US counties by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2016
San Bernardino County 37.7%, the highest of 1008 counties, 2016
- Under 0.3
- 0.3 to 0.8
- 0.8 to 1.7
- 1.7 and over
- No data
Boundaries: U.S. Census Bureau cartographic boundary files.