Counties with the Worst Air Quality in California
The top 25 of 52 California counties on GIS Map, ranked by median Air Quality Index, counting only counties that host an EPA air monitor.
| # | County | Median AQI |
|---|---|---|
| 1 | Riverside County | 87 |
| 2 | San Bernardino County | 87 |
| 3 | Los Angeles County | 80 |
| 4 | Kern County | 72 |
| 5 | San Diego County | 71 |
| 6 | Tulare County | 71 |
| 7 | Fresno County | 67 |
| 8 | Imperial County | 63 |
| 9 | Inyo County | 61 |
| 10 | Kings County | 60 |
| 11 | Colusa County | 54 |
| 12 | Orange County | 54 |
| 13 | Stanislaus County | 53 |
| 14 | Madera County | 52 |
| 15 | Merced County | 52 |
| 16 | Sacramento County | 51 |
| 17 | San Joaquin County | 51 |
| 18 | Placer County | 50 |
| 19 | Ventura County | 50 |
| 20 | Alameda County | 49 |
| 21 | San Luis Obispo County | 49 |
| 22 | Santa Barbara County | 49 |
| 23 | Sutter County | 49 |
| 24 | Contra Costa County | 48 |
| 25 | Plumas County | 48 |
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 California”, https://gismap.land/rankings/california/worst-air-quality-counties. Figures from EPA Air Quality Index annual summary (2024).
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