Assessment of the human health risks of heavy metals in nine typical areas.

Human health risks of five different heavy metals were assessed in nine typical areas in Asia, Europe, and Africa. The geoaccumulation index (I _geo ) of arsenic (As) in Hyderabad (HB), cadmium (Cd) in Veles (VL), and lead (Pb) in Murcia (MC) were found to be 5, indicating extreme contamination. This is related to their high concentrations in soil. The concentration of As in wheat in Niger Delta (ND) and European Union (EU) areas were 3.3 and 2.55 mg/kg, which were 22 and 17 times respectively of the World Health Organization (WHO)/Food and Agriculture Organization (FAO) criteria. In general, the concentrations of heavy metals in wheats were higher than those in corns, indicating that heavy metals were easier to accumulate in wheats than in corns. The human risks induced by the carcinogenic metals As and Cd were much higher than those induced by noncarcinogenic metals in different exposure ways. The human health risks of heavy metals in different exposure ways were R _w-ing  > R _c-ing  > R _s-ing  > R _s-der  > R _s-inh . The human health risks induced by wheat ingestion for adults and children accounted for 67.75-97.52% and 69.52-98.04%, respectively, of the total human health risks. The total human health risks in the VL and MC areas were 1.58 × 10 ^-4 a ^-1 and 1.3 × 10 ^-4 a ^-1 for adults and 1.14 × 10 ^-4 a ^-1 and 9.47 × 10 ^-5 a ^-1 for children, respectively, which were significantly high according to the Environmental Protection Agency and International Commission on Radiological Protection. The ranking of the total human health risks in different areas were R _VL  > R _MC  > R _ND  > R _EU  > R _HB  > R _KY  > R _TB  > R _MLV  > R _NHM . The total human health risks of adults were higher than those of children.