Technology Transfer Network - OAR Policy and Guidance
Mercury Emissions and Electric Utilities Fact Sheet
Mercury Emissions and Electric Utilities
February 24, 1998
EPA is today issuing a Report to Congress on emissions of hazardous air pollutants from power plants that identifies electric utilities as the largest remaining source of mercury emissions to the air. EPA has a five-pronged approach to controlling mercury emissions from power plants. The approach includes:
EPA already has taken steps to reduce mercury emissions from three other significant industry sources. The Agency issued final regulations cutting mercury emissions from municipal waste combustors in 1995 and from medical waste incinerators last August. Latter this year, EPA will announce a final rule to reduce mercury emissions from hazardous waste combustion. These actions, once fully implemented, will reduce mercury emissions caused by human activities by over 50% from 1990 levels.
Mercury moves through the environment as a result of both natural and human activities. The human activities that are chiefly responsible for causing mercury to enter the environment are burning mercury-containing fuels and wastes, and industrial manufacturing processes. Mercury emissions are transported through the air and deposited to water and land where humans and wildlife are exposed. Based on the emissions inventory in EPA's Mercury Study Report to Congress (December 1997), the highest emitting source category is coal burning electric utilities. This group of sources account for one-third of the anthropogenic (caused by human activity) emissions to the air in the US.
Concentrations of mercury in air are usually low and of little direct concern. Once mercury enters waters, either directly or through air deposition, it can bioaccumulate in fish and animal tissue in its most toxic form, methylmercury. Bioaccumulation means that the concentration of mercury in predators at the top of the food web (for example, predatory fish and fish-eating birds and mammals) can be thousands or even millions of times greater than the concentrations of mercury found in the water.
Human exposure to mercury occurs primarily through eating contaminated fish. Exposure to high levels of mercury has been associated with serious neurological and developmental effects in humans. Depending on the dose, the effects can include subtle losses of sensory or cognitive ability, tremors, inability to walk, convulsions, and death. Because the developing fetus may be the most sensitive to the effects from methylmercury, women of child-bearing age are regarded as the population of greatest interest.
People who consume average amounts of a variety of commercially available fish as part of a balanced diet are not likely to consume harmful amounts of mercury. Moreover, fish is an excellent source of proteins, vitamins and minerals and including a variety of fish in the diet is a healthy dietary practice. The levels of methylmercury found in the most frequently consumed commercial fish are low, especially compared to levels that might be found in some non-commercial fish from fresh water bodies that have been affected by mercury pollution. While most U.S. consumers need not be concerned about their exposure to methylmercury, some exposures may be of concern. Those who regularly and frequently consume large amounts of fish -- either marine species that typically have much higher levels of methylmercury than the rest of seafood, or freshwater fish that have been affected by mercury pollution -- are more highly exposed.
The greatest exposure and risk exist for those persons who regularly eat large amounts of fish from a single location which has been impacted by mercury pollution, particularly for women of child-bearing age. Everyone should follow established guidelines in accordance with existing state and tribal advisories on locally caught fish in order to reduce the potential risk of mercury exposure.
Mercury is the most frequent basis for fish advisories issued by States or Tribes, represented in 60% of all water bodies with advisories. They increased 28% from 1995 to 1996 (from 1,308 to 1,675). Thirty-nine states have advisories for mercury in one or more water bodies, and nine States have issues statewide mercury advisories.
There is a good deal about the contribution of electric utilities to concentrations of mercury in fish that we do not yet know. There is a plausible link between anthropogenic releases of mercury from industrial and combustion sources in the United States and methylmercury in fish. However, these fish methylmercury concentrations also result from existing background concentrations of mercury (which may consist of mercury from natural sources, as well as mercury which has been re-emitted from the oceans or soils) and deposition from the global reservoir (which includes mercury emitted by other countries). Given the current scientific understanding of the environmental fate and transport of this element, it is not possible to quantify with precision how much of the methylmercury in fish consumed by the U.S. population is contributed by U.S. emissions from utilities relative to other sources of mercury.
EPA's approach to mercury emissions from power plants includes the following actions: