Here Are the U.S. Cities With the Worst Air Pollution in 2024

California cities make up a large portion of them.

Air pollution continues to present a major issue for many Americans living in cities. Between auto emissions and natural phenomena like wildfires, breathing in this air can present a bevy of health problems down the line. 

The American Lung Association just released its "State of the Air" report for 2024, which analyzes air quality in metropolitan areas across country and tracks two of the most dangerous air pollutants: fine particles and ozone. 

Once again, Bakersfield, California topped the list for the worst short-term particle pollution, and also ranked as the metropolitan area with the worst level of year-round particle pollution for the fifth year in a row. On the other side of the Tehachapi Mountains, Los Angeles — long known for its smog — has the worst ozone pollution in the nation, as it has been for 24 of the 25 years the "State of the Air" report has been released. California cities make up a large portion of these locations, despite having the country's strictest emission requirements. In total, nearly four in 10 Americans are estimated to be living in an area with unhealthy levels of air pollution. 

Most of the polluted cities are in the West, and the association chalked it up to a combination of "policy-driven reductions in emissions on the one hand and climate change-fueled increases in pollution on the other hand." 

"[This has] resulted in an ongoing and marked disparity between air quality in eastern and western states, especially for the daily measure of fine particle pollution," they wrote. "In this year’s report, only four large counties in three states east of the Mississippi River earned failing grades for daily spikes in fine particle pollution, compared to 108 counties in 16 western states."

These are the top 10 most-polluted metropolitan areas by annual particulate matter levels. 

1. Bakersfield, California
2. Visalia, California
3. Fresno–Madera–Hanford, California
4. Eugene–Springfield, Oregon
5. San Jose–San Francisco–Oakland, California
6. Los Angeles–Long Beach, California
7. Sacramento–Roseville, California
8. Medford–Grants Pass, Oregon
9. Phoenix–Mesa, Arizona
10. Fairbanks, Alaska 

And when it comes to ozone, the L.A. area easily trumps the rest of the competition. 

1. Los Angeles–Long Beach, California
2. Visalia, California
3. Bakersfield, California
4. Fresno–Madera–Hanford, California
5. Phoenix–Mesa, Arizona
6. Denver–Aurora, Colorado
7. Sacramento–Roseville, California
8. San Diego–Chula Vista–Carlsbad, California
9. Salt Lake City–Provo–Orem, Utah
10. Houston–The Woodlands, Texas