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The Clean Air Act

The Clean Air Act

The Clean Air Act (CAA) is the primary federal law governing air quality in the United States. First enacted in 1963 and significantly amended in 1970 and 1990, it establishes a comprehensive framework for regulating air pollution.

National Ambient Air Quality Standards (NAAQS)

The EPA sets NAAQS for six criteria pollutants that are widespread and harmful to public health and the environment:

  • Carbon monoxide (CO)
  • Lead (Pb)
  • Nitrogen dioxide (NO2)
  • Ozone (O3)
  • Particulate matter (PM2.5 and PM10)
  • Sulfur dioxide (SO2)

    • There are two types of NAAQS:

  • Primary standards — protect public health with an adequate margin of safety
  • Secondary standards — protect public welfare (crops, vegetation, buildings, visibility)

    • State Implementation Plans (SIPs)

    States must develop State Implementation Plans detailing how they will achieve and maintain NAAQS. Areas that meet the standards are in attainment; areas that do not are designated nonattainment and face stricter requirements.

    New Source Performance Standards

    The EPA sets technology-based emission standards for new and modified stationary sources of pollution (power plants, factories, refineries). These standards require the use of the best demonstrated technology for reducing emissions.

    Hazardous Air Pollutants (HAPs)

    The 1990 amendments identified 189 hazardous air pollutants (toxic air pollutants). Sources emitting these pollutants must install Maximum Achievable Control Technology (MACT).

    Mobile Sources

    The CAA regulates emissions from motor vehicles and fuels. The EPA sets emission standards for cars, trucks, and other mobile sources, and regulates fuel composition (including lead, sulfur content, and renewable fuel requirements).

    Title V Permits

    Major sources of air pollution must obtain a Title V operating permit that consolidates all applicable air quality requirements into a single document.

    Enforcement

    The CAA is enforced through:

  • Administrative orders and penalties
  • Civil judicial actions by the EPA or state agencies
  • Criminal prosecution for knowing violations
  • Citizen suits — private parties can sue violators or the EPA for failure to perform mandatory duties

    • Quiz: The Clean Air Act

    Question 1 of 3

    How many criteria pollutants does the EPA regulate under NAAQS?