Health Risk Assessment of Heavy Metals and Persistent Pesticides in Nigerian Rice Sold in Port Harcourt, Rivers State
Main Article Content
Abstract
Rice is a dietary staple in Nigeria, with domestic production expanding rapidly in response to national food security policies. However, concerns persist regarding chemical contamination in locally milled rice due to unregulated agrochemical use and environmental pollution across agricultural regions. This study assessed the levels of five heavy metals (Ni, Pb, Hg, Cd, Cr) and ten pesticide residues in four widely consumed Nigerian-produced rice brands: Mama Pride, Falgold, Burgun, and Mango. Composite samples were analyzed using atomic absorption spectrophotometry (AAS) and gas chromatography–mass spectrometry (GC-MS). All samples contained detectable levels of heavy metals and multiple pesticide residues, including banned organochlorines such as lindane (up to 9.56 mg/kg), hexachlorobenzene (HCB; up to 7.06 mg/kg), and γ-chlordane. Cadmium (0.010–0.028 ppm) and lead (0.022–0.076 ppm) were present in all brands. Health risk assessment revealed Hazard Index (HI) values exceeding 1 for both adults (4.91–10.53) and children (19.64–42.12), indicating significant non-carcinogenic risks. Carcinogenic risk (ILCR) ranged from 1.24 × 10⁻⁴ to 3.57 × 10⁻⁴, surpassing the acceptable threshold of 1 × 10⁻⁴. These findings demonstrate that chemical contamination in Nigerian-produced rice poses serious health hazards, underscoring the urgent need for strengthened regulatory oversight, farmer education, and national food safety monitoring to protect consumers of this essential staple.
Article Details
References
Adeleke, R. O., Oyekunle, J. A. O., & Ogunfowokan, A. O. (2021). Assessment of rice consumption pattern and exposure risk to heavy metals in Southwestern Nigeria. Environmental Monitoring and Assessment, 193(8), 521.
Adeyemi, O. A., Adetunji, M. T., & Oguntoke, O. (2020). Pesticide use practices and residues in agricultural produce in Nigeria: A review. Journal of Environmental Science and Health, Part B, 55(10), 901–912.
Alam, M. S., Islam, M. R., Islam, M. S., Hossain, M. B., & Habibullah-Al-Mamun, M. (2021). Health risk assessment of heavy metals in rice and vegetables from Bangladesh: Implications for children and adults. Environmental Science and Pollution Research, 28(15), 18943–18955.
Alloway, B. J. (2013). Heavy metals in soils: Trace metals and metalloids in soils and their bioavailability (3rd ed.). Springer. https://doi.org/10.1007/978-94-007-4470-7 DOI: https://doi.org/10.1007/978-94-007-4470-7
Anastassiades, M., Lehotay, S. J., Štajnbaher, D., & Schenck, F. J. (2003). Fast and easy multiresidue method employing acetonitrile extraction/partitioning and “dispersive solid-phase extraction” for the determination of pesticide residues in produce. Journal of AOAC International, 86(2), 412–431. DOI: https://doi.org/10.1093/jaoac/86.2.412
Codex Alimentarius Commission. (2023). Maximum levels for contaminants in food (CAC/GL 75-2010). FAO/WHO. http://www.fao.org/fao-who-codexalimentarius
EFSA Panel on Contaminants in the Food Chain (CONTAM). (2019). Scientific opinion on the update of the risk assessment on cadmium in food. EFSA Journal, 17(10), e05862. https://doi.org/10.2903/j.efsa.2019.5862 DOI: https://doi.org/10.2903/j.efsa.2019.5862
European Commission. (2023). EU pesticides database: Maximum residue levels (MRLs). https://ec.europa.eu/food/plant/pesticides/eu-pesticides-database
Eze, C. U., Uzoh, I. M., & Nwosu, J. U. (2022). Heavy metal contamination of rice (Oryza sativa L.) cultivated in Abia State, Nigeria: Implications for human health. Environmental Challenges, 8, 100542.
International Agency for Research on Cancer (IARC). (2012). Arsenic, metals, fibres, and dusts (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 100C). World Health Organization.
Kwami, A. G., Akpabli, C. K., Akpabli, E. K., & Dodoo, D. K. (2020). Pesticide residues in rice from markets in Ghana: Implications for consumer safety. Journal of Environmental Science and Health, Part B, 55(7), 601–608.
Meharg, A. A., & Rahman, M. A. (2022). Arsenic in rice: From field to fork. In A. A. Meharg & E. M. J. Hoey (Eds.), Arsenic contamination in food chains (pp. 45–68). Springer.
National Bureau of Statistics (NBS). (2024). Agricultural sample survey: Crop production statistics 2023. Federal Republic of Nigeria.
Nduka, J. K. C., & Orisakwe, O. E. (2020). Heavy metals in foods marketed in Nigeria: A review. Journal of Environmental Science and Health, Part C, 38(1), 1–20.
Ogunlela, A. E., Ojo, M. O., & Adeyemi, O. A. (2021). Pesticide residue levels in selected food crops in Nigeria: A meta-analysis. Toxicology Reports, 8, 1432–1441.
Oguntunde, P. G., Abiodun, O. J., & Lischeid, G. (2022). Pesticide use and food safety in Nigeria: Challenges and policy implications. Environment, Development and Sustainability, 24(5), 6589–6610.
Ojemaye, E. N., & Okoh, A. I. (2019). Pesticide residues in rice and processed rice products marketed in South Africa and Nigeria: Implications for human health. Environmental Monitoring and Assessment, 191(11), 687.
Oladejo, O. A., Oluwafemi, O. S., & Akinbode, S. O. (2023). Rice policy and domestic production in Nigeria: Impacts of the Anchor Borrowers’ Programme. African Development Review, 35(1), 45–58.
Olowoyo, I. O., Oyedemi, S. O., & Bassey, B. E. (2021). Heavy metal contamination of rice and vegetables from Kano metropolis, Nigeria: Health risk assessment. Environmental Monitoring and Assessment, 193(4), 189.
Rauh, V. A., & Margolis, A. E. (2016). Research review: Environmental exposures, neurodevelopment, and child mental health. Journal of Child Psychology and Psychiatry, 57(4), 451–478. DOI: https://doi.org/10.1111/jcpp.12537
U.S. Environmental Protection Agency (USEPA). (1989). Risk assessment guidance for Superfund: Volume I—Human health evaluation manual (Part A) (EPA/540/1-89/002). Office of Emergency and Remedial Response.
U.S. Environmental Protection Agency (USEPA). (1996). Soil Screening Guidance: User’s Guide. EPA/540/R-96/018. Office of Solid Waste and Emergency Response, Washington, DC.
U.S. Environmental Protection Agency (USEPA). (2004). Risk assessment guidance for Superfund: Volume I—Human health evaluation manual (Part E, Supplemental guidance for dermal risk assessment) (EPA/540/R/99/005).
U.S. Environmental Protection Agency (USEPA). (2023). Integrated Risk Information System (IRIS). https://www.epa.gov/iris
Udowelle, N. A., Asomugha, R. N., Orisakwe, O. E., & Igweze, Z. N. (2018). Heavy metal contamination of food crops grown in the oil-producing areas of Nigeria. Toxicology Reports, 5, 1157–1163.
Ugboma, C. M., Nwosu, J. U., & Eze, C. U. (2021). Environmental pollution and public health in the Niger Delta: A systematic review. Journal of Public Health in Africa, 12(2), 204–215.
United Nations Environment Programme (UNEP). (2023). Stockholm Convention on Persistent Organic Pollutants. https://www.pops.int
Valentine, O., & Ozioma, E. A. (2022). Determination of heavy metals in gels and tubes of toothpaste commonly used in Port Harcourt, Rivers State, Nigeria. Journal of Applied Chemical Science International, 13(1), 13–17. https://doi.org/10.9734/jacsi/2022/v13i130348 DOI: https://doi.org/10.56557/jacsi/2022/v13i17344
World Health Organization (WHO). (2011). Guidelines for drinking-water quality (4th ed.).
Zhang, J., Liu, Y., Liu, X., Li, Y., Wang, X., & Li, J. (2022). Health risk assessment of heavy metals in PM2.5 and PM10 during haze episodes in Beijing, China. Chemosphere, 292, 133406