| # | County | Median AQI |
|---|---|---|
| 1 | Adams County | 55 |
| 2 | Denver County | 55 |
| 3 | Larimer County | 54 |
| 4 | Weld County | 54 |
| 5 | Chaffee County | 51 |
| 6 | Jefferson County | 50 |
| 7 | Park County | 50 |
| 8 | Arapahoe County | 49 |
| 9 | Boulder County | 49 |
| 10 | Clear Creek County | 49 |
| 11 | El Paso County | 49 |
| 12 | Garfield County | 49 |
| 13 | Douglas County | 48 |
| 14 | Gilpin County | 48 |
| 15 | Mesa County | 48 |
| 16 | Gunnison County | 47 |
| 17 | La Plata County | 46 |
| 18 | Rio Blanco County | 46 |
| 19 | Grand County | 45 |
| 20 | Montezuma County | 45 |
| 21 | Jackson County | 44 |
| 22 | Pueblo County | 44 |
| 23 | Archuleta County | 32 |
| 24 | Alamosa County | 26 |
| 25 | Prowers County | 25 |
Source: EPA Air Quality Index annual summary (2024). All counties with data are ranked. Estimates carry margins of error.
Citing this page: GIS Map, “Counties with the Worst Air Quality in Colorado”, https://gismap.land/rankings/colorado/worst-air-quality-counties. Figures from EPA Air Quality Index annual summary (2024).
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