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Environmental Health - Toxic Substances



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Methylmercury - "CH3Hg+, organic form of mercury and the form of mercury that is most easily bioaccumulated in organisms; a neurotoxin." - Griesbauer, 2007

Methylmercury - "Most mercury in fish is methylmercury, a highly toxic substance that can build up in predatory fish ... Methylmercury bioaccumulates (is accumulated within organisms faster than it's eliminated) and biomagnifies (increases in concentration as it travels up the food chain)." - Erwin and Munn, 1997

Methylmercury - "Methylmercury (MeHg), one organic form of Hg, can accumulate up the food chain in aquatic systems and lead to high concentrations of MeHg in predatory fish, which, when consumed by humans, can result in an increased risk of adverse effects in highly exposed or sensitive populations. Consumption of contaminated fish is the major source of human exposure to MeHg in the United States." - National Research Council, 2000

Methylmercury - "Mercury occurs in several different geochemical forms, including elemental mercury [Hg(0)], ionic (or oxidized) mercury [Hg(II)], and a suite of organic forms, the most important of which is methylmercury (CH3Hg+). Methylmercury is the form most readily incorporated into biological tissues and most toxic to humans. The transformation from elemental mercury to methylmercury is a complex biogeochemical process that requires at least two steps: (1) Oxidation of Hg(0) to Hg(II), followed by (2) Transformation from Hg(II) to CH3Hg+; step '2' is referred to as methylation." - Alpers and Hunerlach, 2000

Methylmercury - "The conversion of inorganic mercury to methylmercury is important for two reasons: (1) methylmercury is much more toxic than inorganic mercury, and (2) organisms require considerably longer to eliminate methylmercury. At this point, the methylmercury-containing bacteria may be consumed by the next higher level in the food chain, or the bacteria may release the methylmercury to the water where it can quickly adsorb to plankton, which are also consumed by the next level in the food chain." - Krabbenhoft and Rickert, 2009

Text in brackets ("[text]") are additions by the editor.

USGS Information on Mercury in the Environment

USGS Information on Assessing Mercury Contamination

USGS Fact Sheets on Mercury in the Environment

Related Science Feature Articles

Mercury Toxicity Information

Other Mercury Information


Alpers, C.N., and Hunerlach, M.P., 2000, Mercury contamination from historic gold mining in California: U.S. Geological Survey Fact Sheet FS-061-00.

Erwin, M.L., and Munn, M.D., 1997, Are walleye from Lake Roosevelt contaminated with mercury?: U.S. Geological Survey Fact Sheet FS-102-97.

Griesbauer, L., 2007, Methylmercury contamination in fish and shellfish: CSA Discovery Guides, access date June 1, 2011.

Krabbenhoft, D.P., and Rickert, D.A., 2009, Mercury contamination of aquatic ecosystems: U.S. Geological Survey Fact Sheet FS-216-95.

National Research Council, 2000, Toxicological effects of methylmercury: Washington, D.C., National Academies Press, 368 p.


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