Metal accummulation in Labeo umbratus (Smith, 1841) collected from the Vaal Dam and human health risks

The Vaal Dam is one of the largest dams in South Africa, located between the Gauteng Province and Orange Free state, and supplies water to approximately 11.6 million people. Recreational and small scale subsistence fishing... [ view full abstract ]

The Vaal Dam is one of the largest dams in South Africa, located between the Gauteng Province and Orange Free state, and supplies water to approximately 11.6 million people. Recreational and small scale subsistence fishing activities have been noted for the dam along with consumption of fish by local people. Labeo umbratus (moggel) was collected from the Vaal Dam and muscle, liver, kidney, gill and spinal cord samples were obtained post mortem and frozen. Defrosted samples were weighed, dried and digested for analysis of 19 trace elements by Inductively Coupled Plasma – Mass Spectrometer (ICP-MS). Metals in the muscle tissue were lower compared to other organs analysed. The levels of As, Co, Cr, Cu, Fe, Se, Sr and Zn in muscle tissue were above guidelines recommended by the USEPA, with Zn being highest at 31.5 mg/kg (dw). Calculated target hazard quotients indicated that there is a risk of exposure to As (1.46) for humans consuming L. umbratus muscle tissue, whereas, no risk was found for the other elements analysed. The total health hazard index (HI) for moggle, however, did indicate that there is an overall health risk to humans consuming muscle tissue from this fish species. It has consistently been shown that trace elements in the water of the Vaal Dam are below guidelines set out in government legislation for aquatic ecosystems and aquaculture conditions. However, studies detailing the accumulation of metals by fish inhabiting the dam have indicated that elements in muscle tissue are above food safety guidelines set out by the USEPA. Comparison of the HI between benthic and pelagic fish species from the dam indicates greater health risks are associated with the consumption of the former group of fish.