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Archive for August 20th, 2009

Mercury Found in Every Fish Tested in the US

Posted by feww on August 20, 2009

“as mad as a hatter” syndrome, now a deadly US reality

Researchers Found Mercury Contamination in Every Fish Sampled in 291 Streams Across the United States: USGS

Since 1980, the amount of mercury in the atmosphere has risen by about 56 percent, our colleagues at EDRO have estimated.

Mercury contamination in quarter of the samples tested  exceeded “the criterion for the protection of people who consume average amounts of fish, established by the U.S. Environmental Protection Agency.”  And nearly 70 percent  of the fish exceeded the U.S. EPA safety level for fish-eating mammals.

Mercury levels in fish are determined by (1) mercury sources, such as atmospheric emissions from burning coal; (2) methylation efficiency, which is controlled by certain biological, chemical, and environmental characteristics; and (3) food-web complexity, the totality of feeding interactions—from algae to predatory fish—in an ecological community. USGS

“This study shows just how widespread mercury pollution has become in our air, watersheds, and many of our fish in freshwater streams,” said Secretary of the Interior Ken Salazar. “This science sends a clear message that our country must continue to confront pollution, restore our nation’s waterways, and protect the public from potential health dangers.”

Mercury contamination is widespread globally, originating from natural and human-related sources, including air transport from coal combustion, waste incineration, and mining. (Photograph by Phillip J. Redman, U.S. Geological Survey). Caption USGS.

Mercury is released to the environment from natural and anthropogenic sources. Volcanoes,  natural mercury deposits, and volatilization from the ocean are among the main natural sources. The main anthropogenic sources include: coal combustion, chlorine alkali processing, waste incineration, and metal processing [gold and mercury mining.] USGS estimates that human activities have about tripled the amount of mercury in the atmosphere, and that “the atmospheric burden is increasing by about 1.5 percent per year.”  [Source EDRO based on USGS data. ]

“Some of the highest levels of mercury in fish were found in the tea-colored or “blackwater” streams in North and South Carolina, Georgia, Florida and Louisiana — areas associated with relatively undeveloped forested watersheds containing abundant wetlands compared to the rest of the country. High levels of mercury in fish also were found in relatively undeveloped watersheds in the Northeast and the Upper Midwest. Elevated levels are noted in areas of the Western United States affected by mining. ” US Department of interior said.

Studies of sediment cores show that younger sediments deposited since industrialization have mercury concentrations that are [up to] 5 times that of historical sediments. Thus, the fact that these sediments are primarily composed of dead microorganisms that were once the bottom of the food chain would suggest that modern levels of mercury in the food chain are elevated over preindustrial times. USGS.

aquatic mercury cycle
Mercury cycling pathways in aquatic environments are very complex. The various forms of mercury can be converted from one to the next; most important is the conversion to methylmercury (CH3Hg+), the most toxic form. Ultimately, mercury ends up in the sediments, fish and wildlife, or evades back to the atmosphere by volatilization. Reprinted with permission from Mercury Pollution: Integration and Synthesis. Copyright Lewis Publishers, an imprint of CRC Press.

For a US listing of fish advisories from the Environmental Protection click here.

mercury pie

Combustion from coal-fired utilities and industrial boilers accounts for more than 85 percent of the transmission of inorganic mercury to the atmosphere (U.S. Environmental Protection Agency, 1997). USGS findings will provide a better understanding of what drives methylation of inorganic mercury in certain environmental settings, and thereby help to clarify appropriate strategies regarding mercury emissions. Pie chart and caption USGS

“This study improves our understanding of where mercury ends up in fish in freshwater streams,” said USGS scientist Barbara Scudder. “The findings are critical for decision-makers to effectively manage mercury sources and to better anticipate concentrations of mercury and methylmercury in unstudied streams in comparable environmental settings.”

The USGS study included testing for “mercury contamination in fish, bed sediment and water from 291 streams” across the country, spanning over an 8-year from 1998 to 2005.

USGS found that “coal-fired power plants are the largest source of mercury emissions in the United States.” Additionally, 59 of the streams sampled were also “potentially affected by gold and mercury mining.”

Why study mercury?

Mercury can adversely affect humans and wildlife through consumption of contaminated fish, particularly by sensitive individuals, such as children and women of childbearing age. Mercury is currently the leading cause of impairment in the Nation’s estuaries and lakes and was cited in nearly 80 percent of fish-consumption advisories (2,242 of 2,838) reported by states in 2000. The geographic extent of mercury advisories covers more than 10 million acres of lakes and more than 400,000 stream miles—increases of about 7 and 48 percent, respectively, over advisories reported in 1998 (U.S. Environmental Protection Agency, 2002a).

Facts about mercury:

  • Highly toxic to the nervous system
  • Persistent in the environment
  • Bioaccumulates (higher concentrations in tissues of aquatic plants and animals than in water)
  • Biomagnifies (higher concentrations at increasingly higher levels in the food chain)
  • Numerous chemical forms in air, water, sediment, and biota
  • Responsible for nearly 80 percent of U.S. fish-consumption advisories

Mercury Cycle links:

Water Pollution and Related Links:

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