Heavy metal contamination in soils and stream water in Tungabhadra basin, Karnataka: environmental and health risk assessment

Surface soils and stream water samples were collected from parts of Tungabhadra River basin, Karnataka to assess heavy metal (Cr, Pb, Ni, Co, Cu, Cd and Zn) contamination and effects on the environment and human health. The geo-accumulation index (- 1.79 to 3.7) and ecological risk index (18.74-207.47) indicated negligible to heavy contamination and low to moderate ecological risk. The sequence of non-carcinogenic (NCR) and carcinogenic risk (CR) is ingestion > dermal > inhalation in soils and ingestion > dermal in water samples. The hazard index (HI) in soil and water is < 1, indicating no NCRs for adults and children. However, three soil samples showed HI > 1 for As in children. In water samples, two samples showed HI > 1 for As in adults and about 50% of water samples showed HI > 1 for As in children, which is due to more exposure of children to arsenic contamination as compared to the adults. For adults, total carcinogenic risk (TCR) of Pb was below the recommended limit of 1 x 10(-6). The TCR of As and Cr in adults and Pb in children were found within the range of 10(-6) < CR <= 10(-4), indicating lower carcinogenic risk. However, TCR of As and Cr in children were exceeding the threshold limits of 1 x 10(-4), indicating significant carcinogenic effects. In water samples, TCR of As and Cd was higher than the threshold limits of 1 x 10(-4), indicating significant carcinogenic risk for both adults and children. The study provides the background levels of pollutants in soil and water, which will help to develop regional sediment and water quality guidelines.