Changes

On March 16, 2011, the U.S. Environmental Protection Agency (EPA) announced its [http://www.epa.gov/airquality/powerplanttoxics/pdfs/proposal.pdf proposed emissions standards] to limit mercury, acid gases and other toxic pollution from power plants, to prevent an estimated 91 percent of the mercury in coal from being released to the air. The EPA estimates that there are approximately 1,350 units affected by the action, including 1,200 existing coal-fired units.<ref name=fs>[http://www.epa.gov/airquality/powerplanttoxics/pdfs/proposalfactsheet.pdf "Fact Sheet: Proposed Mercury and Air Toxics Standards"] EPA, accessed March 2011.</ref>

Section 112 of the Clean Air Act requires national emission standards for Hazardous Air Pollutants (HAPs). The emission standards must reflect application of the maximum-achievable control technology (MACT). The EPA is tasked with developing MACT emission rules for specific industry groups, such as industrial, institutional, and commercial boilers. On Feb. 26, 2004, National Emission Standard for Hazardous Air Pollutants (NESHAP), commonly referred to as the Industrial Boiler MACT Rule, was finalized by the EPA. However, on June 8, 2007, the U.S. Court of Appeals for the District of Columbia Circuit issued a decision to vacate the Industrial Boiler MACT Rule, and the EPA was required to rewrite it.<ref name=dw>Don Wolf, [http://hpac.com/bse/understanding-industrial-boiler-mact-0610/index.html "Understanding the Industrial Boiler MACT Rule"] HPAC Engineering, June 3, 2011.</ref>