The Clean Air Interstate Rule (CAIR) was issued in 2005 to reduce the amount of sulfur dioxide and nitrogen oxides released by power plants by 70%. The rule covers 28 eastern states and the District of Columbia.
States must meet the required emissions reduction either by participating in an interstate cap and trade system administered by the EPA, or by meeting individual state emission limits by methods of the state's choosing.
Click on the link to find out more about the Clean Air Act http://www.epa.gov
Source: US EPA. 2013. Clean Air Interstate Rule - Clean Air Markets. Accessed on 9 September 2013. Available at http://www.epa.gov