Assessment of human health risks and pollution index for heavy metals in farmlands irrigated by effluents of stabilization ponds.

Areas contaminated with heavy metals can pose major risks to human health and ecological environments. The aims of this study are to assess human health risk and pollution index for heavy metals in agricultural soils irrigated by effluents of stabilization ponds in Birjand, Iran. The results revealed that the levels of Cr, Mn, Zn, Fe, Cu, Cd, and Pb were in range of 70.3-149.65, 355-570, 31.15-98.45, 23,925-29,140, 22.75-25.95, 0.17-6.51, and 8.5-23.5 mg/kg in topsoils, respectively. Total hazard index values from heavy metals through three exposure routes for adults and children were 9.13E-01 and 1.10, respectively, indicating that there was non-carcinogenic risk for children. The total risk of carcinogenic metals (Cr, Cd, and Pb) through the three exposure routes for adults and children was 1.06E-04 and 9.76E-04, respectively, which indicates that the metals in the soil will not induce carcinogenic risks to these age groups. Pollution levels of heavy metals in soil samples including enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geo-accumulation index (Igeo) showed heavy metal contamination of agricultural soils. The results of the present study provide basic information about heavy metal contamination control and human health risk assessment management in the study area.