Exposure to unhealthy levels of ozone air pollution continues to make breathing difficult for millions of Americans all across the country. In the years 2018, 2019 and 2020, more than 122.3 million people lived in the 156 counties that earned an F for ozone. That is fewer than in the past four reports, but more than the 116.5 million people in the 2017 report. There are still a lot of vulnerable people, including 27.8 million children and 18.5 million people age 65 or older, who are exposed to ozone air pollution and face an increased risk of harm.

3 out of 8 Americans live in counties with F grades for ozone

3 out of every 8 Americans live in counties with F grades for ozone smog.

The list of 25 cities with the worst ozone pollution in “State of the Air” 2022 and their order of ranking remained relatively stable compared with last year’s report. Cities that improved enough to move off the list were Milwaukee and Sheboygan, Wisconsin; Philadelphia; and the Washington-Baltimore metro area. They were replaced by San Luis Obispo, Reno, Detroit and San Antonio.  

Cities in the West and the Southwest continue to dominate the most ozone-polluted list. California retains its historic distinction of having the most cities on the list, with 11 of the 25 most-polluted cities. The Southwest fills most of the remaining slots, with an equal number. In this year’s report, only three of the worst 25 cities for ozone are east of the Mississippi River. And no metropolitan areas in the Pacific Northwest, the Mid-Atlantic or the Southeast rank among the 25 worst cities most polluted by ozone. 

Overall, the 25 most ozone-polluted cities in the U.S. experienced fewer bad air days on average from 2018 to 2020 than did those in last year’s report covering 2017 to 2019. Five California cities on the list plus the New York metro area recorded their fewest days of high ozone in the report’s 23-year history, although three of them are still among the ten most ozone-polluted cities in the nation. 

The geographical distribution of cities with the worst ozone problems continues a trend seen over the past six reports: fewer eastern cities and more western cities. Oil and gas extraction and population growth in the Southwest and improved cleanup of power plants in the East have shifted the cities that experienced the greatest number of unhealthy ozone days. However, there are still problems in the East, not only from mobile sources and industry, but also from transported pollution when ozone and ozone precursors enter from upwind sources, nearby and even from as far as the Midwest. For example, Fairfield County, Connecticut is the county with the highest ozone in the eastern half of the nation, in part because of pollution transported from other states.  

Thermometer with arrow pointing up

The three years covered by State of the Air 2022 ranked among the seven hottest years on record globally.

Higher temperatures over longer periods also make a difference. Although cleanup of ozone precursor pollutants has been working to reduce ozone concentrations, climate change, with its higher temperatures and more frequent stagnation events, plays a significant role in making the number of unhealthy ozone days higher than it would otherwise be. Simply, climate change is undercutting the progress we would have made. The Lung Association continues to advocate for standards more protective of health for ozone pollution that better reflect the current science. See Recommendations for Action for details.

Did You Know?

  1. More than four in ten Americans live where the air they breathe earned an F in “State of the Air” 2022.
  2. More than 137 million people live in counties that received an F for either ozone or particle pollution in “State of the Air” 2022.
  3. Close to 19.8 million people live in counties that got an F for all three air pollution measures in “State of the Air” 2022.
  4. Breathing ozone irritates the lungs, resulting in inflammation—as if there were a bad sunburn within the lungs.
  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 lower birth weight in newborns.
  9. If you live or work near a busy highway, traffic pollution may put you at greater risk of 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.
  12. People of color and those earning 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 forecasts 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 clean up communities where ozone levels are high.
  16. Climate change increases the risk of wildfires that spread particle pollution in the smoke.
  17. The Biden Administration has made bold commitments to improve air quality, especially in communities that have faced disproportionate levels of pollution. The Lung Association is advocating to make sure they are realized.
  18. The nation has the Clean Air Act to thank for decades of improvements in air quality. This landmark law has driven pollution reduction for 50 years.
  19. Cutting air pollution through the Clean Air Act was projected to prevent over 230,000 deaths and save nearly $2 trillion in 2020 alone.
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  1. NOAA National Centers for Environmental Information, Global Climate Report--Annual 2017, published online January 2018. Accessed at https://www.ncdc.noaa.gov/sotc/global/201713