Abstract:
Second only to the agricultural industry, mining is often considered to be the largest source of pollution in most mineral-rich countries. Mine wastes and tailings commonly generate large concentrations of effluents containing high levels of potentially harmful elements (PHEs) which migrate into various compartments of the ecosystem with obvious undesirable health consequences. In this study, the concentrations of As Cd, Hg and Pb were determined on samples of soil, stream water and fish (Rastrineobola argentea) collected from the Migori Gold Belt (MGB) in Kenya. Maximum total concentrations of Cd, Pb, As and Hg recorded in some samples in the study area were found to be far above the World Health Organization (WHO) and the Food and Agriculture Organisation (FAO) maximum allowable concentrations (MAC), respectively, including some from the control site, 150 km away from the MGB. The calculated geometric means showed that the PHE concentrations were significantly above MAC levels (p b 0.05) in the three sample types.
The PHE concentrations were as follows: in water, Cd: 1.5–10.5 μg l−1, Pb: 0.4–13.1 μg l−1, As: 0.06–23.0 μg l−1, and Hg: 0.36–52.1 μg l−1; in soil, Cd: 4.5–570 mg kg−1, Pb: 5.9–619 mg kg−1, As: 0.08–86.0 mg kg−1, and Hg:0.51–1830 mg kg−1; and in fish; Cd, 1.9–10.1 mg kg−1, Pb: 2.0–13.1 mg kg−1, As: 0.02–1.92 mg kg−1, and Hg: 0.26–355 mg kg−1. Concentrations of PHEs were much higher in the area affected by gold mining area than at point S4 which was sampled for comparison and was 70 km away from the gold mining area. We conclude that gold mining and other human activities in the MGB have led to the release of toxic levels of Cd, Pb, As and Hg, which may lead to serious environmental health consequences in humans. We recommend that the public health sector addresses in a timely fashion, these sources of contamination (gold mining and associated human activities), in order to obviate impending health problems.
