Short-Term Particle Pollution Trends

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In the years 2020, 2021 and 2022, there were 65 million people living in the 112 counties in 19 states that earned an F grade for unhealthy spikes in particulate matter air pollution. This represents an increase of 1.3 million more people than in last year’s report, the sixth straight year of increasing health threat of this deadly pollutant.

cirlce with 65 MM

More than 65 million people in America live in counties with F grades for spikes in daily particle pollution

Even compared with the past several 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, especially throughout much of the western United States. This trend in recent years is a reversal after roughly a decade of improvements resulting from the requirements of the Clean Air Act. 

Snapshot from the 2004 "State of the Air" report

The “State of the Air” report added grades and ranks for fine particle pollution in 2004, with data from 2001, 2002 and 2003. It was the first time three years of data was available from a network of monitors put in place following EPA's adoption in 1997 of a new health standard to address particle pollution. At that time, 106 counties in 30 states earned an F grade for short-term particle pollution, affecting the health of 81 million people. The air quality standard was weaker than it is now, meaning that in fact many more people were breathing unhealthy air. If the current standard had been in effect, 189 counties in 36 states would have gotten failing marks.

Wildfires in the western United States and Canada remain the major contributing factor to the increasing number of days and places with unhealthy levels of particle pollution in recent years. Wildfires are also continuing to increase the severity of pollution, resulting in the highest ever number of days designated as either purple or maroon (135 and 79 days, respectively). 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, the highest category, a health warning of emergency conditions is issued, saying, “Everyone is more likely to be affected.”

In the years 2020, 2021 and 2022, the health of 32.3 million people across 58 counties in ten states was put at risk on “purple” or “maroon” days for fine particle pollution. This is slightly worse than the findings in last year’s “State of the Air” and a worrisome sign of a trend that is continuing as climate change worsens.

In this year’s report, 33 metropolitan areas equaled or exceeded their previous worst-ever weighted average number of days with unhealthy levels of fine particle pollution. Among those cities ranked the worst 25, the average number of days per year that residents were exposed to high levels of fine particle pollution increased by more than two days, to a weighted average of 20.8 days. Seven of the 25 most polluted cities for this measure posted their highest-ever number of unhealthy days: Fairbanks, Alaska; Visalia, California; Boise City, Idaho; Eugene, Oregon; Las Vegas and Reno, Nevada and Spokane, Washington. Only one city, Logan, Utah, recorded its fewest-ever number of unhealthy days, though it still earned an ”F” grade.

Twenty-two of last year’s worst 25 cities remained listed among the worst 25 in this year’s report, with most of their relative ranks shifting by no more than two places. Three metro areas saw declines in their air quality that moved them up among the worst 25: Las Vegas, Nevada, for the first time, and well as Portland, Oregon and Seattle, Washington. Medford, Oregon, and Lancaster and Pittsburgh, Pennsylvania improved enough to leave the list. Pittsburgh, in 26th place this year, narrowly avoided the 25 worst list, noteworthy as first time that Steel City has earned that distinction for this measure. 

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

In “State of the Air” 2024, with the departure of Lancaster and Pittsburgh, for the first time in the report’s history, no cities among the 25 worst for short-term particle pollution were in the eastern United States.  The farthest east of any metro area on the list was Fargo-Wahpeton, ND-MN.

The Revised National Standard for Particle Pollution in “State of the Air” 2024

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Did You Know?

  1. Nearly four in ten people in the U.S. live where the air they breathe earned an F in “State of the Air” 2024.
  2. More than 131 million people live in counties that received an F for either ozone or particle pollution in “State of the Air” 2024.
  3. Nearly 44 million people live in counties that got an F for all three air pollution measures in “State of the Air” 2024.
  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 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. Particle pollution exposure from wildfire smoke harms health in ways that range from mild irritation to serious illness and premature death.
  20. Recent updates to the Air Quality Index give the public more accurate information about the health risk from air pollution, and when to take measures to protect themselves on bad air days.
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Page last updated: April 19, 2024