Trace Metal Concentrations in Local and Imported Rice Consumed in Southeast Nigeria
Main Article Content
Abstract
Rice (Oryza sativa L.) is a staple for half the world’s population and a major component of the Nigerian diet. As domestic production lags behind rising demand, Nigeria increasingly relies on rice imports, raising food safety concerns. This study aims to determine and compare concentrations of Zn, Pb, Cr, Cu, and Cd in 36 rice samples (20 imported, 16 locally grown; short- and long-grain) collected from markets across five southeastern Nigerian states. Additionally, health risks from rice consumption were assessed. Samples were processed and analysed by atomic absorption spectrometry. The objectives were to quantify trace metal levels in local and imported rice, evaluate differences by grain size and location, assess potential health risks, and compare results with FAO/WHO limits and literature. Results showed a decreasing concentration trend: Zn > Cd > Cu > Pb > Cr. Mean concentrations (±SD) were 1.24±1.15 mg/kg (Zn), 0.58±1.55 mg/kg (Cd), 0.24±0.17 mg/kg (Cu), 0.18±0.23 mg/kg (Pb), and 0.12±0.27 mg/kg (Cr). All metals except Cd were below FAO/WHO maximum limits, but some samples exceeded the 0.2 mg/kg Cd threshold. Locally produced rice contained significantly higher Zn (3.6×), Pb (2.0×), and Cd (18×) than imported rice. Short-grain rice had higher Zn, Pb, and Cd than long-grain. Notably, rice from Ebonyi State (a known Pb-Zn mining region) showed extreme Cd (1.89±3.27 mg/kg), suggesting geogenic contamination. Health risk assessments indicated estimated daily intakes and hazard quotients below harmful levels for adults and children. Our findings provide important baseline data and highlight the need for continued monitoring of trace metals in rice for food safety in Nigeria. The findings suggest that rice consumed in southeastern Nigeria is generally safe, though residents of Ebonyi State who frequently consume locally produced rice may be at risk of increased cadmium accumulation. Regular monitoring of food products for metal contamination remains essential for public health protection. This study thus contributes critical baseline data to guide food safety policy and monitoring efforts in Nigeria.
Article Details
This work is licensed under a Creative Commons Attribution 4.0 International License.
Adel, M., Oliveri Conti, G., Dadar, M., Mahjoub, M., Copat, C., & Ferrante, M. (2016). Heavy metal concentrations in edible muscle of whitecheek shark, Carcharhinus dussumieri (elasmobranchii, chondrichthyes) from the Persian Gulf: A food safety issue. Food and Chemical Toxicology, 97, 135–140. https://doi.org/10.1016/j.fct.2016.09.002 DOI: https://doi.org/10.1016/j.fct.2016.09.002
Ahmad, S., Adiba Khan Sehrish, Alomrani, S. O., Zhang, L., Waseem, M., Shamaila Noureen, Ullah, I., Rohina Tabassam, Abbas, G., & Ali, S. (2024). Combined application of biochar and metal-tolerant bacteria alleviates cadmium toxicity by modulating the antioxidant defense mechanism and physicochemical attributes in rice (Oryza sativa L.) grown in cadmium-contaminated soil. Plant Stress, 11, 100348–100348. https://doi.org/10.1016/j.stress.2024.100348 DOI: https://doi.org/10.1016/j.stress.2024.100348
Ajah, D. N., Agboeze, E., Ihedioha, J. N., Chukwudi-Madu, E., & Chime, C. C. (2022). Levels of Zinc (Zn), Copper (Cu), Iron (Fe), and Cadmium (Cd) in Soil, Rice Stalk, and Oryza Sativa Grain in Ishiagu Rice Field, Ebonyi State, Nigeria; Human Health Risk. Journal of the Nigerian Society of Physical Sciences, 891. https://doi.org/10.46481/jnsps.2022.891 DOI: https://doi.org/10.46481/jnsps.2022.891
Alengebawy, A., Abdelkhalek, S. T., Qureshi, S. R., & Wang, M.-Q. (2021). Heavy Metals and Pesticides Toxicity in Agricultural Soil and Plants: Ecological Risks and Human Health Implications. Toxics, 9(3), 42. https://doi.org/10.3390/toxics9030042 DOI: https://doi.org/10.3390/toxics9030042
Anjali, K., Kumar, H., Powell, M. A., Prafulla, K. S., Harmanpreet, S. K., & Mittal, S. (2023). Trace Element Occurrence in Vegetable and Cereal Crops from Parts of Asia: A Meta-data Analysis of Crop-Wise Differences. Current Pollution Reports. https://doi.org/10.1007/s40726-023-00248-9
APHA. (2020). American Public Health Association, Standard Methods: For the Examination of Water and Wastewater, APHA, AWWA, WEF/1995, APHA Publication, 1995. Sciepub.com. https://www.sciepub.com/reference/330361
Azzi, V., Kanso, A., Kazpard, V., Kobeissi, A., Lartiges, B., & El Samrani, A. (2017). Lactuca sativa growth in compacted and non-compacted semi-arid alkaline soil under phosphate fertilizer treatment and cadmium contamination. Soil and Tillage Research, 165, 1–10. https://doi.org/10.1016/j.still.2016.07.014 DOI: https://doi.org/10.1016/j.still.2016.07.014
Copat, C., Arena, G., Fiore, M., Ledda, C., Fallico, R., Sciacca, S., & Ferrante, M. (2013). Heavy metals concentrations in fish and shellfish from eastern Mediterranean Sea: Consumption advisories. Food and Chemical Toxicology, 53, 33–37. https://doi.org/10.1016/j.fct.2012.11.038 DOI: https://doi.org/10.1016/j.fct.2012.11.038
Cu, S. T., Warnock, N. I., Pasuquin, J., Dingkuhn, M., & Stangoulis, J. (2021). A high-resolution genome-wide association study of the grain ionome and agronomic traits in rice Oryza sativa subsp. indica. Scientific Reports, 11(1), 19230. https://doi.org/10.1038/s41598-021-98573-w DOI: https://doi.org/10.1038/s41598-021-98573-w
Dwivedi, M., Jindal, D., Jose, S., Dwivedi, M., & Nayak, P. (2024). Elements in Trace Amount with a significant role in Human Physiology: a Tumor Pathophysiological and Diagnostic Aspects. Journal of Drug Targeting, 1–52. https://doi.org/10.1080/1061186x.2024.2309572 DOI: https://doi.org/10.1080/1061186X.2024.2309572
Fang, Y., Sun, X., Yang, W., Ma, N., Xin, Z., Fu, J., Liu, X., Liu, M., Mariga, A. M., Zhu, X., & Hu, Q. (2014). Concentrations and health risks of lead, cadmium, arsenic, and mercury in rice and edible mushrooms in China. Food Chemistry, 147, 147–151. https://doi.org/10.1016/j.foodchem.2013.09.116 DOI: https://doi.org/10.1016/j.foodchem.2013.09.116
Huybrechts, M., Hendrix, S., Bertels, J., Beemster, G. T. S., Vandamme, D., & Cuypers, A. (2020). Spatial analysis of the rice leaf growth zone under controlled and cadmium-exposed conditions. Environmental and Experimental Botany, 177, 104120–104120. https://doi.org/10.1016/j.envexpbot.2020.104120
Islam, Md. A., Romić, D., Akber, Md. A., & Romić, M. (2017). Trace metals accumulation in soil irrigated with polluted water and assessment of human health risk from vegetable consumption in Bangladesh. Environmental Geochemistry and Health, 40(1), 59–85. https://doi.org/10.1007/s10653-017-9907-8 DOI: https://doi.org/10.1007/s10653-017-9907-8
Jafari, A., Kamarehie, B., Ghaderpoori, M., Khoshnamvand, N., & Birjandi, M. (2018). The concentration data of heavy metals in Iranian grown and imported rice and human health hazard assessment. Data in Brief, 16, 453–459. https://doi.org/10.1016/j.dib.2017.11.057
Kormoker, T., Proshad, R., Islam, M. S., Tusher, T. R., Uddin, M., Khadka, S., Chandra, K., & Sayeed, A. (2020). Presence of toxic metals in rice with human health hazards in Tangail district of Bangladesh. International Journal of Environmental Health Research, 1–21. https://doi.org/10.1080/09603123.2020.1724271
Huybrechts, M., Hendrix, S., Bertels, J., Beemster, G.T., Vandamme, D. & Cuypers, A. (2020). Spatial analysis of the rice leaf growth zone under controlled and cadmium-exposed conditions. Environmental and Experimental Botany 177, 10412. https://doi.org/10.1016/j. envexpbot.2020.104120. DOI: https://doi.org/10.1016/j.envexpbot.2020.104120
Jafari, A., Kamarehie, B., Ghaderpoori, M., Khoshnamvand, N. & Birjandi, M. (2018). The concentration data of heavy metals in Iranian grown and imported rice and human health hazard assessment. Data Brief. 16:453–459. http://doi:10.1016/j. dib.2017.11.057. DOI: https://doi.org/10.1016/j.dib.2017.11.057
Kormoker T., Ram P., Md Saiful I., Tanmoy R. T., Minhaz U., Sujan K., Krishna C. & Abu, S. (2020). Presence of toxic metals in rice with human health hazards in Tangail district of Bangladesh. International Journal of Environmental Health Research, 32 http://doi:10.1080/09603123.2020.1724271. DOI: https://doi.org/10.1080/09603123.2020.1724271
Nutescu, E.A., Burnett, A., Fanikos, J., Spinler, S. & Wittkowsky, A. (2016). Pharmacology of anticoagulants used in the treatment of venous thromboembolism. Journal of Thrombosis and Thrombolysis, 41(1), 15–31. https://doi.org/10.1007/s11239-015-1314-3 DOI: https://doi.org/10.1007/s11239-015-1314-3
Omaka, O.N, Aghamelu, O.P., Ike-Amadi, C.A. & Ofoezie, R.C. (2017). Assessment of the quality of groundwater from different parts of southeastern Nigeria for potable use, Environmental Earth Sciences, 76, 344-367. https://doi.org/10.1007/s12665-017-6680-z DOI: https://doi.org/10.1007/s12665-017-6680-z
Onuchukwu, S. C., Udousoro, I. I., & Umoren, I. U. (2024). Characterization of toxic metals and flame retardants in printed circuit boards from electronic waste. World Journal of Applied Science & Technology, 16(1), 10-17. https://doi.org/10.4314/wojast.v16i1.10 DOI: https://doi.org/10.4314/wojast.v16i1.10
Onuchukwu, S. C., Nnorom, I. C., Udoh, S. S., & Opara, J. O. (2025). Genetic Diversity and Stress Tolerance in Nigerian Horticultural Crops: Multifactorial Influences and Breeding Implication. African Journal of Agricultural Science and Food Research, 20(1), 138-176. https://doi.org/10.62154/ajasfr.2025.020.01020 DOI: https://doi.org/10.62154/ajasfr.2025.020.01020
Plum, L.M., Rink, L. & Haase, H. (2010). The essential toxin: impact of zinc on human health. International Journal of Environmental Research and Public Health, 7 (4), 1342–1365. https://doi.org/10.3390/ijerph7041342 DOI: https://doi.org/10.3390/ijerph7041342
Poutanen, K.S., Kårlund, A.O., Gómez-Gallego, C., Johansson, D. P., Scheers, N.M., Marklinder, I.M., Eriksen, A.K., Silventoinen, P.C., Nordlund, E., Sozer, N., Hanhineva, K.J., Kolehmainen, M. & Landberg, R. (2021). Grains – a major source of sustainable protein for health. Nutrition Reviews, 80(6), 2459-2473. https://doi.org/10.1093/nutrit/nuab084 DOI: https://doi.org/10.1093/nutrit/nuab084
Proshad R, Kormoker T, Islam MS, and Chandra K. (2019). Potential health risk of heavy metals via consumption of rice and vegetables grown in the industrial areas of Bangladesh. Human & Ecological Risk Assessment: an International Journal, 1–23. http://doi:10.1080/10807039.2018.1546114 DOI: https://doi.org/10.1080/10807039.2018.1546114
Qiao, M., Cai, C., Huang, Y., Liu, Y., Lin, A. & Zheng, Y. (2011). Characterization of soil heavy metal contamination and potential health risk in metropolitan region of northern China. Environmental Monitoring and Assessment, 172 (1), 353–365. http://doi:10.1007/s10661-010-1339-1. DOI: https://doi.org/10.1007/s10661-010-1339-1
Rahman, A., Hossain, L., Foysal, A. & Akter, A. (2014). Impact of climate change on food security in South-West Coastal Region of Bangladesh. American Journal of Experimental Agriculture, 4(12), 1916–1934. https://doi.org/10.9734/ajea/2014/6165 DOI: https://doi.org/10.9734/AJEA/2014/6165
Rasheed, A., Fahad, S., Aamer, M., Hassan, M. U., Tahir, M. M., & Wu, Z. M. (2020). Role of genetic factors in regulating cadmium uptake, transport and accumulation mechanisms and quantitative trait loci mapping in rice. a review. Applied Ecology & Environmental Research, 18(3). https://aloki.hu/pdf/1803_40054023.pdf DOI: https://doi.org/10.15666/aeer/1803_40054023
Salam, L.B., Obayori, O.S., Ilori, M.O. & Amund, O.O. (2020). Effects of cadmium perturbation on the microbial community structure and heavy metal resistome of a tropical agricultural soil. Bioresources & Bioprocessing 7, 1–19. https://doi.org/10.1186/s40643-020-00314-w. DOI: https://doi.org/10.1186/s40643-020-00314-w
Udousoro, I. I., Onuchukwu, S. C., & Umoren, I. U. (2025). Assessment of Electronic Waste for Heavy Metal Contamination and Its Impacts on Ecosystem Health. Environmental Pollution and Management, 3,1-10. https://doi.org/10.1016/j.epm.2025.09.003 DOI: https://doi.org/10.1016/j.epm.2025.09.003
Wang, Y., Jiang, X., Li, K., Wu, M., Zhang, R., Zhang, L. & Chen, G. (2014). Photosynthetic responses of Oryza sativa L. seedlings to cadmium stress: physiological, biochemical and ultrastructural analyses. Biometals 27, 389–401. https://doi.org/10.1007/s10534-014-9720-0. DOI: https://doi.org/10.1007/s10534-014-9720-0
WHO. (2017). Country Assignments to the 13 Proposed GEMS/ Food Consumption Cluster Diets. World Health Organization (WHO). Geneva, Switzerland.
Zazouli, M.A. (2008). Cadmium content in rice and its daily intake in Ghaemshahr region of Iran. African Journal of Biotechnology, 7 (20), 3686–3689. https://doi.org/10.4314/ajb.v7i20.59412
Zazouli, M.A. (2010). Investigation of cadmium and lead contents in Iranian rice cultivated in Babol region. Asian Journal of Chemistry, 22 (2), 13–69. https://www.researchgate.net/profile/Hassan-Izanloo3/publication/259496192_Investigation_of_Cadmium_and_Lead_Contents_in_Iranian_Rice_Cultivated_in_Babol_Region/links/54c143b60cf25b4b8071e837/Investigation-of-Cadmium-and-Lead-Contents-in-Iranian-Rice-Cultivated-in-Babol-Region.pdf
Zhang, F., Liu, M., Li, Y., Che, Y. & Xiao, Y., (2019). Effects of arbuscular mycorrhizal fungi, biochar and cadmium on the yield and element uptake of Medicago sativa. Science of the Total Environment, 655, 1150–1158. https://doi.org/10.1016/j.scitotenv.2018.11.317 DOI: https://doi.org/10.1016/j.scitotenv.2018.11.317
Article Sidebar
