A new report shows the state of air quality across the United States, identifying metro areas facing the greatest pollution challenges in 2026.
The American Lung Association’s 27th annual “State of the Air” report assesses ozone and particulate pollution levels in counties, states and metropolitan areas.
Ground-level ozone remains one of the most persistent threats to U.S. urban air quality. Formed when emissions from vehicles, industrial facilities and other sources react in sunlight, ozone It is the main component of smog.
experts warn temperature rise is exacerbating the problem. Warmer climate accelerates ozone formation, leading to more frequent ozone peaks in the summer. These increases often trigger health advisories, especially in densely populated cities.
Vulnerable groups including children, the elderly and people with respiratory illnesses are most at risk. Long-term exposure has been linked to asthma attacks, cardiovascular disease and other serious health problems.
Also read: Global temperature exceeds 1.5°C threshold for first time in three consecutive years
California cities dominate rankings
The report’s rankings show that the most polluted cities are concentrated in californiaLos Angeles and Long Beach, California, tops the list of the most ozone-polluted metropolitan areas in the United States.
This was followed by Visalia, California, and Bakersfield-Delano, California, which also reported high levels of particle pollution. Several other California regions, including Fresno-Hanford-Corcoran and San Diego-Chula Vista-Carlsbad, also stand out.
“Despite decades of progress, too many people in California still live with unhealthy air pollution,” said Will Barrett, the American Lung Association’s assistant vice president for national clean air policy.
Also read: Weather Bee: How much global warming is expected in 2026
Every metropolitan area in the U.S. is affected
In addition to California, other major urban areas are among the most polluted. Phoenix-Mesa, Arizona (No. 4), Houston-Pasadena, Texas (No. 6), and Denver-Aurora-Greeley, Colorado (No. 8) all reported higher ozone levels.
Industrial activity remains a major factor in cities like Houston, with emissions from petrochemical facilities contributing significantly to pollution levels.
Meanwhile, metropolitan areas such as New York-Newark, New York-New Jersey-Connecticut-Pennsylvania (No. 12) and Chicago-Naperville, Illinois-Wisconsin (No. 15) also made the list.
Full list of worst affected cities
The 15 U.S. metro areas with the worst air pollution in 2026 are:
Los Angeles-Long Beach, CA
Visalia, California
Bakersfield-Delano, California
Phoenix-Mesa, Arizona
Fresno-Hanford-Corcoran, California
Houston-Pasadena, Texas
San Diego-Chula Vista-Carlsbad, CA
Denver-Aurora-Greeley, Colorado
Dallas-Fort Worth, TX-OK
El Centro, California
Las Vegas-Henderson, Nevada
New York-Newark, NY-NJ-CT-PA
Salt Lake City-Provo-Orem(UT-ID)
San Jose-San Francisco-Oakland, CA
Chicago-Naperville, IL
The report states that approximately 33.5 million children in the United States (nearly 46% of children under the age of 18) live in areas that fail at least one air pollution indicator.
