At EPA's AirCompare site, you can compare the air quality of different counties in the US. AirCompare will tell you the number of unhealthy air quality days in an area. You also have the option to base the number of unhealthy days on a specific health concern such as asthma or lung disease. To get the most complete picture of an area's air quality, be sure to check the "historical profiles" and "monthly profiles." AirCompare is located at https://www3.epa.gov/aircompare.