Where to live with asthma: counties with the fewest bad-air days
If you or your child has asthma, the number of smoky and ozone days a year where you live matters. Set the most you'd accept and the map shows which counties fit. With the starting settings, 159 counties of 250,000 people or more qualify, home to 98 million people.
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Large counties with the cleanest air
Counties of 250,000 people or more with at most 2 smoke and dust days and 5 ozone days a year, fewest bad-air days first. Each one is a day the EPA advises people with asthma to cut back on time outdoors.
| County | Smoke and dust days | Ozone days |
|---|---|---|
| San Mateo County, CA | 0.0 | 0.0 |
| St. Lucie County, FL | 0.0 | 0.0 |
| Buncombe County, NC | 0.0 | 0.0 |
| Marin County, CA | 0.0 | 0.0 |
| Palm Beach County, FL | 0.2 | 0.0 |
| San Francisco County, CA | 0.2 | 0.0 |
| Lee County, FL | 0.0 | 0.2 |
| Brevard County, FL | 0.2 | 0.0 |
| Pasco County, FL | 0.0 | 0.2 |
| Volusia County, FL | 0.2 | 0.0 |
| Monterey County, CA | 0.2 | 0.0 |
| Mobile County, AL | 0.0 | 0.2 |
| Charleston County, SC | 0.2 | 0.0 |
| Manatee County, FL | 0.0 | 0.2 |
| Lake County, FL | 0.0 | 0.2 |
| Collier County, FL | 0.2 | 0.0 |
| Lexington County, SC | 0.2 | 0.0 |
| Alachua County, FL | 0.2 | 0.0 |
| St. Johns County, FL | 0.0 | 0.2 |
| Santa Cruz County, CA | 0.2 | 0.0 |
| Polk County, FL | 0.2 | 0.2 |
| Sonoma County, CA | 0.4 | 0.0 |
| Seminole County, FL | 0.4 | 0.0 |
| Sarasota County, FL | 0.2 | 0.2 |
| Osceola County, FL | 0.0 | 0.4 |
What else to weigh
Bad-air days are one part of the picture. Pollen, mold, humidity, cold air and indoor triggers such as smoke and dust mites also set off asthma, according to the CDC. A county with clean outdoor air can still be hard on someone allergic to its pollen.
County numbers are averages for the worst spot in each county. A home near a highway or in a valley that traps smoke can have worse air than the county as a whole. Before a move, look at the county page and talk with your doctor about what matters most for you.
Questions people ask about asthma and where to live
What are the best places to live with asthma?
Going by outdoor air alone, the large counties with the fewest smoke, dust and ozone days are San Mateo County, CA; St. Lucie County, FL; Buncombe County, NC; Marin County, CA; Palm Beach County, FL; San Francisco County, CA. Pollen, mold and humidity matter too, so the best place depends on your triggers.
Does this include the 2023 Canadian wildfire smoke?
For counties with EPA monitors, yes: the finder uses their counts for 2021 to 2025. Where there is no monitor, it falls back on CDC's estimates, which end in 2022, so the 2023 smoke isn't in those numbers.
Is the air better on the coast?
Often. Sea breezes move pollution inland, and many coastal counties in Florida, Washington and northern California average under 1 ozone day a year. Southern California is the big exception: Los Angeles, Riverside and San Bernardino counties have some of the most ozone days in the country.
How many bad-air days a year is too many for someone with asthma?
There's no official cutoff. On any day with an AQI over 100, the EPA advises people with asthma to cut back on long or hard outdoor activity. Counties with 1 or 2 such days a year mean a few days of planning; counties with 30 or more mean a whole season of it.
These maps use the CDC Environmental Public Health Tracking Network's daily estimates of fine particles (PM2.5) and ozone for every county in the lower 48, 2001 to 2022. A bad-air day is a day when the worst spot in a county goes over 35.4 µg/m³ of fine particles or 70 ppb of ozone, where the AQI passes 100. How we count · Download the data