Assessment of Potential Human Health Risks Associated with Heavy Metals in Fish from Loskop Dam of the Olifants River System, South Africa

The Loskop Dam is one of the major reservoirs on the Olifants River in South Africa. The study was conducted to determine the accumulation of As, Cd, Cr, Fe, Hg, Pb, Mn, Ni, Cu and Zn in the muscle tissue of three edible fish species, Oreochromis mossambicus, Clarias gariepinus and Labeo rosae, from the Loskop Dam and the potential health risk of consuming these fish. Heavy metal concentrations varied among the fish species and seasons. Higher metal concentrations were found in C. gariepinus during winter than in summer, while O. mossambicus and L. rosae had higher metal concentrations in summer than in winter. The arsenic concentration exceeded the international guideline limit in O. mossambicus during winter and summer, while the Mn levels in C. gariepinus, O. mossambicus and L. rosae exceeded the permissible limit during the summer season. The potential human health risk assessment showed that the average daily dose (ADD) values were below the respective reference doses (RfDs), except for As in O. mossambiccus, which exceeded its RfD. Target hazard quotients (THQs) were <1, indicating that consumption of the fish species from the dam does not pose a potential non-carcinogenic health risk, except for As. The hazard index (HI) estimations showed a potential non-cancer risk for O. mossambicus during both seasons. Furthermore, the potential cancer risks (CRs) associated with daily exposure indicated that individuals who consume O. mossambicus, L. rosae and C. gariepinus during both seasons may be at risk of carcinogenic effects due to exposure to As, and all the three species due to exposure to Ni. The results underscore the need for effective measures to prevent and mitigate future heavy metal contamination in the dam, not only to conserve the ecosystem but also to protect the well-being of local communities that consume fish from the dam. Implementing these measures would contribute to achieving United Nations sustainable development goals (SDGs) 2, 3 and 6.