Heavy Metal Contamination of Vegetables Irrigated with Borehole Water in Kaduna State

Urban vegetable farming using borehole irrigation is increasingly common in peri-urban areas of Kaduna State, where seasonal water scarcity drives year-round cultivation of leafy vegetables consumed by the local population. However, the potential accumulation of heavy metals in these vegetables from contaminated water sources poses a food safety concern that requires systematic documentation. This study determines the concentrations of lead, cadmium, zinc, copper, iron, and nickel in borehole irrigation water and three vegetables, spinach, tomato, and lettuce, grown on irrigated farms in Chikun LGA, Kaduna State. Water and plant samples were digested using standard wet acid digestion procedures and analyzed by atomic absorption spectrophotometry. Results reveal that lead concentrations in spinach and lettuce samples exceeded the maximum permissible limits set by the World Health Organization and the Codex Alimentarius Commission. Cadmium levels in all three vegetables exceeded WHO thresholds for leafy vegetables. Borehole water lead concentrations were above WHO drinking water guidelines, suggesting that the contamination pathway originates from groundwater sources likely influenced by nearby industrial and domestic waste activities. Bio-concentration factors calculated for each metal indicate a high accumulation potential for lead and cadmium in leafy vegetables. The health risk assessment suggests that regular consumers of these vegetables face elevated non-carcinogenic risk. Urgent policy action is recommended to monitor and regulate peri-urban irrigation water quality in Kaduna State. Keywords: heavy metals, vegetable contamination, borehole irrigation, Kaduna State, food safety.