Air Quality Standards of the Clean Air Act

Air Quality Standards of the Clean Air Act

EPA Emissions Limits for Criteria Pollutants
Under the Clean Air Act, the Environmental Protection Agency (EPA) has the authority to set standards to limit pollutant concentrations discharged into the air (emissions) from a variety of sources, such as steel mills, chemical plants, and utilities. This is similar to the EPA standards for industrial effluents – the discharge of wastewater – to surface waters and from wastewater treatment plants. Clean Air Act standards are formulated with the cooperation of the EPA and individual states.

About the Clean Air Act
The basic structure of the Clean Air Act was crafted by Congress in 1972, and it was significantly revised in 1977 and 1990. The purpose of the Act was to reduce emissions from both industrial and automotive sources which were responsible for smog in major U.S. cities and industrial areas. Additionally, the Clean Air Act provided for the reduction of acid rain, cancer-causing air pollutants, environmental threats such as heavy metals, as well as emissions that deplete the atmosphere’s ozone layer.

What are Criteria Pollutants?
The Clean Air Act authorizes the EPA to set National Ambient Air Quality Standards (NAAQS) for six major threats to air quality, known as criteria pollutants: carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), lead (Pb), particulate matter (PM), and sulfur dioxide (SO2).

Table of EPA Standards for Criteria Pollutants

To see a table listing the specific standards for the criteria pollutants, please click on the link below, provided by the EPA:

Accomplishments of the Clean Air Act

The Clean Water Act is considered by many experts as the most effective environmental protection legislation ever instituted in the United States.  Following are some of the Act’s most noteworthy achievements:

  • The aggregate emissions of the six criteria pollutants were reduced by 69% between 1970 and 2014.
  • In response to the Act, new plants and factories have installed clean, modern technologies to curb pollutants.
  • Protections to curb reduction of the ozone layer have greatly decreased the incidence of skin cancer and cataracts.
  • The EPA has taken steps to decrease emissions that contribute to climate change.
  • Environmental damage caused by air pollution has been reduced.
  • The Act has helped curb the emission of pollutants from municipal solid waste landfills.
  • Reduction in air pollutants has increased crop yields.


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