Mercury Contamination in Forest and Freshwater Ecosystems in the Northeastern United States

M (Hg) is a potent neurotoxin of significant ecological and public health concern. Human and wildlife exposure to Hg occurs largely through the consumption of contaminated fish. It is estimated that over 410,000 children born each year in the United States are exposed in the womb to methylmercury (MeHg) levels that are associated with impaired neurological development (Mahaffey 2005). Eight percent of US women of childbearing age have blood Hg levels in excess of values deemed safe by the US Environmental Protection Agency (USEPA; Schober et al. 2003). Studies have also linked elevated Hg in the blood or tissue of fish, birds, and mammals with negative effects such as reduced reproductive success, hormonal changes, and motor skill impairment (Wiener and Spry 1996, Nocera and Taylor 1998, Evers et al. 2004). To protect human health, the USEPA set a fish tissue criterion for MeHg at 0.3 μg per g under section 304(a) of the Clean Water Act (USEPA 2001). Similar criteria for wildlife are under development or promulgation in several states (e.g., Maine, New York). As of 2004, fish consumption advisories regarding Hg contamination have been issued for 44 states, including 21 statewide advisories for fresh waters and 12 for coastal waters. These advisories represent more than 53,000 km2 of lakes and 1,230,000 km of rivers. The extent of fish consumption advisories underscores the extensive human and ecological health risk posed by Hg pollution. Important sources of Hg to the environment include electric utilities, incinerators, industrial manufacturing, wastewater treatment plants, and improper disposal of consumer products (e.g., batteries, fluorescent light bulbs, Hg switches). Considerable public policy attention is directed toward airborne Hg emissions, since they constitute the largest source