New Report Details Widespread Unhealthy Air Pollution in U.S.
A new report from the American Lung Association (ALA) finds that a significant portion of the U.S. population lives in areas with unhealthy air pollution levels. The findings are based on air quality data collected between 2022 and 2024.
Report Scope and Methodology
The ALA's 2025 "State of the Air" report is its 27th annual analysis. It grades air pollution levels across U.S. counties using three measures: ground-level ozone (smog), year-round particle pollution (soot), and short-term spikes in particle pollution.
Key Population Findings
Overall Exposure: The report states that 44% of the U.S. population, or approximately 152 million people, reside in counties that received a failing grade for at least one measure of air pollution.
Childhood Exposure: 33.5 million children under the age of 18, representing 46% of that demographic, live in such areas. Of those, 7 million children live in counties that failed all three pollution measures.
Ozone Exposure: 38% of the population, or about 129.1 million people, were exposed to unhealthy ozone levels during the reporting period. This represents an increase of 3.9 million people from the previous year's report.
Disparities in Exposure: According to the report, people of color are disproportionately affected. While making up 42.1% of the U.S. population, they represent 54.2% of those living in counties with at least one failing grade.
The report states a person of color is 2.42 times more likely than a white person to live in a county that fails all three pollution measures.
Pollution Trends and Factors
The report noted a mixed picture on particle pollution, with the number of people living in counties receiving an 'F' grade for short-term and year-round soot pollution described as lower than in previous reports.
It identified several factors contributing to current pollution levels:
- Extreme heat, drought, and wildfires.
- Smoke from Canadian wildfires in 2023.
- Weather patterns in 2023 and 2024 that favored ozone formation, particularly in Southern and Southwestern states.
- Climate change, which the report states can intensify ozone pollution by boosting precursor emissions and creating conditions for pollutants to build up.
- Data centers, cited as a growing source due to their electricity consumption and the use of diesel backup generators. The report notes data centers currently consume roughly 4.4% of total U.S. electricity.
Geographic Rankings
Most Polluted Metropolitan Areas
The ALA report listed the five most polluted metropolitan areas as:
- Bakersfield-Delano, California
- Brownsville-Harlingen-Raymondville, Texas
- Eugene-Springfield, Oregon
- Fresno-Hanford-Corcoran, California
- San Diego-Chula Vista-Carlsbad, California (tied with Visalia, California)
Bakersfield, California, ranked highest for year-round particle pollution.
Cleanest Cities for Year-Round Particle Pollution
- Bozeman, Montana
- Casper, Wyoming
- Kahului-Wailuku, Hawaii
- Urban Honolulu, Hawaii
- Burlington-South Burlington-Barre, Vermont
Regulatory and Policy Context
The report includes commentary on federal environmental policy. It cites the repeal by the U.S. Environmental Protection Agency (EPA) of the "endangerment finding" in February 2025, which had formally linked greenhouse gases to human health problems.
The report's authors wrote that the EPA "has recently acted to weaken, delay or revoke key health protections."
The report notes that since returning to office last year, the Trump administration has initiated numerous actions to roll back environmental regulations. These include loosening regulations on power plant emissions of mercury and other hazardous air toxics, overturning limits on major air pollution sources, and disbanding EPA advisory committees on air quality.
A separate annual review by the Swiss technology company IQAir placed El Paso, Texas, and Los Angeles, California, among the most polluted areas in the U.S. and found a 3% increase in U.S. pollution concentrations between 2024 and 2025.
According to EPA data, emissions of common air pollutants fell significantly after the Clean Air Act was enacted in 1970, but additional data show levels have been rising again in recent years.