Short Term Particle Pollution

Nearly one in six (16.1%) of people in the United States live in an area with unhealthful short-term levels of particle pollution.

  • Nearly 50 million Americans live in 66 counties that experienced too many days with unhealthy spikes in particle pollution, a decrease from the last report.
  • Short-term spikes in particle pollution can last from hours to several days and can increase the risk of heart attacks, strokes and emergency-room visits for asthma and cardiovascular disease, and most importantly, can increase the risk of early death.

Unlike with year-round particle pollution levels, fewer cities with the worst short-term levels improved in 2008-2010. Only 13 cities had fewer unhealthy days or lower daily levels, while 13 of the cities on the list did worse than in 2007-2009.1, 2

Among the 26 cities with the worst short-term levels of particle pollution, thirteen cities improved in 2008-2010: that is, they had fewer unhealthy days or lower daily levels. In addition, nine cities that were on this list in previous reports moved off the list entirely, including one—Birmingham, AL—that had been on since the list began. Twelve of the cities on the list had more high particle days in 2008-2010 than in the previous report. Although “short-term” particle pollution looks at the same type of pollution that the year-round levels do, this measure focuses on the spikes in particle levels that can last from hours to days. Those days or weeks of high levels can be dangerous, even deadly.

In 2008-2010, these thirteen cities improved, cutting their average number of days with high particle levels: Bakersfield, CA(still ranked most polluted); Fresno, CA; Pittsburgh, PA; Salt Lake City, UT; Provo, UT; Visalia, CA; Eugene-Springfield, OR; Stockton, CA; Chicago, IL; San Diego, CA; Sacramento, CA; Davenport, IA; Philadelphia, PA. Nine previously ranked cities had improved enough to drop off the most polluted list this year: Birmingham, AL; Louisville, KY; Phoenix, AZ; San Jose- San Francisco-Oakland, CA; Wheeling, WV; Seattle-Tacoma, WA; Macon, GA; Portland, OR; and Madison, WI. Four cities had their lowest average yet, despite still being among the 25 most polluted: Philadelphia, PA; Pittsburgh, PA; Visalia, CA; and San Diego, CA.

Five cities were never ranked on this list before but moving to this list because so many other cities had fewer unhealthy air days: Las Cruces, NM; Harrisburg, PA; Washington, DC-Baltimore, MD; South Bend, IN; and Yakima, WA. The remaining cities on the list had more days or higher daily levels than in the last report: Hanford, CA; Los Angeles, CA; Modesto, CA; Logan, UT; Milwaukee, WI; Fairbanks, AK; Merced, CA; and Green Bay, WI.

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. To learn more, go to Health Risks.

» 25 Cities Most Polluted by Short-term Particle Pollution
» Cleanest Cities for Short-term Particle Pollution

  1. The usual list of the 25 cities with the most short-term particle pollution actually includes 26 cities because of ties in the rankings.
  2. Full names for all these metropolitan areas can be found in the tables showing the most polluted and cleanest cities. The full metropolitan areas often include multiple counties, incorporated cities and counties in adjacent states.

FACT: Minorities and lower income groups are often disproportionately affected by air pollution which put them at higher risk for illnesses.

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