Assessment of human health risks through the consumption of mercury contaminated fish from gold and platinum mining areas

Mining activities can pollute freshwater systems with toxic contaminants that can damage the environment and cause risks to human health. In South Africa, mercury is a contaminant of major concern due to it being released into the environment through artisanal gold mining and the coal combustion process at power stations. Mercury accumulates in the liver and more importantly the muscle tissue of fish. Mercury can then be transferred to humans through the consumption of contaminated fish and can affect the nervous system and cause permanent damage. Although South Africa is a major contributor to global mercury emissions, there are very few papers published on mercury concentrations and the risks to human health associated with consuming contaminated fish. This study aimed to determine the mercury concentrations in environmental matrices (water, sediment and two fish species (Cyprinus carpio and Clarias gariepinus)) from five sites and determine the risks to human health associated with the consumption of these fish. The mercury concentrations in muscle and liver tissues of C. carpio (1.2 and 0.8 mg/kg) and C. gariepinus (1.6 and 0.9 mg/kg) from Boskop Dam were the highest across all sites. Clarias gariepinus had higher mercury concentrations and a higher risk to human health compared to C. carpio across all sites. Both species from Boskop Dam and the Vaal River, while C. gariepinus from Olifantsnek and Modder Dam all had a hazard quotient of > 1 which shows these fish had a high possibility for adverse health effects to humans.