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Fate and Transport and Ecological Effects of Mercury

Mercury in the air may settle into water bodies and affect water quality. This airborne mercury can fall to the ground in raindrops, in dust, or simply due to gravity (known as “air deposition”). After the mercury falls, it can end up in streams, lakes, or estuaries, where it can be transferred to methylmercury through microbial activity. Methylmercury accumulates in fish at levels that may harm the fish and the other animals that eat them. Mercury deposition in a given area depends on mercury emitted from local, regional, national, and international sources. The amount of methylmercury in fish in different waterbodies is a function of a number of factors, including the amount of mercury deposited from the atmosphere, local non-air releases of mercury, naturally occurring mercury in soils, the physical, biological, and chemical properties of different waterbodies and the age, size and types of food the fish eats. This explains why fish from lakes with similar local sources of methylmercury can have significantly different methylmercury concentrations.

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Birds and mammals that eat fish are more exposed to methylmercury than any other animals in water ecosystems. Similarly, predators that eat fish-eating animals are at risk. Methylmercury has been found in eagles, otters, and endangered Florida panthers. Analyses conducted for the Mercury Study Report to Congress suggest that some highly-exposed wildlife species are being harmed by methylmercury. Effects of methylmercury exposure on wildlife can include mortality (death), reduced fertility, slower growth and development and abnormal behavior that affects survival, depending on the level of exposure. In addition, research indicates that the endocrine system of fish, which plays an important role in fish development and reproduction, may be altered by the levels of methylmercury found in the environment.

Total Mercury Wet Deposition, 2003

The Mercury Deposition Network (MDN) monitors wet deposition of mercury at a number of sites across the country. For more information about the network, see http://nadp.sws.uiuc.edu/mdn/Exit EPA Disclaimer

The Mercury Study Report to Congress – EPA prepared this report to fulfill requirements of the Clean Air Act Amendments of 1990. Published in 1997, it is an eight volume assessment of the magnitude of U.S. mercury emissions by source; the health and environmental impacts of those emissions; and the availability and cost of control technologies.

Volume III: Fate and Transport of Mercury in the Environment (376 pp., 4MB) - Volume III is the mercury fate and transport assessment component of the risk assessment for anthropogenic mercury emissions.

Volume IV: An Assessment of Exposure to Mercury in the United States (PDF) (293 pp., 1MB) - Volume IV is an exposure assessment component of the risk assessment for anthropogenic mercury emissions.

Volume VI, Ecological Assessment (PDF) (158 pp., 3M) - Volume VI is an ecological risk assessment for anthropogenic mercury emissions.

Volume VII: Characterization of Human Health and Wildlife Risks from Mercury Exposure in the United States (PDF) (152 pp., 727K) - Volume VII is an assessment of human health and ecological effects, identifies human subpopulations or wildlife species at elevated risk from mercury, assesses exposures from multiple environmental media, and describes the uncertainty and variability in these assessments.

Mercury Maps - This page describes a technical approach for estimating how reductions in mercury deposition will result in reduced fish tissue contamination. States, tribes, and EPA regions can use the techniques demonstrated in the Mercury Maps report to help them better understand and manage their mercury contamination problem.

STAR Grants about Mercury - EPA's National Center for Environmental Research (NCER) in the Office of Research and Development administers STAR (Science to Achieve Results) grants. Some of these grants involve studying the risks created by mercury in our environment so that we can better understand how to eliminate them. In 1999, NCER issued STAR grants to better understand the fate and transport of mercury through a watershed. In 2003, NCER issued STAR grants to better understand the fate and transport of mercury through the atmosphere.

STAR Mercury Transport and Fate Research Projects, 2000 (PDF) (8 pp., 463K) - EPA’s STAR (Science to Achieve Results) program funded a set of studies to develop a better understanding of mercury's terrestrial and aquatic fate and transformation processes that influence ecological and human exposure. This is a synopsis and overview of the research conducted through the grant program for 1999.

METAALICUSExit EPA Disclaimer- Mercury Experiment To Assess Atmospheric Loading In Canada and the United States (METAALICUS) is an experimental project in which leading mercury researchers from the United States and Canada working to address the critical uncertainties linking atmospheric mercury deposition to methylmercury concentrations in fish. In October 2007, these researchers published an article in the Proceedings of the [United States] National Academy of Sciences, "Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition," that concluded that an increase in mercury loading at rates relevant to atmospheric deposition resulted in an increase in methylmercury production and concentrations in aquatic biota in only three years. Read the abstract. Exit EPA Disclaimer

Methylmercury Availability in New England Estuaries as Indicated by the Saltmarsh Sharp-tailed Sparrow, 2004-2005 (PDF) (27 pp., 1.86 MB)Exit EPA Disclaimer This study, prepared by the BioDiversity Research Institute in 2006, assessed methylmercury availability to sparrows collected in Maine, Rhode Island and Connecticut.

2008 South Florida Environmental Report - A report about restoration, management, and protection activities associated with the Evergaldes, Lake Okeechobee, the Kissimmee Basin, and South Florida’s coastal ecosystems. The report includes information on recent mercury research.

United Nations Environment Programme: Global Mercury AssessmentExit EPA Disclaimer- At the February 2003 meeting of the UNEP Governing Council, the environmental ministers agreed to create a UNEP Mercury Programme. The long-term objective of the Programme is to facilitate national, regional and global actions to minimize uses and releases of mercury, thereby significantly reducing the adverse impacts on humans and the environment. The immediate objective of the Programme is to encourage all countries to adopt goals and take actions, as appropriate, to identify at-risk populations, minimize exposures through outreach efforts, and reduce human-generated mercury releases.

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