Phoenix's ozone levels are among the highest in the nation, but our overall air quality improved enough in recent years to knock us off the 2025 list of the 25 most polluted U.S. cities, according to the American Lung Association's State of the Air report released today.
Why it matters: Even with the slight improvement, Maricopa County still received an "F" grade for the number of days with high ozone and particle pollution.
Neighboring Pinal County was ranked one of the 25 most polluted counties in the country.
How it works: The report uses local air quality data to grade and rank locations based on ozone pollution, daily particle pollution and annual particle pollution.
The latest report includes data from 2021-2023, "the most recent three years of quality-assured nationwide air pollution data publicly available."
Ozone is a gas that, at ground level, is a harmful irritant. Particle pollution involves tiny airborne particles from wildfires, fossil fuel burning and more.
The big picture: Just over 156 million Americans — 46% of the population — live in areas with unhealthy levels of ozone or particle pollution, per the report.
Extreme heat, wildfires and drought are degrading air quality nationwide, the Lung Association says. All have been linked to climate change.
