Clean Air Act, U.S.

THE U.S. CLEAN Air Act (CAA) was passed by the U.S. Congress in 1963 and strengthened with amendments passed in 1970, 1977, and 1990. The U.S. Environmental Protection Agency (EPA) is responsible for implementation and regulation of the CAA, although much of the work falls to state and local governments. EPA regulates many pollutants (such as particulate matter) that play an important role in the Earth's radiation balance, but CAA has not been used to regulate greenhouse gases (GHGs), the pollutants most responsible for global warming. A 2007 U.S. Supreme Court decision ruled that GHGs fall within the jurisdiction of the EPA and the CAA, forcing the EPA to re-examine its ruling on this matter.

The first U.S. federal legislation dealing with air pollution was the Air Pollution Control Act of 1955, which recognized air pollution as a national hazard and encouraged research on the issue. In 1963, the original version of the CAA was passed, which called for the study of air quality issues and set emissions standards for stationary sources. The 1970 CAA was a major overhaul of the original version, making it a comprehensive federal law regulating stationary and mobile sources of air pollution.

The 1970 amendments further established a federal regulatory roll that had previously been lacking. Along with these amendments, Congress created the EPA in 1970 and charged it with carrying out the CAA. The EPA set National Ambient Air Quality Standards for six “criteria” pollutants, and set the target year at 1975 for locations across the United States to meet these standards. Many parts of the country did not meet this deadline, however, and the CAA amendments of 1977 were passed mainly to set new goals and deadlines.

A larger revision occurred with the CAA amendments of 1990. Most significantly, a new market-based cap-and-trade system was implemented as an approach for meeting air quality goals. The 1990 amendments included new standards for hazardous air pollutants and new requirements for EPA regulation and reporting. The 1990 amendments also included provisions to deal with the pressing air quality issues of the time, such as stronger regulation of ground-level ozone, particulate matter, and carbon monoxide; provisions to protect the stratospheric ozone layer; and measures to reduce the pollutants contributing to acid rain. Despite existing knowledge of global warming, however, the amendments did not include any measures to deal with GHGs or climate change.

GHGs, such as carbon dioxide (CO2), have not been included in either of the groups that the EPA regulates, which are comprised of the six “criteria” pollutants and a group of hazardous air pollutants. In 1999, a group of private organizations petitioned the EPA to begin regulating four GHGs, including CO2. The EPA denied the petition by responding that CO2 is not a pollutant under the CAA, that the EPA did not have the authority to regulate against climate change, and that even if it did, it would choose not to regulate due to uncertainty in establishing a causal link between global warming and GHGs. Led by Massachusetts, 12 states, four local governments, and 13 private organizations then filed suit against the EPA (joined by 10 states and six trade associations), challenging that decision.

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