UNIVERSITY OF GHANA COLLEGE OF BASIC AND APPLIED SCIENCES DEPARTMENT OF NUTRITION AND FOOD SCIENCE EXPOSURE ASSESSMENT OF SOME HEAVY METALS (ARSENIC, LEAD, CADMIUM, MERCURY, COPPER AND ZINC) IN LOCALLY PRODUCED RICE SOLD IN ACCRA METROPOLIS BY DESMOND ASANTE KARIKARI (10876190) THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF MASTER OF PHILOSOPHY FOOD SCIENCE DEGREE AUGUST 2023 University of Ghana http://ugspace.ug.edu.gh ii DECLARATION This is to certify that this thesis is the results of research by Desmond Asante Karikari under supervision towards the award of MPhil degree in the Department of Nutrition and Food Science. University of Ghana, Legon. Signatures: Desmond Asante Karikari Date (Candidate) Supervisory Committee Dr. Bennett Atta Dzandu Date (Main Supervisor) Dr. Joycelyn K. Quansah Date (Co Supervisor) University of Ghana http://ugspace.ug.edu.gh iii ABSTRACT Rice is the second-most consumed cereal in Ghana. However, human activities such as mining and excessive use of agro-chemicals in some farming areas have the potential to pollute rice with heavy metals, and compromise food safety. The objective of this study was to assess the levels and risk of heavy metals in locally produced rice sold in Accra Metropolis. Also, the quantity and consumption pattern of rice in Accra was also surveyed using structured questionnaire. A total of 385 consumers who consented participated in the survey. Information collected included sex, age, and body weight as well as frequency and quantity of rice consumed. Children’s consumption information was collected from parents or caregivers. Thirty samples of local rice (uncooked) were sampled from markets and analyzed for heavy metals (arsenic, lead, cadmium, mercury, copper, and zinc) using ICP-MS. Exposure assessment was conducted using the U.S. EPA method. The estimated intake, carcinogenic and non-carcinogenic risk were determined. Survey results showed participants weighed between 60 and 69 kg, consumed an average of 496.36 grams of rice per week and 221.67 grams of rice per day. Children consumed averagely 58.33 grams of rice per day and 142.43 grams of rice per week and they weighed between 21 and 30 kg. Concentration of heavy metals in all the rice samples were below the upper limit permitted by Codex. However, the consumption of local rice was found to be associated with carcinogenic and non-carcinogenic hazards in both adults and children from the outcome of the risk assessment. Exposure to arsenic, lead, and cadmium were of primary concern for the children whilst for the adults, it was arsenic and lead. The health risk of exposure to heavy metals should be publicized and education intensified in order to protect public health. University of Ghana http://ugspace.ug.edu.gh iv DEDICATION I dedicate my dissertation work to my late dad, Mr. Kwabena Asante Karikari and the rest of my family. A special feeling of gratitude for you all. University of Ghana http://ugspace.ug.edu.gh v ACKNOWLEDGEMENT My deepest gratitude goes to God who has provided all that was needed to complete this program of study. My utmost regard also goes to Akua Nyarko, Mr. P.M Fosu, Mrs. Lydia Asare-Bediako, Dr. Paul Osei-Fosu, Mr. Derry Dontoh and Mr. Adongo Ayamba Abdul-Malik who painstakingly laid the foundation for my education giving it all it takes. My appreciation also goes to my supervisors, Dr. Bennett Atta Dzandu and Dr. Joycelyn k Quansah, who have been of tremendous help to me through it all to the final day of submitting this work. To all lecturers and senior staff of the Department of Nutrition and Food Science, I say a big thank you for your inputs and suggestions to making this project a success during my series of presentations from proposal to results presentation. I appreciate my siblings, Kwaku Gyasi, Akosua Anokyewaa, Kwabena Owusu and Adwoa Amponsah who have been there and have continually prayed for my success. I appreciate all my friends and well-wishers especially Ms Keziah Ama Darko, Mr. Alex Ekow-Ampong and Angel Ampofo for the love and motivation to help me accomplish this feat. God bless you. I also appreciate the efforts of Rosemond Akosua Nyamedor who assisted me with the distribution of the questionnaires and with the analysis of data. I am and will forever be grateful to my colleagues who have given everything possible and even given up important things to make sure I achieve this feat. Finally, I thank my Senior Pastor, Rev. Richmond Darko for your prayers, words of motivation and words of comfort. God bless you all. Amen. University of Ghana http://ugspace.ug.edu.gh vi TABLE OF CONTENTS DECLARATION........................................................................................................................... ii ABSTRACT .................................................................................................................................. iii DEDICATION.............................................................................................................................. iv ACKNOWLEDGEMENT ............................................................................................................ v TABLE OF CONTENTS ............................................................................................................ vi LIST OF TABLES ........................................................................................................................ x LIST OF FIGURES .................................................................................................................... xii LIST OF ABBREVIATIONS ................................................................................................... xiii CHAPTER ONE ........................................................................................................................... 1 INTRODUCTION......................................................................................................................... 1 1.1 Background ........................................................................................................................... 1 1.2 Rationale for the study .......................................................................................................... 5 1.3 Main Objective ...................................................................................................................... 7 1.3.1 Specific Objectives ......................................................................................................... 7 CHAPTER TWO .......................................................................................................................... 8 LITERATURE REVIEW ............................................................................................................ 8 2.1 Rice and its Benefits .............................................................................................................. 8 2.2 Rice Production in Ghana ..................................................................................................... 9 2.3 Types of Local Rice ............................................................................................................ 11 2.4 Rice consumption in Ghana ................................................................................................ 12 2.5 Heavy Metals....................................................................................................................... 13 2.5.1 Arsenic (As) .................................................................................................................. 13 2.5.2 Lead (Pb) ...................................................................................................................... 16 2.5.3 Cadmium (Cd) .............................................................................................................. 18 University of Ghana http://ugspace.ug.edu.gh vii 2.5.4 Mercury (Hg) ................................................................................................................ 20 2.5.5 Copper (Cu) .................................................................................................................. 21 2.5.6 Zinc (Zn) ....................................................................................................................... 22 2.6 Heavy metals in Rice........................................................................................................... 24 2.7 Risk Assessment .................................................................................................................. 26 CHAPTER THREE .................................................................................................................... 28 MATERIALS AND METHODS ............................................................................................... 28 3.1 Study Design ....................................................................................................................... 28 3.2 Overview of Rice Consumption Survey ............................................................................. 28 3.2.1 Sample Size Determination for Consumer Survey ....................................................... 29 3.2.2 Ethical approval ............................................................................................................ 29 3.3.1 Sampling of Rice for Estimation of Heavy Metal content ........................................... 29 3.3.2 Estimation of Heavy Metals in Rice Samples .............................................................. 30 3.3.2.1 Reagents and Chemicals ....................................................................................... 30 3.3.2.2 Sample Pre-treatment ............................................................................................ 30 3.3.2.3 Digestion Procedure .............................................................................................. 30 3.3.2.4 Equipment for Heavy Metal Analysis................................................................... 31 3.3.2.5 Quality Control and Assurance ............................................................................. 31 3.4 Exposure Risk Assessment ................................................................................................. 32 3.5 Data Analysis ...................................................................................................................... 33 CHAPTER FOUR ....................................................................................................................... 34 RESULTS AND DISCUSSION ................................................................................................. 34 4.1 Local Rice Varieties ............................................................................................................ 34 4.2 Survey on Local Rice Consumption.................................................................................... 34 University of Ghana http://ugspace.ug.edu.gh viii 4.2.1 Gender Distribution of Respondents ............................................................................ 35 4.2.2 Age Group of Respondents ........................................................................................... 36 4.2.3 Body Weight of Respondents ....................................................................................... 37 4.2.4 Educational Level of Respondents ............................................................................... 38 4.2.5 Occupation of Respondents .......................................................................................... 39 4.2.6 Reasons for the Consumption of Local Rice ................................................................ 40 4.2.7 Place of Purchase for Local Rice .................................................................................. 41 4.2.8 Local Rice Consumption by Respondents .................................................................... 42 4.2.9 Frequency and Quantity of Local Rice consumption for Adults ................................. 43 4.2.10 Consumption of Local rice by Children ..................................................................... 44 4.2.10.1 Respondents whose households had children who consume Local Rice ........... 44 4.2.10.2 Age group distribution of children in respondents’ households ......................... 45 4.2.10.3 Body weight of children who consume Local Rice ............................................ 46 4.2.10.4 Local Rice Consumption pattern of Children ..................................................... 47 4.2.10.5 Quantity and Frequency of Local Rice Consumption by children ..................... 48 4.3.1 Heavy Metals Analysis of Local Rice Samples ............................................................ 50 4.3.2 Arsenic (As) .................................................................................................................. 50 4.3.3 Lead (Pb) ...................................................................................................................... 53 4.3.4 Cadmium (Cd) .............................................................................................................. 55 4.3.5 Mercury (Hg) ................................................................................................................ 57 4.3.6 Copper (Cu) .................................................................................................................. 59 4.3.7 Zinc (Zn) ....................................................................................................................... 61 4.4 Exposure to Heavy Metals from Consumption of Local Rice ............................................ 64 4.5.1 Non-carcinogenic Risk Assessment (Hazard Quotient) ............................................... 69 University of Ghana http://ugspace.ug.edu.gh ix 4.5.2 Carcinogenic Risk Assessment ..................................................................................... 72 CHAPTER FIVE ........................................................................................................................ 76 CONCLUSION AND RECOMMENDATION ........................................................................ 76 5.1 Conclusion ........................................................................................................................... 76 5.2 Recommendations ............................................................................................................... 77 REFERENCES ............................................................................................................................ 78 APPENDIX ................................................................................................................................ 107 APPENDIX I ........................................................................................................................... 107 APPENDIX II ......................................................................................................................... 114 APPENDIX III ........................................................................................................................ 120 APPENDIX IV ........................................................................................................................ 122 University of Ghana http://ugspace.ug.edu.gh x LIST OF TABLES Table 1 Educational Level of Respondents .................................................................................. 38 Table 2 Place of Purchase for Local Rice ..................................................................................... 41 Table 3 Quantity and Frequency of Local Rice Consumption for Adults .................................... 43 Table 4 Quantity and Frequency of Local Rice Consumption by Children ................................. 48 Table 5 Average (age group, weight, and quantity of rice consumed) by children and adults ..... 49 Table 6 Arsenic (As) content of local rice samples ...................................................................... 52 Table 7 Arsenic (As) Content of foreign rice samples ................................................................. 52 Table 8 Lead (Pb) content of local rice samples ........................................................................... 54 Table 9 Lead (Pb) Content of foreign rice samples ...................................................................... 54 Table 10 Cadmium (Cd) content of local rice samples ................................................................. 56 Table 11 Cadmium (Cd) Content of foreign rice samples ............................................................ 56 Table 12 Mercury (Hg) content of local rice samples .................................................................. 58 Table 13 Mercury (Hg) Content of foreign rice samples .............................................................. 58 Table 14 Copper (Cu) content of local rice samples..................................................................... 60 Table 15 Copper (Cu) Content of foreign rice samples ................................................................ 61 Table 16 Zinc (Zn) content of local rice samples ......................................................................... 63 Table 17 Zinc (Zn) Content of foreign rice samples ..................................................................... 63 Table 18 Estimated Daily Intake (EDI) of local rice for adults .................................................... 65 Table 19 Estimated Daily Intake (EDI) of local rice for Children ............................................... 66 Table 20 Estimated Weekly Intake (EWI) of local rice for Adults .............................................. 67 Table 21 Estimated Weekly Intake (EWI) of local rice for Children ........................................... 68 Table 22 Hazard Quotient (HQ) in Adults .................................................................................... 71 University of Ghana http://ugspace.ug.edu.gh xi Table 23 Hazard Quotient (HQ) in Children ................................................................................ 72 Table 24 Cancer Risk (CR) in Adults ........................................................................................... 74 Table 25 Cancer Risk (CR) in Children ........................................................................................ 75 University of Ghana http://ugspace.ug.edu.gh xii LIST OF FIGURES Figure 1 Gender Distribution of Respondents .............................................................................. 35 Figure 2 Age Groups of Respondents (in years) ........................................................................... 36 Figure 3 Body Weight (Kg) of Respondents ................................................................................ 37 Figure 4 Occupation of Respondents ............................................................................................ 39 Figure 5 Reasons for Consuming Local Rice ............................................................................... 40 Figure 6 Local Rice Consumption Pattern of Respondents .......................................................... 42 Figure 7 Respondents whose households had children who consume local rice .......................... 44 Figure 8 Age Group Distribution of Children Who Consume Local Rice ................................... 45 Figure 9 Body Weight of Children who Consume Local Rice ..................................................... 46 Figure 10 Local Rice Consumption Pattern of Children .............................................................. 47 University of Ghana http://ugspace.ug.edu.gh xiii LIST OF ABBREVIATIONS AB Ashanti Brown As Arsenic ANOVA Analysis of Variance AW Ashanti White Cd Cadmium CR Cancer Risk CRM Certified Reference Material Cu Copper DHHS Department of Health and Human Services DNA Deoxyribonucleic Acid EDI Estimated daily intake EFSA European Food Safety Authority EPA Environmental Protection Agency EU European Union EWI Estimated weekly intake FAO Food and Agriculture Organization FAPAS Food Analysis Performance Assessment University of Ghana http://ugspace.ug.edu.gh xiv HI Hazard Index IARC International Agency for Research on Cancer iAs Inorganic Arsenic ICP-MS Inductive Coupled Plasma Mass Spectrophotometer IPC Infection prevention and control LDL Low-density lipoprotein HDL High-density lipoprotein Hg Mercury NB Northern Brown NW Northern White MoFA Ministry of Food and Agriculture MT Megatonne Pb Lead pH power of hydrogen PTFE Polytetrafluoroethylene PTWI Permitted tolerable weekly intake RDA Recommended Daily Allowance RfD Reference dose University of Ghana http://ugspace.ug.edu.gh xv RNA Ribonucleic Acid. USDA United States Department of Agriculture US FDA United States Food and Drugs Authority VB Volta Brown VW Volta White WHO World Health Organization Zn Zinc University of Ghana http://ugspace.ug.edu.gh 1 CHAPTER ONE INTRODUCTION 1.1 Background Rice is a commonly consumed staple meal that makes up a sizable percentage of the diets of more than half of the world's population. (Danso-Abbeam et al., 2014; Nurshad, 2019). In the last 30 years, the global rice consumption climbed by 40%. (Anang et al., 2011). Rice, Ghana's main staple meal, is the second-most significant cereal after corn (MoFA, 2020; USDA, 2018). For both city and rural consumers, it provides a convenient food (Anang et al., 2011; Tomlins et al., 2003). Ghana has experienced a significant change in rice consumption patterns and levels (MoFA, 2020). Due to its comparatively easy preparation and delectable recipes, its consumption has expanded in the nation along with population expansion, and it is quickly becoming a major component of the diet in many Ghanaian families (Anang et al., 2011; Armah & Aboagye, 2020; USDA, 2018). Urbanization, expatriate community, entrepreneurial middle class, tourism sector, and an increase in women working outside the home are boosting its demand (Armah & Aboagye, 2020; USDA, 2018). In recent years, there has been concerns about heavy metal contamination of rice crops (Gomah et al., 2019) and this led to several countries prioritizing the implementation of food safety practices (Salem, 2021). However, exposure to heavy metals continue to pose a significant threat to food safety (Naujokas et al., 2013a). Heavy metals are defined by Holleman & Wiberg Nils (1985) as metals with specific weights greater than 5 gcm-3 or, as stated by Ferguson (1990), as metallic elements with a comparatively high density in contrast to water. Heavy metals with negative health consequences when exposure University of Ghana http://ugspace.ug.edu.gh 2 is not minimized include arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu), and zinc (Zn) (Duffus, 2001). Most plant and animal tissues may accumulate heavy metals, which have extended half-lives and are deadly when they do. (Otitoju et al., 2014). The presence of heavy metals in the soil might be due to natural occurrences or anthropogenic activity (such as mining, extraction, careless rubbish disposal, and various agricultural practices) (Otitoju et al., 2014; Teymori et al., 2014). In the course of mining, for instance, heavy metals may occasionally be released into the environment and transported by air and water to other areas (Engwa et al., 2019). Plant death has been seen when heavy metal concentrations are high (Carolyn & Aqilah, 2014). Arsenic (As) is abundant in the environment, occurs everywhere, and can easily infiltrate the food chain or food supply through tainted soil, water, or air (Nguyen et al., 2019a; US FDA, 2020). Its risks are well established, and it affects humans in a variety of ways (Liao et al., 2018). According to reports, arsenic exposure may affect more people than previously thought and contribute to a greater number of chronic diseases (Naujokas et al., 2013a). Although lead (Pb) is a naturally occurring chemical, human activities like mining and manufacture have the potential to introduce it into the environment (Tchounwou et al., 2012a). It is extremely dangerous and carcinogenic by the Environmental Protection Agency (Jaishankar et al., 2014; EPA, 1988). According to Papanikolaou et al., 2005, lead poisoning in humans has the most negative effects on the hemopoietic, neurological, reproductive, and urinary tract systems. Acute exposure might result in nausea, vomiting, headaches, hypertension, stomach pain, renal failure, lethargy, sleeplessness, arthritis, hallucinations, and vertigo (Jaishankar et al., 2014). University of Ghana http://ugspace.ug.edu.gh 3 Industrial activities and cadmium smelters release cadmium into sewage sludge, fertilizers, and groundwater, where it can stay in soils and sediments for decades before being absorbed by plants (Unaegbu et al., 2016). The primary source of exposure to cadmium is certain crops, such as rice, which can accumulate significant levels of the metal if cultivated in cadmium-contaminated soil (WHO, 2019). Cadmium and its compounds can lead to cancer in humans, according to the International Agency for Research on Cancer (IARC), which made this claim in 1993. People exposed to cadmium have an increased risk of developing leukaemia, high blood pressure, osteoporosis, renal illness, urinary bladder, pancreatic, breast, and prostate cancers (Satoh et al., 2002). As a bio accumulative substance, mercury is exceedingly hazardous (Jaishankar et al., 2014). Mercury contamination is mostly caused by human activities like agriculture, municipal and industrial wastewater discharges, mining, and cremation (Chen, 2012). Intestinal issues, acrodynia disorders, and harm to the brain and central nervous system have all been connected to mercury (Gomah et al., 2019). In addition, it can accumulate in the thyroid, raising the risk of autoimmune diseases and resulting in contact dermatitis (Gallagher et al., 2012; Caravati et al., 2008). An essential micronutrient needed for biological activity is copper (Cu) (Harvey & Mcardle, 2008; Tchounwou et al., 2008). Clinical signs of a deficit, such as anemia, hypercholesterolemia, and skeletal abnormalities, demonstrate that it is essential for humans (Harvey & Mcardle, 2008). Despite this, high copper exposure has been linked to cell damage in humans, leading to Wilson disease (Tchounwou et al., 2008). Additionally, a surplus of such metals damages cells and tissues, which has several negative effects and causes human diseases. According to Tchounwou et al., there is relatively little difference in copper content between beneficial and detrimental effects (2008). University of Ghana http://ugspace.ug.edu.gh 4 Zinc is a necessary heavy metal in the human body, and its homeostasis reflects a balance between dietary zinc absorption and zinc loss from the body (Kumar Sharma & Agrawal, 2004; Wuana & Okieimen, 2011). Zinc is essential for the proper functioning of many organ systems, as well as for growth, development, and tissue repair (Codex Alimentarius Commission, 2016). Excessive zinc exposure, on the other hand, can be harmful and have pathological consequences (Naseri et al., 2015a). Acute zinc toxicity in humans can result in vomiting, dehydration, sleepiness, lethargy, electrolyte imbalance, abdominal discomfort, nausea, poor motor coordination, and renal failure (Kumar Sharma & Agrawal, 2004). An excessive intake of zinc over time boosts the risk of anemia, pancreatic damage, low-density lipoprotein (LDL) cholesterol elevation, and worsening Alzheimer's disease symptoms (Athar & Vohora, 1995). Heavy metals cannot be completely eliminated from the environment or food supply because they are naturally occurring substances (US FDA, 2020). To the greatest extent possible, however, consumer exposure to heavy metals can be reduced (US FDA, 2020). A group of experts on food chain contamination advocated reducing dietary exposure to toxins including arsenic (EFSA, 2009). As a result, limitations for certain heavy metals in various food products have been established by Codex and the European Commission (Codex Alimentarius Commission, 2016; EFSA, 2009). University of Ghana http://ugspace.ug.edu.gh 5 1.2 Rationale for the study Over the past 10 years, the consumption of rice has increased significantly as a huge portion of consumers switched from other staples to rice. (Nurshad, 2019; Tomlins et al., 2003) Rice consumption per capita increased from 24 kg in 2012/2013 to 35 kg in 2016/2017 (GSS, 2018). Also, rice expenditure per capita increased from 3.3 times that of maize in 2012/2013 to 4.1 times in 2016/2017 (Ragasa et al., 2020). This continuous increase in rice consumption is because of factors such as change in consumer habits, population growth, urbanization and increase in consumers’ wealth (Anang et al., 2011; MoFA, 2020). Consumers in urban areas account for 70% of national consumption (MoFA, 2020). Ghana's domestic rice production reached 450,000 MT in 2017/2018, up from 390,000 MT in 2016/2017 owing to excellent weather circumstances and other major production factors (MoFA, 2020; USDA, 2018). A factor that has revamped domestic rice production in Ghana is the government’s commitment to boost rice output by setting expansion targets through the introducing of new high yielding and disease resistant rice cultivars, and the use of low-cost water management measures (USDA, 2018; (MoFA, 2020). In addition, was the establishment of the Ghana Rice Inter-Professional Body (GRIB) as one of the efforts by the government to revamp the local rice industry (Diako et al., 2010). Moreover, production and consumption of local rice is growing in popularity in Ghana for various reasons, including affordability and a countrywide goal of increasing local production to strengthen the economy. (Danso-Abbeam et al., 2014). Additionally, some rice farms are located near mining operations, which causes the soil and water used to irrigate rice fields to also absorb the mine's effluent, which is contaminated with several heavy metals. For instance, the MoFA reports that between 2020 and 2021, the Central Region's rice output grew dramatically (from 12,308 metric tonnes to 16,246 metric tonnes). The districts University of Ghana http://ugspace.ug.edu.gh 6 that produce most of the region's rice are Gomoa East, Assin Central, Assin North, Assin South, and Twiffo Attimorkwa (MoFA, 2022). The Pra river, a significant body of water utilized for irrigation in this region, has over time been extensively poisoned with heavy metals because of unlawful mining. Also, using too many pesticides raises the concentrations of several heavy metals in the soil and groundwater (Kalita et al., 2018; Teymori et al., 2014). Rice contamination by heavy metals endangers consumers, therefore there is the need to ensure its safety (Naseri et al., 2015). Most heavy metals, including cadmium, lead, and arsenic, have been identified as carcinogenic (Cubadda et al., 2003; EPA, 1988; IARC, 2012), with effects on the liver, kidneys, bladder, lungs, bones, and central nervous system (Teymori et al., 2014). Given the huge demand for rice, precautions must be taken to guarantee the public's health is safeguarded. This study's goal was to determine how much local rice sold in Accra Metropolis exposes consumers to certain heavy metals, including arsenic, lead, cadmium, mercury, copper, and zinc. University of Ghana http://ugspace.ug.edu.gh 7 1.3 Main Objective The primary goal of this study was to evaluate the risk of exposure to various heavy metals (Arsenic, Lead, Cadmium, Mercury, Copper, and Zinc) in locally produced rice sold in the Accra Metropolitan Area. 1.3.1 Specific Objectives i. Determine extent of local rice consumption by consumers in Accra Metropolis. ii. Determine the concentrations of Arsenic, Lead, Cadmium, Mercury, Copper, and Zinc in local rice sold at markets in Accra Metropolis. iii. Assess risk of exposure to Arsenic, Lead, Cadmium, Mercury, Copper, and Zinc from the consumption of local rice sold in Accra Metropolis. University of Ghana http://ugspace.ug.edu.gh 8 CHAPTER TWO LITERATURE REVIEW 2.1 Rice and its Benefits The Gramineae family (Poaceae) of grass plants includes rice (Tripathi et al., 2011). Other grains like maize, sorghum, and millet as well as tubers and roots like potatoes, yams, and cassava have long held sway in regions of the world where rice has gained popularity (Danabal et al., 2021). Rice is the main food consumed by most people in underdeveloped nations (Roy et al., 2013). For example, it has been stated that Africa has experienced the greatest rise in rice consumption during the past few decades (Danabal et al., 2021). Since the beginning of civilization, rice has provided life-sustaining nourishment throughout the humid regions of Asia and, to a lesser extent, West Africa (Roy et al., 2013). Rice (Oryza sativa) is among the species of cultivated rice which originated from Asia (O. rufipogon, and O. glaberrima) but originally it originated from Africa (O. barthii) (Cordero-Lara, 2020). Rice is categorised according to its form (Dzudzor, 2013). Rough rice, also known as paddy rice, refers to rice that has not been processed and hence retains the hull and bran layer (Dzudzor, 2013). Brown rice is rice that has had the hull removed but still has the bran layer adhering to it (Dzudzor, 2013). The term "milled rice" refers to rice that has had the hull and bran coating removed (Dzudzor, 2013). The grain becomes refined as the degree of milling increases as the bran layer is eliminated further (Dzudzor, 2013). Rice can be classified as polished or unpolished depending on the degree of milling. The sensory qualities of milled rice are superior, but it has fewer vitamins, minerals, fats, and fiber (Abbas et al., 2017). Rice is a good source of calories and protein, and it also has a lot of zinc and niacin (FAO, 2006) which are all essential for body development. Rice is an important grain as it accounts for more University of Ghana http://ugspace.ug.edu.gh 9 than one-fifth of all calories consumed by humans globally (Pateriya et al., 2021). Rice's protein quality (66%) is only slightly lower than that of oats (68%) but higher than that of whole wheat (53%) and corn (49 %) (Roy et al., 2013). Among the cereals, rice is without a doubt the most energy-dense (Roy et al., 2013). In other words, rice crops produce more food energy per hectare than wheat and maize, based on mean grain yield (Roy et al., 2013). Rice, which is low in sodium and fat and cholesterol-free, helps to keep blood pressure in check (Roy et al., 2013). Rice contributes significantly to agricultural GDP (Gross Domestic Product) of the Ghanaian economy (Suleman & Sarpong, 2012). Rice is used to make infant foods, snack foods, breakfast cereals, beer, fermented products, and rice bran oil in the industrial world (Roy et al., 2013). However, rice has been shown to accumulate more metals than other cereal grains (Williams et al., 2007). 2.2 Rice Production in Ghana A variety of habitats, including irrigated, rainfed lowland, deep water, upland, and tidal wetlands, are suitable for the growth of rice (International Rice Research Institute, 1984). When compared to other crops, rice crops require at least two to three times as much water as other cereals (Kumar Pandey et al., 2015). Conventional rice cultivation methods (transplanted rice) require typically 2500 liters of water to produce 1 kilogram of rough rice (Bouman et al., 2007). In Ghana, rice is one of the most important cereals grown in terms of agricultural land because it makes up roughly 19 percent of the country's grain production (Danso-Abbeam et al., 2014). Rice is grown across all sixteen regions of Ghana, including the interior Savannah zone, the high rain forest zone, the semi-deciduous rain forest zone, and the coastal Savannah zone, in all the key biological and climatic zones (Amanor-Boadu, 2012; Oteng, 2020). Nearly 80% of the country's University of Ghana http://ugspace.ug.edu.gh 10 total rice production and 73% of its total production area in 2010 were produced in Ghana's Northern, Upper East, and Volta regions, which are also its most populous (Asravor et al., 2019; Danso-Abbeam et al., 2014; Donkoh & Awuni, 2011). Rice is typically planted once a year, however, in rare cases where irrigation is available, producers may plant two crops per year. Planting takes place in July/August in the Northern and Upper East, while harvest takes place in October/November (USDA, 2018). Governments in Ghana have reportedly made numerous attempts throughout the years to boost domestic rice output, according to Donkoh et al. (2012). One instance is the implementation of numerous irrigation projects, including the Vea, Afife, Kpong, Tanoso, Ashaiman, Tono, Dawhenya, Weija, Bontanga, and Aveyime. The government has also implemented efforts to increase rice output because of worries expressed by the Coalition for African Rice Development (CARD) about tripling rice production in Sub-Saharan African nations in ten years (Suleman & Sarpong, 2012). As a result, the country set a goal of becoming West Africa's leading rice producer by 2015 (Suleman & Sarpong, 2012). This led to the establishment of the Fievie Rice Projects in the country's Volta Region (Suleman & Sarpong, 2012). Ghana's domestic rice production for MY2020/21 was expected to be 500,000 MT, an increase of about 6% from the MY2019/20 estimate of 470,000MT (USDA, 2020). This shows strong growth in the domestic rice sector and the continuation of Ghana's recent upward production trajectory (USDA, 2020). However, it has been reported that commercial growers use a lot of pesticides (Anang & Amikuzuno, 2015). Some of these pesticides contain heavy metals (Kalita et al., 2018). Due to the use of arsenic-contaminated water for irrigation and the many processes that result in its mobilization, which affect the agricultural system and cause crop plant uptake of the element, levels of heavy metals like arsenic have increased in soils (Kalita et al., 2018). According to Xu et University of Ghana http://ugspace.ug.edu.gh 11 al. (2008), rice has a greater translocation factor (TF) for metals such As (0.8) than other cereals like wheat (0.1) and barley (0.2). 2.3 Types of Local Rice Branded and unbranded local rice are the two categories that make up the market for local rice (Spring Agro Industries Limited, 2021). Large-scale domestic farmers and processors frequently supply branded types, which are usually premium fragrant long grain varieties (Spring Agro Industries Limited, 2021). Most supermarkets and shopping malls sell locally produced rice under brand names (Ayeduvor, 2018). Some branded domestic types are now almost as popular as foreign ones (Spring Agro Industries Limited, 2021). Most of the unbranded local rice sold by vendors at traditional open markets is obtained from the country's primary rice-producing regions in the Eastern and Northern Regions of Ghana (Ayeduvor, 2018; Spring Agro Industries Limited, 2021). According to Ayeduvor's (2018) market research, most rice vendors in urban traditional open marketplaces sell their product by the bowl and the sack. Most of the time, the producing area is used to identify rice types in local markets (Ayeduvor, 2018). However, nothing is known about the native rice types that are marketed in the market (Ayeduvor, 2018). Tamale brown rice, Tamale white rice, Tamale agra rice, Hohoe brown rice, Hohoe white rice, Kumasi brown rice and Kumasi white rice (Kpong) are the types of local rice reported in the literature (Ayeduvor, 2018). Much of the local rice sold at markets in Accra come from the Volta Region (Hohoe area) and Tamale in the Northern Region (Ayeduvor, 2018). University of Ghana http://ugspace.ug.edu.gh 12 2.4 Rice consumption in Ghana Rice consumption patterns and levels in Ghana have rapidly changed especially among city dwellers who constitute about 70% of the national consumption (Ayeduvor, 2018; Donkoh et al., 2012; MoFA, 2020). Because of this, rice has become Ghana's most important cereal food crop after maize (Amanor-Boadu, 2012; Ayeduvor, 2018). MY2020/21 consumption is expected to be 1.42 million MT, up 1% from Post's MY 2019/20 estimate of 1.4 million MT (USDA, 2020). Rice consumption in Ghana has increased in tandem with population growth, and rice is increasingly becoming a staple in many Ghanaian households due to its ease of preservation and preparation as well as palatable recipes (Ayeduvor, 2018; Ragasa et al., 2020; USDA, 2020). Rising urbanization, a burgeoning expat population, a middle-class that is entrepreneurial, a quickly increasing tourism industry, and an increase in households where both couples work outside the home are all factors that are causing the demand for rice to increase (MoFA, 2020; USDA, 2020). The features of rice that impact cooking, such as cooking time, water absorption ratio, elongation ratio, swelling capacity, and amylose content, have also raised demand for rice (Ayeduvor, 2018). The growth of eateries and fast-food joints in significant cities and towns has also increased demand for rice (Donkoh & Awuni, 2011; MoFA, 2020; USDA, 2020). With Ghana's population presently projected by the Ghana Statistical Service to reach above 30 million in 2020, rice consumption is predicted to increase proportionately. Per capita consumption of rice is now estimated to be approximately 48 kg per year (USDA, 2020). University of Ghana http://ugspace.ug.edu.gh 13 2.5 Heavy Metals Heavy metals are naturally occurring substances with large atomic weights and densities at least five times that of water (Tchounwou et al., 2012b). Since they are present in a variety of environmental matrices in concentrations ranging from parts per billion to less than 10 parts per million, heavy metals are sometimes referred to as trace elements (Kabata-Pendias, 2000). They are widely dispersed throughout the environment because of numerous industrial, domestic, agricultural, medicinal, and technological uses (Tchounwou et al., 2012b). As a result, questions have been raised about their potential effects on the environment and human health. The dose, route, chemical species, as well as the exposed person's age, gender, heredity, and nutritional condition, all have an impact on the toxicity of these substances (Tchounwou et al., 2012b). Every heavy metal is recognized to have unique physical and chemical features that give rise to certain toxicological modes of action (Tchounwou et al., 2012b). The heavy metals Arsenic, Lead, Cadmium, Mercury, Copper, and Zinc are the subject of this investigation. 2.5.1 Arsenic (As) Arsenic, although possessing properties that make it both a metal and a non-metal, is chemically classified as a metalloid but is most frequently referred to as a metal (ATSDR, 2007; Martinez et al., 2011). It is an abundant element that is present in modest concentrations in almost all environmental matrices (ATSDR, 2007). Metallic arsenic is another name for the solid, steel-gray material known as elemental arsenic (ATSDR, 2007). Despite this, the environment typically contains arsenic, oxygen, chlorine, and sulphur (ATSDR, 2007). The bulk of organic and inorganic arsenic compounds are granules that are colorless or white and do not evaporate (ATSDR, 2007). They often lack a distinct flavor and fragrance (ATSDR, 2007). As a result, figuring out whether arsenic is in food, water, or the air can be difficult (ATSDR, 2007). University of Ghana http://ugspace.ug.edu.gh 14 As a result of arsenic's natural occurrence in the ground, it may enter the air, water, and land through wind-blown dust and can enter bodies of water through runoff and leaching (ATSDR, 2007). Variable amounts of it have been found in the soil, water, fuels, marine life, and air (Smedley & Kinniburgh, 2002). The underlying geology of the area affects arsenic levels, according to a US FDA report from 2020. Furthermore, they appear in volcanic explosions (ATSDR, 2007). Due to pollution from mining, fracking, coal-fired power plants, arsenic-treated timber, and arsenic-containing herbicides, arsenic levels are increased in some places (Tchounwou, Patlolla, et al., 2003; US FDA, 2020). It may do this by evaporating in the rain or by discharging industrial waste into lakes, rivers, and subterranean water sources (ATSDR, 2007). Under reducing circumstances, arsenite predominates, while in oxygen-rich environments, arsenate is the most stable species. Most of the forms of arsenic dissolved in water are inorganic (WHO, 2001). Organo-arsenic species are created by the biotransformation of toxic inorganic arsenic (iAs) molecules, which subsequently enter biosynthetic pathways to create the roughly one hundred chemicals prevalent in nature (Taylor et al., 2017). Since the beginning of time, large ingested doses of inorganic arsenic (above 60,000 ppb in water) have been known to be fatal (ATSDR, 2007). Arsenic's solubility and oxidation state, as well as several other inherent and extrinsic characteristics, all have a significant impact on how dangerous it is (Centeno et al., 2005). Arsenic toxicity is regulated by the dosage, frequency, and duration of exposure, the biological species, age, and gender, in addition to personal susceptibilities, genetics, and dietary variables (Abernathy et al., 1999). Numerous cases of human arsenic poisoning have been linked to exposure to inorganic arsenic (Tchounwou et al., 2012b). Inorganic arsenic (iAs) is related with an increased risk of long-term health problems (EFSA, 2009). When consumed, small amounts of inorganic arsenic (between 300 and 30,000 parts per billion in water) may irritate the stomach and intestines, University of Ghana http://ugspace.ug.edu.gh 15 causing symptoms including nausea, vomiting, and diarrhoea (ATSDR, 2007). Ingestion of inorganic arsenic also causes blood vessel damage, which can result in bruising, an irregular heartbeat, decreased production of red and white blood cells, which can lead to weariness, and poor nerve activity, which can result in "pins and needles" feelings in the hands and feet (ATSDR, 2007). Inorganic arsenic compounds can damage many organs even when taken in small amounts over time (Al-Saleh et al., 2017). The most noticeable side effect of long-term oral exposure to inorganic arsenic is probably a pattern of skin problems (ATSDR, 2007; Chung et al., 2014; Hughes et al., 2011; Naujokas et al., 2013b; Steinmaus et al., 2013; US FDA, 2020). Some of them include blotches of darker skin and the development of tiny "corns" or "warts" on the palms, soles, and chest. These changes are typically accompanied by adjustments to the skin's blood vessels (ATSDR, 2007). Skin cancer is another possibility (ATSDR, 2007; Steinmaus et al., 2013; Zaldivar, 1974). It has also been demonstrated that long-term inorganic arsenic exposure has an impact on the vascular system (ATSDR, 2007). Blackfoot Disease, which causes a gradual loss of circulation in the hands and feet and finally results in necrosis and gangrene, is the most striking of these consequences (ATSDR, 2007). Recent research shows that exposure to inorganic arsenic is more hazardous and can have detrimental effects on health than exposure to organic arsenic (US FDA, 2020). Arsenic in drinking water is known to induce lung cancer, and long-term oral exposure to the substance results in the development of respiratory malignancies (ATSDR, 2007). Human carcinogenicity is assigned to inorganic arsenic. For instance, the United States Department of Health and Human Services (DHHS) classifies inorganic arsenic as a human carcinogen (ATSDR, 2007). University of Ghana http://ugspace.ug.edu.gh 16 The International Agency for Research on Cancer (IARC) classified arsenic as a Group 1 carcinogen since there is enough evidence to connect its exposure to humans with cancer (IARC, 2012). Inorganic arsenic is a human carcinogen through oral and inhalation routes, according to the Environmental Protection Agency (EPA), which has assigned it to cancer classification Group A. (ATSDR, 2007). The underlying molecular processes of arsenic's well-known negative impacts on health remain poorly understood (Martinez et al., 2011). Little is known about the carcinogenicity of arsenic at levels that raise risks for immunological problems, cancer (Gilbert- Diamond et al., 2013; Tchounwou, Patlolla, et al., 2003), diabetes (Navas-Acien et al., 2005; Sung et al., 2015), ischemic heart disease, and peripheral vascular disease (Abhyankar et al., 2016). Eating inorganic arsenic is therefore harmful at all quantities, even if it cannot be avoided. 2.5.2 Lead (Pb) In tiny proportions, lead is an element that naturally occurs in the earth's crust (EPA, 2022; Tchounwou et al., 2012b). Because of human activities including the burning of fossil fuels, mining, and manufacturing, lead and lead compounds can be found in the air, soil, and water (Martin & Griswold, 2009; Tchounwou et al., 2012b). Since lead looks like calcium, the majority of it is absorbed and deposited in children's and adults' bones, where it can stay for decades (Adeti, 2015). Despite the fact that lead may take on many different chemical forms, it does not break down in the environment. Lead-containing particles can move via the air, water, and soil (ATSDR, 2020). The major source of lead in soils that are not affected by other nearby non-air sources (such as dust from degrading leaded paint) is often atmospheric deposition (ATSDR, 2020). Lead is continually transferred between the air, water, and soil via natural physical and chemical processes like University of Ghana http://ugspace.ug.edu.gh 17 weathering, runoff, precipitation, dry deposition of dust, and stream/river movement (ATSDR, 2020). But it appears that soil and sediments are significant Lead sinks (ATSDR, 2020). Most soils strongly absorb lead, which reduces the rate of leaching. The pH and composition of the soil are the primary determinants of Lead solubility, mobility, and phytoavailability in that environment (ATSDR, 2020). Reducing conditions and high chloride concentration are some factors that exacerbate Lead mobility in soil (ATSDR, 2020). Nearly all the body's organs and systems might be harmed by lead (EPA, 2022). It is hazardous to people and animals and causes health issues because it is not required by the human body in any quantity (ATSDR, 2020). (EPA, 2022). Since more than 2,000 years ago, lead's toxicity to humans has been known and is not in question (ATSDR, 2020). Lead poisoning is one of the most often observed accidental hazardous heavy metal exposures in kids and the main factor in single-metal toxicity in kids (Bronstein et al., 2011). Due to its ability to prevent or mimic the actions of calcium and interact with proteins, lead is one of the main factors that contribute to poisoning (ATSDR, 2020). Numerous ways exist through which lead binds to biological molecules, reducing their capacity to function (Tchounwou et al., 2012b). An enzyme's structure changes, and its activity decreases when lead binds to the sulfhydryl and amide groups (Tchounwou et al., 2012b). Lead can also compete with important metallic cations for binding sites, affecting the activity of enzymes or how important cations like calcium are transported (Flora et al.,2007). Reactive oxygen species (ROS) are produced as a result of lead ingestion, which destroys cells (Hermes- Lima et al., 1991). The International Agency for Research on Cancer (IARC) has classified lead as potentially human carcinogenic due to a large body of data in animals and insufficient evidence in humans (IARC, 2014). (ATSDR, 2020). University of Ghana http://ugspace.ug.edu.gh 18 2.5.3 Cadmium (Cd) Cadmium is a highly poisonous metal (Martin & Griswold, 2009). This element becomes toxic over time because of its accumulation (Gomah et al., 2019). It is a by-product of zinc and lead mining and smelting (Jaishankar et al., 2014). Cadmium is also obtained from used batteries (Faroon et al., 2013). It is found in soils and rocks, as well as coal and mineral fertilizers (Jaishankar et al., 2014; Martin & Griswold, 2009; Tchounwou et al., 2012b). Pure cadmium is a delicate, silver-white metal (Faroon et al., 2013). Cadmium sulphate and chloride are soluble in water (Faroon et al., 2013). Cadmium's harmful effects are widely established (Ogabiela et al., 2011). If inhaled or ingested, cadmium can be fatal since it is a risky digestive and lung irritant (Tchounwou et al., 2012b). Symptoms such as nausea, stomach discomfort, burning feeling, vomiting, salivation, muscle cramps, vertigo, shock, loss of consciousness, and convulsions may emerge 15 to 30 minutes after acute consumption (Baselt, 2020). Acute cadmium poisoning can also cause gastrointestinal tract erosion, lung, hepatic, or renal dysfunction depending on the route of poisoning (Baselt, 2020). Although the specific mechanisms of cadmium toxicity are unknown, it has been hypothesized that cadmium toxicity primarily damages cells by producing reactive oxygen species (ROS), which causes single-strand DNA damage and prevents the production of nucleic acids and proteins (Mitra, 1984; Stohs & Bagchi, 1995). When compared to other metals that cause cancer, cadmium is a weak mutagen (J. B. Smith et al., 1989). Studies (Dally & Hartwig, 1997; Suszkiw et al., 1984; Thévenod & Jones, 1992) have shown that cadmium interferes with signal transduction pathways by forming inositol polyphosphate, increasing the concentration of free calcium in the cytoplasm of several cell types, and blocking calcium channels. At lower concentrations (1-100 M), cadmium binds to proteins, inhibits DNA University of Ghana http://ugspace.ug.edu.gh 19 repair, promotes protein degradation, up-regulates the expression of cytokines and proto- oncogenes like c-fos, c-jun, and c-myc, and induces the expression of numerous genes, including metallothioneins, heme oxygenases, glutathione transferases, heat-shock proteins, acute-phase proteins (Tchounwou et al., 2012b). According to the United States National Toxicology Program and the International Agency for Research on Cancer, there is enough evidence to conclude that cadmium is a human carcinogen (Tchounwou et al., 2012b). It is believed that occupational exposure to cadmium increases the risk of developing lung cancer, and there is substantial evidence from rodent studies that the pulmonary system is a target organ for this designation as a human carcinogen (Tchounwou et al., 2012b). As a result, cadmium-induced human carcinogenesis is most clearly established in the lung (Tchounwou et al., 2012b). Animal cadmium carcinogenesis in addition to injection sites also affects the adrenals, testes, and hemopoietic system (IARC, 1993). The US Environmental Protection Agency (US EPA) states that children are not anticipated to be negatively impacted by cadmium exposure in drinking water at a concentration of 0.04 mg/L for up to 10 days (Faroon et al., 2013). The US EPA states that exposure to 0.005 mg/L cadmium in drinking water over the course of a lifetime is not anticipated to have any negative consequences (Faroon et al., 2013). According to the American Food and Drug Administration, bottled water may contain no more cadmium than 0.005 mg/L. (Faroon et al., 2013). A legal limit of 5 g/m3 of cadmium in the air, averaged over an 8-hour workday, was established by the Occupational Safety and Health Administration (OSHA) of the United States (Faroon et al., 2013). University of Ghana http://ugspace.ug.edu.gh 20 2.5.4 Mercury (Hg) Mercury is a heavy metal that may be found in the periodic table's transition element series (Tchounwou et al., 2012b). Typically, mercury is recovered as a by-product of mining processing (L. A. Smith et al., 1995). The main source of mercury is the sulphide mineral cinnabar (Evanko & Dzombak, 1997). The three main forms of mercury are metallic elements, inorganic salts, and organic molecules, each of which has a different level of toxicity and bioavailability (Jaishankar et al., 2014) Mercury is frequently found in the forms of mercuric (Hg2+), mercurious (Hg2 2+), elemental (Hgo), or alkylated (methyl/ethyl mercury) compounds after being discharged into the environment (Evanko & Dzombak, 1997). The organic component of mercury found in the environment that is most frequently encountered is methylmercury (Dopp et al., 2004). Microorganisms in soil and water methylate inorganic (mercuric) forms of mercury to produce it (Dopp et al., 2004). The manufacturing of chloralkali, the burning of garbage, and other industrial processes all release some elemental mercury into the environment as a result of anthropogenic emissions (FAO/WHO, 2011). Natural occurrences such as volcanoes also release some elemental mercury into the atmosphere (FAO/WHO, 2011). Mercury is the deadliest heavy metal, and there is no recognized physiological function for it in human metabolism (Salonen et al., 1995). The human body lacks any systems for actively excreting mercury (Salonen et al., 1995). Acute heavy metal poisoning is frequently brought on by the toxicity of mercury (Jaishankar et al., 2014). Mercury is a prevalent environmental toxin and pollutant that causes serious changes in human tissues and has a number of detrimental impacts on health (Bhan & Sarkar, 2005; Ogabiela et al., 2011). Mercury may cause damage to any organ, as well as problems with the neurological system, muscles, and kidneys (Jaishankar et al., 2014). Both membrane potential and intracellular calcium University of Ghana http://ugspace.ug.edu.gh 21 homeostasis may be affected (Jaishankar et al., 2014). Mercury vapours can cause bronchitis, asthma, and other acute respiratory illnesses (Jaishankar et al., 2014; Ogabiela et al., 2011). By adhering to selenohydryl and sulfhydryl groups, mercury affects tertiary and quaternary protein structure and changes cellular function, which in turn causes methyl mercury to disturb cellular structure (Jaishankar et al., 2014; Patrick, 2002). 2.5.5 Copper (Cu) It is a naturally occurring reddish metal that is also present in small amounts in air, water, sediment, and rock (ATSDR, 2004). Many plants and animals also contain copper (ATSDR, 2004). The formation of hemoglobin, the metabolism of carbohydrates, the synthesis of catecholamines, and the cross-linking of collagen, elastin, and hair keratin all depend on the nutrient copper, which is essential at low intake levels (Tchounwou et al., 2008). Copper is a crucial element in many catalytic processes due to its capacity to collect or donate electrons (Harvey & Mcardle, 2008). The reduction of molecular oxygen is carried out by enzymes that require copper (Tchounwou et al., 2008). Some examples of these enzymes include monoamine oxidase, ferroxidases, superoxide dismutase, cytochrome C oxidase, and dopamine -monooxygenase (Tchounwou et al., 2008). Cuproenzymes use copper's capacity to cycle between an oxidized state, Cu(II), and a reduced state, Cu(I), in redox reactions (Tchounwou et al., 2008). Despite this, copper has the potential to be dangerous due to the production of superoxide and hydroxyl radicals as a result of transitions between Cu(II) and Cu(I) (Camakaris et al., 1999). Micronutrient copper is important for the development of both plants and animals. It facilitates the human body's ability to produce blood hemoglobin (Wuana & Okieimen, 2011). In plants, it is crucial for water control, disease resistance, and seed production (Wuana & Okieimen, 2011). University of Ghana http://ugspace.ug.edu.gh 22 Although copper is essential, when ingested in excess, copper poisoning can take both acute and long-term forms (ATSDR, 2004; Onakpa et al., 2018). Recently, a 0.9 mg daily (0.013 mg/kg daily) recommended dietary allowance (RDA) was created (Tchounwou, Yedjou, et al., 2003). Mining for copper and other metals, as well as establishments that produce or utilize copper metal or copper compounds, can leak copper into the environment (ATSDR, 2004). Dump sites, home wastewater, the burning of fossil fuels and trash, the manufacture of wood, and the creation of phosphate fertilizer are other ways that copper may enter the environment (ATSDR, 2004). Additionally, it can infiltrate the environment naturally through wind-borne dust, native soils, volcanoes, decomposing plants, forest fires, and sea spray (ATSDR, 2004). Copper is hence widely distributed in the environment (ATSDR, 2004). 2.5.6 Zinc (Zn) In nature, zinc is abundant and contributes 20–200 ppm (by weight) of the Earth's crust (ATSDR, 2005). It does not present in nature as elemental zinc, but rather as zinc oxide or sphalerite (ZnS) (ATSDR, 2005). Zinc is a frequent environmental contaminant that is present in large quantities in the aquatic environment (Ogabiela et al., 2011). Approximately 70 mg per kilogram of crustal rocks contain zinc, which is naturally present in soil although in low proportions (Wuana & Okieimen, 2011). By mining, smelting zinc, lead, and cadmium ores, producing steel, burning coal, and burning trash, zinc is discharged into the environment (ATSDR, 2005). Normally, background ambient air contains 1 g/m3 of zinc (ATSDR, 2005). Zinc levels in surface water are typically 0.05 mg/L, although can occasionally reach 50 mg/L. (ATSDR, 2005). The micronutrient zinc is essential for all living things (Kumar Sharma & Agrawal, 2004). It is a vital nutrient for humans, present in all tissues, and acts as a cofactor for more than 300 enzymes University of Ghana http://ugspace.ug.edu.gh 23 (US EPA, 2005). Animals and humans both need zinc for prenatal and perinatal growth, protein synthesis, and DNA and RNA stabilization (Kumar Sharma & Agrawal, 2004). Several metalloenzymes, including alcohol dehydrogenase, alkaline phosphatase, carbonic anhydrase, leucine aminopeptidase, and superoxide dismutase, need it in order to function properly (ATSDR, 2005). Dermatitis, anorexia, growth retardation, inadequate wound healing, hypogonadism with reduced reproductive potential, compromised immunological function, and restricted cerebral function are only a few of the disorders connected to zinc deficiency (ATSDR, 2005). Additionally, a lack of zinc in mothers has been related to a higher incidence of congenital defects in infants (ATSDR, 2005). Zinc deficiency may also impact other compounds' ability to cause cancer, albeit the effect's direction tends to vary depending on the substance that causes the cancer (ATSDR, 2005). Humans have been found to have a mild toxicity reaction to zinc (Ogabiela et al., 2011). However, prolonged usage of large doses can result in health issues like neutropenia, tiredness, and wooziness (Ogabiela et al., 2011). People typically consume 5.2-16.2 mg of zinc per day from food; assuming a body weight of 70 kg, this equates to 0.07-0.23 mg of zinc per kilogram per day (ATSDR, 2005). For zinc, the daily recommended intake (RDA) for men and women is 11 mg and 8 mg, respectively, or around 0.16 mg/kg/day and 0.13 mg/kg/day (ATSDR, 2005). Women who are pregnant or breastfeeding should follow higher RDAs (12 mg/day) (ATSDR, 2005). The recommended zinc intake for babies is 2-3 mg/day and for children is 5-9 mg/day due to their lower typical body weights (Trumbo et al., 2001). University of Ghana http://ugspace.ug.edu.gh 24 2.6 Heavy metals in Rice One of the main ways that people are exposed to heavy metals is through food (Hasan et al., 2022). Due to their extreme toxicity, arsenic, cadmium, lead, and mercury are some of the priority metals of public health concern (Tchounwou et al., 2012b). These dangerous heavy metals may migrate from polluted soil to rice at a certain rate (Hasan et al., 2022). Heavy metal dispersion into the environment raises concentrations in cultivated soil and water, making the food chain a critical source of toxic metal exposure (Datta et al., 2000). Plant-derived foods can easily absorb heavy metals from soil (Huang et al., 2016). Also, irrigation with metal-contaminated water or wastewater can contribute to soil contamination (Hang et al., 2009). Furthermore, the increasing use of fertilizers, insecticides, or pesticides may be a source of toxic metals such as Arsenic, lead and cadmium agricultural soil and crops (Azmy & Kippler, 2020). The rice plant has been identified as one of the plants that absorb many toxic metals from soil, and it adds to human metal exposure across the globe (Williams et al., 2007b). Metal exposure from rice is affected by several factors, including rice consumption rate, the geography (location rice came from), metal sources (where the rice is grown), soil and irrigation water criteria, and rice variety consumed (Azmy & Kippler, 2020). Because metal exposure varies with rice consumption, the more rice people eat, the more metals they may be exposed to (Al- Rmalli et al., 2012). Additionally, the continuous increase in the use of pesticides and insecticides, as well as the use of more lands, such as mines and industrial lands, to meet the world's ever- increasing demand for rice, increases the risk of metal contamination in rice (Feigin et al., 2012). Even for commercial purposes, people occasionally use food adulterants, such as urea for whitening rice, particularly polished rice, which increases the concentration of Cd in rice and rice products (Hossain et al., 2008).Rice roots have a greater capacity than other crops to absorb toxic University of Ghana http://ugspace.ug.edu.gh 25 metals from soils and water in paddy fields (Huang et al., 2016). Anaerobic soil conditions in paddy fields have been shown to result in increased mobilization of toxic metals, making them more bioavailable to rice (Morekian et al., 2013). Furthermore, soil pH is critical (Azmy & Kippler, 2020). Alkaline soil (high pH) contains less lead and other metals such as copper, posing a lower risk of uptake by plants (Tariq & Rashid, 2013). The greater the area devoid of surface water, the higher the concentration of cadmium in the cultivated grain (Azmy & Kippler, 2020). In various marketplaces, "rice grains" and "rice-based goods" had extraordinarily high average levels of total arsenic, ranging from 0.14 to 0.17 mg/kg and having between 0.1 and 0.4 milligrams of inorganic arsenic per kilogram of dry mass, according to the EFSA review (EFSA, 2009). Uncooked rice contains between 0.1 and 0.4 milligrams of inorganic arsenic per kilogram of dry mass (EFSA, 2009; Hojsak et al., 2015; Williams et al., 2007). Compared to other cereals like wheat and barley, which have levels of arsenic that vary from 0.03 to 0.08 mg/kg, rice has significantly higher arsenic (Williams et al., 2007a). Rice includes varying amounts of arsenic based on its variety, place of production, and method of processing; brown rice has a greater arsenic content than white rice (Meharg & Rahman, 2003). Arsenic levels may also change as food is being prepared, with boiling water suggesting being particularly important. For instance, reducing the quantity of arsenic in rice by boiling it in pure water (Daz et al., 2004). Cereals are the principal food type to expose people to cadmium because of their widespread consumption (FAO/WHO, 2011). The EFSA Panel on Contaminants in the Food Chain proposed a tolerable weekly intake of 2.5 g/kg body weight to ensure adequate protection for all consumers, a level that is nearly 40% lower than the FAO/WHO-approved tolerance level. The provisional tolerable monthly intake of 25 g/kg body weight was established by the Joint Food and Agriculture Organization of the United Nations and the World Health Organization Expert Committee on Food University of Ghana http://ugspace.ug.edu.gh 26 Additives (CTA, 2011). Previous research has shown that rice can accumulate fairly high levels of MeHg (0.174 mg/kg), especially in those regions where mercury mining is active (Ogabiela et al., 2011). These metallic substances are thought to be systemic poisons that, depending on the exposure amount, might cause organ damage (Tchounwou et al., 2012). Therefore, the presence of harmful heavy metals in food crops like rice may have an adverse effect on health (Hasan et al., 2022). 2.7 Risk Assessment A risk assessment process was created in order to figure out or estimate the threat to a certain target organism, system, or (sub)population following exposure to a particular substance. This process considers the intrinsic characteristics of the individual agent of concern as well as the characteristics of the particular target system, and it also involves the identification of concomitant uncertainties. (IPCS, 2004). The risk assessment method comprises four stages: risk identification, dose-response assessment, exposure analysis and risk characterization. The process of assessing hazards begins with identifying potential hazards (IPCS, 2004). The dose is the quantity of the substance consumed by the exposed person (or given to the person) (Sheets, 2018). Biologically effective dose is the amount of the substance that reaches a target site where it would pose a hazard (Sheets, 2018). The third phase of risk assessment is exposure assessment (IPCS, 2004). It is the most significant and vital component of risk assessment since it determines the actual level of human exposure to the food hazardous ingredient (de Oliveira et al., 2021). A wide range of estimations are produced depending on the type of consumer and eating habits, as well as the presence of acute or chronic intake, as each mycotoxin's exposure is defined by its concentration in the food and the amount University of Ghana http://ugspace.ug.edu.gh 27 consumed (de Oliveira et al., 2021). Exposure evaluation measures how exposed an organism, system, or (sub) population is to a drug (and its derivatives) (IPCS, 2004). Concentration, exposure, dosage, and physiologically effective dose make up exposure assessment (Sheets, 2018). The concentration of a material indicates how much of it is present in the immediate area (Sheets, 2018). The material (heavy metals in this case) is typically found in air, water, soil, products, or transport or carrier media; the chemical concentration at the point of contact is the exposure concentration (US EPA, 1992). A time-dependent exposure concentration profile can be used to indicate exposure over a period (US EPA, 1992). Exposure is the term used to describe the degree of human contact with the chemical (Sheets, 2018; US EPA, 1992). Risk characterisation is the process of estimating the chance that known and possible unfavorable effects of an agent would manifest in a particular organism, system, or (sub) population under a given exposure scenario. When possible, it uses both qualitative and quantitative methodologies (IPCS, 2004). Risk characterization is the fourth step in the risk assessment process. To estimate the health hazards associated with heavy metal exposure, both carcinogenic and noncarcinogenic risks to the human body are taken into consideration (Luo & Jia, 2021). The three most typical ways that soil heavy metals enter the human body are by oral consumption, respiratory inhalation, and skin contact (Meza-Montenegro et al., 2012). University of Ghana http://ugspace.ug.edu.gh 28 CHAPTER THREE MATERIALS AND METHODS 3.1 Study Design This study comprised of a consumer survey and laboratory analyses. The survey was conducted to obtain information on consumption patterns (frequency and amount consumed) of locally produced rice and the laboratory analyses was to determine the levels of heavy metals in the various rice samples. 3.2 Overview of Rice Consumption Survey This research was conducted in the Accra Metropolis in the Greater Accra Region. A survey was conducted on local rice consumption. It involved the random selection of participants who were consumers of local rice and live in Accra Metropolis. Vulnerable participants who included infants and children were included but not interacted with directly. Questions involving such group were answered by parents or guardians. Questionnaires were issued in google forms via email and other social media platforms. Hard copies were also made available for participants without access to such online platforms. In all participant were made to sign a consent form before they were allowed to participate in the survey. The questionnaire was in a form of multiple choice and closed-ended questions. Some information gathered included: I. Amount consumed per meal (g/meal). II. Frequency of rice consumption (meals/week). III. Major point of purchase. IV. Personal Information (sex, age, body weight). University of Ghana http://ugspace.ug.edu.gh 29 3.2.1 Sample Size Determination for Consumer Survey The study adopted Cochran (1963) to calculate the sample size. Sample size was determined as: n = 𝑍2𝑝𝑞 𝑒2 = 1.962(0.5)(0.5) 0.052 = 0.9604 0.0025 = 384.16 ≈ 385 Where p is the percentage of people who consume rice, q = (1-p), e is the margin of error, and n is the projected minimum sample size. Z is the standard deviation of 1.96 at 95% confidence range. The value for Z may be found in the statistical table that provides the area under the normal curve. People who don't eat local rice were not included. 3.2.2 Ethical approval The protocol for this study was submitted to the Ethics Committee for Basic and Applied Sciences (ECBAS) for approval. The study was conducted after approval is granted from the ECBAS with approval reference number ECBAS 033/21-22. 3.3.1 Sampling of Rice for Estimation of Heavy Metal content Previous studies on local rice production in Ghana, consultation with local rice producers and market women revealed the Ghana local rice are catergorised based on provenance. A convenient sampling approach was employed to collect samples of local rice from randomly chosen local retail markets in Accra Metropolis. The selected markets were Makola, Nima, Kaneshie, Agbogloloshie, and Madina. The rice samples were subjected to instrumental analysis to ascertain their Arsenic, Lead, Cadmium, Mercury, Copper, and Zinc levels. Some imported rice samples were also included to compare their level of the various heavy metals to the locally produced rice samples. In all forty (40) rice samples were obtained. Thirty (30) were locally produced rice and ten (10) were imported rice samples. University of Ghana http://ugspace.ug.edu.gh 30 3.3.2 Estimation of Heavy Metals in Rice Samples 3.3.2.1 Reagents and Chemicals Ultra-pure water (deionised water) from Ghana Standards Authority, Nitric acid (65% v/v) from Fisher Scientific (Pennsylvania, USA), Reference multielement stock standard solutions (Pb, AS, Cu, Cd and Zn) and a single element reference standard solution of mercury (Hg) from Sigma Aldrich (Darmstadt, Germany), Hydrogen peroxide (30% v/v) solution and Blank Solution. 3.3.2.2 Sample Pre-treatment A stainless-steel homogenizer was used to blend and homogenize the rice samples (Warring Commercial blender). To ascertain the varied levels of heavy metals, the samples were microwave digested and then subjected to an ICP-MS analysis. A powerful mixer grinder was used to crush the rice samples (Warring commercial blender). The materials were weighed using an electronic scale, and they were digested using an Italian microwave digester (Milestone start D Sorisole). The solution was stored for examination in centrifuge tubes (50mL). 3.3.2.3 Digestion Procedure A Teflon PTFE jar was used to weigh each sample twice (0.5g each). One (1) mL of deionized water, 5 mL of HNO3 (65% v/v), and 3 mL of H2O2 (30% v/v) were used to treat the samples of powdered rice. Following that, the samples were digested in a microwave digester for 50 minutes at 170 °C, 50 bars of pressure, and 1000 watts of power. The digested samples were put into the 50 mL centrifuge tubes after they had cooled to room temperature and were topped off with 25 mL of deionized water. University of Ghana http://ugspace.ug.edu.gh 31 3.3.2.4 Equipment for Heavy Metal Analysis ICP-MS (Inductively Coupled Plasma - Mass Spectrometer): A NexION triple quad mass spectrometer that operates in the mass range of 5 amu to 20 amu and uses an inductively coupled argon (Purity of at least 99.99%) plasma. The mass spectrometer had a sensitivity to reach the analysis's detection limit and could resolve 1amu peak width at 5% peak height or better (resolution 300) when utilized in routine settings. It also had a nebulizing system, a low-pulsion peristaltic pump, and a mass flow controller for the nebulizer gas. 3.3.2.5 Quality Control and Assurance To guarantee that the analytical data obtained is correct and dependable, quality assurance techniques were used during the study. Each set of samples had its own reagent blanks tested as a guide to ensure that sample findings were accurate in the case of heavy metal contamination in the water or reagents utilized. Additionally, each batch of analysis contained a verified reference material with predetermined concentrations (CRM Dorm 4, and FAPAS proficiency material). The certified reference materials (Dorm 4) and PT (powdered rice) used in this research were given by the National Research Council of Canada and FAPAS, in that order. To make sure the ICP-MS is being monitored and managed, standard solutions were checked periodically (1 in every 10 samples) throughout the studies. Samples were checked in duplicate to guarantee consistent test outcomes. University of Ghana http://ugspace.ug.edu.gh 32 3.4 Exposure Risk Assessment Exposure assessment and Human Risk for each metal was determined using the (U.S. EPA, 1989) approach as follows: i) Daily intake assessment (EDI) EDI = C × IR × ED × EF/BW × AT The terms listed below are defined: C represents the concentration of various metals in rice (ng/g), IR represents the average daily consumption of rice (g/d), ED represents the exposure period (64.68 years, which is equal to the average lifespan in Ghana), EF represents the exposure frequency (365 days per year), BW represents the body weight (kg), and AT represents the average exposure time (U.S. EPA, 1989, 2020). ii) Estimated Weekly Intake (EWI) EWI = C × WC/BW where BW is the average body weight, WC is the weekly rice consumption for each person, and C is the average concentration of heavy metals in rice (mg/kg) (kg) iii) Non-carcinogenic risks The following equation, known as the Hazard Quotient (HQ), was used to calculate the non- carcinogenic risks: HQ is calculated as EDI / RfD, where RfD (mg kg1 day1) is the reference dosage of each heavy metal under research (Saha et al., 2016). A potential non-carcinogenic influence on human health would exist if the computed HQ value is greater than one. The non- carcinogenic impact is unlikely to occur if value is less than or equal to one. University of Ghana http://ugspace.ug.edu.gh 33 iv) Carcinogenic Risks The carcinogenic risk is the possibility of developing cancer in a person's lifetime because of exposure to a probable carcinogen. The equation below was used to calculate the cancer risk (CR) = EDI × SF where: EDI (mg /kg/BW/day) is the estimated daily intake, SF (mg/kg/day) is the slope factor of the various metals (U.S. EPA, 1988). 3.5 Data Analysis The collected data was placed into an Excel 2019 spreadsheet and analyzed using SPSS's ANOVA statistical techniques. The 95% confidence level was used in every instance to compare the means. Microsoft Excel version 19 was used to create all descriptive statistics and graphs. Tables and figures were used to present the data. University of Ghana http://ugspace.ug.edu.gh 34 CHAPTER FOUR RESULTS AND DISCUSSION 4.1 Local Rice Varieties Information acquired from the traders during the collection of rice samples for heavy metal analysis revealed that local rice is split into two categories: branded and unbranded. Most of the local rice types found in market areas were classified according to their source, or site of cultivation. The indigenous varieties of rice were Tamale brown rice, Tamale white rice, Hohoe brown rice, Hohoe white rice, Kumasi brown rice, and Kumasi white rice. This was an indication the local rice sold in Accra's market areas originates in the Hohoe area of the Volta Region, Kumasi of the Ashanti Region, and Tamale of the Northern Region. 4.2 Survey on Local Rice Consumption A total of 385 participants were consented to participate in the consumer survey. Personal information (sex, age, and body weight) and the amount of local rice consumed per meal (g/meal), frequency of rice consumption (meals/week), principal point of purchase, and consumption frequency were some of the data collected. Infants and young children were not directly interacted with as they were vulnerable participants. This group's questions were addressed by parents or guardians. University of Ghana http://ugspace.ug.edu.gh 35 4.2.1 Gender Distribution of Respondents Three hundred and eight-five (385) respondents' gender breakdown is shown in Figure 1. Male respondents made up 164, or 43% of the participants, while female respondents made up 221 or 57% of the respondents. Female participants made up a larger percentage of respondents than male respondents, because when data were being collected, women were far more approachable and eager to interact than men, who typically provided excuses for their busyness or general unwillingness to listen to what you had to say. Figure 1 Gender Distribution of Respondents Male, 164, (43%) Female, 221, (57%) University of Ghana http://ugspace.ug.edu.gh 36 4.2.2 Age Group of Respondents In groups, Figure 2 displays the 385 respondents' age distribution. Fifty-one representing 13% of the 385 respondents were under the age of twenty. Twenty to twenty-nine (20–29)-year-olds made up 155 respondents (40%); 30–39-year-olds made up 95 (25%); 40–49-year-olds made up 49 (13%); and people over 50 made up 35 (9%). Figure 2 Age Groups of Respondents (in years) <20 years (13%) 20-29 years (40%) 30-39 years (25%) 40-49 years (13%) 50+ years (9%) University of Ghana http://ugspace.ug.edu.gh 37 4.2.3 Body Weight of Respondents Figure 3 displays the respondents' body weights (in kg). Out of 385 responses, 18 were under 40 kg (>40 kg) in weight, 43 were in the (40-49) weight range, 66 were in the (50-59) weight range, 80 were in the (60-69) weight range, 75 were in the (70-79) weight range, 79 were in the (80-89) weight range, and 24 were 90 kg and more. Figure 3 Body Weight (Kg) of Respondents <40 kg (5%) 40-49 kg (11%) 50-59 kg (17%) 60-69 kg (21%) 70-79 kg (19%) 80-89 kg (21%) 90 kg and above (6%) University of Ghana http://ugspace.ug.edu.gh 38 4.2.4 Educational Level of Respondents The respondents' highest level of education is shown in Table 1. Of the 385 responses, 12 cited primary school, 36 said they had finished middle school or junior high school, 93 said they had finished sixth form or secondary school, and 244 said they had completed postsecondary education. This implies that everyone who replied to the survey had some type of formal education, and that more than half had finished tertiary education. This made it easier to collect data because most people understood the concept and what was required of them. Additionally, there were comments and even suggestions on how to strengthen the nation's domestic rice industry because most respondents were aware of how most neighbouring nations—Nigeria, for instance—produce and consume domestically grown rice as opposed to imported foreign samples. Table 1 Educational Level of Respondents Highest Educational Level Frequency (N) Percentage (%) Primary school 12 3 Middle School/JHS 36 9.4 Sixth Form/Secondary School 93 24.2 Tertiary 244 63.4 None 0 0 Total 385 100 University of Ghana http://ugspace.ug.edu.gh 39 4.2.5 Occupation of Respondents The respondents' occupations are displayed in Figure 4. Out of 385 respondents, 50% were employed; 29% were students;14% were unemployed; and 7% were retired. With less than 30% being either unemployed or retirees, this shows that more than 70% of the respondents were either employed or students. Figure 4 Occupation of Respondents 14% 29% 50% 7% Unemployed Student Employed Retired University of Ghana http://ugspace.ug.edu.gh 40 4.2.6 Reasons for the Consumption of Local Rice Figure 5 displays the justifications given by respondents for eating local rice. Ten (10) of the 385 respondents said price, 12 mentioned packaging, 18 preferred quality, 30 mentioned taste, 60 selected closeness to the point of purchase, 60 mentioned aroma, 65 mentioned cooking ease, and 130 mentioned nutritional content as being reasons for consuming locally produced rice. This outcome shows that most respondents consume it for its nutritional value Additionally, after speaking with the majority of respondents, some came to the conclusion that most of our locally produced foods are free of added additives and chemicals, making them natural and healthy for their bodies' development as opposed to imported samples, which are high in chemicals. Figure 5 Reasons for Consuming Local Rice Nutritional Content Cooking convenience Aroma Proximity to point of purchase Taste Quality Packaging Price 34% 17% 15% 15% 8% 5% 4% 2% University of Ghana http://ugspace.ug.edu.gh 41 4.2.7 Place of Purchase for Local Rice Where respondents bought their local rice is shown in Table 2. Two hundred out of the 385 respondents purchase their local rice from the neighbourhood open market, 68 mentioned a grocery store, convenience store, or shopping centre, and 117 identified a restaurant or fast-food joint as the various points where the purchase their local rice. Due to pricing, the majority of respondents said that their preferred place to make a purchase was not a supermarket, convenience store, or shopping mall. This is because most of these establishments stock branded samples that are slightly more expensive than what is offered in local open markets. Table 2 Place of Purchase for Local Rice Place of Purchase Frequency (N) Percentage (%) Local open market 200 52 Supermarket/shopping mall 68 18 Restaurant or food joints 117 30 Total 385 100 University of Ghana http://ugspace.ug.edu.gh 42 4.2.8 Local Rice Consumption by Respondents Figure 6 displays the respondents' local rice consumption habits. Ninety (90) people indicated that local rice is a staple in their diet; 220 of them consume it weekly, 60 consume it monthly, and 15 consume it annually. This demonstrates that rice is a common staple food. This is consistent with a Ministry of Food and Agriculture assessment from 2020 that named rice as the second-most significant cereal after corn and that it has established itself as a significant staple food in Ghana. (MoFA, 2020). Figure 6 Local Rice Consumption Pattern of Respondents Daily 23% Weekly 57% Monthly 16% Yearly 4% University of Ghana http://ugspace.ug.edu.gh 43 4.2.9 Frequency and Quantity of Local Rice consumption for Adults The amount of local rice consumed by respondents and their associated patterns were described in Table 3. Forty-two respondents consumed 175 grams of local rice per day, 48 consumed 262.5 grams per day, 12 consumed 262.5 grams once per week, 8 consumed 350 grams once per week, 10 consumed 437.5 grams per week, 35 consumed 525 grams per week, and 155 consumed more than 525 grams per week, 60 consumed more than 525 grams once per month, and 15 consumed more than 525 grams once per year. It is clear from the data that more respondents consumed rice on a daily and weekly basis than on a monthly and yearly basis. Table 3 Quantity and Frequency of Local Rice Consumption for Adults Quantity consumed (grams) Pattern Frequency Percentage (%) 175 Daily 42 10.9 262.5 262.5 Daily Weekly 48 12 12.5 3.1 350 Weekly 8 2.1 437.5 Weekly 10 2.5 525 Weekly 35 9.1 525+ Weekly 155 40.3 525+ Monthly 60 15.6 525+ Yearly 15 3.9 Total 385 100 University of Ghana http://ugspace.ug.edu.gh 44 4.2.10 Consumption of Local rice by Children 4.2.10.1 Respondents whose households had children who consume Local Rice Children who eat local rice in their households are represented in Figure 7. Two hundred and twenty-six of the 385 respondents have children who eat local rice at home, as opposed to 159 who do not. Figure 7 Respondents whose households had children who consume local rice Yes 59% No 41% University of Ghana http://ugspace.ug.edu.gh 45 4.2.10.2 Age group distribution of children in respondents’ households The distribution of children's ages in the households of respondents is shown in Figure 8. There was a total of 405 children. Forty-five children were identified in the age ranges of 6 to 11 months, 120 in 1 to 3 years, 140 in 4 to 9 years, and 100 in 10 to 14 years. Figure 8 Age Group Distribution of Children Who Consume Local Rice 6-11 months 11% 1-3 years 30% 4-9 years 34% 10-14 years 25% University of Ghana http://ugspace.ug.edu.gh 46 4.2.10.3 Body weight of children who consume Local Rice The weight distribution of 405 children in the household of the respondents are shown in Figure 9. Eighteen children were under 5 kilograms in weight, 43 were between 5 and 10 kilograms, 90 were between 11 and 20 kilograms, 75 were between 21- 30 kilograms, 76 were between 31 and 40 kilograms, 79 were between 41 and 50 kilograms, and 24 were over this weight (50 kilograms). Figure 9 Body Weight of Children who Consume Local Rice <5 4% 5-10 11% 11-20 22% 21-30 19% 31-40 19% 41-50 19% 50+ 6% University of Ghana http://ugspace.ug.edu.gh 47 4.2.10.4 Local Rice Consumption pattern of Children The local rice consumption pattern of 405 children is displayed in Figure 10. Of the 405 kids, 105 ate local rice every day, 295 ate it once a week, and 5 ate it once a month. Only 5 children ate local rice every month, which means 99% of children ate local rice every day and every week. Adult consumption patterns were more prevalent on a daily and weekly basis. Therefore, children's local rice consumption habits mirrored those of adults. This may be mostly due to the fact that most parents and other adult caregivers have a significant impact on the amount, caliber, and eating habits of their children. (Robinson et al., 2001; Scaglioni et al., 2008). Figure 10 Local Rice Consumption Pattern of Children Daily 26% Weekly 73% Monthly 1% University of Ghana http://ugspace.ug.edu.gh 48 4.2.10.5 Quantity and Frequency of Local Rice Consumption by children The quantity and frequency of local rice eating among 405 kids are shown in Table 4. From the 405 kids, 70 ingested 34.75 grams every day, 35 consumed 87.5 grams every day, 83 took 87.5 grams every week, 140 consumed 175 grams every week, 70 consumed 262.5 grams every week, and 5 consumed 350 grams every month. Similar to adults, more children ate rice daily, weekly, and occasionally. Table 4 Quantity and Frequency of Local Rice Consumption by Children Quantity consumed (grams) Pattern Frequency Percentage (%) 43.75 Daily 70 17.3 87.5 87.5 175 Daily Weekly Weekly 35 83 140 8.6 20.5 34.6 262.5 350 350 Weekly Weekly Monthly 70 2 5 17.3 0.5 1.2 Total 405 100 University of Ghana http://ugspace.ug.edu.gh 49 The average weight and age for both children and adults are shown in Table 5. Additionally, it shows the typical daily and weekly intake for both adults and kids. Table 5 Average (age group, weight, and quantity of rice consumed) by children and adults Average age group (years) Average weight (kilograms) Average daily intake (grams) Average weekly intake (grams) Adult 20-29 60-69 221.67 496.36 Children 4-9 21-30 58.33 142.43 University of Ghana http://ugspace.ug.edu.gh 50 4.3.1 Heavy Metals Analysis of Local Rice Samples To determine the concentrations of arsenic, lead, cadmium, mercury, copper, and zinc, local rice samples were procured from open retail markets in the Accra Metropolitan Area. This study used six (6) different types of locally grown rice. Thirty (30) samples of locally produced rice were collected from the Nima, Kaneshie, Madina, Markola, and Agbogbloshie markets, which are among the five (5) largest local open markets in the Accra Metropolitan Area. VB (Volta Brown), VW (Volta White), AB (Ashanti Brown), AW (Ashanti White), NB (Northern Brown), and NW (Northern White) are the names given to the local rice samples based on their provenance where they are cultivated or produced. The same process utilized for the local rice analysis was applied to ten (10) additional foreign rice samples to compare the different heavy metal contents in them. 4.3.2 Arsenic (As) The maximum and minimum concentrations of Arsenic found in the 30 rice samples was 0.123 mg/kg and 0.0082 mg/kg which was found in two different Volta Brown samples. The mean concentration of Arsenic in Volta Brown was 0.05 mg/kg, Volta White was 0.038 mg/kg, Ashanti Brown was 0.06 mg/kg, Ashanti White was 0.056 mg/kg, Northern Brown was 0.056 mg/kg, Northern White was 0.044 mg/kg, presented in table 6. One-way ANOVA analysis displayed no significant variations (p > 0.05) in the mean concentrations (Table 6). The amount of arsenic discovered in the local rice samples was less than the maximum permitted limit allowed by Codex (0.2 mg/kg). While both local and imported rice are below the Codex maximum allowable values, the mean concentration for the ten imported rice samples that were University of Ghana http://ugspace.ug.edu.gh 51 examined was 0.081 mg/kg, suggesting that the amount of arsenic in imported rice was greater than local rice. A study conducted by Asamoa, (2016), also found concentrations of Arsenic in the unpolished and polished rice samples to be lower than the CODEX allowed limits for rice. Adomako et al. (2021) also found a lower concentration of Arsenic in Ghanaian rice as compared to other countries such as the United States and Thailand. Studies from other nations discovered higher levels of arsenic in samples of rice. For instance, rice grains from the south and east of China's Hunan Province have significant amounts of total arsenic, according to Ma, Wang, Jia, and Yang's (2016) research. In two high-yielding rice cultivars produced in paddy fields in Matlab, Bangladesh, Sandhi et al., (2017) also discovered higher concentrations of arsenic (0.09-0.21 mg As kg1). Arsenic was identified in rice samples that were analyzed at a higher concentration than other metals. This supports research by Adomako et al. (2011), who found that Ghanaian rice had a greater arsenic content than other grains. However, compared to global mean values, Ghanaian rice has lower Arsenic values according to Adomako et al., (2011), which has been confirmed in this study. Although arsenic naturally occurs in the ground, its concentration in soils has grown because of its usage in irrigation water and various mobilization processes, ATSDR (2007). This has had an impact on the agricultural system and led to arsenic absorption in rice (Kalita et al., 2018). In addition, compared to other heavy metals, rice has a greater translocation factor (TF) for arsenic (0.8), which might explain why there is a larger concentration of arsenic in the rice samples. Arsenic is considered as one of the elements with a high risk of soil to food chain transfer (Zhao & Wang, 2019). Rice grown amid continual floods has a large amount of arsenic in its edible component, claim Meharg and Rahman (2003). This is because iron oxyhydroxide plague develops, releasing a considerable amount of arsenic University of Ghana http://ugspace.ug.edu.gh 52 into the plant. Iron oxyhydroxide plague develops because of the oxygenation of the plant's rhizosphere in anaerobic environments, and the rate at which the plague forms rise in low phosphorus environments. A pho