Levels of mercury in Nile tilapia (Oreochromis niloticus), water, and sediment in the Migori gold mining belt, Kenya, and the potential ramifications to human health

Abstract

Understanding mercury levels in gold mining areas where Background locals consume fish is important in evaluating the risk to the population. This study determined the levels of total mercury (T-Hg) in Nile tilapia, water, and sediment in the Migori gold mining belt and the potential risk to human health.: Water, sediment, and fish were sampled from 10 sites in Rongo Methods and Nyatike and analyzed for T-Hg using cold vapor atomic absorption spectroscopy. Geo-accumulation index (IGeo) was used to evaluate sediment quality, and the estimated daily intake of fish per meal (EDIm), the target hazard quotient (THQ), and the maximum allowable fish consumption rate (CRmw) were calculated as health risk indices.: Sediment from 6 sites were moderately polluted with T-Hg, while 2 Results sites were strongly polluted. Water from all the sites had T-Hg levels higher than the FAO recommended level for surface water. About 78% (38/49) of all tissues sampled had T-Hg levels above the 0.5 µg/g limit for consumption by the general human population. About 31% (15/49) of muscle tissues had T-Hg levels above the 0.5 µg/g limit, while 88% (43/49) of brain, 69% (34/49) of liver, and 69% (34/49) of muscle tissues had T-Hg levels above the 0.2 µg/g limit for consumption by at-risk groups. There were positive correlations between T-Hg levels in brain, muscle and pond sediment, T-Hg levels in brain and water pH and temperature, and negative correlations between T-Hg levels in brain and levels in water, T-Hg levels in brain and weight of fish. EDIm and THQ ranged from 2.43-15.84 µg/g and 24.3-158.4 µg/g wet weight respectively while CRmw ranged from 1-4 fish.: Consumption of Nile tilapia from the studied area carries a Conclusions significant risk of Hg exposure in frequent fish-eaters, pregnant women, and developing children, but is safe for the general population. Keywords