Is air quality getting better? County by county, 2001 to 2022
For most of the country, yes. The average American's county had about 27 high-ozone days a year in the early 2000s and about 8 from 2018 to 2022. High-particle days fell from about 8 to 2. Wildfire smoke has pushed the other way in parts of the West.
people live in counties with fewer bad-air days than in the early 2000s
live in counties with more, mostly in the West
was the worst ozone year: about 34 high-ozone days where the average American lived
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The national trend
Bad-air days a year for the average American, by where they live. Brown is fine particles; blue is ozone.
The numbers behind the chart
Ozone fell the most. It forms when pollution from cars, power plants and industry reacts in sunlight, and the 2 main ingredients dropped sharply: nitrogen oxide emissions fell 73% and volatile organic compounds 46% from 1990 to 2023, according to the EPA's air trends report. Particle days fell too, with bumps in big wildfire years such as 2020.
Most improved large counties
Counties of 250,000 people or more. Bad-air days a year, 2001 to 2005 compared with 2018 to 2022. The tag says what drove most of the change.
Large counties getting worse
Same counties and years. In the West, rising particle days come mostly from wildfire smoke.
Questions people ask about air quality trends
Is air quality in the US getting better?
Mostly. For the average American, high-ozone days fell from about 27 a year in 2001 to 2005 to about 8 in 2018 to 2022, and smoky days (fine particles over 35.4 µg/m³, mostly smoke) fell from about 8 to 2. 297 million people live in counties with fewer bad-air days than in the early 2000s.
Where is air quality getting worse?
In 311 counties, home to 22 million people, mostly in the West. Large counties with the biggest increases include Washoe County, NV (5 to 25 days); Snohomish County, WA (1 to 8 days); Clackamas County, OR (5 to 12 days). Most of the rise there is fine particles from wildfire smoke.
Why did ozone go down?
Ozone forms when pollution from cars, power plants and industry reacts in sunlight. The EPA reports that US emissions of nitrogen oxides fell 73% and volatile organic compounds 46% from 1990 to 2023, which it credits to the Clean Air Act and cleaner technology. With less of both, less ozone forms on hot days.
Does this include the 2023 Canadian wildfire smoke?
No. CDC's county estimates end in 2022. County pages on this site use EPA monitor readings through 2025, which do include 2023.
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