Any geographic region of the United States which has been designated as nonattainment under Section 107 of the Clean Air Act Amendments for any pollutant for which a national ambient air quality standard (NAAQS) exists. These areas must take specific emission reduction measures to reach NAAQS.

Further information on nonattainment areas is available in Pub. 321 Project Level Air Quality Handbook:

https://www.pa.gov/content/dam/copapwp-pagov/en/penndot/documents/public/pubsforms/publications/pub%20321.pdf

Any geographic region of the United States which has been designated as nonattainment under Section 107 of the Clean Air Act Amendments for any pollutant for which a national ambient air quality standard (NAAQS) exists. These areas must take specific emission reduction measures to reach NAAQS.

Further information on nonattainment areas is available in Pub. 321 Project Level Air Quality Handbook:

https://www.pa.gov/content/dam/copapwp-pagov/en/penndot/documents/public/pubsforms/publications/pub%20321.pdf