Ecological and human health risk of metal contaminations in an impoundment impacted by wastewater effluents

Wastewater effluents have become a source of metals, particularly in rivers receiving effluents from wastewater treatment plants. The Shongweni Dam is an impoundment on the uMlazi River, which receives the water impacted by wastewater effluents. The dam is bordered by economically disadvantaged communities, which are opting for the inhabitant fish to supplement their protein needs. The present study aimed to investigate the response of fish to contamination and assess health risks that could be associated with the consumption of this fish. The water and sediment showed significant concentrations of metals, with the latter exhibiting a substantially high metal pollution index (MPI). Dry seasons exhibited relatively higher metal contamination indices, suggesting that the reduced water level resulted in high metal concentration. Cu, Mn, Fe, and Pb were the main drivers for high ecological risk on the overall metal contamination. Metals also showed significant concentrations in the muscle of the two fish species, with Cr and Pb exceeding the acceptable level for human consumption. The two species exhibited similar trends with regard to metal dispersion and MPI; however, no significant difference was observed for MPI between species. Nevertheless, Cr and Pb showed THQs of > 1, suggesting possible health implications for consumers, whereas the carcinogenic risk estimation for As, Cd, Cr and Pb showed that consumers remain at risk of cancer. These findings sensitize the communities residing near wastewater-polluted water bodies, particularly the Shongweni Dam, on the possible risk from consuming contaminated fish.