The most polluted cities, by ozone pollution:

1. Los Angeles - Long Beach - Riverside, CA
2. Bakersfield, CA
3. Visalia - Porterville, CA
4. Houston - Baytown - Huntsville, TX
5. Fresno - Madera, CA
6. Sacramento - Arden - Arcade - Yuba City, CA - NV
7. Dallas - Fort Worth, TX
8. New York - Newark - Bridgeport, NY - NJ - CT - PA
9. Washington - Baltimore - Northern Virginia, DC - MD - VA - WV
10. Baton Rouge - Pierre Part, LA