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Proposed Mercury and Air Toxics Standards

On March 16,2011, the Environmental Protection Agency (EPA) issued a proposed rule that would reduce emissions of toxic air pollutants from power plants. Specifically, the proposal would reduce emissions from new and existing coal- and oil-fired electric utility steam generating units (EGUs).

EPA is also proposing to revise the new source performance standards (NSPS) for fossil-fuel-fired EGUs. This NSPS would revise the standards new coal- and oil-fired power plants must meet for particulate matter (PM), sulfur dioxide (S02), and nitrogen oxides (NOx).

The proposed toxics rule would reduce emissions of heavy metals, including mercury (Hg), arsenic, chromium, and nickel, and acid gases, including hydrogen chloride (HCI) and hydrogen fluoride (HF). These toxic air pollutants, also known as hazardous air pollutants or air toxics, are known or suspected of causing cancer and other serious health effects.

Power plants are the largest source of mercury emissions to the air. Once mercury from the air reaches water, microorganisms can change it into methylmercury, a highly toxic form that builds up in fish. People are primarily exposed to mercury by eating contaminated fish.

Methylmercury exposure is a particular concern for women of childbearing age, unborn babies, and young children because studies have linked high levels of methylmercury to damage to the developing nervous system. This damage can impair children's ability to think and learn.

Mercury and other power plant emissions also damage the environment and pollute lakes, streams, and fish. Other toxic metals emitted from power plants, such as arsenic, chromium and nickel can cause cancer. Reducing toxic power plant emissions will also cut fine particle pollution and prevent thousands of premature deaths and tens of thousands of heart attacks, bronchitis cases and asthma episodes.

As part of this rulemaking, EP A is also proposing monitoring changes and other minor amendments to the industrial, commercial, and institutional steam generating units (Le., boilers) NSPS, but does not propose to amend those emission standards.

Affected Sources

The mercury and air toxics standards will affect EGUs that bum coal or oil for the purpose of generating electricity for sale and distribution through the national electric grid to the public are affected by this rule. These include investor-owned units as well as units owned by the Federal government, municipalities, and cooperatives that provide electricity for commercial, industrial, and residential uses.

EPA has identified two different subcategories of coal-fired EGUs, two different subcategories of oil-fired EGUs, and a subcategory for units that combust gasified coal or solid oil (Integrated gasification and combined cycle (lGCC) units) based on the design ofthe various types of boilers at different power plants. The proposed air toxics rule includes emission standards and other requirements for each subcategory.

EPA estimates that there are approximately 1,350 units affected by this action. Approximately 1,200 existing coal-fired units and 150 oil fired units at about 525 power plants. The NSPS will affect boilers that bum fuels, including coal, oil, or natural gas to produce steam. The steam is used to produce electricity or provide heat.

Boilers are used at industrial facilities (e.g., refmeries, chemical and manufacturing plants, and paper mills), commercial establishments (e.g., stores/malls, laundries, apartments, restaurants, hotels/motels), and institutional facilities (e.g., medical centers, educational and religious facilities, and municipal buildings).


For all existing and new coal-fired EGUs, the proposed standards would establish numerical emission limits for mercury, PM (a surrogate for toxic non-mercury metals), and HCI (a surrogate for toxic acid gases).

For all existing and new oil-fired EGUs, the proposed toxics rule would establish numerical emission limits for total metals, HCI, and HF. Compliance with the metals standards is through fuel testing. The proposal would establish alternative standards, including S02 (as an alternate to HCI), individual non-mercury metal air toxics (as an alternate to PM), and total non-mercury metal air toxics (as an alternate to PM) for certain subcategories of power plants.

A range of widely available, technical and economically feasible practices, technologies, and compliance strategies are available to power plants to meet the emission limits, including wet and dry scrubbers, dry sorbent injection systems, activated carbon injection systems, and baghouses.

EPA estimates the health benefits associated with reduced exposure to fine particles are $59 billion to $140 billion in 2016 (2007$).

EPA estimates the total national annual cost of this rule will be $10.9 billion in the year 2016.

EP A anticipates that the proposed toxics rule may have a significant economic impact on small entities. Thus, as required by section 609(b) ofthe Regulatory Flexibility Act (RFA) as amended by the Small Business Regulatory Enforcement Fairness Act of 1996 (SBREFA), we conducted outreach to small entities and convened a Small Business Advocacy Review (SBAR) Panel to obtain advice and recommendations from representatives of the small entities that potentially would be subject to the requirements of the proposed toxics rule.

EPA also consulted with State, local, and tribal officials in the process of developing the proposed toxics rule to permit them to have input into its development.


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