The Most Polluted U.S. Cities

Almost half of the U.S. population (46%) is now living with dangerous levels of air pollution, according to a new study from the American Lung Association. Their 2025 “State of the Air” report has just come out, revealing that 156-million Americans live in areas that received an “F” grade for either ozone or particle pollution.

  • That’s 25-million more people than last year’s numbers.
  • Overall, 42.5-million Americans live in counties with failing grades for all three types of air pollution measured.
  • The American Lung Association explains that extreme heat and wildfires contributed to worse air quality for people across the country.
  • Their 26th annual “State of the Air” report grades exposure to unhealthy levels of ground-level ozone pollution - also known as smog - and year-round short-term spikes in particle pollution - also known as soot - over a three-year period.
  • The research shows that cities in California are some of the most polluted in the U.S. when it comes to air quality.
  • The worst city overall for year-round particle pollution is Bakersfield-Delano, California. It’s also the most polluted by short-term particle pollution.
  • Los Angeles-Long Beach, California, is the city most polluted by ozone pollution, followed by Visalia, California, with Bakersfield-Delano in third.

The 10 Most Polluted Cities for Year-Round Particle Pollution

1: Bakersfield-Delano, California

2: Visalia, California

3: Fresno-Hanford-Corcoran, California

4: Eugene-Springfield, Oregon

5: Los Angeles-Long Beach, California

6: Detroit-Warren-Ann Arbor, Michigan

6: San Jose-San Francisco-Oakland, California

8: Houston-Pasadena, Texas

9: Cleveland-Akron-Canton, Ohio

10: Fairbanks-College, Alaska