1 
 
 
 
PESTICIDE CONTAMINATION OF FRUITS AND VEGETABLES – A 
MARKET-BASKET SURVEY FROM SELECTED REGIONS IN GHANA.     
 
 
 
BY 
ERIC ASIEDU 
(10180167) 
 
 
 
 
 
 
 
 
 
 
 
THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN 
PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF MPHIL 
CHEMISTRY DEGREE. 
 
 
 
JUNE 2013 
 
 
 
 
 
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DEDICATION 
This project is dedicated to my mum Grace Nyarko and my sister, Hannah Asiedu. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                    
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DECLARATION 
 I do hereby declare that, except for references to works of other researchers which have been 
cited, this work is the result of my own research carried out under the supervision of Prof Robert 
Kingsford-Adaboh and Dr. Raphael Klake all of Chemistry Department, University of Ghana, 
and has not been presented previously by anyone anywhere as fulfillment for a degree or any 
certificate.  
 
 
……………………………………………………………… 
ERIC ASIEDU 
(STUDENT) 
 
 
 
 
………………………………………………………… 
PROF ROBERT KINGSFORD- ADABOH 
 (MAIN SUPERVISOR) 
 
 
………………………………………………………… 
DR. RAPHAEL KLAKE 
(CO-SUPERVISOR) 
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ACKNOWLEDGEMENT 
 Thanks be to the Lord Jesus Christ for taking me through this project work successfully. I wish 
to also express my profound gratitude to my supervisors Prof Kingsford Adaboh and Dr. Raphael 
Klake all of Chemistry Department, for their support and understanding which made the 
completion of this project successful. 
Thanks also go to Mr. Bob Essien for providing the necessary reagents and apparatus for my 
work. Last but not the least; thanks go to all other individuals who in diverse ways helped to 
make this project a success. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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                                                    ABSTRACT 
A market- basket survey was carried out with the aim of determining the concentration levels of 
pesticides, in lettuce, garden eggs, pineapple and mango from some selected regions in Ghana and to 
assess the potential health risk associated with exposure to the pesticide residues from fruits and 
vegetables consumption. A total of 192 fresh samples of fruits and vegetables were randomly collected 
under normal purchase conditions from 12 major towns and cities in the three regions of Ghana. The 
samples were extracted and analyzed for organophosphates, synthetic pyrethroids and organochlorine 
pesticides. The percentage of samples of fruits and vegetables with pesticide residues in Lettuce, Garden 
eggs, Pineapple and Mango were 52%, 40%, 45%, 48% respectively and concentrations of pesticides did 
not vary significantly in samples as well as the sampling areas (p>0.05) even though there were 
differences in residual concentrations of pesticides . The differences in residual concentrations of 
pesticides could be due to different agricultural practices adopted by farmers and also accessibility of the 
pesticides. The average residue concentrations range from 0.01-0.45 mg/kg, 0.01-0.30 mg/kg and 0.01-
1.27 mg/kg for organophospates, synthetic pyrethroids and organochlorine pesticides respectively. 
Lindane, chlorpyrifos and cypermethrin were the most frequent organochlorine, organophosphate and 
synthetic pyrethroid pesticides respectively while lettuce was the most frequently contaminated sample. 
Comparing the concentration levels of organochlorine pesticides residue with the maximum residue limits 
(MRLs) adopted by the FAO/WHO Codex Alimentarious Commission shows that some of the fruits and 
vegetables sold on Ghanaian markets are contaminated even though the levels are generally low. Health 
risk analysis indicates that heptachlor in particular may be of public concern since its concentration levels 
exceeded the reference dose in all the four different types of samples analyzed indicating a great potential 
for systemic toxicity to consumers in Ghana. 
 
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TABLE OF CONTENTS 
DEDICATION…………………………………………………………………………… i 
DECLARATION ………………………………………………………………………… ii 
ACKNOWLEDGMENT ………………………………………………………………… iii 
ABSTRACT ……………………………………………………………………………… iv 
TABLE OF CONTENTS ………………………………………………………..…….… v 
LIST OF FIGURES ………………………………………………………..……………… viii 
LIST OF TABLES ………………………………………………………………………... xi 
 
CHAPTER ONE 
1.0 INTRODUCTION ………………………………………….……………..…. 1 
1.1 Background ……………………………………………………...……...…………. 1 
1.2   Problem statement ………………………………………………...…………….… 3 
1.3   Objectives of the research ………………………………………………...…….… 4 
1.4 Hypothesis ………………………………...………..……………………………… 4 
1.5   Justification …………………………………………..…………………………… 4 
 
CHAPTER TWO 
2.0   LITERATURE REVIEW………………………………………………………… 6 
2.1   Introduction……………………………………………………………………… 6 
2.2   Classification of pesticides………………………………………………………… 8 
2.2:1 Organochlorine pesticides………………………………………………………… 9 
2.2.2 Organophosphate pesticides……………………………………………………… 12 
2.2.3 Carbamates pesticides…………………………………………………………… 14 
2.2.4 Synthetic pyrethroids pesticides………………………………………………… 15 
2.3.0 Pesticide metabolites……………………………………………………………… 17 
2.3.1 Trends in pesticide use in Ghana………………………………………………… 19 
2.3.2 Studies on pesticides in Ghana………………………………………………… 21 
2.4 Health impacts of pesticides………………………………………………………… 23 
2.4.1 Toxicity to Humans………………………………………………………………… 24 
2.4.2 Pesticide accumulation in biological systems…………………………………… 25 
2.4.3 Biomagnification………………………………………………………………… 25 
2.4.4 Toxicology……………………………………………………………………… 26 
2.4.5 Dose – Response Relationship ………………………………………………… 27 
2.5   Risk Assessment …………………………………………………………………… 28 
2.6   Analytical methods for pesticide residue analysis………………………………… 29 
2.6.1 Sampling…………………………………………………………………………… 30 
2.6.2 Extraction…………………………………………………………………………… 30 
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2.6.3 Clean-up of sample extract………………………………………………………… 36 
2.6.4 Identification and quantification of Pesticide Residue…………………………… 39 
 
 CHAPTER THREE 
3.0 METHODOLOGY…………………………………………………………………… 42 
3.1 Study Area…………………………………………………………………………… 42 
3.1.2 Sampling and storage …………………………………………………………….. 44 
3.1.3 Reagents………………………………………………………………………….. 44 
3.1.4 Apparatus ……………………………………………………………………….. 44 
3.1.5 Cleaning of glass wares ………………………………………………………… 45 
3.1.6 Preparation of pesticide (organochlorine) mixture standard solution ………… 45 
3.1.7 Extraction …………………………………………………………………………. 45 
3.1.8 Solid-phase extraction (SPE) clean-up of extract………………………………. 46 
3.1.9 Calibration curve………………………………………………………………… 46 
3.2 Gas Chromatographic Analysis ………………………………………………….. 47 
3.2.1 Quantification of pesticides results …………………………………………… 47 
3.2.2 Quality control and quality assurance ………………………………………… 47 
3.2.3 Recovery Test ………………………………………………………………….. 48 
3.2.4 Limit of detection (LOD) ……………………………………………………… 48 
3.2.5 Data analysis …………………………………………………………………… 48 
 
CHAPTER FOUR  
4.0 RESULTS AND DISCUSSION …………………………………………………. 50 
4.1:  Introduction ……………………………………………………………………. 50 
4.1.1: Percentage of samples of fruits and vegetables with pesticide residues…….. 50 
4.12: Occurrence and distribution of organophosphates and synthetic pyrethroids in  
samples from Greater the Accra Region ……………………………………………...... 52 
4.13: Occurrence and distribution of organophosphates and synthetic pyrethroids in 
 samples from Central Region …………………………………………………………. 57 
4.14: Occurrence and distribution of organophosphates and synthetic pyrethroids in 
 samples from Eastern Region ……………………………………………………………. 62 
4.15: Occurrence and distribution of organophosphates and synthetic pyrethroids in 
 samples from all sampling areas ………………………………………………………… 68  
4.16: Occurrence and distribution of organochlorine in samples from Greater Accra  
Region……………………………………………………………………………………. 75 
4.17: Occurrence and distribution of Organochlorine in samples from Central  
Region ………………………………………………………………………………….. 79 
4.18: Occurrence and distribution of Organochlorine pesticides in samples from  
Eastern Region ………………………………………………………………………. 83 
4.19: Occurrence and distribution of organochlorine pesticides in samples from all  
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the sampling areas …………………………………………………………………. 87 
4.2: Tolerance limits ………………………………………………………………….. 93  
4.21: Health Risk Assessment ……………………………………………………..  95 
 
CHAPTER FIVE 
5.0 CONCLUSION AND RECOMMENDATIONS ………………………………… 101 
5.1 Conclusions ……………………………………………………………………… 101 
5.2 Recommendations………………………………………………………………… 102  
 
 
REFERENCES ……………………………………………………………………… 103 
Appendix A…………………………………………………………………………… 120 
Appendix B ………………………………………………………………………….. 121 
Appendix C ………………………………………………………………………….. 122 
Appendix D …………………………………………………………………………. 123 
Appendix E ………………………………………………………………………….. 124 
Appendix F ………………………………………………………………………….. 124 
Appendix G ………………………………………………………………………… 125  
Appendix H …………………………………………………………………………. 125  
Appendix I …………………………………………………………………………… 126  
Appendix J …………………………………………………………………………… 127 
Appendix K …………………………………………………………………………… 128  
Appendix L ………………………………………………………………………….. 129  
Appendix M …………………………………………………………………………. 130 
Appendix N …………………………………………………………………………… 131 
Appendix O …………………………………………………………………………. 132 
Appendix P ………………………………………………………………………….. 133 
 
 
 
 
 
 
 
 
 
 
 
 
 
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LIST OF FIGURES 
 
Figure 2.2.1: Structural formulae of some organochlorine pesticides…………………. 11 
Figure 2.2.3: The three main classes of organophosphates with examples ………….. 13 
Figure 2.2.4: Structural formulae of some carbamate pesticides …………………….. 15 
Figure 2.2.5: Structural formulae of some synthetic pyrethroids pesticides …………. 16 
Figure 3.1: Map showing the study areas …………………………………………….. 43 
Figure 4.11: Graph showing the  percentage of samples with one or more pesticide 
 residues……………………………………………………………………………….. 51 
Figure 4.12a: Mean concentration levels of organophosphates in fruits and vegetables  
from the Greater Accra Region …………………………………………………………. 55 
Figure 4.12b: Mean concentration levels of synthetic pyrethroids in fruits and 
vegetables from the Greater Accra Region ……………………………………………. 55 
Figure 4.12c: Mean concentration levels of organophosphates and synthetic pyrethroid 
in lettuce from the Greater Accra Region …………………………………………….. 55 
Figure 4.12d: Mean concentration levels of organophosphates and synthetic  
pyrethroids in garden eggs from the Greater Accra Region ………………………….. 55 
Figure 4.12e: Mean concentration levels of organophosphates and synthetic  
pyrethroids pineapple from the Greater Accra Region ………………………………… 56 
Figure 4.12e: Mean concentration levels of organophosphates and synthetic pyrethroids  
mango the Greater Accra Region ………………………………………………….. …. 56 
Figure 4.13a: Mean concentration levels of organophosphates in fruits and vegetables 
 from the Central Region ……………………………………………………………….. 60 
Figure 4.13b: Mean concentration levels of synthetic pyrethroids in fruits and vegetables 
 from the Central Region ……………………………………………………………….. 60 
Figure 4.13c: Mean concentration levels of organophosphates synthetic pyrethroids 
 in lettuce from the Central Region ……………………………………………………… 60 
Figure 4.13d: Mean concentration levels of organophosphates and synthetic  
pyrethroids in garden eggs from the Central Region …………………………………… 60 
Figure 4.13e: Mean concentration levels of organophosphates and synthetic 
pyrethroids in pineapple from the Central Region  ……………………………………. 61 
Figure 4.13f: Mean concentration levels of organophosphates and synthetic 
 pyrethroids in mango from the Central Region …………………………………….. 61 
Figure 4.14a: Mean concentration levels of organophosphates and synthetic pyrethroid  
in fruits and vegetables from the Eastern Region ………………………………………. 66 
Figure 4.14b: Mean concentration levels of synthetic pyrethroids in fruits and vegetables  
from the Eastern Region ………………………………………………………………….. 66  
Figure 4.14c: Mean concentration levels of organophosphates and synthetic 
 pyrethroids in lettuce from the Eastern Region ………………………………………. 66 
Figure 4.14c: Mean concentration levels of organophosphates and synthetic pyrethroids 
 in lettuce from the Eastern Region ………………………………………………….. 66 
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Figure 4.14e: Mean concentration levels of organophosphates and synthetic  
pyrethroids in pineapple from the Eastern Region ………………………………….. 67 
Figure 4.14f: Mean concentration levels of organophosphates and synthetic  
pyrethroids in mango from the Eastern Region lettuce ……………………………….. 67 
Figure 4.15a: Mean concentration levels  of organophosphates in samples from all the  
 sampling areas ………………………………………………………………………….. 72 
Figure 4.15b: Mean concentration levels  of synthetic pyrethroids in samples from  
all the sampling areas …………………………………………………………………….. 72 
Figure 4.15c: Mean concentration levels of organophosphates in lettuce from all the  
sampling areas ……………………………………………………………………………. 72 
Figure 4.15d: Mean concentration levels  of organophosphates in garden eggs from  
all the sampling areas …………………………………………………………………….. 72 
Figure 4.15e: Mean concentration levels  of organophosphates in pineapple from all  
the sampling areas ……………………………………………………………………….. 73 
Figure 4.15f: Mean concentration levels  of organophosphates in mango from all the  
sampling areas ……………………………………………………………………………. 73 
Figure 4.15g: Mean concentration levels  of synthetic pyrethroids in lettuce from all  
sampling areas ……………………………………………………………………………. 73 
Figure 4.15h: Mean concentration levels of synthetic pyrethroids in garden eggs 
 from  all sampling areas ………………………………………………………………….. 73 
Figure 4.15i: Mean concentration levels  of synthetic pyrethroids in pineapple from 
 all the sampling areas ………………………………………………………………… 74 
Figure 4.15j: Mean concentration levelsof synthetic pyrethroids in mango from all the 
 sampling areas ……………………………………………………………………….. 74 
Figure 4.16a: Mean concentration levels of organochlorine pesticides in fruits and 
 vegetables from the Greater Accra Region ……………………………………………… 77 
Figure 4.16b: Mean concentration levels of organochlorine pesticides in lettuce from 
the Greater Accra Region …………………………………………………………………. 78  
Figure 4.16c: Mean concentration levels of organochlorine pesticides in garden eggs 
 from the Greater Accra Region ………………………………………………………… 78 
Figure 4.16d: Mean concentration levels of organochlorine pesticides in pineapple  
from the Greater Accra Region ………………………………………………………….. 78 
Figure 4.16e: Mean concentration levels of organochlorine pesticides in mango from 
 the Greater Accra Region …………………………………………………………… 78 
Figure 4.17a: Mean concentration levels of organochlorine pesticides in fruits and 
 vegetables from the Central Region …………………………………………………….. 81 
Figure 4.17b: Mean concentration levels of organochlorine pesticides in lettuce from 
 the Central Region ……………………………………………………………………… 81 
Figure 4.17c: Mean concentration levels of organochlorine pesticides in garden eggs 
 from the Central Region ………………………………………………………………… 81 
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Figure 4.17d: Mean concentration levels of organochlorine pesticides in pineapple  
from the Central Region …………………………………………………………………. 82 
Figure 4.17e: Mean concentration levels of organochlorine pesticides in mango from  
the Central Region ……………………………………………………………………….. 82 
Figure 4.18a: Mean concentration levels of organochlorine pesticides in fruits and  
vegetables from the Eastern Region …………………………………………………….. 85 
Figure 4.18b: Mean concentration levels of organochlorine pesticides in lettuce from  
the Eastern Region ……………………………………………………………………… 86  
Figure 4.18c: Mean concentration levels of organochlorine pesticides in garden eggs 
 from the Eastern Region ………………………………………………………………. 86 
Figure 4.18d: Mean concentration levels of organochlorine pesticides in pineapple  
from the Eastern Region ………………………………………………………………… 86 
Figure 4.18e: Mean concentration levels of organochlorine pesticides in mango from  
the Eastern Region ………………………………………………………………………… 86 
Figure 4.19a: Mean concentration levels of organochlorine pesticides in fruits and  
vegetables from all sampling areas …………………………………………………….. 97 
Figure 4.19b: Mean concentration levels  of organochlorine pesticides in lettuce  
from all samplingareas ………………………………………………………………… 97 
Figure 4.19c: Mean concentration levels of organochlorine pesticides in garden eggs 
 from all sampling areas ……………………………………………………………….. 97 
Figure 4.19d: Mean concentration levels of organochlorine pesticides in pineapple  
from all sampling areas ……………………………………………………………… 98 
Figure 4.19e: Mean concentration levels  of organochlorine pesticides in mango 
 from all samplingareas …………………………………………………………………. 98 
                                                
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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LIST OF TABLES 
 
Table 2.0: Volume of pesticide products (tons) imported into Ghana from 
 2002-2006……………………………………………………………………………... 21 
Table 2.1:  Methods of sample extraction and clean-up……………………………… 38 
Table 4.11: Percentage of samples with one or more pesticide residue …………….. 51 
Table 4.12: Concentrations (mg/kg) of organophosphates and synthetic pyrethroids in 
 samples from Greater the Accra Region ………………………………………………. 54 
Table 4.13: Concentrations (mg/kg)  of organophosphates and synthetic pyrethroids in 
 samples from the Central Region ……………………………………………………… 59 
Table 4.15: Concentrations (mg/kg)  of organophosphates and synthetic pyrethroids in  
samples from the Eastern Region ……………………………………………………. 65  
Table 4.15: Concentrations (mg/kg)  of organophosphates and synthetic pyrethroids in 
 samples from all the sampling areas …………………………………………………… 71 
Table 4.16: Concentrations (mg/kg) of oganochlorine pesticide residues detected in  
samples from the Greater Accra Region ………………………………………………… 77 
Table 4.17: Concentrations (mg/kg) of oganochlorine pesticide residues detected in  
samples from the Central Region ……………………………………………………….. 80 
Table 4.18: Concentrations (mg/kg) of oganochlorine pesticide residues detected in  
samples from the Eastern Region ………………………………………………………. 85 
Table 4.19: Concentrations (mg/kg)  of organochlorine pesticide residues detected  
in samples from all the sampling areas …………………………………………………. 90 
Table 4.20: Highest organochlorine pesticide residue concentration found in lettuce,  
garden eggs, pineapple, mango from the selected sampling areas compared with 
 FAO/WHO maximum residue limits  ………………………………………………….. 93 
Table 4.21: Health risk estimates for systemic effects associated with pesticide  
residues in lettuce ……………………………………………………………………….. 97 
Table 4.22: Health risk estimates for systemic effects associated with pesticide  
residues in garden eggs ……………………………………………………………….. 98 
Table 4.23: Health risk estimates for systemic effects associated with pesticide  
residues in pineapple …………………………………………………………………… 99 
Table 4.24: Health risk estimates for systemic effects associated with pesticide 
 residues in mango …………………………………………………………………….. 100 
 
 
 
 
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CHAPTER ONE 
                                          1.0 INTRODUCTION 
1.1   Background  
Feeding the ever increasing human population is one of the challenges facing the world today. 
The high demand for food has led to the use of fertilizers and pesticides in Agriculture in order to 
boost food production. The use of pesticides started with the introduction of arsenical pesticides 
and organic compounds such as tar, petroleum oils, and dinitrophenol emulsions (Ntow, 2005). 
Antinnonin (dinitrocresol) is considered the first synthetically produced pesticide for which a 
patent has been applied. In 1939, after the discovery of insecticidal properties in DDT, a 
systematic search for synthetic organic products was launched (Kumar, 1987). 
 
 Pesticides are widely used in agriculture to increase the yield, improve the quality, and extend 
the storage life of food crops. Thus pesticides protect food crops in the field against a wide range 
of pests and diseases. It is estimated that without pesticides, two-thirds of all crops in the field 
would be lost, depriving many people of food and increasing malnutrition (Botwe, 2006). 
However, the lack of informed choices, on the use of pesticides has resulted in the repeated and 
indiscriminate use of pesticides which has exposed farmers and consumers to health hazards due 
to their toxic residues that persist in foods after application (Biney, 2001). These residues may 
either cause acute or chronic toxicity in humans after consumption of the treated crop (Ntow, 
2005). These toxic effects are more apparent in vegetables and fruits since they are sometimes 
consumed fresh. 
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Today many agricultural pesticides are available which are usually organochlorines, carbamates, 
pyrethroid or phenoxy compounds. The organochlorine pesticides in addition to their toxic 
nature, resist degradation and persist in the environment for a long time (Botwe, 2007). They are 
lipophilic and may accumulate in the human body when small amounts are taken up in food. The 
agricultural use of pesticides (mostly organochlorine pesticides) has been banned or severely 
restricted in many developed countries due to their adverse effect on human health. The 
Stockholm convention on persistent organic pollutants (POPs) which was signed in May 2001 is 
geared towards banning these poisonous chemicals worldwide. Nine out of the twelve chemicals 
targeted for global elimination under this treaty are organochlorines. The bans and restrictions 
are not effective and so these   pesticides find their way into developing countries and Ghana is 
no exception (Botwe, 2007). 
Though it is of the general opinion that household processing methods such as washing and 
boiling remove pesticide residues in fruits and vegetables, it is not always so. Washing and 
boiling may not remove the pesticides (especially the organochlorines) completely (Bull, 1982) 
and this may be a threat to public health if they exceed the maximum permissive levels. It is 
therefore necessary to assess the levels of pesticides in the selected fruits and vegetables and to 
estimate the potential health risk associated with its dietary exposure. 
 
 
 
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1.2   Problem statement  
The increasing demand of vegetables, fruits and other food crops for local use as well as for 
export has encouraged the use of pesticide in farming for the purpose of controlling and reducing 
the effect of insects in food production. Organochlorine pesticides are resistant to environmental 
degradation through chemical, biological and photolytic processes and as a result bio-accumulate 
in living tissues and in food chains which causes a resultant negative impact on human health 
and environment. These synthetic organic chemicals therefore contribute to many acute and 
chronic illnesses such as cancers and hormone disruptions (Amoah et al, 2006). As a result of the 
toxicity associated with Organochlorine pesticides, there is an international effort to eliminate or 
minimize Organochlorine pesticides and related compounds from the environment. 
 
It is estimated that 87% of farmers in Ghana use pesticides in vegetable and fruit production 
(Dinham, 2003). In Ghana, even though there is a ban on Organochlorine pesticides such as 
aldrin, dieldrin, DDT, and lindane (gamma-HCH), due to weak import control and lack of 
logistics to monitor these pesticides, the ban on these pesticides may be ineffective. Ready made 
formulations in soft drink bottles and other unlabelled liquid containers sold to farmers may 
contain some of these restricted or banned pesticides. Thus, even though DDT is highly 
restricted, DDT residues have been found in some Ghanaian vegetables and fruits (Ntow et al, 
2001; Amoah et al, 2006). 
Potential health risk assessment due to dietary exposure to pesticide residue in fruits and 
vegetables has been undertaken in other parts of the world (National Research Council, 1993). 
However, in Ghana, very little has been done on health risk assessment, and it is therefore 
necessary to conduct a health risk assessment on these vegetables and fruits. This study will 
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therefore be a step towards the assessment of health risks due to pesticide residue (especially 
organochlorine) exposures from consumption of selected vegetables and fruits in Ghana. 
1.3    Objectives of the research 
The main objectives of the study were to: 
  Determine the levels of pesticide residues in the selected fruits and vegetables sold in 
some Ghanaian markets. 
  Estimate the potential health risk associated with the daily intake of the selected fruits 
and vegetables. 
 
 
1.4   Hypothesis 
H0: Vegetables and fruits sold on Ghanaian markets are contaminated with pesticide residues. 
H1: Vegetables and fruits sold on Ghanaian markets are not contaminated with pesticide residues 
 
 
1.5   Justification 
Fruits and vegetables form the major component of food consumed by humans because of its 
high nutritional value for the body and is therefore not surprising to know that many nutritional 
experts and other health professionals recommend the daily intake of fruits and vegetables. 
However, in spite of the benefits gained from the consumption of these fruits and vegetables 
there have been reports of diseases such as cancer, endocrine disruptions, immunological effects, 
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neurotoxicity and many others which are attributed to continuous use of contaminated fruits and 
vegetables (Hodgson and Levi, 2003). This incidence of contamination in fruits and vegetables 
has raised public concern because of its adverse effects on human health.  
Many researchers have attributed this contamination in these fruits and vegetables to the 
continuous use of banned and approved pesticides by farmers during crop production (Ntow, 
2005). In Ghana pesticide use in crop production is a common practice and recent studies reveal 
levels of pesticide residues especially organochlorine in fruits and vegetables from some 
Ghanaian markets and farms (Bempah et al, 2011; Ntow et al, 2005). In view of the public health 
significance of pesticide residues and the uncertainty that exist regarding the long term effects of 
low dose exposure of these pesticides, this present study therefore becomes relevant in updating 
data on pesticide residue levels in some selected vegetables and fruits sold in Ghana. 
 
 
 
 
 
 
 
 
 
 
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     CHAPTER TWO 
2.0     LITERATURE REVIEW 
2.1  Introduction 
The insurgence of pests, diseases and other plant pathogens has necessitated the use of 
pesticides. This is to eliminate both pre-harvest and post-harvest losses so as to maintain high 
yield.  The rapid increase in population growth and the need to maintain food security especially 
in developing countries has increased the use of these pesticides. It has been reported that the use 
of pesticides has increased massively with an estimated 2.5 million tons (worldwide) used  
annually (Farag et al, 2011). 
 
Pesticides are substances or mixture of substances whose use is supposed to prevent, destroy, 
repel or mitigate any pest. They may be of biological origin (such as virus or bacterium) or 
chemical origin (such as DDT or Cypermethrin). Also pesticides can be naturally occurring or 
manmade with numerous applications. Hill and Walter (1994) stated that pesticides application 
to the target pest comes in innumerable formulations and delivery systems. Some come in the 
form of sprays, baits and slow-release diffusions. 
 
Historians have traced the use of pesticides to the time of Homer around 1000 BC. However, the 
earliest recorded application of pesticides was the burning of sulphur to fumigate Greek homes 
(Metacalf, 1980). Other inorganic chemical pesticides that emerged around the same time were 
copper, arsenic and lead. These inorganic pesticides were extensively used until the early 20th 
century when they were banned due to their high persistence and their non-specific toxicity. 
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Pesticides are quite toxic to humans and other mammals which sometimes have resulted in 
deaths (Baird and Cann, 2004). 
 
During and after the Second World War, another form of pesticides evolved. These were the 
synthetic organic pesticides. The introduction of synthetic organic pesticides was seen as a major 
effort in the elimination of pests which hitherto had been a major concern in the security of food 
to the world’s population. Unfortunately, the introduction of these synthetic organic pesticides 
was not very successful. Most pests have become resistant to synthetic organic pesticides. Again, 
these synthetic organic pesticides have caused a growing number of environmental and health 
problems (Metcalf, 1980). 
 
Barnett (1997) reported that minimal exposure to pesticides in the environment and result from 
their residues ingested through food and water has the tendency of causing chronic health effects 
many years after. Other researchers (Nollet, 2004) have reported a wide range of human health 
hazards emanating from short term impacts such as headaches and nausea to chronic impacts like 
cancer, reproductive harm and endocrine disruption. 
 
Indiscriminate use of pesticides especially at the fruiting and pre-harvesting stages; and non-
adoption of safe waiting periods have led to pesticides residues accumulating in most 
consumable vegetables and fruits especially in developing countries. The contamination of 
vegetables and fruits with pesticides has been reported in many developing countries (Amoah et 
al, 2006). Farmers’ quest to get better yield and quality products have resulted in repeated 
application of pesticides during the entire growing period of vegetables and fruits. 
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Clarke et al (1997) stated that despite the potential health risk derived from the use of pesticides, 
they have been shown to decrease immensely the volume of crop loss both before and after 
harvest. In India, Brinjal (Solanummelongena L.), an important local vegetable crop grown 
extensively suffers heavily at the fruiting stage due to attack of shoot and fruit borers causing 
70 % loss. The use of pesticides has reduced this loss drastically (Misra and Singh, 1996). 
Vegetables and fruits are the fresh and edible portions of most plants. Vegetables and fruits have 
valuable nutrients which build up and repair the body tissue, hence the need to produce them in 
greater volumes. 
 
2.2   Classification of pesticides 
Pesticides are one broad area where so many classes exist depending on what is of interest. For 
instance US EPA (2008) and Walter (2005) have classified pesticides by their target organisms. 
In this regard, insecticides, fungicides, herbicides and rodenticides are groups of pesticides that 
target insects, fungi, herbs (plants) and rodents respectively. In addition to the classes mentioned 
above, pesticides can also be classified as organic or inorganic pesticides (Baird, 1997).  
 
The inorganic pesticides are made from naturally occurring minerals and have varying modes of 
action including interfering with conversion of energy within cells which can cause death and 
desiccation (Agbeve, 2011). Some examples of inorganic pesticides are boric acid (H3BO3) silica 
gel (Na2SiO3), sodium fluoride (NaF) and those that contain heavy metals such as mercury, 
arsenic and lead (Baird, 1997). Organic pesticides consist of compounds containing mainly 
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carbon and hydrogen and may contain other elements such as chlorine, nitrogen, sulphur, tin and 
phosphorus.  
 
Organic pesticides can further be grouped into synthetic and natural organic pesticides. The 
synthetic organic pesticide can further be grouped into four major classes as organochlorines, 
organophosphates, carbamates and synthetic pyrethroids. 
 
In addition to the classes mentioned above, the Ghana Environmental Protection Agency which 
is the sole agency responsible for registering pesticides (Act 528 ,1996) has classified pesticides 
as general use pesticides, restricted use pesticides and suspended or banned pesticides. Pesticides 
that fall under general use do not have an unreasonable adverse effect on the environment. 
Banned pesticides have great effects on the environment, humans and crops are therefore not 
supposed to be used in Ghana. Examples of banned pesticides are DDT, aldrin, dieldrin, 
heptachlor. Pesticides whose application may lead to unreasonable adverse effects on humans, 
animals or the environment fall under restricted pesticides. Examples of restricted pesticides 
used in Ghana include; endosulfan (thiodan), and gamma HCH (Lindane). 
 
2.2:1 Organochlorine pesticides 
The organochlorine pesticides are synthetic organic pesticides which are made up of 
predominantly carbon, hydrogen, chlorine and sometimes oxygen and sulphur. They are also 
known by other names such as chlorinated hydrocarbons, chlorinated organics, chlorinated 
insecticides and chlorinated synthetics. They were used extensively from the 1940s through the 
1960s in agriculture and mosquito control. Generally, there are three major types of 
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organochlorine insecticides and these are: dichlorodiphenylethanes, cyclodienes, chlorinated 
benzenes or cyclohexanes. The dichlorodiphenylethanes happen to be the oldest group of 
organochlorines and examples are DDT (dichlorodiphenyltrichloroethane), DDE 
(dichlorodiphenyldichloroethylene), methoxychlor(1,1,1-trichloro-2-2-bis-(4-methoxyphenyl) 
ethane, rthothane, dicofol and perthane. Examples of cyclodienes include aldrin, dieldrin, endrin, 
heptachlor, chlordane and endosulfan(6,7,8,9,10,10-hexachloro-1,5,-5a,6,9,9a-hexahydro-6,9-
methano-2,4,3-benzodioxathiepin-3-oxide). The chlorinated benzenes or cyclohexanes also 
include lindane, toxaphene, mirex, HCH and chlordecone.  
 
In general, many organochlorines and their metabolites have the tendency to bioaccumulate in 
the food chain due to their low water solubility and high chemical stability.  Amongst the 
organochlorine pesticides, DDT is the most common, harmful chemical and also persists in the 
environment. Swiss scientist Paul Muller discovered DDT in 1939 as an effective synthetic 
organic insecticide although it was synthesized before its discovery in 1939. For this momentous 
work, he received a noble prize in medicine. This is because DDT was found to be very useful in 
the control of malaria and yellow fever (Dunlap, 1981).  
The world health organisation estimates that malaria reduction programs, one component of 
which was the use of DDT saved the lives of more than five million people (Baird, 1997; 
Gladwell, 2001). The mode of action of DDT is not clearly established. However it is believed 
that DDT acts as neurotoxin which disrupts the delicate balance of sodium and potassium ions in 
nerve cells thereby preventing the normal transmission of nerve impulses in insects and in 
mammals (Robbins, 1991). Structural formulae of some organochlorine pesticides are shown 
below. 
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ClCl
Cl
ClCl
DDT                                              
ClCl
ClCl
DDE 
 
Cl Cl
Cl
Cl
Cl
Cl
Heptachloro                                                      
                                                                                        Hexachlorohexane (HCH)                                               
                                                                                 
                                       
              Endosulfan                                                                       Endrin 
 
 
 
Figure 2.2.1: Structural formulae of some organochlorine pesticides. 
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2.2.2 Organophosphate pesticides  
Organophosphate pesticides are derivatives of phosphoric acid. They include all insecticides 
containing phosphorus and are also known as organic phosphates, phosphorus insecticides and 
phosphoric acid esters.  They contain pentavalent phosphorus, carbon, hydrogen, oxygen and 
sulphur. Organophosphates were discovered in the early 1940s as a replacement for 
organochlorines for insect control. The largest use of organophosphates is in agriculture but also 
have much domestic uses (Smith, 1991).  
 
Organophosphates are less persistent or chemically unstable, lasting only a matter of days, 
months in the environment (Ware, 1983). It is this characteristic that brought them into 
agricultural use as substitute for persistent organochlorines. The organophosphates work by 
inhibiting certain important enzymes of the nervous system, namely cholinesterase. The enzyme 
is said to be phosphorylated when it becomes attached to the phosphorous moiety of the 
insecticide, a binding that is irreversible. This inhibition brings about the accumulation of 
acetylcholine at the neuron/muscle junctions or synapses resulting in rapid twitching of voluntary 
muscles and eventually paralysis (Robbins, 1991). 
 
In spite of the non-persistent nature of organophosphates, most are found to exhibit toxic effects 
in mammals. Exposure to these chemicals by swallowing, inhalation or absorption through the 
skin can lead to immediate health problems. There is evidence that organophosphates cause 
chronic as well as acute health problems especially in children (McKinney and Schoch, 2003). 
There are three main classes of organophosphates and these are type A, type B, type C as 
summarised below. 
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PO O
O
O
CH
3
CH
3
R
Type A
PO O
O
S
CH
3
CH
3
R
PS O
O
S
CH
3
CH
3
R
Type B
Type C
P O
O
O
CH
3
CH
3
OCHCl
2
C
PO O
O
O
CH
3
CH
2
NO
2
CH
3
PS O
O
S
CH
3
CH
3
R
Where  R=
CH
2
C
O
O
CH
3
R
2
Malathion
Parathion
dichlorvos
GeneralStructure
Specific example
 
 
Figure 2.2.3: The three main classes of organophosphates with examples 
 
Other specific examples of organophosphates are diazinon, chlorpyrifos, phosmet, fenitrothion, 
chlorvinphos, azinphos-methyl, profenophos, phorate, methamidophos, ethoprophos, pirimphos-
methyl, monocrotophos, mevinphos, acephate, oxydemetonmethyl, isofenphos, sulprofos, 
famphur and dimethoate (Metcalf, 1980).  
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2.2.3 Carbamate pesticides  
The carbamates are insecticides which are derivatives of carbamic acid H2NCOOH. An alkyl 
group usually a methyl replaces one of the hydrogen atoms attached to the nitrogen whereas a 
longer and more complex organic group replaces the hydrogen atom attached to the oxygen. 
In 1956, the first successful carbamate, carbaryl was introduced (Metcalf, 1980). Generally, 
carbamates have a short-life in the environment and behave just like organophosphates in its 
mode of action and persistency. The only difference in the mode of action is that the inhibition 
by carbamates is reversible and when the cholinesterase is inhibited by a carbamate it is said to 
be carbamylated (Robbins, 1991). 
 
Carbamates react with water and decompose to simple, nontoxic products and are preferred to 
the organochlorines. However, just like organophosphates, carbamates are a particular problem 
in developing countries where ignorance about their hazards and failure to use protective 
clothing has led to sickness and many deaths among agricultural workers (Baird and Cann, 
2004). Other examples of carbamate insecticides in addition to carbaryl are methomyl, 
carbofuran, aldicarb, oxamyl, thiodicarb, methiocarb, propoxur, bendiocarb, carbosulfan, 
aldoxycarb, promecarb and fenoxycarb (Metcalf, 1980). Structures of some carbamates are 
shown below. 
 
 
 
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O
O
NH
Carbaryl      
O
CH
3
CH
3
O
NH
O
CH
3
Carbofuran
N
H
H
O
O
N
CH
3
CH
3
S
CH
3
Aldicarb
 
 
Figure 2.2.4: Structural formulae of some carbamate pesticides. 
 
2.2.4 Synthetic pyrethroids pesticides  
Synthetic pyrethroids insecticides are man-made insecticides which have a similar chemical 
structure to natural pyrethrins found in chrysanthemums. They are commonly referred to as 
pyrethroids, very stable in sunlight and are effective against most agricultural insect pests when 
used at very low rates (Metcalf, 1980). Pyrethroids have gained considerable popularity since its 
discovery in the 1970s because of its low toxicity and as a result its usage has increased 
satisfactorily (Baird and Cann, 2004). 
 
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The mode of action of the pyrethroids is similar to that of DDT. They work by keeping the 
sodium channels open in neuronal membranes. Examples of Synthetic pyrethroids include 
permethrin, bifenthrin, cypermethrin, deltamethrin, fenpropathrin, allethrin, lambda- cyhalothrin, 
cyfluthrin, fenvalerate and prallethrin (Metcalf, 1980). Structural examples of some synthetic 
pyrethroids are shown below. 
 
 
 
 
                 Cypermethrin 
 
 
 
Cl
Cl
O
O
O
F
CN
Cyfluthrin 
 
 
 
 
Figure 2.2.5: Structural formulae of some synthetic pyrethroids pesticides. 
Cl
Cl
CH
3
CH
3
O
O
O
Permethrin
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2.3.0 Pesticide metabolites 
Metabolites are the products obtained after the original, parent chemical has undergone 
degradation. This can cause reduction in the concentration of the specific pesticide due to their 
breakdown to metabolites. The term degradation does not necessarily imply a less potent 
chemical as metabolites sometimes have an equal or greater toxicity the parent compound (Van 
Loon and Duffy, 2000). Degradation of pesticides to their metabolites can be caused by chemical 
reactions in the soil (chemical breakdown), sunlight (photo-degradation) or by microorganisms 
(microbial breakdown), 
 
Certain degradation reactions produce species with lower toxicity. DDT for instance degrades 
very slowly in water and soil by dechlorination (removal of chlorine) reactions to a less toxic 
compound, DDD under reducing conditions. The removal of the chlorine atoms from 
organochlorine molecules always has a detoxifying effect on these chemicals (Van Loon and 
Duffy, 2000). The equation for the conversion of DDT (dichlorodiphenyltrichloroethane) to 
DDD (dichlorodiphenyldichloroethane) through microbial breakdown is shown below. 
 
 
C
CCl3
H
ClCl
Dechlorination
C
CHCl2
H
ClCl
DDT DDD 
 
 
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Whereas most organochlorines degrade to produce less toxic compounds, degradation products 
of some organophosphosphate exhibit high toxicity. For instance organophosphate compound 
like parathion is properly called phosphorothioate because of the presence of the P=S group. 
Inside cells, oxygenating enzymes convert this group to P=O as shown below. 
 
P
S
O
O
CH3
CH3
O
NO2
Paraoxon
P
O
O
O
CH3
CH3
O
NO2
Parathion
 
 
 
The phosphorus atom in the oxygenated product, paraoxon, then reacts with the 
acetylcholinesterase (AcE) forming a stable complex that inhibits the ability of AcE to catalyse 
acetylcholine hydrolysis during transmission of nerve impulses. This interference with the 
neurotransmission accounts for the activity of paraoxon as pesticide; which is also a serious 
potential health hazard to other organisms including humans (Bempah, 2008)  
Both paraoxon and parathion are subject to degradation via hydrolysis reactions, in which water 
acts as a nucleophile. These reactions are catalyzed in organisms by various phosphatase 
enzymes. However, the presence of sulfur (S) attached to phosphorus (P) in parathion  
P
O
O
O
CH
3
CH
3
O
NO
2
H
2
O
Phosphatase enzyme
P
O
O
O
CH
3
CH
3
O H
H
O
NO
2
+
Paraoxon
 
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instead of the oxygen (O) in the paraoxon reduces the tendency for reaction with the nucleophile 
and therefore the S analogue is less toxic. Consequently it is of environmental concern when the 
more toxic oxygen-containing forms of these organophophorus compounds are produced by 
oxidation outside the target organism (Bempah, 2008). Two breakdown products of the herbicide 
atrazine are 2-chloro-4-ethylamino-6-amino-s-triazine and 2-chloro-4-amino-6-isopropylamino-
s-triazine commonly referred to as deisopropylatrazine (DIA) and deethylatrazine (DEA), 
respectively. These metabolites are typically found and used as a marker for interaction between 
surface and ground water (Bempah 2008).While these metabolites are phytotoxic and somewhat 
equally potent, 2-[(2,6-diethylphenyl)(methoxymethyl) amino]-2-oxoethanesulfonic acid, the 
ethane sulfonic acid (ESA) metabolite of alachlor, possesses greater stability than the parent 
compound but retains no herbicidal activity (Bempah, 2008). 
Generally pesticides metabolites are more stable and have a greater degree of polarity than the 
parent chemical. The breakdown products (metabolites) usually have a lower molecular mass 
than the parent compound and are more completely oxidized. These differences make them the 
metabolites more water soluble thereby increasing mobility and likelihood of transport (Barret, 
1996). 
 
2.3.1 Trends in pesticide use in Ghana 
It is estimated that 87% of farmers in Ghana use pesticides in vegetable and fruit production 
(Dinham, 2003). From 1970 to 1990 for example, the use of insecticides alone increased rapidly 
from 270,000 litres to 1,900000 litres, an annual rate increase of 30% (Ntow, 2001, Botwe, 
2007). Before the early 1980s, annual pesticide product imports into Ghana were worth less than 
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US $ 5 million. However over the last two decades, imports have increased significantly 
reaching more than US $ 30 million in 1999 (Ntow, 2001; Botwe, 2007). 
 
The government of Ghana in an attempt to regulate the importation, registration, distribution, 
application and disposal of pesticides promulgated the Pesticide Control and Management Act 
(Act 528). Under this Act, it is a criminal offence to import, distribute, manufacture or sell 
unregistered pesticides. Lindane (gamma-HCH) and thiodan (endosulfan) are recommended only 
for particular crops and pests and therefore have restricted use. For instance lindane is registered 
for capsid control cocoa on plantations, on vegetable farms, and for the control of stem borers in 
maize. Endosulfan is popularly used in cotton growing areas, on vegetables farms, and on coffee 
plantations (Ntow, 2001). 
Herbicides are the predominant pesticide type used in vegetable production in Ghana probably 
due to the farmers’ perception of weed control. They reason as long as it is profitable, and no 
better alternatives are available, the spraying of pesticide is a good investment. More so, 
chemical control method is very effective, rapid in curative action, adaptable in most situations, 
flexible in meeting changing agronomic and ecological and economical conditions (Bempah, 
2008). The table below shows the summary of imported insecticides, fungicides, herbicides 
imported from 1995 up to 1999. 
 
 
 
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Table 2.0: Volume of pesticide products (tons) imported into Ghana from 2002-2006 
Pesticide 2002 2003 2004 2005 2006 Average Percent 
        
Insecticides  4,130 5,974 8,418 10,006 12,728 8,251 49 
Fungicides  1,079 1,249 2,402 2,205 3,195 2,026 12 
Herbicides  2,186 2,939 4,578 8,566 10,718 5,797 35 
Others 368 498 544 707 1,224 672 4 
Total  7763 10658 15942 21484 27886 16746 100 
Source: Godfred Darko, Dietary intake of organophosphate pesticide residues through vegetables 
 from Kumasi, Ghana, February 2009. p.3, http//tpsalliance.org 
 
 
2.3.2 Studies on pesticides in Ghana 
Various studies in Ghana and other parts of the world have focused much on the analysis of only 
organochlorine pesticides because of their persistence, lipophilicity, toxicity and 
bioaccumulation. Nevertheless, regular survey studies and monitoring programmes of the other 
different types of pesticides have been carried out (MAFF, 1989; Luke et al; 1988; Yamaguchi et 
al, 2003) .In a study encompassing 30 organized farms and 110 kraals distributed throughout the 
10 regions of Ghana, Awumbila and Bokuma (1994) found that 20 different pesticides were in 
use with lindane being the most widely distributed and used pesticides accounting for 35% of 
those applied on farms and 85% of those used as herbicides. Of the 20 pesticides, 45% were 
organophosphates, 30% were pyrethroids, 15% were carbamates and 10% were organochlorines, 
(Awumibila and Bokuma, 1994). 
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In 1997, Clarke et al studied the knowledge attitudes and practices of 123 farm workers on three 
irrigation project areas in the Afram plains regarding the safe handling and use of pesticides. 
They found moderate levels of knowledge of pesticides absorption routes and of potential 
symptoms following exposure. However, farm workers knowledge for personal protective 
measures was poor to moderate and their use of personal protective equipment was minimal 
primarily due to financial constraints. They concluded that, training of agriculture and health 
workers in safety precautions in safety precautions, recognition and management of pesticides 
poisoning was a matter of urgency. 
Aboagye et al (2002) analysed pesticide residue in exportable quality cocoa beans collected from 
selected cocoa growing districts in the middle belt of Ghana and two shipping ports at Tema and 
Takoradi. Analysis of the extract by gas liquid chromatography showed detectable amount of 
lindane residue but the level was about 10% of maximum residue level of 0.1 mg/kg permitted 
by Codex Alimentarious Commission. The results of the research indicated that Ghana’s 
exportable cocoa beans were of no immediate danger of being rejected by importing countries 
due to the presence of lindane pesticide residues. 
 
Amoah et al (2005) carried out a study on pesticide  residues levels in a total of 180 vegetable 
samples( lettuce, cabbage and spring onion) which were randomly collected under normal 
purchase conditions from 9 major markets and 12 specialized selling points in 3 major Ghanaian 
cities: Accra, Kumasi and Tamale. The samples were analyzed for pesticide residues on all three 
vegetables. Chlopyrifos (Dursban) was detected on 78% of the samples, lindane (Gamalin 20) on 
31% of the samples, endosulfan (thiodan) on 36% of the samples, lambdacyhalothrin (karate) on 
11% of samples and dichloro-diphenyl-trichloroethane on 33% of samples. Most of the residues 
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recorded exceeded the maximum residue limit for consumption. Ntow (2001) also reported 
residues of lindane and other organochlorine pesticides in different samples. A total of 208 
samples of water, sediment, tomato, other crops, farmer’s blood and milk of women in 
Akumadan area in Ashanti region of Ghana were analysed. The results of the water and 
sediments analysed showed significant levels of lindane and endosulfan. 
 
There have been few reports on pesticides residues and the dangers they pose. The farmer’s field 
survey carried out by Gerken et al 2001 in Ghana identified headache, general weakness and 
dizziness, body pains, nausea and vomiting, stomach ache and diarrhoea as acute poisoning 
symptoms through pesticides application. In March 1999, three children in Ghana died after 
consuming fruits containing high residue of carbamates (Gerken et al, 2001). In late October, 
1998 children aged between 3-4 years were served with milk contaminated with the 
organophosphate insecticide, parathion in peru. They began vomiting and convulsing within half 
an hour of eating contaminated breakfast. Twenty four children died and another twenty one 
were treated at hospital and discharged (Aboagye, 2002). 
2.4 Health impacts of pesticides  
The harmful effects of pesticide usage cannot be ignored despite its numerous benefits. 
Pesticides can cause injury to human health as well as the environment. Exposure to hazardous 
pesticides is associated with a wide range of adverse effects in humans. Pesticide residues in 
food can cause short term or acute effect such as dizziness, diarrhoea and death. They can also 
result in long term or chronic health effects which can occur months or years after exposure. 
Chronic health effects include cancer, tumours, brain and nervous system damage, birth defects, 
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infertility and other reproductive system deformities, body organ damage, mild cognitive 
dysfunction and damage to the immune system (Botwe, 2007). 
 
 
2.4.1 Toxicity to Humans 
Humans can be exposed to pesticides through many ways. Exposure to pesticides may be 
minimal or excessive. Excessive exposure normally occurs through ground application of 
insecticides in farm fields. In most developing countries, like Ghana and Egypt a very large 
number of workers, laborers, and spray workers are involved in spraying of agriculture fields a 
number of times each season.  In most cases, they are often not equipped with protective clothes 
or masks. In addition, many thousands including children working on farms are exposed to 
insecticide residues. Eventually, this may affect majority of them resulting in exposure to 
pesticide intoxication in many nations (Mansour, 2004).  
In the United States for instance, about 45,000 accidental poisonings occur annually leading to 
about 50 deaths per year. Many more are believed to die of cancer caused by pesticide exposure 
(Bempah, 2008), whereas in Egypt reports indicate, incidence of pesticide poisoning during the 
period 1966-1982 was 5913. Moreover in Egypt, the other exposed populations suffered from 
dermatitis, neuropsychiatries, topical eye changes, gastrointestinal, genitourinary manifestations, 
as well as hepatomegaly and ventilatory function changes were significantly manifested among 
exposed group. Sensory hypothesia and abnormal deep reflexes were also noticed among the 
workers (Mansour, 2004). 
 
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2.4.2  Pesticide accumulation in biological systems 
Many organochlorine compounds are found in the tissues of fish in concentrations that are orders 
of magnitude higher than those in the waters in which they swim. Hydrophobic (water-hating) 
substances like DDT are particularly liable to exhibit this phenomenon. There are several reasons 
for this bioaccumulation of chemicals in biological systems (Baird and Cann, 2005).  Some of 
the reasons include low water solubility, high lipophilicity and high chemical stability of the 
pesticides. 
 
2.4.3  Biomagnification 
Several aquatic organisms such as fish may accumulate organic chemicals from the food they eat 
and from their intake of particulates in water and sediments onto which the chemicals have been 
adsorbed. In many cases, the chemicals are not metabolized by the fish: the substance simply 
accumulates in the fatty tissue of the fish, where its concentration increases with time. For 
example, the concentration of DDT in trout from Lake Ontario increases almost linearly with the 
age of the fish (Bempah, 2008).  
The average concentration of many chemicals also increases dramatically as one proceeds up a 
food chain, which is a sequence of species, each one of which feeds on the one preceding it in 
the chain. Over a lifetime, a fish eats many times its weight in food from the lower levels of the 
food chain, but it retains rather than eliminates most organochlorine chemicals from these meals. 
A chemical whose concentration increases along a food chain is said to be biomagnified. In 
essence, the biomagnification results from a sequence of bioaccumulation steps that occur along 
the chain.  
 
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2.4.4  Toxicology 
Toxicity is the degree to which a substance can damage an organism. It also refers to the 
harmfulness of a substance to an organism such as organochlorine pesticides. Toxicity of a 
substance can be affected by a number of factors such as the pathway of administration (whether 
the toxin is applied to the skin, ingested, inhaled or injected), the time of exposure (Botwe, 
2007). 
Toxicological data concerning the harmfulness of a substance to an organism, such as 
Organochlorine pesticide or heavy metal, are gathered most easily by determining its acute 
toxicity, which is the rapid onset of symptoms including death at the extreme limit following the 
intake of a dose of the substance. For example, experiments show that it takes only a few tenths 
of 1 microgram of the most acutely toxic synthetic compound, the dioxin kills most rodents 
within a few hours after it is administered orally to them (Bairn and Cann 2005; Bempah, 2008). 
Although the acute toxicity of a substance is of interest when we are exposed accidently to pure 
chemicals, in environmental toxicology we are usually more concerned about chronic 
(continuous, long-term) exposures at relatively low individual doses of a toxic chemical that is 
present in the air we breathe, the water we drink, or the food we eat. Generally speaking, any 
effects whether cancer, birth defects, etc. of such continuing exposures are also long-lasting and 
therefore also classified as chronic. (Bairn and Cann 2005; Bempah, 2008). 
The same chemical may give rise to both acute and chronic effects in the same organism, 
although usually by different physiological mechanisms. For example, a symptom of acute 
toxicity in humans of exposure to many organochlorines is a skin irritation that leads to 
chloracne, a persistent, disfiguring, and painful analog to common acne, and there is the fear that 
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persistent exposure to much lower individual doses than those that produce skin disease could 
eventually lead to cancer (Bairn and Cann 2005; Bempah, 2008). 
 
2.4.5  Dose – Response Relationship  
The dose of the substance administered in toxicity tests is usually expressed as the mass of the 
chemical, usually in milligrams, per unit of the test animal’s body weight, usually expressed in 
kilograms, thus giving units of milligrams per kilogram. The division by body weight is 
necessary because the toxicity of a given amount of a substance usually decreases as the size of 
the individual increases. Normally the toxicity of a substance increases with increasing dose, 
although exceptions are known (Bairn and Cann 2005). 
Individuals differ significantly in their susceptibility to a given chemical: some respond to it even 
at very low doses whereas others require a much higher dose before they respond. For this reason 
scientists have created dose – response relationships for toxic substances, including 
environmental agents (Bairn and Cann 2005; Bempah, 2008). Usually, the response effect on the 
test animals that is used to construct dose – response curve is death. The dose that proves to be 
lethal to 50% of the population of the test animals is called the LD50 value of the substance; its 
determination from a dose – response curve. The smaller the value of LD50, the more potent (i.e., 
more toxic) the chemical, since less of it is required to affect the animal. A chemical much less 
toxic than that would have a sigmoidal curve shifted to the right of the one shown (Bairn and 
Cann 2005; Bempah, 2008).   
Many sources quote values for the LD50, the lethal oral dose, when the chemical has been 
administered orally to the test animals, as opposed to dermal or some other means of 
administration. For example, the LD50 value for DDT for rats is about 110 mg/kg. As mentioned 
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previously, the presumption is usually made that LD50 values are approximately transferable 
between species. In the case of DDT, for example, humans are known to have survived doses of 
about 10 mg/kg, so presumably the LD50 value for humans is greater than 10 mg/kg. However, 
we have no direct evidence that the 110 mg/kg value for rats is also valid for humans (Bairn and 
Cann 2005; Bempah, 2008) 
In the dose – response curves for some substances there exists a dose below which none of the 
animals are affected; this is called the threshold. The highest dose at which no effects are seen 
lies slightly below it and is called the no observable effects level (NOEL), although sometimes 
the two terms are used interchangeably (Bairn and Cann 2005; Bempah, 2008) 
2.5 Risk Assessment  
The health risk associated with a particular pesticide is a function of both exposure and toxicity. 
Toxicities associated with the different pesticides (especially organochlorines) may however 
differ significantly. To protect public health from pesticide residues, most countries have 
specified and enforced maximum residues levels (MRLs) allowed to remain in foods. The MRLs 
may differ for different countries due to differences in food consumption patterns and 
agricultural practices. In Ghana, there are no set maximum residues levels (MRLs) and therefore 
MRLs by international bodies such as the Codex Alimentarius Commission and acceptable daily 
intake (ADI) values established by the world health organization (WHO) are often used as bench 
marks. Generally risk = exposure x toxicity 
Therefore in performing a risk assessment, an attempt is made to estimate the exposure of the 
affected population first. For  example for chemicals whose mode of exposure is primarily 
through drinking water, regulatory agencies such as the U.S. EPA consider a hypothetical 
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average person who drinks about 2 litres of water daily and whose body weight averages 70 kg 
9154 Ib) through life. If the ADI (or RfD) is 0.0020 mg/kg/day, then for the 70 kg person, the 
mass of substance that can be consumed per day is 0.0020 X 70 = 0.14 mg/day. Thus the 
maximum allowable concentration of the chemical in water would be 0.12 mg/2L = 0.07 ppm. 
Of course, if there are other significant sources for the substance, they must be taken into account 
in determining the drinking water standard. Also, exposure to several chemicals of the same type 
(e.g, several organochlorines) might lead to additive effects, so the standard for each one should 
presumably be lowed to take this into consideration (Bairn and Cann,2005) 
 
2.6 Analytical methods for pesticide residue analysis 
Different analytical methods exist for the analysis of pesticide residues in fruits and vegetables 
and new analytical methods are being developed continually. The analytical methods used at a 
particular time depends on the pesticide residues of interest, the sample matrix, the time required 
for analysis, the expected concentrations of pesticide residues and the materials and equipments 
available to the experimenter (Botwe, 2007).  Basically, the process of pesticide residue analysis 
consists of the following steps: 
 Sampling 
 Extraction 
 Clean up on interfering materials / Extract Purification 
 Concentration of samples 
 Identification and quantification of pesticide residue. 
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2.6.1 Sampling 
A representative sample should be collected into appropriate containers. Containers such as glass 
bottles, Teflon and aluminium foils have been proven to be the most suitable materials to come 
into contact with the sample for pesticide residue analysis. Pesticides may be lost by degradation, 
adsorption to the wall of the container and sometimes by volatilization. This occurrence can be 
prevented or reduced by sealing samples in airtight containers and storing them in a deep freezer 
until analysis (Akerblom, 1995). 
 
2.6.2 Extraction 
Extraction is an important technique in the process of pesticide residue analysis and therefore 
when choosing an extraction method, one should take into consideration the chemical and 
physical properties of the analytes and the type of matrix in which they are present (Zwir-Ferenc, 
2004). In vegetables and fruits, pesticide residues are normally present in low concentrations and 
therefore residues need to be concentrated first before the analysis is carried out. This is achieved 
by partitioning the residues to appropriate organic solvents or different solvent combinations 
(Akerblom, 1995; Yeboah, 2001). Among the many techniques that exist for isolating pesticides 
and PCBs (polychlorinated biphenyls) from food samples, the most frequently used are: 
 Solvent extraction by shaking (LE) 
 Solvent extraction in a soxhlet apparatus 
 Ultra sonication extraction (USE) 
 Microwave-assisted extraction (MAE) 
 Focused microwave –assisted solvent extraction( FMASE) 
 Supercritical fluid extraction techniques(SFE) 
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 Accelerated solvent extraction (ASE) 
 Membrane extraction techniques 
 Solid-based extraction techniques 
 
2.6.2.1 Solvent extraction by shaking 
Solvent extraction aided by shaking is based on the partitioning of analytes between liquid and 
solid phases (in the case of classical liquid-liquid extraction (LLE), between two immiscible 
liquids), which occurs when analyte move from the sample matrix into the properly selected 
solvent (Bempah, 2008). This technique has so many disadvantages.  For instance it is laborious 
and time consuming, expensive and apt to form emulsion, it may require the evaporation of large 
volumes of solvent and the disposal of toxic and flammable chemicals. Moreover, a relatively 
large amount of matrix is required. Smaller sample size becomes important when dealing with 
real life problems, such as consumer complaints and alleged chemical contamination (Bayer and 
Biziuk, 2008). 
 
2.6.2.2 Solvent extraction by soxhlet apparatus  
Extraction in soxhlet apparatus is one of the new, less expensive techniques which has replaced 
the old process of liquid-liquid extraction. The sample is repeatedly brought closer to a fresh 
solvent with high temperature. One major advantage of this technique is that no filtration is 
required. However, the main disadvantages of this method are that it still requires large amount 
solvent and is time consuming. An improved version of soxhlet apparatus which allows for 
shortening of the extraction time even to one hour with a simultaneous reduction of solvent 
usage is soxtec apparatus. Extraction in soxtec is a two-step procedure, involving a boiling and 
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rinsing step which drastically reduces the total time of extraction. Soxtec extraction has been 
used in many applications to extract organochlorine pesticide residues from samples with high 
lipid content such as fish (Falandysz et al, 2004; Bempah 2008). 
 
2.6.2.3 Ultrasonication extraction (USE) 
Ultrasonication extraction is a common conventional technique which has been widely applied 
for the extraction of pesticides and PCBs from various environmental samples (Ahmed, 2003). 
The application of ultrasonication extraction is to enhance food washing. The prominent 
mechanism for this washing is mechanical and includes the abrasion of suspended food particles 
in solvent leading to the removal of contaminants and improved solvent leaching of 
contaminants from the interior of the particles. Like the technique mentioned above, this 
technique requires the application of a lot of solvents (Mason et al, 2004). 
 
2.6.2.4 Microwave-assisted extraction (MAE) 
Another extraction technique is the microwave assisted extraction. In this phenomenon, the 
microwave energy absorption is applied. The microwave energy causes molecular movement and 
liquid rotation with permanent dipole, leading to a very fast heating of the solvent and the 
sample. The microwave assisted extraction’s requires low temperature treatment, high extraction 
rate, automation and the possibility of simultaneously extracting different samples at the same 
time without interferences (Camel, 2000) 
Microwave extraction is becoming the choice for the extraction of a diverse array of solid 
matrices for organic analyte analysis by GC, GC-MS, HPLC, and other analytical techniques. 
Since it operates at a far higher temperature and pressure than traditional soxhlet and sonication 
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techniques, it can be applied to a broader range of samples. One of the biggest benefits is 
realized in the reduced amount of time the extraction takes for multiple samples in a single 
extraction operation. With microwave extraction, samples are enclosed in high quality Teflon 
vessels together with solvent and heated to a controlled temperature with microwave power. 
With the flexibility of vessel options, choices of sample size, temperature/pressure, amounts of 
solvent, and number of samples make this an attractive technique for high-throughput sample 
preparation as well as the ability to process more difficult samples. This technology can also be 
applied to open-vessel applications depending on the matrix and substrate analyzed. One of the 
major benefits with this approach is moving to solvent-free applications (Camel, 2000; Bempah, 
2008). 
 
2.6.2.5 Focused microwave –assisted solvent extraction ( FMASE) 
The use of focused microwave –assisted soxhlet extraction (FMASE) has proved to be an 
alternative to soxhlet extraction. This process requires small amount of solvents and hence 
minimizes environmental pollution. (Luque-Garcia and Luque de Castro, 2004). Focused 
microwave –assisted solvent extraction has been used in many applications to extract pesticide 
residues from samples with high fat content and sunflower seeds (Prados-Rosales et al, 2003). 
 
2.6.2.6 Supercritical fluid extraction techniques (SFE) 
Extraction is a diffusion-based process, with the solvent required to diffuse into the matrix, and 
the extracted material to diffuse out of the matrix into the solvent. Diffusivities are much faster 
in supercritical fluids than in liquids, and therefore extraction can occur faster. Also, surface 
tension and viscosities are much lower than in liquids, so the solvent can penetrate into small 
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pores within the matrix inaccessible to liquids. Both the higher diffusivity and lower viscosity 
significantly increase the speed of the extraction: An extraction using an organic liquid may take 
several hours, whereas supercritical fluid extraction can be completed in 10 to 60 minutes 
(Skoog, 2007). The requirement for high pressures would increase the cost compared to 
conventional liquid extraction, therefore SFE may be used where there are significant 
advantages. Carbon dioxide itself is non-polar, and has somewhat limited dissolving power, 
hence it cannot be always used as a solvent on its own, particularly for polar solutes. The use of 
modifiers increases the range of materials which can be extracted. Food grade modifiers such as 
ethanol are often used, and can also help in the collection of the extracted material, but this 
reduces some of the benefits of using a solvent which is gaseous at room temperature (Bempah, 
2008). 
 
2.6.2.7 Accelerated solvent extraction (ASE) 
Accelerated solvent extraction is one the newly developed extraction techniques. This method 
utilizes solvents that are raised to near supercritical region, where they display better extraction 
properties. The rate of extraction increases at high temperatures because the viscosity and the 
surface tension decreases while its solubility and diffusion rate into the sample increase. As a 
result, pressure keeps the solvent below its boiling point and forces its penetration into the pores 
of the sample (Mendiola et al, 2007). The use of both high temperatures and pressures provides a 
relatively faster extraction process. Additionally, smaller amounts of solvents are required. In 
accelerated solvent extraction, the time required for extraction is independent on the mass of the 
sample and the efficiency of extraction is mainly dependent on temperature. The main 
advantages of accelerated solvent extraction are reduction in solvent consumption and extraction 
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time. However the major disadvantage with this method is that it is very expensive (Mendiola et 
al, 2007). 
 
2.6.2.8 Membrane extraction techniques 
Membrane extraction technique is one of the most recently developed methods of extraction of 
pesticides. The selective nature of membranes has made them a unique alternative to solvent 
extraction for sample clean up (Cordero et al, 2000; Jonsson et al, 2000, Bempah, 2008). This 
technique allows the preparation of samples that have a complex matrix by means of simple and 
easily automated equipments (Jakubowska et al, 2005). Also, membrane extraction technique 
can be coupled with the chromatographic system with significant advantages such as direct 
introduction of untreated samples, analyte pre-concentration and elimination of interferences. 
Additionally, there is also the possibility of recirculating the sample through the membrane cell, 
thereby allowing the extraction procedure to be applied even in cases where only limited 
amounts of sample are available (Carabias-Martinez et al, 2000). 
 
2.6.2.8 Solid-based extraction techniques 
Another way of extracting analyte is using a solid adsorbent material. A sorbent with strong 
affinity towards some target analytes will retain and concentrate those compounds from the 
sample solution. Widely applied to many matrices, including food, solid – phase – based 
extraction techniques are matrix solid – phase dispersion (MSPD), solid – phase extraction 
(SPE), solid-phase micro-extraction (SPME) and stir-bar sorptive extraction (SBSE). Current 
trends in these techniques for pesticides determination in food and the environment are presented 
in an up-to-date review (Bempah, 2008). 
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2.6.3 Clean-up of sample extract 
During the process of extraction, some constituents of the sample (fruit / vegetable) other than 
the target analytes can also be extracted into the solvent and interfere with the analysis and this is 
known as matrix-effect (Plimmer, 1995). These co-extractives have the effect of obscuring peaks 
in the chromatogram, damaging analytical columns and sensitive detectors used in the residue 
analysis. Co-extracted compounds often require tedious clean-up process for their removal to 
avoid matrix effect and ensure more consistent detector response and better baseline from 
instrument (Bacci et al, 1988; Botwe, 2007). When undertaking a clean- up process for an 
extract, care must be taken to ensure that target pesticides are not lost. 
 
Different methods have been developed to separate pesticides from co-extractives, and many are 
applied to different group of pesticides. Column adsorption chromatography and gel permeation 
chromatography techniques are two common techniques that have been widely used for clean up 
(Miglioranza et al, 1997). In column adsorption chromatography, the extract is applied to a 
column packed with a solid material such as florisil, alumina or silica gel for the components to 
be adsorbed (Jiang et al, 2005). The adsorption is followed by elution of the components of 
interest with solvents or solvent mixtures with increasing polarity. Separation of components is 
achieved based on difference in polarity of the components. As are result, polar compounds are 
eluted with polar solvents while non-polar are eluted with non-polar solvents (Hess et al, 1995). 
 
Adsorbent materials with relatively close particle size distribution packed in disposable 
polypropylene cartridges-solid phase extraction columns have also been used during clean up. 
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When analysing the techniques for determining pesticides and PCBs in food, a single, universal 
procedure, applicable to all types of samples does not exist. Because a combination of different 
techniques is often required, the aim of any analytical procedure should be achieved in as few 
steps as possible (Focant et al, 2001). The table below shows a summary of sample extraction 
and clean up procedures.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 2.1: Methods of sample extraction and clean-up (Zwir-Ferenc et al, 2004).  
Technique  Extraction  Clean-up          Characteristics 
LLE + + Foods, liquids, crops, plant material. 
High consumption of organic solvents, risk of 
emulsion creation, universal 
 
SPE   
Catridge  
Membrane extraction disc 
GCB 
 
+ - Foods, liquids, crops, plant material 
No emulsion, low consumption of organic solvents, 
automated, universal. 
SPME + - Foods, liquids, crops. 
No organic solvents  automated, universal 
 
 
MSPDE + + Plant material, food, liquids feed 
No emulsions, direct on-line clean up, universal. 
 
 
SFE + + Cereals, plant materials. 
Use ecologically nontoxic fluid (CO2). 
Optimization of modifier, automated, expensive 
instrumentation, small extractions. 
 
 
ASE + - Foods, crops, plant material. 
Low use of solvents, automated, expensive 
instrumentation. 
 
 
Colum AC 
Florisil column 
Alumina column 
Silica gel column 
 
 
+ 
+ 
+ 
 
 
- 
- 
- 
Foods, crops, plant material, fatty foods 
 
 
 
 
 
PGC column + - Samples with high content of fat, oil 
Automated, economical, universal. 
 
 
Soxhlet extraction  + - Foods, crops, plant material fatty foods 
Time consuming, high consumption of organic 
solvents. 
+, Main application;  -, secondary application Abbreviation : LLE, liquid-liquid extraction; SPE, solid-phase 
extraction; SPME, solid-phase micro extraction ; MSPDE, matrix solid-phase dispersion extraction; SPE, 
supercritical fluid extraction; ASE, accelerated solvent extraction; MAE, microwave-assisted extraction; column 
AC, ;PGC, porous graphitic carbon. 
 
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2.6.4 Identification and quantification of Pesticide Residue 
2.6.4 .1 Chromatography methods 
Currently, gas chromatography has proved to most versatile and easiet method for pesticide 
residue analysis due to its high sensitivity. The replacement of glass or metal by columns of 
Teflon was suggested because of the fact that a metallic column can decompose the analyte. 
Detectors such as electron capture (ECD), nitrogen-phosphorous (NDP), flame photometric 
(FPD) and Mass spectrometer are normally used. Mass spectrometry (MS) is currently the often 
used detection technique; this is due to its ability to provide information on the compounds 
molecular structure. It is also highly sensitive when used in the single ion monitoring mode. GC-
MS is the most accepted confirmatory technique (Torres et al, 1996). 
 
Nitrogen Phosphorous Detectors or GC-NPD, otherwise known as Thermionic Specific Detector 
or TSD, is a technique used to analyse nitrogen or phosphorous containing organic compounds. 
It is commonly used for pesticides, pharmaceuticals, food and environmental determinations due 
to its selectivity for phosphorous and nitrogen. Similar to a Flame Ionization Detector, a NPD 
uses a Hydrogen/Air flame through which the sample is passed. However a NPD uses a rubidium 
or cesium chloride alkali bead which is heated by a coil, over which the carrier gas mixed with 
Hydrogen passes (Torres et al, 1996).  
 
The hot bead emits electrons by thermionic emissions which are collected at the anode and 
provides the background current. When a component containing nitrogen or phosphorous exits 
the column, the partially combusted nitrogen and phosphorous materials are adsorbed on the 
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surface of the bead. This then increases the emission of electrons and the current which is then 
measured. 
 
Electron Capture Detectors (ECDs) are often used in pesticide residue determination. It has a 
very high sensitivity to polychlorinated hydrocarbons and other halogenated pesticides.). When 
electronegative compounds enter the ECD cell from the column, they immediately combine with 
some of the free electrons, temporarily reducing the number remaining in the electron cloud. 
When the electron population is decreased, the pulse rate is increased to maintain a constant 
current equal to the standing current. The pulse rate is converted to an analog output, which is 
acquired by the Peak Simple data system. Unlike other detectors which measure an increase in 
signal response, the ECD detector electronics measure the pulse rate needed to maintain the 
standing current (Bempah, 2008). It’s disadvantaged to selectivity because all kinds of electron 
attracting functional groups such as nitro groups and aromatic structures also give response. 
(Torres et al, 1996) 
 
Gas Chromatography – Flame Photometric Detector or GC-FPD is a technique used to analyse 
sulphur or phosphorous containing compounds and metals such as tin, boron, arsenic and 
chromium. An FPD uses a Hydrogen/Air flame into which the sample is passed. Phosphorous 
and sulphur containing hydrocarbons generate chemiluminescene at specific wavelengths which 
when passed into a photo-multiplier gives an electrical signal which can then be measured. 
(Torres et al, 1996). 
 
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High Performance Liquid Chromatography - High performance liquid chromatography is 
basically a highly improved form of column chromatography. Instead of a solvent being allowed 
to drip through a column under gravity, it is forced through under high pressures of up to 400 
atmospheres. That makes it much faster and also allows you to use a very much smaller particle 
size for the column packing material which gives a much greater surface area for interactions 
between the stationary phase and the molecules flowing past it. This allows a much better 
separation of the components of the mixture.  
 
 
 
 
                                                      
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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CHAPTER THREE 
3.0 METHODOLOGY 
3.1 Study Area 
The study was undertaken in three regions of Ghana namely Greater Accra, Eastern and Central 
Regions. These  regions are linked together in the southern part of Ghana where there is 
abundant of rainfall and good climatic conditions necessary for crop production especially fruits 
and vegetables. As a result, the use of pesticides is a common practice as well as probable use of 
restricted or banned pesticides which get into the country through unapproved routes. There may 
also be deposition of pesticide residues especially organochlorine pesticides at the study area 
(markets) as a result of long range air transport from their application sites. These factors are the 
reasons for the selection of those areas for the study. 
In each region, four large urban markets were targeted. These include the regional capitals and 
other towns where these fruits and vegetables are mostly cultivated and sold since majority of the 
populace obtains their fresh vegetables and fruits from such markets. 
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       Figure 3.1: Map showing the study areas  
 
 
 
 
MAP SHOWING STUDY AREAS
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3.1.2 Sampling and storage 
A total of 192 samples of fruits and vegetables were purchased from major market centers in 
three regions of Ghana within the months of January and February. The fruits and vegetables 
sampled were lettuce, garden eggs, mango and pineapple. In Greater Accra, samples were 
purchased from Mallam Atta, Agbobloshie, Kaneshie and Madina markets. For Central Region, 
samples were obtained from Cape Coast, Kasoa, Mankesim and Agona Swedru markets. In 
Eastern region, samples were purchased from Koforidua, Nsawam, Somanya and Asamankese 
markets. In every market, fresh samples were purchased from different sellers in order to have a 
true representation. After collection, the samples were sealed in polyethylene bags, labeled 
appropriately and transported to the laboratory and kept in a refrigerator for further analysis. 
 
3.1.3 Reagents 
Pesticide grade ethyl acetate, analytical grade acetone were supplied by Labscan 
(Dublin,Ireland), sodium hydrogen carbonate and sodium sulfate were purchased from E.Merck 
(Germany). Disposable solid-phase florisil cartridges (500mg/8mL) were obtained from Sigma-
Aldrich Chemicals USA. Pesticide reference standards were obtained from Dr, Ehrenstofer 
GmbHm (Germany) and stored in the freezer to minimize degradation. 
 
3.1.4 Apparatus 
The following lists of apparatus were used for laboratory analysis:Gas chromatograph (GC): 
Helwet Packard 5890 series ii with electron capture detector nickel source Column: 30m 
capillary column,0.53mm ID, fused silica coated with DB-5, Integrator: Helwet Packard 3396, 
Homogenizer-Foss 2096 based on tecator technology, Weighing balance-Metler Toledo PG 
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1003-5, Macerator- Ultra-turax macerator, type t- 25 generator, Centrifuge-CRI multifunction 
Thermo Electron Industries SAS (France), Rotary vacuum evaporator-Buchi RE-200 (Buchi 
Labortechnic AG, Postfach, Switzerland), graduated pipettes, Round bottom flasks (250ml and 
100ml), aluminum foils, oven, auto sampler vials (2ml) ,chromatographic columns. 
 
3.1.5 Cleaning of glass wares 
Glass wares were soaked in soapy water for two days after which they were thoroughly washed 
with detergent. After washing, the glass wares were rinsed six times with tap water followed by 
deionized water and then dried in an oven at 100 oC for about one hour. The glass wares were 
then removed from the oven and allowed to cool down ready to be used. 
 
3.1.6 Preparation of pesticide (organochlorine) mixture standard solution 
0.1mL  each of o,p’ DDE, endrin, p,p’ DDT, heptachlor, chlordane, alpha -endosulfan, beta- 
endosulfan, methoxychlor, HCH, and aldrin were accurately pippeted into a 50ml volumetric 
flask and 48.4ml of ethyl acetate was added to give organochlorine mix. Standard solution with 
concentration 2.0µg/ml was made for the calibration curve. 
 
3.1.7 Extraction 
The extraction procedure was according to methods described by Netherlands analytical methods 
of pesticide residues and foodstuffs (Ministry of Public Health, Welfare and Sports, Netherlands, 
2007). Frozen vegetables and fruits were allowed to thaw to room temperature, shredded and 
homogenized. Approximately 20 g of the homogenized sample was macerated with 40ml of 
ethyl acetate. 5 g of sodium hydrogen carbonate and 20 g of anhydrous sodium sulfate were 
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added to remove moisture present and macerated for 3 minutes till a consistent mixture was 
attained using the ultra-turax macerator. The samples were centrifuged for 5 minutes at 3000 rpm 
to separate the two phases. The solvent was filtered through a No. 1 filter paper into 250 ml 
conical flask. After this the residue was taken through the same process two more times and 
added to the original filtrate. A drop of isodrin was added to the combined filtrate and evaporated 
to dryness on a vacuum rotary evaporator. 
 
3.1.8 Solid-phase extraction (SPE) clean-up of extract 
About 3 g of activated silica was weighed and poured into a glass column which has been 
plugged with a glass wool at the end followed by 2 g of anhydrous sodium sulfate. The silica 
packed column was clamped using a retort stand after which it was conditioned with 10ml ethyl 
acetate. A receiving flask was placed under the column to collect the eluate. The sample was 
then transferred onto the silica column and eluted   two times first with 10 ml of ethyl acetate and 
again with 5 ml of ethyl acetate using Pasteur pipette. The eluate was collected into a round 
bottomed flask and evaporated to dryness using a rotary evaporator fitted to a vacuum pump. The 
residue was dissolved with 2 ml of ethyl acetate using Pasteur pipette into glass vials for Gas 
Chromatographic analysis. 
 
3.1.9  Calibration curve 
 Calibration curve was prepared from the stock solutions containing the individual pesticide 
standards to check for the linearity of the system. Ethyl acetate (9975 µl) was added to 25 µl of 
pesticide standards solution (2 µg/ml). Serial dilutions of concentrations of 0.20 µg/ml, 0.02 
µg/ml, 0.01 µg/ml and 0.005 µg/ml were prepared. 1.0 µl of each concentration was injected into 
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the injection port of the GC-ECD and the responses were recorded. A calibration curve was 
constructed by plotting the concentration against their respective peak areas. 
3.2 Gas Chromatographic Analysis 
A Varian CP-3800 Gas Chromatograph (Varian Associates Inc. USA) equipped with 63Ni 
electron capture detector was used for the analysis. A volume of about 1 µL of the extract was 
injected and the separation was performed on a fused silica gel capillary column coated with VF-
5ms, 40m long with internal diameter and film thickness of 0.25 mm and 0.25 µm respectively. 
The carrier gas and make up gas were nitrogen at a flow rate of 1.0 and 29 ml/min respectively. 
The injector and detector temperatures were 270 oC and 300 oC respectively. The column oven 
temperature was programmed as follows: 80oC for 1min to 18oC at 25 oC/min and up to 300 oC 
at 5 oC/min held for 1min. 
  
3.2.1 Quantification of pesticides results 
An external standard method was used for determining the quantities of residues in the sample 
extracts. A standard mixture containing known amounts of pesticides was run and the response 
of the detector for each compound was determined. The area of the corresponding peak in the 
sample was compared with that of the known standard. 
 
3.2.2 Quality control and quality assurance 
Quality control and quality assurance were incorporated into the analytical scheme. Samples 
were carefully handled carefully to avoid contamination. Analytical grade reagents were used in 
the sample preparations and treatments and deionized water was used throughout the study. 
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3.2.3 Recovery Test 
Loss of target compounds could occur during sample preparation, extraction and analysis. The 
extent of analyte losses especially during extraction was assessed by performing a recovery test. 
This was done by spiking the samples with 0.5ppm of an internal standard (isodrin) before 
extraction to evaluate the recovery of the compounds. The recovery was determined using the 
formula: 
% Recovery= Pesticide (ppm) recovered from fortified sample   x 100 
                       Amount of pesticide (ppm) added 
 
 
 
3.2.4 Limit of detection (LOD) 
The extracts of the fortified samples were serially diluted by a factor of two to give different 
concentrations. 1.0µL of each concentration was injected and the least concentration that gave 
response was noted. The limit of detection was calculated by the formula: 
LOD=    V1 (µl)    X Concentration fortified 
               V2 (µl) 
 
Where V1=volume injected        and       V2=final volume of fortified extract 
 
3.2.5 Data analysis 
Statistical analysis incorporated in the work include mean of samples and corresponding standard 
deviations. Ranges were compiled from minimum and maximum values for levels of pesticides 
residues detected in the study. Data was subjected to one-way analysis of variance to determine 
the differences in pesticide residue among the samples as well as the different areas from which 
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they were sampled. All tests were regarded as statistically significant when p<0.05. All these 
calculations were done using Microsoft excel 2007.  
 
 
 
 
 
 
                                                  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  CHAPTER FOUR 
4.0 RESULTS AND DISCUSSION 
4.1:  Introduction  
The concentrations of organophosphates, synthetic pyrethroids and organochlorine pesticide 
residues were measured in four different samples namely, lettuce, garden eggs, pineapple and 
mango from the selected regions in Ghana. Analysis of the samples revealed varying 
concentrations of pesticide residues. Tables 4:12- 4.19 show the results of the various pesticide 
residues detected in samples from the different sampling areas.  
Data was subjected to one-way analysis of variance (one-way ANOVA) to determine whether 
the pesticides concentrations vary among the samples (lettuce. garden eggs, pineapple and 
mango) as well as the different areas (the three regions) from which they were sampled. All tests 
were regarded as statistically significant when p<0.05. These are summarized in Appendices A-
D. Again, the results of the pesticide residues were compared with the WHO/FAO codex 
Alimentarious Commission Maximum Residues Levels (MRLs) for fruits and vegetables. Health 
risk estimation was computed for each organochlorine pesticide and is presented in tables 4.21-
4.24 and the results discussed. 
 
4.1.1: Percentage of samples of fruits and vegetables with pesticide residues. 
The percentage of samples of fruits and vegetables with pesticide residues are presented in the 
table 4.11. In all, a total of 192 fresh samples of fresh fruits and vegetables were purchased from 
major market centers in the three regions of Ghana within the months of January and February 
2013. The percentage of samples of fruits and vegetables with pesticide residues in Lettuce, 
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Garden eggs, Pineapple and Mango were 52%, 40%, 45%, 48% respectively and details are 
discussed below. 
 
Table 4.11: Percentage of samples with one or more pesticide residues.  
Vegetable/fruit Scientific name Number  of 
samples 
% with one or 
more residues 
Lettuce 
 
Lactuca sativa    48   52 
Garden eggs Solanum melongena    48   40 
 
Pineapple  Ananas comosus    48   45 
 
Mango Magnifera indica    48   48 
Total                                                                      192 
 
 
 
 
 
 
Fig 4.11: Graph showing the percentage of samples with one or 
 more pesticide residues  
0
10
20
30
40
50
60
Lettuce Garden eggs Pineapple Mango
%
 w
it
h
 p
es
ti
ci
d
e 
re
si
d
u
es
 
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4.1.2: Occurrence and distribution of organophosphates and synthetic pyrethroids in 
samples from the Greater Accra Region 
Table 4.12 and Figures 4.12a-4.12f show the levels of organophosphates and synthetic 
pyrethroids in samples from the Greater Accra Region. Total samples analyzed show the 
presence of sixteen different pesticides residues comprising nine organophosphates and seven 
synthetic pyrethroids being the region with the highest number of recorded synthetic pyrthroids 
pesticide residues. The different organophosphates pesticides detected were dimethoate, 
pirimiphos-methyl, malathion, fenitrothion, parathion ethyl, chlorfenvinphos, profenofos, 
methamidophos, and chlorpyrifos. Phorate and ethoprophos were not detected in any of the 
samples analyzed.  
Generally most organophosphates pesticides recorded high concentrations except profenofos and 
dimethoate with total mean concentrations of 0.02 mg/kg and 0.04 mg/kg respectively in all 
samples. The highest concentration of organophosphate in lettuce was recorded for malathion 
with mean concentration of 0.26 mg/kg while dimethoate, profenofos and chlorpyrifos recorded 
lowest mean concentrations of 0.02 mg/kg (Fig 4.12c). Again, the highest concentration of 
organophosphate in garden eggs was recorded for chlorpyrifos while the lowest was recorded for 
pirimiphos-methyl with mean concentrations of 0.45 mg/kg and 0.01mg/kg respectively (Fig 
4.12d).  
In pineapple, the highest concentration of organophosphate was observed for parathion 
ethyl/malathion with mean concentration of 0.10 mg/kg while the lowest was recorded for 
chlorfenvinphos with mean concentrations of 0.02 mg/kg (Fig 4.12e). Mango showed the highest 
concentration of organophosphate for methamidophos with mean concentration of 0.78 mg/kg 
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while the lowest was recorded for chlorfenvinphos/parathion-ethyl/profenofos/ chlorpyrifos with 
mean concentration of 0.02 mg/kg (Fig 4.12f). Statistically, the concentration of 
organophosphates in the samples of lettuce, garden eggs, pineapple did not vary significantly 
(p>0.05 or p=0.525, appendix a) suggesting a common route of contamination. 
Also, the seven different synthetic pyrethroids pesticides detected were allethrin, lambda-
cyhalothrin, permethrin, cyfluthrin, deltamethrin, cypermethrin and bifenthrin. The  results show 
low levels of synthetic pyrethroids except for cypermethrin, cyfluthrin and bifenthrin with mean 
concentrations of 0.26 mg/kg, 0.07 mg/kg and 0.13 mg/kg respectively. The highest 
concentration of synthetic pyrethroids in lettuce was observed for lambda-cyhalothrin with mean 
concentration of 0.18 mg/kg while the lowest concentration was observed for permethrin with 
mean concentration of 0.02 mg/kg (Fig4.12c). The highest concentration of synthetic pyrethroids 
in garden eggs was recorded for cypermethrin with mean concentration of 0.36 mg/kg while the 
lowest concentration was observed for lambda-cyhalothrin/ cyfluthrin, with each recording a 
mean concentration of 0.03 mg/kg (Fig 4.12d).  
The highest concentration of synthetic pyrethroid found in pineapple and mango was 
cypermethrin with mean concentrations of 0.21 mg/kg and 0.36 mg/kg in pineapple and mango 
respectively while the lowest concentration was recorded for cyfluthrin with mean 
concentrations of 0.15 mg/kg and 0.05 mg/kg for pineapple and mango respectively (Fig 4.12e 
and 4.12f). Statistically, the differences in concentrations of synthetic pyrethroids in the samples 
of lettuce, garden eggs, pineapple and mango varied significantly (p<0.05 or p= 0.0015, 
appendix a) suggesting different route of contamination. 
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54 
 
The high levels of organophosphates and synthetic pyrethroids in samples from Greater Accra 
Region suggest that farmers who supply vegetables and fruits to these markets centers do use 
organophosphates and synthetic pyrethroids in significant quantities. 
 
 
 
 
Table 4.12: Concentrations (mg/kg) of organophosphates and synthetic pyrethroids in 
samples from the Greater Accra Region 
 a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD =standard 
deviation,   
                                                                               
 
 
Pesticide 
 
Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Dimethoate 0.02 - 0-0.02 0.05 - 0-0.05 0.05 - 0-0.05 0.03 - 0-0.03 
Pirimiphos-m 0.09 - 0-0.09 0.01 - 0-0.01 0.05 - 0-0.02 0.56 - 0-0.56 
Malathion 0.26 - 0-0.26 0.13 - 0-0.13 0.1 0.07 0-0.17 0.12 - 0-0.56 
Fenitrothion 0.08 0.06 0-0.13 0.12 - 0-0.12 0.04 0.02 0-0.05 0.05 - 0-0.05 
Parathion ethyl 0.08 - - 0.07 0.05 0-0.12 0.10 0.05 0-0.14 0.02 - 0-0.02 
Chlorfenvinp 0.03 0.01 0-0.04 0.19 - 0-0.09 0.02 - 0-0.02 0.02 - 0-0.02 
Profenofos 0.02 0.02 - 0.02 - 0-0.02 0.03 - 0-0.03 0.02 - 0-0.02 
Methamidop 0.08 - - 0.03 0.01 0-0.04 0.06 - 0-0.02 0.78 - 0-0.78 
Chlorpyrifos 0.02 0.01 0-0.02 0.45 0.02 0.09-
1.36 
0.07 0.03 0-0.09 0.02 - 0-0.02 
Allethrin a   <0.01 - - 0.05 0.02 0-0.08 <0.01 - - ND - - 
Lambda-cyhal a 0.08 0.02 0-0.13 0.03 - 0-0.03 ND - - ND - - 
Permethrin a 0.02 - - 0.08 - 0-0.08 <0.01 - - ND - - 
Cyfluthrin a 0.04 0.04 0-0.06 0.03 - 0-0.03 0.15 - 0-0.15 0.05 0.03 0-0.03 
Deltamethrin a <0.01 - - 0.04 - 0-0.04 ND - - ND - - 
Cypermethrin a 0.04 0.04 0-0.04 0.41 0.22 0-0.63 0.21 - 0-0.21 0.36 - 0-0.02 
Bifenthrin a ND - - 0.13 - 0-0.13 ND - - ND - - 
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55 
 
 
    
   
Fig 4.12a: Mean concentration levels of                              Fig 4.12b: Mean concentration levels of  synthetic   
 organophosphates in fruits and vegetables from               pyrethroids in fruits and vegetables from the    
 the Greater Accra Region.                                                    the Greater Accra Region.  
 
 
  
 
Fig 4.12c: Mean concentration levels of                              Fig 4.12d: Mean concentration levels of     
 organophosphates  and synthetic pyrethroids in              organophosphates  and synthetic pyrethroids in  
 lettuce  from the Greater Accra Region.                            garden eggs from the Greater Accra Region.  
 
 
0
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Garden eggs
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56 
 
 
 
   
 
Fig 4.12e: Mean concentration levels of                             Fig 4.12f: Mean concentration levels of     
 organophosphates  and synthetic pyrethroids in              organophosphates  and synthetic pyrethroids in  
 pineapple from the Greater Accra Region.                        mango from the Greater Accra Region.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0
0.05
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0.15
0.2
0.25
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Mango
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57 
 
4.1.3: Occurrence and distribution of organophosphates and synthetic pyrethroids in 
samples from the Central Region 
The mean, standard deviation and the range of values obtained from the analysis done on all 
samples from the Central Region are shown in table 4.13. The results from the samples analyzed 
showed the presence of thirteen different pesticides residues comprising eight organophosphates 
and five synthetic pyrethroids being the region with the least number of recorded 
organophosphates pesticide residue. The organophosphates pesticides detected were dimethoate, 
fenitrothion, chlorfenvinphos, profenofos, methamidophos, ethoprophos and chlorpyrifos.  
In the Central Region, the highest concentration of organophosphate in lettuce was recorded for 
methamidophos with mean concentration of 0.05 mg/kg while the lowest concentration was 
recorded for fenitrothion with mean concentration of 0.02 mg/kg (Fig4.13c). Phorate and 
ethoprophos recorded concentrations below the detection limit. Again the highest concentration 
of organophosphate in garden eggs was observed for chlorpyrifos with mean concentration of 
0.17 mg/kg while the lowest concentration was obtained for both dimethoate and 
chlorfenvinphos with mean concentration of 0.01 mg/kg each (Fig4.13d). Fenitrothion and 
profenofos were not detected in any of the garden eggs samples analyzed.   
In pineapple, the highest concentration of organophosphate was obtained for methamidophos 
with mean concentrations of 0.11 mg/kg while the lowest concentration was obtained for 
dimethoate and chlorfenvinphos with concentrations of 0.01 mg/kg each (Fig4.13e). Fenitrothion 
and profenofos were not detected in any of the garden eggs samples while phorate and 
ethoprophos recorded concentration levels below the detection limit.  
The highest concentration of organophosphate in mango was observed for chlorpyrifos with 
mean concentration of 0.34 mg/kg while the lowest concentration was observed for 
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58 
 
phorate/profenofos at concentrations of 0.04 mg/kg each (Fig4.13f). Fenitrothion and 
ethoprophos were not detected in any of the pineapple samples analyzed while dimethoate 
concentrations were below the detection limit. Generally, most organophoshates recorded low 
concentrations levels except methamidophos and chlorpyrifos with mean concentrations of 0.08 
mg/kg and 0.15 mg/kg respectively in all samples. Parathion ethyl, malathion, pirimphos methyl 
were not detected in samples from the Central Region. The concentration of the 
organophosphates in the fruits and vegetables varied significantly (p < 0.05 or p=0.011, appendix 
b). 
Also, the five different synthetic pyrethroids pesticides detected were lambda-cyhalothrin, 
permethrin, cyfluthrin, deltamethrin and cypermethrin. The  results indicate low levels of 
synthetic pyrethroids except for cypermethrin, cyfluthrin and lambda-cyhalothrin with mean 
concentrations of 1.67 mg/kg, 0.13 mg/kg and 0.12 mg/kg respectively. The highest 
concentration of synthetic pyrethroids in lettuce, garden eggs, and pineapple mango was obtained 
for cypermethrin with mean concentrations of 1.34 mg/kg, 1.7 mg/kg, and 1.52 mg/kg and 2.11 
mg/kg respectively (Fig 4.13a - 4.13f). The lowest concentration of synthetic pyrethroids in 
lettuce and garden eggs was observed for allethrin with mean concentrations of 0.04 mg/kg and 
0/03 mg/kg respectively (Fig 4.13c and 4.13d). The lowest concentration of synthetic pyrethroids 
in pineapple and mango was observed for lambda-cyhalothrin with each recording mean 
concentrations of 0.01 mg/kg (Fig 4.13e and 4.13f). The difference in the concentration of 
synthetic pyrethroids in the samples of lettuce, garden eggs, pineapple and mango from the 
Central Region was not significant (statistically, p>0.05 or p= 0.991, appendix b). Deltamethrin 
was absent in both lettuce and garden eggs while allethrin was absent in both pineapple and 
mango. Cyfluthrin was not detected in any of the pineapple samples analyzed. The relatively low 
University of Ghana          http://ugspace.ug.edu.gh
59 
 
levels of organophosphates and high levels of synthetic pyrethroids especially cypermethrin in 
samples from the Central Region shows that farmers in this region use cypermethrin extensively. 
 
Table 4.13: Concentrations (mg/kg) of organophosphates and synthetic pyrethroids in 
samples from the Central Region 
a - Synthetic Pyrethroids , 
 
Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD =standard 
deviation,   
            
 
Pesticide 
 
Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Dimethoate 0.05 0.01 0-0.06 0.01 - 0-0.01 0.01 - - <0.01 - - 
Fenitrothion 0.02 - - ND - - ND - - ND - - 
Chlorfenvinphos 0.03 - - 0.01 - 0-0.01 0.01 - 0-0.01 0.05 0.03 0-0.08 
Profenofos 0.03 - 0-0.03 ND - - ND - - 0.04 - - 
Phorate <0.01 - - 0.02 - 0-0.12 <0.01 - - 0.04 0.02 0-0.06 
Methamidophos 0.05 0.01 0-0.07 0.09 0.02 0-0.11 0.11 - 0-0.11 0.06 - 0-0.06 
Ethoprophos <0.01 - - 0.02 - 0-0.02 <0.01 - - ND - - 
Chlorpyrifos 0.04 0.02 0-0.06 0.17 0.1 0-0.27 0.04 0.02 0-0.07 0.34 - - 
Allethrin a 0.04 0.01 0-0.06 0.03 0.02 0-0.04 ND - - ND - - 
Lambda-cyhal a 0.41 0.22 0-0.71 0.50 0.48 0-1.17 0.01 - 0-0.01 0.01 - 0-0.01 
Permethrin a 0.11 0.08 0.05-
0.25 
0.05 0.03 0.02-
0.09 
0.07 0.07 0-0.16 0.13 - 0-0.13 
Cyfluthrin a 0.29 0.08 0-0.41 0.08 0.01 0-0.08 ND - - 0.03 - 0-0.03 
Deltamethrin a  ND - - ND - - 0.10 - - 0.05 -
0.02 
0-0.06 
Cypermethrin a 1.34 0.32 1.34-
2.41 
1.70 0.43 1.34-
2.41 
1.52 0.30 1.19-
1.91 
2.11 0.90 1.41-
3.39 
University of Ghana          http://ugspace.ug.edu.gh
60 
 
  
 
Fig 4.13a: Mean concentration levels of                               Fig 4.13b: Mean concentration levels of  synthetic   
 organophosphates in fruits and vegetables from                pyrethroids in fruits and vegetables from the    
 the Central Region.                                                                Central Region.  
 
 
     
 
Fig 4.13c: Mean concentration levels of                              Fig 4.13d: Mean concentration levels of     
 organophosphates  and synthetic pyrethroids in               organophosphates  and synthetic pyrethroids in  
 lettuce from the Central Region.                                         garden eggs from the Central Region.  
 
0
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Pineapple Mango
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Pineapple Mango
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Garden eggs
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61 
 
 
 
 
  
 
Fig 4.13e: Mean concentration levels of                          Fig 4.13f: Mean concentration levels of     
 organophosphates  and synthetic pyrethroids in          organophosphates  and synthetic pyrethroids in  
 pineapple from the Central Region.                               mango from the Central Region.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0
0.2
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0.6
0.8
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1.4
1.6
D
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Mango
University of Ghana          http://ugspace.ug.edu.gh
62 
 
4.14: Occurrence and distribution of organophosphates and synthetic pyrethroids in 
samples from the Eastern Region 
The results obtained from the analysis of samples from the Eastern Region are shown in table 
4.14 and graphically represented in Fig4.14a-4.14f. Total samples analyzed show the presence of 
eleven organophosphates and five synthetic pyrethroids. This region recorded the highest number 
organophosphate pesticide residues. The different organophosphate pesticides detected were 
dimethoate, pirimiphos-methyl, malathion, fenitrothion, parathion ethyl, chlorfenvinphos, 
profenofos, methamidophos, chlorpyrifos, phorate and ethoprophos.  
The most predominant organophosphate pesticide in lettuce, garden eggs, pineapple and mango 
was chlorpyrifos with mean concentrations of 0.19 mg/kg 0.14 mg/kg 0.08 mg/kg 0.30 mg/kg 
(Fig4.14a-4.14f). The high levels of chlorpyrifos in most samples suggest that farmers in this 
region use a lot of chlorpyrifos as pesticides. These results confirm earlier findings by Ntow et al 
(2005) that a lot of farmers in Ghana use Dursban (chlorpyrifos) in vegetable production 
especially lettuce and cabbage. 
The least predominant organophosphate pesticides in lettuce was obtained for dimethoate, 
parathion ethyl, chlorfenvinphos and phorate all recording a mean concentration of 0.02 mg/kg 
(Fig 4.14c). Malathion was not detected in any of the lettuce samples analyzed. The lowest 
concentration of organophosphates pesticides in garden eggs was observed for ethoprophos with 
a mean concentration of 0.02 mg/kg (Fig 4.14d). Chlorfenvinphos was not detected in any of the 
garden egg samples analyzed while pirimiphos-methyl concentration was below the detection 
limit. 
Again the lowest concentration of organophosphate pesticides in pineapple was recorded for 
phorate and dimethoate with a mean concentration of 0.01 mg/kg (Fig 4.14e). Comparably, these 
University of Ghana          http://ugspace.ug.edu.gh
63 
 
values are not different from those detected in pineapple sampled from the Central Region 
suggesting similar route of contamination. Pirimiphos-methyl, Chlorfenvinphos and profenofos 
were not detected in any of the pineapple samples analyzed indicating that farmers in this region 
do not use these pesticides in pineapple production or could be to the fact that farmers are 
seriously following extension officer’s guidelines as regards pesticide application. In mango, the 
lowest concentration of organophosphates pesticides was recorded for phorate with a mean 
concentration of 0.01 mg/kg (Fig 4.14e). Generally most organophosphates pesticides recorded 
high concentrations except phorate and methamidophos with total mean concentrations of 0.02 
mg/kg and 0.04 mg/kg respectively in all samples. The concentration of the organophosphates in 
the fruits and vegetables varied significantly (p < 0.05 or p= 0.013, appendix b). 
Also, five synthetic pyrethroids pesticides were detected and they include lambda-cyhalothrin, 
permethrin, cyfluthrin, deltamethrin and cypermethrin. Allethrin and bifenthrin were not 
detected. From the results, it was observed that high levels of synthetic pyrethroids were detected 
except for deltamethrin, with a mean concentration of 0.04 mg/kg. The highest concentration of 
synthetic pyrethroids in lettuce, garden eggs, pineapple and mango was cypermethrin with mean 
concentrations of 1.55 mg/kg, 0.67 mg/kg, 1.52 mg/kg and 1.35 mg/kg respectively. (Fig 4.14b 
and 4.14e). Interestingly, this observation is no different from that of the Central Region. 
The lowest concentration of synthetic pyrethroid in lettuce was obtained for lambda-cyhalothrin 
with a mean concentration of 0.05 mg/kg (Fig 4.14a). Deltamethrin was not detected in any of 
the lettuce samples analyzed. The lowest concentration of synthetic pyrethroid in garden eggs 
was observed for allethrin with a mean concentration of 0.03 mg/kg (Fig 4.14c). Lambda-
cyhalothrin was not detected in any of the garden eggs samples analyzed. Statistically, the 
University of Ghana          http://ugspace.ug.edu.gh
64 
 
difference in concentration of synthetic pyrethroids in the samples of lettuce, garden eggs, 
pineapple and mango was not significant (p > 0.05 or p= 0.938, appendix c)  
In pineapple, the lowest concentration of synthetic pyrethroid was observed for cyfluthrin with a 
mean concentration of 0.01 mg/kg (Fig 4.14e). Lambda-cyhalothrin was not detected in any of 
the pineapple samples analyzed while allethrin concentration was below detection limit.In 
mango; the lowest concentration of synthetic pyrethroid was recorded for deltamethrin with a 
mean concentration of 0.04 mg/kg (Fig 4.14f). This observation was not different from 
concentration levels of lambda-cyhalothrin recorded in samples from the Greater Accra Region. 
The absence of lambda-cyhalothrin in both pineapple and mango suggest proper use of these 
pesticides or farmers do not use these pesticides in pineapple and mango production in this 
region. In addition, the high levels of organophosphates and synthetic pyrethroids in samples 
from the Eastern Region suggests that farmers who supply vegetables and fruits to these markets 
use organophosphates and synthetic pyrethroids in significant quantities. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
University of Ghana          http://ugspace.ug.edu.gh
65 
 
Table 4.14: Concentrations (mg/kg) of organophosphates and synthetic pyrethroids in 
samples from the Eastern Region 
 a - Synthetic Pyrethroids , 
 
Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD =standard 
deviation,   
            
 
 
 
Pesticide 
 
Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Dimethoate 0.02 0.01 0-0.02 0.03 0.01 0-0.05 0.01 - - 0.08 0.06 0-0.10 
Pirimiphos-m 0.04 - 0-0.04 <0.01 - - ND - - 0.09 - 0-0.15 
Malathion ND - - 0.13 - 0-0.13 0.2 - 0-0.02 0.23 - 0-0.23 
Fenitrothion 0.04 0.02 0-0.05 0.02 - 0-0.02 0.02 - 0-0.02 0.07 - 0-0.07 
Parathion ethyl 0.02 - - 0.04 - 0-0.04 0.04 0.05 0-0.06 0.05 0.07 0-0.08 
Chlorfenvinphos 0.02 0.01 0-0.02 ND - - ND - - 0.23 0.56 0-0.42 
Profenofos 0.05 0.01 0-0.06 0.03 0.03 0-0.06 ND - 0-0.03 0.13 0.02 0-0.13 
Phorate 0.02 - 0-0.02 0.03 0.01 0-0.04 0.01 - 0-0.01 0.01 - 0-0.01 
Methamidophos 0.04 - 0-0.04 0.04 - 0-0.06 0.03 0.02 0-0.04 0.05 0.01 0-0.06 
Ethoprophos 0.07 - 0-0.07 0.02 - 0-0.02 0.22 0.56 0-0.35 0.26 - - 
Chlorpyrifos 0.19 0.57 0.04-
0.42 
0.14 055 0.02-
0.24 
0.08 0.30 0.04-
0.13 
0.3 0.15 0-0.56 
Allethrin a 0.07 0.03 0-0.12 0.03 0.01 0-0.03 <0.01 - - 0.18 0.05 0-0.24 
Lambda-cyhal a 0.05 0.01 0-0.07 <0.01 - - ND - - ND - - 
Permethrin a 0.17 0.45 0-0.37 0.09 0.34 0-0.13 0.23 0.04 0-0.16 0.13 0.06 0-0.15 
Cyflu a 0.15 0.32 0-0.67 0.12 0.41 0.02-
0.35 
0.01 - 0-0.01 0.08 - - 
Deltamethrin a  ND - - 0.04 - 0-0.04 0.04 - 0-0.04 0.04 0.05 0-0.08 
Cypermethrin a 1.55 0.41 0.89-
2.56 
0.67 0.38 0.06-
0.32 
1.52 0.34 1.18-
1.86 
1.35 0.45 0-61 
University of Ghana          http://ugspace.ug.edu.gh
66 
 
  
 
Fig 4.14a: Mean concentration levels of                               Fig 4.14b: Mean concentration levels of  synthetic   
 organophosphates in fruits and vegetables from               pyrethroids in fruits and vegetables from the    
 the Eastern Region.                                                               Eastern Region.  
 
 
 
 
 
Fig 4.14c: Mean concentration levels of                               Fig 4.14d: Mean concentration levels of     
 organophosphates  and synthetic pyrethroids in                organophosphates  and synthetic pyrethroids in  
 lettuce from the Eastern Region.                                          garden eggs from the Eastern Region.  
 
 
0
0.05
0.1
0.15
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Lettuce Garden eggs
Pineapple Mango
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Lettuce Garden eggs
Pineapple Mango
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 (
m
g/
kg
) 
Garden eggs
University of Ghana          http://ugspace.ug.edu.gh
67 
 
 
 
Fig 4.14e: Mean concentration levels of                              Fig 4.14f: Mean concentration levels of     
 organophosphates  and synthetic pyrethroids in              organophosphates  and synthetic pyrethroids in  
 pineapple from the Eastern Region.                                   mango from the Eastern Region.  
 
 
 
 
 
 
 
 
 
 
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
D
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) 
Pineapple
0
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C
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ce
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tr
at
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 (
m
g/
kg
) 
Mango
University of Ghana          http://ugspace.ug.edu.gh
68 
 
4.15: Occurrence and distribution of organophosphates and synthetic pyrethroids in 
samples from all the sampling areas 
Fig 4.15a-4.15j show the overall distribution of the various organophosphates and synthetic 
pyrethroids   levels detected in lettuce, garden eggs, pineapple, mango from the various sampling 
areas. Table 4.15 also shows the mean concentration levels of organophosphates and synthetic 
pyrethroids in samples from all sampling areas. In all, a total of eighteen pesticides including 
eleven organophosphates and seven synthetic pyrethroids were detected in the samples. The 
eleven organophosphates comprise dimethoate, pirimiphos-methyl, malathion, fenitrothion, 
parathion ethyl, chlorfenvinphos, profenofos, methamidophos, chlorpyrifos, phorate and 
ethoprophos. The seven different synthetic pyrethroid pesticides detected were allethrin, lambda-
cyhalothrin, permethrin, cyfluthrin, deltamethrin, cypermethrin and bifenthrin. 
The highest concentration of organophosphate in lettuce was recorded for malathion with a mean 
concentration of 0.26 mg/kg while the lowest concentration was recorded for parathion ethyl and 
phorate with a mean concentration of 0.02 mg/kg (Fig 4.15c). In garden eggs, the highest 
concentration of organophosphate was obtained for chlorpyrifos with a mean concentration of 
0.25 mg/kg while the lowest concentration was recorded for ethoprophos with a mean 
concentration of 0.02 mg/kg (Fig 4.15d). The highest concentration of organophosphate in 
pineapple was obtained for ethoprophos with a mean concentration of 0.22 mg/kg while the 
lowest concentration was phorate with a mean concentration of 0.01 mg/kg (Fig 4.15e). In 
mango, the highest concentration of organophosphate was observed for pirimiphos-methyl with a 
mean concentration of 0.32 mg/kg while the lowest concentration was observed for phorate with 
a mean concentration of 0.02 mg/kg (Fig 4.15f). The concentration of the organophosphates in 
University of Ghana          http://ugspace.ug.edu.gh
69 
 
the fruits and vegetables varied significantly among the sampling areas (p < 0.05 or p= 0.039, 
appendix d). 
Among the synthetic pyrethroids, cypermethrin levels were all highest in lettuce, garden eggs, 
pineapple and mango with mean concentrations of 0.97 mg/kg, 0.93 mg/kg, 1.08 mg/kg and 1.27 
mg/kg respectively (Fig 4.15g - 4.15j). The lowest concentration of synthetic pyrethroids in 
lettuce and garden eggs was recorded for allethrin with mean concentration of 0.06 mg/kg and 
0.03 mg/kg respectively while the lowest concentration in pineapple and mango was lambda-
cyhalothrin with a mean concentration of 0.01 mg/kg respectively (Fig 4.15g - 4.15j). 
Bifenmethrin was not detected in any of the samples analyzed from all the three regions. The 
difference in concentrations of synthetic pyrethroids in the samples of lettuce, garden eggs, 
pineapple and mango from all the sampling areas was not significant (statistically, p>0.05 or p= 
0.996, appendix d).  
The most occurring organophosphate in samples was chlorpyrifos while the most occurring 
synthetic pyrethroid was cypermethrin with mean concentrations of 0.15 mg/kg     and     1.10 
mg/kg respectively. Comparing these values with the maximum residue limits (MRLs) set forth 
by the FAO/WHO Codex Alimentarius Commission, cypermethrin and chlorpyrifos exceeds the 
limit of 0.05 mg/kg for both pesticides.  
The concentrations of lamda-cyhalothrin in lettuce range from 0.01-0.18 mg/kg while that of 
chlopyrifos range from 0.01-0.19 mg/kg. These values are far lower than those reported by Ntow 
(Ntow et al, 2005) who obtained 0.01-1.4 mg/kg and 0.4-6.0 mg/kg for lamda-cyhalothrin and 
chlorpyrifos respectively. About 90% of   cypermethrin (marketed as Ammo or Cymbush) 
manufactured worldwide is used to combat pests feeding on crops (WHO, 1989) and is therefore 
its high levels in fruits and vegetables. From the results, it can be deduced that some 
University of Ghana          http://ugspace.ug.edu.gh
70 
 
organophosphates and synthetic pyrethroids   levels detected in lettuce, garden eggs, pineapple, 
mango from the various sampling areas were above the maximum residue limits (MRLs) set 
forth by the FAO/WHO Codex Alimentarius Commission. 
Generally, the high frequent and high levels of organophosphates and synthetic pyrethroids in the 
fruits and vegetables analyzed is an indication that most of the modern pesticides used by 
farmers in Ghana contain these high organophosphates and synthetic pyrethroids and farmers 
may misuse or misapply them causing serious contamination. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
University of Ghana          http://ugspace.ug.edu.gh
71 
 
Table 4.15: Concentrations (mg/kg) of organophosphates and synthetic pyrethroids in 
samples from all the sampling areas 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD =standard 
deviation,   
 
 
 
 
 
 
 
 
 
 
 
 
Pesticide 
 
Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Dimethoate 0.03 0.03 0-0.06 0.03 0.02 0-0.05 0.02 0.34 0-0.05 0.06 0.07 0-0.10 
Pirimiphos-m 0.07 - 0-0.07 0.03 - 0-0.03 0.05 - 0-0.05 0.32 - 0-0.32 
Malathion 0.26 - 0-0.26 0.13 - 0-0.13 0.12 0.01 0-0.20 0.18 0.03 0-0.23 
Fenitrothion 0.05 0.04 0-0.13 0.07 0.32 0-0.12 0.03 0.02 0-0.05 0.06 0.01 0-0.07 
Parathion ethyl 0.02 - 0-0.02 0.04 - 0-0.04 0.04 0.06 0-0.06 0.05 0.02 0-0.08 
Chlorfenvinp 0.03 0.6 0-0.04 0.1 0.20 0-0.19 0.03 0.34 0-0.09 0.10 0.09 0-0.42 
Profenofos 0.03 0.02 0-0.06 0.03 0.04 0-0.06 0.03 - 0-0.03 0.06 0.03 0-0.13 
Phorate 0.02 - 0-0.02 0.03 0.02 0-0.04 0.01 - 0-0.01 0.03 0.01 0-0.04 
Methamidophos 0.06 0.43 0-0.08 0.05 0.03 0-0.11 0.07 0.03 0-0.11 0.30 0.03 0-0.78 
Ethoprophos  0.07 - 0-0.7 0.02 - 0-0.02 0.22 0.33 0-0.50 0.26 - 0-0.26 
Chlorpyrifos  0.08 0.04 0-0.42 0.25 0.02 0-1.36 0.06 - 0-0.06 0.22 0.06 0-0.34 
Allethrin a 0.06 0.21 0-0.12 0.03 0.04 0-0.08 0.04 0.57 0-0.60 0.18 0.01 0-0.24 
Lambda-cyhal a 0.18 0.04 0-0.35 0.19 0.67 0-1.17 0.01 - 0-0.01 0.01 - 0-0.01 
Permethrin a 0.1 0.50 0-0.37 0.07 0.43 0-0.13 0.15 0.01 0-0.16 0.13 0.01 0-0.15 
Cyfluthrin a 0.16 0.42 0-1.30 0.08 0.42 0-1.6 0.08 0.02 0-1.19 0.05 0.01 0-0.08 
Deltamethrin a <0.01 - - 0.04 - 0-0.04 0.07 0.02 0-0.10 0.05 0.06 0-0.08 
Cypermethrin a 0.97 0.45 0-2.56 0.93 0.50 0-2.41 1.08 0.35 0-1.91 1.27 0.50 0-3.39 
Bifenthrin a <0.01 - - 0.13 - 0-0.13 ND - - 0.05 - 0-0.05 
University of Ghana          http://ugspace.ug.edu.gh
72 
 
   
 
Fig 4.15a: Mean concentration levels of                               Fig 4.15b: Mean concentration levels of     
organophosphates in fruits and vegetables                          synthetic pyrethroids in fruits and vegetables from  
from all the sampling areas.                                                  all the sampling areas.  
 
 
 
  
 
Fig 4.15c: Mean concentration levels of                               Fig 4.15d: Mean concentration levels of     
organophosphates in lettuce   from all  the                         organophosphates in garden eggs from  all the 
sampling areas.                                                                       sampling areas.  
 
0
0.05
0.1
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0.35
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) 
Lettuce Garden eggs
Pineapple Mango
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) 
Lettuce Garden eggs
Pineapple Mango
0
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0.25
0.3
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Lettuce
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 (
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kg
) 
Garden eggs
University of Ghana          http://ugspace.ug.edu.gh
73 
 
 
 
Fig 4.15e: Mean concentration levels of                             Fig 4.15f:Mean concentration levels of     
organophosphates in pineapple   from all  the                   organophosphates in mango from  all the        
sampling areas.                                                                      sampling areas.  
 
 
 
 
   
 
Fig 4.15g: Mean concentration levels of                              Fig 4.15h: Mean concentration levels of           
synthetic pyrethroids in lettuce  from all  the                     synthetic pyrethroids in garden eggs from  all the 
sampling areas.                                                                      sampling areas.  
 
0
0.05
0.1
0.15
0.2
0.25
D
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 (
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) 
Pineapple
0
0.05
0.1
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0.3
0.35
D
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Mango
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Lettuce
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0.8
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1
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(m
g/
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) 
Garden eggs
University of Ghana          http://ugspace.ug.edu.gh
74 
 
  
 
Fig 4.15i: Mean concentration levels of                                  Fig 4.15j: Mean concentration levels   of                     
synthetic pyrethroids in pineapple   from all  the                  synthetic pyrethroids in mango from  all the 
sampling areas.                                                                          sampling areas.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0
0.2
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0.6
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1
1.2
C
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) 
Pineapple
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1.4
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 (
m
g/
kg
) 
Mango
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4.16: Occurrence and distribution of organochlorine in samples from the Greater Accra 
Region 
The values in table 4.16 indicates the mean, standard deviation and the range of values obtained 
from the analysis done on all samples  from the Greater Accra Region. A total of seven 
organochlorine pesticides were detected in the samples analyzed. Delta –HCH, gamma HCH, 
gamma-chlordane, alpha-endosulfan, dieldrin, endrin, p,p’-DDT, methoxychlor were all not 
detected in any of the samples from the Greater Accra Region. The seven pesticides which were 
detected were beta-HCH, gamma- HCH, heptachlor, p,p’-DDE, beta-endosulfan and endosulfan 
sulfate. 
 The highest mean concentration of 0.16 mg/kg was obtained for gamma HCH, in lettuce 
followed by a concentration of 0.12 mg/kg for endosulfan s and gamma HCH in pineapple and 
lettuce respectively. The concentration of the organochlorines in the fruits and vegetables did not 
vary significantly (statiscally, p >0.05 or p= 0.606, appendix a). 
Also it can a be observed that gamma HCH ( lindane )  was found in all the four samples with 
relatively higher  mean concentrations levels of 0.16 mg/kg in lettuce, 0.12  mg/kg in  garden 
eggs, 0.07  mg/kg in pineapple, and 0.08  mg/kg in mango respectively. These values were 
however higher than the mean concentrations of 0.01 mg/kg in tomato and 0.04 mg/kg in 
pawpaw detected by Bempah and Donkor, 2010 from some market sites in Accra.. Also 
comparing the results from the present study with a similar one carried out by Beena Kumari in 
India where gamma-HCH range from not -detected to 0.02 mg/kg in okro, then the market fruits 
and vegetables analyzed were highly contaminated. 
This occurrence predicts the extensive use of lindane by farmers who supply foodstuffs to Accra 
market centers. This high concentrations and wide distribution of lindane confirms earlier 
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76 
 
findings made by Bempah and Donkor, that lindane is widely used by farmers in Ghana 
(Bempah and Donkor, 2010). The other two isomers (beta-HCH and delta HCH) which are not 
insecticidal, only beta-HCH recorded mean concentrations of 0.03 mg/kg and 0.02 mg/kg in 
pineapple and mango respectively. Though p,p’ -DDT was not detected in any of the samples, 
the degradation product p,p’-DDE was found in lettuce and pineapple with mean concentrations 
of 0.08 mg/kg and 0.05 mg/kg respectively. Since p,p’ –DDT itself was not detected, the 
detection of p,p’-DDE in lettuce and pineapple may be due to previous use of p,p’ –DDT rather 
than current use. In the environment, DDT can be broken down to its metabolites such as DDE. 
This may occur as result of dehydrohalogenation (loss of HCl) of DDT. Thus p,p’ –DDT can be 
found in the environment as the parent p,p’ –DDT or its metabolites such as DDE and DDD. 
While DDT may persist in the environment for about twelve years before breaking down, its 
metabolites DDE can persist for a much longer period (Cooke and Stinger, 1982; Botwe et al, 
2007) 
 
 
 
 
 
 
 
 
 
 
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Table 4.16 Concentrations (mg/kg) of organochlorine pesticide residue detected in samples 
from the Greater Accra Region. 
       Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD =standard deviation 
 
 
 
 
Fig 4.16a: Mean concentration levels of  organochlorine pesticides in fruits and  
 vegetables from  the Greater Accra Region.                                                      
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
C
o
n
ce
n
tr
a
ti
o
n
 (
m
g
/k
g
) 
Lettuce
Garden eggs
Pineapple
Mango
Pesticide 
 
Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Beta-HCH ND - - ND - - 0.03 0.01 0-0.03 0.02 - 0-0.02 
Gamma- HCH 0.16 0.06 0.10-
0.26 
0.12 0.06 0-0.17 0.07 0.04 0-0.1 0.08 0.01 0-0.03 
Delta- HCH ND - - ND - - ND -  ND - - 
Heptachlor 0.02 - 0-0.02 0.02 - - 0.02 - 0-0.02 0.02 - 0-0.02 
Aldrin  0.01 - 0-0.01 ND - - 0.04 - 0-0.04 0.04 0.01 0-0.06 
G-chlordane ND - - ND - - ND - - ND - - 
A-endosulfan ND - - ND - - ND - - ND - - 
P,p’-DDE 0.08 0.01 0--0.08 ND - - 0.05 0.03 0.-0.08 ND - - 
Dieldrin ND - - ND - - ND - - ND - - 
Endrin ND - - ND - - ND - - ND - - 
B-endosulfan 0.01 - 0--0.01 <0.01 - - 0.01 - 0-0.01 <0.01 - - 
P,p’-DDT ND - - ND - - ND - 0 ND - - 
Endosulfan S 0.04 0.01 0-0.04 ND - - 0.12 - 0-0.12 0.01 - 0-0.01 
Methoxychlor  ND - - ND - - ND - - ND - 0 
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 Fig 4.16b: Mean concentration levels of                                 Fig 4.16c: Mean concentration levels of     
 Organochlorine pesticides in lettuce from                             organochlorine pesticides in garden egg from the      
 the Greater Accra Region.                                                      the  Greater Accra Region.  
 
 
 
 
  
 
Fig 4.16d: Mean concentration levels of                              Fig 4.16e: Mean concentration levels of     
 Organochlorine pesticides in pineapple from                    organochlorine pesticides in mango from the      
 the Greater Accra Region.                                                   the  Greater Accra Region.  
 
 
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Lettuce
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Gamma- HCH Heptachlor
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Garden eggs
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
C
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m
g/
kg
) 
Pineapple
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Mango
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4.1.7: Occurrence and distribution of Organochlorine in samples from the Central Region 
Table 4.17 and Fig 4.17a-4.17e show the various mean concentration of organochlorine pesticide 
residues detected in samples from the Central Region. In all, a total of eleven organochlorine 
pesticides were detected and they include beta-HCH, gamma- HCH, heptachlor, aldrin, alpha-
endosulfan, p,p’-DDE, dieldrin, beta-endosulfan , p,p’-DDT and  endosulfan sulfate. Delta- 
HCH, endrin and methoxychlor were not detected in any of the samples. DDT was absent in all 
samples except in pineapple which recorded a mean concentration of 0.02 mg/kg. It is interesting 
to note that in Central Region, the sample which recorded a greater no of organochlorine 
pesticides residues was lettuce followed by garden eggs with pineapple and mango recording 
fewer number of organochlorine pesticides residues. 
Heptachlor was detected in lettuce and garden eggs but was absent in pineapple and mango with 
mean concentrations of 0.05 mg/kg and 0.02 mg/kg in lettuce and garden eggs respectively. The 
highest aldrin mean concentration of 0.31 mg/kg was obtained in pineapple while the lowest was 
obtained in mango with concentration of 0.01 mg/kg. Alpha endosulfan ranged from 0-0.09 
mg/kg in lettuce, 0-0.02 mg/kg in garden eggs, 0-0.06 mg/kg in mango. The alpha endosulfan 
mean concentration values in lettuce and garden eggs were 0.09 mg/kg and 0.21 mg/kg 
respectively. Interestingly, these values are not different from its isomer endosulfan sulfate 
which recorded a mean of 0.09 mg/kg in lettuce and 0.03 mg/kg in garden eggs. The difference 
in concentration of organochlorines in the samples of lettuce, garden eggs, pineapple and mango 
was not significant (statistically, p>0.05 or p= 0.148, appendix b).  
Out of the total samples analyzed, only one sample showed the presence of p,p-DDT. The 
absence of p,p-DDT  in most of the samples analyzed is not surprising since DDT has been 
banned and no more in use. The highest concentration of p,p-DDT was detected in pineapple 
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with a mean concentration of 0.02 mg/kg but its metabolite p,p-DDE recorded no detection in 
pineaple suggesting current pesticide use contamination and not from previous use. Again even 
though p,p-DDT was not detected in lettuce and mango, its degradation product p,p-DDE was 
detected in lettuce and mango with mean concentrations of 0.04 mg/kg and 0.05 mg/kg 
respectively. This finding is an indication of the rate of degradation of the original p,p-DDT to its 
metabolite p,p-DDE. 
.Just as gamma- HCH recorded the highest mean concentration in lettuce in greater Accra so did 
gamma- HCH record the highest in Central Region samples with concentration of 0.16 mg/kg in 
lettuce. The high level of gamma- HCH detected in samples from the Central Region suggests 
that farmers in those regions use lindane in vegetable and fruit production 
Table 4.17: Concentrations (mg/kg) of oganochlorine pesticide residue detected in samples 
from the Central Region 
       Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD =standard deviation 
Pesticide Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Beta-HCH 0.13 - 0-0.13 ND - - ND - - ND - - 
Gamma- HCH 0.53 - 0-0.53 ND - - 0.07 - - 0.09 0.04 0-0.09 
Delta- HCH ND -  ND - - ND - - ND - - 
Heptachlor 0.05 - 0-0.05 0.02 - 0-0.02 ND - - ND - - 
Aldrin  0.06 0.05 0.01-
0.13 
0.02 0.01 0..01-
0.03 
0.31 - - 0.01 - 0-0.01 
G-chlordane ND - - 0.01 - 0-0.01 ND - - ND - - 
A-endosulfan 0.09 - 0-0.09 0.02 - 0-0.02 ND - - 0.04 0.03 0-0.06 
P,p’-DDE 0.04 - 0-0.04 0.01 - 0-0.01 ND - -- 0.05 - 0-0.05 
Dieldrin 0.01 - 0-0.01 0.01 - 0-0.01 ND - -- ND - - 
Endrin ND - - ND - - ND -  ND - - 
B-endosulfan 0.01 - 0-0.01 ND - - ND - - ND - - 
P,p’-DDT ND - - ND - - 0.02 - - ND - - 
Endosulfan S 0.09 - 0-0.09 0.03 0.01 0-0.04 ND - - ND - - 
Methoxychlor  ND - - ND - - ND - - ND - - 
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Fig 4.17a: Mean concentration levels of  organochlorine pesticides in fruits and  
 vegetables from  the Central Region. 
 
   
Fig 4.17b: Mean concentration levels of                            Fig 4.17c: Mean concentration levels of     
 Organochlorine pesticides in lettuce from                       organochlorine pesticides in garden egg from the      
 the Central Region.                                                            the  Central  Region. 
0
0.1
0.2
0.3
0.4
0.5
0.6
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Lettuce
Garden eggs
Pineapple
Mango
0
0.1
0.2
0.3
0.4
0.5
0.6
B
e
ta
-H
C
H
G
am
m
a-
 H
C
H
H
e
p
ta
ch
lo
r
A
ld
ri
n
G
-c
h
lo
rd
an
e
A
-e
n
d
o
su
lf
an
P
,p
’-
D
D
E 
D
ie
ld
ri
n
B
-e
n
d
o
su
lf
an
P
,p
’-
D
D
T 
En
d
o
su
lf
an
 S
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Lettuce
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
H
e
p
ta
ch
lo
r
A
ld
ri
n
G
-c
h
lo
rd
an
e
A
-e
n
d
o
su
lf
an
P
,p
’-
D
D
E 
D
ie
ld
ri
n
En
d
o
su
lf
an
 S
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Garden eggs
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Fig 4.17d: Mean concentration levels of                           Fig 4.17e: Mean concentration levels of     
 Organochlorine pesticides in pineapple from                  organochlorine pesticides in mango from the      
 the Central Region.                                                             the  Central Region.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Gamma-
HCH
Aldrin P,p’-DDT 
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Pineapple
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Mango
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4.1.8: Occurrence and distribution of Organochlorine pesticides in samples from the  
Eastern Region. 
In the Eastern Region, a total of twelve different organochlorine pesticides residues were 
detected in the four samples being the region with highest number of detected organochlorine 
pesticide residues. Like  the other two regions, delta-HCH and methoxychlor were not detected 
in any of the samples analyzed. Mango recorded the highest number of OCPs followed by 
lettuce, pineapple and garden eggs. One major mango production area in the Eastern Region 
which supplies mango to many parts of the region is Somanya. Interestingly mango sampled 
from this area recorded higher mean concentrations of organochlorine pesticides residues. This 
occurrence suggests that farmers in this part of the region use a lot of pesticides to control pests 
which might contain banned pesticides like DDT or have used DDT previously in mango 
plantations. It is therefore not surprising to detect high levels of organochlorine pesticides in 
mango samples from these areas. DDT which has been banned in Ghana was recorded in all the 
different samples of vegetables and fruits except in garden eggs with mean concentrations of 
0.02 mg/kg, 0.03 mg/kg and 0.15 mg/kg in lettuce, pineapple and mango respectively. 
Comparing with the other two regions, Eastern Region recorded the highest mean concentration 
of DDT but the difference was not significant (p= 0.07). The difference in concentration of 
organochlorines in the samples of lettuce, garden eggs, pineapple and mango from this region 
was not significant (statistically, p>0.05 or p= 0.342, appendix c).  
Fig 4.18a shows the mean concentration levels of organochlorine pesticides in fruits and 
vegetables from the Eastern Region. From the graph it can be observed that highest mean 
organochlorine pesticides concentration was obtained for gamma- HCH in lettuce with highest 
mean concentration of 0.22 mg/kg .The mean concentrations of  gamma- HCH were 0.22 mg/kg 
University of Ghana          http://ugspace.ug.edu.gh
84 
 
in lettuce , 0.03 mg/kg in garden eggs, 0.05 mg/kg in pineapple and 0.06 mg/kg in mango. The 
high concentrations of gamma- HCH in these samples suggest that famers in these areas also use 
lindane in vegetable and fruit production. 
Gamma-chlordane and alpha-endosulfan were absent in all samples except in mango recording a 
mean concentration of 0.05 mg/kg and 0.08 mg/kg for gamma-chlordane and alpha-endosulfan 
respectively. Beta-endosulfan and endosulfan sulfate mean concentrations in mango did not vary 
significantly, with mean concentration of 0.05 mg/kg and 0.04 mg/kg respectively. Dieldrin also 
recorded the highest mean concentration of 0.17 mg/kg in lettuce followed by a concentration of 
0.04 mg/kg in mango. Mean endrin concentrations ranged from (0-0.08) mg/kg in lettuce, (0-
0.02) mg/kg in garden eggs, (0-0.24) mg/kg in pineapple and no detection in mango.  
The lack of significant difference (p>0.05) which existed in some of the organochlorine residues 
detected in the samples collected in Eastern Region suggest that the contamination of samples 
might have been contributed by similar factors.  
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.18: Concentrations ( mg/kg) of oganochlorine pesticide residue detected in samples 
from the Eastern Region 
Limit of detection for all pesticides = 0.01 mg/kg , ND=not detected , SD =standard deviation 
 
 
  
 
Fig 4.18a: Mean concentration levels of  organochlorine pesticides in fruits and  
 vegetables from  the Eastern Region. 
0
0.05
0.1
0.15
0.2
0.25
B
e
ta
-H
C
H
G
am
m
a-
 H
C
H
H
e
p
ta
ch
lo
r
A
ld
ri
n
G
-c
h
lo
rd
an
e
A
-e
n
d
o
su
lf
an
P
,p
’-
D
D
E 
D
ie
ld
ri
n
En
d
ri
n
B
e
ta
-e
n
d
o
su
lf
an
P
,p
’-
D
D
T 
En
d
o
su
lf
an
 S
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Lettuce
Garden eggs
Pineapple
Mango
Pesticide Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Beta-HCH 0.07 0.03 0-0.09 ND - - ND - - ND - - 
Gamma- HCH 0.22 0.11 0.05-
0.33 
0.03 0.02 0-0.04 0.05 0.01 0-0.06 0.06 0.05 0-0.13 
Delta- HCH ND - - ND - - ND - - ND - - 
Heptachlor 0.05 0.04 0-0.08 0.02 - 0-0.02 0.13 0.11 0-0.24 ND - - 
Aldrin  0.02 0.01 0-0.03 0.05 - 0-0.05 0.03 0.02 0-0.05 0.01 0.01 0.01-
0.02 
G-chlordane ND - - ND - - ND - - 0.05 - 0-0.05 
A-endosulfan ND - - ND -- - ND - - 0.08 0.06 0-0.13 
P,p’-DDE ND - - ND - - ND - - 0.07 0.04 0-0.13 
Dieldrin 0.17 - 0-0.17 0.01 - 0-0.01 ND - - 0.04 0.03 0-0.06 
Endrin 0.07 0.04 0-0.11 ND - - ND - - 0.05 - 0-0.05 
Beta-
endosulfan 
ND - - ND - - 0.02 - 0-0.02 0.05 0.02 0-0.08 
P,p’-DDT 0.02 - 0-0.02 ND - - 0.03 - 0-0.03 0.15 0.10 0-0.28 
Endosulfan S 0.04 0.02 0-0.06 ND - - ND - - 0.04 0.03 0-0.09 
Methoxychlor  ND - - ND - - ND - - ND - - 
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86 
 
 
 
 
 
 
   
 
Fig 4.18b: Mean concentration levels of                      Fig 4.18c: Mean concentration levels of     
 Organochlorine pesticides in lettuce from                 organochlorine pesticides in garden egg from the      
 the Eastern Region.                                                      the  Eastern Region. 
 
 
 
 
   
 
Fig 4.18d: Mean concentration levels of                          Fig 4.18e: Mean concentration levels of     
 Organochlorine pesticides in pineapple from                organochlorine pesticides in mango from the      
 the Eastern Region.                                                          the  Eastern Region.  
 
 
0
0.05
0.1
0.15
0.2
0.25
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Lettuce
0
0.01
0.02
0.03
0.04
0.05
0.06
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Garden eggs
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Pineapple
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Mango
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4.1.9: Occurrence and distribution of organochlorine pesticides in samples from all the 
sampling areas 
Fig 4.19a-4.19e show the distribution of the various OCPs levels detected in lettuce, garden eggs, 
pineapple and mango from the various sampling areas. Table 4.19 also shows the mean 
concentration levels of oganochlorine pesticide residues in lettuce, garden eggs, pineapple, and 
mango from all the sampling areas. 
Out of a total of fourteen organochlorine pesticide residues, eleven were detected in lettuce, 
seven in garden eggs, ten in pineapple and twelve in mango. None of the samples recorded any 
concentration of delta HCH and methoxychlor in all the samples analyzed. Methoxychlor is an 
analogue of DDT. Half-lives in soil may depend on soil conditions as it can be less than 30 days 
in anaerobic soils and greater 100 days in aerobic soils (Fogel et al, 1982; Muir et al, 1984). It 
has also been observed that 42% of methoxychlor may remain only six months after application 
(Polyakova et al, 1984). Again several studies of the effect of methoxychlor in soil microflora 
showed that it is moderately persistent, with persistence between thirty days and a year (Howard, 
1991; Botwe, 2007). Thus methoxychlor is not as persistent as DDT and this may be the reason 
why it was not detected in the samples of lettuce, garden eggs, pineapple and mango. 
 Also pesticide concentrations range from (0-0.55) mg/kg, (0-0.17) mg/kg, (0-0.31) mg/kg and 
(0-0.28) mg/kg in lettuce, garden eggs, pineapple and mango respectively. The mean beta-HCH 
concentrations observed in all samples were 0.09 mg/kg, 0.03 mg/kg and 0.03 mg/kg in lettuce, 
pineapple and mango respectively. The mean residue levels were relatively higher for gamma-
HCH (lindane) and aldrin with aldrin recording mean concentrations of 0.45 mg/kg in lettuce, 
0.02 mg/kg in garden eggs, 0.13 mg/kg in pineapple and 0.02 mg/kg in mango. Gamma -HCH 
mean concentrations were 0.29 mg/kg in lettuce, 0.08 mg/kg in garden eggs, 0.09 mg/kg in 
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pineapple and 0.05 mg/kg in mango. Total endosulfan (alpha endosulfan +endosulfan sulfate) 
concentrations range from (0-0.09) mg/kg, (0-0.24) mg/kg, (0-0.12) mg/kg and (0-0.28) mg/kg in 
lettuce, garden eggs, pineapple and mango respectively. The difference in concentration of 
organochlorine pesticides in the samples from all the sampling areas was not significant 
(statistically, p>0.05 or p= 0.429, appendix d).  
Total DDT concentrations were 0.02 mg/kg in lettuce, 0.03 mg/kg in pineapple and 0.15 mg/kg 
in mango. DDT was not detected in garden gardens eggs. Interestingly, these values are not 
different from those obtained from the various regions. DDE/DDT ratios are often used as 
indicators of recent DDT input into the environment. Low ratios (less than one) indicates recent 
input and vice versa. DDE/DDT ratios for lettuce, garden eggs, pineapple and mango were 
calculated as 3.0, 2.0, 3.33, and 0.03 respectively. Generally, the high ratio of DDE to DDT 
mean values support the assumptions that current DDT exposure levels primarily originates from 
previous contamination as well as environmental persistence and not from current use (Ntow, 
2005;Bempah and Donkor, 2010).  
Additionally, this finding is an indication of the rate of degradation and isomerisation of the 
original organochlorine compounds to their metabolites and isomers, examples DDT to DDE in 
the terrestrial environment under the hot, dry climatic conditions which is characteristic of 
tropical climate (Jiries et al, 2002). DDT has been banned from agricultural use but has restricted 
use for public health purposes under the Stockholm convention in which Ghana is a signatory. 
The present investigation therefore gives a strong indication on the restricted use of DDT for 
agricultural and vector control purposes in Ghana. However long term persistence in the 
environment of this pesticide has been reported in various publications (Schfer and Kegley, 
2002; Fattore et al, 2002) 
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89 
 
The total heptachlor mean concentrations were 0.05 mg/kg in lettuce, 0.02 mg/kg in garden eggs, 
0.07 mg/kg in pineapple and 0.02 mg/kg in mango. Statiscally, the difference was significant 
(p=0.02). These values were however higher than the mean concentration detected in aquatic 
foods and aquatic food products (0.002 mg/kg) in China ( Pingping et al, 2007).  
 
Generally, it was observed that there were differences in the levels of pesticide residues 
(especially organophosphates) in fruits and vegetables analyzed from the different sampling 
areas. This was in accordance with a finding of the Global Environment Monitoring System 
Project on pesticides in food in ‘Global pollution and health’ that the concentrations of various 
residues in foods can vary substantially from one specific food item to another even within the 
same food group and  within the same country. The differences in the levels of pesticides in the 
vegetables and fruits observed may be attributed to a number of reasons. 
 
 The first has to do with different agricultural practices adopted by farmers and also accessibility 
of the pesticides. For instance higher quantities of pesticides may be applied in areas of massive 
pest attack and the frequency of pesticide application may be influenced by climatic conditions 
such as temperature and rainfall. Another reason why variation in pesticide concentration may 
occur is as a result of some farmers mixing cocktails of various pesticides to increase their 
efficacy or potency (Ntow et al 2005, Drechel et al 2002). This practice may also alter both the 
type and the concentrations of pesticide residues in the fruits and vegetables. 
Again within the same field, crops may receive varying amounts of pesticides due to wind drift 
and also due to non-uniform spraying. The last but not the least is the fact that plants and for that 
matter fruits and vegetables may exhibit different abilities to take up pesticide residues upon 
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exposure. This is because different plants have different biochemical mechanisms of dealing 
with foreign chemicals.  
 
 
Table 4.19: Concentrations (mg/kg) of organochlorine pesticide residues detected in 
samples from all the sampling areas. 
Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD =standard deviation 
 
 
 
 
 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Mean SD Range Mean SD Range Mean SD Range Mean SD Range 
Beta-HCH 0.09 0.04 0-0.13 ND - - 0.03 0.01 0-0.03 0.03 0.01 0-0.05 
Gamma- HCH 0.29 0.15 0.1-
0.55 
0.08 0.06 0-0.17 0.09 0.06 0-0.21 0.05 0.04 0-0.13 
Delta- HCH ND - - ND - - ND - - ND - - 
Heptachlor 0.05 0.03 0-0.08 0.02 - 0-0.02 0.07 0.01 0-0.24 0.02 - 0-0.02 
Aldrin  0.45 0.04 0-0.13 0.02 0.01 0-0.03 0.13 0.12 0-0.31 0.02 0.01 0-0.02 
G-chlordane ND - - ND - - 0.01 - 0-0.01 0.05 - 0-0.05 
A-endosulfan 0.08 0.03 0-0.09 0.02 - 0-0.02 0.03 - 0-0.03 0.07 0.05 0-0.13 
P,p’-DDE 0.06 0.02 0-0.08 0.01 - 0-0.01 0.1 0.03 0-0.09 0.05 0.04 0-0.13 
Dieldrin 0.08 0.04 0-0.17 0.01 - 0-0.01 ND - - 0.04 0.02 0-0.06 
Endrin 0.07 0.04 0-0.11 ND - - ND - - 0.05 - 0-0.05 
B-endosulfan 0.01 - 0-0.01 ND - - 0.02 0.01 0-0.02 0.05 0.02 0-0.08 
P,p’-DDT 0.02 - 0-0.02 ND - - 0.03 0.01 0-0.03 0.15 0.10 0-0.28 
Endosulfan S 0.05 0.01 0-0.06 0.03 0.01 0-0.04 0.12 - 0-0.12 0.04 0.04 0-0.09 
Methoxychlor  ND - - ND - - ND - - ND ND - 
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Fig 4.19a: Mean concentration levels of  organochlorine pesticides in fruits and  
 vegetables  from all sampling areas. 
 
 
 
 
 
   
 
Fig 4.19b: Mean concentration levels of                        Fig 4.19c: Mean concentration levels of     
 Organochlorine pesticides in lettuce from                   organochlorine pesticides in garden eggs  
 all the sampling areas.                                                    from  all   the sampling areas.  
 
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
C
o
n
ce
n
tr
at
io
n
 (
m
g/
kg
) 
Lettuce
Garden eggs
Pineapple
Mango
0
0.05
0.1
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0.2
0.25
0.3
0.35
0.4
0.45
0.5
B
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 H
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 S
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 (
m
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0
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0.02
0.03
0.04
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0.06
0.07
0.08
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 H
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 (
m
g/
kg
) 
Garden eggs
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Fig 4.19d: Mean concentration levels of                          Fig 4.19e: Mean concentration levels of     
 Organochlorine pesticides in pineapple from                organochlorine pesticides in mango from  all      
 all the sampling areas.                                                      the sampling areas.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
B
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-H
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 H
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an
 S
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at
io
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 (
m
g/
kg
) 
Pineapple
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
B
e
ta
-H
C
H
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 H
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 S
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at
io
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 (
m
g/
kg
) 
Mango 
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4.2: Tolerance limits 
The concentration of organochlorine pesticides in various fruits and vegetables sampled from the 
selected sampling areas were compared with maximum residue limits (MRLs) set forth by the 
FAO/WHO Codex Alimentarius Commission (table below). 
Table 4.20: Highest organochlorine pesticide residue concentration found in lettuce, garden 
eggs, pineapple, mango from the selected sampling areas compared with FAO/WHO 
maximum residue limits (mg/kg). 
 
Pesticides 
              Highest amounts found              Maximum residue limit 
 Lettuce Garden 
eggs 
Pineapple Mango Lettuce Garden 
eggs 
Pineapple Mango 
          
Beta-HCH  0.13 ND 0.03 0.05 0.1 0.1 0.1 0.1 
G- HCH  0.55 0.17 0.21 0.13 0.1 0.1 0.1 0.1 
Delta- HCH  ND ND ND ND 0.1 0.1 0.1 0.1 
Heptachlor  0.08 0.02 0.24 0.02 0.01 0.01 0.01 0.01 
Aldrin   0.13 0.03 0.31 0.02 0.05 0.05 0.05 0.05 
G -chlordane  ND ND 0.01 0.05 0.02 0.02 0.02 0.02 
A-endosulfan  0.09 0.02 0.03 0.13 0.1 0.1 0.5 0.5 
P,p’-DDE  0.08 0.01 0.06 0.13 0.05 0.05 0.05 0.05 
Dieldrin  0.08 0.01 ND 0.06 0.05 0.05 0.05 0.05 
Endrin  0.11 ND ND 0.08 0.05 0.05 0.05 0.05 
β-endosulfan  0.01 ND 0.02 0.28 0.1 0.1 0.5 0.5 
P,p’-DDT  0.02 ND 0.03 0.28 0.05 0.05 0.05 0.05 
Endosulfan S  0.06 0.04 0.12 0.09 0.1 0.1 0.5 0.5 
Methoxychlor  ND ND ND ND 0.01 0.01 0.01 0.01 
Limit of detection for all pesticides = 0.01 mg/kg , ND=not detected , SD =standard deviation 
 
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From table 4.20, it can  be observed that the  highest concentration of gamma- HCH (lindane) 
recorded in lettuce (0.55 mg/kg), garden eggs (0.17 mg/kg), pineapple (0.21 mg/kg) and mango 
(0.13 mg/kg) were all higher than the maximum residue limits (MRLs) set forth by the 
FAO/WHO Codex Alimentarius Commision. Also the highest concentration of   Beta-HCH in all 
samples except lettuce were all lower than the maximum residue limits (MRLs) set forth by the 
FAO/WHO Codex Alimentarius Commission while no concentrations of Delta-HCH and 
methoxychlor were recorded in any of the samples. 
Heptachlor concentrations in all samples were above the MRLs values. In addition, highest 
endosulfan levels (alpha-endosulfan and beta-endosulfan) in lettuce, garden eggs, pineapple and 
mango were all lower than the maximum residue limits (MRLs) set forth by the FAO/WHO 
Codex Alimentarius Commision. 
The concentration of DDT in mango was above the maximum residue limits (MRLs) but was 
lower than the MRLs in lettuce, garden eggs and pineapple. The highest DDE values were all 
above the MRLs except in garden eggs which recorded a concentration of 0.01 mg/kg. Gamma-
chlordane values were all lower than the maximum residue limits (MRLs) set forth by the 
FAO/WHO Codex Alimentarius Commision except in mango which recorded highest value of 
0.05 mg/kg. Also highest aldrin concentrations in lettuce and pineapple were higher than the 
MRLs. However its concentrations in garden eggs and mango were all below the   MRLs. 
It is interesting to note that both diedrin and endrin highest concentration in lettuce and mango 
were all above the MRLs while their highest concentration in garden eggs, pineapple were all 
below the MRLs. 
Generally, it can be deduced from the data that some fruit and vegetable samples analyzed 
contain residues of the monitored organochlorines above the accepted maximum residue limits 
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(MRLs) adopted by the FAO/WHO Codex Alimentarius Commision. Since fruits and vegetables 
consumption by humans is an indispensable part of our daily life, this makes the safety of market 
fruits and vegetables an important health issue and therefore underscores the importance of the 
potential health risks of organochlorine pesticides in fruits and vegetables. 
 
4.2.1: Health Risk Assessment 
In view of the potential toxicity associated with organochlorine pesticides than the other types of 
pesticides, it was prudent to conduct a health risk assessment on organochlorine pesticides in 
order to help consumers make informed choices when buying fruits and vegetables since food 
consumption is an important route of human exposure to organochlorine pesticides residues 
(Jiang et al, 2005). 
In estimating the potential health risk associated with each organochlorine pesticide, the 
following assumptions were made based on the United States Environmental Protection 
Agency’s guidelines (USEPA, 1996). The first is that a hypothetical body weight of 70 kg for 
adults and 10 kg for children and the second is that there is maximum absorption rate of 100% 
and bioavailability rate of 100%. In Ghana, food consumption rate for fruits and vegetables is 
found to be 0.064 mg/kg (Bempah, 2008). Therefore for each type of exposure, the estimated 
lifetime exposure dose (mg/kg) was obtained by multiplying the residual pesticide concentration 
(mg/kg) in the food of interest by the food consumption rate (mg/kg) and dividing the product by 
the body weight (kg). The hazard indices for adults and children were computed as ratios 
between estimated pesticides exposure doses and the reference doses which are considered to be 
safe levels of exposure over the lifetime. 
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Tables 4.21, 4.22, 4.23 and 4.24 show the reference dose, the estimated dose and the 
corresponding hazard index for each organochlorine pesticide in lettuce, garden eggs, pineapple 
and mango respectively. The data analysis indicates that organochlorine pesticides such as beta-
HCH, gamma-HCH, alpha endosulfan, beta endosulfan, p,p-DDE and DDT do not pose a direct 
hazard to human even though residual concentration were detected in  all the four different 
samples. Heptachlor, aldrin, dieldrin gamma chlordane however had their hazard indexes more 
than unity in the samples in one or more of the samples indicating a potential systemic toxicity 
especially in children. 
The results further indicate that heptachlor in particular may be of public concern since its 
concentration levels exceeded the reference dose in all the four different types of samples 
analyzed indicating a great potential for systemic toxicity to consumers in Ghana. 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.21: Health risk estimates for systemic effects associated with pesticide residues   
  in   Lettuce 
 
Pesticide Reference dose  
( mg/kg/day) 
Estimated dose 
 ( mg/kg/day) 
hazard index  health  
risk 
Beta -HCH 0.003 8.23  x10-5 [adult] 0.027 no 
  5.76 x10
-4[children] 0.192 no 
Gamma- HCH 0.003 2.65 x10-4[adult] 0.088 no 
  1.86 x10-3[children] 0.619 no 
Heptachlor 0.0001 4.57 x10-5[adult] 0.457 no 
  3.20 x10-4[children] 3.200 yes 
Aldrin  0.0002 4.57 x10-5[adult] 0.229 no 
  3.20 x10-4[children] 
 
1.600 yes 
Alpha-endosulfan 0.006 7.31 x10-5 [adult] 0.012 no 
  5.12 x10-4[children] 
 
0.085 no 
Beta -endosulfan 0.006 9.14 x10-6[adult] 0.002 no 
  6.40 x10-5 [children] 
 
0.011 no 
P,p’-DDE 0.02 5.49 x10-5 [adult] 0.003 no 
  3.84 x10-5 [children] 
 
0.019 no 
Dieldrin 0.0002 7.31 x10-5 [adult] 0.366 no 
  5.12 x10-4 [children] 
 
2.560 yes 
Endrin 0.0002 6.40 x10-5 [adult] 0.320 no 
  4.48 x10-4 [children] 
 
2.240 yes 
P,p’-DDT 0.02 1.83 x10-5 [adult] 0.001 no 
  1.28 x10-5  [children] 0.0064 no 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.22: Health risk estimates for systemic effects associated with pesticide residues   
  in   garden eggs 
 
Pesticide Reference dose  
( mg/kg/day) 
    Estimated dose  
     ( mg/kg/day) 
Hazard index Health  risk 
Gamma- HCH 0.003 7.31 x10-5[adult]    0.024 no 
  5.12 x10-4[children]    0.171 no 
Heptachlor 0.0001 1.83 x10-5[adult]    0.183 no 
  1.28 x10-4[children]    1.280 yes 
Aldrin  0.0002 1.83 x10-5[adult]    0.091 no 
  1.28 x10-4[children]    0.640 no 
Alpha-endosulfan 0.006 1.83 x10-5[adult]    0.003 no 
  1.28 x10-4[children]    0.021 no 
P,p’-DDE 0.02 9.14 x10-6[adult]    0.000 no 
  6.4 x10-5[children]    0.003 no 
      
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.23: Health risk estimates for systemic effects associated with pesticide residues   
  in   pineapple 
 
Pesticide Reference dose 
( mg/kg/day) 
Estimated dose 
( mg/kg/day) 
Hazard index Health 
risk 
     
Beta -HCH 0.003 2.74 x10-5[adult] 0.009 no 
  1.92 x10
-4 [children] 
 
0.064 no 
Gamma- HCH 0.003 8.23 x10-5[adult] 0.027 no 
  5.76 x10-4 [children] 
 
0.192 no 
Heptachlor 0.0001 6.40 x10-5[adult] 0.640 no 
  4.48 x10-4[children] 
 
4.480 yes 
Aldrin  0.0002 1.19 x10-4[adult] 0.594 no 
  8.32 x10-4 [children] 
 
4.160 yes 
Gamma chlordane 0.0001 9.14 x10-6[adult] 0.091 no 
  6.40 x10-5 [children] 
 
0.640 no 
Alpha-endosulfan 0.006 2.74 x10-5[adult] 0.005 no 
  1.92 x10-4[children] 
 
0.032 no 
Beta -endosulfan 0.006 1.83 x10-5[adult] 0.003 no 
  1.28 x10-4 [children] 
 
0.021 no 
P,p’-DDE 0.02 5.49 x10-5[adult] 0.003 no 
  6.40 x10-4[children] 
 
0.032 no 
P,p’-DDT 0.02 2.74 x10-5[adult] 0.001 no 
  1.92 x10-4 [children] 0.010 no 
     
 
 
 
 
 
 
 
 
 
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Table 4.24: Health risk estimates for systemic effects associated with pesticide residues   
  in   Mango 
 
Pesticide Reference dose 
( mg/kg/day) 
Estimated dose 
( mg/kg/day) 
Hazard index Health 
 risk 
     Beta -HCH 0.003 2.74 x10-5[adult] 0.009 no 
  1.92 x10
-4 [children] 
 
0.064 no 
Gama- HCH 0.003 4.57 x10-5[adult] 0.015 no 
  3.20 x10-4[children] 
 
0.107 no 
 Heptachlor 0.0001 1.83 x10-5[adult] 0.183 no 
  1.28 x10-4 [children] 
 
1.280 yes 
Aldrin  0.0002 1.83 x10-5 [adult] 0.091 no 
  1.28 x10-4[children] 
 
0.640 no 
Gamma chlordane 0.0001 4.57 x10-5 [adult] 0.457 no 
  3.20 x10-4[children] 
 
3.200 yes 
Alpha-endosulfan 0.006 6.40 x10-5 [adult] 0.011 no 
  4.48 x10-4[children] 
 
0.075 no 
Beta -endosulfan 0.006 4.57 x10-5 [adult] 0.008 no 
  3.20 x10-4[children] 
 
0.053 no 
P,p’-DDE 0.02 4.57 x10-5 [adult] 0.002 no 
  3.20 x10-4[children] 
 
0.016 no 
Deldrin 0.0002 3.66 x10-5 [adult] 0.183 no 
  2.56 x10-4[children] 
 
1.280 yes 
Endrin 0.0002 4.57 x10-5 [adult] 0.229 no 
  3.20 x10-4[children] 
 
1.600 yes 
P,p’-DDT 0.02 1.37 x10-4 [adult] 0.007 no 
  9.60 x10-4[children] 0.048 no 
 
  
 
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CHAPTER FIVE 
5.0 CONCLUSION AND RECOMMENDATIONS 
5.1  Conclusions 
 The results of this study indicate that some Ghanaian market vegetables and fruits are 
contaminated with different types of pesticides of which organophosphates and synthetic 
pyrethroids are the most common. Chlorpyrifos and cypermethrin were the most frequent 
pesticides among the organophosphates and synthetic pyrethroids respectively with 
higher concentration levels. 
 Twelve organochlorine pesticides were detected of which seven are among the banned 
pesticides of the environmental protection agency (EPA) of Ghana. These banned 
organochlorine pesticides are: heptachlor, aldrin, dieldrin, lindane (gamma-HCH), endrin, 
gamma chlordane and DDT ( Afful et al,2010)).  The occurrence of organochlorine 
pesticide residues in the vegetables and fruits could be due to   its illegal use or due to 
historic use since these chemicals are prohibited from agricultural use. Lindane was the 
most common organochlorine pesticide while lettuce was the most frequently 
contaminated sample. . 
 There were no significant variations in the levels of pesticides in the four samples as well 
as the sampling areas (p>0.05) even though there were differences in residual 
concentrations of pesticides. The differences in residual concentrations of pesticides 
could be due to different agricultural practices adopted by farmers and also accessibility 
of the pesticides. 
 The concentrations of organochlorine pesticide residues were generally low. However, 
the  concentration of OCPs in some fruits and vegetables exceeded the maximum 
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tolerable limits or maximum residue limits (MRLs)  adopted by the FAO/WHO Codex 
Alimentarius Commission. 
 Health risk analysis Indicates that heptachlor in particular may be of public concern since 
its concentration levels exceeded the reference dose in all the four different types of 
samples analyzed indicating a great potential for systemic toxicity to consumers in 
Ghana. 
 
5.2 Recommendations. 
 Future monitoring programs are recommended to acquire adequate information regarding 
the levels of pesticides especially organochlorines in vegetables and fruits. 
 The ministry of agriculture and the environmental protection agency need to check and 
enforce regulations on the use of banned pesticides in Ghana. 
 There is the need to conduct a dietary survey for the entire population of Ghana to 
generate a food consumption database so that a more complete health risk assessment 
could be done in the future. 
 Farmer education on safe pesticide use should be intensified to limit the levels of 
pesticides residues in fruits and vegetables. 
 
 
 
 
 
 
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                                                 Appendix A 
                                               ANOVA ANALYSIS 
 
                                      GREATER ACCRA REGION 
   Organophosphates 
ANOVA 
      Source of 
Variation SS       df MS F P-value F crit 
Between Groups 0.0262 3 0.008733 0.764565 0.525063 3.008787 
Within Groups 0.274143 24 0.011423 
   
       Total 0.300343 27         
 
 
 Synthetic pyrethroids 
ANOVA 
      Source of 
Variation SS        df MS F P-value F crit 
Between Groups 0.183443 6 0.030574 5.492301 0.00149 2.572712 
Within Groups 0.1169 21 0.005567 
   
       Total 0.300343 27         
 
 
Organochlorines  
ANOVA 
      Source of 
Variation SS 
           
df MS F P-value F crit 
Between Groups 0.002406 3 0.000802 0.618847 0.606207 2.798061 
Within Groups 0.0622 48 0.001296 
   
       Total 0.064606 51         
        
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Appendix B 
                                            ANOVA ANALYSIS 
                                                CENTRAL REGION 
Organophosphates 
 
ANOVA 
      Source of 
Variation SS           df MS F P-value F crit 
Between Groups 0.06905 7 0.009864 3.4561 0.010589 2.422629 
Within Groups 0.0685 24 0.002854 
   
       Total 0.13755 31         
 
 
Synthetic pyrethroids 
ANOVA 
      Source of 
Variation SS         df MS F P-value F crit 
Between Groups 0.04675 3 0.015583 0.035038 0.990934 3.098391 
Within Groups 8.8951 20 0.444755 
   
       Total 8.94185 23         
         
 
Organochlorines 
ANOVA 
      Source of 
Variation SS           df MS F P-value F crit 
Between Groups 0.123621 13 0.009509 1.527021 0.147869 1.961218 
Within Groups 0.26155 42 0.006227 
   
       Total 0.385171 55         
 
                                            
 
 
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Appendix C 
                                            ANOVA ANALYSIS 
                                                  EASTERN REGION 
Organophosphates 
ANOVA 
      Source of 
Variation SS           df MS F P-value F crit 
Between Groups 0.064555 3 0.021518 4.04408 0.013314 2.838745 
Within Groups 0.212836 40 0.005321 
   
       Total 0.277391 43         
        
 
  Synthetic pyrethroids 
ANOVA 
      Source of 
Variation SS          df MS F P-value F crit 
Between Groups 0.107233 3 0.035744 0.134847 0.938108 3.098391 
Within Groups 5.3015 20 0.265075 
   
       Total 5.408733 23         
 
 
Organochlorines 
ANOVA 
      Source of 
Variation SS 
           
df MS F P-value F crit 
Between Groups 0.03118 13 0.002398 1.156894 0.342848 1.961218 
Within Groups 0.087075 42 0.002073 
   
       Total 0.118255 55         
                                                      
 
 
 
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Appendix D 
                                           ANOVA ANALYSIS 
                                                                  OVERALL  
Organophoshates 
ANOVA 
      Source of 
Variation SS 
            
df MS F P-value F crit 
Between Groups 0.05733 3 0.019112 3.052833 0.039358 2.838745 
Within Groups 0.250418 40 0.00626 
   
       Total 0.307755 43         
        
Synthetic pyrethroids 
ANOVA 
      Source of 
Variation SS 
           
df MS F P-value F crit 
Between Groups 0.008754 3 0.002918 0.020159 0.996005 3.008787 
Within Groups 3.473857 24 0.144744 
   
       Total 3.482611 27         
 
 
Organochlorines 
ANOVA 
      Source of 
Variation SS 
           
df MS F P-value F crit 
Between Groups 196.0909 3 65.36362 0.938813 0.429288 2.798061 
Within Groups 3341.939 48 69.62372 
   
       Total 3538.029 51         
         
 
 
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Appendix E 
Table 6.1: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from Mallam Atta market. 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate 0.02 0.05 ND 0.03 
Pirimiphos-methy ND ND <0.01 ND 
Malathion ND ND 0.03 ND 
Fenitrothion 0.13 ND ND ND 
Parathion ethyl ND ND 0.14 ND 
Chlorfenvinphos 0.04 ND ND ND 
Profenofos <0.01 0.02 ND ND 
Methamidophos ND 0.04 ND ND 
Chlorpyrifos 0.02 1.36 ND 0.02 
Allethrin a ND 0.08 <0.01 ND 
Lambda-cyhalothrin a 0.13 0.03 ND ND 
Permethrin a 0.02 ND ND ND 
Cyfluthrin a 0.02 0.03 0.15 0.07 
Deltamethrin a <0.01 0.04 ND ND 
Cypermethrin a <0.01 0.63 0.21 0.36 
 Bifenthrin a ND 0.13 ND ND 
   a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD= 
standard   deviation 
 
 
                                                     Appendix F 
 
Table 6.2: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from  Agbobloshie    market. 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate ND ND ND 0.03 
Pirimiphos-methyl ND <0.01 ND 0.56 
Malathion 0.26 0.13 0.17 0.12 
Parathion ethyl 0.08 0.02 0.05 0.02 
Chlorfenvinphos ND 0.19 0.02 0.02 
Profenofos 0.02 ND <0.01 0.02 
Phorate ND ND 0.02 ND 
Methamidophos ND 0.02 ND ND 
Ethoprophos ND 0.02 ND ND 
Chlorpyrifos ND 0.19 ND ND 
Allethrin a ND 0.06 ND ND 
Lambda-cyhalothrin a 0.03 ND ND ND 
Permethrin a ND 0.08 <0.01 ND 
Cyfluthrin a 0.06 0.24 ND 0.02 
Cypermethrin a 0.04 0.19 ND ND 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, 
SD=standard  deviation 
 
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Appendix G 
Table 6.3: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from  Madina   market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Fonofos 0.02 ND ND ND 
Dimethoate ND 0.05 <0.01 0.03 
Pirimiphos-methyl ND ND ND 0.56 
Malathion ND ND ND 0.12 
Fenitrothion 0.02 0.12 0.02 ND 
Parathion ethyl ND ND ND 0.02 
Chlorfenvinphos ND ND ND 0.02 
Profenofos ND ND ND 0.02 
Phorate 0.03 ND <0.01 0.02 
Methamidophos 0.08 ND ND ND 
Chlorpyrifos 0.01 0.09 0.04 ND 
Allethrin a <0.01 0.02 ND ND 
a - Synthetic Pyrethroid ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
 
Appendix H 
 
Table 16: Mean concentration levels (mg/kg) of organophosphate pesticide residues detected in 
samples from Kaneshie   market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Fonofos ND ND 0.01 ND 
Dimethoate ND <0.01 0.05 ND 
Pirimiphos-methy 0.09 ND 0.05 ND 
Malathion ND ND <0.01 ND 
Fenitrothion ND ND 0.05 0.05 
Parathion ethyl ND 0.12 ND ND 
Chlorfenvinphos 0.02 ND ND ND 
Profenofos ND ND 0.03 ND 
Methamidophos 0.02 <0.01 0.06 0.78 
Chlorpyrifos <0.01 0.16 0.09 ND 
Limit of detection for all pesticides:  0.01mg/kg                             ND-not detected 
 
 
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Appendix I 
Table 17: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from capecoast market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate 0.04 0.01 0.01 ND 
Fenitrothion 0.02 ND ND ND 
Chlorfenvinphos 0.03 0.01 0.01 0.01 
Profenofos 0.03 ND ND ND 
Phorate <0.01 ND ND 0.01 
Methamidophos 0.05 0.11 0.11 0.06 
Ethoprophos <0.01 ND ND ND 
Chlorpyrifos 0.02 0.07 0.07 ND 
Lambda-cyhalothrin a 0.71 ND ND <0.01 
Permethrin a 0.06 0.05 ND ND 
Cyfluthrin a 0.26 0.08 ND ND 
Fenvalerate a ND ND 0.03 ND 
Cypermethri a n 1.75 1.63 1.46 1.41 
Bifenthrin a <0.01 ND ND ND 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
 
 
 
 
 
                                                 
 
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Appendix J 
Table 18: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from Mankessim market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate 0.06 ND ND <0.01 
Parathion ethyl ND <0.01 ND ND 
Chlorfenvinphos ND ND <0.01 ND 
Profenofos ND ND ND 0.04 
Phorate ND 0.02 ND <0.01 
Methamidophos 0.07 0.07 ND ND 
Chlorpyrifos ND 0.27 0.02 0.34 
Allethrin a 0.06 0.04 ND ND 
Lambda-cyhalothrin a 0.17 0.27 0.01 ND 
Permethrin a 0.07 0.04 0.01 ND 
Cyfluthrin a ND <0.01 ND ND 
Cypermethrin a 1.16 2.41 1.91 ND 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
 
 
 
 
 
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Appendix K 
Table 19: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from Kasoa market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Parathion ethyl ND <0.01 ND ND 
Chlorfenvinphos ND ND ND 0.08 
Phorate ND ND ND 0.06 
Chlorpyrifos ND ND 0.02 0.11 
Allethrin a 0.04 ND ND ND 
Lambda-cyhalothrin a 0.35 0.06 ND 0.01 
Permethrin a 0.05 0.02 0.03 ND 
Cyfluthrin a 0.21 ND ND ND 
Deltamethrin a ND ND ND 0.03 
Cypermethrin a 0.92 1.34 1.19 3.39 
  a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
 
 
 
 
 
 
 
 
 
                                                    
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Appendix L 
Table 20: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from swedru market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate ND 0.01 ND ND 
Chlorfenvinphos ND ND ND 0.02 
Phorate ND ND <0.01 0.02 
Methamidophos 0.043 0.03 ND ND 
Ethoprophos 0.02 <0.01 ND ND 
Chlorpyrifos 0.06 ND ND ND 
Allethrin a 0.03 0.01 ND ND 
Lambda-cyhalothrin a 1.17 ND ND ND 
Permethrin a 0.25 0.09 0.16 0.13 
Cyfluthrin a 0.41 0.07 ND 0.03 
Deltamethrin a ND ND 0.10 0.06 
Cypermethrin a 1.53 1.41 1.50 1.54 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
 
 
 
 
 
 
                                            
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Appendix M 
Table 21: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from koforidua market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate ND 0.02 ND 0.10 
Pirimiphos-methy ND ND ND 0.15 
Malathion ND ND ND 0.23 
Fenitrothion ND 0.02 ND 0.07 
Parathion ethyl ND ND ND 0.08 
Chlorfenvinphos 0.02 ND ND 0.42 
Profenofos ND 0.02 ND 0.23 
Phorate  ND 0.04 0.01 ND 
Methamidophos ND 0.04  0.04 0.06 
Ethoprophos <0.01 ND <0.01 0.35 
Chlorpyrifos 0.42 0.02 0.05 0.56 
Allethrin a 0.01 ND ND 0.24 
Lambda-cyhalothrin a 0.07 ND ND ND 
Permethrin a 0.07 ND 0.30 ND 
Cyfluthrin a 0.05 0.02 0.01 ND 
Deltamethrin a ND ND 0.04 0.01 
Cypermethrin a 0.89 0.17 1.18 1.21 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
 
 
 
                                                       
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Appendix N 
Table 22: Mean concentration levels (mg/kg) of organophosphate and synthetic pyrethroids 
pesticide residues detected in samples from Somanya market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate 0.02 ND ND 0.06 
Pirimiphos-methy ND ND ND 0.03 
Malathion ND ND 0.20 ND 
Fenitrothion 0.03 ND ND ND 
Parathion ethyl ND ND 0.06 0.02 
Chlorfenvinphos 0.02 ND ND 0.04 
Profenofos ND ND 0.09 ND 
Phorate <0.01 ND ND ND 
Methamidophos 0.04 ND ND 0.05 
Ethoprophos ND ND ND 0.26 
Chlorpyrifos 0.14 0.16 0.13 0.30 
Lambda-cyhalothrin a 0.07 <0.01 ND ND 
Permethrin a 0.08 0.13 ND ND 
Cyfluthrin a 0.18 0.05 ND ND 
Deltamethrin a ND <0.01 ND 0.08 
Cypermethrin a 1.21 0.32 ND 1.61 
Bifenthrin a ND ND ND 0.05 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
 
 
 
 
                                                     
 
 
 
 
 
 
 
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Appendix O 
Table 23: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from Asamankese market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate ND 0.02 0.01 ND 
Pirimiphos-methyl 0.04 ND ND ND 
Malathion ND 0.13 ND ND 
Fenitrothion ND ND 0.02 ND 
Parathion ethyl 0.02 0.04 ND ND 
Chlorfenvinphos 0.01 ND 0.03 ND 
Profenofos 0.06 0.06 ND 0.03 
Methamidophos <0.01 ND ND ND 
Ethoprophos ND ND 0.08 ND 
Chlorpyrifos 0.04 0.12 0.04 ND 
Allethrin a ND 0.03 <0.01 ND 
Lambda-cyhalothrin a 0.01 ND ND ND 
Permethrin a ND ND 0.16 0.11 
Cyfluthrin a ND 0.05 ND ND 
Deltamethri a ND ND ND 0.01 
Cypermethrin a ND 0.06 1.86 ND 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
                                                    
 
 
 
 
 
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Appendix P 
Table 24: Mean concentration levels (mg/kg) of organophosphate and  synthetic pyrethroids 
pesticide residues detected in samples from Nsawam  market. 
 
Pesticide Lettuce Garden eggs Pineapple Mango 
Dimethoate 0.01 0.05 ND <0.01 
Pirimiphos-methyl ND <0.01 ND ND 
Fenitrothion 0.05 ND ND <0.01 
Parathion ethyl ND ND 0.01 ND 
Chlorfenvinphos 0.05 ND <0.01 0.02 
Profenofos 0.04 0.02 ND ND 
Phorate 0.02 0.02 ND 0.01 
Methamidophos ND 0.04 0.01 0.04 
Ethoprophos 0.07 0.02 ND <0.01 
Chlorpyrifos 0.16 0.24 0.11 0.03 
Allethrin a 0.12 0.02 ND 0.12 
Permethrin a 0.37 0.04 ND 0.15 
Cyfluthrin a 0.22 0.35 ND 0.08 
Deltamethrin a ND 0.04 ND 0.04 
Cypermethrin a 2.56 2.12 ND 1.24 
a - Synthetic Pyrethroids ,  Limit of detection for all pesticides = 0.01 mg/kg, ND=not detected, SD 
=standard        deviation 
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