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The Clean Air Act (CAA) is a comprehensive federal law in the United States that regulates air emissions from both stationary and mobile sources. Originally enacted in 1963 and significantly amended in 1970, 1977, and 1990, the CAA authorizes the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) to protect public health and the environment.
Key provisions of the Clean Air Act include:
- Regulation of Air Pollutants: The CAA requires the EPA to identify and regulate hazardous air pollutants (HAPs) and set emission standards for industries to limit their release.
- National Ambient Air Quality Standards (NAAQS): The CAA mandates the establishment of NAAQS for pollutants considered harmful to public health and the environment, such as ozone, particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.
- State Implementation Plans (SIPs): States are required to develop SIPs to ensure compliance with the NAAQS. These plans outline how each state will control air pollution from various sources to meet federal standards.
- Permitting and Compliance: The CAA establishes a permitting system for large sources of air pollution, ensuring that they meet specific emission limits and operate in compliance with the law.
- Mobile Source Emissions: The CAA includes provisions for reducing emissions from mobile sources like cars, trucks, and airplanes, including setting fuel standards and promoting cleaner technologies.
- Acid Rain Program: The 1990 amendments introduced the Acid Rain Program, which aimed to reduce sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions, the primary causes of acid rain.
- Climate Change and Greenhouse Gases: Although not originally focused on climate change, the CAA has been interpreted by courts to allow the EPA to regulate greenhouse gases (GHGs) that contribute to global warming.
The Clean Air Act has played a pivotal role in improving air quality in the United States, significantly reducing pollutants that cause smog, acid rain, and health problems while providing a framework for addressing new and emerging environmental challenges.
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