US counties by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2012
Riverside County 45.6%, the highest of 1026 counties, 2012
- Under 0.4
- 0.4 to 1.4
- 1.4 to 3
- 3 to 5.7
- 5.7 and over
- No data
Boundaries: U.S. Census Bureau cartographic boundary files.