POLLUTION LOCATOR|Nonattainment Area Classifications

A nonattainment area is classified either by how severely it violates air quality standards or by the type of standard it exceeds.

Ozone Classifications
Extreme:
Area has a design value of 0.280 ppm and above.
Severe 17:
Area has a design value of 0.190 up to 0.280 ppm and has 17 years to attain.
Severe 15:
Area has a design value of 0.180 up to 0.190 ppm and has 15 years to attain.
Serious:
Area has a design value of 0.160 up to 0.180 ppm.
Moderate:
Area has a design value of 0.138 up to 0.160 ppm.
Marginal:
Area has a design value of 0.121 up to 0.138 ppm.

EPA has not yet designated areas based on the 8-hour ozone standard. For more detailed information, see EPA's Green Book on Ozone.

Carbon Monoxide Classifications
Serious:
Area has a design value of 16.5 ppm and above.
Moderate:
Area has a design value of 9.1 up to 16.4 ppm.
Not Classified:
Area designated as an carbon monoxide nonattainment area as of the date of enactment of the Clean Air Act Amendments of 1990 and did not have sufficient data to determine if it is meeting or is not meeting the carbon monoxide standard.

For more detailed information, see EPA's Green Book on Carbon Monoxide.

Sulfur Dioxide Classifications
Primary:
Exceedance of the sulfur dioxide primary standard. Primary Standards set limits to protect the public health.
Secondary:
Exceedance of the sulfur dioxide secondary standard. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.

For more detailed information, see EPA's Green Book on Sulfur Dioxide.

Particulate Matter Classifications
Serious:
Serious exceedance of the particulate matter (PM-10) standard.
Moderate:
Moderate exceedance of the particulate matter (PM-10) standard.

EPA has not yet designated areas based on the fine particulate matter (PM-2.5) standard. For more detailed information, see EPA's Green Book on Particulate Matter.