GOLD MINING can severely damage the environment and may pose a hazard to human health, both by introducing contaminants from the mining process and by enhancing concentrations of naturally present minerals. Traditional industrial methods for processing gold ore use mercury to separate gold from crushed rock, with consequent release of mercury into the surrounding air, tailings, soil, sediment, and water. (1) In developing countries, artisanal miners extract gold by a process that involves burning off elemental mercury to isolate gold from a gold-mercury amalgam. Once in the environment, mercury persists. (2) Among naturally present minerals, elevated arsenic concentrations are also found in surface water and sediment in gold mining watersheds, (3,4) and have been found in surface soil as far as 13 km from gold mining sites. (5)

This investigation focused on 2 toxic metals of health concern--mercury and arsenic--in Siuna, a small town at the hub of "Las Minas," a gold mining area in remote north-Atlantic Nicaragua. Gold mining began in Siuna in the 1890s, was fully mechanized by the 1930s, and continued on an industrial scale until the mine closed in 1987. By that time, the hill at the center of Siuna had become a deep pit, which filled with groundwater to form an approximately 15-acre lake. From the 1930s to the 1980s, the mine produced a tailings heap more than 1 km long, 0.3 km wide, and approximately 10 m deep. Waste water containing mercury and cyanide was released into a stream along the tailings known as El Cianuro (The Cyanide), which joins with a river commonly used for washing and bathing. Since the closure of the mine, many unemployed miners have turned to artisanal mining, locally known as guiriseria. The owner of the mine concession commissioned an environmental impact study in the 1990s, but no data were publicly released regarding heavy metal concentrations in Siuna. To our knowledge, the extent of human exposure to potential mining contaminants has not been investigated in Siuna. Therefore, we conducted an environmental assessment of mercury and arsenic in drinking water and soil samples in relation to the mining site, and evaluated the extent of human uptake by examining levels of these metals in fingernail tissue as a biologic marker of internal dose of exposure. This approach has been used elsewhere to assess metal exposure in adults, (6,7) but data for children are extremely limited. Therefore, we specifically examined the association between fingernail concentrations and potential sources of mercury and arsenic exposure according to age, as well as other factors.