America's 25 Most Ozone-Polluted Metropolitan Areas, 2009
Updated February 21, 2017 | Factmonster Staff 
Each year the American Lung Association issues their "State of the Air" report. They track year-round and short-term particle pollution as well as the ozone pollution listed here. Though ozone pollution isn't the obvious, sooty kind of pollution, it can still be harmful to your health. Studies have shown that ozone pollution can worsen conditions such as bronchitis, asthma, emphysema, and cardiovascular disease.
| Rank | City |
|---|---|
| 1. | Los Angeles, CA |
| 2. | Bakersfield, CA |
| 3. | Visalia-Porterville, CA |
| 4. | Fresno-Madera, CA |
| 5. | Sacramento, CA |
| 6. | Hanford, CA |
| 7. | Houston, TX |
| 8. | San Diego, CA |
| 9. | San Luis Obispo, CA |
| 10. | Charlotte, NC |
| 11. | Phoenix, AZ |
| 12. | Merced, CA |
| 13. | Dallas-Fort Worth, TX |
| 14. | Knoxville, TN |
| 15. | El Centro, CA |
| 16. | New York, NY |
| 16. | Baltimore/DC, MD |
| 18. | Cincinnati OH |
| 19. | Atlanta, GA |
| 19. | Birmingham, AL |
| 21. | Las Vegas, NV |
| 22. | Modesto, CA |
| 22. | Philadelphia, PA |
| 24. | Chico, CA |
| 25. | Baton Rouge, LA |
Source: State of the Air: 2009, American Lung Association.
