Several existing programs under the Clean Air Act, such as State Implementation Plan (SIP) Limits, the Title IV Acid Deposition regulations, and the NOx SIPCall are currently regulating haze-forming pollutants and their precursors. In 1999, EPA issued the Regional Haze Rule (RHR), intended to further reduce haze and protect visibility in "federal Class I areas, " which are certain types of national and international parks and wilderness areas. Since the regulation was proposed, over 40 states have requested major changes in the rule, as have diverse groups including industrial, business and environmental advocates.

Regional Haze Timelines:

• Rule Development Timeline
• State Implementation Milestones

Full text of the RHR:

• Regional Haze Rule

Map of Class I areas:

• View Map

Under the RHR, states must develop specifications for BART sources that meet EPA requirements. BART rules will establish the types of emissions reductions that must be achieved by existing sources.

The BART requirement will greatly impact the use of coal in the nation as a whole. BART regulations for coal-fired utilities are expected to require a reduction of 90 to 95% in sulfur dioxide emissions. While this level is achievable, it is extremely expensive and may force the shutting down of many coal-fired plants. It is highly unlikely that the replacement generation will be coal-fired.