Heavy metal contamination of some vegetables from pesticides and the potential health risk in Bauchi, northern Nigeria

Vegetable farming in developing countries is characterized by the indiscriminate application of pesticides and the resultant pollution of agricultural soil with heavy metals that form constituents of these pesticides. These heavy metals have long term toxicity to human and other biota in the ecosystem. This problem is exacerbated by lack of monitoring to regulate  the excessive use of pesticides. The objective of this study was to determine the presence and concentration of some heavy metals in pepper, tomato and onion grown in pesticide contaminated farm and the human health risk associated with their consumption. Pepper ( Capsicum annuum ), Tomato ( Solanum lycopersicum ) and Onion ( Allium cepa ) and their corresponding soils were collected from three vegetable farms. The concentrations of Pb, As, Cd, Cr and Zn in the plants and soil were determined. The potential health risk from the consumption of these vegetables was assessed using the methods developed by World Health Organization (WHO) and Food and Agricultural Organization (FAO). Results obtained showed presence of heavy metals (Pb, As, Cd, Cr and Zn) Sin different parts of the plants and at different concentrations, with some above the WHO/FAO permissible limits. The edible part of these vegetables (fruits) had the least mean contents of all heavy metals while roots recorded the highest mean concentration. All vegetables were found to be hyper accumulators of Cd and Cr. The Hazard Index (HI) of heavy metal contamination in these vegetables suggested a potential human health risk. The need by government for monitoring and regulation of pesticides application needs urgent attention. Keywords: Vegetables, pesticides, heavy metals, health risk, toxicity