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STAR Researchers Study Environmental Behavior of Mercury
Thursday, June 5, 2003
NCER Staff Writer
WASHINGTON (NCER) - Mercury contamination in the environment is a growing concern.
Some forms of environmental mercury can damage the liver, kidneys, and
brain and can be especially risky for human health and wildlife because
it concentrates in animal tissues as it moves up the food chain.
Since mercury is a natural, metallic element, it will always be present in the environment in one form or another. According to the U.S. Environmental Protection Agency's (EPA's) Mercury Study Report to Congress (December 1997), mercury concentrations in water, soil, and other media have increased by a factor of two to five over pre-industrial levels. As the quantity of available mercury in the environment has increased, so have the risks of neurological and reproductive problems for humans and wildlife, making it a pollutant of potential human health and environmental concern. Mercury contamination is the most frequent reason for fish advisories and almost 79 percent of all public health advisories on fish consumption in the United States are at least partly due to mercury contamination.
After mercury is released into the environment, it can be transformed by complex chemical processes from an inorganic element into a highly toxic form called methylmercury that can bioaccumulate in fish and animal tissues. The term for this chemical process is methylation and the possible consequences for people or wildlife exposed to mercury in this form can include neurological and developmental disorders that hamper growth and suppress the ability to reproduce. Exposure to methylmercury, particularly in fetuses and young children, is thought to be an important public health threat.
While the public often views mercury as a rare silvery metal, it is nearly ubiquitous and a cause for everyone's concern. Coal-fired power plants, municipal waste incinerators, chlor-alkali plants, and commercial and industrial boilers emit it. Mercury can be deposited from the atmosphere via rainfall and on land, mercury can bind to organic and inorganic matter in soil, including the sediments where naturally occurring bacteria transform it into methylmercury.
As with the pesticide, DDT, mercury can be carried by air and water around the globe. Because of this problem, EPA's research office, launched a research initiative in 2000 setting targets and priorities for the Science to Achieve Results (STAR) program and other research efforts to understand this pollutant.
In the EPA's mercury research plan, there are two chief goals: reducing and preventing mercury releases, and understanding the movement of the mercury through the environment and its subsequent effects. This important research supports EPA's program offices in their decision-making processes on regulating mercury in urban air toxics, and from coal-fired utilities, chlorine production facilities, municipal landfills, and others.
Some of the mercury research projects completed or now underway by STAR scientists include:
- Researchers at the University
of Connecticut conducted some of the only studies done on the behavior
and fate of mercury in the marine environment as opposed to freshwater.
Their work in coastal waters such as Long Island Sound confirmed the
prominent role of mercury production and emissions in marine waters.
- Scientists at the University
of Michigan and Princeton
University have changed all previous theories regarding how quickly
mercury volatilizes in the atmosphere. Another component of their work
allows us to understand which parts of a watershed are the most likely
sources of mercury emission into the atmosphere, for example, clear
lakes vs. murky ones.
- Researchers at the University of Wisconsin/Madison and the University of Minnesota are studying the factors that influence mercury levels in water and aquatic life, especially fish. They have shown that mixing zones, where waters of different temperatures and other characteristics come together, provide significant pathways for methylmercury to enter the food web of some northern temperate lakes such as Lake Superior.
The latest STAR grants focus on the natural and human sources of mercury, the behavior of mercury in the atmosphere, and the impact of mercury in the U.S. as it travels from industrial sources in Asia. As previous researchers have discovered, even without additional input, our soil, water, and vegetation contain residues of mercury that are re-emitted, making it a persistent problem.
STAR is also working on answers to other questions of concern. If we reduce releases of mercury in the U.S., will the levels of methylmercury decrease in fish and by how much? How much exposure to methylmercury do people get, particularly among women of childbearing age and children in highly exposed population groups? Can innovative control technologies for mercury reduce its emissions from coal-fired utility boilers and other combustion systems?
Without the contributions of science, such questions might never be answered. STAR researchers are making a substantial contribution to better understanding how this complex element behaves in the environment.