Download the 2020 State of the Air full report


What Are "Short-Term Levels" of Particle Pollution?

Particle pollution can be harmful even if it is inhaled over just a few hours or days, even if the year-round averages are low. "Short-term levels" refers to just such spikes. These represent levels averaged over a 24-hour period. Those days or weeks of high levels can be dangerous, even deadly.

Bakersfield (CA) remains the city most polluted by spikes in particle pollution. Bakersfield has held this position for all but two years since the 2010 report covering data from 2006-2008. Twenty of the 26 most polluted cities had more days on average in the 2019 report. Many of these are due to wildfires.

Eight cities had their highest-ever weighted average number of days with spikes in particle levels: Fairbanks, AK; Missoula, MT; Yakima, WA; Spokane-Spokane Valley-Coeur d'Alene, WA-ID; Santa Maria-Santa Barbara, CA; Salinas, CA; Bend-Prineville, OR; and Bismarck, ND.

Showing the impact of wildfires, prior to this year's report, Santa Maria—Santa Barbara, CA had been on the list of cleanest cities for short-term PM for the past six years.

Twelve others also suffered from more days when particle pollution spiked into unhealthy levels. San Jose-San Francisco, Los Angeles, Seattle and Pittsburgh, Logan, UT; Phoenix; Sacramento; Medford-Grants Pass, OR; Eugene, OR; Reno, NV; Portland, OR; and Pocatello, ID.

Wildfire smoke shifted Santa Maria—Santa Barbara, CA off the list of cleanest cities for short-term particle pollution for the past six years to rank as the 17th most polluted city.

San Jose-San Francisco CSA added two counties from the former Modesto-Merced MSA, which had ranked fifth most polluted in the 2018 report. Their addition increased the weighted average, but, even without those counties, the metro area had more days.

Six of the 26 most-polluted cities improved and had fewer unhealthy air days on average than in the 2018 report. Despite being among the 10 most-polluted, Salt Lake City dropped to its fewest days ever reported on average. Five other cities had fewer unhealthy days on average: Bakersfield, CA; Fresno-Madera-Hanford, CA; Anchorage; Visalia, CA; and El Centro, CA.

NASA's Suomi NPP satellite collected this natural-color image using the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument on September 04, 2017.

NASA's Suomi NPP satellite collected this natural-color image using the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument on September 04, 2017. Actively burning areas are outlined in red. NASA image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC. Caption by Lynn Jenner

In California, Washington and Oregon, extended wildfires increased the days when PM levels spiked. The Los Angeles metro area had two days when levels spiked to "hazardous," the highest "maroon" level in the Air Quality Index. Medford-Grants Pass, OR, Eugene, OR and Calaveras County, CA each had one maroon day.

Wildfires are not the only source of high particle pollution days. Other sources including wood stove use (especially in Fairbanks), older diesel vehicles and equipment, and industrial sources (as in Pittsburgh) contribute to a lot of particle pollution. Changes in weather patterns can create atmospheric inversions that trap particles in place, leading to days with spikes. Pittsburgh is the only city in the 25 most polluted that is east of the Mississippi River.

Did You Know?

  1. Nearly 5 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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