Using EPA Air Quality System annual data, we've compiled a ranking of US cities by air quality. Rankings are based on median AQI scores — a better indicator of typical conditions than averages skewed by extreme events.
Methodology
We analyzed annual AQI data for counties with populations over 50,000, using the most recent full year of available EPA data. Cities are ranked by their county's median AQI (lower is better), with tiebreakers going to the number of "Good" days per year.
Top Cities for Clean Air
Honolulu, HI consistently tops the list, benefiting from ocean breezes and geographic isolation from industrial pollution. The islands see median AQI readings in the 20–30 range.
Coastal Pacific Northwest cities like Bellingham, WA and Port Angeles, WA regularly rank highly thanks to prevailing ocean winds — though wildfire smoke has become an increasingly significant issue in summer months.
Rural Mountain West cities often benefit from high elevation and low population density, though they're vulnerable to smoke events.
Cities Making the Most Improvement
Several cities have made dramatic improvements over the past decade:
- Pittsburgh, PA — once among the most polluted US cities, has improved significantly following industrial changes and EPA enforcement
- Los Angeles, CA — still struggles with ozone but has vastly improved from its 1970s peak
- Salt Lake City, UT — winter inversions remain a challenge, but summer air quality has improved
Most Polluted Cities
The most polluted cities by annual AQI tend to be in the San Joaquin Valley (Fresno, Bakersfield, Visalia) due to geography that traps pollution, and the Intermountain West during wildfire season.
See Full Rankings
Browse our complete rankings for the best and worst air quality cities across all 50 states.