Denver is among the most polluted cities
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The metro Denver area ranks as the eighth-most ozone-polluted region in the nation with an average of 30 high-ozone days a year, per the American Lung Association's 2026 "State of the Air" report.
Why it matters: Hundreds of thousands of people in the metro area — which includes Aurora and Greeley — have health conditions such as asthma that make them more susceptible to air pollution.
- Infants, children and teens are at increased risk because their lungs are still developing, experts noted.
State of play: As a whole, Colorado's air quality is improving, the report found, but ozone and particle pollution in certain areas remain problematic.
- Fort Collins and Loveland ranked as the 18th-worst in terms of ozone-polluted cities
- Jefferson County ranks 10th for ozone pollution, while Douglas County ranks 20th.
The other side: Colorado Springs is one of just three metro areas in the nation to see improvements and leave the worst list. It moved from 23rd worst to 54th.
- Grand Junction and Pueblo-Cañon City are at the top of the 25 cleanest cities for year-round particle pollution.
The big picture: Nearly half of Americans (44%) live in places with unhealthy levels of ozone or particle pollution.
- That's over 152 million people, and despite "decades of successful efforts to reduce sources of air pollution," the report says.