Human exposure to mercury in artisanal small-scale gold mining areas of Kedougou region, Senegal, as a function of occupational activity and fish consumption

Abstract

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.

Senegalese artisanal gold mining leads to elevated total mercury and methylmercury concentrations in soils, sediments, and rivers

“…This Hg can also bioaccumulate across the food chain, resulting in high concentrations of Hg in piscivorous fish [Driscoll et al, 2007]. High concentrations of Hg in fish near ASGM in Senegal have been correlated with high concentrations of Hg in human hair, a biomarker for MeHg exposure, resulting in concentrations of Hg that exceed the US EPA recommended threshold [Niane et al, 2015].…”

“…The Senegalese Sabodala Deposit is the largest deposit in West Africa, extending over a 230 km 2 region and estimated to contain over 30 tons of gold [Savornin et al, 2007;Niane et al, 2015]. The geological composition of the Sabodala Deposit represents that of the Greenstone Gold Belt, which extends further into West Africa and contains over 400 tons of gold [Bassot, 1997].…”

Influence of human disturbance on Western Chimpanzee (Pan troglodytes verus) nesting behavior in a savanna mosaic habitat, southeastern Senegal

“…Mercury is one of the main toxic metals that are found in an aquatic environment, especially in the form of methylmercury (MeHg) (Niane et al, 2015). This is because of its ability to biomagnify, or increase in concentration, in the food chain (Niane et al, 2015).…”

“…Mercury is one of the main toxic metals that are found in an aquatic environment, especially in the form of methylmercury (MeHg) (Niane et al, 2015). This is because of its ability to biomagnify, or increase in concentration, in the food chain (Niane et al, 2015). The bioaccumulation and biomagnification properties of Hg along the food chain make it a dangerous element, especially in aquatic systems (Niane et al, 2014).…”

“…Areas with ASGM, such as Amazonia, China, and east Africa, have exhibited health risks for local populations that consume fish contaminated with mercury (Niane et al, 2014). Consumption of aquatic food is the main way humans are exposed to Hg, although it can also be inhaled as a gas in its elemental form (Niane et al, 2015). Humans along the Gambia River, at ASGM sites, who consume fish were found to have high levels of THg in their hair, compared to those from other locations (Niane et al, 2015).…”