Methylmercury

Definitions

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

• Effect Of Mercury on Aquatic Ecosystems
• USGS Mercury Research Laboratory
• Mercury Research in the USGS
• Search the Toxic Substances Hydrology Program's Bibliography for "methylmercury"

USGS Information on Assessing Mercury Contamination

• Mercury Transport in the Carson River Basin
• Assessing Bottom Sediments as a Source of Mercury Contamination, Far West Reservoir, California
• Yolo Bypass Studies, Yolo Bypass, Sacramento, CA; Cache Creek, CA
• Mercury Cycling in the Everglades

USGS Fact Sheets on Mercury in the Environment

• Mercury Contamination of Aquatic Ecosystems: U.S. Geological Survey Fact Sheet FS-216-95
• Mercury in the Environment: U.S. Geological Survey Fact Sheet 146-00
• Mercury Contamination from Historic Gold Mining in California: U.S. Geological Survey Fact Sheet FS-061-00
• Are Walleye from Lake Roosevelt Contaminated with Mercury?: U.S. Geological Survey Fact Sheet FS-102-97
• Mercury Studies in the Florida Everglades: U.S. Geological Survey Fact Sheet FS-166-96
• Mercury and Selenium Poisoning: U.S. Geological Survey Fact Sheet 1999-15
• Environmental Geochemistry of Mercury Mines in Alaska: U.S. Geological Survey Fact Sheet FS-072-94

Mercury Headlines

• Clues to High Mercury Along the Gulf Coast
• Some Ecosystems will Respond to Reductions in Mercury Emissions
• Mercury from Yellowstone's Geysers
• Fish in Some Streams Accumulate Mercury
• A New Source of Methylmercury Entering the Pacific Ocean
• USGS Mobile Atmospheric Mercury Laboratory Makes an Impact
• National Fish Mercury Model Available On-Line
• OSTP Report on Methylmercury in the Gulf of Mexico
• Glacial Ice Cores Reveal the History of Global Mercury Contamination
• Mercury-Contaminated Fish--Is it Old or New Mercury?
• New Method for Assessing Bed Sediment Contamination

Mercury Toxicity Information

• ToxFAQs™ for Mercury, Frequently asked health questions about mercury from the Agency for Toxic Substances and Disease Registry (ATSDR)
• Toxicological Profile for Mercury, Agency for Toxic Substances and Disease Registry (ATSDR)
• Methylmercury (MeHg) (CASRN 22967-92-6), Integrated Risk Information System, U.S. Environmental Protection Agency
• Toxicological Effects of Methylmercury, National Academy Press

Other Mercury Information

• Mercury, Information from the U.S. Environmental Protection Agency
• Mercury and the Environment, Information from Environment Canada
• METAALICUS (Mercury Experiment To Assess Atmospheric Loading In Canada and the United)
• Evaluation of the Effectiveness of Remediation Dredging--The Fox River Deposit N Demonstration Project, Lower Fox River, near Kimberly, Wisconsin (pdf)

References

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.