What are California’s most polluted cities? See worst offenders for air quality

How bad is air pollution in California?

Five California cities ranked among the 10 most polluted metropolitan areas in the United States in the United States, in the latest American Lung Association’s 26th annual State of the Air Report.

Since 2000, the American Lung Association has issued report cards each year for U.S. cities and counties based on their scores for ozone, year-round particle pollution and short-term particle pollution levels.

The association said it uses the most recent data collected by the U.S. Environmental Protection Agency for the “two most widespread types of pollution” — ozone, commonly known as smog, and particle pollution, also known as soot.

Here’s where California cities ranked in the latest State of the Air report, released March 23.

How bad is air pollution in California cities?

The Los Angeles-Long Beach metropolitan area had the worst ozone pollution in the United States in 2025, ranking No. 1 out of 228 metro areas, according to the American Lung Association’s latest State of the Air report.

The Los Angeles-Long Beach metro area had an annual average of about 153.7 high ozone days from 2021 to 2023, the report said.

That’s 65 more high ozone days per year than the second-worst spot for ozone pollution in the nation.

Visalia had an annual average of 88.7 high ozone days, according to the report.

Visalia also ranked No. 2 in terms of metro areas with the worst year-round particle pollution, the American Lung Association said.

In terms of ozone pollution, Bakersfield was the third most polluted metro area in the United States, with an average of 72.8 high-ozone days per year.

Bakersfield ranked No. 1 among metro areas with the worst year-round particle pollution and short-term particle pollution, the report said.

The Fresno-Hanford-Corcoran metro area was ranked fifth with an average of 46.8 high ozone days each year, according to the American Lung Association.

The Central Valley metro area ranked third in the nation in terms of year-round particle pollution and fifth in terms of short-term particle pollution.

Out of the 10 U.S. cities with the worst ozone pollution, the San Diego-Chula Vista-Carlsbad metro ranked eighth with an annual average of 27.5 high ozone days, the report said.

The Sacramento-Roseville metro area was No. 10 on the association’s list of the U.S. cities with the worst short-term particle pollution

The area ranked No. 11 in the nation in terms of high ozone days and No. 14 among metro areas with the worst long-term particle pollution.

Did air quality improve in Sacramento? Fresno?

Out of the California cities that ranked the worst for ozone and particle pollution in 2025, the Fresno and Sacramento metropolitan areas improved the most compared to 2024, according to the American Lung Association.

The Fresno-Hanford-Corcoran metro area dropped one place after ranking No. 4 for ozone pollution in 2024.

Meanwhile, the Sacramento-Roseville metro area went down six places on the association’s list of the U.S. metro areas with the worst short-term particle pollution in 2025. It ranked No. 4 the previous year.

Which US cities have the worst ozone pollution?

These were the 10 most polluted metropolitan areas in the United States in terms of ozone, according to the American Lung Association:

1. Los Angeles-Long Beach
2. Visalia
3. Bakersfield
4. Phoenix-Mesa, Arizona
5. Fresno-Hanford-Corcoran
6. Denver-Aurora-Greeley, Colorado
7. Houston-Pasadena, Texas
8. San Diego-Chula Vista-Carlsbad
9. Salt Lake City-Provo-Orem, Utah
10. Dallas-Fort Worth, Texas

What are the top 10 worst cities for particle pollution?

These 10 metro areas had the worst year-round particle pollution in the nation in 2025, the State of the Air report said:

1. Bakersfield
2. Visalia

3. Fresno-Hanford-Corcoran

4. Eugene, Springfield, Oregon

5. Los Angeles-Long Beach

6. Detroit-Warren- Ann Arbor, Michigan

7. San Jose-San Francisco-Oakland

8. Houston-Pasadena, Texas

9. Cleveland-Akron-Canton, Ohio

10. Fairbanks-College, Alaska

These 10 metro areas topped the list for the locations with the worst short-term particle pollution in 2025:

1. Bakersfield

2. Fairbanks-College, Alaska

3. Eugene, Springfield, Oregon

4. Visalia

5. Fresno-Hanford-Corcoran

6. Reno-Carson City-Gardenville Ranchos, Nevada

7. Los Angeles-Long Beach

8. Yakima, Washington

9. Seattle-Tacoma, Washington

10. Sacramento, Roseville

How did American Lung Association come up with rankings?

To create its 2025 State of the Air Report, the American Lung Association said it graded metropolitan areas and counties across California for ozone, year-round particle pollution and short-term particle pollution levels using data from 2021, 2022 and 2023, the most recent “quality-assured nationwide air pollution data publicly available.”

Data came from the U.S. Environmental Protection Agency’s Air Quality System.

This story was originally published April 29, 2025 at 5:00 AM with the headline "What are California’s most polluted cities? See worst offenders for air quality."

Fernanda Galan

The Fresno Bee

559-441-6005

Fernanda Galan covers Central Valley and California news as The Fresno Bee’s service journalism reporter. Before joining The Bee in 2024, she reported in Milwaukee, Arizona and Los Angeles. She is a graduate of Arizona State’s Walter Cronkite School of Journalism and Mass Communication.