Human exposure to mercury and the accumulation of methylmercury that is associated with gold mining in the Amazon Basin, Brazil

In order to evaluate the extent of human exposure to mercury in the Amazon, in particular, in the Tapajos River basin, which is a site of extensive alluvial gold mining, we analyzed samples of human hair, blood and urine, as well as fish, collected from different areas for total levels of mercury and methylmercury. In fishing villages, the inhabitants were found to have accumulated mercury, mostly in the form of methylmercury, at abnormally high levels as the apparent result of consumption of local fish, with very little confounding exposure to inorganic mercury, including mercury vapor in the air. The people living near the main gold-mining areas had accumulated higher levels of methylmercury than people living far downstream from the gold-mining sites. Quite high levels of methylmercury were found in samples of hair from inhabitants of the fishing villages.