Mercury in the Amazon.

Release and spreading of mercury from gold mining is a widespread problem in the Amazon area. Today we have rather good knowledge of the mercury situation. Tens of investigations have considered mainly concentrations in fish and human hair. Metallic mercury is used for amalgamation of gold, and the mercury is released by evaporation at reburning sites. The first extraction (burning) is performed in the field at the garimpos and the second (reburning) in gold shops in towns. This practice may cause severe exposure to elemental mercury by inhalation for people working with gold purification. Mercury is also released in substantial amounts to rivers and lakes. This mercury may be bioaccumulated as methylmercury in aquatic food chains. Predatory fish often contain mercury in concentrations that far exceed the safety norms in Brazil. As many people eat fish daily, there is a high exposure to methylmercury. Neurological disorders have been found in exposed persons. Methylmercury concentrations in hair are often at levels that may cause clinical symptoms of Minamata disease. The greatest health hazard index values have been estimated for people eating contaminated fish.