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PESTICIDES IN ENVIRONMENTAL COMPARTMENTS OF
AFRAM ARM OF THE VOLTA BASIN IN GHANA
BY
SAMUEL SENYO KORANTENG
(10074438)
THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN
PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF
PHD BOTANY DEGREE
2015
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ACKNOWLEDGEMENTS
The authorship of this work may be credited to me, Samuel S. Koranteng, but I unreservedly
acknowledge the special Grace of Jehovah God that enabled its accomplishment.
I wish to express my sincere gratitude to all those who helped to make the completion of this
Thesis possible. I am particularly grateful to my supervisors, Professor Gabriel K. Ameka and
Professor Ebenezer Oduro-Owusu for their interest, patience, guidance and critical supervision
of this research work. Special thanks to Mr. Emmanuel Akorsah, the Driver who took me round
in all the field trips. He was more than just a driver; his special knowledge of the study area
facilitated selection of appropriate study sites. I do also acknowledge Mr. Emmanuel Klubi of the
Department of Marine and Fisheries Science, University of Ghana for assisting me in the field
work.
I am under special obligation to express my profound gratitude to the Director and Management
of the Ghana Standards Authority for allowing me to use the facilities of the Pesticide Residue
Laboratory to carry out all my analyses. I am very grateful to Mr. Paul Osei-Fosu, Head of the
Pesticide Residue Laboratory for facilitating access to the use of the laboratory. I am particularly
indebted to Mr. Samuel Frimpong, an expert in pesticide residue analyses, who willingly guided
and helped in adapting protocols where necessary to suit various aspects of the extraction
processes. I cannot forget occasions when we spent entire nights in the laboratory working to get
desired results. His assistance is truly invaluable. I also appreciate very much the contribution
and friendliness of other staff mainly; Mr. John Danqwah, Ms. Pearl Mensah and Ms. Ernestina
Adeennze.
This work benefitted from the Faculty Development Grant of University of Ghana, and it is as
such acknowledged.
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Sometimes, the challenges were very daunting and prospects of successful completion appeared
blurred, however, the moral and prayer supports of Rev. Dr. and Mrs Dzameshie (Department of
Linguistics- University of Ghana), Professor Vincent Nartey (Department of Chemistry-
University of Ghana), my wife, Mrs Faustine Koranteng, my children: Jessie, Mark-Jonas and
Jemimah had been a great pillar of encouragement that urged me on. God bless you all.
Finally, to all who have contributed in one way or the other but have not been mentioned, I say:
Thank you very much.
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ABSTRACT
Inappropriate use of agrochemicals, especially insecticides along the banks of the Afram River in Ghana
raises food safety concerns as well as concerns of pollution of the aquatic ecosystem. These
environmental compartments along the Afram arm of the Volta Lake are therefore investigated for
pesticide residues. Levels of three groups of pesticides (organochlorines, synthetic pyrethroids and
organophosphates) were analysed in farmland soils, watermelon, onion and chili pepper as well as some
aquatic biota (fish species, and submerged macrophytes), water and surface sediment. In the case of
aquatic fauna, pesticide content of three tissues: muscle, gill and liver of Tilapia zilli, Oreochromis
niloticus, Chrysichthys nigrodigitatus and Bagrus bayad were determined. Two aquatic macrophytes:
Ceratophyllum demersum and Nymphaea lotus were also analysed and bioconcentration factors for
quantified pesticides evaluated. Presence of banned pesticides were investigated in the analysed matrices,
health risk assessment of pesticide residues in the food commodities for systemic effects conducted,
toxicity of sediment investigated and effect of periodic flooding of cultivated lands on pesticide content of
water assessed. Approximately 97% of target pesticides analysed were detected and quantified in soil
samples of fallow lands; 24% of which exceeded the maximum residue limit (MRL) of the United States
Environmental Protection Agency (USEPA). About 88% of total soil samples analysed contained one or
more pesticide residues. The Farmland soils temporary left to fallow were therefore found from this study
to have high load of residual pesticides. The pesticides that exceeded the USEPA maximum residue limits
were p,p’-DDT, p,p’-DDD, fenvalerate, cypermethrin, permethrin, chlorpyrifos, dimethoate,
chlorfenvinphos and methamidophos; and the banned pesticides detected were: aldrin, dieldrin, endrin,
gamma-lindane, DDT, heptachlor, parathion and methamidophos. Incidence rate of the pesticides in the
food commodities was very high; 100% of target organophosphate and pyrethroids as well as 80% of the
organochlorines were quantified in the food commodities (watermelon, onion and pepper samples)
analysed. While 38% of the quantified pesticide residues exceeded the European Union (EU) MRL,
estimation of health risk associated with pesticide present in the food crops indicate that β-lindane,
dieldrin and methamidophos have potential for systemic toxicity in children while heptachlor shows
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health risk in both children and adults. Also, comparison of pesticides content of water during flood and
recess regimes show significantly high incidence rate and concentration levels of pesticides, as well as
high number of pesticides exceeding the WHO MRL during the flood regime. Determination of Afram
River bed sediment toxicity identifies γ-lindane, p,p’-DDE and dieldrin as contaminants whose
concentration levels affect the integrity of the Afram arm of the Volta Lake ecosystem as a whole and
pose  health risk to benthic organisms in particular. The mean concentration range of pesticides in the four
fish species was highest for organochlorines (0.78 µg/kg – 4671 µg/kg), followed by synthetic pyrethroids
(1.10 µg/kg – 49.8 µg/kg) and then the organophophates (1.60 – 17.00 µg/kg) while total pesticide load in
the fishes follow the order: C. nigroditatus > B. Bayad > O. niloticus > T. zilli. Pesticide content was
significantly higher (p ≤ 0.05) in liver than in gill and muscle tissues.  The concentration order in the
tissues was generally: Liver > Gill > Muscle. Whereas the levels of methoxychlor, aldrin, bifenthrin,
permethrin, cyfluthrin, cypermethrin, chlorpyrifos, chlorfenvinphos, ethoprophos and profenofos in the
muscle tissues of the fishes exceeded 0.01mg/kg default EU MRL, estimation of health risk indicates that
levels of only heptachlor, α-endosulfan and ethoprohos in the fish species present health hazard in
children (up to 11 years), while no health risk can directly be imputed or associated with adult
consumption of these fishes. While Ceratophyllum demersum and Nymphaea lotus have been found to
bioconcentrate pesticides, Ceratophyllum demersum in particular was found to fulfill the “very
bioaccumulative” criterion since it was able to have bioconcentration factor of approximately 5000 for
some pesticides like diazinon and fenitrothion in the aquatic medium. Interaction with the farmers
indicates that most of them are well acquainted with the right application of agrochemicals but fail to do
so. This attitude has resulted in high pesticide residue levels in various environmental matrices along the
Afram River bank of the Volta basin. Most of the farmers, either due to ignorance or deliberate refusal, do
not observe the required Pre-harvest interval (PHI) that has the effect of reducing pesticide residues to
acceptable levels in food crops before consumption. It is therefore necessary to put appropriate policy and
legislative measures in place to ensure compliance to this important requirement that is particularly
relevant in improving food security in fruit and vegetable cultivation.
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TABLE OF CONTENT
Page
Title page i
Declaration ii
Acknowledgement iii
Abstract v
CHAPTER ONE: INTRODUCTION
1.1. Background 1
1.2. Justification 3
1.3. Problem Statement 5
1.4. Objectives of the study 7
1.5. Organisation of the Thesis 7
CHAPTER TWO: LITERATURE REVIEW
2.1. Definition of Pesticides 9
2.2. Classification of Pesticides 12
2.3. Organochlorine, Synthetic Pyrethroid and Organophosphorus Pesticides 14
2.3.1. Organochlorine Pesticides 15
2.3.1.1. Dichlorodiphenyltrichloroethane and Its Metabolites 16
2.3.1.2. Environmental Fates of DDT, DDE and DDD 17
2.3.1.3. Hexachlorocyclohexanes (HCHs) 20
2.3.1.4. Cyclodienes 22
2.3.1.5. Toxaphene 23
2.3.1.6. Health Effects of Organochlorine Pesticides 24
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2.3.2. Pyrethroids 25
2.3.2.1. Environmental Fate of Synthetic Pyrethroids 26
2.3.2.2. Health Effects and Metabolism of Pyrethroids 28
2.3.3. Organophosphates Pesticides (OPs) 29
2.3.3.1. Classes of Organophosphates Pesticides 30
2.3.3.2. Health Impacts of Organophosphorus Pesticides 32
2.3.3.3. Environmental Fates of Organophosphorus Pesticides 34
2.4. Pesticides use in Developing Countries 35
2.5. Review of Pesticide use in Ghana 35
2.5.1. Pesticides in fruits and Vegetables 36
2.5.2. Pesticides in Fish 41
2.5.3. Pesticides in Sediments of Water Bodies of Ghana 43
2.5.4. Pesticides in Ghanaian waters 44
2.6. Government Policy and Regulation on Pesticides 46
2.6.1. Signatory to International Regulations 46
2.6.2. National Legislative Framework for Pesticides Management 48
2.6.2.1. Environmental Protection Act of 1994 (Act 490) 48
2.6.2.2. The Pesticide Control and Management Act, 1996 (Act 528) 49
2.6.2.3. The Food and Drugs Law, 1992 (Act 305B) 49
2.6.3. Control of Imports and Exports 51
2.6.3.1. Export and Import Act, 1995 (Act 503) 51
2.6.3.2. The Customs, Excise and Preventive Service Law, 1993 51
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CHAPTER THREE: STUDY AREA
3.1. Background and Reconnaissance Survey of the Study Area 52
3.2. Ethnicity and Livelihood of People in the Study Area 53
3.3. Geology, Soil, Topography and Drainage of the Study Area 56
3.4. Climate and Vegetation 57
CHAPTER FOUR: PESTICIDE CONTENT OF FALLOW LANDS
4.1. Background 58
4.2. Materials and Method 59
4.2.1. Collection of Soil Samples 59
4.2.2. Chemicals and Reagents 60
4.2.3. Preparation of Soil Samples For Pesticides Extraction 60
4.2.4. Extraction of Pesticides from Soil Samples 61
4.2.4.1. Clean-Up of Extracted Samples 61
4.2.5. Preparation of Stock Pesticides Mix Standards Solution 62
4.2.6. Calibration of Gas Chromatograph 63
4.2.7. Recovery Test of Extracted Method 63
4.2.8. Identification and Quantification of Pesticide Residues 64
4.2.9. Limit of Detection (LOD) and Limit of Quantitation (LOQ) 64
4.2.10. Gas Chromatographic Quantification of Extracted Pesticides 65
4.2.11. Quality Assurance and Control of Method 66
4.2.12. Data Analysis 67
4.3. Results 68
4.3.1. Overview of the Results 68
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4.3.2. Organochlorine Pesticide Residues in Soils 71
4.3.3. Synthetic Pyrethroid Pesticide Residues in Farmland Soils 73
4.3.4. Organophosphorus Pesticide Residues in Farmland Soils 74
4.4. Discussions 76
4.4.1. Organochlorine Pesticide Residues in Soil Samples 76
4.4.2. Degradation Pathways and Evaluation of Input of New Organochlorine
Pesticides 77
4.4.3. Residues of Pyrethroid Pesticides 79
4.4.4. Residues of Organophosphorus Pesticides 81
CHAPTER FIVE: PESTICIDE CONTENT AND HEALTH RISK ASSESSMENT
OF WATERMELON, PEPPER AND ONION FROM THE
CULTIVATED BANKS OF AFRAM ARM OF
THE VOLTA LAKE
5.1. Background 95
5.2. Materials and Method 96
5.2.1. Sampling of Fruit and Vegetable Samples 96
5.2.2. Chemicals and Reagents 96
5.2.3. Processing of Samples for Pesticide Extraction 96
5.2.4. Extraction and Clean-Up of Pesticides from Samples 97
5.2.5. Recovery Test of Extraction Method 98
5.2.6. Gas Chromatographic Quantification of Extracted Pesticides 99
5.2.7. Quality Assurance and Control of Method 100
5.2.8. Determination of Per Capita Consumption in the Study Area. 101
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5.2.9. Data Analysis 102
5.2.9.1 Dietary exposure and Health Risk Assessment 102
5.2.9.2. Treatment of Non-Detect samples 103
5.3. Results 105
5.3.1. Overview 105
5.3.2. Pesticide Residues in Watermelon Samples 105
5.3.3. Pesticide Residues in Chili Pepper Samples 107
5.3.4. Pesticide Residues in Onion Samples 109
5.3.5. Health Risk Analysis 112
5.4. Discussions 116
5.4.1. Organochlorine Pesticide Residues in Fruit and Vegetables 116
5.4.2. Synthetic Pyrethroid Residues in Fruit and Vegetables 118
5.4.3. Organophosphorus Pesticide Residues in Fruit and Vegetables 120
5.4.4. Health Risk Estimate 121
CHAPTER SIX: PESTICIDE CONTENT OF WATER AND SEDIMENT
TOXICITY OF THE AFRAM ARM OF THE VOLTA LAKE
6.1. Background 124
6.2. Materials and Method 126
6.2.1. Sampling of Water and Sediment 126
6.2.2. Chemicals and Reagents 127
6.2.3. Extraction of Samples 127
6.2.3.1. Extraction of Pesticides from Water Samples 127
6.2.3.2. Extraction of Pesticides from Sediment Samples 127
6.2.4. Clean-Up of Pesticide Extracts from Water and Sediment Samples 128
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6.2.5. Recovery Test of Extraction Efficiency 129
6.2.6. Quality Assurance and Control 130
6.2.7. Gas Chromatographic Quantification of Extracted Pesticides 130
6.2.8. Data Analysis 131
6.2.8.1. Water Data Analysis 131
6.2.8.2. Determination of Sediment Toxicity 132
6.3. Results 135
6.3.1. Pesticide Content of Lake Water 135
6.3.2. Pesticide Content and Toxicity of Sediment 137
6.4. Discussion 140
6.4.1. Variation of Pesticide Content of Lake Water under Flood and Recession
Regimes 140
6.4.2. Level of Organochlorines in Sediment 143
6.4.2.1. DDT And Its Metabolites (P,P’-DDE And P,P’-DDD) In Lake
Bed Sediment 143
6.4.2.2. Endosulfan and Its Metabolite Endosulfan Sulfate in Lake Sediment 144
6.4.2.3. Concentration of Lindanes and the Drins (Aldrin, Dieldrin, Endrin)
in Sediment 145
6.4.3. Concentrations of Organophosphorus Pesticides and Synthetic Pyrethroids
in Sediment 146
6.4.4. Lake Sediment Risk and Toxicity Assessment 148
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CHAPTER SEVEN: PESTICIDE DISTRIBUTION IN TISSUES OF FISH SPECIES,
HEALTH RISK ANALYSIS AND BIOCONCENTRATION
OF PESTICIDES IN AQUATIC FLORA
7.1. Background 150
7.2. Materials and Method 152
7.2.1. Collection of Fish and Aquatic Plant Samples 152
7.2.2. Chemicals and Reagents 153
7.2.3. Preparation of Fish Tissue Samples for Pesticide Extraction 153
7.2.4. Extraction and Clean-Up of Extracted Samples 154
7.2.4.1. Extraction and Clean-Up of Pesticides from Fish Samples 154
7.2.4.2. Extraction and Clean-Up of Pesticides from Aquatic Plants 155
7.2.5. Recovery Test of the Extraction Method 155
7.2.6. Quantification of Extracted Pesticides by Gas Chromatograph 156
7.2.7. Quality Assurance of Method 157
7.2.8. Data Analysis 158
7.2.8.1. Health Risk Analysis 158
7.2.8.2. Analysis of Residues in Fish Tissues 159
7.3. Results 160
7.3.1. General Trend of Pesticide Levels in Fish Tissues 160
7.3.2. Organochlorine Pesticide Residues in Fish Tissues 162
7.3.3. Synthetic Pyrethroid Pesticide Residues in Fish Tissues 168
7.3.4. Organophosphorus Pesticide Residues in Fish Tissues 169
7.3.5. Analysis of Residues in Tissue of Fishes 170
7.3.6. Health Risk Analysis 172
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7.3.7. Pesticide Residues and Bioconcentration in Ceratophyllum demersum
and Nymphaea lotus 177
7.4. Discussions 180
7.4.1. Organochlorine Pesticides Concentrations and Composition in Tissues
Of Fishes 180
7.4.2. Synthetic Pyrethroid Concentrations and Composition in Tissues of Fishes 184
7.4.3. Organphosphorus Pesticides Concentrations and Composition in Tissues
of Fishes 185
7.4.4. Tissue-Specific Bioaccumulation of Pesticides in Fish Species 187
7.4.5. Health Risk Estimates 188
7.4.6. Bioconcentration of Pesticides in Aquatic Flora 190
CHAPTER EIGHT: GENERAL CONCLUSION, SUMMARY AND
RECOMMENDATIONS
8.1 General conclusion 192
8.2. Summary 194
8.3. Recommendations 198
REFERENCES 200
APPENDICES 226
Appendix I: Chemicals and Reagents 226
Appendix II: Concentration of Pesticides in Water under Flood Regime 227
Appendix III: Concentration of Pesticides in Water under Recess Regime 228
Appendix IV: One-way  Anova to Compare Pesticides Concentrations in Muscle,
Gill and Liver Tissues of Tilapia zilli 229
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Appendix V: One-way  ANOVA to compare Pesticides Concentrations in Muscle,
Gill and Liver Tissues of Oreochromis niloticus 230
Appendix VI: One-way  ANOVA to compare pesticides concentrations in muscle,
Gill and Liver Tissues of Chrysichthys nigrodigitatus 231
Appendix VII: One-way  ANOVA to compare Pesticides Concentrations in Muscle,
Gill and Liver Tissues of Bagrus bayad 232
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LIST OF TABLES
Page
Table 4.1: Mean Concentrations of Organochlorine Pesticides in Soil Samples
from Farmlands 72
Table 4.2: Ratios of Metabolites to Parent Compounds in Soils from Farmlands 72
Table 4.3: Mean Concentrations of Synthetic Pyrethroid Pesticides in Soil Samples
from Farmlands 73
Table 4.4: Mean Concentrations of Organophosphorus Pesticides in Soil Samples
from Farmlands 74
Table 4.5: Inventory of some Insecticides Used in the Study Area 75
Table 5.1: Pesticide Concentrations in Watermelons 106
Table 5.2: Pesticide Concentrations in Chili Pepper 108
Table 5.3: Pesticide Concentrations in Onions 111
Table 5.4: Daily Consumption of Food Items in the Study Area Compared to
National Per Capita Consumption for Ghana 112
Table 5.5: Health Risk Estimates for Systemic Effects associated with Pesticide
Residues in Watermelon 113
Table 5.6: Health Risk Estimates for Systemic Effects associated with Pesticide
Residues in Chili Pepper 114
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Table 5.7: Health Risk Estimates for Systemic Effects associated with Pesticide
Residues in Onion 115
Table 6.1: Comparison of Pesticide Water Quality during occasional Flooding of
Farmlands and Period of Recession 136
Table 6.2: Concentration of Pesticide Residues in Sediment 138
Table 6.3: Estimated Risk Quotients of Organochlorine Pesticides Concentrations in
Sediments (Ocps) Based on Canadian Sediment Quality Guideline (CSQG)
and National Oceanic and Atmospheric Administration (NOAA) Guidelines 139
Table 7.1: Comparison of Mean Concentration (µg/Kg) of Total Detected Pesticides
in Tissues of four Fish Species 160
Table 7.2: Mean Concentration (µg/Kg) and Distribution of Pesticides in Body Tissues
of Tilapia zilli 164
Table 7.3: Mean Concentration (µg/Kg) and Distribution of Pesticides in Body
Tissues of Oreochromis niloticus 165
Table 7.4: Mean Concentration (µg/Kg) and distribution of Pesticides in Body
Tissues of Chrysichthys nigrodigitatus 166
Table 7.5: Mean Concentration (µg/Kg) And Distribution of Pesticides in Body
Tissues of Bagrus Bayad 167
Table 7.6: Mean Concentration of selected Pesticide Residues in different Tissues
of Tilapia Zilli 170
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Table 7.7: Mean Concentration of selected Pesticide Residues in different Tissues
of Oreochromis niloticus 171
Table 7.8: Mean Concentration of selected Pesticide Residues in Different Tissues
of Chrysichthys nigrodigitatus 171
Table 7.9: Mean Concentration of selected Pesticide Residues in different Tissues
of Bagrus bayad 171
Table 7.10: Health Hazard Indices of Pesticides in Tilapia zilli 173
Table 7.11: Health Hazard Indices of Pesticides in Oreochromis niloticus 174
Table 7.12: Health Hazard Indices of Pesticides in Chrysichthys nigrodigitatus 175
Table 7.13: Health Hazard Indices of Pesticides in Bagrus bayad 176
Table 7.14: Pesticides in Ceratophyllum demersum and Bioconcentration Factor 178
Table 7.15: Pesticides in Nymphaea lotus and Bioconcentration Factor 179
Table 7.16: Concentrations of Pesticides in Fish Tissues from Local and International
Studies Compared to the Present Study 183
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LIST OF FIGURES
Page
Figure 2.1: Isomers of Dichlorodiphenyltrichloroethane (DDT) 17
Figure 2.2: Structure of some DDT Metabolites 19
Figure 2.3: Lindane Structure 20
Figure 2.4: Chemical Structures of some common Cyclodienes 22
Figure 2.5: Generalized Structure of Toxaphene 24
Figure 2.6: Chemical Structures of some Pyrethroids 27
Figure 2.7: General Structure of Organophosphates Insecticides 30
Figure 2.8: Chemical Structure of Some Common Organophosphate Pesticides 32
Figure 3.1: Map of Study Area Showing Sampling Sites 55
Figure 4.1: Percentage Total Concentration of individual Chemicals in each
group of Pesticide 69
Figure 4.2: Top Ten Chemicals with Highest Mean Concentration (µg/Kg) in Soils
from the Study Area 70
Figure 7.1: Total Number of detected Pesticides in various Tissues of four
Fish Species 161
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LIST OF PLATES
Page
Plate 1: Fallow Lands 84
Plate 2: Crop Samples 85
Plate 3: Samples of Aquatic Biota 86
Plate 4: Drawdown Farming 87
Plate 5: Large scale Farms Upland the Drawdown Areas 88
Plate 6: Tissue Samples of Some Fishes 89
Plate 7: Some stages in the extraction of soil and fish matrices 90
Plate 8: Some Stages in the food crop Extraction Process 91
Plate 9: Gas Chromatography Varian CP-3800 Used For Pesticide Residue
Quantification 92
Plate 10: Decon Sonicator and Centrifuge 93
Plate 11: Buchi Rotary Vacuum Evaporator used in the Analyses 94
.
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CHAPTER ONE
INTRODUCTION
1.1 Bacground
The US Environmental Protection Agency defines a pesticide as “any substance or mixture of
substances intended for preventing, destroying, repelling or mitigating any pest” (USEPA, 2006).
Pesticides are therefore formulated primarily to control pests and are deliberately introduced into
the environment containing the target pests. Due to uncontrolled use of pesticides in some
instances, coupled with occasional lack of specificity, the effect of pesticides invariably tend to
go beyond their targets, to impacting unintended compartments of the environments with dire
consequences on occasions (Carson, 2002). The study of pesticides and their effects has
therefore been a thematic research area of much interest.
Historically, pesticides have been in use for about 4500 years (Unsworth, 2010). The first
recorded use was of simple sulphur compounds to control insects and mites by the Sumerians
(Unsworth, 2010). Since its first use, pesticides of various kinds have been manufactured for
various purposes. The first groups of pesticides of major revolutionary importance to be
discovered was the synthetic organic pesticides or the organochlorines in the 1940s, such as
Parathion, dichlorodiphenyltrichloroethane (DDT), benzenehexachloride (BHC), aldrin, dieldrin
and chlordane (History of pesticide, n.d.). This group of pesticides instantly became very popular
because of their broad-spectrum activity and also because they were effective yet inexpensive
(The History of Pesticides, 2008). The most popular of them, DDT, discovered in 1949 by a
Swiss Scientist, Dr. Paul Muller was widely used due to its perceived low mammalian toxicity,
to treat insect-borne diseases like malaria, yellow fever and typhus (Delaplane, 2000). From the
1950s through the 60s pesticide use became mostly associated with agricultural activities. There
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was over-reliance on the newly found organic pesticides (like DDT, BHC, dieldrin, endrin,
chlordane etc) for increase yield of crops (Ganzel, 2007).
Over time, the potential of the organochlorine pesticides for bioaccumulation and long-term
toxicity became widely recognized and pest persistence became increasingly evident. Over
reliance on the chlorinated hydrocarbons soon led to their indiscriminate use (Carson, 2002) and
this resulted in various health and environmental problems. Of particular concern to the
international community are the persistent organic pollutants (POPs,) also referred to as the
‘dirty dozen’ comprising: aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex, dioxins,
hexachlorobenzene, furans, toxaphene and polychlorinated biphenyls (PCBs). They are known to
cause an array of adverse effects including diseases and birth defects among humans and
animals. The United Nations (UN), through the Stockholm Convention therefore banned the use
of the POPs in 2004 (EPA Ghana, 2007). The chlorinated pesticides subsequently fell out of use
in preference to the more environmentally friendly ones like orgarnophosphates, carbamates and
pyrethroids, which although more acutely toxic, do not persist in the environment.
Discovery of pesticides has brought many benefits to mankind. The most obvious are the
economic benefits derived from the protection of commodity yield and quality, and the reduction
of other costly inputs such as labour (Thorpe, 1988). Other kinds of benefits include the
maintenance of aesthetic quality, the protection of human health from disease-carrying
organisms, the suppression of nuisance-causing pests, and the protection of other organisms,
including endangered species from pests (Thorpe, 1988).
Despite their many advantages, there are some potential hazards or risks associated with the use
of pesticides. Adverse impacts of pesticides use usually stem from a lack of understanding of the
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impact of the chemical on the environment and indiscriminate use/overuse of the product.
Uncontrolled use can result in the reduction of the population of non-target organisms, including
beneficial species. Drift sprays and vapour during application can cause severe damage and
residue problems in food resources and present health risks (Pros & cons of pesticide use (n.d.)).
Poisoning hazards and other health effects can occur through excessive exposure if safe handling
procedures are not followed. There is also the risk of contamination of soil and groundwater as
well as development of crop pest populations that are resistant to agrochemical treatment (Pros &
cons of pesticide use (n.d.).
1.2 Justification
Ghana is essentially an agricultural country with the sector contributing 31.8%, 29.8%, 25.3%,
22.7% and 21.3% to the nation’s Gross Domestic Product (GDP) in 2009, 2010, 2011, 2012 and
2013, respectively (Ghana Statistical Service, 2013). Like all agrarian economies, there is
dependence on agro-chemicals for increased yield in every sector of the agricultural enterprise
and this has led to an increase in demand for agro-chemicals.
Importation of pesticides into Ghana dates back to the late 1940s when
dichlorodiphenyltrichloroethane (DDT), lindane and related pesticides were extensively used for
both agricultural and public health purposes (EPA Ghana, 2007).
Dichlorodiphenyltrichloroethane was officially used for the control of cocoa capsids as well as
malaria and filariasis. However, following the recognition of its adverse effects, the use and
importation of DDT, alongside 26 others, was banned in 1985 (EPA Ghana, 2007). As DDT and
some organochlorines were phased-out, new and safer alternatives, mainly organophosphates,
carbamates and synthetic pyrethroids were introduced. Currently about a total of 380 pesticides
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of different categories have been registered or approved for use in Ghana (EPA Ghana, 2013)
and accessibility has been facilitated by the rapid and widespread proliferation of agro-chemical
retail shops in the country. Dinhan, (2003) reported that about 87% of farmers in Ghana depend
on pesticide for increase yield. One particular area that has witnessed intensive use of pesticides
is fruit and vegetable farming. This horticultural industry tends to concentrate around water
bodies where irrigation occurs all year round. Given the fact that fruits and vegetables are
naturally infested by myriads of pests, farmers tend to depend heavily on pesticides for improved
yield and aesthetic value of their products for maximum economic benefits. Horna et al., (2008)
reported that about 90% of vegetable farmers in Ghana apply doses above the recommended
rates in single applications. The residue of the pesticides accumulate in the crops, the soil
medium, water bodies, sediments and aquatic biota; resulting in the contamination of the food
chain and the attendant health hazards.
Presence of pesticides in the following matrices: fish, (Darko, Akoto & Oppong, 2008; Afful,
Anim & Serfor-Armah, 2010), water (Ntow, 2001 & 2005), sediment (Ntow, 2001; Darko,
Akoto & Oppong, 2008), vegetables (Amoah et al., 2006; Ntow, 2008; Darko, 2009; Bempah et
al., 2011, 2012) and meat (Darko & Acquaah, 2007), from Ghana have been reported. Evidence
of the presence of pesticides in human body is already documented in Ghana (EPA Ghana, 2007;
Ntow, 2008; 2001; Osei-Tutu et al., 2011). This occurrence should be of much concern and
special attention and concerted effort needs to be directed into investigation of pesticide residue
in our environment. There is the need to investigate residues of pesticides in various
environmental matrices to provide clues about pathways along which pesticides bioaccumulation
occur. Moreover, there is the need to investigate health hazards associated with environmental
residue levels. Such data will provide important information needed by the Environmental
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Protection Authority (EPA), Food and Drugs Authority (FDA) and Ghana Standards Authority
(GSA) for their monitoring and regulatory activities and will as well facilitate assessment of
existing policies for the development of alternative pesticide management programmes.
1.3 Problem Statement
According to Gordon and Amatekpor (1999), the Volta River in Ghana was impounded in 1964
following the creation of a dam a year earlier at Akosombo for the main purpose of hydro
electricity generation. The impoundment created a lake with a surface area of about 8500 km2
(3.6% of surface area of Ghana) and a shoreline exceeding 4800 km. It also resulted in reduction
in the flow regime and inundation of farm lands and communities in the upper stretches of the
Volta River. Since the creation of the Lake some 50 years ago, there have been intensive
agricultural activities along its banks that heavily rely on agrochemicals. There is seasonal
recession of water from the lake, especially during the drier periods. As water recedes, farmers
follow along and cultivate the exposed land, taking full advantage of the residual moisture in the
soil hence reducing the burden of irrigation. Communities along the Afram arm of the Volta
Lake in particular, apart from fishing, also resort to farming along the immediate banks, taking
advantage of the residual moisture in the soil when the lake recedes between the months of
November and May (Gordon & Amatekpor, 1999). This type of farming is referred to as
‘drawdown farming’. Later, when the moisture of the soil falls below the optimum level, manual
or can irrigation is employed. Noticing the economic benefits from ‘draw-down’ farming,
mechanised irrigation equipment has been procured to enable cultivation of large areas upland
and further away from the drawdown region. Plates 5a -5c provide some insight into the
irrigational facilities that make large scale farming upland of drawdown areas possible.
Communities along entire Afram arm of the Volta Lake are now noted for the production of
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crops such as tomatoes, okra, pepper, garden eggs, cabbage, lettuce, peas, water melon, sweet
potatoes and other short-maturing crops along the banks of the Afram arm of the Volta Lake
(Gordon & Amatekpor, 1999).
The most common horticultural crops produced along the bank of the Afram arm of the Volta
Lake are the Allium cepa L. (red onions), Capsicum annuum L. (chilli pepper), Citrullus vulgaris
Schrad. (Watermelon) and Abelmoschus esculentus L. (okra) which have ready market. They are
transported to the nearest centres of commercial activities (in this case, Nkawkaw, Kumasi and
Accra) for onward retailing to the various parts of the country.
Now, with the introduction of mechanized irrigation, farming goes on all-year round and farmers
rely heavily on the use of agrochemicals, including pesticides for increased yield of crops.
Reconnaissance visit to the field revealed that the synthetic pyrethroid, organophosphates,
fungicides and herbicides are the most commonly used pesticides. Documented evidence of
misuse of pesticides and other agrochemicals by the farmers in other vegetable growing areas in
Ghana (Ntow, Gijzen, Kelderman & Drechsel, 2006; Ntow et al., 2007; Ntow, 2008; Botwe et
al., 2011) is enough ground to give cause for similar concerns in the Afram area. The important
phenomenon of seasonal flooding of the cultivated areas along the Afram bank increases the
probability of the presence of pesticides in water body. Given the dynamics normally involved in
pesticide contamination, the farmland soil, the farm produce, the adjoining water body, sediment,
and the aquatic flora and fauna, as well as the farmers themselves are invariably exposed to
pesticide contamination. Hence these environmental compartments of the Afram arm of the
Volta Lake need to be investigated to assess the level of pesticide pollution.
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1.4 Objectives of the study
This study seeks to investigate the residual levels of three pesticides groups (organochlorines,
synthetic pyrethroids and organophosphates) in farmland soils as well as in fruits and vegetables
cultivated along the Afram arm of the Volta Lake. It is anticipated that the Afram arm of the
Volta Lake will inevitably receive run-offs from the agricultural fields and hence water, river
sediments and some aquatic biota will as well be analysed for pesticide contamination and any
possibly associated health hazards.
The specific objectives of this study are to:
 Verify if banned pesticides are still in agricultural use along the bank of the Afram River.
 Investigate pesticide content of fallow farmlands prior to re-cultivation
 Determine pesticide content of Afram water and toxicity in surface sediments
 Ascertain pesticide levels in food crops and fish and the health hazard associated with
their consumption.
 Estimate bioconcentration of pesticides by submerged aquatic flora
1.5 Organisation of the Thesis
This study focuses on the analyses of wide range of insecticides from the organochlorine,
organophosphate and synthetic pyrethroids groups and their levels in different environmental
matrices mainly: soil, water, sediment, fruit and vegetables as well as aquatic biota along the
Afram arm of the Volta Lake. The research employed random field   sampling. The
concentration of pesticides in the samples were evaluated by laboratory measurements using
state-of-the-art equipment, mainly gas chromatography equipped with electron capture detector
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(ECD) and pulse flame photometric detector (PFPD). Results were analysed and health
risk/hazards assessment through dietary exposure determined.
The Thesis starts with an introduction as chapter one and presents background to the entire work.
The research outline is presented here and the aim, objectives and strategy defined. Chapter two
presents detailed literature review pertaining to the research. Here, current state of work relating
to the various aspects of this research, in the country is extensively reviewed. The location and
features of the study area are spelt out in Chapter three, and Chapters four to seven present the
main body of the research.
In Chapter four, the research presents how soil from agricultural lands on the bank of the Afram
River was sampled and analysed for pesticide residues. Chapter five describes the determination
of pesticide residues in selected fruit and vegetables from the cultivated fields and the health risk
associated with their consumption. Chapter six examines toxicity of surface sediment of the lake
and compares pesticide quality of lake water under flood and recess regimes, whilst chapter
seven investigates distribution of pesticides in tissues of four selected species of fish in the
Afram River. This chapter as well assesses the health risk associated with the consumption of
targeted fishery species. Pesticide accumulations in two aquatic plants are also determined in
chapter seven and the results used to estimate bioconcentration factors (BCF) for each of the
plants. Finally, the Thesis ends with chapter eight presenting the general conclusion, summary
and recommendations for future research as well as policy directions for the Ghana
Environmental Protection Authority (EPA), Ghana Standards Authority (GSA) and Ghana Food
and Drugs Authority (FDA) who are the main stakeholders.
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CHAPTER TWO
LITERATURE REVIEW
2.1 Definition of Pesticides
Pesticides of one type or another have been in use for thousands of years. A major motivation for
using pesticides is to control diseases. Human deaths due to insect-borne diseases through the
ages far exceed those attributable to the effect of warfare (Baird & Cann, 2012). The use of
various insecticides has greatly reduced the incidence of diseases transmitted by insects and
rodents. Malaria, yellow fever, bubonic plagues and sleeping sickness are but few examples of
these diseases. Another principal motivation for insecticide use is to prevent insects from
attacking food crops. Even with extensive use of pesticides, about one-third of the world’s total
crop yield is destroyed by pests during growth, harvesting and storage (Baird & Cann, 2012).
Pesticides as substances that directly kill or control unwanted organisms have been defined by
various authours, interest groups and organizations. The United States Environmental Protection
Agency (USEPA) defines a pesticide as “any substance or mixture of substances intended for
preventing, destroying, repelling or mitigating any pest” (USEPA, 2006). Washington State
Department of Agriculture (2009) defines pesticides as: “Any substance or mixture of
substances, including plant regulators, defoliants, desiccants and spray adjuvant, intended to
prevent, destroy, control, repel, or mitigate any insect, rodent, snail, slug, fungus, weed, and any
other form of plant or animal or virus, except viruses on or in a living person or other animal”.
The European Union prefers a definition for pesticides that covers insecticides, acaricides,
herbicides, fungicides, plant growth regulators, rodenticides, biocides and veterinary medicines.
It defines pesticides as chemical compounds used to: “Kill, repel or control pests to protect crops
before and after harvest; Influence the life processes of plants; destroy weeds or prevent their
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growth; and Preserve plant products”. The Food and Agriculture Organization (FAO, 2002)
provides an elaborate and extensive definition of pesticide as: “any substance or mixture of
substances intended for preventing, destroying, or controlling any pest, including vectors of
human or animal disease, unwanted species of plants or animals, causing harm during or
otherwise interfering with the production, processing, storage, transport, or marketing of food,
agricultural commodities, wood and wood products or animal feedstuffs, or substances that may
be administered to animals for the control of insects, arachnids, or other pests in or on their
bodies. The term includes substances intended for use as a plant growth regulator, defoliant,
desiccant, or agent for thinning fruit or preventing the premature fall of fruit. Also used as
substances applied to crops either before or after harvest to protect the commodity from
deterioration during storage and transport”
The ‘US Legal’, a legal service industry that offers support and resources such as a legal
dictionary, law guides and legal references defines pesticides as: “Any substance or mixture of
substances intended for preventing, destroying, repelling, attracting or mitigating any insects,
rodents, nematodes, fungi, weeds or other forms of plant or animal life and/or bacteria and
viruses, except bacteria or viruses on or in living man or other animals, which is determined to
be a pest”. It may also mean any substance or mixture of substances intended for use as a plant
regulator, defoliant or desiccant” (USLegal, 2014). Pests can be insects, mice and other animals,
unwanted plants (weeds), fungi, or microorganisms like bacteria and viruses. The U.S. definition
of pesticides generally is quite broad and often misunderstood to refer only to insecticides,
though the term pesticide also applies to herbicides, fungicides, and various other substances
used to control pests as well as any substance or mixture of substances intended for use as a plant
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regulator, defoliant, or desiccant (USEPA, 2006). Even though the U.S. definition of pesticides is
quite broad, it does have some exclusions such as: drugs used to control diseases of humans or
animals; fertilizers, nutrients, and other substances used to promote plant survival and health (are
not considered plant growth regulators and thus are not pesticides); biological control agents,
except for certain microorganisms, are exempted from regulation by EPA (Biological control
agents include beneficial predators such as birds or ladybugs that eat insect pests) and products
which contain certain low-risk ingredients, such as garlic and mint oil, have been exempted from
the US Federal registration requirements, although State regulatory requirements may still apply
(USEPA, 2014). Generally, the USEPA definition has been adopted in Ghana by stakeholder
institutions like the EPA, Ghana; Ghana Standard Authority and Ghana Food and Drugs
Authority.
Scrutiny of above definitions and others from literature identifies common elements in
definitions. According to Young (1987), any accepted definition of pesticides should include key
phrases such as “chemical substance or mixture of substances intended for preventing,
destroying, repelling or mitigating any pest” and “substances intended for use as a plant
regulator, defoliant or desiccant”. In the light of the above review of pesticides definitions, the
one provided by Eldridge, (2008) is quite succinct and aptly summarises the various definitions
and therefore adopted for this study. According to him, “Pesticides are defined as substances or
mixtures of substances intended for controlling, preventing, destroying, repelling, or attracting
any biological organism deemed to be a pest”.
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2.2 Classification of Pesticides
The term pesticide encompasses a diverse collection of substances. Appropriate classification of
pesticides groups is therefore desirable for easy reference. Different authors adopt different
approaches. Irrespective of the approaches however, pesticides are grouped or classified
according to the pests they control, their chemical structure, how/when they work, or their mode
of action (site of action) (British Colombia Ministry of Agriculture, n.d.).
The most popular way of classifying pesticides is according to the target pests they kill; for
example, insecticides are pesticides that target insects, herbicides target plants, acaricides target
ticks, nematocides target nematodes, etc. Pesticides are also grouped according to their chemical
structure. Pesticides with similar chemical structures have similar characteristics and usually
have a similar mode of action. Most pesticide active ingredients are either inorganic or organic
pesticides. Inorganic pesticides do not contain carbon and are usually derived from mineral ores
extracted from the earth. Examples of inorganic pesticides include copper sulphate, ferrous
sulphater and sulphur. Organic pesticides on the other hand contain carbon in their chemical
structure. Most organic compounds are created from various compounds, but a few are extracted
from plant material and are called 'botanicals'. The most well known organic group of pesticides
include: organochlorines, organophosphates, synthetic pyrethroids and carbamates. (USEPA,
2006)
Pesticides can also be classified according to how or when they work. On this basis, the
following, among others have been identified by the USEPA: Contact pesticides, systemic
pesticides, foliar pesticides, selective pesticides, non-selective pesticides, residual and non-
residual pesticides.
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Contact pesticides generally control a pest as a result of direct contact. Insects are killed when
sprayed directly or when they crawl across surfaces treated with a residual contact insecticide.
Weed foliage is killed when enough surface area is covered with a contact herbicide. Systemic
pesticides are pesticides which are absorbed by plants or animals and move to untreated tissues.
Systemic or translocated herbicides move within the plant to untreated areas of leaves, stems or
roots. They may kill weeds with only partial spray coverage. Systemic insecticides or fungicides
move throughout treated plants and kill target pests. Foliar pesticides are applied to plant leaves,
stems and branches; they may be either a contact pesticide or a systemic pesticide. Selective
pesticides control only certain pests, while non-selective pesticides will control a wide range of
pests. Residual pesticides do not break down quickly and may control pests for a long time (i.e.
several weeks or a year). Non-residual pesticides are quickly made inactive after application
and do not affect future crops.
Biopesticides are another group of pesticides. They are derived from natural materials such as
animals, plants, bacteria, and certain minerals. Biopesticides fall into three major classes:
Microbial pesticides, Plant-Incorporated-Protectants (PIPs) and Biochemical pesticides.
Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan)
as the active ingredient. Microbial pesticides can control many different kinds of pests, although
each separate active ingredient is relatively specific for its target pests. The most widely used
microbial pesticides are subspecies and strains of Bacillus thuringiensis (Bt). Each strain of this
bacterium produces a different mix of proteins, and specifically kills one or a few related species
of insect larvae. While some Bt's control moth larvae found on plants, other strains are specific
for larvae of flies and mosquitoes. The target insect species are determined by whether the
particular Bacillus thuringiensis produces a protein that can bind to a larval gut receptor, thereby
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causing the insect larvae to starve (USEPA, 2014). Plant-Incorporated-Protectants (PIPs) are
pesticidal substances that plants produce from genetic material that has been added to the plant.
For example, the gene for the Bacillus thuringiensis pesticidal protein can be taken and
introduced into the plant's own genetic material. Then the plant, instead of the Bt bacterium,
manufactures the substance that destroys the pest. Biochemical pesticides are naturally
occurring substances that control pests by non-toxic mechanisms. Conventional pesticides, by
contrast, are generally synthetic materials that directly kill or inactivate the pest. Biochemical
pesticides include substances, such as insect sex pheromones that interfere with mating as well as
various scented plant extracts that attract insect pests to traps. Because it is sometimes difficult to
determine whether a substance meets the criteria for classification as a biochemical pesticide,
USEPA has established a special committee to make such decisions (USEPA, 2014). Pesticides
can also be grouped according to their mode of action or the way a pesticide destroys or
controls the target pest. The pesticide may have a specific site of action, commonly referred to as
primary action site. In some instances, one insecticide may affect insects’ nerves while another
may affect moulting. One herbicide may mimic the plants growth regulators and another may
affect the plants ability to convert light into food. One fungicide may affect cell division and
another may slow the creation of important compounds in the fungus British Colombia Ministry
of Agriculture, n.d.).
2.3 Organochlorine, synthetic pyrethroid and organophosphorus pesticides
The principal pesticides considered in the study area are organochlorines, organophosphates and
synthetic pyrethroids insecticides.  Therefore only these pesticides will be included in the review
in this chapter.
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2.3.1 Organochlorine Pesticides (OCPs)
Organochlorine pesticides are insecticides composed primarily of carbon, hydrogen and chlorine.
There are four chemically distinct sub-groups of organochlorines –
Dichlorodiphenyltrichloroethane (DDT) and its analogues, hexachlorocyclohexanes (HCH),
cyclodiene compounds and toxaphene group (Ware, 2000). While each of these sub-groups
varies in chemical structure, their properties are mostly typical of all organochlorine pesticides.
The organochlorine compounds possess unique physical and chemical properties that influence
their persistence, fate, and transport in the environment. Although these properties differ among
the organochlorine compounds, they all exhibit an ability to resist degradation, associated with
sediments or other solids, and to accumulate in the tissue of invertebrates, fish, and mammals.
Their unique properties have contributed to both their efficacy as pesticides and industrial
products and their persistence and accumulation in the environment (Organochlorine
compounds, n.d). The carbon-chlorine bond of organochlorines is very stable to hydrolysis and
the stability increases with greater number of chlorine substitutions. OCPs are typically ring
structures with a chain or a branched chain framework. Chlorine attached to an aromatic ring is
more stable to hydrolysis than chlorine in aliphatic structures. Due to their high degree of
halogenation, they have very low water solubility and high lipid solubility, hence their ability to
easily pass through the phospholipid structure of biological membranes and accumulate in fat
deposits (Baird & Cann, 2012). Organochlorine pesticides share several notable properties such
as: high stability against decomposition or degradation in the environment; very low solubility in
water; high lipid solubility; low volatility and relatively high toxicity to insects but low toxicity
to humans (Baird & Cann, 1999). Their ability to persist, bioconcentrate, biomagnify and the
associated health hazards have made them highly undesirable in the environment.
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As insect pests, all organochlorines act by stimulating the nervous system, interrupting the
transmission of nerve impulses and signals (Waugh, & Padovan, 2004). In response to their
adverse effects seen in wildlife and humans, the production and use of these compounds were
banned in industrialised countries during the 1970s or subjected to restrictions in use in many
others. However, they continue to be detected in both biological and environmental samples
worldwide because of their persistent and bioaccumulative properties (Ntow et al., 2007)
2.3.1.1 Dichlorodiphenyltrichloroethane and its metabolites
Dichlorodiphenyltrichloroethane (DDT) was developed by the German chemist, Othmar Zeidler
in 1874, but its insecticidal properties were discovered by the Swiss chemist Paul Hermann
Muller in 1939. It was used during the Second World War for control of lice and mosquitoes to
combat typhus and malaria, respectively (Snedeker, 2001). The World Health Organization has
estimated that malaria reduction programs by the use of DDT, have saved the lives of more than
5 million people (Baird & Cann, 2012). Its insecticidal properties were discovered in 1939 by the
Swiss chemist Hermann Muller (Chau & Afghan, 1982) and it was hailed as the "miracle
insecticide" (Baskin, 2001) and quickly became one of the most widely used pesticides in the
world to control insects on agricultural crops. As a result of its potential for human toxicity and
severe ecological effects, DDT was banned in Hungary in 1968, Norway and Sweden in 1970,
the United States in 1972  and in the United Kingdom in 1984 (US EPA, 1990). It was
subsequently banned for agricultural use worldwide in 2004 under the Stockholm Convention,
though it is still being used in some underdeveloped countries for disease vector control.
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p,p'-dichlorodiphenyltrichloroethane o,p'-dichlorodiphenyltrichloroethane
Fig. 2.1: Isomers of dichlorodiphenyltrichloroethane (ATSDR, 2002)
In the environment and in the body, dichlorodiphenyltrichloroethane (DDT) breaks down over
time into dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD)
(Figure 2.2). Dichlorodiphenyldichloroethylene and dichlorodiphenyldichloroethane are therefore
the major metabolites of DDT. Technical-grade DDT however, is a mixture of some related
compounds. The components include the p,p'-DDT isomer (85%), o,p'-DDT (15%) (Fig. 2.1),
and o,o’-DDT (trace amounts). Dichlorodiphenyldichloroethylene (DDE) and
dichlorodiphenyldichloroethane (DDD) also occur as contaminants (Faroon et al., 2002). The
total DDT in a sample refers to the sum of all DDT congeners (p,p'-DDT, p,p'-DDE, p,p'-DDD,
o,p'-DDT, o,p'-DDE and o,p'-DDD). Dichlorodiphenyldichloroethane was also manufactured
and used as an insecticide, but to a much lesser extent than DDT.
Dichlorodiphenyldichloroethylene has no commercial use, but is commonly detected along with
DDT at concentrations in the environment that often exceed those measured for DDT.
2.3.1.2 Environmental fates of DDT, DDE and DDD
Most DDT in the environment is as a result of past use (ATSDR, 2002). It also entered the
various compartments of the environment as gas during the production process. DDT still enters
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the environment because of its current use in other areas of the world. DDE is only found in the
environment as a result of contamination or breakdown of DDT.
Dichlorodiphenyldichloroethane was also used as a pesticide to a limited extent in the past. It
also enters the environment as a breakdown product of DDT (ATSDR, 2002).  Large amounts of
DDT were released into the air and on soil or water when it was sprayed on crops and forests to
control insects. DDT was also sprayed in the environment to control mosquitoes. DDT, DDE and
DDD may also enter the air when they evaporate from contaminated water and soil. DDT, DDE,
and DDD in the air will then be deposited on land or surface water. This cycle of evaporation
and deposition may be repeated many times. As a result, DDT, DDE, and DDD can be carried
long distances in the atmosphere. According to Faroon et al., (2002), these chemicals have been
found in regions, far from where they were ever used and some DDT, DDE, and DDD may occur
in the atmosphere as a vapor or be attached to solids in air. Vapor phase DDT, DDE, and DDD
may break down in the atmosphere due to reactions caused by the sun. The half-life of these
chemicals in the atmosphere as vapors has been calculated to be approximately 1.5 – 3 days
(ATSDR, 2002). However, in reality, this half-life estimate is too short to account for the ability
of DDT, DDE, and DDD to be carried long distances in the atmosphere. DDT, DDE, and DDD
remain in the soil for a very long time, potentially for hundreds of years. Their half-life in soil
can vary between 2 and 15 years, depending on the soil acidity and temperature (ATSDR, 2002),
350 days in surface waters and 31 years in ground water (Howard, 1991). Most DDT breaks
down slowly into DDE and DDD, generally by the action of microorganisms. Figure 2.2 shows
the structure of some DDT metabolites.
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P,p'-Dichlorodiphenyldichloroethylene (p,p'-DDE) p,p'-Dichlorodiphenyldichloroethane (p,p'-DDD)
Fig. 2.2: Structure of DDT metabolites- p,p'-DDE and p,p'-DDD (ATSDR, 2002)
These chemicals may also evaporate into the air and be deposited in other places. They stick
strongly to soil, and therefore generally remain in the surface layers of soil. Some soil particles
with attached DDT, DDE, or DDD may get into rivers and lakes in runoff. Only a very small
amount, if any, will seep into the ground and get into groundwater. The length of time that DDT
will last in soil depends on many factors including temperature, type of soil, and whether the soil
is wet. DDT lasts for a much shorter time in the tropics where the chemical evaporates faster and
where microorganisms degrade it faster. DDT disappears faster when the soil is flooded or wet
than when it is dry. Its disappearance is also faster initially when it enters the soil. Later on,
evaporation slows down and some DDT moves into spaces in the soil that are so small that
microorganisms cannot reach it to break it down efficiently. In tropical areas, total DDT may
disappear in much less than a year. In temperate areas, half of the total DDT initially present
usually disappears in about 5 years. However, in some cases, half of the total DDT initially
present will remain for 20, 30, or more years (ATSDR, 2002). In surface water, DDT will bind to
particles in the water, settle, and be deposited in the sediment. DDT is taken up by small
organisms and fish in the water. It accumulates to high levels in fish and marine mammals (such
as seals and whales), reaching levels many thousands of times higher than in water. In these
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animals, the highest levels of DDT are found in their adipose tissue. DDT in soil can also be
absorbed by some plants and by the animals or people who fed on those plants.
2.3.1.3  Hexachlorocyclohexanes (HCHs)
Hexachlorocyclohexane (HCH), formally known as benzene hexachloride (BHC), is a synthetic
chemical derived from cyclohexane having one of two halogens on each carbon substituted by
chlorine. It was discovered during the Second World War and found to be an effective
insecticide against a wide variety of insects (Baird & Cann, 1999).
Fig. 2.3:   Lindane structure (ATSDR, 2005)
It exists in eight isomeric forms and the isomers differ only in relative orientations of the
chlorine atoms bonded to different carbons. Alpha- HCH, β- HCH, γ- HCH, and δ- HCH are the
common isomers found in use in developing countries (ATSDR, 2005). Only one of the isomers,
Lindane (γ-isomer) (Fig. 2.3) has the insecticidal property and as such is produced and used
commercially as an insecticide on fruits, vegetables, forest crops, and animals (ATSDR, 2005).
Lindane is one of the restricted pesticides used to treat seeds (barley, corn, oats, rye, sorghum
and wheat) prior to planting and as a pharmaceutical agent for the control of head lice and
scabies. It is highly persistent and because of its use in the past, it still contaminates the
environment, accumulating in soils, sediment, fish and plants, thus ultimately contaminating the
food chain (ATSDR, 2005). γ-HCH can be absorbed through the skin when it is used as a lotion,
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cream, or shampoo for the treatment and/or control of scabies and body lice. In general, HCH
isomers and the products formed from them in the body can be temporarily stored in body fat.
HCH breaks down in the body to many other substances; these include various chlorophenols,
some of which have toxic properties. Among the HCH isomers, β-HCH leaves the body most
slowly. α-HCH, δ-HCH, and γ-HCH, and the products formed from them in the body, are more
rapidly excreted in the urine;  small amounts leave in the feces and expired air (ATSDR, 2005).
According to ATSDR (2005), exposure to Lindane causes the following adverse health effects in
humans: neurological effects, liver toxicity, reproductive and developmental effects. Exposure to
high doses can cause symptoms such as vomiting, nausea, diarrhea, muscle weakness, seizures,
blood disorders and immune deficiencies. Studies have also shown possible associations between
lindane exposure in pregnant women and increased risk of spontaneous abortion and premature
delivery. Fortunately, ATSDR, (2005) explains that lindane is rapidly broken down and excreted
from the body. Long-term exposure to α- HCH, β- HCH, γ- HCH, or technical-grade HCH has
been reported to result in liver cancer. It can also result in blood disorders, dizziness, headaches,
and possible changes in the levels of sex hormones in the blood.
Although technical-grade HCH is no longer used as an insecticide in most developed countries,
α- HCH, β- HCH, γ- HCH, and δ- HCH have been found in the soil and surface water at
hazardous waste sites because they persist in the environment. In air, the different forms of HCH
can be present as a vapor or attached to small particles such as soil and dust; the particles may be
removed from the air by rain or degraded by other compounds found in the atmosphere. HCH
can remain in the air for long periods and travel great distances depending on the environmental
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conditions. In soil, sediments, and water, HCH is broken down to less toxic substances by algae,
fungi, and bacteria, but this process can take a long time
2.3.1.4 Cyclodienes
These are a group of organochlorines that are produced primarily from chlorination of
cyclopentadienes. Pesticides in the group include chlordane, aldrin, dieldrin, heptachlor,
Fig. 2.4: Chemical structures of some common cyclodienes (ATSDR, 2000)
Chlordane, endosulfan and endrin (Fig. 2.4). Their discovery dates back to the 1940s (Howard,
1991) and they were used to control soil insects, fire ants, cockroaches, termites, grasshoppers,
locust and other insect pests. Like most organochlorines, cyclodienes are very persistent in the
environment and tend to accumulate in biological as well as non-biological systems. Due to their
persistence, potential toxicity and tendency to accumulate in fatty tissues, their use has been
banned or severely restricted in most countries (Baird & Cann, 2012). Aldrin and heptachlor are
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rapidly metabolized by organisms but their metabolites, dieldrin and heptachlor epoxide,
respectively are more toxic and persistent than the parent material (Howard, 1991).
The compounds in this group are classified as neurotoxins. In both humans and animals the
primary acute toxic effects are on the central nervous system, including hyper excitability and
tremors followed by convulsions and possibly death. Acute poisoning from them may be fatal.
The compounds also affect the reproductive system, liver and kidney.
2.3.1.5  Toxaphene
Toxaphene (Fig. 2.5) is a mixture of hundreds of similar substances all of which are produced
when the naturally occurring hydrocarbon-camphene is partially chlorinated (Baird & Cann,
1999). It was used primarily to control insect pests on cotton and other crops as well as
controlling insect pests on livestock and killing unwanted fish in lakes. When toxaphene is
released into the environment, it can enter the air (by evaporation), the soil (by sticking to soil
particles), and the water (from runoff after rains). It does not dissolve well in water, and hence
found mainly in air, soil, or the sediment at the bottom of lakes and streams. Toxaphene is
capable of long distances transport by air and has been found in water, soil, sediment, air, and
animals in places far from where it has been used. It breaks down very slowly in the
environment. It is highly bioaccumulative and even when levels are low or confined to a certain
area, it could be high in individual animals. It is also persistent, chronically toxic and harmful to
living matter. Toxaphene was therefore banned for all registered uses by 1990 in the US
(ATSDR, 2010). Individuals may be exposed to toxaphene through drinking contaminated water,
eating fish, shellfish, or wild game from areas contaminated by toxaphene; also through
breathing contaminated air or through direct skin contact with contaminated soil. Toxaphene
causes damage to the liver and kidney, and is a potential liver carcinogen in mammals. When
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ingested in significant doses, it causes convulsion (ATSDR, 2010). Toxaphene does not appear
to accumulate in the body to any appreciable degree.   In the body, it is quickly broken down into
other substances and the breakdown products leave mostly in urine and feces. Small amounts
may leave through breast milk and exhaled air.
Fig. 2.5: Generalized structure of toxaphene (ATSDR, 2010)
(n is the number of chlorine substituted)
2.3.1.6  Health effects of Organochlorine Pesticides
The main source of human exposure to Organochlorine Pesticides (OCPs) is through diet,
particularly meat, dairy products and fish. The compounds become concentrated as they move up
through the food chain, and have been detected in humans and other mammals in regions even
where these compounds have not been used. They have been associated with increased risk of
cancer, developmental delays, and disruption of endocrine function, including thyroid hormones
which have a similar structure to theirs (Centre for Environmental Research and Children’s
Health (n.d.). Increase accumulation of these chemicals in the food chain may pose serious
health hazards (Jayashree & Vasudevan, 2007). For example, exposure to organochlorine
compounds has been reported to affect thyroid function in pre-school children (Osei-Tutu et al.,
2011). Low sperm count in males, birth defects, increase in testicular cancer and other
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reproductive and development effects (Weltman & Norback, 1983) have also been reported as a
result of organochlorine contamination.
According to Squipp (n.d.) the carcinogenicity of organochlorine insecticides is not well
established, however, some epidemiological studies among agricultural workers suggest an
association between organochlorine pesticide use and non-Hodgkin’s lymphoma, and long
persistent exposure indicates long term damage to the nervous system. (Squibb, n.d.). Exposure
to DDT early in life is associated with an increased breast cancer risk later in life (Cohn et al.,
2007). Many other organochlorine pesticides, such as mirex, chlordane and toxaphene, are
known to be carcinogenic as well (Weltman, & Norback, 1983)
2.3.2  Pyrethroids
The term pyrethroid bears similarity to the name of the natural insecticide mixture known
as pyrethrum or pyrethrins (Pyrethroids and Pyrethrins, 2013). Pyrethrum is one of the oldest
known naturally occurring mixtures of chemicals with insecticidal properties; found in two
species of asters: Chrysanthemum cinerariifolium and C. coccineum (ATSDR, 2003). Pyrethrum
was first recognized as having insecticidal properties around 1800 in Asia and was used to kill
ticks and various insects such as fleas, cockroaches, beetles and mosquitos. Six individual
chemicals have active insecticidal properties in the pyrethrum extract, and these compounds are
the pyrethrins. The six chemically active pyrethrins are: pyrethrin I and II, Cinerin I and II, and
Jasmolin I and II (EXTONET, 1994). Pyrethrins are contact poisons which easily penetrate nerve
system of insects and kill them. They however break down quickly in the environment,
especially when exposed to natural sunlight.
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Pyrethroids are Synthetic chemicals that are very similar in structure to the pyrethrins. While
chemically and toxicologically pyrethrins and pyrethroids are similar, the former are extremely
sensitive to light, heat and moisture. In direct sunlight, half-life can be measured in hours. The
pyrethroids, however, were developed to capture the effective insecticidal activity of their
botanical analogues-pyrethrins, with increased stability in light, higher insect toxicity and longer
residence time (Gosselin, 1984; Pyrethroids and Pyrethrins 2013). Both pyrethrins and synthetic
pyrethroids are sold as commercial pesticides used to control insect pests in agriculture, homes,
communities, hospitals and as a topical head lice treatment (Chemicalwatchfactsheet, n.d.).
Not all pyrethroids in the same class are equally toxic, however, irrespective of what group they
belong, pyrethroid insecticides are observed to be low in toxicity to mammals and birds but high
in toxicity to fish; especially if applied directly to water. They are very poorly soluble in water
but generally soluble in organic solvents; require very low doses to kill insects (high arthropod
toxicity) and are fast-acting. They bind tightly to soil and organic matter and are therefore not
effective in penetrating soil to kill pests. Figure 2.6 presents the structure of some pyrethroids.
2.3.2.1 Environmental fate of Synthetic Pyrethroids
Pyrethrins and pyrethroids are primarily released into the air because of their use as insecticides.
Pyrethroids are broken down or degraded rapidly by sunlight or other compounds found in the
atmosphere. Often, they last only 1 or 2 days before being degraded (ATSDR, 2003). Rain and
snow help remove the pyrethroids from air that are not rapidly degraded. Many of these
compounds are extremely toxic to fish, and although they are usually not sprayed directly onto
water, they can enter lakes, ponds, rivers, and streams from rainfall or runoff from agricultural
fields. Pyrethroids bind strongly to dirt and are usually not very mobile in soil, they are not easily
taken up by the
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Allethrin Permethrin
Fig. 2.6: Chemical structures of some pyrethroids. (ATSDR, 2003)
roots of plants and vegetation because they are strongly bound to the soil; however, they are
often sprayed directly onto crops and plants so they may be found on leaves, fruits, and
vegetables. Because these compounds adsorb so strongly to soil, pyrethroids usually do not leach
into groundwater. These compounds are eventually degraded by the microorganisms in soil and
water. They can also be degraded by sunlight at the surfaces of water, soil, or plants (ATSDR,
2003). However, some of the more recently developed pyrethroids can persist in the
environment for a few months before they are degraded. The extreme toxicity of pyrethroids to
aquatic organisms, including fish has been measured to be a lethal concentration (LC50) of
1.0ppb (Chemicalwatchfactsheet, n.d.). These levels are similar for most insects. Because they
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are toxic to all insects, both beneficial insects and pests are affected by their application.
Pyrethroids are moderately toxic to birds with most LC50 values greater than 1000 mg/kg. Birds
can however be indirectly affected by pyrethroids because of the threat to their food supply
(Mueller-Beischmidt, 1990).
2.3.2.2  Health Effects and Metabolism of Pyrethroids
Pyrethroids are not easily absorbed through the skin, but are absorbed through the gut and
pulmonary membranes. They have been proven to be neurotoxic when administered by injection
or orally. Reigart and Roberts, (2013) explained that low toxicity can be attributed to limited
dermal absorption and inhalation. Although limited absorption may account for the low toxicity
of pyrethroids, rapid biodegradation by mammalian liver enzymes is mostly responsible for this
phenomenon. They stated further those insects without liver function, exhibit greater
susceptibility to the chemical. Signs and symptoms of pyrethroid poisoning, according to Fishel,
(2014) may take several forms. Persons, especially children with a history of allergies or asthma
are particularly sensitive. Symptoms of acute toxicity due to inhalation include sneezing, nasal
stuffiness, headache, nausea, incoordination, tremors, convulsion, numbness, facial flushing, and
swelling, burning and itching sensations. The most severe poisonings have been reported in
infants who are not able to efficiently break down pyrethroids (Fishel, 2014;
Chemicalwatchfactsheet, n.d.). When ingested orally in significant doses, nervous symptoms
may occur, which include excitation and convulsion leading to paralysis, accompanied by
muscular fibrillation and diarrhea (EXTONET, 1994). Death in these cases is due to respiratory
failure. Symptoms of acute exposure may last for two days. Pyrethroids and their metabolites are
not known to be stored in the body nor excreted in the milk (Elliot et al., 1972; Hayes, 1982).
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They exit the body quickly mainly through urine and faeces. If exposure levels are high or they
occur over a long time, pyrethroids can accumulate in the fatty tissue and persist in the body for
a little longer. Some type of pyrethroids can also be retained for longer time in the skin and hair
(ATSDR, 2003)
2.3.3  Organophosphorus Pesticides (OPs)
Organophosphate compounds were first developed by Schrader shortly before and during the
Second World War. They were first used as an agricultural insecticide and later as potential
chemical warfare agents (Kazemi et al., 2012b). In the late 1990 and early 2000, with the advent
of increased awareness of terrorism, the OPs gained prominence as weapons of nerve agents for
mass destruction (Kazemi et al., 2012a). Organophosphate pesticides (OPs) currently are
considered the most widely used in the world (Ross et al., 2013) and the most hazardous to
vertebrate animals; being responsible for many cases of poisoning worldwide, particularly in the
developing countries (WHO, 1990; Soltaninejad & Abdollahi, 2009). Organophosphate
pesticides have largely replaced organochlorine insecticides, having the advantage of being more
rapidly biodegradable and hence less persistent in various environmental compartments
(Soltaninejad & Abdollahi, 2009). Concern about the effects of organophosphates on human
health has been growing as they are increasingly used throughout the world for a variety of
agricultural, domestic and industrial purposes. Authors such as Karalliedde et al., (2001) and
Ross et al., (2013) stated that organophosphorus pesticides have been used in agriculture and
horticulture; in veterinary medicines to prevent ectoparasitic infections of farm animals and
domestic pets; some human medicines (e.g. to treat head lice); and in public hygiene products
both for use by professional operators and the general public to control insect infestations in
public and residential buildings, outside spaces and gardens; and organophosphate compounds
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are used in industry as lubricants, plasticizers and flame retardants. Many organophosphates are
acutely toxic to those who may come into contact with them. Exposure to these chemicals by
inhalation, swallowing or absorption through the skin can lead to health problems (Baird &
Cann, 2012). Like the organochlorines, organophosphates concentrate in fatty tissues. The
neurotoxic effects due to OPs poisoning are well established and involve inhibition of the
enzyme acetylcholinesterase (AChE) causing changes in peripheral, autonomic and central
nervous system function (the cholinergic crisis). However, the possibility that long-term low-
level exposure to OPs in doses below that causing acute toxicity causes ill health is controversial
(Ross et al., 2013).
2.3.3.1 Classes of Organophosphates Pesticides
According to Kazemi et al., (2012a), organophosphate pesticides are compounds derived from
orthophosphoric acid esters in which a central, pentavalent phosphorus atom is doubly bonded to
either oxygen (O) or sulphur (S) atoms and singly bonded to two alkyl substitutions(two
methoxy (–OCH3) or ethoxy (–OCH2CH3)) and a third group more labile to hydrolysis (Fig.
2.7). They are put into three main subclasses as follows:
Fig. 2.7: General structure of organophosphates Insecticides (Kazemi et al., 2012a)
(R, normally corresponds to methyl or ethyl groups, the oxygen in the OX can be replaced by S)
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In type A organophosphate pesticides (Phosphates), the phosphorus is doubly bonded to an
oxygen atom (P=O). Dichlorvos and Chlorfenvinphos are examples of type A organophosphate
pesticides. Dichlorvos in particular is a relatively volatile insecticide that is used as a domestic
fumigant to kill flies in the room (Baird & Cann, 1999). Type B Organophosphates
(Phosphorothioates) contain S atom doubly bonded to P. Examples include Parathion,
Chlorpyrifos, Fenitrothion and Diazinon. In type C Organophosphates (Phosphorodithioates),
there is P-S in addition to P=S bond. Examples of type C organophosphates are Malathion and
Dimethoate (Baird & Cann, 1999).
According to Baird & Cann, (1999), organophosphates containing P=S units are converted
within insects to the corresponding molecule with P=O unit, which are more toxic but less stable
and with lower insect penetration ability. In the presence of water molecules, the P-O bond
within the structure splits to yield non-toxic substances such as phosphoric acid and its ions and
alcohols (Baird & Cann, 1999). Figure 2.8 presents the chemical structures of some of
organophosphorus pesticides mentioned.
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Parathion Chlorpyrifos
Malathion Dichlorvos
Fig. 2.8: Chemical structure of some common organophosphate pesticides (inchem.org, 2015)
2.3.3.2 Health Impacts of Organophosphorus Pesticides
The organophosphate compounds are most commonly associated with serious human toxicity.
Kazemi et al., (2012b) reported that among pesticides, organophosphates are responsible for
more than 50% of total poisoning cases whereas Kumar et al., (2010) asserted that they account
for more than 80% of pesticide-related hospitalizations. In contrast to the past, when chlorinated
hydrocarbon compounds such as DDT were commonly used, organophosphate insecticides have
become increasingly popular for both agricultural and home use because their unstable chemical
structure leads to rapid hydrolysis and little long-term accumulation in the environment (Kumar
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et al., (2010). This widespread use, however, has resulted in increased numbers of human
poisonings. In the 1970s, the United States Environmental Protection Agency (USEPA)
estimated that 3,000 hospitalizations per year were registered for insecticide poisoning in the
United States, with a fatality rate of 50% in the paediatric age group and 10% in adults (Kumar
et al., 2010). In 1983 data from the American Association of Poison Control Centres indicated
that the national incidence of insecticide exposures was 77,000, of which 33,000 involved
organophosphates (Veltri & Litovitz, 1983).
Concerns have been raised about the increasing levels of cancer incidence and possible links
with high levels of pesticide exposure. Kazemi et al., (2012a) reported that each year 500 people
are recorded as dying from cancer in Golestan province of Iran; 350 from stomach and 150 from
throat cancer. In addition, organophosphate compounds have been used as harmful nerve gases
and they induce oxidative stress resulting in cell death (necrosis and apoptosis) as well as
changes in metabolic and vital functions of the cells that leads to cancers. Many studies reviewed
by the Ontario College, Canada show positive associations between solid tumors and pesticide
exposure, including kidney cancer and failure (Abdollahi et al., 2004; Kazemi et al., (2012a).
Symptoms of acute organophosphate pesticide poisoning develop during or after exposure,
within minutes to hours, depending on the method of application. Exposure due to inhalation
results in the fastest toxic symptoms, followed by the gastrointestinal route and finally the
dermal route. Some of the most commonly early symptoms of OP poisoning include, headache,
nausea, dizziness, hyper secretion (sweating and salivation), muscle twitching, weakness, and
tremors, paralysis and starvation (Kazemi et al., 2012a). Some organophosphorus pesticides
(OPs) have been found to have endocrine disrupting properties (Kavlock, 2001). Epidemiologic
studies have suggested associations between OPs exposure and reproductive disorders
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(infertility, birth defects, adverse pregnancy outcomes, perinatal mortality) (Peiris-John &
Wickremasinghe, 2008). Organophosphate pesticides are suspected to alter reproductive function
by reducing brain acetyl cholinesterase activity and secondarily influencing the gonads.
2.3.3.3 Environmental Fates of Organophosphorus Pesticides
The fate of pesticides once they reach soil or water depends on their chemical and physical
characteristics and susceptibility to various transformation and transport processes. The OPs are
easily degraded by the hydrolysis of the ester linkage to produce harmless phosphoric acids and
alcohols (Baird & Cann, 1999). The OPs may also leach, however, persistence, or longevity, of a
pesticide influences the likelihood of leaching (Kazemi et al., 2012a). Soil factors that influence
leaching include texture and organic matter, in part because of their effect on pesticide
adsorption. Soil permeability (how readily water moves through the soil) is also important. A soil
that is more permeable is susceptible to leaching of OPs (Abrahams, 2002). Certain physical and
chemical properties of the pesticide, such as how quickly it is absorbed by plants or how tightly
it is bound to plant tissue or soil, are also important. Typically, heavy rainfalls lead to more
leaching. Organophosphate pesticides runoff can cause direct injury to non-target plants.
Organophosphate pesticides runoff can also contaminate groundwater and can cause injury to
crops, livestock or humans if the contaminated water is used downstream. Environmental
conditions, biota, soil and sediment characteristics and water composition also influence fate of
OPs residues (Abrahams, 2002). Degradation rates after release to the environment vary
extensively between substances, with half life from minutes to many years. Organophosphate
pesticides ingested by ruminants by means of residues on forage crops or as dermal or inhalation
exposure from spray drifts are exposed to potential metabolic attack by rumen microorganisms.
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2.4  Pesticide use in Developing Countries
According to Agrow, (as cited in Williamson et al., 2008) pesticides alone account for about
US$31 billion in the global market with 2.26 million tons of active ingredients used, as at 2001.
Of the world’s total production, 25% of pesticides is used in developing countries. Although
developing countries use only 25% of the pesticide produced worldwide, 99% of deaths due to
pesticides worldwide occur in them (WHO, 2008). Developing countries experience highest
death rate due to pesticides because use of pesticides tends to be more intense misused and
unregulated, health and education systems are weaker in these countries (WHO, 2008). Recent
trend unfortunately indicates that use of pesticides has risen in developing countries and the
fastest growing markets are in Africa, Asia, South and Central America and Eastern
Mediterranean (Fleischer & Waibel, 2003). It is estimated that average pesticide use per hectare
in Africa is low, reported as only 1.23 kg/ha, compared with 7.17 and 3.12 kg for Latin America
and Asia (Williamson et al., 2008) and tends to be intensively used mostly on cash crops such as
cotton, cocoa, oil palm, coffee and vegetables (Matthews, Wiles, & Baleguel, 2003). In the
1980s, Nigeria ranked first among West African countries in terms of quantities of pesticides,
importing about 5,346 metric tons of pesticides from the UK. Ghana ranked second with 299.5
metric tons, and Gambia third with 237.6 metric tons. Thus, Nigeria alone accounted for nearly
93% of UK pesticide exports to West African countries (Youm, Gilstrap, & Teetes, 1990).
2.5 Review of Pesticide Use in Ghana
Ghana, just like most developing countries experiences poor and inefficient pesticide practices
such as using incorrect/innappropriate dosages, use of unauthorised or banned products, cocktail
mixes of products, mixing with bare hands, poorly maintained or leaking application equipment,
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splashing pesticides onto crops using brushes or twigs and lack of minimal protective clothing
(Ntow et a.l, 2006; Fianko et al., 2010).
The findings of various researchers all agree that the estimates of the proportion of Ghanaian farmers
using chemical pesticides to control insects and diseases on their food and cash crops are above
recommended dosages. A 2003 survey by Dinham (2003) estimated 87% of farmers use pesticides
whereas a 2008 research by Horna et al, (2008) indicates 86%. Yet still, a recent study by
Northern Presbyterian Agricultural Services and Partners (2012) puts the percentage at 90.
Inappropriate use has consequences not only for the effectiveness of the intended pest control but
also for operator and consumer health, farm livestock, soil organisms, wildlife and vegetation,
and contamination of soil, water and air.
2.5.1 Pesticides in Fruits and Vegetables
Fruits and vegetables are known to be excellent sources of dietary fibre, vitamins minerals and
other natural substances that help protect the body from chronic diseases (Centers for Disease
Control and Prevention, 2012). Health experts therefore recommend daily intake of them to
remain healthy. In order to meet market demand, vegetable production in Ghana is on the
increase. Production activity can be seen around almost every water body, including utilization
of even urban sewage waters in some instances, for irrigation. Since vegetables in particular are
naturally infested by myriads of pests, production tends to rely heavily on pesticide input to
improve yield and market value. Thus, an attempt to improve health through consumption of
fruits and vegetables come with an attendant health hazard of bacterial or/and pesticides
contamination. Analysis of pesticide residues in crops in Ghana has been carried out to some
extent, with the spectrum stretching across vegetables, fruits, cereals and cash crop like cocoa.
Target pesticide in analyses is mainly organochlorines but currently, organophosphorus
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pesticides and synthetic pyrethroids, are covered; however, carbamates, fungicides, weedicides
and others are beginning to receive some attention. Even though there is enough documented
work, review of literature on pesticide residue analyses shows there is no planned systematic
temporal and spatial monitoring  efforts by the designated authorities like the Ghana
Environmental Protection Authority (Ghana EPA) and Ghana Standards Authority (GSA) to
investigate levels of pesticide residues in environmental matrices and in food crops in particular
on consistent basis. Work in this direction is sporadic and carried out mostly by individual
researchers, academic institutions and sponsored cooperate bodies with specific or parochial
interest and on ad hoc basis. Pesticide residue levels in fruits and vegetables in particular have
been a matter of health and research interest considering their rate of daily consumption.
A recent study by Asiedu (2013) on residue of organochlorine pesticides, organophosphorus
pesticides and synthetic pyrethroids in fruits and vegetables from three regions in Ghana
recorded the presence of over 30 pesticides with incidence rate between 40-52% of the targeted
pesticides. Lindane, chlorpyrifos and cypermethrin were the most frequently encountered. This
singular work in three regions of Ghana (Greater Accra, Central and Eastern) reveals how
widespread the use of pesticides is in the fruits and vegetable farming industry. Similarly, an
earlier work done in 2009 and 2010 by Bempah, Buah-Kwofie and Denutsui (2011), in
determining residue level of 7 organochlorine pesticides (OCPs) and 5 synthetic pyrethroids in
about 350 locally produced fruits and vegetables in the Kumasi metropolis recorded 19% of the
samples registering pesticide residue levels exceeding the European Commission Maximum
Residue Limit (EC MRL). The fruits and vegetables investigated included water melon,
pineapples, pawpaw, banana, mango, onions, chili pepper, tomato, lettuce, cabbage, cucumber
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and okra. Within the same period of 2009 to 2010, Bempah et al., (2012) conducted similar
exercise in the Accra metropolitan area and found out that methoxychlor, lindane, endrin and
dieldrin recorded residue levels above the EC MRL in crops such as: onions, pineapples, lettuce,
cabbage, cucumber, carrot and banana. Chlorpyrifos, was however, the only organphosphate
detected to be above the EC MRL; and this was in pineapple. Botwe et al., (2011) also recorded
OCP levels in the range of 0.1-46.95ug/kg wet weight in tomato, pepper, onions and garden egg
from farming communities of Akumadan in the Ashanti Region of Ghana. Even though levels in
this case were low, researchers expressed health concerns because of the persistent and
bioaccummulative nature of the OCPs. The presence of OCPs in food crops is a matter of much
concern since most of the OCPs have been banned from use in Ghana. Their presence is often
not only detected with large incidence rate but in many cases, their levels are also above
recommended limits. Ntow (2008), Kokroko et al., (2012), Owusu-Boateng and Amuzu (2013)
and Agyekum et al., (2014) all recorded residue levels of OCPs exceeding FAO/WHO and EC
MRL guidelines in fruits and vegetables such as mango, cabbage, pineapple and tomato. Locally
produced fruit-based soft drinks were also found to contain appreciable levels of OCPs (Bempah
et al., 2011).
The presence of organophosphorus and synthetic pyrethroid pesticides has also been detected.
Odhiambo, Gbewonyo and Obeng-Ofori (2014) recorded high levels of chlorpyrifos in cabbage
from suburbs of Accra and Mampong-Akuapem in the range of 55-124 mg/kg; far above the
FAO/WHO MRL; for instance Chlorpyrifos recorded 55-124 fold increases above the
recommended MRL of 1mg/kg. Pyrethroid residues from their investigation were also not only
above MRL, but 12-18 folds above levels recorded in an earlier study by Ninsin (1997), and 2-15
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folds increase above recommended MRL. Gonu et al., (2012) investigated pyrethroid residual
levels in chili pepper from Northern Region of Ghana. Their report indicated that whereas
residual concentration of Fenvalerate equaled the European Union MRL, that of Fenpropathrin
was above it. The presence of eight other pyrethroids was registered, though at very low levels.
Gbewonyo and Afreh-Nuamah (2008) also detected the presence of cypermethrin, DDT,
dimethoate and chlorpyrifos in shallots from the Volta Region of Ghana with residual level of
chlorpyrifos in most of the samples above the Codex maximum permissible level. Tordzaglah et
al., (2013) investigated specific levels if chlorpyrifos in pineapples from Amasaman District.
They analysed the extracts from epicarp and mesocarp and found out that 10% of all samples
recorded residue levels above European Commission MRL of 0.05 mg/kg.
Cocoa, a cash crop and a major foreign exchange earner for Ghana has also received a
considerable attention in pesticide residue analysis. Boakye (2012) investigated the levels of
OCPs, organophosphorus pesticides and synthetic pyrethroids in cocoa beans from two principal
producing regions in Ghana; Ashanti and Brong-Ahafo Regions. The research revealed that 45%
and 50% of pesticide residue detected in Ashanti and Brong-Ahafo Regions, respectively were
above their EU allowable limits, with Chlorpyrifos registering as high as 9.81 mg/kg and 10.55
mg/kg in the former and latter regions, respectively. Endosulfan and delta-lindane recorded the
lowest residual concentration of 0.01mg/kg each in both regions. Similar work done by Blankson
(2011) in Brong-Ahafo Region alone showed that cocoa beans contained DDT and its isomers as
well as Endosulfan, although in lower concentrations. However, organophosphorus pesticides
such as ethoprophos, fenitrothion, malathion and profenofos registered residual levels of 0.0573
mg/kg, 0.0537 mg/kg, 0.0581 mg/kg and 0.6368 mg/kg respectively; which were all higher than
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the maximum limit set by the EU. Synthetic pyrethroids such as permethrin, cypermethrin and
fenvalerate also registered residual concentrations above their EU MRL. Lindane, a pesticide that
has been listed among the Prior Informed Consent (PIC) pesticides is heavily dependent upon by
cocoa farmers in controlling capsids. Owusu-Ansah et al., (2010) as well as Apau and Dodoo
(2010) investigated the levels of lindane in cocoa beans in Ashanti and Central Regions of Ghana
respectively. Whereas Owusu-Ansah et al., (2010) reported no detectable concentration of
Lindane in all samples, Apau and Dodoo (2010) recorded a residue range of 0.055-3.318mg/kg;
a concentration range that indicated levels above the EU MRL. Frimpong et al., (2012);
Frimpong, et al, (2012a, 2012b & 2012c); Frimpong et al., (2013) and Frimpong, Yeboah, and
Fletcher, (2013) monitored  over 15 OCPs in cocoa beans ready to be exported from Tema and
Takoradi port of Ghana. The OCP residual concentrations in all cases were low, ranging from
0.01-103.0 µg/kg. The residual presence of organophosphorus pesticides such as: dimethoate,
pirimophos-methyl, chlorpyrifos and fenitrithion were also low. Methamidophos, profenofos and
malathion concentration were however appreciable, being at the threshold of EU MRL. Synthetic
pyrethroids were also detected but in traces. Allethrin, fenvalerate and cypermethrin average
concentrations bordered on the Japanese MRL threshold.
Work done by researchers in other crops may exist but not easily accessible. The work of Akoto,
Andoh, Darko, Eshun, and Osei-Fosu (2013) indicates even cereal crops are not exempted from
pesticide contamination. Maize and cowpea from Ejura in the Brong-Ahafo Region were
assessed by Akoto et al for the presence of OCPs, organphosphorus pesticides and synthetic
pyrethroids. Fifteen OCPs were detected and 5 of them: β-lindane, β-endosulfan, Heptachlor,
p,pʹ-DDT and p,pʹ-DDE had levels above their EU MRL. So also levels of synthetic pyrethroids
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such as Fenpropathrin and λ-cyholothrin exceeded their respective EU MRL. In maize, with the
exception of Chlorpyrifos, levels of organophosphorus pesticides were all within limits.
2.5.2 Pesticides in Fish
According to Akan, et al., (2013a) presence of pesticides in water has the potential to impart
objectionable and offensive taste, odours and colours to fish and aquatic plants. Pesticides in
water column normally adsorb to sediment particles and the sediment particles in turn adsorb to
entities within the aquatic medium. Pesticide-laden sediments are easily adsorbed by fish on the
skin and also on the gills; during feeding by ingestion of water.  Persistent pesticides like the
organochlorines readily accumulate in animal tissues and since they are poorly hydrolysed, they
cause serious bioaccumulation and bioconcentration problems in food chains (Nowell et al.,
1999). The immediate banks of every fresh water body in Ghana are subjected to human
activities of one kind or the other, especially agriculture. Fish constitute a very important protein
source in diet all over the globe and it is necessary to have a continuous investigation into levels
of pesticides in their tissues, particularly because the water bodies in which they are found
invariably receive run-offs from adjacent agricultural fields. The dearth of investigations on
pesticide content of fish species in the country has resulted in scanty information. The few
researches done in this field have been sporadic over time and results reveal generally low
residual levels of pesticides.
Darko, Akoto & Oppong (2008) investigated the levels of OCPs in Tilapia zilli from Lake
Bosomtwi and registered the presence of endosulfan, aldrin, dieldrin, lindane, p,pʹ-DDE and p,pʹ-
DDT within a concentration range of 0.018 – 5.232 ng/kg. DDE and DDT both recorded highest
incidence and concentration. Essuman, Togoh & Chokky (2009) also evaluated the presence of
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four OCPs (o,pʹ-DDE, p,pʹ-DDD, p,pʹ-DDT and Propiconazol) and four organophosphorus
pesticides (Fenitrothion, Chlorpyrifos, Dichlorvos and Diazinon) in one  fish species,
Sarotherodon melanotheron from Fosu and Etsii lagoons in Central Region of Ghana. Whereas
o,pʹ-DDE was not detected in any of the fish sample, the other three OCPs were present, albeit at
very low concentration, in a range of 0.0001 – 0.0098 mg/kg. Similarly, only Diazinon and
Chlorpyrifos were registered in very low concentration range of 0.0001 – 0.0003 mg/kg. Afful,
Anim & Serfor-Armah (2010) investigated pesticide residue levels in six fish species from
Densu River with respect to 14 OCPs. The fish species were: Heterotis niloticus, Channa
obscura, Hepsetus odoe, Tilapia zilli, Clarias gariepinus and Chrysichthys nigrodigitatus. Seven
of the targeted OCPs recoded 100% incidence whilst the rest recorded 75%, indicating the
ubiquitous nature of these chemicals. Their levels were however low, in a range of 0.3-71.3
ug/kg. Gbeddy et al., (2012) in a separate study focused on the presence of 15 OCPs in gills and
muscle tissues of only two species of fish; Tilapia zilli and Chrysichthys nigrodigitatus from the
Volta Lake. Thirteen of the targeted OCPs were identified in all the samples. Whereas 100%
incidence was recorded for beta-lindane, delta-lindane, p,pʹ-DDD, Heptachlor and Endosulfan
sulphate in the muscle; beta-lindane, delta-lindane, p,pʹ-DDD, gama-chlordane, Endosulfan-
sulphate and Methoxychlor also registered 100% incidence in the gills. The mean residue
concentration ranges in muscle and gill tissues were 0.10-17.35 ng/g and 0.56-37.75 ng/g,
respectively. A recent study by Adu-Kumi et al., (2010) on edible fish in Lake Volta recorded
the presence of DDT compounds, Chlordane compounds, Hexachlorobenzene and Lindane
isomers in tilapia and catfish. This research report suggests that the Volta Lake and its environs
are possibly experiencing fresh contamination by diverse kinds of organochlorine chemicals;
both banned and restricted.
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2.5.3 Pesticides in sediments of water bodies in Ghana
Pesticides in aquatic medium can bioconcentrate unto suspended materials and get deposited to
the substratum. Sediment serves as a principal reservoir and sink from which pesticides can be
released to groundwater, redistributed into the overlaying water column and as well be adsorbed
to suspended particulate matter and aquatic flora and fauna (Xue, et al., as cited in Williams,
2013). Investigations carried out on Ghanaian water bodies revealed that sediment contain
appreciable levels of pesticides, especially, organochlorine pesticides. Darko et al., (2008)
detected lindane, endosulfan, aldrin, p,pʹ-DDE and p,pʹ-DDT in the sediment of Lake Bosomtwi
at concentrations of: 6.755, 9.683, 0.065, 0.072, 8.342 and 4.410 ng/kg respectively; with DDE
being widespread, registering occurrence frequency of 98%. Later studies by Afful, Awudza,
Osae, and Twumasi, (2013a) on the same water body registered 16 OCPs, and at higher
concentration levels; along with 5 polychlorinated biphenyls (PCBs). The concentration range of
the 16 detected OCPs were 0.01 – 15.23 ug/kg. Endosulfan sulfate recorded the highest of
15.23ug/kg, followed by methoxychlor and β-endosulfan at 5.95 and 5.60 ug/kg respectively.
Ntow (2005) analysed the presence of six OCPs namely: Lindane, α-endosulfan, β-endosulfan,
endosulfan sulphate, p,pʹ-DDT and p,pʹ-DDE, in the Volta Lake and found out that these
chemicals were very widespread, with the least frequency of 86% and individual mean
concentration of 2.30, 0.21, 0.17,0.36, 9.00 and 52.3 ug/kg dry weight respectively; indicating
the persistence of DDT isomers. Fianko et al., (2011) and Kuranchie-Mensah et al., (2012)
investigated the residual levels of 14 OCPs in Densu river sediment and reported high levels. The
14 OCPs included Dieldrin, Endrin, Endrin ketone, Endrin aldehyde, Methoxychlor, Heptachlor,
Aldrin, γ-lindane, δ-lindane, DDT, DDE, α-endosulfan and α-endosulfan sulfate. Fianko et al,
(2011) reported concentration range of 0.10ug/kg – 163.0ug/kg dry weight whilst that for
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Kuranchie-Mensah et al., (2012) was 0.03 ug/kg – 10.98 ug/kg dry weight. Αlpha-endosulfan
and Aldrin registered the highest concentrations by both investigators. The huge difference in
concentration range as reported by both researchers could be due to different locations of
investigation along the same river. Whereas Fianko et al., targeted the main Densu and its
tributaries in the forest zone where industrial crops such as cocoa, coffee, oil-palm and food
crops are produced on large scales, Kuranchie-Mensah et al, sampled further down at Weija
where the Densu River was dammed to form a reservoir for potable water supply. Afful et al.,
(2013) carried the investigation further by assessing levels of synthetic pyrethroids, namely:
bifenthrin, fenpropathrin, lambda-cyhalothrin, cyfluthrin, cypermethrin, fenvalerate,
deltamethrin, allethrin and permethrin in sediment of Weija Lake. The concentration range was
0.15 – 6.60 ug/kg. Even though the concentration levels were below maximum residue limit set
by the EU, the registering of the presence of the wide spectrum of pyrethroids in this
investigation indicates increasing diversification in the use of pesticides.
2.5.4 Pesticides in Ghanaian Waters
Researchers have reported presence of pesticides in various water bodies in the country. The
Volta Lake, although by far the biggest water body in the country, has not received adequate
study into levels of pesticides in its waters. Ntow (2005) monitored the residues of chlorinated
pesticides in one hundred and eighty water samples from six locations in the Volta Lake. Out of
these, only four organochlorine pesticides were detected, namely: Lindane, α-endosulfan, β-
endosulfan and Endosulfan sulphate. About 23% of the samples contained detectable levels of
Lindane with a mean concentration value of 0.008µg/L. Alpha-endosulfan was present in the
highest concentration, with a mean value of 0.036µg/L, being detected in 16% of samples
analysed. Β-endosulfan was detected in 18% of the samples while Endosulfan sulphate was
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found in 10% of the samples. DDT and DDE were however not detected. Fianko et al., (2011)
reported the presence of OCPs in 3.3% of samples of water from River Densu. Concentration of
detected OCPs varied between 0.1µg/L and 48.6 µg/L in compounds such as Dieldrin, DDT,
Endosulfan sulphate, γ-HCH, Aldrin, γ-chlordane, DDE and Endrin. γ-HCH and γ-chlordane
recorded the highest frequency of 4.4% each, and Endosulfan sulphate recorded the highest
residual concentration of 48.6µg/L. Afful, Awudza, Osae, and Twumasi, (2013b) detected the
presence of seven synthethic pyrethroids in water from Densu around Weija in a low range of 0.1
µg/L – 3.5 µg/L. Cyfluthrin was most ubiquitous, with 100 per cent frequency of occurrence.
Agyapong, Lugushie, Fei-Baffoe and Atabila (2013) also recorded the presence of seven OCPs
in waters from the River Tano in Brong Ahafo of Ghana. The OCPs were: Lindane (and all its
metabolites), Aldrin, Dieldrin, Endrin, Chlordane, Heptachlor and all metabolites of DDT. Their
results indicated that the mean concentrations of aldrin, dieldrin, endrin, heptachlor and cis-
heptachlor epoxide all exceeded the WHO limits and could pose a threat to human and aquatic
life within the watershed.
Darko et al., (2008) and Afful et al., (2013) studied the water quality of Lake Bosomtwi whereas
Darko et al recorded the presence of only 5 OCPs, later investigation of Afful et al., (2013)
recorded more than 15 organochlorine compounds, including Polychlorinated biphenyls (PCBs).
This indicates degeneration of water quality in the lake with time. The reason could only be
attributed to the increasing anthropogenic activities around the lake, especially agricultural ones.
Botwe, Ntow and Nyarko (2012) investigated 2 streams and 9 ground water sources (wells) in
the Ashanti region. The stream water registered the precence of α-endosulfan, β-endosulfan and
Endosulfan sulphate at the mean concentrations of 0.027, 0.021 and 0.011 µg/L respectively.
None was however detected in ground water.
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2.6 Government Policy and Regulation on Pesticides
Ghana is a signatory to a number of international Conventions on chemicals and as such is under
obligation to put proper policies and regulations in place for safe importation, management and
use of chemicals and pesticides.
2.6.1 Signatory to International Regulations
The main international regulations and legal instruments relating to pesticides use and to which
Ghana is a signatory are:
The International Code of Conduct for the Distribution and Use of Pesticides (also known
as the FAO Code of Conduct), which is a voluntary international mechanism for countries to
regulate the availability, distribution and use of pesticides in their countries. It was revised in
2002. (Northern Presbyterian Agricultural Services and Partners, 2012)
The Rotterdam Convention on Prior Informed Consent is an international treaty designed to
facilitate informed decision-making by countries with regard to trade in hazardous chemicals. It
establishes a list of covered chemicals and requires parties seeking to export a chemical on that
list to first establish that the intended importing country has consented to the import. It also
requires that a party seeking to export a chemical that is not listed under the Convention, but is
subject to a ban or severe restriction in its own territory, must provide notice to the importing
country of the proposed export. The Convention entered into force on February 24, 2004 (UNEP,
2005, 2008). By this provision, exports and imports of banned or severely restricted pesticides is
prevented or highly restricted. It also encourages identification of pesticides that cause problems
to health or the environment. Ghana signed the Rotterdam Convention in 1998 and ratified it in
2003 (Northern Presbyterian Agricultural Services and Partners, 2012).
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The Stockholm Convention on Persistent Organic Pollutants, which aims to protect human
health and the environment from persistent organic pollutants (POPs). Parties to the Convention
are obliged to develop a National Implementation Plan (NIPs) which identifies the current state
of these chemicals and their management and articulates the policy, program, priorities and
activities that Parties will take to eliminate the use of these chemicals (FAO, 2006).
The ILO Convention on the Safety of Chemicals at the Workplace
Ghana is a party to this convention. Ghana’s response to the needs of this Convention however is
a comprehensive piece of legislation on labour. This law is divided into several parts and
includes Occupational Health, Safety and Environment. Under this last part employers are
enjoined to ensure that their employees work under safe and healthy conditions. Furthermore
they are to protect workers from “toxic gases, noxious substances, vapours, dust, fumes and other
substances likely to cause risk to safety or health. Failure on the part of the employer to do such
or to report any occupational accident is punishable. Labour Inspectors have the right to take or
remove for purposes of analysis, samples of materials and hazardous or chemical substances
used or handled by workers in the course of their employment (FAO, 2006).
Although Ghana is a signatory to all the aforementioned international regulations, there is little
compliance or implementation of them, largely due to insufficient allocation of resources
(Northern Presbyterian Agricultural Services and Partners, 2012). For instance the Ghana EPA
proposed the creation of a specific Fund for pesticide management to increase resources
available for pesticide surveillance and training. This was necessary since the existing
Environmental Fund never had any specific allocation for pesticide surveillance. In this
direction, industries agreed to contribute 0.1 per cent of the values of their import to the fund, yet
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the proposal was rejected by the Ministry of Finance (Northern Presbyterian Agricultural
Services and Partners, 2012). The government of Ghana, as a matter of fact, is aware of the
dangers of pesticides and has taken a number of measures to ensure their safer use. One
important step is the establishment of the legislative framework to manage and control the use of
all manner of chemicals.
2.6.2 National Legislative Framework for Pesticides Management
Even though there are various laws on chemical management in existence, there is no
comprehensive piece of legislation on chemicals management in Ghana (EPA Ghana, 1997,
2007). Laws on Chemicals Management are scattered in various pieces of Legislation. Together,
these laws provide a framework for the management of all chemicals and pesticides in Ghana.
They include Principal Acts, Subsidiary legislation, guidelines, codes of conduct and practice
(FAO, 2006).
2.6.2.1 The most important Act is the Environmental Protection Act of 1994 (Act 490). This
Act forbids any pesticide imports except where they have been registered, requires the Ghana
EPA to keep a list of registered pesticides and requires all importers and sellers to keep a record
of the pesticides imported or sold.  The Act also allows for EPA inspections to take place on
grounds of reasonable suspicion that illegal pesticides are being stored and for pesticides and
equipment to be seized. The EPA is the key Agency responsible for the management of all
Chemicals in Ghana. The Act establishes a Committee of the Environmental Protection Agency
Board known as the Hazardous Chemicals Committee. The functions of the Hazardous
Chemicals Committee are to monitor the use of hazardous chemicals by collecting information
on the importation, exportation, manufacture, distribution, sale, use and disposal of such
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chemicals; advise the Board and the Executive Director on the regulation and management of
hazardous chemicals; and perform such other functions relating to such chemicals as the Board
or the Executive Director may determine (EPA Ghana, 1999). To be able to perform its duties
under the Act, the EPA has as one its Divisions, the Chemicals Control and Management Centre
(CCMC) which plays a vital role in the management of Chemicals in Ghana. The CCMC has as
its primary objective, to protect human health and the environment from the possible effects of
chemicals The CCMC issues Chemical Clearance Permits to importers of Industrial Chemicals.
One permit is given per each import. The CCMC also supervises the disposal of obsolete
chemicals.
2.6.2.2 The Pesticides Control and Management Act, 1996 (Act 528)
Act 528 is the only piece of legislation that addresses the manufacture, classification, labeling,
importation, exportation, and use of pesticides in Ghana. This Law has very broad application
and affects government, companies, manufacturers, users, vendors, importers, exporters,
advertisers and formulators. The law focuses on the registration of pesticides, the restriction and
suspension of the use of pesticides, the licensing of pesticide dealers and the penalties for non-
compliance. Act 528 stipulates that no person shall import, export, manufacture, distribute,
advertise, sell or use any pesticide in Ghana unless the pesticide has been registered by the EPA.
The Agency will only register a pesticide if it is satisfied that the pesticide is safe to use under
Ghana’s local conditions and effective for the use for which it is intended (FAO, 2006).
2.6.2.3 The Food and Drugs Law, 1992 (Act 305B)
This Act aims at regulating the manufacture, preparation, sale or supply, export or import and
use of food, drugs, cosmetics and chemical substances so as to protect the health of consumers.
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The food and Drug Law Act established a body known as the Food and Drugs Board (FDB),
which has the responsibility of performing the administrative functions under the Law. Though
this law does not make specific reference to banned or severely hazardous chemicals, the word
“chemical substance” is defined under the Law as “any substance or mixture of substances
prepared, sold or represented for use as a germicide, an antiseptic, a disinfectant, a pesticide, an
insecticide, a rodenticide, vermicide, or detergent” (FAO, 2006). The Law prohibits a person from
manufacturing, preparing, selling or supplying, exporting or importing into Ghana any chemical
substance unless it has been registered with the FDB. There seems to be an overlap in the
regulatory functions of FDB and EPA. In practice, however, the FDB stays clear of the
registration and regulation of pesticides use. Despite this fact, there is still the need to rectify this
obvious overlap so as to ensure that the functions of each body are clarified. With regard to
enforcement, it is an offence for any person to sell any chemical substance (that has in or on it
any substance) which when used according to the directives on the label accompanying such
pesticide may cause injury to the health of the user. The Act empowers authourised officers of
the FDB at any hour reasonable for the proper performance of their duty to open and examine
any receptacle or package, which he believes, contains any pesticide. Such officers also have the
power of seizure of such products. Furthermore, it an offence for any person to use or dispose of
any chemical substance (pesticide) in a manner likely to cause contamination of food or water
for human consumption or in a manner likely to be injurious or dangerous to the health of any
person. It is an offence under this law for anyone to label, package, sell or advertise any chemical
substance in a manner that is false, misleading or deceptive as regards its character, constitution,
value, potency, quality, composition, merits or safety. The Law prescribes the penalty for
offences committed as either the payment of a fine or a term of imprisonment or both.
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2.6.3 Control of Imports and Exports
2.6.3.1 Export and Import Act, 1995 (Act 503)
This Act seeks to regulate the efficient import and export of all goods, including chemicals, into
and from Ghana. The Customs, Excise and Preventive Service (CEPS) play an important role in
the enforcement of this Law. The Law stipulates that where an importer or exporter is required
under any other enactment to obtain a permit or license or certificate, in addition to other
certification for any category of goods, certified copies of same shall be given to the
Commissioner of CEPS (FAO, 2006).
2.6.3.2 The Customs, Excise and Preventive Service (Management) Law of 1993
The Customs, Excise and Preventive Service (Management) Law of 1993 regulates all imports
into and exports from Ghana, including chemicals. CEPS currently performs certain duties on
behalf of EPA. It examines documents and as well as certificates and permits granted by the EPA
to ensure that they cover the particular importation or exportation that the bearer of permit
claims. Records of chemical import returns are submitted by CEPS to the EPA on a quarterly
basis. The law gives CEPS officers the power to search persons, premises and baggage and seize
prohibited goods, including chemicals, and they are required to prevent the illegal import into
Ghana of any pesticide. In order to implement this law, CEPS officers are given the same powers
as the police. They are also required to keep a list of all pesticides imported into the country for
onward submission to the EPA. The Plant Protection and Regulatory Services Directorate of the
MOFA,  (PPRSD) also has staff – quarantine staff – at border posts looking for illegal imports of
pesticides, among other things (FAO, 2006).
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CHAPTER THREE
STUDY AREA
3.1 Background and Reconnaissance survey of the study area
The River Afram is a major tributary of the Volta Lake in Ghana. Gordon and Amatekpor (1999)
noted that after the creation of the Volta Lake following its damming in 1964, there was flooding
of large area that affected about 80,000 people. The villages and farmlands of these people were
inundated by water and the Ghana government had to put these people in new resettlement
townships further upland beyond areas demarcated for the newly created lake. The Afram
tributary was one of the major outlets of the then River Volta and as such experienced serious
rise in water levels, leading to flooding of its banks and consequent relocation of communities. It
is worthy of note that during the creation of the Volta Lake, potential for irrigation farming on
large tracts of lands in the Afram plains in particular was recognized. As such, experimental
irrigation farming of vegetables was set up in three communities, namely Ampem, Dedeso and
Amartey (Gordon and Amatekpor, 1999).
The study area occupies part of the Eastern Region that lies along the lower reaches of the Afram
tributary of the Volta Lake (Fig. 3.1) and for the purpose of this research, it will be referred to as
the Afram arm of the Volta Lake (AVL). This area extends across three administrative districts
(Fanteakwa, Kwahu South and Kwahu East) of the region. In the quest to select the appropriate
sites for the study, a stretch of land area and communities bordering on the lower reaches of
Afram arm of the Volta Lake (AVL) was surveyed from lower part of Fanteakwa District,
through Kwahu South to the northern part of Kwahu East districts, lying within the coordinates:
N 060 34ʹ 124″ - 060 43ʹ 696″ and W 0000 14ʹ 089″ - 0000 37ʹ 810″ (Fig. 3.1). Many of the
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communities within this area are involved in food crop production along the banks of the AVL,
but of particular interest is the predominance of irrigation farming of fruits and vegetable crops;
both on small holder and large commercial basis. The farm size of the small-holder farmers was
generally less than one acre while others are much bigger. Sampling sites near six communities
on the lower banks of the AVL were chosen for the study. These are: Odortom, Dedeso, Kwahu
Amanfrom, New Jerusalem, Adawso and Kotoso. Access roads to the communities are very
deplorable and barely motorable. The communities were therefore chosen considering relative
ease of accessibility to them; and also because farming along the banks here is done on large
scale compared to other bank. The location of these sampling sites along the AVL enables the
study to span the entire or the greater length of the Afram tributary (Fig. 3.1) and hence can be
considered to be fairly representative of the entire region along both banks of the Afram tributary
that engage in fruits and vegetable farming.
3.2 Ethnicity and livelihood of people in the study area
Eastern Region has a heterogeneous population made up mostly of the Akans and the Ga-
Adangbes. Other major ethnic groups are Ewes, Guans and ethnic mix from the Northern Region
of Ghana. Ewes, and to a lesser extent, the Ga-Adangbes are however the predominant
inhabitants along the AVL as fisher folks. Dependence on fishing solely is no longer sustainable
hence the practice of irrigation farming which over the years has turned out to be more
economically profitable.
Available records indicate that as at 2013, an estimated 5,753 and 4,700 farmers were actively
engaged in market-oriented farming along the Afram arm in Kwahu East and Fanteakwa
Districts respectively; and these figures constitute about 72% and 75% of the farming population
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of the respective Districts (Fanteakwa and Kwahu East District Profiles). Cultivated food crops
along the banks include sweet potatoes, maize, cassava, cowpea and fruits and vegetables. Due to
the short maturing period of fruits and vegetables, they are cultivated all-year round with reliance
on water from the Afram tributary for irrigation. The main fruits and vegetables cultivated are
pepper, onions, okra, tomato, watermelon and egg plants. As at 2013, the estimated annual
production in metric tonnes of pepper, egg plant, onions water melon and cowpea respectively
were: 25,292.95, 12,673.50, 1,077.79, 10,425.24 and 787.15 in the Fanteakwa District alone.
These productions came from farmlands of average area of about 0.4 hactare per holder
(Fanteakwa District Assembly, 2014). Similarly, the average crop production per holder in the
Kwahu East District with about 0.75 hactares for pepper and water melon; and 0.25 ha for okra
and tomato were 456, 480, 90 and 273.60 metric tones respectively (Kwahu East District
Assembly, 2014).
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Fig. 3.1: Map of Study area showing sampling sites
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3.3. Geology, soil, topography and drainage, of the study area
The topography of the study area is generally hilly and rugged with undulating landforms. The
average height of the land is about 8762 feet above sea level. Underlying these land masses are
several rocks or parent rocks from which several different soils have developed. These parent rocks
include the Birimian foundation and Voltaian Metamorphosed sediments, with their associated
rocks such as phyllites, schist and granites. Most of the hills are capped with iron pans, bauxite and
kaolin. Gold and bauxite are also embedded within these rocks. The area is well drained with
several rivers portraying the trellised drainage pattern system. Some of the important rivers are the
Afram, Pra, Akrum, Osubin, Amanfuesua and Dede rivers. Most of these rivers are seasonal with
most of them overflowing their banks during the rainy season and drying up during the dry season
(Fanteakwa District Assembly, 2014). The river Afram is a major tributary of the Volta and flows
through the northern border of the Kwahu South District within the Afram Plains while the Pra
River take its source from Kwahu Twenedruase and flows through Akwasiho and Kwahu Praso
where it leaves the district.
The Volta Lake is an important resource which provides employment to many fishermen and fish
mongers who have settled along the lake (Kwahu South District Assembly, 2014). The underlying
Birimian formation in the Kwahu South District is an important geological formation since it
contains most of the valuable mineral exported from the country for foreign exchange such as gold,
bauxite, diamonds etc. Gold is believed to be in the district but currently remains unexploited. Soils
developed over these rocks in the district are the Atewa-Anum simple formation (association)
Nzima-Bekwai/Oda compound association, Atewiredu-Katie Simple Association, Bediesa-
Yaya/Asuansi-Atewa complex association, Nankesi-Akrosi/Nta Offin compound association
(Fanteakwa District Assembly, 2014). Soils belong to the forest ochrosols and consist of fine sand
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loams, congregational loams, non-gravel sandy clay loams and iron pan soils. These soils possess
good chemical properties of clay and appreciable amount of humus, making them generally fertile
for the production of both cash and food crops such as cocoa, coffee, plantain, cassava and yams.
3.4  Climate and Vegetation
Information from the three district assembly offices (Kwahu East District Assembly, 2014; Kwahu
South District Assembly, 2014 and Fanteakwa District Assembly, 2014) within the study area
presents the same account of climate and vegetation. The study area lies within the wet-semi
equatorial region with mean annual rainfall between 150.0mm to about 2000mm. The area
experiences all year round sunshine with an average temperature of 24° C. During the rainy season
there are brief interruptions of the sun by thick cloud cover. There is a double maxima rainfall
during the period of June and October in each year with just slight deviations. Rainfall intensity
however, decreases towards the Voltaian basin. Mean monthly temperature ranges from high of
30oC in the dry season to about 26oC in the wet season. It is worthy of note that the relatively
higher altitude has moderating influence on the local temperature. Relative humidity ranges
between 75% and 80% (Kwahu South District Assembly, 2014). The study area lies within the
Semi-Deciduous forest zone. The vegetation is dense in terms of tree coverage with most trees
shedding off their leaves in the dry season. Trees of economic value like Odum, Wawa and Sepele
are found in the forest. The forest is made of three layers namely the upper, middle and lower
layers. A greater part of the natural vegetation has been altered due to anthropogenic activities. The
forests however, remains in their natural state in the five (5) reserve areas namely the Southern
Scarp Forest, Oworobong South, Abisu, Northern Scarp West, Oworobong South, Northern scarp
West and Oworobong North Forest reserves. Together, the reserves cover a total of 37, 070
hectares of land.
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CHAPTER FOUR
PESTICIDE CONTENT OF FALLOW LANDS
4.1 Background
The banks of the Afram arm of the Volta Lake are intensively cultivated for all kinds of crops,
owing to availability of water for irrigation. In particular, fruit and vegetable cultivation which is
much dependent on water availability is carried out all-year round. In order to increase yield and
maximize economic gains, there is over-reliance on agro-chemicals and in particular, pesticides.
Due to the persistence, bioaccumulation and health effects of the organochlorine pesticides, their
use has been discouraged in favour of the less persistent new generation pesticides like the
organophosphates and the synthetic pyrethroids. Wide range of pesticides belonging to these
groups is indiscriminately used to control insect pests. Although it has generally been assumed that
this new generation pesticides rapidly degrade in the environment, they are known to be more toxic
and reports indicate that a good number of them are sufficiently persistent to contaminate the
environment (Schimmel et al., 1983; Kjolholt, 1985; Barcello et al., 1990; Readman et al., 1992;
Ragnarsdottir, 2000). For instance Readman et al., (1992) found chlorpyrifos and parathion to be
stable and sufficiently persistent and hence contributed to the contamination of tropical marine
sediments. Bifenthrin has been established to have a half live of up to 8 months in soils (Extension
Toxicology Network, 1995); cypermethrin, up to 8 weeks (Extension Toxicology Network, 1996a)
and permethrin up to 43 days (Extension Toxicology Network, 1996b).
With the introduction of mechanized irrigation, farming goes on all-year round along the Afram
banks on crop and land rotation bases. Lands on the immediate banks of the river are keenly
competed for since irrigation efforts on such lands are reduced. Here, crop rotation is practiced
mostly as a way of maximizing the use of a piece of land, rather than cultural means of managing
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pests. Nevertheless the practice of land rotation also occurs. In the land rotation system however,
previously cultivated lands do not have enough fallow period. Typically, they are left uncultivated
temporarily for a maximum period of one vegetable growing season, i.e. 3 months. The lands are
therefore under pressure of cultivation all-year round. Since cultivation is heavily dependent on
agro-chemicals (Gordon and Amatekpor, 1999), it is pertinent to know the pesticide content; both
the organochlorines and the new generation pesticides, of the abandoned farmlands at the time of
their recultivation. The objective of this chapter therefore is to assess pesticide content of fallowed
fields prior to recultivation, as well as to determine if the presence of banned organochlorine
pesticides was due to current or historical inputs.
4.2 Materials and Method
4.2.1 Collection of Soil Samples
Cultivated lands that were temporarily left uncultivated for a maximum of three months were the
target for sampling (Plate 1). Sixty-six composite soil samples were taken from farmlands on the
banks of the Afram arm of the Volta Lake (four sampling sites: Odortorm, Kwahu Amanfrom,
Adawso and Kotoso – Fig. 3.1) between March to October 2012. The number of farmlands
sampled in each of these sites depended upon the willingness of the farmers to permit sampling on
their lands. At Odortom site, 14 samples were obtained; 17 from Kwahu Amanfrom; 19 from
Adawso and 16 from Kotoso. One composite sample consisting of nine sub-samples was collected
from each farm by random sampling within a grid according to British Crop Protection Council,
(2003). Three transects were established in each farm, with the middle transect approximately
equidistant from the other two. A margin of 1 to 2 metres was demarcated from the edges of each
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farm and this margin was not included in the sampled area. This was done to ensure all samples
were taken within the main farm area. With the help of hand trowel, samples were taken at three
point along each transect at a depth of 0 – 20 cm. The subsamples were placed in a thoroughly
cleaned plastic bucket, well mixed with the hand trowel and sieved through a 2 mm brass soil sieve
to separate liter, roots large stones and other large exogenous objects. Approximately 1 kg of the
sieved soil was then placed in a zip-locked plastic bag and labeled and tightly enclosed in another
polythene bag. One extra soil sample was collected in each community from a seemingly pristine
and uncultivated field and used as matrix blank sample. All samples were stored on ice transported
within 24 hours to the Ghana Standards Authority laboratory where they were subsequently stored
in a freezer until analysis. Enclosure of samples in the second plastic bags was a precautionary
measure to prevent samples from being soaked by melting ice blocks during transportation.
4.2.2 Chemicals and Reagents
All chemicals and reagents used in this study were of purest grade and are listed in Appendix I
4.2.3 Preparation of soil samples for pesticide extraction
Wet soils were used for extraction. This approach is more convenient and desirable because it
minimizes potential contamination and possible volatilization loses due to drying (Jayaraman,
2001; Muir & Sverko, 2006).
Soil samples from storage freezers were remove and allowed to thaw. The percentage of water in
each sample was determined by accurately weighing 10 g, drying at 105oC and reweighing to a
constant dry weight. A wet weight equivalent to 10 g dry sample was calculated for each sample
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after determining the percentage of water. Therefore, wet soils equivalent to 10 g of dry soil were
extracted per sample.
4.2.4 Extraction of pesticides from soil samples
Comminuted homogenous wet weight soil samples equivalent to 10 g dry samples were weighed
into 100 mL separating flasks and 10 mL acetonitrile added to each. The flasks were stoppered and
sonicated for 5 minutes in an ultrasonic bath, Decon FS400B (Plate 10a). A further 10 mL
acetonitrile was added to each flask, placed on a horizontal mechanical shaker and set to shake
continuously for 30 minutes at 300 motions per minute. The mixture in each flask was allowed to
stand for 10 minutes to separate layers, as demonstrated by plates 7a and 7b. The organic phase
(top layer) was decanted and dried over 5 g anhydrous magnesium sulphate through No. 1
Whatman filter paper. Ten mL aliquots of the filtrate were introduced into 50 mL round-bottomed
flasks and evaporated to 1 mL concentrate using Buchi rotary vacuum evaporator (Plate 11).
4.2.4.1 Clean-up of extracted samples
Two grammes of silica gel that has previously been activated at 1300C for 2 hours was carefully
packed into 10 mL polypropylene cartridge columns and capped with a 1 g anhydrous sodium
sulfate. This was conditioned with 10 mL acetonitrile. The 1 mL extract concentrates were loaded
onto cartridges by washing with 5 mL acetonitrile and the flow rate adjusted to 3 mL per minute,
with the help of visiprep vacuum manifolds. The eluates were collected into 50 mL pear-shaped
flasks. The cartridges were then further eluted with another portion of 5 mL acetonitrile. The
combined eluates were then evaporated just to dryness at 39oC and 77 mbarr pressure, using
vacuum evaporator (Buchi R.210). The concentrate was re-dissolved in 1 mL ethyl acetate and
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transferred into a 2 mL standard opening vial prior to analysis by gas chromatography equipped
with electron capture detector  (GC-ECD) for quntitation of organochlorine and synthetic
pyrethroid pesticides. And also chromatography equipped with pulse-flame photometric detector
(GC-PFPD) for organophosphorus pesticides quantitation. Until the GC determinations, the
extracts were stored frozen. On occasions when a final 1mL extract appeared a bit turbid, it was
introduced into a 15 mL centrifuge tube, frozen for one hour and centrifuged for 5 minutes at 3000
rpm (revolutions per minute) (Plate 10b). The top clear liquid is then taken into a 2 mL standard
vial, ready for gas chromatographic quantitation.
4.2.5 Preparation of stock pesticide mix standards solution
Pesticides stock solutions (1000 µg/mL) of individual standards were prepared by dissolving 25 mg
corrected by purity of the individual pesticide in 25 mL of ethyl acetate. 0.25 mL aliquot of each
prepared pesticide stock standard solutions was accurately pipetted into 25 mL volumetric flask
and the volume made up to 25 mL mark with ethyl acetate. This gives a concentration of 10 µg/mL
for each pesticide in the mixture. An aliquot of 2.5 mL of the prepared mixed standard solution was
pipetted into another 25 mL flask and again the volume made up to the 25 mL mark with ethyl
acetate to give a solution with a resultant concentration of 1 µg/mL. The mixed pesticides standards
solution for organochlorines contained 15 targeted organochlorine pesticides; that for
organophosphates contained 13 pesticides and that for synthetic pyrethroids contained 9 pesticides.
The list of pesticides is presented in Appendix I.
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4.2.6 Calibration of Instrument (Gas chromatograph)
From the stock standard mix solution, calibration standards of 0.005 µg/mL, 0.01 µg/mL, 0.02
µg/mL, 0.05 µg/mL, 0.1 µg/mL and 0.5 µg/mL were prepared to check the linearity of the
determination. 1.0 µL of each of the standard mix organochlorine pesticides (OCPs) and synthetic
pyrethroids pesticides (SPs) was injected into the injection port of the GC-ECD and the responses
recorded. (For OPs, 2.0 µL of each concentration was injected into the GC-PFPD injection port).
Calibration linear curves were constructed by employing Star Workstation software in-built to plot
the concentrations against their respective peak areas. Callibration curves had R2 = 0.995 – 0.998.
Recalibration curves were run with esch batch of 30 samples to ensure that correlation coefficient
was kept above 0.99.
4.2.7 Recovery test of extraction method
Recovery studies were undertaken to evaluate the efficiency of the extraction procedure used. Ten
grammes of soil matrix blank samples taken from the field were extracted as previously described
to determine the background concentration levels of any residual pesticide. An aliquot of 0.5 mL of
the standard stock solution (1µg/mL) was added to fresh 10 g of the soil matrix blank (This is
equivalent to a fortification or spiking level of 0.05 mg/kg) and taken through the entire extraction
process. These were then analysed by gas chromatograh to compare detected levels with the initial
concentration injected into samples prior to extraction. The recovery was done in duplicates, at
another fortification level of 0.01 mg/kg. The values, expressed in percentages were calculated
from chromatograms as follows:
C2 − C1
% Recovery = X 100
C
Where: C1 = Concentration (mg/kg) of pesticide residue in the matrix blank
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C2 = Concentration (mg/kg) of pesticide residue in the spiked matrix blank
C = Concentration (mg/kg) of pesticide added
The recoveries of the pesticides were within acceptable range of 70% - 120% for all of the
pesticides analysed.
4.2.8 Identification and Quantification of pesticide residues
Pesticide residues were identified using reference standards and relative retention time techniques.
Residue levels were determined by the external standard method by comparing the peak heights of
samples with the corresponding peak heights of the reference standards of known concentrations.
Measurements were carried out within the linear range of the detectors. Peak areas whose retention
times coincided with that of the standards were extrapolated on their corresponding calibration
curves to obtain concentrations.
4.2.9 Limit of detection (LOD) and Limit of quantitation (LOQ)
There are several conceptual approaches to the subject of LOD, each providing somewhat different
definition, and consequently the methodology used to calculate the LOD differ. LOD defined by
Chang (2011) as “the lowest amount of analyte in a sample which can be detected but not
necessarily quantitated as an exact value and LOQ as the lowest amount of analyte in a sample
which can be quantitatively determined with suitable precision and accuracy.
LOD for pesticides reported in this determination was based on the lowest analyte concentration
that could consistently and reliably yield 70% or more recovery from fortified samples (Scholtz &
Flory, 1999). Standard pesticide mix solutions were serially diluted and lowest concentration
whose recovery from fortified samples was greater than 70% and also gave a signal to noise ratio
of 3 was run 10 times and the standard deviation of the signals calculated. The standard deviation
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(SD) was multiplied by 3 to get the LOD (i.e. SD x 3 = LOD). The standard deviation for the LOD
determination was multiplied by 10 to get the LOQ (i.e SD x 10 = LOQ), following Scholtz and
Flory (1999). The LOD and LOQ for the determined pesticides in soil were set as 0.15µg/kg and
0.5µg/kg respectively. The standard pesticide mix solutions for LOD and LOQ determination
contained all target pesticides however, LOD and LOQ were determined for only certain individual
pesticides (markers) that represent the various pesticide groups. The markers for the various
pesticide groups are as follows: Organochlorine pesticides (γ-chlordane, p,p’-DDE and endosulfan
sulphate); Organophosphorus pesticides (diazinon, fenitrothion and parathion-ethyl); Synthetic
pyrethroids (bifenthrin, lambda-cyhalothrin and permethrin).
4.2.10 Gas Chromatographic quantification of extracted pesticides
The final extracts were analyzed for organochlorine and synthetic pyrethroid pesticides by Gas
Chromatograph- Varian CP-3800 (Varian Association Inc. USA) equipped with combiPal
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autosampler and Ni electron capture detector (ECD) (Plate 9 on page 94) that allowed the
detection of contaminants even at trace level concentrations (in the lower µ g/kg range)
from the matrix to which other detectors do not respond. The GC conditions used for the
analysis were capillary column coated with VF-5 (30 m + 10 m guard column x 0.25 mm i.d,
o o
0.25 µm film thickness). The injector and detector temperature were set at 270 C and 300 C
respectively. The oven temperature was programmed as follows: 70oC held for 2 min, ramp at
o o o o
25 C/min to 180 C, held for 1 min, and finally ramp at 5 C/min to 300 C. Nitrogen was used
as carrier gas at a flow rate of 1.0 mL/min a n d detector make-up gas of 29 mL/min. The
injection volume of the GC was 1.0 µ L. The total run time for a sample was 31.4 min.
Organophosphorus pesticides on the other hand were analyzed by Gas Chromatograph- Varian
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CP-3800 (Varian Association Inc. USA) also equipped with combiPal autosampler and
pulse flame photometric detector (PFPD) that allowed the detection of contaminants even at
trace level concentrations (in the lower µ g/g range). The GC conditions used for the analysis
were capillary column coated with VF-1701 (30 m x 0.25 mm i.d, 0.25 µ m film thickness).
o o
The injector and detector temperature were set at 270 C and 280 C respectively. The oven
o o o
temperature was programmed as follows:  70 C held for 2 min, ramp at 25 C/min to 200 C,
o o
held for 1 min, and finally ramp at 20 Cmin-1 to 250 C maintained for 3.3 min. Nitrogen was
used as carrier gas at a flow rate of 2.0 mL/min and detector make-up gases (17.0, 14.0 and
10.0 mL/min) for hydrogen, air-1 and air-2, respectively. The injection volume of the GC
organophosphorus pesticide determination was 2.0 µL. The total run time for a sample was
14 min. Each sample underwent duplicate analyses.
4.2.11 Quality Assurance and Control of Method
In Order to minimize potential contamination from laboratory air, as well as loses due to
volatilization, drying in the laboratory and freeze-drying were avoided. Further quality was
assured through the analysis of solvent and matrix blanks. For each batch of 20 samples analysed,
a solvent and matrix blanks were prepared. The reagents (ethyl acetate and acetonitrile) were of
high quality and were exposed to the same extraction procedures and subsequently run to check
that no interfering substances were present. No analytes were detected in the blanks. Recalibration
curves were run with each sample batch to ensure that correlation coefficient was kept above 0.99.
Strict cleaning procedures were adhered to viz: all glassware were washed with hot water and
detergents and copiously rinsed with distilled water. After drying, the glass wares were further
rinsed with acetone. Recoveries of spiked standards were all within acceptable range (70% -
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120%) for all pesticides.
4.2.12 Data Analysis
Detected pesticides were put into their pesticide groups and the mean concentration of each
pesticide was calculated based only on the number of samples in which quantifiable detects were
made. Incidence rate (IR) however was calculated as percentage frequency of each pesticide based
on the total number of samples. Standard deviations were computed to show the dispersion or
distribution of the data points around the mean.
Fi x 100
IR =
Ts
Where
IR = the incidence rate or percentage frequency of occurrence of an individual pesticide
Fi = frequency of detection of an individual pesticide i in all the soil samples and
Ts = total number of soil samples taken.
Percentage concentration of each pesticide in a pesticide group was also calculated and illustrated
as figures in the form of column and bar charts.
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4.3 Results
4.3.1 Overview of the results
Figure 4.1 illustrates the percentage composition of each detected pesticide in their various
pesticide groups. It was observed that some single pesticides contributed more than a third of the
entire concentration of their respective chemical/pesticide groups. For instance chlorpyrifos alone
accounted for 51% of the total organophosphorus concentration in the soil samples while
cypermethrin and p,p’-DDD contributed 37%  and 34%, respectively to pyrethroid and
organochlorine pesticide residue concentrations. The ten chemicals with the highest residues are
presented in Figure 4.2. Tables 4.1, 4.3 and 4.4 summarise the concentrations and frequencies of
organochlorine, synthetic pyrethroid and organophosphorus pesticides respectively in farmland
soils of the study area. On the average, the OCPs had the highest incident rate or frequency of
occurrence of 34.4% followed by the synthetic pyrethroids with 30% and the organophosphates
with 13%. The mean concentrations of residues in the pesticide groups however follow the order:
Synthetic pyrethroids > organophosphates > organochlorines. Table 4.5 enlists most of the
insecticides employed by the farmers in the study area to combat insect pests in fruits and
vegetable cultivation.
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Methoxychlor
p,p'-DDD
p,p'-DDT
Beta endosulfan
Endrin
Dieldrin
p,p'-DDE
α-endosulfan
γ-Chlordane
Aldrin
δ-HCH
γ-HCH
0 5 10 15 20 25 30 35
Percentage of total organochlorine concentration
Deltamethrin
Fenvalerate
Cypermethrin
Cyfluthrin
Permethrin
Lamda-cyhalothrin
Fenpropathrin
Bifenthrin
Allethrin
0 10 20 30 40
Percentage of total pyrethroid concentration
Profenofos
Chlorfenvinphos
Malathion
Chlorpyrifos
Dimethoate
Diazinon
Ethoprophos
Methamidophos
0 10 20 30 40 50 60
Percentage of total organophosphorus concentration
Fig. 4.1: Percentage total concentration of individual chemicals in each group of pesticide
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Chlorfenvinphos, 17
Bifenthrin, 17.4
p,p'-DDD, 41.9
Cypermethrin,
18.7
Dimethoate, 33.4
Chlorpyrifos, 21
Diazinon, 21 Fenvalerate, 27.27
Permethrin, 21.6
p,p'-DDE, 26.7
Fig. 4.2: Top ten chemicals with highest mean concentration (µg/kg) in soils from the study area
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4.3.2 Organochlorine pesticide residues in soils
The targeted OCPs, with the exception of heptachlor were encountered and the range of
concentration of detected pesticides was 0.47 – 91.0 µg/kg. Averagely, the pesticides had
frequency of occurrence of 33%. The most frequently encountered was p,p’-DDT, with incidence
rate of 88.3%. The least encountered was endosulfan sulphate, with frequency of occurrence of
1.7%.  Para, para-DDD (p,p’-DDD) registered the highest average concentration of 41.9 µg/kg,
followed by p,p’-DDE, γ-lindane, γ-chlordane and β-endosulfan with respective concentrations of
26.77, 14.85, 11.93 and 7.86 µg/kg. Endosulfan sulphate recorded both the lowest concentration
(0.47 µg/kg) and incidence (1.7%). It is also noted that of the quantified chemicals, p,p’-DDT, p,p’-
DDE and p,p’-DDD recorded levels above the USEPA maximum residual levels (Table 4.1). As
much as 38% of total samples analysed recorded p,p’-DDD residue levels above the USEPA
maximum residual levels while 10% and 3.8% were registered for p,p’-DDE and p,p’-DDT
respectively. The ratios of DDD/DDT and DDE/DDT were 6.7 and 4.2 respectively.
Concentrations of parent compounds and their metabolites are captured as ratios in Table 4.2. for
evaluation of degradation pathways and new inputs of pesticides.
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Table 4.1: Mean concentration of organochlorine pesticides in soils samples from farmlands
Mean ±SD Range % of samplesPesticide USEPA MRL(µg/kg) (µg/kg) IR (%) exceedingUSEPA MRL ( µg /kg)
β-HCH 3.15 ±1.5 2.1-9.5 33.3 0 30.0
γ-HCH 14.85 ±5.3 0.5-28.5 60.0 0 40.0
δ-HCH 6.51 ± 1.2 3.7-8.2 33.3 0 30.0
Heptachlor nd - 30.0
Aldrin 1.72 ± 0.3 1.3-2.5 33.3 0 40.0
Dieldrin 1.39 ± 0.2 1.1-1.6 33.3 0 20.0
Endrin 4.68 ± 0.2 1.2-5.2 30.0 0 40.0
γ-Chlordane 11.93 ± 9.5 4.6-39.1 33.3 0 250.0
α-endosulfan 2.48 ±0.4 1.8-3.4 33.3 0 50.0
Beta endosulfan 7.86 ± 2.2 4.4-10.4 10.0 0 40.0
Endosulfan sulfate 0.47 0.47 1.7 0 40.0
p,p'-DDE 26.77 ±9.4 12.7-47.1 33.3 10 40.0
p,p'-DDT 6.3 ±14.6 0.75-91.0 88.3 3.8 50.0
p,p'-DDD 41.89 ± 29.1 1.6-67.0 45.0 38 40.0
Methoxychlor 6.38 ±1.2 5.4-9.0 13.3 0 50.0
Grand mean 9.74
Load 136.36
N = 66 nd =  not detected
IR = Incidence rate
Grand mean = Mean of the concentrations of all organochlorine pesticides quantified in the analysis
Load = Total of the means of all OCP residues in soil samples
IR = Percentage frequency of occurrence of an individual pesticide in total sample
Table 4.2: Ratios of metabolites to parent compounds in soils from farmlands
Pesticides Ratio value
p,p’-DDE/p,p’-DDT 4.24
p,p’-DDD/p,p’-DDT 6.65
p,p’-DDD/p,p’-DDE 1.57
Endrin/Dieldrin 3.37
Endrin/Aldrin 2.72
Dieldrin/Aldrin 0.81
β-HCH/ γ-HCH 0.21
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4.3.3 Synthetic pyrethroid pesticide residues in farmland soils
Nine synthetic pyrethroid pesticide residues were targeted in this study and all of them were
detected and quantified in the analysed soil samples. The incidence rate ranged from 10% for
allethrin to 78.3% for cypermethrin (Table 4.3). The general concentration ranged from 0.50 µg/kg
for permethrin to 139.30 µg/kg for cypermethrin. The mean concentration range however was 1.36
µg/kg – 27.27 µg/kg. Fenvalerate recorded the highest mean concentration of 27.27 µg/kg followed
by permethrin (21.55 µg/kg) and then cypermethrin (18.70 µg/kg). Allethrin mean detect was the
least; 2.20 µg/kg. Residues of three pesticides recorded levels higher than the USEPA MRL and
these are fenvalerate, cypermethrin and permethrin, with respective percentages of 10, 10 and 3.3
of total samples analysed exceeding the maximum residue limit (Table 4.3).
Table 4.3: Mean concentration of synthetic pyrethroid pesticides in soils sample from farmlands
Pesticide Mean ±SD Range IR (%) % of samples USEPA MRL
(µg/kg) (µg/kg) Exceeding (µg /kg)
USEPA MRL
Allethrin 2.20 ± 1.5 0.78-3.30 10.0 0 10.00
Bifenthrin 17.40 ±2.6 12.00-21.10 30.0 0 40.00
Fenpropathrin 8.93 ±1.1 1.0-50.60 28.3 0 20.00
Lamda-cyhalothrin 3.67 ±0.4 3.20-4.00 18.3 0 20.00
Permethrin 21.55 ±32.6 0.5-95.00 15.0 3.3 10.00
Cyfluthrin 9.11 ±5.1 0.50-18.00 28.3 0 150.00
Cypermethrin 18.70 ±30.2 0.50-139.30 78.3 10.0 50.00
Fenvalerate 27.27 ±27.4 1.95-76.00 28.3 10.0 30.00
Deltamethrin 1.36 ±1.4 0.51-6.00 38.3 0 50.00
Grand mean 12.24
Load 110.16
N = 66; Grand mean = Mean of the concentrations of all pyrethroid pesticides quantified
Load = Total of the means of all OCP residues in soil samples
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4.3.4 Organophosphorus pesticide residues in farmland soils
The presence of all the target organophosphorus pesticides was registered except pirimiphos-methy
(Table 4.4). The concentration range of the detected residues was 1.0 – 58.5 µg/kg. The least
concentration of 1.0 µg/kg was recorded for ethoprophos, fonofos, malathion, fenitrothion and
profenofos, while the highest concentration of 58.5 µg/kg was registered for chlorfenvinphos. The
frequencies of occurrence here was very low, with a mean of 13% and a range of 3.0 - 63.3%.
Chlorpyrifos had the highest rate of occurrence while parathion had the lowest. Here too, the levels
of four pesticides, namely chlorpyrifos, dimethoate, chlorfenvinphos and methamidophos exceeded
the USEPA MRL in 16.7%, 5.0%, 1.6% and 1.6% of total samples analysed.
Table 4.4: average concentration of organophosphorus pesticides in surface soils samples
from farmlands
Pesticide Mean ±SD Range IR (%) % of samples USEPA MRL
(µg/kg) (µg/kg) Exceeding (mg/kg)
USEPA MRL
Methamidophos 11.75 ±6.8 4.00-28.65 33.0 1.6 0.03
Ethoprophos 5.40 ±2.3 1.00-7.48 9.1 0 0.05
Phorate 1.71 ±0.4 1.28-2.00 4.5 0 0.05
Diazinon 20.50± 8.9 7.12-25.00 6.1 0 0.03
Fonofos 1.33 ±0.5 1.00-2.00 4.5 0 0.05
Dimethoate 33.42 ±24.0 3.10-57.00 7.6 5 0.03
Pirimiphos-methyl Nd - - 0.03
Chlorpyrifos 20.70 ±13.0 3.12-46.00 63.3 16.7 0.03
Malathion 10.0 ±12.9 1.00-31.21 7.6 0 0.05
Fenitrothion 2.66 ±1.6 1.00-4.50 9.1 0 0.05
Parathion 2.50 ±0.7 2.00-3.00 3.0 0 0.04
Chlorfenvinphos 17.24 ±2.2 1.10-58.50 6.1 1.6 0.05
Profenofos 8.00 ±6.3 1.0-15.12 9.1 0 0.05
Grand mean 11.02
Load 132.24
N = 66 nd =  not detected
Grand mean = Mean of the concentrations of all OPs quantified in the analysis
Load = Total of the means of all OCP residues in soil sample
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Table 4.5: Inventory of some insecticides used in the study area
Trade Name Active ingredient(s) Function
Cydim EC Dimethoate Systemic and contact insecticide for vegetables,
Cypermethrin Soybeans, pineapple and ornamental plants
Cydim Super EC Insecticide for the control of aphids, caterpillars,
Cypermethrin
whitefly, grasshoppers, bollworms in vegetables and
Dimethoate
cotton
Plan DEC 25 Contact insecticide for the general treatment of
Deltamethrin
of insects of various categories
Agricombi Fenitrothion (30%) Broad-spectrum insecticide for treating caterpillars, mites
Fenvalerate (10%) and aphids
Akate Bifenthrin Broad-spectrum insecticides used for all crops
Decis EC 12.5 Contact and ingestion pesticide use to treat vegetables
Deltamethrin against caterpillars, thrips, cutworms, leafworms and
bollworms.
Thiodan Endosulfan For the control of bollworms
Akape (Anty Broad-spectrum systemic insecticide used on vegetables,
Imidacloprid
Ataa) fruits cereals and ornamentals
Acetar star EC Bifenthrin Contact and stomach insecticide for the contrl of
Acetamiprid whiteflies, aphids, bollworms on vegetables & fruits.
Attack Emmectin benzoate Non-systemic insecticide that controls cabbage moths,
aphids, whitefly, caterpillars and leaf miners.
Sumitex 40EC Dimethoate Insecticide for the control of mealybugs, mites, thrips,
and larvae borers in vegetables and pineapples
Sumitox Fenvalerate Broad spectrum insecticide with contact and stomach
action against sucking and boring pests
Actellic 50 EC Pirimiphos-methyl For the control of aphids
Confidor SL 200 Imidacloprid For the control of aphids, thrips, whitefly and termites
Ceres (cerox) Dimethoate Broad spectrum insecticide
Alphacp 10 SC Alpha-cypermethrin Insecticide for the control of insect pests in vegetables
and fruits.
Conquer super Lambda-cyhalothrin Insecticide for the control of insect pest in vegetables and
2.5EC pulses
Conpyrifos Chlorpyrifos-ethyl Insecticide for the control of borers in vegetables, cereals
48EC and for public health purposes
Contihalothrin Lambda-cyhalothrin Insecticide for the control of insect pest in vegetables and
2.5EC pulses
Fastrack 10SC Alpha-cypermethrin Insecticide for the control of insect pests in vegetables
and fruits crops
Perfekthion Dimethoate Insecticide for the control of mealybugs, mites, thrips,
and larvae borers in vegetables and pineapples
Vector 30%WP Beta-cyfluthrin and Insecticide for the control of insect pests in vegetables
Imidacloprid
Sumicombi -Fenitrothion Insecticide for the control of pests on vegetables and for
-Fenvalerate public health
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4.4 Discussions
4.4.1 Organochlorine pesticide Residues in soil samples
The single highest Organochlorine pesticide (OCP) concentrations measured in the samples were
recorded for p,p’-DDT (91.0 µg/kg), followed by p,p’-DDD (67.0 µg/kg) and p,p’-DDE (47.1
µg/kg) as can be observed from their respective concentration ranges in Table 4.1. Except for the
DDTs (p,p’-DDT, p,p’-DDE and p,p’-DDD), the level of other OCPs were low and below the
USEPA maximum residue levels. Apart from γ-HCH whose frequency of occurrence was 60%, the
DDTs were the most frequently encountered with p,p’-DDT detected and quantified in 88.3% of
the samples. Wang et al., (2006) recorded 8.55 µg/kg, 22.78 µg/kg and 11.50 µg/kg for p,p’-DDT,
p,p’-DDE and p,p’-DDD respectively in a paddy agricultural region along Taihu Lake in China
while Manz et al., (2001) also recorded up to 90 µg/kg, 100 µg/kg and 20 µg/kg for the respective
compounds in agricultural fields in Germany. Values from this study are higher than what Wang et
al reported but far lower than recorded figures by Manz et al., (2001). Whereas the order of
decreasing magnitude of the residue concentration in this study was p,p’-DDD > p,p’-DDE > p,p’-
DDT, that in Wang et al., (2006) and Manz et al., (2001) were p,p’-DDE > p,p’-DDD > p,p’-DDT
and p,p’- DDE > p,p’-DDT > p,p’-DDD respectively.
For the lindanes, β, γ and δ isomers were quantified. Alpha-HCH was not recorded in any sample.
Gamma-HCH was the most frequently encountered (60% incidence rate) and also had the highest
mean concentration (14.85 µg/kg), followed by δ-HCH (6.51 µg/kg) and then β-HCH (3.15 µg/kg).
Relative to the DDTs, the lindanes and the drins (aldrin, dieldrin and endrin) recorded lower
residue levels and incidence rates. The mean concentration of aldrin (1.72 µg/kg), the parent
compound, was higher than that of dieldrin (1.39 µg/kg) but lower than the endrin concentration
(4.68 µg/kg).
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Of the endosulfan group, the parent, β-endosulfan had the highest mean concentration (7.86 µg/kg)
but α-endosulfan was more frequently encountered. The metabolite, endosulfan sulfate was
virtually absent, being recorded in only one sample. On the whole, the concentrations of OCPs in
the soils were in the following order: DDTs > HCHs > endosulfans > drins.
4.4.2 Degradation pathways and evaluation of input of new organochlorine pesticides
The predominance of the DDTs, both in concentration and incidence rate on the surface suggests
possible fresh introduction of technical DDT. According to Manz et al., (2001), studying the
isomeric ratio and metabolite/parent compound ratios enables past and present pollutant emission
sources to be distinguished. If there was no other pollution source, the metabolite/parent compound
ratio generally increases with time. Thus the ratio of metabolites to parent compounds could be
used as a rough estimate of the period of their application as well as to infer pollution sources
(Karina et al., 2003; Gao et al., 2005).
P,p’-DDT  is easily metabolized into the more stable and persistent isomers p,p’-DDE and p,p’-
DDD in the environment (Bossi et al., 1992). In this study, both metabolites were present in
appreciable quantities, though p,p’-DDD recorded a higher concentration. The degradation of DDT
in the environment could be explained as a result of anaerobic process of reductive dechlorination
to DDD and dehydrochlorination to DDE respectively (Quensen et al.,1998; Yao et al., 2006).
Generally, a value of metabolite:parent compound greater than 1.0 indicates aged or historical use
of pesticide while a value less than 1.0 indicates new pesticide application (Karina et al., 2003;
Zhang et al., 2006). The ratios of p,p’-DDE: p,p’-DDT, p,p’-DDD: p,p’-DDT and endrin:dieldrin
as well as endrin:aldrin were all greater than 1.0 (Table 4.2), indicating no new inputs of these
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pesticides (DDT, aldrin and endrin) in the field. However, the ratio of dieldrin:aldrin was less than
1.0 (0.8), suggesting there might be a current input of aldrin pesticide, to a lesser extent. The
degradation pathway of DDT to DDD could be direct and indirect. The indirect path was from
DDT to DDE, then further to DDD (Wenzel et al., 2002). The ratios of DDD:DDE, DDD:DDT
and DDE:DDT were employed to deduce the possible dechlorination pathway (Wenzel et al.,
2002) in the farmland soils along the Afram bank in the current study. It was possible that DDT to
DDD was the main degradation route and as a result, the ratio sequence was DDD:DDT >
DDE:DDT > DDD: DDE (Table 4.2).
Technical Lindane contains 60%-70% α-HCH, 5%-12% β-HCH, 10%-12% γ-HCH, 6%-10% δ-
HCH and 3%-4%  ε-HCH.  If technical lindane is the pollution source, the ratio of α-HCH to γ-
HCH should be 5.3-6.3 (Fu et al., 2001). However, if lindane (γ-HCH) is the pollution source, the
ratio of β-HCH/ γ-HCH increases in the soil during the degradation process (Wang et al., 2006)
and a value of 1.0 or greater will indicate aged or historical use of lindane (pure  γ-HCH) while a
value less than 1.0 will imply current use. From Table 4.2, β-HCH/ γ-HCH value is less than 1
(0.21), implying the source of lindane in the farmland soils might be due to current input of
Lindane (γ-HCH) other than technical lindane. This view is reinforced by the fact that there was no
detection of α-HCH; and γ-HCH concentration was far higher than the other isomers.
Technical endosulfan is a mixture of two isomers: α-endosulfan (64-67%) and β-endosulfan (29-
32%) (British Crop Protection Council, 2003). Their degradation product is endosulfan sulfate, the
presence of which indicates the residue might have originated from historical use of endosulfan
(Dem et al., 2007). The virtual absence of endosulfan sulfate in the soil samples from this study
therefore suggests the detected residues came from recent applications. It is interesting to note that
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the, DDTs, aldrin, dieldrin and endrins whose usage has been banned in the country have also been
found, (per their metabolite-parent compound ratios in this study) not to be of current use. It should
also be noted that even though the presence of the DDTs in the fallow lands does not suggest
current inputs, their concentrations levels are all above the MRLs of the USEPA. They therefore
still pose as sources of contaminants to crops that will subsequently be cultivated on those lands
(even without further application of pesticides) and health hazard in food chains. Lindane and
endosulfan are the only OCPs whose presence in the soil suggests that they are still being used.
Whereas the source of endosulfan may come from the use of thiodan and thionex to control
bollworms in fruits, vegetables and cereal crops, the source of Lindane cannot be easily traced
since it has not been listed in the inventory of pesticides used in the study area (Table 4.5); neither
was any pesticide with Lindane as an active ingredient chanced upon by personal observation.
Lindane being a popular and effective broad-spectrum insecticide was probably one of those illegal
pesticides that were covertly peddled from house to house to farmers, knowing very well that their
use has been banned.   Heptachlor, a pesticide whose use has not only been banned, but listed by
the EPA as completely not in use in the country has also not been detected in this study.
4.4.3 Residues of Pyrethroid pesticides
All the target pyrethroid pesticides (SPs) were found in soil samples. Cypermethrin was found in
78.3% of the samples, deltamethrin in 38.3%, befenthrin in 30.0%, fenvalerate, cyfluthrin and
fenpropathrin in 28.3%. Permethrin was measured in 18.3% and allethrin in only 10% of the total
of 66 soil samples. Generally, pyrethroids are known to be the least persistent among the
pesticides. The detection and quantification of all the target pesticides in samples therefore
underscore the high dependence and suggests indiscriminate use of this group of pesticides in
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agricultural activities in the study area. As indicated in Table 4.3, pyrethroids are mostly broad
spectrum insecticides effective against a wide range of insect pests of the orders Coleoptera,
Diptera, Hemiptera, Hymenoptera, Lepidoptera, Orthoptera and Thysanoptera (Thatheyus &
Selvan, 2013). Their low mammalian toxicity but high arthropod toxicity makes them very
effective and therefore popular and desirable in the treatment of all kinds of insect pests. As can be
inferred from Table 4.3, they constitute the main insecticides found from the study. Indeed
information from farmers in the study area indicate that although they are aware of the requisite pre
harvest interval (PHI)  (a period prior to harvesting, during which there should be no pesticide
application to food crops), yet most of them still spray their crops very close to harvest time in
order to increase their aesthetic and economic values.
The general concentration range of detected pyrethroids in the soil samples was 0.25 µg/kg –
139.3µg/kg. Even though the mean of each of the three highest pesticides measured follow the
order fenvalerate > permethrin > cypermethrin, the highest concentrations measured in single
samples follow the order cypermethrin > permethrin > fenvalerate (Table 4.3). The percentage
contribution of each pesticide to the total/cummulative pyrethroid concentration in the area
however is of the order cypermethrin > fenvalerate > bifenthrin (Figure 4.1). It is also worthy of
note that the levels of some of the pesticides, mainly cypermethrin, permethrin and fenvalerate in
some of the samples exceeded the maximum residue levels (MRL) set by USEPA. Of the three
pesticide groups under study, pyrethroids registered the highest total average concentration of
12.24 µg/kg, followed by the organophosphates (11.02 µg/kg), and then the organochlorine
pesticides (9.74 µg/kg). This is interesting since OCPs are known to be most persistent, followed
by the OPs. This information is indicative of the fact that there is more reliance on SPs for pest
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control relative to the other two and this is corroborated by facts gathered through interviews and
observations from the field (Table 4.5).
Pyrethroids are largely insecticides and are normally sprayed on crops, rather than on soils, to
control pests. Considering this fact, and also that they are supposed to be readily degradable, within
few days to weeks of their application, there is cause for concern noting that they still have some
appreciable levels in soils of farmlands that have been left temporarily uncultivated for at least
three months. This could be due to abuse of the chemicals, mostly over dosage, as discovered by
Dinham et al., (2003) with the resultant high residual concentration irrespective of their short half
lives. This finding may underscore some level of environmental persistence of this group of
pesticides that may have been underestimated and must be re-evaluated on the basis of the
individual chemicals. Indeed, as pointed by some authors (Lee et al., 2003; ATSDR, 2003;
Thatheyus & Selvam, 2013), pyrethroids can persist in soils for few hours to some few years,
depending on  a number of factors such as the type of pyrethroids in question, soil type, climate,
species of microbes present in the soil and their  population size. Whereas allethrin and resmethrin
are known to be among the fastest degrading pyrethroids; taking few minutes to hours after
application to degrade, others like permethrin, cyfluthrin, bifenthrin, fenvalerate and cypermethrin
have given indication- though uncertain- of their persistence in soils up to 5 years, 9 months, 8
months, 3 months and 2 months respectively (Pyrethroids and pyrethrins, 2013).
4.4.4 Residues of Organophosphorus pesticides
Chlorpyrifos and methamidophos were the most frequently detected with incidence rates of 63.3%
and 33.0% respectively. The rest had frequency rates below 10%. Even though Pirimiphos-methyl
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was listed among pesticides found in use in the study area (Table 4.5), it was not detected in any of
the 66 samples analysed. The presence of dimethoate, fenitrothion and chlorpyrifos in soil samples
agree with organophosphorus pesticides listed as being in use during reconnaissance survey. The
levels of three of them, dimethoate, chlorpyrifos and chlorfenvinphos exceeded the MRLs while
the level of methamidophos in some samples (38.65 µg/kg) almost equaled MRL of the USEPA.
The concentrations recorded in this study were generally higher than those reported by Kumari et
al., (2008) and Bhupander et al., (2011) from northern India and Delhi Region in India
respectively. Reported mean concentrations for parathion by Velasco et al., (2014), from
agricultural soils in Rio Verde Region of Mexico were however much higher (25.2 µg/kg - 47.48
µg/kg) than what is found in this study. Unlike pyrethroids, OPs are very toxic to humans as well
as other organisms and their presence in the environment has been associated with many health
consequences (Ragnarsdottir, 2000). Even though they are also known to be less persistent in the
environment, their persistence is higher relative to the SPs. Species like chlorpyrifos and parathion,
and indeed many more OPs, are known to persist in the environment for up to more than 1 year
(Ragnarsdottir, 2000; Kazemi et al., 2012b).
The findings from this study established the facts that 37 out of 38 (97.4%) targeted pesticides for
investigation in soils of temporally abandoned (fallowed) farmlands were detected and quantified.
Ninety-four percent of the targeted OCPs were detected in 88.3% of the samples; 100% of targeted
synthetic pyrethroids were detected in 78.3% of the samples while 69% of the organophosphates
were detected in 63.3% of all the samples. Of all the detected pesticides, 9 (p,p’-DDT, p,p’-DDE,
p,p’-DDD, permethrin, cypermethrin, fenvalerate, dimethoate, chlorpyrifos and chlorfenvinphos),
representing 24% exceeded the USEPA maximum residue limit. The presence of 8 banned
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pesticides, namely: aldrin, dieldrin, endrin, γ-HCH, p,p’-DDT, heptachlor, parathion and
methamidophos was also identified and among them, the presence of only γ-HCH have been
assessed to be due to current input. It can, therefore, be concluded that the residual load of
pesticides on fallowed cultivated lands along the banks of the Afram arm of the Volta Lake are
heavy enough to potentially contaminate new crops that will be cultivated on them, even without
further application of insecticides.
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1a
1b
Plate 1: Fallow lands
1a: Previously cultivated land temporarily abandoned
1b: Sampling on fallowed farmland freshly ploughed for re-cultivation
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2a
2b
2c
Plate 2: Crop samples
2a: Samples of Citrullus vulgaris (watermelon)
2b:  Samples of Allium cepa (red onion)
2c: Sample of Capsicum annum (Chili pepper)
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3a 3b
3d
3c
3f
3e
Plate 3: Samples of aquatic biota
3a: Samples of Bagrus bayad
3b:  Samples of Tilapia zilli
3c: Samples of Chrysicththys nigrodigitatus
3d: Oreochromis niloticus sample being prepared for filleting
3e:  Harvested sample of Ceratophyllum demersum
3f: Nymphaea lotus sample
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4a
4b
4c
Plate 4:  Drawdown farming
4a: Previously submerged farm showing relics of dead crop plants after recession
4b Preparation of drawdown area for cultivation
4c Cultivation of pepper along immediate bank of Afram River (draw-down farming)
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5a
5b
5c
Plate 5: large scale farms upland the drawdown area
5a: Irrigation of watermelon plantation
5b: Example of onion plantation
5c: A typical machine for pumping water to irrigate farms upland
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6a 6b
6c 6d
Plate 6: Tissue samples of some fishes
6a: Orechromis niloticus showing position of filleting
6b: Muscle tissue taken from Orechromis niloticus
6c: Liver tissue taken from Bagrus bayad
6d: Gill tissue taken from Bagrus bayad
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7a
7b
7d
7c 7e
7f
Plate7: Some stages in the extraction of soil and fish matrices
7a: Extraction of pesticides from soil samples using mechanical shaker
7b: Separation of pesticide-laden organic layer (top layer) from soil matrix
7c: Organic layer containing pesticide extract from Bagrus bayad muscle tissue prior to clean-up
7d: Organic layer containing pesticide extract from liver tissue of B. bayad prior to clean-up
(Note colour of extract due to presence of pigments and other interfering materials)
7e & 7f: Extracts of B. bayad muscle and liver tissues after going through silica SPE clean-up.
(Note colour of liver extract in arrowed flask 7d and the corresponding clear extract in
arrowed flask 7f after SPE clean-up)
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8a
8b 8c
8d 8e
Plate  8: Some stages in the food crop extraction process
8a: Use of vortex mixer to homogenize watermelon sample
8b & 8c:  Homogenised pepper (8b) and onion (8c) samples after being centrifugated. Note how
clearly the supernatants are separated
8d: Fruits and vegetable supernatants from centrifuge being loaded unto Envi-Carb/LC-NH2
SPE Cartridges for clean-up on visiprep vacuum manifold
8e: Silica SPE cartridges with entrapped co-extractives (the greenish layers) after clean-up
process
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Plate 9: Gas chromatography Varian CP-3800 used for pesticide residue quantification.
This GC is equipped with Electron Capture Detector (ECD), Flame Ionisation Detector (FID) and Pulse
Flame Photometric Detector (PFPD). Designed with a CombiPal autosampler and 1177 type injector, it is
capable of running both split/splitless injections. The ECD component quantified organochlorine and
synthetic pyrethroid pesticides in samples while the PFPD quantified organophosphate pesticides. Arrow
points to autosampler loaded with sample vials.
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10a
10b
Plate 10: Decon sonicator and Centrifuge
Plate 10a: Decon FS400B sonicator. It is a waterbath that can be set to ultrasonically shake soil and
sediment samples in organic solvent prior to extraction by electronic shaker (plate 7a).
Plate 10b: Centrifuge employed to ease phase separation
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Plate 11: Buchi rotary vacuum evaporator used in the analyses
Buchi Rotovapor R.210 with recirculation chiller. It is used to evaporate organic
solvent from the pesticide residues after solid phase extraction. Arrow points to
recirculation chiller.
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CHAPTER FIVE
PESTICIDE CONTENT AND HEALTH RISK ASSESSMENT
OF WATERMELON, PEPPER AND ONION FROM THE
CULTIVATED BANKS OF AFRAM ARM
OF THE VOLTA LAKE
5.1 Background
The varieties of crops cultivated along the Afram arm of the Volta Lake may, out of convenience,
be put into two categories, based on their demand for agro-chemical input for increased yield.
Crops like cassava, maize, sweet potato and peanuts are mainly for subsistence and do not require
much input of agro-chemicals, especially insecticides. Their cultivation virtually does not require
irrigation and application of insecticides. Others like onions, water melon, pepper and okra are
intensively cultivated for cash and highly dependent on regular irrigation and insecticide
application for good yield. It is the latter group of crops that are the target for investigation for
multiresidue analysis of pesticides. This group of crops is short-maturing, taking on the average,
three months to mature. Thus, it is possible to have at least three cultivation seasons in a year. In
order to make maximum economic gain, most farmers continuously cultivate fruits and vegetables
throughout the year.
The intensity of farming has implications for pest persistence and hence the need to intensify
insecticide application, sometimes including cocktail applications and experimentation with
unfamiliar or inappropriate pesticides. Continuous application of insecticides may not only tend to
produce resistant species of insect pests but may also contaminate crops by their residual
concentrations. In order to produce crops of aesthetic quality (that is so much desired by
consumers), pesticide application sometimes goes on through to the harvest time, sometimes
ignoring the required pre-harvest interval (period prior to harvesting when crops are mandatorily
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not required to be treated with pesticides to prevent contamination). The aim of this chapter is
therefore to assess the presence and residual level of a spectrum of insecticides in water melon,
onions and chili pepper cultivated along the banks of the Afram arm of the Volta Lake and their
associated health hazard.
5.2 Materials and method
5.2.1 Sampling of fruit and vegetable samples
Large quantities of water melon fruits, onions and fresh chili peppers were bought from the
sampling sites in the field (Fig. 3.1) from farmers at the time when farmers were harvesting for sale
and crops were ready for immediate consumption. Plate 2 shows some of the samples. The
sampling was done at different times between January – November, 2013 to ensure diversity and
consistency with Codex sampling method (FAO/WHO, 2000). The onion and pepper samples after
purchase were kept on ice. All samples were transported to the pesticide laboratory at the Ghana
Standards Authority in Accra and were immediately processed and stored in deep freezers until
extraction is done within 24 hours.
5.2.2 Chemicals and Reagents
All the chemicals and reagents used are listed in Appendix I
5.2.3 Processing of samples for pesticide extraction
Each of the onion and pepper samples from all the sampling sites were put together and thoroughly
mixed in the laboratory. Fifty gramme (50 g) composite portions were separately weighed,
thoroughly washed in two changes of distilled water and homogenized in a warring blender food
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processor. Water melons samples weighed between 3 kg to 7 kg per fruit. Each fruit was
thoroughly washed with distilled water and sliced into six cones. The edible part of a number of
cones weighing at least 1kg was homogenized. The homogenized samples were then put into
plastic bags and kept in deep freezer until extraction was done within a maximum of 24 hours.
5.2.4 Extraction and clean-up of pesticides from samples
Annastassiade et al., (2003) developed a novel method for extraction of pesticide multiresidues in
food commodities and described it as Quick, Easy, Cheap, Effective Rugged and Safe
(QuEChERS). It is an effective extraction and cleanup approach for the analysis of diverse analyte
residues in food matrices that requires minimum input of chemicals and reagents (cost), time and
expensive equipment to accomplish. So far, it has achieved excellent results and its application has
been extended to analyses in other fields including pharmaceuticals and veterinary (Wilkowska and
Biziuk, 2010). Over the years, the original method has been modified for improved efficiency and
also adapted to achieve specific results. Takatori et al., (2009) described rapid and easy
multiresidue methods for the determination of pesticide residues in various foods matrices. In this
study, their method (Takatori et al., 2009) was modified for extraction and clean-up of pesticides in
the fruit and vegetable samples.
Frozen homogenized samples were allowed to thaw. Ten gramme portions of samples were put
into 50 mL polypropylene tubes and 10 mL acetonitrile added. The content of the tube was
homogenized by vortex mixer (Thermolyne-Maxi Mix-Plus) (Plate 8a) at high speed for 1 minute.
Four grammes of anhydrous magnesium sulphate and 1g of sodium chloride were then added and
vigorously shaken for another minute. The mixture was then centrifuged for 5 minutes and 4 mL
supernatant organic layer taken. Supelclean Envi-Carb/LC-NH2 SPE cartridge (500mg/500mg, 6ml
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size) was conditioned with 10 mL acetonitrile and allowed to run down but the cartridge was not
allowed to dry. The 4 mL supernatant from the centrifuge process was then loaded onto the
conditioned solid phase extraction cartridge. This was then eluted with two portions of 5 mL
acetonitrile into a pear-shaped 50mL flask, using a 12 port visiprep vacuum manifold. The elution
was done at the rate of 3 drops per second. Plate 8 illustrates some stages of the extraction process.
The eluate was evaporated to dryness using Buchi rotary vacuum evaporator (Buchi Rotovapor
R.210) at 40oC and 77 mbar with recirculation chiller, (Buchi, B-740). The concentrate was re-
dissolved in 2 mL ethyl acetate and transferred into a 2mL standard opening vial for Gas
chromatogram equipped with electron capture detector (GC-ECD) and pulse flame photometric
detector (GC-PFPD) analyses.
5.2.5 Recovery test of extraction method
Duplicate of samples that have already been analysed were spiked with 0.05 mg/kg of standard
pesticide mixtures and subjected to the same extraction process in order to determine recovery
efficiency of the extraction method. The recovery was done in duplicates, at another fortification
level of 0.01mg/kg. The values, expressed in percentages were calculated from chromatograms as
follows:
C2 − C1
% Recovery = X 100
C
Where: C1 = Concentration (mg/kg) of pesticide residue in the matrix blank
C2 = Concentration (mg/kg) of pesticide residue in the spiked matrix
C = Concentration (mg/kg) of pesticide added
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The recoveries of the pesticides were within acceptable range of 70% - 120% for the pesticides
analysed. Reagent or procedural blanks were also extracted similarly as the test samples and found
to be devoid of any interfering agents. Calibration of gas chromatogram, quantification of pesticide
residues and limits of detection and quantification as well as calibration standards were all set as
described in chapter four. The limit of detection (LOD) and limit of quantification (LOQ) of the
GC for all the pesticides in fruits and vegetables were 0.15 µg/kg and 0.5 µg/kg respectively,
5.2.6 Gas Chromatographic quantification of extracted pesticides
The final extracts were analyzed for organochlorine and synthetic pyrethroid pesticides by Gas
Chromatograph- Varian CP-3800 (Varian Association Inc. USA) equipped with combiPal
63
autosampler and Ni electron capture detector (ECD). The GC conditions used for the analysis
were capillary column coated with VF-5ms (30 m + 10 m guard column x 0.25 mm i.d, 0.25 µ
o
m film thickness). The injector and detector temperature were set at 270°C and 300 C
respectively. The oven temperature was programmed as follows: 70°C held for 2 min, ramp at
25°C /min to 180°C, held for 1 min, and finally ramp at 5 °C/min to 300°C. Nitrogen was used
as carrier gas at a flow rate of 1.0 mL/min a n d detector make-up gas of 29 mL/min. The
injection volume of the GC was 1.0 µ L. The total run time for a sample was 31.4 min.
Organophosphorus pesticides on the other hand were analyzed by Gas Chromatograph- Varian
CP-3800 (Varian Association Inc. USA) also equipped with combiPal autosampler and
pulse flame photometric detector (PFPD) that allowed the detection of contaminants even at
trace level concentrations (in the lower µ g/g range) from the matrix to which other detectors
do not respond. The GC conditions used for the analysis were capillary column coated with
VF-1701 (30 m x 0.25 mm i.d, 0.25 µ m film thickness). The injector and detector temperature
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o o
were set at 270 C and 280 C respectively. The oven temperature was programmed as follows:
o 1 o
70 C held for 2 min, ramp at 25oCmin- to 200 C, held for 1 min, and finally ramp at 20°C
o
/min to 250 C maintained for 3.3 min. Nitrogen was used as carrier gas at a flow rate of 2.0
mL/min and detector make-up gases (17.0, 14.0 and 10.0 mL/min) for hydrogen, air-1 and air-
2, respectively. The injection volume of the GC organophosphorus pesticide
determination was 2.0 µ L. The total run time for a sample was 14 min. Each sample
underwent duplicate analyses.
5.2.7 Quality assurance and control of method
For each batch of 20 samples, a procedural blank, a spiked blank and a pair of matrix spiked
sample/duplicate were processed. Extraction was done in duplicate for each sample. The spiked
samples contained all the 15 OCPs, 13 OPs and 9 SPs target analytes. All reagents used during the
analysis were of high quality (Appendix I) and were exposed to the same extraction procedures and
subsequently run to check that no interfering substances were present. No analytes were detected in
the blanks. Recalibration curves were run with each sample batch to ensure that correlation
coefficient was kept above 0.99. Strict cleaning procedures were adhered to viz: all glassware were
washed with hot water and detergents and copiously rinsed with distilled water. After drying, the
glass wares were further rinsed with acetone.
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5.2.8. Determination of per capita consumption in the study area.
The per capita fruit and vegetable consumption in Ghana, as stated by WHO (2005) are 0.0644
kg/person/day and 0.137 kg/person/day respectively. It is assumed that the per capita consumption
of vegetables in the cultivated area will be higher (following observations by Ntow, 2008) than that
at the national level and so also will be the associated health risk. Specific per capita consumptions
of onions, watermelons and pepper in the study area were therefore estimated. In the estimation,
face-to-face interaction was held with one hundred and fifty healthy adults from four farming
communities along the Afram arm of the Volta Lake (Dedeso, Kwahu Amanfrom, Adawso and
Kotoso). The information mainly elicited was daily frequency and quantity of consumption of the
three food items over 12 months. For each food item, individuals indicated the quantity and
frequency of consumption within a day.  In determining the quantity, they were presented with
samples of the food items and asked to indicate how much of it is consumed at an instance. The
quantity indicated was immediately weighed on a portable scale and recorded. Among the 150
people interviewed, 55% (82) were female and 45% (68) were male. By age categorization, 60%
(90) were adults (grown-ups of 12 years and above) while 40% (60) were children between the
ages of 6-11 years. There was a gender-specific difference in the rate of consumption of onion in
particular; women consumed more (180 g/day) than men (166 g/day). There was however no
gender difference in consumption of watermelon and pepper. Similarly, there was no age-specific
difference in the consumption of the food items. In most cases, the amounts of pepper and onion
consumed by children were determined by the adult since they normally prepare the meals for
consumption.
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5.2.9 Data Analysis
5.2.9.1 Dietary exposure and Health Risk Assessment
The dietary exposure to pesticides is calculated in order to assess the chronic (long-term) consumer
health risk. The Codex Alimentarius Commission Procedural Manual (Codex Alimentarius
Commission, 2006) defines exposure assessment as “the qualitative and/or quantitative evaluation
of the likely intake of biological, chemical, and physical agents via food as well as exposures from
other sources if relevant”. For each type of exposure, the estimated lifetime exposure dose
(mg/kg/day) is obtained by multiplying the residual pesticide concentration (mg/kg) in the food of
interest by the daily food consumption rate (per capita consumption) (kg/day), and dividing the
product by the body weight (kg). The per capita consumption of fruits and vegetables in Ghana,
according to a WHO-sponsored survey by Ruel et al., (2005) are 23.5 kg/person/year and 50.1
kg/person/year respectively. The general equation for dietary exposure is expressed as follows:
Dietary exposure = Food chemical concentration (mg/kg) × Daily Food consumption (kg/day)
(mg/kg/day) Body weight (kg)
Hazard index (HI) is used as a measure of the risk associated with the exposure. In HI assessment,
the estimated dietary exposure is compared with the toxicological reference value, Acceptable
Daily Intake (ADI) or reference dose (RfD). The acceptable daily intake (ADI) is a level of intake
of a chemical that can be ingested daily over an entire lifetime without any appreciable risk to
health (WHO, 2001).
Exposure dose
HI =
ADI
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Two hazard Indices were calculated; one based on national per capita consumption and the other
based on the estimated per capita consumption in the study area. Hazard indices were also
determined for two categories of people: children between the ages of <1-11 years and grown-ups
(12 years and above). In the health risk estimation, this study adopts the U.S. Environmental
Protection (1989,1996) assumption that: the hypothetical body weights of 0 – 1year children is 10
kg; >1 – 11 years old children is 30kg and 70-kg for adults.
5.2.9.2 Treatment of Non-Detect samples
To account for residue levels in commodities that were below limit of method detection, three
assumptions were considered. The first assumption that content of pesticides not detected have
been assumed to be 0 (zero). The limitation of this model is that the calculated results might be
underestimated, since non-detected residues are ignored. The second assumption is that actual
concentrations of Non-detect (ND) samples were equal to limit of detection. This model tends to
overestimate concentrations if there were no contamination of the sampled vegetables. The third
assumption that if a pesticide has not been detected at all in a commodity, then non-detect samples
of that commodity are assumed to be zero. If however, pesticide has been detected in some samples
of the commodity, then the non-detect samples are assumed to be 50% of the limit of detection
(Petersen et al., 2013). A correction factor is sometimes applied to the third assumption since it is
assumed that a small margin of overestimation can still occur because the summation of very small
frequencies of detection that may sometimes occur may still be high enough to be significant. The
correction factor is normally applied when the food commodity of interest undergoes processing or
part of it (for instance the outer part) will have to be rid off before consumption. In this study
concentration means, rather than summation will be used and means computed based on the second
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or third models/approaches will underestimate detected levels hence the first assumption adopted.
Furthermore, there is no need for correction factor since pepper and onion are consumed whole and
only the edible part of melon is extracted.
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5.3 Results
5.3.1 Overview
The identities of target chemicals of the three groups of pesticides (organochlorines – OCs,
organophosphates – OPs and Synthetic pyrethroids – SPs) detected in water melon, fresh chili
pepper and onion are presented in Tables 5.1 – 5.3. Means of residue are those of detect-samples
only while incidence rates are based on total number of samples. The pesticide concentrations are
determined on wet weight basis and compared with the maximum residue levels (MRL) allowed by
European Union (EU) countries in the food commodities.
5.3.2 Pesticide residues in watermelon samples
Out of the 16 organochlorine pesticides analysed, 5 of them; β-HCH, γ-HCH, heptachlor, γ-
chlordane and p,p’-DDT were detected and quantified in water melon samples in respective mean
concentrations of 0.081 mg/kg, 0.061 mg/kg, 0.0101 mg/kg, 0.0124 mg/kg and 0.001 mg/kg. Their
concentration ranges are also listed in Table 5.1. With the exception of p,p’-DDT, the mean
concentrations of all the other registered organochlorines exceeded the maximum residue limit
(MRL) set by the European Union (EU). Even though the incidence rate of β-HCH, γ-HCH were
low (27% and 20% respectively), they recorded residue levels above that recommended by the EU
in all samples in which they were quantified.
Out of the 9 targeted synthetic pyrethroid pesticides, 4; allethrin, fenpropathrin, cypermethrin and
fenvalerate had measureable quantities in any of the water melon samples and at very low
frequency of occurrence; below 20% in all of them. Their respective mean concentrations were
0.06 mg/kg, 0.004 mg/kg, 0.003 mg/kg and 0.003 mg/kg. Of the synthetic pyrethroids, only
allethrin had residue level (0.06 mg/kg) exceeding the EU limit of 0.01mg/kg.
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Table 5.1: Pesticide concentrations in Watermelon (n=30)
Pesticide Mean ± SD Range Incidence %  of detect samples EU
(mg/kg) Rate (%) above EU MRL MRL(mg/kg)
Organochlorines
β-HCH 0.0810 ±0.031 0.0337-0.1096 26.7 100 0.01
γ-HCH 0.0610 ±0.003 0.0572-0.0637 20.0 100 0.01
Heptachlor 0.0101 ±0.007 0.0006-0.0276 50.0 40 0.01
γ-Chlordane 0.0124 ±0.005 0.0029-0.0189 30.0 67 0.01
p,p'-DDT 0.0010 ±0.001 0.0007-0.0014 6.7 0 0.05
Load=0.1655
G-mean =0.0331
Pyrethroids
Allethrin 0.0604 ±0.023 0.0402-0.0805 13.3 100 0.01
Fenpropathrin 0.0041 ±0.000 0.0041 6.7 0 -
Cypermethrin 0.0033 ±0.000 0.0033 6.7 0 0.20
Fenvalerate 0.0030 ±0.000 0.003 6.7 0 0.02
Load=0.0708
G-mean =0.0177
Organophosphates
Methamidophos 0.0041 ±0.001 0.0022-0.0078 70.0 0 0.01
Ethoprophos 0.0012 ±0.0 0.0006-0.0016 13.3 0 0.02
Phorate 0.0018 ±0.002 0.0004-0.0078 26.7 0 0.05
Diazinon 0.0005* 0.0005 3.3 0 0.01
Dimethoate 0.0072 ±0.001 0.0039-0.0095 83.3 0 0.02
Chlorpyrifos 0.0018 ±0.001 0.0005-0.0037 20.0 0 0.05
Malathion 0.0015 ±0.001 0.0005-0.0033 36.7 0 0.02
Fenitrothion 0.0031 ±0.001 0.0005-0.004 16.7 0 0.01
Chlorfenvinphos 0.0005* 0.0005 3.3 0 0.02
Profenofos 0.0110 ±0.007 0.0026-0.0267 66.7 0 0.05
Load=0.0327
G- mean.=0.003
Load : Total of the means of all residues in a pesticide group
G-mean : Grand mean; i.e. mean of the concentrations of all pesticides of a pesticide group
* : Detects in single samples
Incidence Rate: Percentage frequency of occurrence of an individual pesticide in total sample
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Of the three groups of pesticides, the oraganophosphorus were the most encountered in the water
melon samples analysed. Ten out of the targeted 13 OPs were encountered. Pirimiphos-methyl,
fonofos and parathion were not quantified (below limit of detection) in any of the samples. Even
though most encountered, the OPs had very low residue levels, with the mean concentration range
of 0.0005–0.011 mg/kg. None exceeded their corresponding EU stipulated residue limit. Individual
pesticides like methamidophos, dimethoate and profenofos recorded high incidence rates of 70%,
83% and 67% respectively; while others like diazinon, fonofos and chloefenviphos were
encountered in single samples only.
5.3.3 Pesticide residues in chili pepper samples
Table 5.2 presents residual concentrations of organochlorine (OC), synthetic pyrethroid (SP) and
organophosphorus (OP) pesticides in chili pepper. The results show that 10 out of the targeted 15
OCs were encountered in the fresh samples of chili pepper analysed. Methoxychlor recorded the
highest mean concentration of 0.053 mg/kg, followed by γ-HCH (0.025 mg/kg), δ-HCH (0.022
mg/kg), p,p’-DDD (0.016 mg/kg), with p,p’-DDE and p,p’-DDT recording the lowest of 0.0014
mg/kg among the OCs. Delta HCH and p,p’DDT recorded incidence rate of 100%, followed by γ-
HCH (90%) and p,p’DDE (72%). γ-Chlordane recoded the lowest frequency of 15%.
Methoxychlor, though with a lower incidence rate (45%), had all its samples, as well as the mean
concentration (0.053 mg/kg) above the EU permissible limit of 0.01 mg/kg. Delta HCH also has its
mean (0.022 mg/kg), as well as 50% of its samples recording residue levels above EU limit (0.02
mg/kg). So also γ-HCH had 11% of its sample recording residue concentrations above the EU
limit, though the average concentration of 0.025 mg/kg is below the EU limit of 0.5 mg/kg.
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Table 5.2: Pesticide concentrations in Chili pepper (n = 20)
Pesticide Mean ± SD Range Incidence % of detect EU MRL
(mg/kg) Rate (%) samples above (mg/kg)
EU MRL
Organochlorines
β-HCH 0.0017 ±0.0004 0.0011-0.0023 45 0 0.5
γ-HCH 0.0248 ±0.017 0.0080-0.0539 90 11 0.5
δ-HCH 0.0221 ±0.02 0.0009-0.0531 100 50 0.02
γ-Chlordane 0.0032 ±0.002 0.0011-0.0058 15 0 0.02
p,p'-DDE 0.0014 ±0.001 0.0005-0.00396 80 0 1.0
Endrin 0.0049 ±0.004 0.0008-0.0123 70 0 0.1
Beta endosulfan 0.0072 ± 0.003 0.0023-0.0115 60 0 -
p,p'-DDT 0.0014 ±0.001 0.00037-0.003 100 0 1.0
p,p'-DDD 0.0163 ±0.011 0.0019-0.0274 65 0 -
Methoxychlor 0.0534 ±0.002 0.0512-0.0575 45 100 0.01
Load=0.1364
G- mean =0.0136
Pyrethroids
Allethrin 0.0066 ±0.002 0.0044 - 0.0104 40 12.5 0.01
Bifenthrin 0.0031 ±0.002 0.0007- 0.0086 45 0 0.10
Fenpropathrin 0.0044 ±0.001 0.0040 - 0.0051 30 0 -
Lamda-cyhalothrin 0.0086 ±0.003 0.0020 - 0.0137 85 0 0.05
Permethrin 0.0156 ±0.012 0.0027 - 0.0330 70 0 0.10
Cyfluthrin 0.0071 ±0.002 0.0032- 0.0118 100 0 0.10
Cypermethrin 0.0031 ± 0.002 0.0005 - 0.0052 65 0 0.10
Fenvalerate 0.0012 ±0.001 0.00047-0.0020 65 0 0.05
Deltamethrin 0.00055 ±0.0 0.0005 - 0.0006 10 0 0.05
Load=0.0501
G-mean =0.0056
Organophosphates
Methamidophos 0.0014 ± 0.001 0.0005-0.0004 25 0 0.10
Ethoprophos 0.0058 * 0.0058 5 0 0.02
Phorate 0.0017 * 0.00171 5 0 0.10
Diazinon 0.0015 * 0.00152 5 0 0.10
Fonofos 0.0022 ±0.002 0.0005-0.0063 35 0 0.01
Dimethoate 0.0056 ±0.003 0.0015-0.0114 45 0 0.50
Pirimiphos-methyl 0.0040 ±0.004 0.0007-0.0147 35 0 0.10
Chlorpyrifos 0.0087 ±0.003 0.0044-0.0150 50 0 1.00
Malathion 0.01 ±0.001 0.0090-0.0110 15 0 0.02
Parathion 0.004 ±0.0 0.0037-0.0042 15 0 0.10
Profenofos 0.0033 ±0.001 0.0024-0.0046 30 0 0.10
Load=0.0482
G-mean =0.0044
Load = Total of the means of all residues in a pesticide group
G-mean = Grand mean; i.e. mean of the concentrations of all pesticides of a pesticide group
* = Detects in single samples
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All 9 targeted SPs were encountered in the analysis of the chili pepper samples. Permethrin
recorded the highest residue concentration of 0.0156 mg/kg, followed by lamda-cyhalothrin (0.008
mg/kg), whilst deltamethrin recorded the lowest of 0.00055 mg/kg. The most encountered of the
SPs were cyfluthrin (100%), lamda-cyhalothrin (85%) and permethrin, (70%). Of all the SPs
encountered in chili pepper, only allethrin had 12.5% of total samples recording concentrations
above the EU permissible limit of 0.01 mg/kg.
With the exception of fenithrothion and chlorfenviphos, all the targeted OPs were encountered in
the chili pepper. However, the frequency of occurrence of the individual pesticides was very low.
For instance, chlorpyrifos with the highest incidence had a rate of only 50%, followed by
dimethoate (45%). Ethoprophos, phorate and Dimethoate all registered as low as 5% occurrence
rate. None of the concentration means as well as individual sample residue concentration also
registered values that equals or exceeds the EU limit. Malathion that was encountered in only three
samples, with incidence rate of only 15% recorded the highest mean concentration of 0.01 mg/kg,
followed by chlorpyrifos (50%).
5.3.4 Pesticide residues in onion samples
Table 5.3 presents concentrations of OCPs, SPs and OPs in onion samples. Among the OCs, β-
HCH recorded the highest level of 0.084 mg/kg, followed by γ-HCH (0.056 mg/kg) and Beta
endosulfan (0.051 mg/kg). The most widely encountered OCPs in onion samples were γ-HCH, γ-
Chlordane, Endrin, β-HCH and Beta endosulfan with occurrence rate of 80% - 100%.  As many as
8 organochlorine pesticides: β-HCH, γ-HCH, δ-HCH, γ-chlordane, p,p’-DDE, dieldrin, endrin and
methoxychlor had concentration in samples above their respective EU permissible limits; while 4
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of these β-HCH, γ-HCH, endrin and methoxychlor had mean concentrations also above the
permissible limits. All the samples had β-HCH levels above maximum limit of 0.01 mg/kg.
The range of mean concentration of SPs in onion samples was 0.0014 mg/kg – 0.0512 mg/kg.
Allethrin and deltamethrin recorded highest levels of 0.0512 and 0.02 mg/kg respectively. Only
allethrin registered mean concentration above the EU permissible limit and frequency of
occurrence was highest in fenpropathrin, lambda-cyahalothrin and deltamethrin; all recording 75%
incidence.
Organophosphorus pesticide occurrence was highest in onion samples, both in concentration and
incidence. Four OPs; methamidophos, ethoprophos, diazinon and dimethoate all recorded incident
rate of 100%. The OPs concentration range was 0.071 mg/kg – 0.0036 mg/kg, with dimethoate at
the apex and malathion at the rear of concentration range.
In summary, concentration and incidence of pesticides was highest in onion samples, followed by
pepper and water melon. The number of samples that had pesticide concentrations exceeding their
corresponding EU limits follows the order: onion ˃ water melon ˃ pepper. In this study, OCPs
registered the highest mean concentration in each of the three food items analysed; being
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Table 5.3: Pesticides concentrations in Onions (n = 20)
Pesticide Mean ± SD Range Incidence % of detect EU MRL
(mg/kg) rate (%) samples above (mg/kg)
EU MRL
Organochlorines
β-HCH 0.0842 ±0.02 0.0432-0.3150 80 100 0.01
γ-HCH 0.0561 ±0.027 0.0015-0.1017 100 90 0.01
δ-HCH 0.0069 ±0.005 0.0005-0.0182 40 12.5 0.01
γ-Chlordane 0.0091 ± 0.004 0.0050-0.0191 100 25 0.01
p,p'-DDE 0.0163 ±0.031 0.0005-0.0855 35 14 0.05
Dieldrin 0.0091 ±0.002 0.0076-0.0109 20 50 0.01
Endrin 0.0125 ±0.009 0.0040-0.0566 85 23 0.01
Beta endosulfan 0.0513 ±0.031 0.005-0.11526 80 0 0.1
p,p'-DDT 0.0216 ±0.017 0.0021-0.0456 45 0 0.05
Methoxychlor 0.0209 ±0.018 0.0005-0.0624 60 53 0.01
Load=0.288
G-mean =0.0288
Pyrethroids
Allethrin 0.0512 ±0.005 0.0470-0.0600 25 100 0.01
Bifenthrin 0.0018 ±0.0 0.0014-0.0023 55 0 0.05
Fenpropathrin 0.0179 ±0.007 0.0099-0.0315 75 0 -
Lamda-cyhalothrin 0.0132 ±0.013 0.0015-0.0400 75 0 0.2
Permethrin 0.0088 ± 0.006 0.0020-0.0181 45 0 0.05
Cyfluthrin 0.0015 ± 0.0 0.0009-0.0019 40 0 0.02
Cypermethrin 0.0016 ± 0.001 0.0006-0.0027 35 0 0.1
Fenvalerate 0.0014 ± 0.001 0.0005-0.0029 15 0 0.02
Deltamethrin 0.0200 ±0.019 0.0014-0.0554 75 0 0.1
Load=0.1174
G-mean =0.013
Organophosphate
Methamidophos 0.0550 ±0.034 0.0145-0.1087 100 100 0.01
Ethoprophos 0.0138 ±0.008 0.0029-0.0246 100 40 0.02
Diazinon 0.0123 0.0008-0.0205 100 0 0.05
Fonofos 0.0080 ±0.005 0.0056-0.0099 15 0 0.01
Dimethoate 0.0711 ±0.002 0.0037-0.1323 100 75 0.02
Pirimiphos-methyl 0.0067 ±0.046 0.0008-0.0165 80 0 0.05
Chlorpyrifos 0.0410 ±0.004 0.0089-0.0600 75 0 0.2
Malathion 0.0036 ±0.019 0.0005-0.0066 25 0 0.02
Fenitrothion 0.0300±0.012 0.0021-0.0445 40 87.5 0.01
Parathion 0.0096 ±0.0 0.0094-0.0100 20 0 0.05
Chlorfenvinphos 0.0178 ±0.004 0.0126-0.0270 45 0 0.05
Profenofos 0.0046 ±0.0 0.0040 10 0 0.05
Load=0.2735
G-mean =0.023
Load = Total of the means of all residues in a pesticide group
G-mean = Grand mean; i.e. mean of the concentrations of all pesticides of a pesticide group
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highest in water melon (0.033 mg/kg), followed by onion (0.0288 mg/kg) and pepper (0.0136
mg/kg). Total residue concentrations (Load) in each of the pesticide groups in the three food items
are as follows: OCs ˃ SPs ˃ OPs (for watermelon and fresh chili pepper) and OCs ˃ OPs ˃ SPs
(for onions) (Tables 5.1 - 5.3).
5.3.5 Health risk analysis
The daily consumption of onion and watermelon was found to be higher in the study area,
compared to the national per capita consumption. Per capita consumption of pepper in the study
area was however lower than at the national level (Table 5.4).
Table 5.4: Daily consumption of food items in the study area compared to national per capita
consumption for Ghana
Food item Daily consumption in study area National per capita consumption
(g/person/day) (g/person/day)
Onion 173 ± 35 137.3
Pepper 14 ± 5 137.3
Watermelon 900 ± 150 64.4
Analysis of health risk associated with consumption of each of the food commodities was carried
out and the results presented in Tables 5.5 – 5.7. Residues were selected based on those
concentrations exceeding the EU MRL, reference dose values and relative high concentration
levels.  Smaller reference dose values have serious/greater impact on the calculated hazard index
and hence residues with very small reference values are of important concern, even though their
residual concentrations in the food crops may be small. Health risk was calculated for the year 1-11
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and adult categories (12 years and above). Children belonging to the 0-1year group were not
considered for the risk determination since their consumption of these food items is insignificant.
Watermelon registered residues associated with health risk (Table 5.5), and these are heptachlor
and β-HCH. So also dieldrin level in onion is associated with some level of health risk. No risk was
associated with residues in pepper samples since all the Hazard Indexes were less than unity
(Tables 5.6 and 5.7). It is also observed that health hazard was mainly associated with dietary
exposure among both adults and children in the study area only.
Table 5.5: Health risk estimates for systemic effects associated with pesticide residues in
Watermelon
Pesticide ADI Exposure dose- mg/kg/day Exposure dose- HI1 HI2
mg/kg/day (based on Per capita mg/kg/day
consumption in study area) (base on national
Per capita consumption)
β-HCH 0.005 1.04 x 10-3 - Adults 7.5 x10-5 - Adults 0.21 0.015
2.43 x 10-3 – Children 1.7 x 10-4 – Children 0.50* 0.03
γ-HCH 0.005 7.8 x 10-4 – Adults 5.6 x10-5 – Adults 0.16 0.011
1.8 x 10-3 – Children 1.3 x 10-4 – Children 0.37 0.03
Heptachlor 0.0001 1.3 x 10-4 – Adults 9.3 x 10-6 – Adults 1.30* 0.09
3.0 x 10-4 – Children 2.2 x 10-5 – Children 3.03* 0.22
γ-Chlordane 0.001 1.6 x 10-4 – Adults 1.14 x 10-5 – Adults 0.16 0.01
3.7 x 10-4 – Children 2.7 x 10-5 – Children 0.37 0.03
Allethrin 0.008 7.8 x 10-4 – Adults 5.5 x 10-5 – Adults 0.10 0.007
1.8 x 10-3 – Children 1.3 x 10-4 – Children 0.23 0.02
Fenpropathrin 0.030 5.3 x 10-5 – Adults 3.8 x 10-6 – Adults 0.002 0.0001
1.2 x 10-4 – Children 8.8 x 10-6 – Children 0.004 0.0003
Dimethoate 0.001 9.3x 10-5 – Adults 6.6 x 10-6 – Adults 0.09 0.01
2.2 x 10-4 – Children 1.5 x 10-5 – Children 0.22 0.02
Profenofos 0.030 1.4 x 10-4 – Adults 1.0 x 10-5 – Adults 0.005 0.0003
3.3 x 10-4 – Children 2.4 x 10-5 – Children 0.01 0.001
Methamidophos 0.001 5.3 x 10-5 – Adults 1.0 x 10-5 – Adults 0.05 0.01
1.2 x 10-4 – Children 8.8 x 10-6 – Children 0.12 0.01
HI1: Hazard Index based on per capita consumption in the study area.
HI2: Hazard Index based on national per capita consumption
* : Hazard index significant enough to indicate possible health implication
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Table 5.6: Health risk estimates for systemic effects associated with pesticide residues in
Chili pepper
Pesticide ADI Exposure dose- Exposure dose- mg/kg/day HI1 HI2
mg/kg/day mg/kg/day (base on national
(based on Per capita Per capita consumption)
consumption in study
area)
γ-HCH 0.005 5.0 x 10-6 – Adults 4.9 x 10-5 – Adults 0.001 0.01
1.2 x 10-5 – Children 1.1 x 10-4 – Children 0.002 0.02
δ-HCH 0.005 4.4 x 10-6 – Adults 4.3 x 10-5 – Adults 0.001 0.01
1.0x 10-5 – Children 1.0 x 10-4 – Children 0.002 0.02
Methoxychlor 0.005 1.0 x 10-5 – Adults 1.0 x 10-4 – Adults 0.002 0.02
2.5 x 10-5 – Children 2.5 x 10-4 – Children 0.005 0.05
Permethrin 0.05 3.1 x 10-6 – Adults 3.0 x 10-5 – Adults 0.00006 0.0006
7.3 x 10-6 – Children 7.3 x 10-5 – Children 0.0001 0.001
λ-cyahalothrin 0.005 1.7 x 10-6 – Adults 1.7 x10-5 – Adults 0.0003 0.003
4.0 x 10-6 – Children 4.0 x 10-5 – Children 0.001 0.01
Allethrin 0.008 1.3 x 10-6 – Adults 1.3 x 10-6 – Adults 0.0001 0.002
3.1 x 10-6 – Children 3.1 x 10-5 – Children 0.0004 0.004
Malathion 0.030 2.0 x 10-6 – Adults 1.9 x 10-5 – Adults 0.00006 0.0006
4.7 x 10-6 – Children 4.7 x 10-5 – Children 0.0002 0.002
Chlorpyrifos 0.010 1.7 x 10-6 – Adults 1.7 x 10-5 – Adults 0.0002 0.002
4.1 x 10-6 – Children 4.1 x 10-5 – Children 0.0004 0.004
Dimethoate 0.001 1.1 x 10-6 – Adults 1.0 x 10-5 – Adults 0.001 0.01
2.6 x 10-6 – Children 2.6 x 10-5 – Children 0.003 0.03
Ethoprophos 0.0001 1.1 x 10-6 – Adults 1.0 x 10-5 – Adults 0.01 0.11
2.7 x 10-6 – Children 2.7 x 10-5 – Children 0.03 0.30
HI1: Hazard Index based on per capita consumption in the study area.
HI2: Hazard Index based on national per capita consumption
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Table 5.7: Health risk estimates for systemic effects associated with pesticide residues in Onions
Pesticide ADI Exposure dose- mg/kg/day Exposure dose- mg/kg/day HI1 HI2
mg/kg/day (based on Per capita (base on national
consumption in study area) Per capita consumption)
β-HCH 0.005 2.1 x 10-4 – Adults 1.6 x 10-4 – Adults 0.04 0.03
4.8 x 10-4 – Children 3.9 x 10-4 – Children 0.10 0.08
γ-HCH 0.005 1.4 x 10-4 – Adults 1.1 x 10-4 – Adults 0.03 0.02
3.2 x 10-4 – Children 2.6 x 10-4 – Children 0.07 0.05
δ-HCH 0.005 1.7 x 10-5 – Adults 1.4 x10-5 – Adults 0.003 0.003
4.0 x 10-5 – Children 3.0 x 10-5 – Children 0.008 0.006
Dieldrin 0.0001 2.3 x 10-5 – Adults 1.8 x 10-5 – Adults 0.23 0.18
5.3 x 10-4 – Children 4.2 x 10-5 – Children 5.30* 0.42
Endrin 0.0002 3.1 x 10-5 – Adults 2.5 x 10-5 – Adults 0.15 0.12
7.2 x 10-5 – Children 5.7 x 10-5 – Children 0.36 0.29
β-HCH 0.005 2.1 x 10-4 – Adults 1.6 x 10-4 – Adults 0.04 0.03
4.8 x 10-4 – Children 3.9 x 10-4 – Children 0.10 0.08
γ-chlordane 0.001 2.3 x 10-5 – Adults 1.8 x 10-5 – Adults 0.02 0.02
5.3 x 10-5 – Children 4.2 x 10-4 – Children 0.05 0.04
Methoxychlor 0.005 5.1 x 10-5 – Adults 4.1 x 10-5 – Adults 0.01 0.008
1.2 x 10-4 – Children 1.0 x 10-4 – Children 0.02 0.02
Allethrin 0.008 1.3 x 10-4 – Adults 1.0 x 10-4 – Adults 0.02 0.01
3.0 x 10-4 – Children 2.3 x 10-4 – Children 0.04 0.03
Methamidophos 0.001 1.4 x 10-4 – Adults 1.0 x 10-4 – Adults 0.14 0.11
3.2 x  10-3 – Children 2.5 x10-4 – Children 3.20* 0.25
Dimethoate 0.001 1.8 x 10-4 – Adults 1.4 x 10-4 – Adults 0.18 0.14
4.1 x 10-4 – Children 3.3 x 10-4 – Children 0.41 0.3
Fenitrothion 0.005 7.4 x 10-5 – Adults 5.9 x 10-5 – Adults 0.01 0.01
1.7 x 10-4 – Children 1.4 x 10-4 – Children 0.04 0.03
Chlorfenviphos 0.0005 4.4 x 10-5 – Adults 3.5 x 10-5 – Adults 0.09 0.07
1.0 x 10-4 – Children 8.2 x 10-5 – Children 0.21 0.16
HI1: Hazard Index based on per capita consumption in the study area.
HI2: Hazard Index based on national per capita consumption
* : Hazard index significant enough to indicate possible health implication
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5.4 Discussions
5.4.1 Organochlorine pesticide residues in fruit and vegetables
Twelve organochlorine pesticide residues (OCPs), namely: β-HCH, γ-HCH, δ-HCH, p,p’-DDT,
p,p’-DDE, p,p’-DDD,  dieldrin, endrin, heptachlor, γ-chlordane, β-endosulfan and methoxychlor,
representing 80% were detected in the fruit and vegetables (watermelon, pepper and onion)
samples analysed. The range of mean concentration was 0.001 – 0.084 mg/kg. The highest
concentration was measured for β-HCH in onion (0.084 mg/kg) while the lowest (0.001 mg/kg)
was recorded for p,p’-DDT in watermelon (Tables 5.1 – 5.3). Fifty percent of the watermelon
samples registered the presence of one or more OCP residues while residues were measured in
100% samples of both pepper and onion. The limit of detection of OCPs was 0.15µg/kg (0.00015
mg/kg). The total of the mean of all OCP residues (load) was highest in onion (0.288 mg/kg),
followed by watermelon (0.166 mg/kg) and then pepper (0.136 mg/kg). The incidence rates of the
OCPs were lower in watermelon but higher and similar in pepper and onion (Tables 5.1 – 5.3). In
all, nine pesticides (: β-HCH, γ-HCH, δ-HCH, p,p’-DDE  dieldrin, endrin, heptachlor, γ-chlordane,
and methoxychlor), representing 24.3% exceeded the European union maximum residue level (EU
MRL). Eight of them (21.6%) exceeded in onion (Table 5.3), four (10.8%) in watermelon (Table
5.1) and 3 (8%) in pepper (Table 5.2). Twenty one and a third percent (21.3%) of watermelon
samples contained organochlorine pesticide residues whose concentrations were above the EU
MRL; 35% of pepper samples contained pesticides above MRL while in onion it was 29.4% of
samples. Meanwhile, 100% of the samples registered the presence of one or more OCP pesticides.
Botwe et al., (2011) measured concentrations of DDT, lindanes and methoxychlor in pepper and
onion samples from Ashanti region in a range of 0.01 – 7.43 µg/kg and 0.02 - 46.95 µg/kg
respectively. These figures are lower than what is reported in this study for the same vegetables. In
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the same way, reported concentrations for vegetables by Owago et al., (2009) for β-HCH, γ-HCH,
δ-HCH, DDE, DDD and DDT for vegetables in Deyang and Yantin areas in China were
comparably lower than findings in this study. However, residue concentrations of 0.041 mg/kg,
0.023 mg/kg and 0.035 mg/kg measured by Bempah et al. (2012) respectively for methoxychlor,
p,p’-DDE and p,p’-DDT in onion samples from the Greater Accra Region of Ghana were observed
to be higher than corresponding concentrations from the current study. Bempah et al., (2012) also
recorded higher levels of DDT (0.008 mg/kg) in watermelon samples but lower lindane (0.004
mg/kg), methoxychlor dieldrin and endrin levels. Whereas their (Bempah et al., 2012) investigation
of pesticide levels in fruits and vegetables from markets in Greater Accra recorded 4 OCPs
(methoxychlor, lindane, dieldrin, and endrin) exceeding the European Commission (EC) maximum
residue limits, their earlier similar investigation (Bempah et al., 2011) in Kumasi metropolis
reported 5 (γ-lindane, methoxychlor, dieldrin endrin and p,p’-DDE) exceeding MRL.
Asiedu (2013) who also investigated pesticide residues in fruits and vegetables in three regions of
Ghana (Eastern, Central and Greater Accra) recorded far higher mean concentration range of OCPs
(0.01 – 1.27  mg/kg), as compared to 0.001 – 0.084 mg/kg in the present study. He also listed 7
OCPs (β-HCH, γ-HCH, heptachlor, aldrin, dieldrin, endrin and p,p’-DDE) (as against 9 in the
present study) as exceeding the MRL.  Comparison of the present results with that of the other
local studies quoted above reveal that β-HCH, γ-HCH, heptachlor, dieldrin, endrin, p,p’-DDE and
methoxychlor always seem to exceed MRL in fruits and vegetables. Meanwhile, all of them are
listed among pesticides that have been banned from agricultural use in this country. Although their
levels may not necessarily be due to current inputs, there is still therefore the need for stakeholder
agencies like Ghana EPA and Standard Authority to redouble their efforts in monitoring. Whereas
the consistent similar concentration levels of β-HCH and γ-HCH fruit and vegetables analysed in
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this study could imply both new input and biotransformation of γ-HCH to β-HCH, p,p’-DDE is
known to be a degradation product of DDT that is energetically more stable and therefore
persistent in matrices of many commodities Manz et al., (2001). Endrin is also a conversion
product of both aldrin and dieldrin. From the current study, endrin dieldrin and aldrin were not
detected in watermelon while only endrin was recorded in chilli pepper. In onion however, both
endrin and dieldrin were recorded with endrin: dieldrin ratio (1.4) being greater than unity,
implying source of the drins to be from old inputs. Prevalence of methoxychlor on the other hand is
difficult to account for, particularly because field survey does not indicate its use. Bempah and
Donkor (2010), however, suggested that methoxychlor is technically a component of DDT during
its formulation and therefore as historically used DDT is being degraded, level of methoxychlor
should be expected to rise.
5.4.2 Synthetic pyrethroid residues in fruit and vegetables
Synthetic pyrethroids (SPs) were detected in watermelon, chili pepper and onion samples and in a
mean concentration range of 0.0005 mg/kg – 0.0604 mg/kg. The highest was measured for allethrin
in watermelon, while the lowest was recorded for deltamethrin in pepper. Residues were measured
in 13.3% of watermelon samples, 75% in onion and 100% in pepper. Forty-four percent of the SPs
were measured in watermelon and 100% of them measured in both onion and pepper samples. The
limit of detection and quantitation were 0.00015 mg/kg (0.15 µg/kg) and 0.0005 mg/kg (0.5.
µg/kg), respectively. Pyrethroid load was highest for onion (0.117 mg/kg), followed by watermelon
(0.0708 mg/kg) and then pepper (0.0501 mg/kg). Only allethrin exceeded the MRL in all the three
food crops analysed. Whereas all samples contained residues, only 14.3% of them recorded
pyrethroid pesticides with levels above MRL.
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Bempah et al., (2011) analysed pyrethroid levels in fruits and vegetables in Kumasi, Ashanti
Region of Ghana. They quantified levels of only permethrin, cyfluthrin and deltamethrin in
watermelon. These pyrethroids were, however, below limit of detection in watermelon samples
from this study. They also quantified levels of permethrin, cyfluthrin, fenvalerate and deltamethrin
in pepper and onion in a range of 0.009 mg/kg – 0.10 mg/kg which was higher, compared to 0.0005
mg/kg – 0.02 mg/kg for the same pesticides in this study. In another study, the same nine SPs
under investigation in this study were investigated by Gonu et al., (2012) in pepper samples from
an irrigation field in the Northern Region. They established a concentration range of 0.0023 mg/kg
– 0.1428mg/kg. Their range was higher than the 0.0005 mg/kg – 0.0156 mg/kg recorded for pepper
in the current study. Whereas allethrin and deltamethrin recorded the lowest and the highest
concentrations respectively in their study, deltamethrin and permethrin recorded the highest and the
lowest concentrations, respectively in this study.
Comparison with works from other regions of the world reveals that findings in this study are in
good agreement with that of Zawiya et al., (2007) in Malaysia, and Masud and Hassan (1992) in
Pakistan. As noted by Bempah et al., (2011), the increasing presence of pyrethroid insecticide
residues in food crops is an indication of a shift from the use of organochlorine pesticides to the
easily degradable groups of pesticides. If the pyrethroids are non-persistent yet they are found to
have high detection rate in food crops, then the misuse and abuse of them are likely and this should
be cause for serious concern and therefore more investigation.
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5.4.3 Organophosphorus pesticide residues in fruit and vegetables
All the thirteen organophosphorus pesticides (OPs) under study, i.e. 100% of the OPs were
measured in the sample. Ten, eleven and twelve OPs were measured in watermelon, pepper and
onion samples, respectively. These values represent 77%, 84% and 92.3% of OPs respectively
detected in the food crops (Tables 5.1-5.3). The mean concentration range recorded for the OPs in
the analysed fruit and vegetables was 0.0005 – 0.0711 mg/kg. Dimethoate recorded the highest
value in onion while the least was recorded by chlofenvinphos in watermelon. Onion recorded the
highest OP load of 0.2735 mg/kg; followed by pepper (0.048 mg/kg) and then watermelon (0.0327
mg/kg). Whereas none of the watermelon and pepper samples recorded OP level above MRL,
onion recorded levels in four OPs (methamidophos, ethoprophos, dimethoate and fenitrothion)
exceeding MRL (Table 5.3). Methamidophos for instance, apart from having 100% incidence rate,
also exceeded MRL in 100% of the samples.
The level of OPs in food crops in this study agrees with local findings by Bempah et al., (2012)
and Botwe et al., (2011) as well as studies outside Ghana by Sanghi and Tewari (2001) and
Paeveen, Khuhro and Rafiq, (2004). Dimethoate levels in pepper and onion were however higher
than those reported by Botwe et al., (2011). The fact that every single sample contained one or
more pesticide residue indicates most farmers did not follow good agricultural practices of
observing a pre-harvest interval (PHI); a minimum period of time allowed between the last
application of pesticide on food crops and final harvesting. The PHI is specific for each pesticide
and is necessary to allow enough time for pesticides to degrade to an acceptable level (Baig et al.,
2009).
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5.4.4 Health Risk Estimate
Health risk estimates for systemic effects associated with pesticide residues in watermelon, pepper
and onion are presented in Tables 5.5 -5.7. The tables comprise acceptable daily intakes (ADIs),
computed average daily intakes based on national per capita consumption, estimated per capita
consumption for the study area and corresponding hazard indices for children (1-11 years) and
grown-ups (12 years and above). The hazard indices showed that heptachlor, β-HCH, dieldrin and
methamidophos showed health risk association. Examination of the results in Tables 5.5-5.7 shows
that only watermelon and onion contain pesticides with hazard indices indicating health risk
association. Heptachlor and β-HCH have significant hazard indices in watermelon while dieldrin
and methamidophos had significant hazard indices in onion. The indices of heptachlor indicate
potential for systemic toxicity in both adults and children.
It should be noted that apart from heptachlor indicating toxicity in both adults and children, the
other pesticides with significant hazard indices (β-HCH, dieldrin and methamidophos) point to
potential toxicity in children only, who constitute the most vulnerable subgroup of the population.
It is also worthy of note that the hazard indices indicating potential health risk are all based on per
capita consumption estimates for the study area. This trend was also observed by Ntow (2008) in
vegetable producing community of Akumadan in the Ashanti Region of Ghana. Ntow explained
that the trend is not surprising since the consumption of food crops is normally higher in the
producing communities. In children, hazard indices computed for β-HCH, dieldrin and
methamidophos (based on field per capita consumption) were less than unity (0.50, 0.53 and 0.32
respectively) (Tables 5.5 and 5.7). They are however significant and associated with health risk
since their respective estimated doses (0.0044, 0.0053 and 0.0032 mg/kg/day) are either higher or
close to their corresponding ADIs (Tables 5.5 and 5.7).
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Analysis of 37 pesticide residues of watermelon, chili pepper and onion from cultivated fields
along the banks of the Afram arm of the Volta Lake established the facts that 92% of the pesticides
were recorded in 92.9% of the total samples. Hundred percent of target organophosphorus and
pyrethroid and 80% of organochlorine pesticides were quantified in the samples. The ranges of
mean concentrations of the three groups of pesticides, OCPs, SPs and OPs were 0.001 – 0.084
mg/kg, 0.0005 – 0.0604 mg/kg and 0.0005 – 0.0711 mg/kg respectively. The pesticide residual
load in the three food commodities follows the order: onion > watermelon > pepper. Levels of
37.8% of the pesticides (β-lindane, γ-lindane, δ-lindane, γ-chlordane, dieldrin, endrin, p,p’-DDE,
methoxychlor, alletrin, methamidophos, ethoprophos, diamethoate and fenvalerate) exceeded the
EU MRL in one or more of the food crops, and as many as 10 detected pesticides are among those
that have been banned from use by the EPA, Ghana. These are: β-lindane, γ-lindane, δ-lindane, γ-
chlordane, dieldrin, endrin, p,p’-DDT, methamidophos, heptachlor and parathion. Health risk
analysis indicates that heptachlor, β-lindane, dieldrin and methamidophos may be of public concern
since their concentration levels exceeded the reference doses in watermelon and onion samples
analyzed indicating a great potential for systemic toxicity to consumers in Ghana.
It must be noted that fruits and vegetables are now important commodities for Ghana’s non-
traditional export market. Standards and quality control measures demanded by European Union
(EU) countries on these commodities are very high and exportation from Ghana has of recent been
particularly problematic since pesticide quality standard of most of the commodities, especially
pineapple has not been met. When this happens, the country loses foreign exchange earnings,
farmers who made huge investment into the production fail to meet production cost, labourers on
plantation farms are either laid off or unpaid and the entire economy is affected in one way or the
other. Above all, the risk of systemic toxicity to local consumers become real concern since
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chronic health effects as a result of long-term dietary pesticide exposures become difficult to deal
with.
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CHAPTER SIX
PESTICIDE CONTENT OF WATER AND SEDIMENT TOXICITY
OF THE AFRAM ARM OF THE VOLTA LAKE
6.1 Background
Globally, there is widespread chemical pollution of fresh water bodies. This is of much concern
since fresh water bodies tend to be main sources of potable water for many communities. A major
source of chemicals like pesticides in water bodies is from run-offs from agricultural fields. The
persistence and mobility of pesticides in soils, coupled with their ability to disperse in water greatly
contribute to their potential to contaminate water (Nowell et al., 1999). Pesticides may be in the
dissolved phase or associated with soil particles when they enter surface water column (Nowell et
al., 1999). The particle-associated pesticides may subsequently be deposited to the bed sediment
and remain in this domain for a very long time. Sediments therefore represent a principal long-term
environmental sink of pesticides from which food chains, overlying water column as well as
ground water could be contaminated (Nowell et al., 1999; Xue et al., 2006). Sediments are
important in the functioning of aquatic ecosystems because they serve as reservoirs of
contaminants for bioaccumulation and trophic transfer (Burton, 2002). For this reason, once
chemical contamination level reaches a point at which it causes adverse effect to biota, sediment is
considered polluted and hence merits remediation intervention. To determine whether sediment is
contaminated or not, its quality is first determined and compared with internationally established
sediment quality criteria or guidelines. Decisions are then made whether it presents risk or not.
According to Fluck et al., (2010), sediment quality criteria for instance can be depended on to
classify sediment samples with regard to their toxic potential, identify problematic contaminants,
put priorities on areas based on the frequency and degree of which values are exceeded. Risk
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assessment of sediments is a relatively new and rapidly developing field that has been embraced by
international research outfits worldwide (Burton, 2002).
The major inland water bodies in Ghana tend to be epicenters of numerous anthropogenic
activities, particularly, agriculture. Existing literature search reveals all or most the water bodies
are associated with some levels of pesticide residues. The Volta Lake in particular has experienced
a sizeable increase in farming, industrial and cultural activities along its entire course. According to
Ntow, (2005), the short distances between agricultural fields and waterways increase the
probability of agrochemicals reaching the waterways via agricultural run-offs. The water level in
the Volta Lake experiences occasional rise and fall. Currently, due to climate variability, the
recession and flooding times are highly unpredictable. Nevertheless, there is still occasional
flooding of the banks when there is sufficient recharge from the upper courses of the Volta Lake.
When the level of water in the lake recedes, there is intense farming along the immediate banks to
take advantage of the residual moisture in soil to grow short maturing crops such as vegetables and
fruits. When water level rises again, the previously farmed lands, or lands still under cultivation are
covered with water. It is pertinent to know the implication of occasional flooding of farmlands on
pesticide water quality of the Afram waters, particularly since the river is the only source of
potable water for the majority of the riparian communities.
In keeping with the worldwide interest in quantifying and controlling pollution of surface waters
(Brown et al., 2002), this chapter assesses pesticide content of surface sediment of Afram arm of
the Volta Lake and evaluates its toxicity by using established sediment quality criteria (with
particular respect to organochlorine pesticides). In addition, quality of water from the Afram arm of
the Volta Lake during the recession period, and the period of water rise when cultivated lands are
flooded is compared.
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6.2 Materials and Methods
6.2.1 Sampling of water and sediment
Water samples were collected in December 2011 and July 2012. The December samples were
taken at a time when water level had risen and flooded the banks while the July samples were taken
when it was observed that water level had receded. A total of eighty water samples were collected
from four sites (Odortom, Kwahu Amanfrom, Adawso and Kotoso sites – Fig 3.1) along the Afram
arm of the Volta Lake. Water samples were taken approximately 0.5 m below the surface at
midstream positions to approximate the mean concentrations of water from the river. The samples
were taken with a 3 L Goflon water sampler into 1 L amber glass bottles that were previously
washed with detergent, rinsed with distilled water, dried and finally rinsed with acetone. Prior to
sample collection, each bottle was rinsed with sample water three times. Twenty samples per site
were collected.
Sediment samples were taken from sites of water collection points after water samples had been
taken. Grab samples of fine textured lake sediment were collected from the bottom at the mid-
stream of the river. As much as possible, sediment samples were taken at mid-stream points where
the Afram River was not very broad; otherwise, samples were generally taken at an approximate
distance of 50 metres from the recession bank mark. Composite samples were pooled from three
subsamples and properly homogenized. The composite samples were wrapped in aluminium foils
and placed in zip-locked plastic bags. Twelve composite samples per site were taken; thus a total of
forty-eight sediment samples were taken. Water and sediment samples were separately stored on
ice at approximately 4°C during transport until they were brought to the Pesticide Laboratory at the
Ghana Standard Authority where sediment samples were stored in a deep freezer at -4°C and water
samples in refrigerator at 4°C pending analyses.
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6.2.2 Chemicals and Reagents
Full list of Chemicals and Reagents needed for the study is presented in Appendix I
6.2.3 Extraction of samples
6.2.3.1 Extraction of pesticides from water samples
Water samples were removed from fridge and allowed to equilibrate with the ambient temperature.
The water samples were extracted according to Mathur et al., (2003) and as done routinely in the
Ghana Standards Authority pesticides Laboratory. Water samples were well shaken and filtered
through whatman no.1 filter paper. After filtration, 1 litre water sample was taken in a 2 litre
capacity separatory funnel and 30 mL of saturated sodium chloride solution was added. The water
sample was partitioned with 100 mL of methylene chloride (thrice) by shaking the separatory
funnel vigorously for 2-3 minutes and releasing the pressure intermittently. The layers were
allowed to stand for 10 minutes to separate. The three extracts of methylene chloride layers were
combined and passed through anhydrous sodium sulphate and concentrated to about 2 mL
using rotary vacuum evaporator.
6.2.3.2 Extraction of pesticides from sediment samples
Sediment was wet extracted and followed the method of Muir & Sverko, (2006). Sediment samples
were removed from storage freezers and allowed to thaw. The percentage of water in each sample
was determined by accurately weighing 10 g, drying at 105°C and reweighing to a constant dry
weight. A wet weight equivalent to 10 g dry sample was calculated for each sample after
determining the percentage of water. Equivalent of 10 g dry sediment, samples were therefore
extracted per sample. Comminuted homogenous wet weight sediment samples equivalent to 10 g
dry samples were weighed into 100 mL separating flasks and 10ml acetonitrile added to each. The
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flasks were stoppered and sonicated for 5 minutes in a Decon sonicator model FS 400B. A further
10 mL acetonitrile was added to each flask, placed on a horizontal mechanical shaker and set to
shake continuously for 30 minutes at 300 motions per minute. The mixture in each flask was
allowed to stand for 10 minutes to separate layers. The organic phase (top layer) was decanted and
dried over 5 g anhydrous magnesium sulphate through No. 1 Whatman filter paper. Ten mililitre
aliquots of the filtrate were introduced into 50 ml round-bottomed flasks and evaporated to 1 mL
concentrate using Buchi rotary vacuum evaporator. Duplicate of previously extracted sediment
samples were spiked with standard pesticide mix solutions and taken through the entire extraction
process in order to determine recovery efficiency.
6.2.4 Clean-up of pesticide extracts from water and sediment samples
Clean-up of the extracted samples was done by column chromatography. Ten mililitres
polypropylene cartridge was packed with activated silica gel 2 g (heated for 2h at 130°C) packed
between two layers of sodium sulphate (1 g each) and the column was conditioned with 10 mL of
methylene chloride and not allowed to dry. The 2 mL concentrate from the water extraction was
then loaded onto the conditioned cartridges. The flask was rinsed with 10 mL methylene chloride
and used to elute the column into a pear-shaped flask. The elution was repeated with another 10
mL portion of methylene chloride. The combined eluate was collected and evaporated to dryness
using rotary vacuum evaporator. A final sample of 2 mL was prepared in ethyl acetate (HPLC
grade) and analyzed by Gas Chromatograph. Cleaning of sediment extracts was done exactly in the
same manner except that acetonitrile, instead of methylene chloride was used for the elution.
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6.2.5 Recovery test of extraction efficiency
Recovery tests for water analysis was carried out prior to analysis by fortifying de-ionized water
samples with 5 ml of 0.05 µg/L standard mixture solutions of organochlorines, organophosphorus
and synthetic pyrethroid pesticides to determine the efficiency of the analytical techniques.
Similarly, 5 ml of 0.05 µg/L standard mix pesticide solution was spiked into previously extracted
sediment samples. These fortified samples were then extracted in manners similar as their
corresponding matrix samples.
2 − 1
% = 100
Where: C1 = Concentration (mg/kg) of pesticide residue in the matrix blank
C2 = Concentration (mg/kg) of pesticide residue in the spiked matrix
C = Concentration (mg/kg) of pesticide added
Recovery for OCs and SPs was in the range of 75-95 % and 70-80 % for OPs.
Reagent or procedural blanks were also extracted in the same manner and found to be devoid of
any interfering agents. Calibration of instruments, quantification of pesticide residues and limits of
detection and quantification as well as calibration standards were all set as described in chapter 4.
The limit of detection (LOD) and limit of quantitation (LOQ) for the determined pesticides in
water were 0.003 µg/L and 0.01 µg/L respectively; and 0.15 µg/kg and 0.5 µg/kg respectively in
sediment.
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6.2.6 Quality assurance and control
For each batch of 20 samples, a procedural blank, a spiked blank and a pair of matrix spiked
sample/duplicate were processed. The spiked samples contained all the 15 OCPs, 13 OPs and 9 SPs
target analytes. All reagents used during the analysis were of high quality and were exposed to the
same extraction procedures and subsequently run to check that no interfering substances were
present. No analytes were detected in the blanks. Recalibration curves were run with each sample
batch to ensure that correlation coefficient was kept above 0.99. Strict cleaning procedures were
adhered to viz: all glassware were washed with hot water and detergents and copiously rinsed with
distilled water. After drying, the glass wares were further rinsed with acetone.
6.2.7 Gas Chromatographic quantification of extracted pesticides
The final pesticide extracts were analyzed for organochlorine and synthetic pyrethroid pesticides
by Gas Chromatograph- Varian CP-3800 (Varian Association Inc. USA) equipped with
63
combiPal autosampler and Ni electron capture detector (ECD) that allowed the  detection of
contaminants even at trace level concentrations (in the lower µ g/kg range) from the matrix
to which other detectors do not respond. The procedure follows the Ghana Standard Authority
pesticide laboratory routine process of conditioning the Gas Chromatography for pesticide
quantification. The GC conditions used for the analysis were capillary column coated with VF-5
(30 m + 10 m guard column x 0.25 mm i.d, 0.25 µ m film thickness). The injector and
detector temperatures were set at 270°C and 300°C respectively. The oven temperature was
programmed as follows: 70°C held for 2 min, ramp at 25°C/ min to 180°C, held for 1 min, and
finally ramp at 5°C/ min to 300°C. Nitrogen was used as carrier gas at a flow rate of 1.0
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-1
mLmin a n d detector make-up gas of 29 mL/min. The injection volume of the GC was 1.0 µ
L. The total run time for a sample was 31.4 min.
Organophosphorus pesticides on the other hand were analyzed by Gas Chromatograph- Varian
CP-3800 (Varian Association Inc. USA) also equipped with combiPal autosampler and
pulse flame photometric detector (PFPD) that allowed the detection of contaminants even at
trace level concentrations (in the lower µ g/g range) from the matrix to which other detectors
do not respond. The GC conditions used for the analysis were capillary column coated with
VF-1701 (30 m x 0.25 mm i.d, 0.25 µ m film thickness). The injector and detector temperature
were set at 270°C and 280°C respectively. The oven temperature was programmed as follows:
o o o
70 C held for 2 min, ramp at 25 C/min to 200 C, held for 1 min, and finally ramp at 20
o o
C/min to 250 C maintained for 3.3 min. Nitrogen was used as carrier gas at a flow rate of 2.0
mLmin-1 and detector make-up gases (17.0, 14.0 and 10.0 mL/min) for hydrogen, air-1 and
air-2, respectively. The injection volume of the GC organophosphorus pesticide
determination was 2.0 µ L. The total run time for a sample was 14 min. Each sample
underwent duplicate analyses.
6.2.8 Data Analysis
6.2.8.1 Water data analysis
Simple arithmetic means, range and frequencies were employed in analyzing the lake water data.
Means of concentrations, concentration ranges and frequency of occurrence of various pesticides
were compared under flood and recession states. Number of pesticides whose residues
concentrations exceeded the WHO maximum residue limits under flooding and recession situations
were also compared.
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6.2.8.2 Determination of sediment toxicity
In determining toxicity, sediment quality criteria, which provide scientific benchmarks, or
reference points, for evaluating the potential for observing adverse biological effects in aquatic
systems (Fluck et al., 2010) is employed in this study. The approach of Fluck et al., (2010), is
adopted. Quotient of pesticide between its concentration in sediment and its quality criteria is
calculated as follows:
= ⁄ (6.1)
RQsi = Risk quotient for pesticide i in sediment
MECi = measured environmental concentration (in total sediment) for pesticide i
SQCi = sediment quality criteria for pesticide i
Calculation of mean quotient for more than one contaminant, according to Fluck et al, (2010) is
also considered as follows:
= Ʃ ⁄ (6.2)
RQm = mean risk quotient in sediment
ƩRQsi = sum of RQsi
n = number of calculated quotients
Decision rule
 If RQm or RQsi < 0.1, the risk is said to be negligible
 If 0.1 < RQm or RQsi < 0.5, the risk is said to be low, but the non-hazard of sediments has
to be checked.
 If RQm or RQsi > 0.5, the risk is non-negligible and there is the need for a detailed
diagnosis.
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Approaches to sediment quality assessment generally employ two concentration threshold values; a
lower limit of sediment quality value below which effects rarely occur and an upper value, above
which harmful effects on sediment-dwelling organisms are likely to occur (Burton, 2002).
According to Fung et al., (2005), values of the two thresholds can be used to calculate risk
quotients under the best-case (RQb) and the worst-case (RQw) scenarios as follows:
RQb = Lowest measured concentration of a chemical in sediment (6.3)
Upper limit (threshold) of sediment quality value (SQVUL)
RQw = Highest measured concentration of a chemical in sediment (6.4)
Lower limit (threshold) of sediment quality value (SQVLL)
Various institutions and nations have developed guidelines by setting their own threshold values. A
combination of two different guidelines, as a matter of propriety and legitimacy, is often used to
assess potential risks. Ghana has no established/interim national or institutional guidelines;
therefore the guidelines employed here are the protocols of Canadian Council of Ministers of the
Environment (1999) for the derivation of Canadian Sediment Quality Guidelines - CSQG (at
Threshold effect level [TEL]) and Probable effect level [PEL]); and the United States National
Oceanic and Atmospheric Administration – NOAA [at the Effects range-low (ERL) and Effects
range-median (ERM) levels, (Burton, 2002)]. TEL and ERL represent the lower threshold values
while PEL and ERM represent upper limits in their respective guidelines.
The determination of RQb and RQw present a simple way of characterizing the risk associated
with a pesticide in the sediment.  In principles, if the RQb and RQw calculated values are greater
than 1, then the pesticides in question could pose risk and therefore require remediation attention.
Conversely if the value of RQb and RQw are less than 1, the chemical is probably of little concern
and thus could be accorded a lower management or remediation priority attention. In situations
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where both risk quotients do not present the same interpretations, (e.g. RQb < 1 and RQw >1) then
a more refined risk assessment must be undertaken to ascertain the risk due to specific chemicals
(Fung et al, 2005). The toxicity assessment in this study is limited to only the organochlorine
pesticides since quality criteria are not yet developed for the other pesticide groups. Even then, not
all OCPs have established guidelines.
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6.3 Results
6.3.1 Pesticide content of lake water
There were differences in the number of pesticides recorded under flood and recession conditions.
For instance 95% of target pesticides were detected and quantified under flood condition while
70% were detected under recession situation (Appendices II and III). The reduction occurred much
more in organochlorine pesticides (OCPs) and synthetic pyrethroids (SPs), while the
Organophosphorus pesticides (OPs) detects remained approximately the same.
Frequencies of occurrence of quatified pesticides were very high under the flood condition,
especially among the OCPs and the SPs, almost all of which registered 75% and above
(Appendices II and III). Curiously however, the OP incidence during the recession was higher than
during the flood condition.
It is also noted that the concentration levels during the flood state were far higher, with as many as
12 pesticides residues exceeding the maximum level prescribed by the WHO/GSA in samples, as
against only 5 during the recession. Table 6.1 presents a vivid detail of specific and general
differences in quality of water between the two regimes. Total of mean concentrations, frequency
of occurrence and number of pesticides exceeding WHO recommended limits for the pesticide
groups under study were all higher during the flood regime. Fourteen OCPs, 9 SPs and 12 OPs
were quatified during the flood, as against 10, 4 and 11 respectively, during the recession. It is
however observed that the recess regime recorded higher frequency of occurrence of OPs. Some of
the organophosphates like dimethoate, malathion, chlorfenvinphos and profenofos also recorded
higher residue levels during the recession (Appendices I and II). However, total OP load under
flood regime (0.91µg/L), just like those of OCPs and SPs, was still higher, compared to that under
the recession regime (0.38 µg/L).
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Table 6.1: Comparison of pesticide water quality during occasional flooding of farmlands and
period of recession
Flood Recession
Pesticide
group MCT Range Average MRLe MCT Range Average MRLe
(µg/L) (µg/L) Frequency
(µg/L) Frequency (µg/L)
(%) (%)
OCPs 15.220 0.01-16.79 89.6 6 0.497 0.01-0.269 17.5 2
SPs 1.470 0.01-2.135 85 6 0.127 0.01-0.37 23.8 1
OPs 0.910 0.01-1.12 20 0 0.382 0.01-0.158 31 2
Total 17.60 0.01-16.79 NA 12 1.01 0.01-0.370 NA 5
MCT = Total of mean concentrations of all residues in a pesticide group
MRLe = Number of residues Exceeding WHO MRL
Flood = Period during which water level in the Afram Lake rises and covers part of the bank
that is cultivated for crop production.
Recess = Period during which water in the Afram Lake assumes normal level following flood regime,
exposing land with high moisture content suitable for cultivation of short-maturing crops.
NA = Not applicable
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6.3.2 Pesticide content and toxicity of sediment
Concentration of pesticide residues in sediment are presented in Table 6.2. The OCPs recorded the
highest average concentration, with the average of the concentration of all OCP pesticides as 11.26
µg/kg. Followed by the organophosphates (7.85 µg/kg) and pyrethroids (5.84 µg/kg). Dimethoate,
though less frequently encountered recorded the highest concentration of 58.9 µg/kg. Gamma
chlordane recorded the next highest concentration of 42.69 µg/kg, followed by p,p-DDD, p,p-DDE,
γ-lindane, and δ-lindane with respective concentrations of 35.76 µg/kg, 31.00 µg/kg, 14.67 µg/kg
and 9.39 µg/kg. Organophosphorus pesticide residues, with the exception of dimethoate registered
only trace concentrations. They were however more frequently encountered than the other group of
pesticides.  Concentration ranges of OCPs, SPs and OPs are 1.55-42.69 µg/kg, 1.96-13.18 µg/kg
and 1.41-58.90 µg/kg respectively.  The top ten most frequently encountered pesticides were γ-
lindane, chlorpyrifos,profenofos, cyfluthrin, chlorfenviphos, fenitrothion, ethoprophos, p,p-DDD,
fenvalerate and parathion, with  incidence rate ranging from 71% - 97%.
The calculated risk quotients of some OCPs are presented in Table 6.3 The risk quotient under
best-case scenario (RQb) estimates of p,p-DDD, γ-chlordane, dieldrin, and endrin were all below 1
based on both CSQG and NOAA. Gamma-lindane was the only chemical whose risk quotient
under best case scenario was more than 1 based on both CSQG and NOAA. It is also noted that,
with the exception of dieldrin, the risk quotients of all the pesticides in question, under worst case
scenario were greater than 1 based on both CSQG and NOAA. The risk quotients of P,P’-DDD,
p,p-DDE, γ-chlordane, and γ-lindane under the worst case scenario had very high values (greater
than 10) based on both CSQG and NOAA.
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Table 6.2: Concentration of pesticide residues in sediment
Pesticides Mean ± SD Range Frequency
(µg/kg) (µg/kg) (%)
Organochlorines
β-HCH 2.16 ± 0.9 0.50-3.50 53.0
γ-HCH 14.67 ±8.4 1.52-38.95 97.0
δ-HCH 9.39 ±12.9 0.50-55.00 47.0
Heptachlor 4.10 4.10 3.0
Aldrin 2.88 ±4.6 1.40-17.60 37.5
γ-Chlordane 42.69 ± 27.3 1.60-95.00 47.0
α-endosulfan 2.18 ±0.5 1.70-3.50 37.5
p,p'-DDE 31.00 ±9.7 14.80-49.80 37.5
Dieldrin 1.55 ±0.4 1.20-2.50 37.5
Endrin 4.55 ±0.1 4.40-4.80 25.0
Beta endosulfan 5.20 4.00-6.40 6.0
p,p'-DDT 4.60 ±2.0 0.50-8.80 37.5
p,p'-DDD 35.76 ±29.5 3.69-91.55 72.0
Endosulfan sulfate 2.12 ±0.7 1.00-3.30 50.0
Methoxychlor 6.10 ±1.8 5.00-9.60 19.0
Pyrethroids
Allethrin 6.35 ±3.5 0.77-9.30 15.6
Bifenthrin 13.18 ±1.0 12.00-15.00 37.5
Fenpropathrin 3.43 ±0.8 2.48-5.00 44.0
Lamda-cyhalothrin 4.35 4.40 6.0
Permethrin 7.67 ±3.6 1.71-11.70 15.6
Cyfluthrin 6.15 ±5.1 0.50-16.20 78.0
Cypermethrin 5.41 ±3.2 1.00-12.60 67.0
Fenvalerate 4.08 ±2.5 0.50-8.20 72.0
Deltamethrin 1.96 ±1.8 0.50-8.10 44.0
Organophosphate
Methamidophos 5.35 ±3.1 0.98-9.00 13.5
Ethoprophos 2.26 ±1.0 1.17-5.30 73.1
Phorate 2.57 ±1.9 0.52-8.80 71.0
Diazinon 1.43 ± 1.1 0.50-5.00 69.2
Fonofos 1.41 ± 1.7 0.50-7.50 61.5
Dimethoate 58.90 ± 3.5 57.00-63.00 5.8
Pirimiphos-methyl 1.48 ±0.9 0.50-3.58 57.7
Chlorpyrifos 9.50 ±14.8 0.51-69.00 94.0
Malathion 1.73 ±1.1 0.50-3.00 32.7
Fenitrothion 3.00 ±1.5 0.85-6.60 77.0
Parathion 3.40 ±2.5 0.52-8.42 71.0
Chlorfenvinphos 6.00 ±8.4 0.56-50.00 77.0
Profenofos 5.00 ±3.9 0.51-17.45 80.8
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Table 6.3: Estimated risk quotients of organochlorine pesticides concentrations in sediments (OCPs)
based on Canadian Sediment Quality Guideline (CSQG) and National Oceanic and
Atmospheric Administration NOAA) guidelines.
NOAA CSQG
Pesticide OCPc (µg/kg) (µg/kg) 1>RQb>1 0.1<RQw<1 1<RQw<10 RQw>10
ERL ERM TEL PEL
p,p-DDD 3.69-91.55 2.0 20 3.54 8.51 ○●
○●
p,p-DDE 14.8-48.8 2.0 27 1.42 6.8 ● ○
○●
p,p-DDT 0.50-8.80 1.0 7 - - ● ●
γ-chlordane 1.60-95.0 0.5 6 4.5 8.9 ○●
○●
Dieldrin 1.20-2.50 0.02 8 2.85 6.67 ○●
○ ●
Endrin 4.40-4.80 0.02 8 2.67 62.4 ○● ○
●
γ-Lindane 1.52-49.0 0.32 1 0.94 1.38
○● ○●
Risk quotients were calculated based on two sediment quality criteria (○ = CSQG; ● = NOAA)
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6.4. Discussion
6.4.1 Variation of pesticide content of Lake Water under flood and recession regimes
Details of pesticide content of lake water from the Afram arm of the Volta Lake (AVL) during
periods when lake flooded agricultural fields and when it receded to its normal level in the lake are
presented in Appendices I and II. Comparison of pesticide water quality during both regimes is
summarized in Table 6.1. Hundred per cent of water samples taken under both flood and recess
regimes contained more than one pesticide residue. All pesticides under investigation were
detected in water samples (except alpha-lindane). Thus 37 different pesticide residues were
quantified in the water samples and this underscores the application of a wide range of pesticides in
the agricultural fields along the banks of AVL.
Occasional flooding of the agricultural fields by the lake water is perceived to have implication on
the occurrence and level of concentration of pesticide residues of water hence the decision to assess
pesticide content of water under both regimes. From the results in Appendices I and II, 35 different
pesticides were quantified during flood regime, as compared to 25 under recess regime. An average
frequency of occurrence of any pesticide during flood regime was 65% compared to 24.1% during
recess (Table 6.1). The range of concentration and pesticide load (total of mean of concentrations
of all pesticides) under the two regimes were 0.01 µg/L – 16.79 µg/L and 17.60 µg/L respectively
for flood period; and 0.01 µg/L – 0.37 µg/L and 1.01 µg/L respectively for the recess (Table 6.1).
Whereas as many as 12 pesticide residues in water samples exceeded the WHO MRL during the
flood, only 5 exceeded during the recess. Higher frequency of occurrence and concentration of
pesticide residues implies associated higher health risk with water consumption during the flood
regime. Unfortunately this is the only source of potable water for most of the communities along
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the AVL. Even the communities in which there is provision of boreholes, individuals still prefer
water from the lake since majority of them complain about high salt content of borehole water.
Recession of water in the lake was previously predictable hence farmers could plan when to
cultivate the immediate banks of the lake (‘drawdown’ areas) and harvest in time before water
levels rose. Within the past decade however, farmers have confirmed that periods of rise and fall in
the Afram arm of the Volta Lake is no longer predictable; obviously due to climate variability.
Farming in the ‘drawdown’ areas has therefore become a risky commercial and subsistence venture
since farms could be flooded before maturity of food crops. Plates 4a - 4c present scenarios of
events in typical drawdown areas. In such situations, agrochemicals on farmlands dissolve in the
water causing their levels to be elevated. This primarily explains high incidence and concentration
levels of even non-persistent second generation pesticides like pyrethroids and organophosphates.
For instance, methamidophos recorded 0.75 µg/L; cypermethrin, 0.637 µg/L; fenpropathrin, 0.341
µg/L; deltamethrin, 0.234 µg/L;  permethrin, 0.066 µg/L and allethrin 0.051 µg/L during flooding,
all exceeding their WHO maximum residue limits (MRL). The most ubiquitous of the pesticides
under flood regime were allethrin, bifenthrin, permethrin, deltamethrin, β-HCH, γ-HCH, δ-HCH,
aldrin endrin p,p’-DDD, endosulfan sulfate and methoxychlor, all of which registered 100%
incidence rate. Dieldrin and endrin, degradation compounds of aldrin had higher concentrations
than their parent compound, aldrin; suggesting the presence of aldrin was due to old inputs and
confirming the ban on use of this pesticide in Ghana. However, the general high concentrations of
both parent and metabolites seem to indicate some level of current inputs that needs to be further
investigated.
The concentration of some pesticides (chlorfenvinphos, dimethoate and cypermethrin), even during
the recess regime exceeded MRLs and gives cause for concern since water from the lake is the only
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reliable source for all purposes, including drinking. Water from the Afram arm as well as water
from the upper reaches of the Volta Lake all flow down into the Kpong water head where water is
treated and distributed for domestic consumption in the greater part of Greater Accra Region.
Therefore, quality of water from the Kpong water works, by implication is a function, to some
extent, of the quality of water that it receives and is treated.  It is therefore necessary that the Volta
Lake as a whole is protected from potential pollution and contamination that can result from
anthropogenic activities taking place along its course.  The results from this study under the recess
regime agree with earlier investigation into OCP levels in other parts of the Volta Lake by Ntow
(2005). So also are the results in agreement with other local works done by Darko et al., (2008) on
Lake Bosomtwi, Kuranchie-Mensah et al., (2012) and Fianko et al., (2011) on Densu River.
However, results under flood regimes are several folds higher than their reported values. Pesticide
pollutions of fresh water bodies in Ghana are primarily due to agricultural activities in their vicinity
as reported by various researchers including Darko et al., (2008); Adu-Kumi et al., (2010); Botwe,
Ntow and Nyarko (2012); Fianko et al., (2012) and Afful et al., (2013). Pollution of the water
bodies, according to Ntow (2005), is facilitated by the short distances between agricultural fields
and waterways that increase the probability of agro-chemicals reaching the water bodies via run-
offs.
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6.4.2 Level of organochlorines in sediment
Fifteen organochlorine pesticide residues were detected in sediment samples from AVL (Table
6.2). The general concentration range was 0.5 µg/kg - 95.0 µg/kg, while the mean concentration
range was 1.55 µg/kg – 42.69 µg/kg. The highest concentration recorded in a single sample as well
as for the mean was for Gamma-chlordane. The most frequently encountered OCPs were γ-HCH
(97%), p,p’-DDD (72%), β-HCH (53%) and endosulfan sulfate (50%). Frequencies of occurrence
of the rest were below 50%. While the mean concentration range in the current study lie between
that quoted by Fianko et.al., (2011) for 14 OCPs in sediment from River Densu (0.10 µg/kg -
163.00 µg/kg) and that of Kuranchie-Mensah et al., (2012) for Lake Bosomtwi (0.03 µg/kg - 10.98
µg/kg, it was below what was reported by Fung et al., (2005) for Pearl River Delta in China (1.4
µg/kg - 600 µg/kg).
6.4.2.1 DDT and its metabolites (p,p’-DDE and p,p’-DDD) in Lake bed sediment
The mean and range of concentrations of p,p’-DDT, p,p’-DDE and p,p’-DDD as shown in Table
6.2 are 4.60 µg/kg, 0.50-8.80 µg/kg; 31.00 µg/kg, 14.80-49.80 µg/kg and 35.76 µg/kg, 3.69-91.55
µg/kg respectively. The result is an indication of the rate of degradation of DDT in typical tropical
water with hot climatic conditions (Jiries, et al., 2006). The current trend of higher p,p’-DDE and
p,p’-DDD relative to p,p’-DDT was also observed by Ntow (2005) in sediment from the Volta
Lake and Darko et al., (2008) in sediment from Lake Bosomtwi, as well as by Pazou et al., (2014)
from sediment of Nokoue and Cotonou Lagoons in Benin. Whereas the concentration levels
recorded in this study were lower than those reported by Ntow (2005), they were higher than those
reported by Darko et al., (2008). The low DDT:DDE and DDT:DDD ratios of 0.15 and 0.13,
respectively is an indication that current exposure levels primarily come from previous
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contamination and environmental persistence rather than from recent applications. DDT in the
environment gradually breaks down into DDD and DDE which are more stable. As a result, when
the input of DDT into the environment ceases, the levels of its metabolites; DDE and DDD will be
higher than that of the parent DDT (Bossi, 1992) as it is in the present study. The higher
concentration of p,p’-DDD, relative to p,p’-DDE in sediments from the Afram arm of the Volta
Lake indicates the degradation pathway is from DDT to DDD by reductive dechlorination
(Quensen et al.,1998; Yao et al., 2006).
Due to its environmental persistence and health hazards, DDT and formulations containing its
metabolites have been banned from agricultural use under the Stockholm convention (FAO, 2006)
to which Ghana is a signatory. The present investigation to a large extent, confirms the restricted
use of DDT for agricultural purposes in Ghana. There are however challenges with enforcement of
the ban in the country due to lack of adequate logistics for training and proper monitoring
programme (EPA Ghana, 1999). There is therefore evidence of current use of DDT in isolated
cases in the country. For instance, Fianko et al., (2011) reported high DDT concentrations in both
water and sediment from parts of the Densu River basin. Williams, (2013) also recorded extremely
high concentrations of DDT in sediment of Tarkwa bay lagoon in Lagos, Nigeria, indicating the
challenge effective banning of the use uf DDT goes beyond the boundaries of Ghana.
6.4.2.2 Endosulfan and its metabolite endosulfan sulfate in Lake Sediment
Endosulfan was present in the Afram arm of the Volta Lake sediment mainly as α-endosulfan.
Though its mean concentration was lower (2.18 µg/kg), compared to the β-isomer (5.20 µg/kg), it
was frequently encountered (37.5% incidence rate) more than the β-isomer (6%). The metabolite
endosulfan sulfate had a mean concentration of 2.12 µg/kg and its incidence rate of 50% was
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higher than that of the parent compounds. The result indicates that historically used endosulfan
pesticides are being converted to the main metabolite endosulfan sulfate (Dem et al., 2007)
meanwhile, there are still sporadic new inputs of endosulfan; mainly α-endosulfan. The range of
concentration of endosulfan sulfate in the sediment of AVL (1.00 – 3.30 µg/kg) is compared to that
of Lake Victoria (0.82 µg/kg – 6.62 µg/kg,) as reported by Wasswa et al., (2011) and was lower.
The mean concentration of each of the compound was however observed to be 10 to 30 folds
higher than what was reported by Ntow (2005) in sediments from some other parts of the Volta
Lake. Current higher values compared to what was reported by Ntow (2005) signifies
intensification of agricultural activities along the banks of the Volta Lake in general, and AVL in
particular; as well as overreliance and inappropriate use of agro-chemicals for maximum output.
This view was confirmed by the farmers who explained that their primary occupation has shifted
from fishing to fruits and vegetable farming since no amount of fishing efforts produces
corresponding yield. Cultivation of fruits and vegetable is possible all-year round and yields better
economic benefits. Fishing has therefore become a supplementary livelihood.   Results in this study
however agree with recorded values from Densu River sediment by Kuranchie-Mensah et al.,
(2012).
6.4.2.3 Concentration of lindanes and the drins (aldrin, dieldrin, endrin) in sediment
The mean concentrations of γ-HCH, δ-HCH and β-HCH were 14.67 µg/kg, 9.39 µg/kg and 2.16
µg/kg respectively. This trend of concentration follows that recorded in July, 2002 by Fernandez-
Bringas et al., (2008) in Mexico (γ-HCH-0.43 ng/g; δ-HCH-0.37 ng/g and β-HCH- 0.16 ng/g) and
locally by Kuranchie-Mensah et al., (2012) at Weija (γ-HCH -0.555 µg/kg and δ-HCH – 0.140
µg/kg) and Nsawam (γ-HCH -0.608 µg/kg and δ-HCH – 0.095 µg/kg). The range of concentration
of lindanes in the sediment of AVL appears high (Table 6.2) when compared with work done by
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Doon et al., (2002) in Taiwan (0.57 µg/kg – 14.1 µg/kg) and Sun et al., (2010) in Huaihe River,
China (1.95 µg/kg – 11.05 µg/kg).
The use of lindanes in general is banned in Ghana due their environmental resistance and health
implications. Gamma HCH in particular was marketed in Ghana as Gammalin 20 until 2007 when
its use was discontinued (Kuranchie-Mensah et al., 2012). Awumbila and Bokuma, (1994) reported
it was the most extensively used pesticide on farms and for animal husbandry in Ghana. The high
concentration of γ-HCH therefore continues to persist in the environment. In the case of the AVL,
the absence of α-HCH, coupled with the high γ-HCH: β-HCH (6.8) suggests that either pure
lindane (γ-HCH), rather than technical lindane is still in use or the degradation of Lindane to the
more stable β-HCH in the sediment is very slow.
The ratios of endrin:aldrin (1.6) and endrin:dieldrin (2.9) suggest the presence of these pesticides in
the sediment was due to old inputs. The use of the drins, just like the lindanes and the DDTs have
been banned. It is therefore not surprising to encounter degradation products of aldrin (dieldrin and
endrin) in significant concentrations in the environment. The low dieldrin:aldrin ratio (0.5)
however indicates the possibility of fresh aldrin usage. Aldrin itself strongly adsorbs to sediment
particles for a long time (Nollet, 2000). This probably also accounts for its high concentration in
the sediment.
6.4.3 Concentrations of organophosphorus pesticides and synthetic pyrethroids in sediment
The concentration levels of organophosphorus pesticide and synthetic pyrethroid residues detected
in the sediment of the AVL are listed in Table 6.2. All 9 target pyrethroids (SPs) and 13
organophosphorus pesticides (OPs) were detected. The general concentration range for the OPs
was 0.50 µg/kg – 63.00 µg/kg while the mean concentration range was 1.41 µg/kg – 58.00 µg/kg.
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Whereas the highest concentration measured in the samples (63.00 µg/kg) was for chlorpyrifos, the
highest mean concentration (58.00 µg/kg) was recorded for dimethoate. Comparing their incidence
rates, chlorpyrifos had 94% as against only 5.8% for dimethoate. For the pyrethroids, the general
concentration range was 0.50 µg/kg – 16.2 µg/kg while the mean concentration range was 1.96
µg/kg – 13.18 µg/kg. The highest SP level measured in the sediment (16.20 µg/kg) was recorded
for cyfluthrin whilst the highest mean concentration (13.18 µg/kg) was recorded for bifenthrin.
Cyfluthrin was the most frequently encountered, with incidence rate of 78%, followed by
fenvalerate (72%). The mean concentration range of 1.41 µg/kg – 58.00 µg/kg recorded for OPs in
Afram sediment in this study was higher than that reported by Afful et al., (2013) in sediments of
Weija Lake in Ghana (0.15 µg/kg – 6.6 µg/kg). In their case, Afful et al., (2013) measured the
highest mean concentration for permethrin while bifenthrin recorded the highest in this study. In
Ghana, SPs and OPs concentrations are rarely studied in water and sediments matrices as they are
in cash crops like cocoa where their levels have been studied by many researchers including
Blankson,(2011), Boakye, (2012), Frimpong et al., (2012a, and 2012b), and Frimpong et al.,
(2013). With the exception of the pyrethroid levels recorded by Frimpong et al., (2012), all
reported concentration levels for SPs and OPs in the cocoa beans were either in the same range or
higher than the levels reported for sediment in this study. Even though the OPs and SPs have
higher mammalian toxicities compared to the OCPs, these second generation pesticides (OPs and
SPs) have become the recommended and preferred agro-pesticides because of their efficacy, short
persistence and ease of degradability in the environment. For instance, only a dose of 10 -40 g of
active pyrethroid ingredient is needed to be efficacious on a land area of one hactare (Afful et al.,
2013). The presence of a wide spectrum of pyrethroids organophosphorus pesticide residues in
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sediments from AVL in this study underscores increasing diversification in the use of these
pesticides.
6.4.4 Lake Sediment risk and toxicity assessment
A summary of the result of an assessment of potential environmental risk associated with
organochlorine pesticide residues measured in sediment of AVL in this study is presented in Table
6.3. The sediment quality values used in the calculation of risk quotients were the Canadian
Sediment Quality Guidelines (CSQG) and the United States National Oceanic and Atmospheric
Administration guidelines (NOAA) (Burton, 2002). Only contaminants for which lake sediment
quality values have been established were assessed.
Scrutiny of the results in Table 6.3 reveals that pesticides with clearly defined risk status are p,p’-
DDE, γ-HCH and dieldrin. For γ-HCH, risk quotients based on both CSQG and NOAA are greater
than one (1) under best and worst case scenarios (RQb and RQw respectively). For p,p’-DDE, the
risk quotient (RQ) is greater than one under best and worst case scenarios based on CSQG only.
Concentrations of these contaminants can therefore be said to reach toxicity levels whereby they
can impact on health of sediment and benthic organisms in particular, and affect the integrity of the
AVL ecosystem as a whole. These pesticides in the sediment may therefore require priority
attention for some control measures. Similar studies carried out by Fung et al., (2005) on sediment
of Pearl River in China listed DDT (and its metabolites), dieldrin and endrin as serious
contaminants with RQs under best case scenarios greater than 10. Nemr et al., (2012) also listed
DDT, chlordane and endrin with RQs above 10 in sediment from Egyptian Mediterranean coast.
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In the case of dieldrin, the RQ based on CSQG is less than unity under both best and worst case
scenarios. Hence this pesticide is of little concern and therefore needs no priority remediation
attention. The risk quotient under worst case scenario (RQw) for p,p’-DDT, p,p’-DDD and endrin
were all above 10 (with the exception of p,p’-DDT whose RQw is less than 10 but greater than 1)
indicating these pesticides may also be of concern to the integrity of the Afram arm of the Volta
Lake ecosystem. It is observed, however, that the risk quotients of these pesticides were all less
than one under best case scenarios. Hence the actual risks posed by these contaminants (p,p’-DDT,
p,p’-DDD and endrin) need further investigation.
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CHAPTER SEVEN
PESTICIDE DISTRIBUTION IN TISSUES OF FISH SPECIES,
HEALTH RISK ANALYSIS AND BIOCONCENTRATION
OF PESTICIDES IN AQUATIC FLORA
7.1 Backgound
A high proportion of pesticides developed for agricultural and other uses have been recognized to
be highly toxic to fish and other aquatic species (Bhalchandra et al, 2001; Visvanathan et al., 2009;
Muthukumaravel et al., 2013). Although the aqueous concentrations may not be directly toxic,
these chemicals, especially the organochlorine pesticides (OCPs) may bioaccumulate and
biomagnify in aquatic organisms to present health concerns. Generally, fish have the ability to
bioconcentrate pesticides from aquatic medium and is therefore an important bioindicator of level
of pesticide pollution in aquatic media. Pollution of fish also contaminates the food (Zhou et al.,
2007). Since fish is an important source of protein globally, its health is also of global concern.
Consumption of contaminated fish is reported to be one important pathway of human exposure,
particularly to the OCPs (Muralidharan et al., 2008). Due to its availability and affordability, fish
constitutes an important source of animal protein in Ghana as well. Literature, however, indicates
fish in Ghana are not always free from appreciable levels of pesticides (Adu-Kumi et al., 2010).
Many studies on exposure of pesticides to humans suggest health implications. For instance health
effects associated with OCPs include reproductive failures, birth defects, endocrine disruption,
immune system dysfunctions and carcinogenicity (Bouman, Coetzee & Schutte, 1990; Olea et al.,
1999; Ayedemi et al., 2008). Pyrethroids, among their numerous health effects, are known to be
both neuropoisons and endocrine disruptors. They have been linked to disruption of the endocrine
system that adversely affect reproduction and sexual development, interference with immune
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system and increased chances of breast cancer (Chemicalwatchfactsheet, n.d). Epidemiological
studies on organophosphorus pesticides (OPs) have suggested associations between OPs exposure
and reproductive disorders like infertility, birth defects, adverse pregnancy outcomes and perinatal
mortality (Peirris-John & Wickremasinghe, 2008). Organophosphorus pesticides, as a matter of
fact are known to be highly toxic and hence human exposure to them is undesirable. They are
mutagenic, teratogenic and a large number of modern-day diseases of nervous and immune system
of mammals, like mad cow disease, Gulf war syndrome, Parkinson’s disease and multiple sclerosis
can be linked to pesticides of this group (Ragnarsdottir, 2000).
Environmental concentrations of pesticides other than OCPs have rarely been studied in Ghana.
Most studies only analyse OCPs distribution in fish muscle. However, distribution of pesticides in
tissues such as liver, gills and skin; which could provide more clues about the pathways along
which pesticide bioaccumulation occurs, and reflect environmental conditions has not received
adequate attention. This chapter therefore examines the distribution of OCPs, OPs and SPs residues
in tissues of four fish species from the Afram arm of the Volta Lake as a reflection of the state of
pesticide pollution of the river. Also, the potential health risk posed to humans upon consumption
of these fish is evaluated. Furthermore, pesticide content of two most common submerged/partially
submerged aquatic weeds Ceratophyllum demersum and Nymphaea lotus are determined.
According to Lass, (2015) and FAO (2015) these two aquatic plants are excellent sources of plant
food for fish. Toowomba, (2000) reported that Ceratophyllum sp. was second among aquatic
macrophytes consumed by fishes in Polish inland waters and most abundant in the gut of fishes
caught in Sri Lanka. In view of this, it is important to assess pesticide content of these plants and
determine their bioconcentration factors. Bioconcentration factor (BCF) represents the ratio of
pesticide concentration in an aquatic plant relative to that in the aqueous medium and gives an
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indication of the ability of an aquatic plant to concentrate chemicals into its system from the
surrounding water.
7.2 Materials and Methods
7.2.1 Collection of fish and aquatic plant samples
Four species of fish: Tilapia zilli, Oreochromis niloticus, Bagrus bayad and Chrysichthys
nigrodigitatus were freshly bought from fishermen upon their immediate return from fishing
expedition on the Afram arm of the Volta Lake (Plates 3a – 3d). These species were selected based
on their abundance and availability all-year round. Moreso, they are a delicacy and have high
consumption rate among Ghanaians. The purchases were done at four different locations along the
Afram arm of the Volta Lake (Dedeso, New Jerusalem, Adawso and Kotoso) on 7th and 8th of
January, 2014. The fish samples were wrapped in pre-cleaned aluminium foil, packaged into zip-
locked plastic bags, stored on ice and transported to the Department of Marine and Fisheries
Sciences of the University of Ghana where they were identified by fish taxonomic experts.
Samples were subsequently washed thoroughly with distilled water and promptly taken through
pre-extraction preparation.
Ceratophyllum demersum and Nymphaea lotus (Plates 3e and 3f respectively) were encountered at
only one location. Whereas Ceratophyllum demersum is completely submerged Nymphaea lotus, is
a floating leaved plant. For Nymphaea lotus, only submerged parts of were harvested. This was
done to ensure that source of pesticide to these aquatic plants was wholly from the aquatic medium.
The two aquatic plants were identified in the Ghana Herbarium, Department of Botany of
University of Ghana. Thereafter, they were thoroughly washed in three changes of distilled water,
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put in zip-locked plastic bags and stored in a deep freezer at the laboratory of Ghana Standards
Authority.
7.2.2 Chemicals reagents
All chemicals and reagents used in this study were of purest grade and are listed in appendix I
7.2.3 Preparation of fish tissue samples for pesticide extraction
The fish sample preparation was done at the Department of Marine and Fisheries Sciences. All fish
samples were weighed on a weighing balance, and their total length (snout to end of tail) taken
with a metre rule. The standard lengths (snout to fork of tail) of fish samples with forked tails
(Bagrus bayad and Chrysichthys nigrodigitatus) were also measured.  Scales of Tilapia zilli, and
Oreochromis niloticus were removed while the skin of Bagrus bayad and Chrysichthys
nigrodigitatus were taken off. Three body tissues: muscle, gills and liver were taken from
individual fishes of each species. Using dissecting kits, each fish was dissected with a scalpel and
the liver carefully removed and weighed. The operculum was then cut off with a pair of scissors
and the gill subsequently removed and weighed. Finally, a sizeable filleted muscle of each fish was
taken by dissecting between dorsal and ventral portions of the fish and minced using a warring
blender. Plates 6a -6d show some of the the fish tissue sample. The minced muscle tissue was then
weighed. By this means, a total of one hundred and twenty tissue samples were obtained from
selected forty whole fish samples comprising: 10 each of Chrysichthys nigrodigitatus, Bagrus
bayad, Tilapia zilli, and Oreochromis niloticus. All prepared samples were wrapped in pre-cleaned
aluminium foils, labeled and stored in a deep freezer at -200C at the Ghana Standard Authority
laboratory.
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7.2.4 Extraction and clean-up of extracted Samples
7.2.4.1 Extraction and clean-up of pesticides from fish samples
A modified method of Sun et al., (2005) for the extraction of fish tissue samples was used. Ten
grammes wet weight of a fish tissue sample was weighed into a nalgelene jar and 40 mL of
acetonitrile added (In the case of liver, when a tissue sample was not up to 10 g, 4 mL of solvent
for each gramme was used for extraction). The mixture was marcerated for 2 minutes using IKA
ultra Turrax homogenizer and then centrifuged at 3000 revolutions per minute (rpm) (Hermle Z
300, jouan CR3i multifunction) for 3 minutes. The supernatant was filtered through 2 g of
anhydrous magnesium sulphate and acetonitrile was added to make up to 50 mL in a round
bottomed flask. This was then condensed in a rotary evaporator to about 1 mL. Silica SPE
cartridge, (1000mg/6 mL) capped with 2g anhydrous magnesium sulphate was conditioned with 10
mL acetonitrile and the cartridge not allowed to dry. Two portions of 10 mL acetonitrile were then
used to wash the concentrated extract onto the SPE cartridge mounted on visiprep vacuum
manifold and the eluate collected at a flow rate of 3 drops per second into a 50 mL round bottomed
flask. Differences in colour of liver extract (in flask 7d) and the eluate (in flask 7f) of plate 7
emphasises the effectiveness of solid phase extraction (SPE) cleaning process. The eluate was
concentrated just to dryness by rotary film evaporator (Buchi Rotovapor R.210) at a pressure of 77
mbar and at a temperature of 440C. The concentrate was re-dissolved in 1 mL ethyl acetate, frozen
for 1 hour and centrifuged at 3000 rpm for 5 minutes in order to settle out any fat/oil left in the
sample. The supernatant was then taken into a 1 mL standard opening vial for quantitation by GC-
ECD and GC-PFPD.
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7.2.4.2 Extraction and clean-up of pesticides from aquatic plants
The aquatic weeds were removed from freezer and allowed to thaw. Five hundred gramme sample
sizes each of Ceratophyllum demersum and Nymphaea lotus were separately weighed and
homogenized in a conventional food processor. Ten grammes sub-samples were then taken for
extraction of pesticides.
The method by Takatori et al., (2009) was adapted for extraction and clean-up of pesticides. Ten
grammes sub-samples of homogenized aquatic weeds were put into a 50 mL polypropylene tubes
and 10 mL acetonitrile added. The content is homogenized by vortex at high speed for 1 minute.
Four grammes of anhydrous magnesium sulphate and 1 g of sodium chloride were then added and
vigorously shaken for another minute. The mixture was then centrifuged for 5 minutes and 4 mL
supernatant organic layer taken. Supelclean Envi-Carb/LC-NH2 SPE cartridge (500mg/500mg, 6
mL size) was conditioned with 10 mL acetonitrile and allowed to run down but the cartridge was
not allowed to dry. The 4 mL supernatant from the centrifuge process was then loaded onto the
conditioned solid phase extraction cartridge. This was then eluted with two portions of 5 mL
acetonitrile into a pear-shaped 50 mL flask, using a 12 port visiprep vacuum manifold. The elution
was done at the rate of 3 drops per second. The eluate was evaporated to dryness using Buchi
rotary vacuum evaporator at 40oC and 77 mbar. The concentrate was re-dissolved in 2 mL ethyl
acetate and transferred into a 2 mL standard opening vial prior to GC-ECD and GC-PFPD
analyses.
7.2.5 Recovery test of the extraction method
A duplicate of samples that have already been analysed were spikes with 0.05 mg/kg of standard
pesticide mixtures and subjected to the same extraction process in order to determine recovery. The
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recovery was done in replicates, at another fortification level of 0.01 mg/kg. The values, expressed
in percentages were calculated from chromatograms as follows:
% Recovery = Pesticide (mg/kg) recovered from fortified sample x 100
Amount of pesticide (mg/kg) added
The recoveries of the pesticides in fish matrices were within the range of 75% - 110% for most of
the pesticides analysed whilst that for the aquatic weeds was 70% - 105%. Reagent or procedural
blanks were also extracted same and found to be devoid of any interfering agents. Calibration of
instruments, quantification of pesticide residues and limits of detection and quantification as well
as calibration standards were all set as described in chapter 4. The limit of detection (LOD) and
limit of quantification (LOQ) of the GC for the pesticides in fish and aquatic plants were 0.15
µg/kg and 0.5 µg/kg.
7.2.6 Quantification of extracted pesticides by Gas Chromatograph
The final extracts were analyzed for organochlorine and synthetic pyrethroid pesticides by Gas
Chromatograph- Varian CP-3800 (Varian Association Inc. USA) equipped with combiPal
63
autosampler and Ni electron capture detector (ECD) that allowed the  detection of
contaminants even at trace level concentrations (in the lower µ g/kg range) from the matrix
to which other detectors do not respond. The GC conditions and the detector response were
adjusted so as to match the relative retention times and response as spelt out by Japanese
analytical methods for agricultural chemicals. The GC conditions used for the analysis were
capillary column coated with VF-5 (30 m + 10 m guard column x 0.25 mm i.d, 0.25 µ m film
thickness). The injector and detector temperature were set at 270°C and 300°C, respectively.
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The oven temperature was programmed as follows: 70°C held for 2 min, ramp at 25°C min-1 to
° -1180 C, held for 1 min, and finally ramp at 5°C min to 300°C. Nitrogen was used as carrier gas
-1
at a flow rate of 1.0 mLmin a n d detector make-up gas of 29 mLmin-1. The injection volume
of the GC was 1.0 µ L. The total run time for a sample was 31.4 min.
Organophosphorus pesticides on the other hand were analyzed by Gas Chromatograph- Varian
CP-3800 (Varian Association Inc. USA) also equipped with combiPal autosampler and
pulse flame photometric detector (PFPD) that allowed the detection of contaminants even at
trace level concentrations (in the lower µ g/g range) from the matrix to which other detectors
do not respond. The GC conditions used for the analysis were capillary column coated with
VF-1701 (30 m x 0.25 mm i.d, 0.25 µ m film thickness). The injector and detector temperature
were set at 270°C and 280°C respectively. The oven temperature was programmed as follows:
70°
1
C held for 2 min, ramp at 25°C min- to 200°C, held for 1 min, and finally ramp at 20°C
min-1 to 250°C maintained for 3.3 min. Nitrogen was used as carrier gas at a flow rate of 2.0
mLmin-1 and detector make-up gases (17.0, 14.0 and 10.0 mLmin-1) for hydrogen, air-1 and
air-2, respectively. The injection volume of the GC organophosphorus pesticide
determination was 2.0 µ L. The total run time for a sample was 14 min. Each sample
underwent duplicate analyses.
7.2.7 Quality assurance of method
For each batch of 20 samples, a procedural blank, a spiked blank and a pair of matrix spiked
sample/duplicate were processed. The spiked samples contained all the 15 OCPs, 13 OPs and 9 SPs
target analytes. All reagents used during the analysis were of high quality and were exposed to the
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same extraction procedures and subsequently run to check that no interfering substances were
present. No analytes were detected in the blanks. Recalibration curves were run with each sample
batch to ensure that correlation coefficient was kept above 0.99. Strict cleaning procedures were
adhered to viz: all glassware were washed with hot water and detergents and copiously rinsed with
distilled water. After drying, the glass wares were further rinsed with acetone.
7.2.8 Data Analysis
7.2.8.1 Health Risk Estimation
Health risk assessment was done as described in chapter 5. The estimated lifetime exposure dose
(mg/kg/day) was obtained by multiplying the residual pesticide concentration (mg/L or mg/kg) in
the food of interest by the daily food consumption rate (L/day or kg/day) in a country, and dividing
the product by the body weight (kg). The lifetime exposure dose is then divided by the Acceptable
Daily Intake (ADI) to obtain a health index (HI) that is a parameter in judging health risk
associated with consumption of food with certain level of pesticide. The daily food consumption
rate of a food item is equivalent to the per capita consumption of that food item. The per capita
consumption of fish in Ghana, as reported by the Ministry of Food and Agriculture, MoFA (2011)
is 30.2 kg/head/year which is equivalent to 0.082 kg/person/day.
Dietary exposure = (Food chemical concentration (mg/kg) × Food consumption (kg/day))
(mg/kg/day) Body weight (kg)
and
=
The hazard indices for children and adults were estimated separately using the hypothetical body
weight of 10 kg for children (0 - 1 yr), 30 kg for children (1 - 11 yrs) and 70 kg for adults. Hazard
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index was calculated for the 0-1 year group since a survey conducted during this study showed that
their fish consumption was almost the same as that of the adults.
Bioconcentration Factors (BCF) of aquatic plants were determined as ratios of pesticide
concentrations in the respective tissues and the surrounding aqueous medium, ie:
=
The concentration of pesticides in aqueous medium used above refers to the site at which the
aquatic plants were harvested.
7.2.8.2 Analysis of residues in fish tissues
Residues that were detected in all tissues in each fish species were identified. One-way analysis of
variance was carried out to assess whether pesticide residues varied significantly between tissue
samples. Possibilities less than 0.05 (p < 0.05) were considered statistically significant. Where
there were significant differences Tukey’s HSD (honestly significant diference) test was used for
mean separation.
Calculation of mean: Only detect samples were used in mean calculations. Incidence rate however
was based on total number of samples, as previously described on page 69 of chapter Four.
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7.3 Results
7.3.1 General trend of pesticide levels in fish tissues
Table 7.1 presents general trend of pesticides concentrations and distribution in various organs of
the four fish species analysed. For each fish species, average of the mean concentration of all
residues is highest in the liver followed by gill (except in Bagrus bayad where) and then the
muscle. Mean concentrations (load) of pesticide residues in tissues across all fish species also
follow the order: Liver ˃ Gill > Muscle (Table 7.1). It is also noted that the total pesticide body
load in the fish species is highest in Chrysichthys nigrodigitatus (536.59 µg/kg), followed by
Bagrus bayad (241.66 µg/kg), Oreochromis niloticus (85.86 µg/kg) and Tilapia zilli (69.06 µg/kg).
Bagrus bayad registered the highest mean residue concentrationof all pesticides in the flesh (20.10
µg/kg) whereas C. nigrodigitatus had the highest liver residue of 508.77 µg/kg. The residue
concentrations in the gills across the species however did not differ very much (Table 7.1). Total
number of detected pesticides in tissues of each fish species follows the order:  Liver ˃ Gill >
Muscle as illustrated by Fig. 7.1
Table 7.1: Comparison of mean concentration (µg/kg) of total detected pesticides in tissues
of four fish species
Fish species Total pesticide concentration in Total
Tissues Body Load
Muscle              Gill               Liver
Tilapia zilli 7.42 10.03 44.07 61.52
Oreochromis niloticus 9.90 16.71 61.25 85.86
Chrysichthys nigrodigitatus 11.71 16.11 508.77 536.86
Bagrus bayad 20.10 15.80 203.33 241.66
Pesticide load in tissues 49.13 58.64 817.42
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25
Musle
Gill
Liver
20
15
10
5
0
TZ ON CN BB
Fig.7.1: Total number of detected pesticides in various tissues of four fish species
TZ: Tilapia zilli ON: Oreochromis niloticus
CN: Chrysichthys nigrodigitatus BB: Bagrus bayad
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7.3.2 Organochlorine pesticide residues in fish tissues
Tables 7.2 - 7.5 presents the residue levels of all the pesticides in tissues of the four fish species
analysed. The results of organochlorine pesticide (OCP) residues are presented in this section. Only
three OCP residues (β-lindane, methoxychlor and aldrin) were detected in the muscle tissues of the
four fish species analysed. Beta Lindane and methoxychlor were detected in the muscle of all the 4
species while Tilapia zilli registered the presence of aldrin as the third residue. The level of
methoxychlor was higher than of β-lindane in all the fish species, exception in Oreochromis
niloticus. The mean concentration range of detected OCPs in muscle tissues of the fishes was
0.78µg/kg – 94.0 µg/kg. Both values were recorded in Bagrus bayad; the highest for methoxychlor
and the lowest for β-lindane. The ranking order of decreasing mean concentration of OCP in
muscles of the 4 species follows: B. bayad > C. nigrodigitatus > T. zilli > O. niloticus (Tables 7.2 -
7.5).
Gills of the fish species registered the presence of seven OCP residues, mainly β-lindane,
heptachlor, p,p’-DDD, α-endosulfan, β-endosulfan, endosulfan sulphate and methoxychlor. Beta-
lindane, heptachlor, α-endosulfan, endosulfan sulphate and methoxychlor were detected in the gill
tissues of T. zilli. Beta-lindane, p,p’-DDD, α-endosulfan and endosulfan sulphate were detected in
O. niloticus; Beta-lindane, α-endosulfan, β-endosulfan and methoxychlor in C. nigrodigitatus and
β-lindane, heptachlor, α-endosulfan and methoxychlor in B. bayad. The mean concentration range
of OCP residues detected in gills of the 4 fish species was 0.90 µg/kg – 18.3 µg/kg. The highest
concentration of 18.83 µg/kg was recorded for heptachlor and in T.zilli. The ranking order of
decreasing mean concentration in the gills was C. nigrodigitatus > O. niloticus >B. bayad > T. zilli
(Tables 7.2 - 7.5).
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In the liver of the four fish species, a total of 10 OCP residues were detected. These are beta,
gamma and delta-lindane, heptachlor, α and β-endosulfan, endosulfan sulphate, p,p’-DDE, endrin
and methoxychlor. All of the above, with the exception of delta-lindane was detected in B. bayad.
Similarly, with the exception of endosulfan sulphate, all the listed OCP residues were recorded in
the liver of C. nigrodigitatus. T. zilli and O. niloticus registered the least number of detected
pesticides (4) in the liver tissue. The mean concentration range of OCP residues in the liver of the
fish species was 11.0 µg/kg – 4671.0 µg/kg. The three highest values of 4671.0 µg/kg, 1771.0
µg/kg and 750.60 µg/kg were all recorded in C. nigrodigitatus for methoxychlor, heptachlor and
endrin respectively. The order of decreasing mean concentration of OCP residues in liver of the
fishes was C. nigrodigitatus > B. bayad > O. niloticus > T. zilli (Tables 7.2 - 7.5).
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Table 7.2: Mean concentration (µg/kg) and distribution of pesticides in body tissues of Tilapia zilli
Muscle Gill Liver
Organochhlorines Conc. ± SD range Freq (%) Conc. ± SD Range Freq (%) Conc. ± SD range Freq (%)
β-HCH 1.22 ± 0.7 0.50 – 1.83 20 4.66 ± 2.3 1.53 – 7.20 100 11.0 ± 9.4 2.38 – 25.16 60
Aldrin 16.33 16.33 10 18.83 ± 0.9 18.14 – 19.52 20 12.6 ± 0.9 11.91 – 13.21 20
α-endosulfan - 15.0 ± 7.4 2.58 – 22.90 60 35.2 ± 1.4 34.14 – 36.21 20
Endosulfan sulfate - 4.17 4.17 10 -
Methoxychlor 3.73 ± 1.4 2.19 – 5.44 50 2.5 ± 0.8 1.18 – 3.29 60 26.4 ± 4.4 22.44 - 31.11 30
Load=21.28 Load=45.16 Load=85.20
Pyrethroids - - -
Allethrin - - 12.8 ± 1.6 11.61 – 13.96 20
Fenpropathrin - - 27.3 ± 5.2 23.65 – 31.01 20
Permethrin 31.0 ± 7.1 22.60 – 35.91 30 11.5 ±7.0 5.00 – 23.84 80 415.5 ±35.3 83.2 – 952.10 50
Cyfluthrin 6.15 6.15 10 17.3 ± 10.8 4.26 – 34.65 80 88.7 ± 47.6 7.45 – 131.50 50
Cypermethrin 1.1 1.09 10 2.0 2.01 10 45.8 ± 17.5 30.00 – 62.84 40
Fenvalerate 1.4 1.41 10 2.3 2.24 10 11.0 ± 8.5 3.23 – 25.30 50
Deltamethrin 2.2 ± 1.5 0.67 – 4.43 50 5.11 ± 0.4 4.61 – 5.52 30 -
Load=41.85 Load=38.21 Load=601.20
Organophosphate
Methamidophos 8.6 ± 0.3 8.50 – 9.00 30 20.0 ± 1.5 18.56 – 21.51 30 28.1 ± 5.6 19.44 – 351.20 50
Ethoprophos - 18.5 ± 9.1 3.65 – 33.40 20 20.3 ± 15.9 8.96 – 31.52 20
Diazinon - - 8.1 8.10 10
Dimethoate - - 35.8 ± 2..0 14.9 5 – 53.10 40
Pirimiphos-methyl - 11.63 ± 8.1 1.05 – 22.20 20 14.1 14.06 10
Chlorpyrifos 9.16 ± 4.3 4.27 – 12.21 30 9.24 ± 6.6 2.68 – 15.88 30 9.2 ± 1.1 8.47 – 10.01 20
Malathion 4.35 4.35 10 8.49 8.49 10 -
Fenitrothion - 9.1 ± 4.4 4.18 – 12.95 20 28.1 ± 4.8 24.67 – 31.5 20
Parathion - - 2.1 2.08 10
Chlorfenvinphos - 2.69 2.68 10 -
Profenofos 3.79 ± 0.5 3.46 – 4.12 20 17.55 ± 2.2 14.96 – 18.59 30 5.17 5.17 10
Load=25.9 Load=97.20 Load=150.93
Load = Total of the means of all residues in a pesticide group
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Table 7.3: Mean Concentration (µg/kg) and distribution of pesticides in body tissues of Oreochromis niloticus
Muscle Gill Liver
Organochhlorines Conc.±SD Range Freq (%) Conc.±SD Range Freq (%) Conc.±SD Range Freq (%)
β-HCH 3.25 ± 3.5 0.50 - 8.00 80 8.8 ± 7.2 1.00 – 20.00 80 12.9 ± 10.8 1.13 – 36.40 80
Heptachlor - - 203.0± 91.5 105.12 – 311.60 40
α-endosulfan - 17.2 ± 11.2 1.47 - 54.20 60 63.3 ± 42.5 23.30 – 122.50 40
p,p'-DDD - 15.7 ± 6.9 7.33 – 24.30 40 -
Endosulfan sulfate - 2.9 ± 1.9 1.32 - 6.13 60 23.3 ± 7.5 16.40 – 31.40 30
Methoxychlor 1.2 ± 0.9 0.50 – 2.36 40 - -
Load=4.45 Load=44.6 Load=302.5
Pyrethroids
Allethrin - - 58.0 ± 35.2 32.30 – 111.20 60
Bifenthrin 16.3 ± 7.4 11.00 – 32.50 20 3.2 ± 1.4 2.21 – 4.26 20 -
Fenpropathrin - 14.1 ±11.7 6.67 – 35.1 60 -
Permethrin 22.0 ± 16.0 5.00 - 41.60 70 54.2 ± 24 14.17 – 81.50 80 379.0 ± 54.7 325.00 – 455.10 40
Cyfluthrin 10.0 ± 2.5 8.00 – 11.60 20 46.0 ± 13.2 30.11 – 81.50 40 28.6 ± 12.5 15.11 – 44.20 40
Cypermethrin 11.0 ±8.9 1.00 - 25.10 60 5.6 ± 2.5 2.11 – 11.00 80 43.4± 31.9 11.66 – 78.11 40
Fenvalerate 1.6 ± 1.4 0.60 – 2.61 20 7.6 ± 7.1 2.11 – 13.10 20 53.4 ± 45.0 22.11 - 133.10 60
Deltamethrin 7.5 ± 2.1 6.00 - 9.00 20 7.2 ± 3.2 1.28 – 8.80 40 9.0 ± 3.0 6.78 – 11.09 20
Load=68.40 Load=137.9 Load=571.38
Organophosphate
Methamidophos 6.7 ± 1.2 4.70 – 8.96 80 22.2 ± 9.0 18.52 – 32.50 30 30.7 ± 13.4 21.20 – 40.00 20
Phorate 4.1 ± 0.8 3.26- 5.24 40 - 2.6 ± 1.4 1.49 – 3.61 20
Chlorpyrifos 3.3 ± 1.1 2.15 – 4.73 40 20.0 ± 14.4 2.74 – 33.69 50 3.73 ± 2.3 2.05 – 5.40 20
Malathion - 10.0± 2.2 8.39 – 11.52 20 -
Fenitrothion - - 39.5 ± 19.0 6.18 – 86.60 40
Chlorfenvinphos - - 4.4 4.39 10
Profenofos - 16.0 ± 4.8 12.58 – 21.50 30 25.1 25.11 10
Load=14.10 Load=68.20 Load=106.02
Load = Total of the means of all residues in a pesticide group
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Table 7.4: Mean Concentration (µg/kg) and distribution of pesticides in body tissues of Chrysichthys nigrodigitatus
Muscle Gill Liver
Organochhlorines Conc. ± SD Range Freq (%) Conc. ± SD Range Freq (%) Conc. ± SD Range Freq (%)
β-HCH 2.7 ± 1.6 0.50 – 8.28 30 2.7 ± 1.6 0.50 - 5.12 80 21.0 ± 13.1 1.48 - 71.86 80
γ-HCH - - 65.0 65.00 10
δ-HCH - - 100.0 ± 48.8 15.60 – 185.20 30
Heptachlor - - 1771.0 ± 103 65.10 - 246.51 40
α-endosulfan - 10.16 10.16 10 555.0 ± 91.3 2.21 – 2607.50 70
p,p'-DDE - 207.6 ± 109 8.52 - 635.10 40
Endrin - 750.6 750.61 10
Beta endosulfan - 0.9 ± 0.4 0.50 - 1.20 30 294 ± 143 4.29 - 730.14 40
Methoxychlor 31.0 ± 14.8 8.00 - 45.97 50 1.93 ± 1.0 0.50 - 3.15 50 4671.0 ± 139 1320.0- 8112.0 30
Load=33.70 Load=15.69 Load=8435.16
Pyrethroids
Allethrin - - 112.1  ± 89 18.21 – 255.00 50
Bifenthrin - - 115.0 ± 84 27.45 - 221.20 30
Fenpropathrin - 12.5 12.49 10 199.1 199.10 10
λ-cyhalothrin - 58.6 58.60 10 1064.0 1064.10 10
Permethrin 41.0 ± 25.4 2.14 - 180.89 100 15.3 ± 8.5 1.11 - 23.20 80 861.4 ± 102 46.40 – 2887.0 80
Cyfluthrin 7.8 ± 4.1 5.20 - 15.16 60 22.5 ± 14.2 4.48 - 42.16 60 234.6 ± 164 5.86 – 485.61 70
Cypermethrin 6.44 ±  2.3 4.75 - 8.13 20 23.7 ±  11.3 6.94 - 34.20 50 376.7 ± 140 16.01 - 782.50 70
Fenvalerate 4.15 ± 1.7 1.24 - 5.31 50 5.2 ± 4.0 1.73 - 12.62 70 483.0 ± 84 14.26 – 1661.00 80
Deltamethrin 14.2 ±10.3 5.12 - 25.48 30 233.3 ± 85 177.20 - 380.60 50
Load=59.40 Load=151.97 Load=3679.20
Organophosphate
Methamidophos - - 19.3 ± 9.7 12.41 – 26 .30 20
Dimethoate 6.57 6.57 10 29.5 ± 8.5 23.41 - 35.48 20
Pirimiphos-methyl 4.1 4.05 10 47.8 ± 3.1 46.00 - 51.36 30 21.0 ± 0.8 19.96 – 21.14 20
Chlorpyrifos 1.6 1.61 10 2.34 ± 0.2 2.19 - 2.51 30 4.35 4.35 10
Malathion - 7.69 ± 2.3 6.10 - 9.28 20 -
Parathion - - 8.1 ± 2.7 6.17 - 10.06 20
Chlorfenvinphos - - 13.9 ± 3.4 11.52 - 16.31 20
Load=12.27 Load=57.84 Load=96.18
Load= Total of the means of all residues in a pesticide group
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Table 7.5: Mean Concentration (µg/kg) and distribution of pesticides in body tissues of Bagrus bayad
Muscle Gill Liver
Organochhlorines Conc. ± SD Range Freq Conc. ± SD Range Freq Conc. ± SD Range Freq
β-HCH 0.78 ± 0.1 0.50 - 1.513 40 3.14 ± 2.6 0.658 - 9.187 80 20.0 ± 20.1 1.23 - 57.21 90
γ-HCH 57.3 ± 27.7 4.50 -162.21 60
Heptachlor 4.0 ± 0.7 3.26 - 4.80 30 591.0 ± 150.4 68.14 - 1156.40 60
α-endosulfan 17.5 ± 0.0 17.51 20 200.0 ± 123 9.55 - 582.61 70
p,p'-DDE 75.8 ± 18 62.84 - 88.73 20
Endrin 38.9 ± 3.3 36.59 - 41.23 20
Beta endosulfan 627.3 ± 0.2 627.00 20
Endosulfan sulfate 150.0 ± 92 45.3 - 223.1 30
Methoxychlor 94.0 ± 30 56.20 - 152.60 40 4.1 ± 2.7 1.25 - 8.51 80 289.7 ± 12 36.47 - 508.10 70
Load=94.78 Load=28.76 Load=2050.00
Pyrethroids
Allethrin 4.1 ± 1.1 2.87 -5.22 30 90.0 ± 85 5.48 - 173.55 40
Bifenthrin 8.2 ± 5.1 6.25 - 10.11 20
Fenpropathrin 6.84 6.84 10 1.69 1.69 10
Lamda-cyhalothrin 12.4 ± 8.2 2.96 - 21.52 40
Permethrin 49.8±  31.3 3.25 - 105.00 90 36.1 ± 24 14.67 - 88.50 90 2190.0 ± 211 103.3 – 5378.4 80
Cyfluthrin 12.2 ± 6.9 5.98 - 16.52 40 41.2 ± 23.2 8.35 - 71.36 80 122.3 ± 182 75.11 – 463.8 30
Cypermethrin 13.3 ± 11.8 4.21 - 22.31 20 11.6 ± 9.8 2.35 - 22.20 30 76.7 ± 38 20.40 - 274.31 80
Fenvalerate 4.1 ± 1.8 2.56 - 6.62 40 104 ± 68 32.2 - 216.90 80
Deltamethrin 1.3 1.29 10 31.0 ±20 12.50 - 53.31 30
Load=84.8 Load=103.92 Load=328.51
Organophosphate
Methamidophos 8.76 ± 2.3 7.11 - 10.40 20 37.7 ± 6.2 33.32 – 42.13 20
Ethoprophos 11.9 ± 9.8 4.95 - 18.91 20 3.0 ± 1.1 2.10 - 4.51 40 36.1 ± 5.6 32.10 - 40.14 20
Fonofos 19.1± 1.5 18.01 - 20.11 20
Dimethoate 33.3 ± 0.0 33.30 20 36.5 ± 18 18.82 - 52.35 40
Chlorpyrifos 6.2 ± 0.7 1.19 - 11.21 20 25.6 ± 17.5 4.14 - 42.91 50
Malathion 6.48 6.48 10 32.8 ± 0.5 32.41 - 33.12 20
Fenitrothion 8.7 ± 2.3 6.33 - 11.03 30 193.0 ± 79 108.0 - 300.0 40
Chlorfenvinphos 6.3 ± 5.2 2.63 – 10.0 20 5.4 ± 3.1 2.94 - 8.88 30 13.7 ± 6.2 4.41 - 18.18 40
Profenofos 17.0 ± 7.8 5.01 - 26.14 50 31.6 ± 20 12.41 - 52.33 30 35.7 ± 6.2 31.30 - 40.00 20
Load=41.40 Load=122.84 Load=404.60
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7.3.3 Synthetic pyrethroid pesticide residues in fish tissues
Six of the nine targeted synthetic pyrethroid (SPs) residues were recorded in the muscle tissues
of the fishes and these are bifenthrin, permethrin, cyfluthrin, cypermethrin, fenvalerate and
deltamethrin. All the six were detected in the muscle of O. niloticus. All, with the exception of
bifenthrin, was detected in T. zilli while fenvalerate was the only non-detect of the six in B.
bayad. Chrysichthys nigrodigitatus also recorded all with the exception of bifenthrin and
deltamethrin (Tables 7.2 - 7.5). The concentration range of SPs in muscle of the fishes was 0.60
µg/kg – 180.89 µg/kg. The highest concentration of 180.89 µg/kg was recorded for permethrin in
the muscle of C. nigrodigitatus. Mean concentration of SPs in muscle tissues of the four fish
species was highest for B. bayad (16.96 µg/kg), followed by C. nigrodigitatus (14.85 µg/kg), O.
niloticus (11.40 µg/kg) and T. zilli (8.37 µg/kg).
All the nine targeted SPs were detected in measurable quantities in the gills and liver tissues of
the fish species being analysed. The number of detects in the gills were 5, 7, 7, and 6 for T. zilli,
O. niloticus, C. nigrodigitatus and B. bayad respectively; while the corresponding values in liver
tissues were 6, 7, 9 and 8 respectively. The respective mean concentration ranges of SPs in gills
and liver tissues of the fish species were 1.11 µg/kg – 88.50 µg/kg and 1.69 C. nigrodigitatus –
5378.40 µg/kg(Tables 7.2 - 7.5). The highest concentration in the two tissues were recorded for
permethrin in B.bayad. The mean concentration of SP residues in the gills follows the order C.
nigrodigitatus > O. niloticus > B.bayad > T. zilli, while that for the liver tissues is C.
nigrodigitatus > B.bayad > T. zilli > O. niloticus (Tables 7.2 - 7.5).
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7.3.4 Organophosphorus pesticide residues in fish tissues
Out of the target 13 OP pesticides, 9 were encountered and quantified in muscle and gill tissues
of the four fish species under study, while 12 were measured in their liver tissues. In the muscle
tissues, only 4 (methamidophos, chlorpyrifos, malathion and profenofos) were detected in T.
zilli; 3 (methamidophos, phorate and chlorpyrifos) in O. niloticus, 3 (Dimethoate,pirimiphos-
methyl and chlorpyrifos) in C. nigrodigitatus and 4 (Ethoprophos, chlorpyrifos, chlorfenvinphos
and profenofos) in B.bayad. The range of OP residue concentration in muscle of the fishes was
1.19 µg/kg – 26.14 µg/kg (Tables 7.2 - 7.5). The highest concentration was recorded for
profenofos and in B.bayad. The average OP residue concentration in the muscle tissues of the
fishes is ranked as follows B. bayad (9.10 µg/kg) > T. zilli (6.48 µg/kg) > O.niloticus (4.70
µg/kg) > C. nigrodigitatus (4.09 µg/kg) (Tables 7.2 - 7.5).
Three OPs were detected in the gills of C. nigrodigitatus, 4 in O. niloticus, 6 in T.zilli and 8 in B.
bayad. Six residues were detected in liver of both O. niloticus and C. nigrodigitatus; eight in B.
Bayad and nine in T. zilli. The concentration ranges in gills and liver respectively are 1.05 –
52.33 µg/kg and 1.49 – 351.20 µg/kg (Tables 7.2 - 7.5). Profenofos registered the highest
concentration of 52.33 µg/kg in the gills and this was recorded in B. bayad while the highest
concentration in the liver was recorded for methamidophos and in T. zilli. The order of
decreasing mean concentration of OP residues measured in gills is C. nigrodigitatus > B. bayad
> O. niloticus > T. zilli; and that in the liver is B. bayad > O. niloticus > T. zilli > C.
nigrodigitatus (Tables 7.2 - 7.5).
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7.3.5 Analysis of residues in tissue of fishes
Residues that were detected in all tissues in each fish species were identified. One-way analysis
of variance was carried out to assess whether pesticide residues varied significantly between
tissue samples in each species. Possibilities less than 0.05 (p < 0.05) were considered statistically
significant. Results of the analysis for tissues of T. zilli, O. niloticus, C. nigrodigitatus and B.
bayad are presented in Tables 7.6, 7.7, 7.8 and 7.9 respectively. Five pesticides were present and
quantified in the three tissues under investigation in Tilapia zilli; four in Oreochromis niloticus,
five in Chrysichthys nigrodigitatus and seven in Bagrus bayad. Generally, statistical differences
exist between tissue concentrations in all the fish species. In T. zilli, chlorpyrifos concentration
did not differ significantly among the tissues. In O. niloticus, there was no significant difference
in deltamethrin concentration the tissues. Similarly, muscle and gill tissue did not differ
significantly in fenvalerate concentration in C. nigrodigitatus. Even though generally residue
concentrations in tissues follow the order Liver > Gill > muscle, significant differences did not
exist between concentrations in gill and muscle tissues.
Table 7.6: Mean concentration of selected pesticide residues in different tissues of Tilapia zilli
Concentration (µg/kg)
P-values
Muscle Gill Liver
β-lindane 1.22a ± 0.7 4.66ab ±  2.3 11.0b ±  9.4 0.047
Methoxychlor 3.73a ± 1.4 2.50a ± 0.8 26.4b ± 4.4 0.0001
Permethrin 31.0a ± 7.1 11.5a ± 7.0 415.5b ± 35.3 0.008
Methamidophos 8.60a ± 0.3 20.0b ± 1.5 28.10b ± 5.6 0.001
Chlorpyrifos 9.16a ±  4.3 9.24a ± 6.6 9.20a ± 1.1 1.000
Within rows, means with different superscript letters are statistically significant, p<0.05
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Table 7.7: Mean concentration of selected pesticide residues in different tissues of Oreochromis niloticus
Concentration (µg/kg)
P-values
Muscle Gill Liver
β-lindane 3.25a ± 3.5 8.8a ± 7.2 12.9a ± 1.2 0.087
Permethrin 22.0a ± 16 54.2a ± 24.9 379.0b ± 54.7 0.0001
cypermethrin 11.0a ± 8.9 5.6a ± 2.5 43.4b ± 31.9 0.003
Deltamethrin 7.5a ±  2.1 7.2a ± 3.2 9.0a ± 3.0 0.396
Within rows, means with different superscript letters are statistically significant, p<0.05
Table 7.8: Mean concentration of selected pesticide residues in different tissues of Chrysichthys
nigrodigitatus
Concentration (µg/kg)
P-values
Muscle Gill Liver
β-lindane 2.9a ± 0.6 3.0a ± 1.6 21.0a ± 3.0 0.192
Methoxychlor 31.0a ± 14.8 1.93b ± 1.0 4671.0C ± 339.0 0.003
Permethrin 41.0a ± 5.4 15.3a ± 8.5 861.4b ± 120.2 0.008
Cyfluthrin 7.8a ± 4.1 22.5a ± 14.2 234.6b ± 16.4 0.002
Fenvalerate 4.15a ± 1.7 5.2a ± 4.0 483.0b ± 48.0 0.026
Within rows, means with different superscript letters are statistically significant, p<0.05
Table 7.9: Mean concentration of selected pesticide residues in different tissues of Bagrus bayad
Concentration (µg/kg)
P-values
Muscle Gill Liver
β-lindane 1.2a ± 1.1 3.14 a ± 2.6 20.0a ± 4.1 0.011
Methoxychlor 150.0a ± 13.1 4.1b ± 2.7 289.6a ± 2.2 0.004
Permethrin 49.8a ± 13.3 36.1a ± 24.6 2190.0b ± 21.1 0.001
Cyfluthrin 12.2a ± 1.9 41.2a ± 23.3 342.3b ± 32.1 0.0001
Chlorfenvinphos 6.3a ± 5.3 5.4a ± 3.1 13.7a ± 6.2 0.158
Ethoprophos 11.9a ± 9.8 3.0a ± 1.1 36.1b ± 5.6 0.002
profenofos 17.0a ± 7.8 31.6a ±  11.9 35.7a ±  6.2 0.181
Within rows, means with different superscript letters are statistically significant, p<0.05
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7.3.6 Health Risk analysis
Tables 7.10, 7.11, 7.12 and 7.13 present health risk estimate for systemic effects associated with
pesticide residues in T. zilli, O. niloticus, C. nigrodigitatus and B. bayad respectively.
Concentrations in only muscle and/or gill tissues were used for the health risk estimates because
these constitute the edible parts (the liver is normally gutted out with the intestines and therefore
not consumed, hence it was not involved in the risk analysis). Where pesticides were quantified
in both muscle and gill tissues, the concentrations in the two tissues (muscle and gill) were
pooled for the health estimate analysis. The tables comprise reference dose (Rfd) or acceptable
daily intake (ADI), the computed dietary exposure dose and the corresponding health hazard
indices for  children between 0-1 year, 1-11 years and adults. Aldrin, alpha-endosulfan and
ethoprophos hazard indices in T. zilli were greater than unity for under one year children and 1 or
close to 1 for the age 1-11year old (Table 7.10). In O. niloticus and C. nigrodigitatus however,
only alpha-endosulfan recorded Hazard index of more than 1 (Tables 7.11 and 7.12). Bagrus
bayad on the other hand recorded two pesticides (alpha-endosulfan and ethoprophos) with
Hazard index greater than 1 (Table 7.13).
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Table 7.10: Health hazard indices of pesticides in Tilapia zilli
Substance ADI(ug/kg) Conc.(ug/kg) Exposure dose(ug/kg/day) Hazard index (HI)
Organochhlorines 0-1yr 1-11yrs Adult 0-1yr 1-11yrs Adult
β-HCH 5.00 5.88 0.048 0.0161 0.007 0.010 0.003 0.001
Aldrin 0.10 35.16 0.288 0.096 0.041 2.88 1.0 0.411
α-endosulfan 0.05 15.00 0.123 0.041 0.018 2.46 0.819 0.351
Endosulfan sulfate 0.05 4.17 0.034 0.011 0.005 0.684 0.228 0.098
Methoxychlor 5.00 6.23 0.051 0.017 0.007 0.010 0.003 0.001
Pyrethroids
Permethrin 50.00 42.50 0.349 0.116 0.050 0.007 0.002 0.001
Cyfluthrin 3.00 79.80 0.654 0.218 0.093 0.218 0.073 0.031
Cypermethrin 50.00 3.10 0.025 0.008 0.004 0.000 0.000 0.000
Fenvalerate 20.00 3.70 0.030 0.010 0.004 0.001 0.000 0.000
Deltamethrin 10.00 7.31 0.060 0.020 0.008 0.006 0.002 0.001
Organophosphate
Methamidophos 1.00 28.60 0.234 0.078 0.033 0.234 0.078 0.033
Ethoprophos 0.10* 18.50 0.152 0.050 0.021 1.517 0.505 0.216
Pirimiphos-methyl 4.00 11.63 0.095 0.032 0.014 0.024 0.008 0.003
Chlorpyrifos 10.00 18.40 0.151 0.050 0.021 0.015 0.005 0.002
Malathion 30.00 12.84 0.105 0.035 0.015 0.004 0.001 0.000
Fenitrothion 5.00 9.10 0.075 0.025 0.011 0.015 0.005 0.002
Chlorfenvinphos 0.50 2.69 0.022 0.007 0.003 0.044 0.014 0.006
Profenofos 30.00 55.45 0.455 0.151 0.065 0.015 0.005 0.002
NB: highlighted cells show HI with possible health implications
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Table 7.11: Health hazard indices of pesticides in Oreochromis niloticus
Substance
ADI(ug/kg) Conc.(ug/kg) Exposure dose(ug/kg/day) Hazard index
Organochhlorines 0-1yr 1-11yrs Adult 0-1yr 1-11yrs Adult
β-HCH 5.00 12.05 0.099 0.033 0.014 0.020 0.007 0.003
α-endosulfan 0.05 17.20 0.141 0.047 0.020 2.821 0.939 0.403
p,p'-DDD - 15.70 - - - - - -
Endosulfan sulfate 0.05 2.90 0.024 0.008 0.003 0.475 0.158 0.068
Methoxychlor 5.00 1.20 0.010 0.003 0.001 0.002 0.001 0.000
Pyrethroids
Bifenthrin 15.00 19.50 0.160 0.053 0.023 0.011 0.004 0.002
Fenpropathrin 30.00 14.10 0.116 0.038 0.016 0.004 0.001 0.000
Permethrin 50.00 76.20 0.625 0.208 0.089 0.012 0.004 0.002
Cyfluthrin 3.00 56.00 0.459 0.153 0.066 0.153 0.051 0.022
Cypermethrin 50.00 16.60 0.136 0.045 0.019 0.003 0.001 0.000
Fenvalerate 20.00 9.20 0.075 0.025 0.011 0.004 0.001 0.000
Deltamethrin 10.00 14.70 0.120 0.040 0.017 0.012 0.004 0.002
Organophosphate
Methamidophos 1.00 28.90 0.237 0.079 0.034 0.237 0.079 0.034
Phorate 0.10 4.10 0.034 0.011 0.005 0.336 0.112 0.048
Chlorpyrifos 10.00 23.30 0.191 0.064 0.027 0.019 0.006 0.003
Malathion 30.00 10.00 0.082 0.027 0.012 0.003 0.001 0.000
Profenofos 30.00 16.00 0.131 0.044 0.019 0.004 0.002 0.001
NB: highlighted cells show HI with possible health implications
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Table 7.12: Health hazard indices of pesticides in Chrysichthys nigrodigitatus
Substance
ADI(ug/kg) Conc.(ug/kg) Exposure dose(ug/kg/day) Hazard index
Organochhlorines 0-1yr 1-11yrs Adult 0-1yr 1-11yrs Adult
β-HCH 5.00 5.40 0.044 0.015 0.006 0.008 0.003 0.001
α-endosulfan 0.05 10.60 0.087 0.029 0.012 1.738 0.579 0.248
Beta endosulfan 0.05 0.90 0.007 0.002 0.001 0.148 0.049 0.021
Methoxychlor 5.00 32.93 0.270 0.090 0.038 0.054 0.018 0.008
Pyrethroids
Fenpropathrin 30.00 12.50 0.103 0.034 0.015 0.003 0.001 0.000
Lamda-cyhalothrin 5.00 58.60 0.480 0.160 0.068 0.096 0.032 0.014
Permethrin 50.00 56.30 0.462 0.154 0.066 0.009 0.003 0.001
Cyfluthrin 3.00 30.30 0.248 0.083 0.035 0.083 0.028 0.012
Cypermethrin 50.00 30.14 0.247 0.082 0.035 0.005 0.002 0.001
Fenvalerate 20.00 9.35 0.077 0.025 0.011 0.004 0.001 0.000
Deltamethrin 10.00 14.20 0.116 0.039 0.017 0.012 0.004 0.002
Organophosphate
Dimethoate 1.00 6.57 0.054 0.018 0.008 0.054 0.018 0.008
Pirimiphos-methyl 4.00 51.90 0.426 0.142 0.061 0.106 0.035 0.015
Chlorpyrifos 10.00 3.94 0.032 0.011 0.004 0.003 0.001 0.000
Malathion 30.00 7.69 0.063 0.021 0.009 0.002 0.001 0.000
NB: highlighted cells show HI with possible health implications
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Table 7.13: Health hazard indices of pesticides in Bagrus bayad
Substance
ADI(ug/kg) Conc.(ug/kg) Exposure dose(ug/kg/day) Hazard index (HI)
Organochhlorines 0-1yr 1-11yrs Adult 0-1yr 1-11yrs Adult
β-HCH 5.00 3.92 0.032 0.011 0.005 0.006 0.002 0.001
Heptachlor 0.10 4.00 0.033 0.011 0.005 0.328 0.109 0.047
α-endosulfan 0.05 17.50 0.143 0.048 0.021 2.870 0.956 0.410
Methoxychlor 5.00 98.10 0.804 0.268 0.115 0.161 0.054 0.023
Pyrethroids
Allethrin 8.00 4.10 0.034 0.011 0.005 0.004 0.001 0.001
Bifenthrin 15.00 8.20 0.067 0.022 0.010 0.004 0.002 0.001
Fenpropathrin 30.00 6.84 0.056 0.019 0.008 0.002 0.001 0.000
Permethrin 50.00 85.90 0.704 0.235 0.101 0.014 0.005 0.002
Cyfluthrin 3.00 53.40 0.438 0.146 0.063 0.146 0.049 0.021
Cypermethrin 50.00 24.90 0.204 0.068 0.029 0.004 0.001 0.001
Fenvalerate 20.00 4.10 0.034 0.011 0.005 0.002 0.001 0.000
Organophosphate
Methamidophos 1.00 37.60 0.308 0.103 0.044 0.308 0.103 0.044
Ethoprophos 0.10 14.90 0.122 0.041 0.017 1.222 0.407 0.174
Dimethoate 1.00 33.30 0.273 0.091 0.039 0.273 0.091 0.039
Chlorpyrifos 10.00 26.80 0.220 0.073 0.031 0.022 0.007 0.003
Malathion 30.00 6.48 0.053 0.018 0.008 0.002 0.001 0.000
Fenitrothion 5.00 8.70 0.071 0.024 0.010 0.014 0.005 0.002
Chlorfenvinphos 0.50 11.70 0.096 0.032 0.014 0.192 0.064 0.027
Profenofos 30.00 48.60 0.398 0.133 0.057 0.013 0.004 0.002
NB: highlighted cells show HI of 1 or greater (with possible health implications)
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7.3.7 Pesticide residues and bioconcentration in Ceratophyllum demersum and Nymphaea
lotus
Tables 7.14 and 7.15 present pesticides detected in Ceratophyllum demersum and Nymphaea
lotus and the extent to which the pesticides are bioconcentrated by these aquatic plants. The
presence of 3 organochlorines, 4 synthetic pyrethroids and 7 organophosphorus pesticide
residues were recorded in C. demersum (Table 7.14). Of the detected organochlorine pesticides,
endrin recorded the highest mean concentration of 5.90 µg/kg whilst β-lindane and p,p’-DDE
were detected in low concentrations of 0.50 µg/kg and 0.53 µg/kg respectively. They all
recorded high incidence rate between 80% – 100% (Table 7.14). The levels of synthetic
pyrethroids were generally low, with mean concentration range of 0.62-2.17 µg/kg.
Cypermethrin registered the highest mean residue of 2.17 µg/kg among the pyrethroids. The
organophosphorus residues recorded the highest levels in C. demersum with a mean
concentration range of 2.86 – 129.0 µg/kg. Methamidophos registered the highest
organophosphorus mean concentration (129.0 µg/kg) while malathion recorded the lowest (2.86
µg/kg). From the values in Table 7.14, organophosphorus pesticides had the highest load (241.66
µg/kg) followed by the OCPs (6.93 µg/kg) and SPs (5.21 µg/kg) in Ceratophyllum demersum.
Nymphaea lotus on the other hand registered the presence of more pesticide residues (Table
7.15). The presence of 4 organochlorines pesticides, 6 synthetic pyrethroids and 8
organophosphorus pesticide residues were detected. The highest mean residue was recorded for
γ-lindane (35.90 µg/kg), followed by methamidophos (8.66 µg/kg) (Table 7.15). Unlike
Ceratophyllum demersum, Nymphaea lotus bioconcentrated OCPs most, followed by OPs and
then SPs (Tables 7.14 and 7.15).
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Examination of the results reveals that all the detected pesticides in the aquatic plants were
bioconcentrated, with the exception of endrin in Nymphaea lotus and β-HCH (in Ceratophyllum
demersum) since their concentrations in the aqueous medium were more than their corresponding
concentrations in the plant tissues (Tables 7.14 and 7.15). Both plants have higher
bioconcentration of organophosphorus pesticides than the OCPs and SPs and follow the order:
OPs > SPs > OCPs. It is also observed that Ceratophyllum demersum generally have higher
bioconcentration of OPs than Nymphaea lotus. For instance whereas the bioconcentration factors
for methamidophos, diazinon and chlorpyrifos in C. demersum respectively were 330.8, 4470.0
and 2305, the corresponding figures for the same pesticides in N. lotus were 22.2, 800.0 and
305.0 (Tables 7.14 and 7.15).
Table 7.14: Pesticides in Ceratophyllum demersum and bioconcentration factor
Mean Conc. in Conc. range Freq. Ambient conc.in Bioconcentration
C. demersum (µg/kg) (µg/kg) (%) water (µg/L) Factor (BCF)
Organochlorines
β-HCH 0.50 ± 0.23 0.50-0.61 100 3.800 0.13
p,p'-DDE 0.53 ± 0.00 0.50-0.61 80 0.050 1.06
Endrin 5.90 ± 0.50 5.30-6.40 80 2.400 2.45
Load 6.93
Pyrethroids
Lamda-cyhalothrin 1.42 ± 0.59 1.10-2.10 60 0.068 20.90
Cyfluthrin 1.00 ± 0.14 0.80-10.00 40 0.011 91.00
Cypermethrin 2.17 ± 0.50 1.81-2.74 60 0.720 3.00
Fenvalerate 0.62 ± 0.47 0.50-1.30 80 0.010 62.00
Load 5.21
Organophosphates
Methamidophos 129.00 ± 21.80 113.60-154.30 60 0.390 330.80
Diazinon 44.70 ± 1.2 3.10-5.30 60 0.010 4470.00
Chlorpyrifos 46.10 ± 6.4 38.70-50.00 60 0.020 2305.00
Malathion 2.86 2.86 20 0.010 286.00
Fenitrothion 11.00 ± 3.50 8.50-13.40 40 0.004 2750.00
Parathion 4.70 ± 0.32 4.50-5.10 60 nd -
Profenofos 3.30 ± 1.10 2.50-4.10 40 0.010 330.00
Load 241.66
Load = Total of the means of all residues in each pesticide group
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Table 7.15: Pesticides in Nymphaea lotus and bioconcentration factor
Mean Conc. in Conc. range Freq. (%) Ambient conc. Bioconcentration
N. lotus(µg/kg) (µg/kg) In water (µg/L) Factor (BCF)
Organochlorines
β-HCH 3.90 ± 2.80 1.30-8.00 80 3.800 1.27
γ-HCH 35.90 ± 4.90 29.60-39.90 100 0.100 359.00
p,p'-DDE 0.66 ± 0.63 0.50-1.10 40 0.050 13.20
Endrin 0.70 ± 0.27 0.50-0.90 40 2.400 0.30
Load 41.16
Pyrethroids
Bifenthrin 2.33 ± 0.71 1.31-2.93 80 0.049 47.00
Lamda-cyhalothrin 2.20 ± 0.99 1.00-3.00 80 0.068 32.40
Permethrin 0.80 ± 0.31 0.50-1.00 40 0.032 25.00
Cyfluthrin 6.20 ± 0.89 5.60-7.50 80 0.011 563.60
Cypermethrin 1.90 ± 0.45 1.57-2.20 40 0.720 2.60
Deltamethrin 0.52 ± 0.00 0.50-0.54 40 0.330 1.58
Load 13.62
Organophosphates
Methamidophos 8.66 ± 4.95 2.24-14.30 80 0.390 22.20
Ethoprophos 5.10 ± 0.57 4.70-5.50 40 0.030 170.00
Phorate 2.80 ± 0.46 2.40-3.10 40 0.006 466.70
Diazinon 4.00 4.00 20 0.01 800.00
Pirimiphos-methyl 2.14 2.14 20 0.01 214.00
Chlorpyrifos 6.10 ± 0.36 5.80-6.50 60 0.020 305.00
Parathion 4.70 ± 0.46 4.36-5.00 40 nd -
Chlorfenvinphos 2.93 2.90 20 0.080 36.60
Load 32.8
Load = Total of the means of all residues in each pesticide group
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7.4 Discussions
7.4.1 Organochlorine pesticides concentrations and composition in tissues of fishes
The determinations were done on wet-weight basis of the tissue samples. In all, eleven
Organochlorine pesticides-OCPs (β-HCH, γ-HCH, δ-HCH, heptachlor, α-endosulfan, β-
endosulfan, endosulfan sulfate, p,p’-DDD, p,p’-DDE, endrin and methoxychlor ) were quantified
in muscle, gill and liver tissues of the four fish species investigated (Tilapia zilli, Oreochromis
niloticus, Chrysicththys nigrodigitatus and Bagrus bayad). The mean concentration range
recorded in the tissues of all the fishes was 0.78 µg/kg – 4671 µg/kg. The highest of 4671 µg/kg
was recorded for methoxychlor in the liver of Chrysicththys nigrodigitatus (Table 7.4) while β-
HCH recorded the lowest concentration in the muscle tissue of Barus bayad (Table 7.5). Three
OCPs (β-HCH, heptachlor and methoxychlor) were detected in the muscle of the fishes in the
mean concentration range of 0.78 -94 µg/kg. The highest and the lowest were both recorded in B.
bayad for methoxychlor and β-HCH respectively. Methoxychlor and β-HCH were the most
frequently encountered OCPs in muscle of the fishes. From Tables 7.2 – 7.5, it can be established
that OCP residue concentrations in the tissues of the fishes follow the order liver > gill > muscle.
So also imputed values from the data gathered established that on the average, 57.5%, 85.0% and
76.0% of muscle, gill and liver tissue samples respectively registered the presence of OCP
residues in the fish species. The European Union (EU) default Maximum Residue Level (MRL)
of any pesticide in fish tissue is 0.01mg/kg (10 µg/kg). In line with this, only methoxychlor and
heptachlor exceeded MRL in the fish muscle tissues. Heptachlor (16.33 µg/kg) exceeded MRL in
muscle of T. zilli, while methoxychlor exceeded in muscle tissues of both C. nigrodigitatus
(31.00 µg/kg) and B. bayad (94.00 µg/kg). Thus in all, 13% of the OCPs residues in muscle
tissues of the fish species exceeded MRL.
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Table 7.16 compares results of the present study with some from other regions of the world as
well as with those from some local studies. Comparison of the mean OCP residue ranges in
muscle tissues from the present study with results from other local studies show that values from
this study are higher (Table 7.16). Whereas the highest local OCP concentration range in the
muscle of fish (0.3- 7.13 µg/kg) was quoted by Afful et al., (2010) for fish species from the
Densu River, that in this study was 0.78 – 94.00 µg/kg. Compared however to the ranges quoted
by some researchers from other regions of the world, the concentration range in this study is
lower. For instance Pazou et al., (2006) reported  a mean concentration range less than limit of
detection – 134.00 µg/kg for fish species from Oueme river basin in Benin; Said and Hamed,
(2005) also recorded a range of 1.217 - 3759 µg/kg for species from El-Temsah and Bitter Lakes
of Suez Canal, Egypt while Adeyemi et al., (2008) registered astronomical mean concentration
range 10.00 - 8920 µg/kg for OCPs in muscle tissues of three species from Lagos Lagoon in
Nigeria (Table 7.16). Fishes in Ghanaian aquatic ecosystems can therefore generally be
considered relatively less contaminated.
Seven OCPs were detected in gill tissues of the fishes, namely β-HCH, heptachlor, α-endosulfan,
β-endosulfan, endosulfan sulfate, p,p’-DDD and methoxychlor. β-HCH had the highest incident
rate of 100% in T. zilli, 80% in O. niloticus and B. bayad, and 90% in C. nigrodigitatus. The
range of mean concentration in all the three species was 0.90 – 18.33 µg/kg. The least
concentration of 0.90 µg/kg was detected for β-endosulfan in C. nigrodigitatus and the highest
(18.83 µg/kg) for heptachlor in T. zilli. This range, as compared to that of Gbeddy et al., (2012)
was much lower. The liver tissues recorded the highest number of OCP residues (10) namely β,
γ, λ-HCH, heptachlor, endrin, α-endosulfan, β-endosulfan, p,p’-DDE, p,p’-DDD and
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methoxychlor with a mean concentration range of 11.00 - 4671 µg/kg. Four of the ten quantified
OCPs were recorded in the liver of T. zilli, with a mean range of 11.00 – 35.2 µg/kg (Table 7.2)
and in O. niloticus 12.90 – 63.30 µg/kg (Table 7.3). Bagrus. bayad and C. nigrodigitatus each
recorded the presence of 9 OCPs and with respective mean concentration ranges of 20.00 –
627.30 µg/kg and 21.0 -4671.0 µg/kg. Concentrations in the liver were not only significantly
higher but also several ten folds higher, in most cases than corresponding concentrations in the
other tissues (gill and muscle).
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Table 7.16 Mean concentrations of pesticide residues in fish tissues from local and international
studies compared to the present study.
Reference No. of Fish tissue Contaminants Range Location
species detected (µg/kg)
Local studies
Darko et al., (2008) 1 (Tilapia) Muscle 4  OPs 0.018 – 5.232 Lake Bosomtwi
Essuman et al.,(2009) NS Muscle 14 OCPs 0.10 – 0.30 Lagoons in Central Region
Afful et al., (2010) 6 Muscle 14 OCPs 0.3 – 71.30 Densu basin
Adu-Kumi et al.,  (2010) 2 Muscle 17  OCPs Nd –290.00 Weija, Bosomtwi and Volta
Fianko et al., (2011) NS Muscle 14  OCPs 0.51 – 7.99 Densu River basin
Gbeddy et al., (2012) 2 Muscle 15  OCPs 0.10 – 17.35 Kpando (Volta Lake)
Gill ʺ 0.56 – 37.75 ʺ
Present study 4 Muscle 3  OCPs 0.78 – 94.00 Afram Lake arm of Volta
Gill 7  OCPs 0.90 – 18.83 ʺ
Liver 11 OCPs 11.0 –4671.0 ʺ
Muscle 7  Pyrethroids 1.10 – 49.80 ʺ
Gill 8 Pyrethroids 2.00 – 58.60 ʺ
Liver 9 Pyrethroids 9.0 –2190.00 ʺ
Muscle 8  OPs 1.60 – 17.00 ʺ
Gill 9  OPs 2.34 – 47.80 ʺ
Liver 13 OPs 2.1 – 193.00 ʺ
Studies from other
regions
Nemr & Abd-Allah (2004) 4 Muscle 12  OCPs 20.0 –211.00 Egyptian markets
Said & Hamed (2005) 3 Muscle 11  OCPs 1.217 –3757.00 Suez  Canal-Egypt
Pazou et al., (2006) 5 Muscle 9  OCPs Nd –1364.00 Oueme River basin–Benin
Fenandez-Bringas et al., 1 Muscle 16  OCPs 0.08 – 6.97 Mexico
(2008)
Adeyemi et al., (2008) 3 Muscle 9  OCPs 10.0 –8920.0 Lagos Lagoon – Nigeria
Akan et al., (2013) 4 Muscle 11  OCPs 0.12 - 4.81 Alau Dam, Borno State –
Gill 11  OCPs 0.22 – 7.45 Nigeria
Liver 11  OCPs 0.35 – 8.98 ʺ
NS – Not stated;   Nd – Not detected;   OCPs – Organochlorine pesticides;
OPs – Organophosphorus pesticides
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7.4.2 Synthetic pyrethroid concentrations and composition in tissues of fishes
The targeted nine synthetic pyrethroids (SPs) were all detected in the fish tissue samples in a
mean concentration range of 1.00 - 2190 µg/kg. Seven of them (bifenthrin, permethrin, cyfluthrin
cypermethrin, fenvalerate and deltamethrin) were detected in muscle of the three fish species in a
mean concentration range of 1.10 – 49.8 µg/kg. The least concentration (1.10 µg/kg) was
recorded for cypermethrin in Tilapia zilli while the highest concentration (49.8 µg/kg) was
recorded for permethrin in Bagrus bayad. On the average, 77.5%, 87.5% and 70.0% of muscle,
gill and liver tissue samples respectively recorded the presence of SPs residues in the four fish
species. Forty-four percent (44.4%) of the SPs (bifenhtrin, permethrin, cyfluthrin and
cypermethrin) exceeded the MRL in the muscle tissues of the fishes. Permethrin exceeded MRL
in all the fishes and also recorded the highest incidence rate in all fish musle samples; 100% in
Chrysicththys nigrodigitatus, 90% in Bagrus bayad and 70% in Oreeochromis niloticus. Eight
pyrethroids were detected in the gills of all the fishes in a mean concentration range of 2.00 –
58.60 µg/kg. These are allethrin, bifenthrin, permethrin, cyfluthrin, fenvalerate, fenpropathrin
and deltamethrin, and 9 SPs, with a mean concentration range of 1.69 – 2190.00 µg/kg were
quantified in the liver of the fishes. The lowest mean concentration of 1.69 µg/kg was recorded
for fenpropathrin in B. bayad while the highest value (2190.00 µg/kg) was detected for
permethrin in the same B. bayad. Pyrethroid load in the liver tissues follow the order C.
nigrodigitatus (3679.20 µg/kg) > B. bayad (2628.10 µg/kg) > T. zilli (601.20 µg/kg) > O.
niloticus (571.38 µg/kg).
Pesticides in general have been found to have adverse hispathological effects in fishes, including
shrinkage of liver cells, changes of cell nuclei, and atrophy of some cells (Murthy et al., 2013).
The high occurrence rate of SPs in fish tissues is therefore a cause for concern. Pyrethroids in
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particular are known to be toxic to fishes. When exposed, fishes experience body spasms,
hyperactive swimming, reduced reaction to stimuli and eventual death in some instances
(Palmquist et al., 2012). In addition, they affect reproductive viability in fish and also alter
embryonic and early life stage development. According to Reigart and Roberts (2013),
pyrethroids are lipophilic, do not readily volatilize and strongly adsorb to organic matter. They
therefore easily bioaccumulate in tissues of fishes, causing contamination in the food chain.
When exposed to humans through diet, persons, especially children can show signs of poisoning
such as headache, nausea, convulsion, numbness and tremors among others (Fishel,
2014).Therefore even though pyrethroids emerged as a response to environmentally persistent
organochlorines as well as inorganic pesticides, there is the need to exercise restrained in their
use in order to avert attendant health hazards related to their abuse.
7.4.3 Organphosphorus pesticides concentrations and composition in tissues of fishes
Thirteen of the OPs were quantified in the tissues of the fishes. Liver tissues recorded the
presence of 12; gill and muscle each recorded the presence of 9. The 9 recorded for the muscle
tissue were methamidiphos, chlorpyrifos, malathion, profenofos, phorate, dimethoate,
pirimiphos-methyl, ethoprophos and chloefenvinphos, all within the mean concentration range of
1.60 – 17.00 µg/kg. Four OPs, namely chlorpyrifos, chlorfenvinphos, ethoprophos and
profenofos exceeded the MRL in the muscle of the fishes. In terms of percentage, 30.8% of the
OPs exceeded MRL. Analysis of incidence rate of OPs in the various organs of the fish show that
on the average, 52.5% each of muscle, gill and liver samples recorded their presence. It was
observed that in each fish species, OP load was highest in liver and least in muscle tissues, hence
following the trend liver > gill > muscle. Overall, 27% of all pesticides analysed exceeded MRL
in muscle tissues of the three fish species and the following banned pesticides were identified in
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the various fish tissues: β-lindane, γ-lindane, δ-lindane, heptachlor, aldrin, endrin, DDT,
methamidophos and parathion.
There is generally dearth of research on levels of synthetic pyrethroids and organophosphorus
pesticide in aquatic biota even though these are pesticides that are mostly in use in agriculture
including cultivation of horticultural crops along water bodies. It is therefore difficult to compare
results from the present study to work done by scientists from Ghana and other countries around
the world. However, Essuman et al., (2009) investigated levels of four OPs (dichlorvos,
diazinon, chlorpyrifos and fenitrothion) in muscle tissues of fish species from two lagoons in the
Central Region of Ghana and reported mean concentration range of 0.1 – 0.3 µg/kg. This is far
lower than the range of 1.1 – 17.0 µg/kg reported in this study.
There is the need to conduct more research into levels of pesticides in our food commodities,
particularly the organophosphates since they have higher mammalian toxicity than the other
groups of pesticides (Kazemi et al., 2012a).  Studies on the effect of OPs on fishes by Shoaib et
al., (2012) suggest that reduction of protein levels in tissues of fish occurs when exposed to OPs.
According to them, reduction of tissue protein is as a result of impaired protein synthesis
resulting from hormonal imbalance, impaired cellular metabolism and DNA damage or necrosis
of cells. Moreover, organophosphorus pesticide poisoning through dietary exposure in humans
can be acute and exhibit early symptoms such as muscle twitching, sweating and salivation,
weakness and headache (Kazemi et al., 2012a). Thus apart from considerable effect on fish
nutritive quality due to tissue protein reduction, long-term exposure of organisms to pesticides
may pose a high risk of health hazard to the general public through consumption of pesticide
contaminated fishes. Serious monitoring and regulatory mechanisms must therefore be put in
place by responsible agents to safeguard life.
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7.4.4 Tissue-specific bioaccumulation of pesticides in fish species
In all the four species of fish, the order of decreasing concentrations of pesticides in the various
organs was liver > gill > flesh. Significant difference generally however existed only between
liver and the other tissues. Thus liver was the predominant organ for organochlorine,
organophosphorus and synthetic pyrethroid pesticides bioaccumulation; while muscle and gill
were found to contain concentrations at relatively lower levels (Tables 7.6 – 7.9). This
demonstrates higher bioaccumulation potency in hepatobiliary system than the extrahepatic
tissues (Zhao et al., 2014). Works done by Akan et al., (2013b) and Zhao et al., (2014) also
demonstrated the same trend of OCPs, and OPs levels in liver, gill and muscle tissues of various
fishes, including those in this study. The relative lower residual levels found in muscle of the
fishes indicate muscle tissues are not the target organ for accumulation of lipophillic substances
(Ballesteros et al., 2011).  Since bioaccumulation of toxic chemicals in fishes occurs mainly
through both absorption by external membrane and by dietary uptake (Yang et al., 2007), it was
expected that gill, which is the primary tissue of filter-feeding fishes, and medium for pollutant
accumulation through the gill-water transfer (Yang et al., 2007) will experience higher
bioaccumulation of contaminants (as experienced by Zhao et al., 2013 in another study). Higher
concentrations in this study were rather found in liver of all the fish species studied. This
indicates that food uptake could be the main exposure route for accumulation of pesticides from
the environment (Ballesteros et al., 2011). The pollutants, once they are absorbed by dietary
uptake are metabolized and biotransformed, as they are transported and distributed to various
body organs, including the liver, which receives large volume of toxin-laden blood for
deamination (Zhao et al., 2014). It is therefore not surprising that liver tissues in this study not
only registered very high contaminant concentration, but also a high variety of pesticides; both
parent and metabolite compounds.
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7.4.5 Health Risk Estimates
Tables 7.10, 7.11, 7.12 and 7.13 the health risks for systemic effects associated with pesticide
residues that were quantified in muscle and gill tissues of Tilapia zilli, Oreochromis niloticus,
Chrysicththys nigrodigitatus and Bagrus bayad respectively. Each table comprises computed
dietary exposure to pesticides and the associated hazard indices for age groups up to 1 year; > 1–
11 years and above 11 years (adults or grown-ups). Acceptable daily intakes (ADIs) or
References doses (RfD), which is a level of intake of a chemical that can be ingested daily over a
lifetime without any appreciable risk involved (WHO, 2001) for each pesticide is also indicated..
The ministry of Food and Agriculture of Ghana (MOFA, 2011) quotes the per capita
consumption of fish in Ghana as being 0.82 kg/person/day.
Examination of analysed data presented in Tables 7.10 – 7.13 reveal that aldrin, α-endosulfan,
ethoprophos and to some extent endosulfan sulfate levels in various fishes present health hazard
to children between the ages of 0 – 11 years. In children of 0 – 1 years, hazard indices (HIs) of
2.88, 2.46 and 1.52 were computed for aldrin, α-endosulfan and ethoprophos respectively in T.
zilli; 2.82 and 1.738 for , α-endosulfan in O. niloticus and C. nigrodigitatus respectively; and
2.87 and 1.22 for , α-endosulfan and ethoprophos respectively in B. bayad. Since the HIs for the
pesticides in each case were greater than 1, they pose direct health hazard to human health,
particularly to children between the ages of 0 – 1 year.
For children of ages between 1 – 11 years, , α-endosulfan in all the four fish species pose health
risk since it recorded HIs close to one. Also, the calculated exposure doses for α-endosulfan in
each case were either higher or close to the ADI of α-endosulfan (0.05 µg/person/day). Hazard
indices for adults were all below 1 and their calculated dietary exposure doses as well were all
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below the corresponding ADIs of the pesticides (Tables 7.10 – 7.13) and so no health risk can
directly be imputed or associated with adult consumption of these fishes. The differences of risk
associated to children and adults basically stems from differences in their body weights. This
therefore confirms the fact that children are basically the most vulnerable subgroup of the
population. The younger and/or smaller the body weight, the higher the associated risk. Fianko et
al., (2011) also reported associated health hazard with consumption of tilapia fish from Densu
River by children of age group 1 – 11 years. Their health risk analysis indicated systemic toxicity
for this age group came from concentration levels of α-endosulfan, heptachlor, dieldrin and
endosulfan sulfate. Gbeddy et al., (2012) in a similar study however reported risk levels of no
health concern associated with low OCPs concentrations in T. zilli and C. nigrodigitatus from the
Volta Lake at Kpando Torkor of Ghana. In the present study, Tilapia zilli recorded four
pesticides with HI > 1; Bagrus bayad recorded 2 and Oreochhromis niloticus and Chrysicththys
nigrodigitatus each registered 1 pesticide with HI > 1. Hence, health risk associated with the
consumption of these fishes in decreasing ranking order follows: Tilapia zilli > Bagrus bayad >
Oreochhromis niloticus = Chrysicththys nigrodigitatus. Also, it is observed that α-endosulfan
presents the highest risk of systemic effect since it recorded hazard indices greater than unity in
all the fish species. It is followed by ethoprophos, with HIs greater than 1 in two fish species.  It
should also be emphasized that although HIs of most pesticides were below 1, there was no zero
risk because pesticides were present in all fish tissue samples. Alpha-endosulfan, heptachlor and
endosulfan sulfate for instance are generally persistent, lipophilic and bioaccumulative in the
environment as well as at trophic levels of the food chain (Sun et al., 2006; Fianko et al., 2011).
These pesticides can therefore, through biomagnifications, reach high concentration in tissues of
organisms higher in the food chain, including man, and therefore present food safety challenges.
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7.4.6 Bioconcentration of pesticides in aquatic flora
Information on bioconcentration of pesticides in two aquatic macrophytes: Ceratophyllum sp.and
Nymphaea sp. is presented in Tables 7.14 and 7.15 respectively. Ambient concentration in water
samples from where the two aquatic flora were harvested were used in computing the
bioconcentration factors. A bioconcentration test is conducted to obtain information concerning
the ability of an aquatic species to accumulate a test material directly from water.
Bioconcentration factor (BCF) is the ratio of contaminant concentrations in biota and the
surrounding water (Nowell et al., 1999) and gives an indication of the ability of an aquatic plant
to concentrate chemicals into its system from the surrounding water.
Bioconcentration factors (BCFs) are used to relate pollutant residues in aquatic organisms to the
pollutant concentration in ambient waters. And they give an indication of the kind of health
hazard associated with the consumption of a specific aquatic organism. A high BCF from an
aqueous medium with an ambient low level of chemical concentration indicates the high ability
of an aquatic organism to concentrate the specific chemical into its biological system. This
becomes a concern, particularly if the organism occupies a lower trophic level in food chain in
the ecosystem. Ceratophyllum sp. and Nymphaea sp. as reported by Lass, (2015), FAO, (2015)
and Toowoomba (2000) constitute important sources of plant food for fish and a high level of
chemicals in them means biomagnifications at higher trophic levels and ultimately in man who is
at the apex of the food chain. According to the European Union regulation for registration of
chemicals (2011), a substance fulfils the bioaccumulation criterion when the bioconcentration
factor in aquatic species is higher than 2000; and “very bioaccumulative” criterion when the
bioconcentration factor in aquatic species is higher than 5000. With this in view therefore,
Ceratophyllum particularly in aquatic systems must be of much concern regarding the pollution
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of the aquatic food chain since it has shown the ability of chemicals fulfiling both
bioaccumulation (fenitrothion and chlorpyrifos) and “very bioaccumulative” criterion (diazinon)
in it. Nymphaea sp. can be considered to be a relatively safe primary producer in an aquatic food
chain since its bioconcentration ability is much lower. In spite of the high bioconcentrations of
diazinon, fenitrothion and chlorpyrifos in Ceratophyllum sp., results of health risk analysis of
pesticides in fish tissues show that they are not of much concern. While chlorpyrifos and
fenitrithion occur in appreciable levels in fish tissues, diazinon in particular was detected only
once and in a low concentration of 8 µg/kg in the liver of Tilapia zilli (Table 7.2) and was
therefore not considered for health risk analysis. Reasons for this observation could be that even
though these aquatic macrophytes could be sources of food for the fishes, the fish species might
have effective depurative mechanism for eliminating diazinon from their body system or they
could have alternative preferred sources of food. This however requires further investigation for
conclusive results. However, the high bioconcentration factor of diazinon, fenitrotion and
chlorpyrifos in Ceratophyllum sp should be a pointer to the fact that many more pesticides could
bioconcentrate to alarming levels in the numerous aquatic weeds found in the Afram arm of the
Volta Lake and which could serve as food for many aquatic fauna. This could have an
implication for biomagnifications of pesticide contaminants along the aquatic food chain and
ultimately affect man who is at the apex of most food chains. More research into this area
therefore needs to be carried out to identify aquatic macrophytes that of major concern as food
chains contaminants, by reason of their bioconcentration potential.
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CHAPTER EIGHT
GENERAL CONCLUSION, SUMMARY AND RECOMMENDATIONS
8.1 GENERAL CONCLUSION
The findings from this study established the facts that banned pesticides are still used and
residual load of pesticides on fallowed lands along the banks of the Afram arm of the Volta Lake
are heavy enough to potentially contaminate new crops that will be cultivated on them, even
without further application of insecticides. The banned pesticides detected in the soils from the
fallowed lands were: aldrin, dieldrin, endrin, gamma-lindane, DDT, heptachlor, parathion and
methamidophos. Furthermore, determination of pesticide content of watermelon, onion and
pepper samples showed that while every sample contained quantifiable presence of pesticide,
67% of all the crop samples contained at least, one pesticide with level above the maximum
residue level permitted by the European Union. Estimation of health risk associated with
pesticides present in the food crops indicate that β-lindane, dieldrin and methamidophos have
potential for systemic toxicity in children while heptachlor shows health risk in both children and
adults. Similarly, estimation of health risk associated with consumption of four species of fish:
Tilapia zilli, Oreochromis niloticus, Bagrus bayad and Chrysichthys nigrodigitatus indicates that
levels of heptachlor, α-endosulfan and ethoprohos in them present health hazard in children up to
11 years, while no health risk can directly be imputed or associated with adult consumption of
these fishes. The order of pesticide concentration in the tissues of the fishes was generally: Liver
> Gill > Muscle and the levels of methoxychlor, aldrin, bifenthrin, permethrin, cyfluthrin,
cypermethrin, chlorpyrifos, chlorfenvinphos, ethoprophos and profenofos in the muscle tissues
of the fishes exceeded 0.01mg/kg default EU MRL. Ceratophyllum demersum and Nymphaea
lotus were found to bioconcentrate pesticides. Ceratophyllum demersum in particular fulfilled
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the “very bioaccumulative” criterion since it was able to have bioconcentration factor of
approximately 5000 for diazinon. Comparison of pesticides content of the Afram River during
flood and recess regimes show significantly high incidence rate and concentration levels of
pesticides, as well as high number of pesticides exceeding the WHO MRL during the flood
regime. Drawdown farming is identified as the cause of high concentrations and incidence level
of pesticides in water during the flood regime.  Determination of Afram River bed sediment
toxicity identifies γ-lindane, p,p’-DDE and dieldrin as contaminants whose concentrations have
reached toxicity levels and could therefore pose  health risk to benthic organisms in particular.
It can therefore be concluded that whereas Afram bank farming has a lot of economic benefits to
farmers, it has also resulted in significant contamination of food crops and the environment.
There is the need for farmers to be educated on the importance of observing the Pre-harvest
Interval (PHI). This must however be accompanied by efficient monitoring system to ensure
strict observance. More agricultural extension officers must therefore be trained to carry out
proper monitoring of agricultural activities along the Afram arm of the Volta Lake. Farming in
the drawdown area must be critically evaluated and appropriate policy measures put in place (by
EPA) to reduce pesticide contamination of the water bodies.
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8.2 SUMMARY
The summary of the most important findings and recommendations from the study are
presented:
1. Farmland soils temporary left fallow, for about three months, were found from this study
to have high load of residual pesticides. About 88% of total samples analysed contained
one or more pesticide residues; and approximately 97% of target pesticides analysed were
detected and quantified. Twenty four percent of the target pesticides had levels exceeding
the maximum residue limit (MRL) of the United States Environmental Protection Agency
(USEPA) and these are p,p’-DDT, p,p’-DDD, fenvalerate, cypermethrin, permethrin,
chlorpyrifos, dimethoate, chlorfenvinphos and methamidophos. The presence of banned
pesticides was also established and these were: aldrin, dieldrin, endrin, gamma-lindane,
DDT, heptachloer, parathion and methamidophos.  Further analysis indicated that the
presence of DDT, aldrin and endrin were due to historical use while gamma-lindane
indicates possible current input.
2. Analysis of three food crops, water melon, onion and pepper for pesticide residue and
associated health risk show that 92% of pesticides analysed were detected in 92.9 % of
the total samples analysed. Hundred percent of target organophosphorus and pyrethroid
and 80% of organochlorine pesticides were quantified in the samples. Seventy percent of
the total samples recorded pesticide residues with concentration levels above the Eurpean
Union (EU) Maximum Residue Limit (MRL). Of the target pesticides analysed, β-
lindane, γ-lindane, δ-lindane, γ-chlordane, p,p’-DDE, dieldrin, endrin, methoxychlor,
heptachlor, allethrin, methamidophos, ethoprophos, dimethoate and fenitrothion,
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constituting 37.8%  exceeded the MRL. Estimation of health risk associated with
pesticide present in the food crops indicate that β-lindane, dieldrin and methamidophos
have potential for systemic toxicity in children while heptachlor shows health risk in both
children and adults. So even though fruits and vegetables are excellent sources of dietary
fibre, vitamins, minerals and other natural substances that help protect the body from
chronic diseases the high incidence of pesticides encountered in them in this study raises
food safety concerns.
3. Seasonal rise of water level of the Afram Lake leads to occasional flooding of its
immediate banks that are normally cultivated. Comparison of pesticides content of water
during the flood and recess regimes show significant high incidence rate and
concentration of pesticides, as well as high number of pesticides exceeding the WHO
MRL during the flood regime. Consumption of lake water from the Afram during the
flood regime is thus associated with higher health risk.
4. Toxicity risk assessment of surface sediment of Afram arm of the Volta Lake clearly
identifies γ-lindane, p,p’-DDE and dieldrin as contaminants whose concentration levels
in the sediment pose health risk to benthic organisms and therefore require remediation
attention. Endrin, p,p’-DDT and p,p’-DDD are also potential risks to the aquatic
ecosystem but require further investigation to clearly establish their status.
5. Four common fish species that are a delicacy and important source of protein to
Ghanaians were investigated to ascertain pesticide residue levels in them as well as any
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associated health risk. The fish species are: Tilapia zilli, Oreochromis niloticus,
Chrysichthys nigrodigitatus and Bagrus bayad. The muscle tissues of the fishes were
variously found to be contaminated with methoxychlor, aldrin, bifenthrin, permethrin,
cyfluthrin, cypermethrin, chlorpyrifos, chlorfenvinphos, ethoprophos and profenofos
whose levels all exceeded 0.01mg/kg which is the default EU MRL.
6. Chrysichthys nigrodigitatus and Bagrus bayad contained the highest load of pesticides.
Analysis of muscle, gill and liver tissues show that pesticide content of liver is far higher
than gill which is also greater than that in muscle. This trend is exhibited in all the fish
species however statistical analysis did not showed diferences between residue
concentrations in gill and muscle tissues.
7. The mean concentration range of organochlorine pesticide residue in the tissues of all the
fishes was 0.78 – 4671 µg/kg. Methoxychlor and heptachlor, representing 13% of the
organchlorine pesticide residues exceeded MRL in the fish muscle tissues. The mean
concentration range of synthetic pyrethroids (SPs) in all tissues of the fish species was
1.10 – 49.8 µg/kg and the mean concentration range of organophosphate pesticides in all
tissues was 1.60 – 17.00 µg/kg. About forty-four percent (44.4%) of the SPs exceeded the
MRL in the muscle tissues of the fishes. So also 30.8% of the OPs exceeded MRL in the
muscle tissues of the fishes and 27% of all pesticides analysed exceeded MRL in muscle
tissues of the three fish species and the following banned pesticides were identified in the
various fish tissues: β-lindane, γ-lindane, δ-lindane, heptachlor, aldrin, endrin, DDT,
methamidophos and parathion.
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8. Estimation of health risk indicates that levels of heptachlor, α-endosulfan and ethoprohos
in the fish species present health hazards such as immune system dysfunctions, adverse
pregnancy outcomes and perinatal mortality in children as well as mutagenic and
teratogenic effects. Meanwhile no health risk can directly be imputed or associated with
adult consumption of these fishes since hazard indices for adults were all below 1 and
their calculated dietary exposure doses as well were all below the corresponding
acceptable daily intakes or reference doses of the pesticides.
9. Various aquatic weeds, including Ceratophyllum demersum and Nymphaea lotus,
according to some authors, constitute food source to fishes. Bioconcentration of
pesticides in these two particular aquatic macrophytes was investigated as an indicator to
the possibility of aquatic weeds as source of contamination to fishes. The results
identified Ceratophyllum demersum in particular to have fulfilled the “very
bioaccumulative” criterion since it was able to have bioconcentration factor of
approximately 5000 for diazinon in the aquatic medium.
10. This investigation established that Ceratophyllum demersum as primary producer and a
food that can be browsed by fish is source of serious pesticide contamination of the
aquatic food chain. Since fish constitutes an important source of protein, and fresh water
fish from the Volta Lake in particular constitutes a delicacy to the Ghanaian populace,
Ceratophyllum sp. has an indirect effect of exposing humans to pesticide contamination
and associated health risks.
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8.3 Recommendations
1. Since Pre-Harvest Interval (PHI) has the effect of reducing incidence level and
concentrations of pesticides in food commodities, there is the need for farmers to be
educated on its importance. This must however be accompanied by efficient monitoring
system to ensure strict observance.
2. In order to practice proper application of pesticides, there must be a good motivation and
incentive to do so. One possible way is to provide ready market for all farmers whose
produce meet food quality standard. This implies Ghana Standards Authority, Food and
Drugs Authority, Ghana Environmental Protection Authority and all other stakeholder
institutions must collaborate to ensure random testing of samples from farms as well as
provision of the ready market.
3. More agricultural extension officers must be trained to carry out proper monitoring of
agricultural activities along the Afram arm of the Volta Lake.
4 In view of elevated pesticide content of water associated with flood regimes, as observed in
this study, farming in the draw-down areas of the Afram arm of the Volta Lake must
critically be evaluated by the EPA, Ghana and appropriate policy measures subsequently
put in place to reduce contamination level during flood regimes. For instance it is possible,
over a period of study, to identify the highest water mark during flood regimes and then
prohibit farming activity below this point. If farming must be done in the drawdown at all,
then it must be limited to those crops that do not necessarily require pesticide inputs. This
action will have an added advantage of curbing rising incidence of siltation of the Volta
Lake as a whole.
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5. Other toxicants, mainly carbamates, fungicides and weedicides (such as glyphosate)
whose use are also very high in the study area must be investigated in food commodities
from the study area.
6. Finally, due to the constant exposure of these farmers to pesticides, the levels of various
pesticides in body tissues of the farmers, as a matter of health concern must be
investigated. Dissemination of health implications of such research results among the
farmers could be a huge incentive for right attitude towards pesticide use.
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APPENDICES
Appendix I
Chemicals and Reagents
Acetonitrile, Ethyl acetate, Methylene chloride and acetone were of purest grade (pesticide
grade) and were acquired from BDH laboratory Supplies, England. Certified organochlorine
pesticide standards (Lindane; α-lindane, β-lindane, γ-lindane, and δ-lindane, aldrin, heptachlor,
γ-chlordane, α-endosulfan, p,p’DDE, dieldrin, endrin, β-endosulfan, p,p’-DDT, p,p’-DDD,
Endosulfan-sulfate and Methoxychlor); certified organophosphorus pesticide standards
(Methamidophos, Ethoprophos, Phorate, Diazinon, Fonofos, Dimethoate, Pirimiphos-methyl,
Chlorpyrifos, Malathion, Fenitrothion, Parathion, Chlorfenvinphos, Profenofos) and certified
synthetic pyrethroids pesticide standards (Allethrin, Bifenthrin, Fenpropathrin,  Lamda-
cyhalothrin,  Permethrin,  Cyfluthrin, Cypermethrin, Fenvalerate, Deltamethrin) with certified
purity of at least 99% were obtained from Dr. Ehrenstofer GmBH (Augsburg, Germany).
Sorbent materials used for solid phase extraction were Supelclean Envi-Carb/LC-NH2 SPE
cartridges (500mg/500mg, 6ml size) from Supelco (Bellefonte, PA, USA); silica SPE cartridges
(1000mg/6ml size) purchased from Phenomenex (Torrance, CA, USA) anhydrous magnesium
sulphate and anhydrous sodium sulphate (from BDH laboratory Supplies, England).
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Appendix II: Concentration of pesticides in water under flood regime
Pesticides Mean (µg/L) Range Frequency WHO MRL
(%) (µg/L)
Organochlorines
β-HCH 4.217 1.940-6.310 100 -
γ-HCH 0.065 0.01-0.158 100 2.00
δ-HCH 6.264 1.594-16.788 100 1.00
Heptachlor 0.011 0.01-0.016 80 0.03
Aldrin 1.031 0.627-1.588 100 0.03
α-endosulfan 0.020 0.01-0.071 75 0.01*
p,p'-DDE 0.040 0.01-0.078 90 2.00
Dieldrin 1.385 0.031-5.550 100 0.03
Endrin 1.900 0.216-3.970 100 0.60
Beta endosulfan 0.059 0.01-0.806 95 -
p,p'-DDT 0.066 0.044-0.092 15 2.00
p,p'-DDD 0.036 0.01-0.104 100 2.00
Endosulfan sulfate 0.023 0.01-0.111 100 0.01*
Methoxychlor 0.102 0.01-0.560 100 20.00
Total=15.22 0.01-16.788
Pyrethroids
Allethrin 0.056 0.027-0.091 100 0.05*
Bifenthrin 0.051 0.015-0.112 100 0.05*
Fenpropathrin 0.341 0.045-0.680 85 0.05*
Lamda-cyhalothrin 0.067 0.023-0.234 90 20.00
Permethrin 0.066 0.017-0.233 100 0.05*
Cyfluthrin 0.010 0.010-0.021 60 0.05*
Cypermethrin 0.637 0.034-2.135 75 0.05*
Fenvalerate 0.010 0.010-0.011 55 0.05*
Deltamethrin 0.234 0.010-0.634 100 0.05*
Total=1.47 0.01-2.135
Organophosphate
Methamidophos 0.751 0.040-1.120 45
Phorate 0.010 5 -
Diazinon 0.012 5 0.05*
Fonofos 0.010 20 -
Dimethoate 0.044 0.020-0.064 15 0.05*
Pirimiphos-methyl 0.010 15 6.00
Chlorpyrifos 0.016 0.010-0.027 65 0.05*
Malathion 0.010 0.010-0.010 15 0.05*
Fenitrothion 0.015 0.010-0.026 35 30.00
Parathion 0.010 0.010 10 -
Chlorfenvinphos 0.010 5 0.05*
Profenofos 0.010 5 0.05*
Total=0.91 0.01-1.12
MRL = Maximum residue limit of pesticides allowed by WHO in drinking water.
*  = MRL  adopted by Ghana Standards Authority where that of WHO is not established.
Avg = Average of the mean concentrations of all pesticides in each pesticide group
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Appendix III: Concentration of pesticides in water during recess regime
Pesticides Mean (µg/L) Range Frequency WHO MRL
(%) (µg/L)
Organochlorines
γ-HCH 0.187 0.010-0.269 35 2.00
δ-HCH 0.010 25 1.00
α-endosulfan 0.010 5 0.01*
p,p'-DDE 0.060 5 2.00
Dieldrin 0.084 5 0.03
Endrin 0.033 5 0.60
p,p'-DDT 0.035 0.010 -0.260 75 2.00
p,p'-DDD 0.010 5 2.00
Endosulfan sulfate 0.057 0.010-0.112 10 0.01*
Methoxychlor 0.011 5 20.00
Total=0.497 0.010 -0.269
Pyrethroids
Fenpropathrin 0.036 5 -
Permethrin 0.015 5 0.05*
Cyfluthrin 0.013 0.011-0.016 15 0.05*
Cypermethrin 0.063 0.010-0.370 70 0.05*
Total=0.127 0.010-0.370
Organophosphate
Methamidophos 0.077 0.055-0.115 55 -
Ethoprophos 0.028 0.020-0.036 30 0.05*
Phorate 0.010 10 -
Diazinon 0.013 0.010-0.017 40 0.05*
Dimethoate 0.091 0.012-0.158 25 0.05*
Pirimiphos-methyl 0.010 0.010-0.007 15 6.00
Chlorpyrifos 0.012 0.010-0.014 50 0.05*
Malathion 0.025 0.014-0.037 10 0.05*
Fenitrothion 0.016 0.010-0.020 20 30.00
Chlorfenvinphos 0.064 0.021-0.140 25 0.05*
Profenofos 0.036 0.010-0.068 60 0.05*
Total=0.382 0.010-0.158
MRL = Maximum residue limit of pesticides allowed by WHO in drinking water.
*  = MRL  adopted by Ghana Standards Authority where that of WHO is not established.
Avg = Average of the mean concentrations of all pesticides in each pesticide group
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Appendix IV
One-way  ANOVA to compare pesticides concentrations in muscle, gill and liver tissues of Tilapia zilli
Sum of Squares df Mean Square F Sig.
β-HCH Between Groups 230.987 2 115.493 3.718 .047
Within Groups 497.068 16 31.067
Total 728.055 18
Methoxychlor Between Groups 1289.913 2 644.957 141.426 .000
Within Groups 50.164 11 4.560
Total 1340.077 13
Permethrin Between Groups 547437.026 2 273718.513 7.119 .008
Within Groups 499858.144 13 38450.626
Total 1047295.170 15
Metamedophos Between Groups 710.793 2 355.396 21.531 .001
Within Groups 132.047 8 16.506
Total 842.840 10
Chlorpyriphos Between Groups .012 2 .006 .000 1.000
Within Groups 124.893 5 24.979
Total 124.905 7
All analyses done at 0.05 confidence interval
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Appendix V
One-way ANOVA comparing pesticides concentrations in muscle, gill and liver of Oreochromis
niloticus
Sum of Squares df Mean Square F Sig.
BHCH Between Groups 377.943 2 188.971 2.744 .087
Within Groups 1446.348 21 68.874
Total 1824.291 23
Permethrin Between Groups 366849.403 2 183424.702 197.058 .000
Within Groups 14893.022 16 930.814
Total 381742.425 18
Cypermethrin Between Groups 4040.317 2 2020.158 8.648 .003
Within Groups 3504.137 15 233.609
Total 7544.453 17
Deltamethrin Between Groups 20.102 2 10.051 1.120 .396
Within Groups 44.872 5 8.974
Total 64.975 7
All analyses done at 0.05 confidence interval
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Appendix VI
One-way ANOVA comparing pesticides concentrations in muscle, gill and liver of Chrysichthys
nigrodigitatus
Sum of Squares df Mean Square F Sig.
β-HCH Between Groups 1501.262 2 750.631 1.832 .192
Within Groups 6555.901 16 409.744
Total 8057.163 18
Methoxychlor Between Groups 5.000E7 2 2.500E7 10.833 .003
Within Groups 2.308E7 10 2307866.624
Total 7.308E7 12
Permethrin Between Groups 3835606.917 2 1917803.459 5.989 .008
Within Groups 7365418.834 23 320235.601
Total 1.120E7 25
Cyfluthrin Between Groups 213166.141 2 106583.071 9.319 .002
Within Groups 182993.985 16 11437.124
Total 396160.126 18
Fenvalerate Between Groups 1097395.605 2 548697.802 4.566 .026
Within Groups 2042762.395 17 120162.494
Total 3140158.000 19
All analyses done at 0.05 confidence interval
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Appendix VII
One-way ANOVA comparing pesticides concentrations in muscle, gill and liver of Bagrus bayad
Sum of Squares df Mean Square F Sig.
BHCH Between Groups 2000.597 2 1000.298 5.795 .011
Within Groups 3107.021 18 172.612
Total 5107.618 20
Methoxychlor Between Groups 304850.486 2 152425.243 7.678 .004
Within Groups 337473.371 17 19851.375
Total 642323.857 19
Permethrin Between Groups 2.551E7 2 1.275E7 9.729 .001
Within Groups 3.146E7 24 1310784.088
Total 5.696E7 26
Cyfluthrin Between Groups 294141.639 2 147070.820 19.582 .000
Within Groups 105145.181 14 7510.370
Total 399286.820 16
Chlorfenvinphos Between Groups 140.188 2 70.094 2.554 .158
Within Groups 164.668 6 27.445
Total 304.856 8
Ethoprophos Between Groups 1467.481 2 733.740 27.530 .002
Within Groups 133.261 5 26.652
Total 1600.742 7
Profenofos Between Groups 680.329 2 340.165 2.200 .181
Within Groups 1082.540 7 154.649
Total 1762.869 9
All analyses done at 0.05 confidence interval
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