According to the American Lung Association, Greater Los Angeles remains the most ozone-polluted metro area in the country. 2026 State of the Air ReportWhich found that Southern California is facing the dirtiest air in the country.
In the report released Wednesday, Los Angeles-Long Beach ranked as the worst U.S. metro area for ozone pollution, with an average of 159.2 unhealthy ozone days a year. The region ranks seventh worst nationally for annual particle pollution and seventh worst for short-term particle pollution.
The American Lung Association, or ALA, assigns grades based on the number of unhealthy air days and the severity of pollution levels, using federal air quality standards. Los Angeles County received failing grades in all three categories measured in the report: ozone, short-term particle pollution and annual particle pollution.
Riverside and San Bernardino counties also failed on all three measures.
Orange County received an F for ozone, a failing grade for annual particle pollution, and a C for short-term particle pollution.
Ground-level ozone, often called “smog”, is a corrosive gas that forms when pollution from vehicles and other sources reacts with heat and sunlight. It can irritate the lungs and cause serious breathing problems.
Short-term and annual particle pollution refers to fine particulate matter, known as PM2.5. These fine particles come from sources such as vehicle exhaust, industrial emissions and forest fires. Because they are small enough to enter the bloodstream, they are linked to asthma attacks, heart disease, stroke and lung cancer, according to Will Barrett, assistant vice president for nationwide clean air policy at ALA.
The report found some signs of progress. Los Angeles recorded its lowest annual particle pollution levels in the report’s history, even though the area is still one of the worst in the country.
On the other hand, ozone pollution in Los Angeles has worsened since last year’s report, leaving the metro area in the top spot nationally for smog. The report said Los Angeles has ranked among the worst for ozone in 26 of the 27 years in the study released by ALA.
Speaking to the press on Tuesday, Barrett said the region’s pollution comes largely from mass transportation sources “primarily burning gasoline and diesel” as well as refineries and other local emission sources. He said these pressures are linked to climate and coastal conditions that promote indoor pollution, especially in the Inland Empire, where unhealthy ozone days are even more severe.
Nationally, the report found that in the US, 152.3 million people, or 44% of the population, live in places that received a failing grade for at least one measure of ozone or particle pollution. This includes 33.5 million children, or 46% of people under the age of 18. In California, the ALA said 82% of residents live in counties affected by unhealthy air.
Of the 15 US counties with the worst smog days last year, eight were in California.
When it came to days with bad PM2.5 pollution, California had seven of the 15 worst counties.
And nine of the 15 counties with the worst PM2.5 pollution year-round were in California.
In the report, ALA said recent federal actions could undermine California’s efforts to improve air quality. These include missed deadlines for stronger particle pollution standards, rollbacks of clean-vehicle and fuel-economy rules, exemptions from toxic air pollution rules, and a Congressional Review Act challenge targeting three of California’s clean-vehicle standards.
“This (Environmental Protection Agency) is making significant changes to life-saving clean air rules,” Diana Van Vleet, lead author of the report and director of ALA’s nationwide clean air advocacy, said during a Tuesday press call. “Federal actions have weakened, delayed, and repealed many pollution limits.”
he referred to February repeal of EPA It is a long-standing scientific conclusion that man-made climate change threatens the health of Americans.
“The federal government’s recent actions to interfere with the state’s authority to protect the health of California residents are a major challenge to the ongoing success of our local air districts and the State Air Board,” Barrett said. He said state projections show that federal actions weakening California’s clean-air authority could lead to more than 14,000 deaths by 2050, thousands of emergency room visits and hospitalizations, and a cumulative health impact of $145 billion.
The report said children are particularly vulnerable to polluted air because their lungs are still developing, they breathe more air relative to their body size and often spend more time outdoors.
“In my daily working life, I treat children with asthma who are often made worse by heavy doses of pollution,” said Afif El-Hassan, physician in charge of Kaiser Permanente San Juan Capistrano Medical Office.
El-Hassan said air pollution “also inhibits lung development in children, which can lead to reduced lung capacity as adults. It can’t be reversed. Once that happens, it’s done.”
Southern California’s air pollution burden has long been shaped by a mix of traffic, freight, industry, geography, and climate.
County rankings reflect the intensity of that burden. San Bernardino County ranked as the most ozone-polluted county in the country with 159.2 weighted average unhealthy ozone days, followed by Riverside County at 126.7 and Los Angeles County at 119.0.
The report also highlighted clean air successes elsewhere in California. Sacramento recorded its lowest annual particle pollution level and fewest unhealthy ozone days in the history of the report.
Four California cities also ranked among the nation’s cleanest cities in at least one category: Salinas and Chico to record zero high-ozone days, and Santa Barbara and San Luis Obispo to record zero days of unhealthy particle pollution.
ALA urged state lawmakers to continue funding programs aimed at cutting emissions from the largest sources. “The Lung Association is asking the California Legislature to invest in zero-emission truck programs, as well as funding for clean farm equipment and consumer cars,” Barrett said.
Health and environmental arguments for these political positions have been strongly rejected, but Barrett says the economic consequences of dirty air are often ignored. “What is often missing is the impact of the cost of air pollution on family budgets, from children not going to school, their parents staying home from work, etc.,” he said. “Air pollution is a costly social problem that requires attention.”
