Year-Round Particle Pollution Trends

More than 20.9 million people, approximately 6.4% of the nation, live in one of the 17 counties where year-round particle pollution levels are worse than the national air quality limit, and that receive a failing grade in “State of the Air” 2021. The number of people living in counties with unhealthy levels of year-round particle pollution is slightly smaller than in last year’s report, but higher than in reports published in 2017, 2018 and 2019.

Of the 25 cities most polluted year-round by particle pollution in the U.S., 13 suffered worse year-round levels during 2017, 2018 and 2019 than in last year’s report, and two reported their worst ever. In contrast, 10 of the 25 most polluted cities had lower year-round levels, of which three achieved their lowest levels ever. Across all 25 cities, the year-round levels of particle pollution worsened only very slightly.

There was a good deal of shuffling positions on the list of 25 most polluted cities this year. Three cities improved enough to leave the list: Birmingham, Alabama; Atlanta, Georgia and Brownsville, Texas. Three cities saw their air quality deteriorate enough in 2017, 2018 and 2019 to be added to the list (See Figure 3).

In “State of the Air” 2021, 15 of the 25 worst cities for year-round particle pollution are in the western U.S.: eight in California, three in the Southwest and four in the Pacific Northwest. Because of their higher frequency, greater severity, longer duration, and increasing proximity to populated areas, the western wildfires contributed significantly to the elevated year-round levels in many western cities.

Cities with high power plant emissions as well as local, industrial sources continue to show up on the list, although with less frequency than in the past. These include Pittsburgh, Philadelphia, New York-Newark, Detroit, Cincinnati, Cleveland, Chicago, Houston, Indianapolis, and Shreveport.

Except for continuing problems from western wildfires, year-round particle pollution continues to improve across most of the nation, unlike the days with high ozone and high short-term particle pollution. All cities but the nine most-polluted meet the current national air quality standards set by the U.S. Environmental Protection Agency, and receive a passing mark in “State of the Air” 2021. However, evidence shows that no threshold exists for harmful effects from particle pollution, even below the official standard.


Did You Know?

  1. More than 4 out of 10 people live where the air they breathe earned an F in State of the Air 2020.
  2. 150 million people live in counties that received an F for either ozone or particle pollution in State of the Air 2020.
  3. More than 20.8 million people live in counties that got an F for all three air pollution measures in State of the Air 2020.
  4. Breathing ozone irritates the lungs, resulting in something like a bad sunburn within the lungs.
  5. Breathing in particle pollution can increase the risk of lung cancer, according to the World Health Organization.
  6. Particle pollution can also cause early death and heart attacks, strokes and emergency room visits for people with asthma and cardiovascular disease.
  7. Particles are 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. Do you live near, or work on or near a busy highway? Pollution from the traffic 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 infants, older adults and people with lung diseases like asthma.
  12. People of color and those earning lower incomes are often disproportionately affected by air pollution that put them at higher risk for illnesses.
  13. Air pollution is a serious health threat. It can trigger asthma attacks, harm lung development in children, and can even be deadly.
  14. You can protect your family by checking the air quality forecasts in your community and avoiding exercising or working outdoors when the unhealthy air is expected.
  15. Climate change enhances conditions for ozone to form and makes it harder to keep ozone from forming.
  16. Climate change increases the risk of wildfires that spread particle pollution and ozone in the smoke.
  17. This Administration is trying to roll back or create loopholes in core healthy air protections under the Clean Air Act. The Lung Association opposes these actions that will add pollution to the air we breathe.
  18. Cutting air pollution through the Clean Air Act will prevent at least 230,000 deaths and save $2 trillion annually by 2020.
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