Key Findings

Learn the key findings and overall trends about air quality in states and cities in the American Lung Association's State of the Air report.
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The “State of the Air” 2025 report finds that even after decades of successful efforts to reduce sources of air pollution, 46% of Americans—156.1 million people—are living in places that get failing grades for unhealthy levels of ozone or particle pollution. This is nearly 25 million more people breathing unhealthy air compared to last year’s report, and more than in any other “State of the Air” report in the last ten years.

more than one in three

Nearly half of the U.S. population live with unhealthy levels of air pollution

Extreme heat, drought and wildfires are contributing to worsening levels of air pollution across much of the U.S., exposing a growing proportion of the population to ozone and particle pollution that put their health at risk.

The “State of the Air” report looks at two of the most widespread and dangerous air pollutants, fine particles and ozone. The air quality data used in the report are collected at official monitoring sites across the United States by federal, state, local and Tribal governments. The Lung Association calculates values reflecting the air pollution problem and assigns grades for daily and long-term measures of particle pollution and daily measures of ozone. Those values are also used to rank cities (metropolitan areas) and counties. This year’s report presents data from 2021, 2022 and 2023, the most recent three years of quality-assured nationwide air pollution data publicly available. See About This Report for more detail about the methodology for data collection and analysis.

“State of the Air” 2025 is the 26th edition of this annual report, which was first published in 2000. From the beginning, the findings in “State of the Air” have reflected the successes of the Clean Air Act, as emissions from transportation, power plants and manufacturing have been reduced over time. Over the last decade, however, the findings of the report have added to the extensive evidence that a changing climate is making it harder to protect this hard-fought progress on air quality and human health. Increases in high ozone days and spikes in particle pollution related to extreme heat, drought and wildfires are putting millions of people at risk and adding challenges to the work that states and cities are doing across the nation to clean up air pollution.

Circle graphic with 3.6X overlayed.

A changing climate is making the job of cleaning up the air more difficult

After several years of reporting that the worst of the nation’s air quality problems were increasingly concentrated in western states, “State of the Air” 2025 finds the geographic distribution of air pollution shifting back East. The year 2023, which is included in this year’s report for the first time, brought improved conditions to the west coast but also a deadly heat wave in Texas and an unprecedented blanket of smoke from wildfires in Canada that drove levels of ozone and particle pollution in dozens of central and eastern states higher than they have been in many years.

Again this year, “State of the Air” finds that the burden of living with unhealthy air is not shared equally. Research has shown that communities of color are disproportionately exposed to unhealthy air and are also more likely to be living with one or more chronic conditions that make them more vulnerable to air pollution, including asthma, diabetes and heart disease. Although people of color make up 41.2% of the overall population of the U.S., they are 50.2% of the people living in a county with at least one failing grade. Notably, Hispanic individuals are nearly three times as likely as white individuals to live in a community with three failing grades.

In “State of the Air” 2025, the metropolitan areas that ranked worst in the country for each of the three pollutant measures are unchanged from last year’s report. Bakersfield, California tops the list for worst short-term particle pollution for the third straight year. Bakersfield also continues to be the metropolitan area with the worst level of year-round particle pollution for the 6th year in a row. Los Angeles is the city with the worst ozone pollution in the nation, as it has been in 25 of the 26 years of reporting in “State of the Air”– although city residents are exposed to 77 fewer days each year, or two and a half months’ worth, with unhealthy levels of ozone, on average, than they were in 2000.

More Findings

Ozone Trends

Exposure to unhealthy levels of ozone air pollution continues to make breathing difficult for millions of Americans.
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Short-Term Particle Pollution Trends

Many cities reached their highest number of days with unhealthy levels of particle pollution ever reported.
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Year-Round Particle Pollution Trends

More than 20.9 million people live where year-round particle pollution levels are worse than the national air quality limit.
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Populations at Risk

Some groups of people are especially vulnerable to illness and death from exposure to unhealthy levels of air pollution.
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Most Polluted Places

See the 25 most polluted counties for ozone and particle pollution ranked.
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Cleanest Places to Live

Ten cities rank on all three cleanest cities lists for ozone, year-round and short-term particle pollution.
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Recommendations for Action

We need action at every level to clean up air pollution and address climate change.
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Did You Know?

  1. Nearly half of the people in the U.S. live where the air they breathe earned an F in “State of the Air” 2025.
  2. More than 156 million people live in counties that received an F for either ozone or particle pollution in “State of the Air” 2025.
  3. More than 42 million people live in counties that got an F for all three air pollution measures in “State of the Air” 2025.
  4. Breathing ozone irritates the lungs, resulting in inflammation—as if your lungs had a bad sunburn.
  5. Breathing in particle pollution can increase the risk of lung cancer.
  6. Particle pollution can cause early death and heart attacks, strokes, and emergency room visits.
  7. Particles in air pollution can be smaller than 1/30th the diameter of a human hair. When you inhale them, they are small enough to get past the body's natural defenses.
  8. Ozone and particle pollution are both linked to increased risk of premature birth and lower birth weight in newborns.
  9. If you live or work near a busy highway, traffic pollution may put you at greater risk of health harm.
  10. People who work or exercise outside face increased risk from the effects of air pollution.
  11. Millions of people are especially vulnerable to the effects of air pollution, including children, older adults, and people with lung diseases such as asthma and COPD.
  12. People of color and people with lower incomes are disproportionately affected by air pollution that puts them at higher risk for illness.
  13. Air pollution is a serious health threat. It can trigger asthma attacks, harm lung development in children, and even be deadly.
  14. You can protect yourself by checking the air quality forecast in your community and avoiding exercising or working outdoors when unhealthy air is expected.
  15. Climate change enhances conditions for ozone pollution to form and makes it harder to clean up communities where ozone levels are high.
  16. Climate change increases the risk of wildfires whose smoke spreads dangerous particle pollution.
  17. Policymakers at every level of government must take steps to clean the air their constituents breathe.
  18. The nation has the Clean Air Act to thank for decades of improvements in air quality. This landmark law has successfully driven pollution reduction for over 50 years.
  19. The U.S. Environmental Protection Agency is critical for cleaning up air pollution. EPA’s staff ensure that air pollution is monitored, write sound rules to clean it up, and make sure those rules are enforced.
  20. The U.S. Environmental Protection Agency is under threat. Despite EPA’s lifesaving role in protecting people’s health from air pollution, big staffing and funding cuts are endangering their work.
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