Heavy metal concentrations in sediments and Cyprinus carpio from Maqalika Reservoir –Maseru, Lesotho: An analysis of potential health risks to Fish consumers

The determination of heavy metal contaminants in fish is very important in monitoring health risks to humans who consume them. This study assessed the concentration of heavy metals (As, Pb and Zn) in sediments and gills of Common Carp fish (Cyprinus carpio) from Maqalika Reservoir in Maseru, Lesotho and their potential health risks to such fish consumers. Sediment and Cyprinus carpio samples were collected from upstream, midstream and downstream sites of Maqalika Reservoir and examined for As, Pb and Zn using atomic absorption spectrometer. Potential health risks were based on comparing the derived metal concentrations in gills of Cyprinus carpio with the World Health Organization (WHO) permissible limits for human consumption. The mean concentration levels of Zn, As and Pb in sediment were in the order: 78.5; 2.34; and 0.29 mg/kg respectively. In the gills of Cyprinus carpio the mean concentration levels were in the order 7.85; 1.29; and 0.33 mg/kg for Zn, As and Pb respectively. The magnitude of concentration of Zn, As and Pb by location in the reservoir varied spatially in the order of downstream > midstream > upstream in both sediment and gills of Cyprinus carpio. Significant differences (p < 0.05) in metal concentrations between upstream and downstream sites of the reservoir were observed. The metals concentration in gills of Cyprinus carpio were lower than those in sediments, but positively and significantly correlated (P < 0.05). As and Pb concentration levels in the gills of Cyprinus carpio were higher than the WHO permissible limits recommended for fish consumption of 1 mg/kg and 0.2 mg/kg respectively, suggesting that residents could experience significant health risks from the intake of individual metals through fish consumption. Measures should be taken to reduce heavy metal concentrations in sediment and Cyprinus carpio exposure in the general population in order to minimize the risk of human health adverse effects.