Heavy metal contamination in vegetables and associated health risks

Bioaccumulation of heavy metals in vegetables poses an enormous health risk to humans. This study assessed the heavy metal contents (Pb, Cr, Cd and Zn) in soils, irrigation water and vegetables using the atomic absorption spectrophotometer. The health risk associated with ingestion of these vegetables (spring onions, lettuce and cabbage) was also evaluated through non-carcinogenic and carcinogenic risk indices. The results revealed that the individual heavy metal concentrations in the soils, irrigation water and vegetables were below the standard limits set by FAO/WHO. The order of the vegetables based on their total heavy metal contents was cabbage (39.30 mg/kg) < spring onion (42.74 mg/kg) < lettuce (83.71 mg/kg). Lettuce, with the highest transfer factor of 1.47 was seen as a hyperaccumulator. Based on the hazard index, the order of the non-carcinogenic health risk posed by the heavy metals occurred as Cr > Zn > Cd > Pb with chromium being the most threatening heavy metal. Values of the total cancer risk index indicated that children were at a greater risk of cancer than adults. The findings from this study necessitate the development and implementation of mitigation measures to ensure food safety and protection of human health.