For many years after enactment of the Clean Air Act, American’s coal-fired generating plants have avoided maximum achievable emission technology regulations required by the Act. Utility power plants constitute the single largest unregulated source of mercury emissions in the United States today; they contribute some 40% of U.S. mercury emissions.
Congress told EPA to clean up toxic air pollution in 1990. Assuming EPA’s final rule complies with Congress’ directive, Americans may look forward to a day when they can again eat fish without serving their families an unhealthy dose of methylmercury.
The mercury emitted by coal-fired utilities is highly toxic to humans. Exposure to even small amounts of methylmercury can lead to irreversible neurological damage. Methylmercury’s neurodevelopmental effects pose particular risk to the developing fetus, children, and adults up to age 20. The most recent data suggest risks to the cardiovascular systems of adults as well. Mercury emitted to the air from coal plants and other sources are deposited to surrounding land and waters; it makes its way into fish tissue in the form of methylmercury. The primary route of human exposure to methylmercury is through consumption of fish.
With widespread mercury contamination in the nation’s lakes and rivers, agencies have issued increasing numbers of fish consumption advisories. All 50 states have issued advisories placing some or all of their waters off limits for those who would eat the fish they catch. As of 2008, 43 percent of lake acres and 39 percent of total river miles within the United States’ borders are under advisories for mercury. In addition, 100 percent of Lakes Superior, Michigan, Huron, and Erie and significant stretches of coastal waters are under advisories. The number and extent of advisories have increased steadily for the past 15 years. Currently, all of Pennsylvania remains under a blanket advisory that recommends limiting consumption of any recreationally-caught fish to one meal per week.
Across the US, major physicians’ associations – including the American Medical Association, the American Academy of Pediatrics, the American Public Health Association, the American Nurses Association, and Physicians for Social Responsibility – have urged stronger mercury rules.
One consequence of the various regulations at the state level is that mercury emissions control technologies such as Activated Carbon Injection (ACI) have been successfully implemented by a number of utilities across the nation. According to a 2009 study by the Government Accountability Office (GAO), these control technologies are enabling sources to obtain mercury emissions reductions as high as 99%. Moreover, reductions on the order of 90% have been achieved by plants firing different types of coal (i.e., bituminous, sub-bituminous, lignite) and employing a variety of configurations. Indeed, according to data supplied by utilities as part of EPA’s Information Collection Request for the rule, commercially operating plants firing each of the different types of coal have in fact applied ACI to control mercury emissions.
With a congressional directive that the MACT floor be keyed to the best performers, and with those performers able to achieve considerable mercury emissions reductions, EPA’s task is fairly straightforward. EPA should do now what it should have done years ago: issue a MACT standard that complies with the CAA.
Operators of coal-fired generation have known that pollution controls would be required to comply with Clean Air Act (CAA) requirements to reduce hazardous air emissions like mercury, hydrochloric acid, and arsenic. Most of the industry has been preparing for the rule by investing in modern pollution controls and cleaner, more efficient power plants.
Some utility companies have recognized the need for these reductions in mercury and other toxic emissions. “We recently completed the installation of a major air quality control system, including scrubbers, baghouse, and other equipment at one of our major coal facilities in Maryland,” said Paul Allen, senior vice president and chief environmental officer of Constellation Energy in a statement. “These systems work effectively and result in dramatically lower emissions of mercury, sulfur dioxide, particulate matter, and acid gases. We know from experience that constructing this technology can be done in a reasonable time frame, especially with good advance planning; and there is meaningful job creation associated with the projects.” 
We support the proposed rule on mercury and other air toxics. Expeditious implementation of the final rule can make a real difference. This rule can help make the air we breathe and the fish we put on our tables safer.
 Roman HA, Walsh TL, Coull BA, Dewailly É, Guallar E, et al. 2011 Evaluation of the Cardiovascular Effects of Methylmercury Exposures: Current Evidence Supports Development of a Dose–Response Function for Regulatory Benefits Analysis. Environ Health Perspect 119(5): doi:10.1289/ehp.1003012
 United State Government Accountability Office, GAO, CLEAN AIR ACT – Mercury Control Technologies at Coal-Fired Power Plants Have Achieved Substantial Emissions Reductions, October 2009.
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