Determination of Heavy Metal Levels in Hybrid and Indigenous Kamba Maize Seed Varieties from Farms in Masii, Machakos County, Kenya

Maize is a staple food consumed by the Kenyan population; however, heavy metal contamination in maize seeds poses significant health risks. This study determined the levels of lead (Pb2+), cadmium (Cd2+), zinc (Zn2+), copper (Cu2+), and manganese (Mn2+), in three maize seed varieties harvested from Masii Ward, Mwala Sub-County, Machakos County, Kenya. Fresh and dry SC Duma 43 and SC Sungura 301 hybrid with Indigenous Kamba (Kinyaanya) maize seeds, were collected from selected farms in Mbaani, Kathama, and Muthei sub-location in Masii Ward and transported to the Department of Chemistry, University of Nairobi, for analysis. The dried and ground maize seeds were digested using an optimized acid mixture of HNO₃, HClO₄, and H₂O₂ in a ratio of 2.5:0.75:0.5 v/v at 105°C for 2.5 hours. The heavy metals were analysed using Atomic Absorption Spectroscopy (AAS). The results showed that zinc levels ranged from 0.343 ± 0.0505 mg/g to 0.389 ± 0.0007mg/g, cadmium from 0.562 ± 0.217 mg/g to 1.998 ± 0.110 mg/g, copper from 0.700 ± 0.0380 mg/g to 0.756 ± 0.101 mg/g, manganese from 0.270 ± 0.0586 mg/g to 2.745 ± 0.851 mg/g, and lead from 8.247 ± 0.798 mg/g to 10.449 ± 0. 398 mg/g. Despite falling below World Health Organization / Food and Agriculture Organization (WHO/FAO), and Kenya Bureau of Standards (KEBS) limits , the detected levels of zinc, copper, and manganese requires monitoring regarding long-term bioaccumulation. Cadmium and lead levels exceeded permissible limits (0.1 and 0.5 mg/g, respectively), with lead concentration particularly high across all three varieties. The analysis revealed that maize seeds pose severe health risks and are unfit for human consumption. This study highlights the urgent need for regular monitoring of heavy metals contamination in food crops and for the implementation on remediation strategies to safeguard public health in Machakos County and similar agricultural regions in Kenya.

Heavy metals, Maize seeds, Atomic Absorption Spectroscopy, SC Duma 43, SC Sungura 301, Indigenous Kamba maize, Lead, Cadmium, Food safety, Machakos County.

1. Aladesanmi, O. T., Oroboade, J. G., Osisiogu, C. P., & Osewole, A. O. (2019). Bioaccumulation factor of selected heavy metals in Zea mays. Journal of Health and Pollution, 9(24), 191207. [Google Scholar] [Crossref]

2. Atta, M. I., Zehra, S. S., Ali, H., Ali, B., Abbas, S. N., Aimen, S., Sarwar, S., Ahmad, I., Hussain, M., Al-Ashkar, I., Elango, D., & El Sabagh, A. (2023). Assessing the effect of heavy metals on maize (Zea mays L.) growth and soil characteristics: Implications for phytoremediation. PeerJ, 11, e16067. [Google Scholar] [Crossref]

3. Liu, J., Si, W., Xiao, Z., Tang, R., Niu, P., Fu, Y., & Shen, W. (2023). Risks to human health of exposure to heavy metals through wheat consumption near a tailings dam in North China. Polish Journal of Environmental Studies, 32(4), 3195-3207. [Google Scholar] [Crossref]

4. Jaishankar, M., Tseten, T., Anbalagan, N., Mathew, B. B., & Beeregowda, K. N. (2014). Toxicity, mechanism and health effects of some heavy metals. Interdisciplinary Toxicology, 7(2), 60-72 [Google Scholar] [Crossref]

5. Abdullahi, N., Dandago, M. A., Gambo, M. S., Abubakar, S. S., Tsoho, A. U., & Idah, P. G. (2024). Seasonal variation and uptake pattern of heavy metals in maize. Dutse Journal of Pure and Applied Sciences, 10(1a), 78-87. [Google Scholar] [Crossref]

6. Khan, M., Nazar Ibrahim Al Azzawi, T., Imran, M., Hussain, A., Mun, B.-G., Pande, A., & Yun, B.-W. (2021). Effects of lead (Pb)-induced oxidative stress on morphological and physio-biochemical properties of rice. BIOCELL, 45(5), 1413-1423. [Google Scholar] [Crossref]

7. Mitra, S., Chakraborty, A. J., Tareq, A. M., Emran, T. B., Nainu, F., Khusro, A., Idris, A. M., Khandaker, M. U., Osman, H., Alhumaydhi, F. A., & Simal-Gandara, J. (2022). Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity. Journal of King Saud University - Science, 34(3), 101865. [Google Scholar] [Crossref]

8. Agriculture and Food Authority. (2024). Food crops yearbook 2024. Ministry of Agriculture, Kenya. https://www.afa.go.ke/. [Google Scholar] [Crossref]

9. Machakos County Integrated Development Plane, 2023-2027 (MCIDP) [Google Scholar] [Crossref]

10. Deon Visser (2021): Atomic Absorption Spectroscopy principles and Applications. [Google Scholar] [Crossref]

11. World Health Organization/ Food Agricultural Organization (2024-2026): Codex Alimentary Recommended levels for heavy metals in Cereal grain. [Google Scholar] [Crossref]

12. Kenya Bureau of Standards (KEBS DKS 3010, 2024) Milled maize Products-Specification [Google Scholar] [Crossref]

13. Khan, B. N., Ullah, H., Ashfaq, Y., Hussain, N., Atique, U., Aziz, T., Alharbi, M., Albekairi, T. H., & Alasmari, A. F. (2023). Elucidating the effects of heavy metals contamination on vital organs of fish and migratory birds found at fresh water ecosystem. Heliyon, 9(11), e20968 [Google Scholar] [Crossref]

14. Briffa, J., Sinagra, E., & Blundell, R. (2020). Heavy metal pollution in the environment and their toxicological effects on humans. Heliyon, 6(9), e04691. [Google Scholar] [Crossref]

15. Morais, S., E Costa, F. G., & Lourdes Pereira, M. D. (2012). Heavy metals and human health. In J. Oosthuizen (Ed.), Environmental Health—Emerging Issues and Practice. InTech. [Google Scholar] [Crossref]

16. Nicholson F.A, Smith S.R, Alloway B.J, Carlton-Smith C, and Chambers B.J (2013). An Inventory of Heavy Metal Input to Agricultural Soils in England and Wales; Science of the Total Environment, 311, 205-219 [Google Scholar] [Crossref]

17. Singh A., Sharma R.K, Agrawal M and Marshall F.M (2010): Health Risk Assessment of Heavy Metals via Dietary Intake of Foodstuffs from the wastewater Irrigated Sites of a Dry Tropical Area of India. Food and Chemical Toxicology, 48, 611-619 [Google Scholar] [Crossref]

18. Yan, A., Wang, Y., Tan, S. N., Mohd Yusof, M. L., Ghosh, S., & Chen, Z. (2020). Phytoremediation: A promising approach for revegetation of heavy metal-polluted land. Frontiers in Plant Science, 11, 359. [Google Scholar] [Crossref]

19. Teresa Akenga, Vincent Sudoi, Walter Machuka, Emmy Kerich, Elkana Ronoh (2017): Heavy Metal Uptake in Maize Grains and Leaves in Different Agro Ecological Zones in Uasin Gishu County; Journal of Environmental Protection, 8 (12), 135-1444. [Google Scholar] [Crossref]

20. Malomo. Olu., Olufade O.I and Jimoh M.O. (2013): Evaluation of Heavy Metal Concentration in Maize Grown in Selected Industrial Areas of Ogun State and its Effects on Urban Food Security International Journal of Science, Technology and Society, 1(2):48-56 [Google Scholar] [Crossref]

21. Kate-Vera Larsen, Samuel J. Cobbina, Samuel A. Ofori and Divine Addo (2020): Quantification and health risk assessment of heavy metals in Milled maize and Millet in the Tolon District, Northern Ghana: Journal of Food Science and Nutrition 8 (8) 4205-4213 [Google Scholar] [Crossref]

• Green Synthesis of Cobalt Oxide/Gold (Coo/Au) Bimetallic Nanoparticles Using Sinapinic Acid: A Comprehensive Study
• Advances in Solar Cell Technologies: A Comprehensive Review of Material Synthesis, Structural Properties, Efficiency and Diverse Applications
• Thermal Decomposition of Co-Fe-Cr-Citrate Complex Via Structural and Spectral Study
• Surface Activity and Thermodynamic Assessment of Surfactants Derived from Oreochromis Niloticus Oil (Nile Tilapia Fish)
• Green Synthesis of Robust Metal-Organic Frameworks: A Sustainable Approach for Advanced Applications