California is home to eight of the 25 smoggiest metro areas in the nation, including one region that's consistently been ranked as having the country's very worst air quality for decades, according to an annual report by the American Lung Association.
The Los Angeles-Long Beach metro areas has ranked No. 1 for smog (ozone) pollution on the association's "State of the Air" report for 26 of the past 27 years. The metro includes Ventura, Los Angeles, Orange, Riverside and San Bernardino counties.
This year, the metro — along with a long list of other California regions — also received poor marks in rankings of particulate matter pollution. However, five metro areas in the state appeared on the association's list of least-polluted regions.
The association said nearly half of U.S. children — about 33.5 million — are breathing unhealthy levels of air pollution, with 152 million people overall living in areas that received failing grades for smog (ozone) or particle pollution.
The report, based on 2022–2024 data, evaluates counties for ground-level ozone and both short- and long-term particle pollution, ranking the cleanest and most polluted areas nationwide.
Researchers warned that despite decades of progress under the Clean Air Act, worsening wildfires, extreme heat, and recent federal rollbacks of environmental protections threaten air quality gains and could expose more people, especially children, to harmful pollution.
Children are particularly vulnerable because their lungs are still developing.
Exposure to unsafe air is linked to asthma, reduced lung growth, cognitive disorders, and an increased risk of disease later in life. Pollution has also been linked to heart attacks, strokes, premature death, and lung cancer.
The report also found disparities, with people of color more than twice as likely as white residents to live in communities with failing grades for all major pollution measures.
Eight of the country's top 25 metro areas for ozone pollution are in California:
Six of the top 25 metro areas for short-term particulate matter are in California:
Seven of the top 25 metro areas for year-round particle pollution are in California:
By contrast, several smaller metro areas ranked among those with the cleanest air across all three categories, including Bangor, Maine, which made the list for all three measures.
Two California metro areas were ranked among the nation's 25 cleanest based on year-round particle pollution:
Additionally, Chico and Salinas appeared on an unranked list of cleanest cities based on ozone pollution. The San Luis Obispo-Paso Robles area and Santa Maria-Santa Barbara appeared on a similar list based on short-term particle pollution.
Californians who want to know the quality of the air they’re breathing can use this tool that sorts data by county and ZIP code.
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