Short-Term Particle Pollution Trends

In the years 2018, 2019 and 2020, some 63.2 million people lived in the 96 counties that earned an F for unhealthy spikes in particulate matter air pollution. This represents close to 8.9 million more people over a larger area than in last year’s “State of the Air” report, and more people than in any of the last seven reports—since the current version of the Air Quality Index was adopted.

U.S. map with 63 MM

More than 63 million Americans live in counties with F grades for spikes in daily particle pollution

Even compared with the past two years of “State of the Air” reports—in which many cities and counties experienced their highest weighted average number of days ever reported for fine particle pollution—results this year were again worse throughout much of the western U.S.

Among those cities ranked in the worst 25, more had poorer air quality than showed improvement, with the weighted average number of days with high levels of fine particle pollution worsening on average by 3.6 (from 12.9 to 16.5), a 28% increase. Eight cities on this list posted their highest-ever weighted average number of days with unhealthy levels of particle pollution and two, Fairbanks, Alaska and Redding-Red Bluff, California, did so for their third report in a row. 

Twenty of last year’s worst 25 cities remained listed among the 25 worst in this year’s report, though their relative ranks shifted around quite a bit. The five cities new to the list in 2022 were Salinas, San Luis Obispo and San Diego in California; Boise, Idaho and Bellingham, Washington. 

Missoula, Montana; El Centro and Santa Barbara, California; Lancaster, Pennsylvania and Las Vegas all moved off the list of worst 25 cities. However, in two of these (Lancaster and Las Vegas), the air quality actually got worse. In fact, because the weighted averages for fine particles worsened so much generally, all five of these cities, plus Denver and Fort Collins, Colorado, posted weighted averages for particle pollution in the 2022 report higher than that of the 25th-ranked city in last year’s report.   

Of all 25 cities, only one, Salt Lake City, posted its best performance ever for this pollutant—as it had in last year’s report. Its rank improved to 20th worst in this year’s report, from 17th last year, and 7th worst two years ago. 

In “State of the Air” 2022, only one city among the 25 worst for short-term particle pollution is not in the western U.S. Pittsburgh again showed improvement and moved to 22nd worst in this year’s report, yet it remained the worst metro area in the country east of Utah for this pollutant measure.

U.S. map with light blue lines along west coast

All but one of the 25 worst cities for short-term particle pollution are in the western U.S.

Of the remaining 24 worst cities, 11 were in California, nine in the Pacific Northwest and four in the Southwest. This continues a shifting geographic trend driven in large part by the increasing number and size of wildfires resulting from climate change-induced heat and drought.

Extreme Pollution Levels on the Rise

In the last several years, Americans have been seeing media coverage of catastrophic wildfires in the western U.S. Images of iconic cities like San Francisco bathed in an eerie orange glow that darkened the sky in the middle of the day were reminiscent of those deadly air pollution events of the mid-twentieth century that prompted the passage of the Clean Air Act.

Wildfires in the western U.S. are not only increasing the number of days and places with unhealthy levels of particle pollution. They are also increasing the severity of pollution, resulting in a sharp rise in the number of days designated as either purple or maroon. These are the levels on the Air Quality Index that carry the strongest health warnings. On purple very unhealthy days, “The risk of health effects is increased for everyone.” On maroon hazardous days, a health warning of emergency conditions is issued, saying, “Everyone is more likely to be affected”.

“State of the Air” 2022 includes 26 counties across six western states where levels spiked to “hazardous,” the highest “maroon” level in the Air Quality Index, on a total of 74 days, far outstripping the ten such days in last year’s report. These counties are home to 4.5 million people. During the three years covered by the report, 116 “very unhealthy” or “purple” air quality days were recorded in 47 counties across eight states, home to some 34 million people. This was almost twice the number of such days recorded in either of the previous two reports, and more than ten times as many as were reported in “State of the Air” 2018.

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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Page last updated: April 13, 2022