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RankingsCaliforniaCleanest air

Counties with the Cleanest Air in California

The top 25 of 52 California counties on GIS Map, ranked by lowest median Air Quality Index, counting only counties that host an EPA air monitor.

#CountyMedian AQI
1Mono County
19
2Sonoma County
19
3San Mateo County
27
4Marin County
28
5Trinity County
31
6Del Norte County
32
7Lake County
32
8San Francisco County
33
9Nevada County
36
10Humboldt County
38
11Glenn County
39
12Monterey County
39
13Santa Cruz County
39
14Solano County
39
15Amador County
40
16Siskiyou County
40
17Tuolumne County
40
18Calaveras County
42
19Mendocino County
43
20San Benito County
43
21Tehama County
43
22El Dorado County
44
23Shasta County
44
24Mariposa County
45
25Yolo County
45

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 Cleanest Air in California”, https://gismap.land/rankings/california/cleanest-air-counties. Figures from EPA Air Quality Index annual summary (2024).

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