20. Chico, CA
> Average high ozone days per year: 10.8
> Average 24-hour unhealthy particle pollution: 23.0
> Adults with asthma: 15,926
> Population: 212,744
19. San Luis Obispo-Paso Robles, CA
> Average high ozone days per year: 11.0
> Average 24-hour unhealthy particle pollution: 7.7
> Adults with asthma: 21,870
> Population: 282,249
18. Fort Collins, CO
> Average high ozone days per year: 14.5
> Average 24-hour unhealthy particle pollution: 4.8
> Adults with asthma: 27,972
> Population: 360,428
17. Chicago-Naperville, IL-IN-WI
> Average high ozone days per year: 16.0
> Average 24-hour unhealthy particle pollution: 0.8
> Adults with asthma: 663,501
> Population: 9,770,485
16. Dallas-Fort Worth, TX-OK
> Average high ozone days per year: 16.0
> Average 24-hour unhealthy particle pollution: 2.3
> Adults with asthma: 459,236
> Population: 8,186,093
