Human health aspects of certain metals in tissue of the African sharptooth catfish, Clarias gariepinus, kept in treated sewage effluent and the Krugersdrift Dam [South Africa]: Chromium and mercury

Health risks associated with the use of wastewater for fish production were evaluated by investigating the possible bioaccumulation of chromium and mercury in the muscle tissue, kidney and liver of Sharptooth catfish (Clarias gariepinus) kept in sewage effluent from a biofilter plant and in the waters of the Krugersdrift dam. Metal concentrations were determined in the sediment and water at these locations. After appropriate preparation, the metals were analysed by atomic absorption spectrophotometry. Chromium concentrations were negligible in both waters until the second half of the year when peaks up to 0.05 mg chromium per litre were measured. Mercury concentrations were below 0.001 mg per litre, the level of detection. Mercury accumulated most in the muscle tissue to a maximal of 0.50 ug per g wet weight. Chromium levels never exceeded 0.2 mg per g wet weight in muscle but liver and kidney concentrations were approximately 4 times this amount. There was some risk in the consumption of fish from both habitats and the levels in livers and kidney could be a threat to human health. There are 47 references. (see also preceding abstract).