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 How
does mercury occur in the environment?
 Mercury is a naturally occurring element that can be found throughout the environment. Human activities such as burning coal and using mercury to manufacture certain products, have increased the amount of mercury that is currently cycling in the atmosphere, in soils, and in lakes, streams and the oceans. Mercury in these locations increases risks to people and wildlife.
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What are the biggest sources of mercury air emissions?
According
to EPA's 1999 National Emissions Inventory, coal-fired electric
power plants are the largest source of human-caused mercury air
emissions in the U.S. Power plants account for about 40% of total
U.S. manmade mercury emissions. Other large sources are industrial
boilers (about 10% of U.S. mercury emissions), burning hazardous
waste (about 5%), and chlorine production (also about 5%). Burning
municipal waste and medical waste was once a large source of emissions
but today, in response to EPA and State regulations and reductions
in mercury use, these sources are much less important.
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How do people and wildlife become exposed to mercury?
Mercury that is emitted to the air falls to the ground either very close to the source or many miles away. When mercury is deposited into the water, or runs off the ground into the water, microorganisms convert it to methylmercury, a highly toxic form of mercury.
Small organisms take this up as they feed. As animals higher up the food chain eat those small organisms, they also take in methylmercury. The process, known as bioaccumulation, continues with levels of mercury increasing as it moves up the food chain. Fish that are higher in the food chain, such as sharks and swordfish, have much higher mercury concentration than fish that are lower on the food chain. Humans become exposed when they eat fish that are contaminated with mercury.
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How does mercury affect health?
Methylmercury
is highly toxic. The developing fetus is the most sensitive to the
effects of mercury, and so women of childbearing age are the population
of greatest concern. Children of women exposed to relatively high
levels of methylmercury during pregnancy have exhibited a variety
of abnormalities, including delayed onset of walking and talking,
reduced neurological test scores, and delays and deficits in learning
ability.
Eight percent of the women of childbearing age have levels of mercury
in their blood that exceeds the level EPA considers safe. In addition,
there is growing evidence that methylmercury exposure can have adverse
cardiovascular effects for adults, resulting in elevated blood pressure
and incidence of heart attack.
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Do some fish contain more mercury than others?
Yes.
Predator fish – big fish that eat smaller fish – tend to have higher
methylmercury concentrations than other fish. The Food and Drug
Administration has issued advise to pregnant women regarding consumption
of certain types of fish. States issue fish advisories that inform
consumers of the extent to which they need to limit their consumption
of locally caught fish. Certain species of commercially available
saltwater fish, such as shark and swordfish, kingfish and tilefish
also can contain high levels of mercury. National and regional information
is available from our Fish Advisory page.
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How will EPA reduce mercury emissions from power plants?
EPA is currently developing a standard to limit emissions from coal-fired power plants. A standard will be proposed for public comment on or before December 15, 2003. The Administration's proposed Clear Skies legislation would cap emissions of mercury at 26 tons in 2010 and 15 tons in 2018, down from a current total of 48 tons.
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What else is EPA doing to reduce mercury emissions?
EPA has taken a number of recent actions to reduce mercury pollution, include issuing stringent regulations for industries that significantly contribute to mercury pollution. These actions, once fully implemented, will reduce nationwide mercury emissions significantly. They include:
- Municipal waste combustors (MWCs) emitted about 42 tons of mercury emissions into the air in 1990. EPA issued final regulations for MWCs on October 31, 1995. These regulations require that mercury emissions from these facilities be reduced by about 90 percent, from 1990 emission levels.
- Medical waste incinerators (MWIs) emitted about 50 tons of mercury emissions into the air in 1990. EPA issued emission standards for MWIs on August 15, 1997, which requires mercury emissions from MWIs be reduced by over 90 percent from 1990 emission levels.
In addition, EPA has other regulations that have been proposed that will reduce emissions of mercury including standards for: chlor-alkalai plants and industrial boilers.
In addition, other factors that have influenced mercury emissions include:
- Federal bans on mercury additives in paint and pesticides;
- Industry efforts to reduce mercury in batteries;
- Increasing state regulation of mercury emissions and mercury in products;
- State-mandated recycling programs; and
- Voluntary actions by industry.
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