Mining is one of the major sources of heavy metals in most developing countries and this has become a major health concern to the populace due to the possibility of food contamination with these heavy metals. We investigated the levels of titanium (Ti), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb), rubidium (Rb), strontium (Sr), selenium (Se), niobium (Nb) and vanadium (V) in 64 soil and 320 samples of regularly consumed staple food crops and vegetables (cassava tubers, white yam, groundnut seed, fluted pumpkin leaf and Z. zanthoxyloides from farms around Enyigba mining sites in Ebonyi State and the possible health risks due to consumption of these staple foods. Energy dispersive X-ray fluorescence (EDXRF) was used in determination of the metals in the samples respectively. The mean levels of the metals except Mn, Pb and Zn were below the threshold limits for agricultural soils. Our data also showed that food crops cultivated around this sites bio-accumulated toxic levels of these metals above the recommended legal limits set by WHO, NAFDAC and CODEX especially Pb, Zn, Cu, Ni, Se, and Rb. This perhaps may have potential health implication on the local dwellers. The estimated daily intakes (EDI) of the toxic metals through the consumption of the crop samples were below the maximum tolerable daily intake (MTDI) except lead and nickel by eating of groundnut, cassava and yam. Furthermore, the target hazard quotient (THQ), computed based on EDI of the heavy metals were above unity for the metals due to cassava, yam and groundnut consumption, suggesting significant health risk. Raised amounts of heavy metal in cassava and groundnut samples as revealed by their metal extraction coefficient computed in this study hint that they may be used as bio-indicators of ecological, health hazards and phytoremediators of Mn, Zn, Cu, and Pb.
Heavy metals in food crops: Health risks, fate, mechanisms, and management