The Smoggiest Cities in America

5. Phoenix-Mesa, AZ
> Average high ozone days per year: 39.3
> Average 24-hour unhealthy particle pollution: 7.8
> Adults with asthma: 383,476
> Population: 5,114,212

4. Fresno-Madera-Hanford, CA
> Average high ozone days per year: 60.2
> Average 24-hour unhealthy particle pollution: 51.5
> Adults with asthma: 88,818
> Population: 1,311,371

3. Visalia, CA
> Average high ozone days per year: 91.8
> Average 24-hour unhealthy particle pollution: 13.7
> Adults with asthma: 30,688
> Population: 468,680

2. Bakersfield, CA
> Average high ozone days per year: 95.2
> Average 24-hour unhealthy particle pollution: 41.0
> Adults with asthma: 60,364
> Population: 901,362

1. Los Angeles-Long Beach, CA
> Average high ozone days per year: 179.8
> Average 24-hour unhealthy particle pollution: 8.7
> Adults with asthma: 1,361,923
> Population: 18,629,661