Human exposure to mercury in artisanal small-scale gold mining areas of Kedougou region, Senegal, as a function of occupational activity and fish consumption
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We investigated mercury (Hg) exposure of food web and humans in the region of Kedougou, Senegal, where Hg is used for gold amalgamation in artisanal small-scale gold mining (ASGM). For this purpose, total mercury (THg) concentration was determined in eight fish species and two shellfish species from Gambia River and in human hair from 111 volunteers of different age and sex, living in urban locations (Kedougou and Samekouta) or in ASGM areas (Tinkoto and Bantako). THg concentrations in fish samples range from 0.03 to 0.51 mg kg−1 wet weight (ww) and 0.5 to 1.05 mg kg−1 ww for shellfish. THg concentrations in fish are below the WHO guideline of 0.5 mg kg−1 ww, whereas 100 % of shellfish are above this safety guideline. In the entire set of fish and shellfish samples, we documented a decrease of THg concentrations with increasing selenium to mercury (Se:Hg) ratio suggesting a protection of Se against Hg. However, local population consuming fish from the Gambia River in the two ASGM areas have higher THg concentrations (median = 1.45 and 1.5 mg kg−1 at Bantako and Tinkoto) in hair than those from others localities (median = 0.42 and 0.32 mg kg−1 at Kedougou town and Samekouta) who have diverse diets. At ASGM sites, about 30 % of the local population present Hg concentrations in hair exceeding 1 mg kg−1, defined as the reference concentration of Hg in hair. We also evidence a higher exposure of women to Hg in the Tinkoto ASGM site due to the traditional distribution of daily tasks where women are more involved in the burning of amalgams. The discrepancy between the calculated moderate exposure through fish consumption and the high Hg concentrations measured in hair suggest that fish consumption is not the only source of Hg exposure and that further studies should focus on direct exposure to elemental Hg of population living at ASGM sites.
KeywordsArtisanal gold mining Mercury Methylmercury Selenium Fish Human health risk
The authors thank the Lombard Foundation (Geneva, Switzerland), Schmidheiny Foundation (Geneva, Switzerland) and Sida-UNESCO project 503RAF2000 for financing the study; and the Geological Survey of Senegal (DMG), University Cheikh Anta Diop (Dakar), Dr Diongue and the team of Kedougou hospital and RandGold Company Senegal for their logistic help; and Dr Sarr of the Animal Biology Department at the University Cheikh Anta Diop for fish identification.
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