| County | Area | Nonattainment in year | Redesignation to attainment | Classification | Part or whole county | Population (2000) |
|---|---|---|---|---|---|---|
| Adams | Denver Metro | 95 96 97 98 99 00 01 | NA | Moderate | Part | 356,944 |
| Arapahoe | Denver Metro | 95 96 97 98 99 00 01 | NA | Moderate | Part | 483,770 |
| Archuleta | Pagosa Springs | 95 96 97 98 99 00 01 | 8/14/01 | Moderate | Part | 1,852 |
| Boulder | Denver Metro | 95 96 97 98 99 00 01 | NA | Moderate | Part | 291,288 |
| Denver | Denver Metro | 95 96 97 98 99 00 01 | NA | Moderate | Whole | 554,636 |
| Douglas | Denver Metro | 95 96 97 98 99 00 01 | NA | Moderate | Whole | 175,766 |
| Fremont | Canon City | 95 96 97 98 99 00 01 | 7/31/00 | Moderate | Part | 18,587 |
| Jefferson | Denver Metro | 95 96 97 98 99 00 01 | NA | Moderate | Whole | 527,056 |
| Pitkin | Aspen | 95 96 97 98 99 00 01 | NA | Moderate | Part | 5,873 |
| Prowers | Lamar | 95 96 97 98 99 00 01 | NA | Moderate | Part | 8,681 |
| Routt | Steamboat Springs | 95 96 97 98 99 00 01 | NA | Moderate | Part | 9,815 |
| San Miguel | Telluride | 95 96 97 98 99 00 01 | 8/14/01 | Moderate | Part | 1,805 |
KEY: NA = not applicable.
SOURCE: U.S. Environmental Protection Agency, Green Book, available at http://www.epa.gov/oar/oaqps/greenbk/anay.html as of Apr. 20, 2002.