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Air Quality Program

Air Quality Standards

Federal and state agencies set air quality standards for outdoor air. The purpose of these standards is to prevent air pollution from reaching levels that hurt human health. When an area does not meet an air quality standard, the state must develop a plan to clean up the air.

National Standards

EPA sets national standards for six air pollutants called "criteria air pollutants." These federal standards are called national ambient air quality standards (NAAQS). States monitor air quality in different areas to find out if the areas are meeting the national air quality standards. The criteria air pollutants are:

There are both national and state standards for most criteria air pollutants. States may set standards at different levels than the federal levels for their areas. State standards must be at least as protective as federal standards.


When EPA sets or revises a national standard, Washington uses air monitoring and other air quality data to determine if air quality meets the new or revised standard. Based on this data, Washington recommends to EPA how areas of the state should be classified or designated. EPA sets each area's designation. Possible designations are:

  • Attainment (meets and maintains a standard)
  • Nonattainment (does not meet a standard)
  • Unclassifiable (not enough information to determine)

State Implementation Plans (SIPs)

The federal Clean Air Act requires states to develop plans to protect and maintain air quality in the state. It also requires states to develop specific plans to bring areas not meeting standards (nonattainment) back into attainment. These plans are called State Implementation Plans (SIPs).

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