Assessment of Heavy Metal Contamination and Health Risks from Urban-Grown Vegetables in Kano State, Nigeria

Abstract

This study evaluates the concentrations and associated health risks of cadmium (Cd), nickel (Ni), lead (Pb), 
manganese (Mn), and chromium (Cr), in six commonly consumed vegetables (pepper, lettuce, carrot, 
beetroot, spinach, and onion) cultivated in three urban locations in Kano State, Nigeria namely: Wudil, 
Nomans-Land, and Sharada. Metal concentrations were quantified using Microwave Plasma – Atomic 
Emission Spectroscopy (MP-AES), and the results revealed spatial and crop-specific variability. The 
highest concentrations of Cd and Mn were observed in vegetables from Wudil, with Cd range of 0.19 to 0.36mg/kg and Mn of 0.67 to 9.29 mg/kg, particularly in carrot (0.36 mg/kg) and lettuce (0.27 mg/kg), while Cr of 0.41 mg/kg and Pb of 0.82 mg/kg levels were notably elevated in samples from Sharada.  Estimated Daily Intake (EDI), Target Hazard Quotient (THQ), and Hazard Index (HI) were calculated to assess non-carcinogenic health risks. Cd consistently exhibited the highest THQ across all samples, with carrot 
(Nomans-Land) and lettuce (Sharada) exceeding the US EPA’s safety threshold (HI > 1). Cr and Pb also significantly contributed to cumulative health risks. Root and leafy vegetables showed a higher propensity 
for metal accumulation, highlighting the influence of plant type and environmental exposure. The findings underscore the potential public health risks associated with the consumption of vegetables grown in 
contaminated urban and peri-urban environments. Routine monitoring and stricter control of anthropogenic pollution sources are recommended to safeguard food safety.