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

Abstract

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.