Q: What is a nonattainment area, and where are they?

A: The Environmental Protection Agency (EPA) has designated a few common pollutants found across the United States as “criteria” pollutants because the bases for regulating them and establishing permissible limits are health-based criteria. The EPA has designated the following as criteria pollutants for which the establishment of National Ambient Air Quality Standards (NAAQS) is required under the Clean Air Act (CAA):

• Sulfur dioxide (SO2)
• Particulate matter (PM-10 and PM-2.5)
• Carbon monoxide (CO)
• Ozone
• Nitrogen dioxide (NO2)
• Lead

For each criteria pollutant, the EPA establishes primary and secondary NAAQS. The primary standard establishes a level of the pollutant in the ambient air that will allow for the protection of human health. The secondary standard is established to prevent environmental and property damage.

The term “nonattainment area” refers to a geographic region that has not met the NAAQS for a particular pollutant. Geographic areas with air quality that meets or is better than NAAQS are designated as “attainment areas” for that particular pollutant. The attainment/nonattainment designation is based on monitoring conducted to determine the ambient concentration of each pollutant in all areas of the country.

Depending on the pollutant, there may be several different classifications of nonattainment that indicate how badly the air is polluted and how long it will be before the area can reasonably be expected to come into attainment with NAAQS. The nonattainment classification system is used to establish realistic deadlines for areas to come into attainment. Ozone, CO, and particulate matter have multiple classifications of nonattainment. 

Once an area is designated nonattainment, the state must submit a plan to the EPA detailing how the nonattainment area will be brought into attainment. Such plans will include regulations to restrict emissions and will impact the permitting provisions applicable to major sources of air pollutants.

Governing laws and regulations:
40 Code of Federal Regulations (CFR) 81.300 to 81.356