Acid Rain Program

The Acid Rain Program (ARP) requires major emission reductions of SO₂ and NO_x from the power sector. The SO₂ program sets a permanent cap on the total amount of SO₂ that can be emitted by electric generating units in the United States. NO_x reductions are achieved through a program that applies to a subset of coal-fired power plants and is closer to a traditional, rate-based regulatory system. Since the program began in 1995, the Acid Rain Program has achieved significant emission reductions.

The earlier reports highlight the results of the Acid Rain Program. In 2010, EPA began producing reports that combined the results of the ARP, the Clean Air Interstate Rule, and the former NO_x Budget Trading Program into a single yearly report.​

View Acid Rain Program Historical Reports

Clean Air Interstate Rule

The Clean Air Interstate Rule (CAIR) began in 2010 and covers 27 eastern states and the District of Columbia. CAIR was designed to address interstate transport of ozone and fine particulate matter (PM_2.5) pollution. To do so, CAIR required certain states to limit annual emissions of nitrogen oxides (NO_x) and sulfur dioxide (SO₂), which contribute to the formation of ozone and PM_2.5. It also required certain states to limit ozone season NO_x emissions which contribute to the formation of ozone during the summer ozone season.

CAIR developed three separate trading programs that could be used to achieve the required reductions — the CAIR NO_x ozone season trading program, the CAIR annual NO_x trading program, and the CAIR SO₂ trading program. The CAIR NO_x ozone season and annual programs began in 2009, while the CAIR SO₂ annual program began in 2010. The reduction in ozone and PM_2.5 formation resulting from implementation of the CAIR programs provides health benefits as well as improved visibility in national parks and improved stream quality in the eastern United States.

The 2009 progress report highlights the results of CAIR. In 2010, EPA began producing reports that combined the results of CAIR, the Acid Rain Program, and the former NO_x Budget Trading Program into a single yearly report.

View Clean Air Interstate Rule Historical Reports

NO_x Budget Trading Program

The NO_x Budget Trading Program (NBP) was a cap and trade program that began in 2003 and was designed to reduce NO_x emissions during the ozone season (May 1 through September 30). Beginning in 2009, the NBP was effectively replaced by the ozone season NO_x program under the Clean Air Interstate Rule, which required further summertime NO_x reductions from the power sector.

View NO_x Budget Trading Program Historical Reports

Ozone Transport Commission (OTC) NO_x Budget Program

The Ozone Transport Commission (OTC) NO_x Budget Program ran from 1999-2002. Its membership was comprised of the states of Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, New York, New Jersey, Pennsylvania, Maryland, Delaware, the northern counties of Virginia, and the District of Columbia. The Program’s goal was to reduce summertime NO_x emissions regionwide as a part of each state’s effort to attain the national ambient air quality standard (NAAQS) for ground level ozone.

View Ozone Transport Commission NO_x Budget Program Historical Reports