US counties by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2011
Riverside County 42.5%, the highest of 1047 counties, 2011
- Under 0.3
- 0.3 to 1.1
- 1.1 to 2.2
- 2.2 to 4.2
- 4.2 and over
- No data
Boundaries: U.S. Census Bureau cartographic boundary files.