Short Term Particle Pollution

More than 13 percent of people in the United States live in an area with too many days with unhealthful levels of particle pollution.

What Is Short-Term 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.

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.

Close to 41.7 million Americans live in 55 counties that experienced too many days with unhealthy spikes in particle pollution, a decrease from the last report. This number may undercount the total because it does not include data from Illinois, most of Tennessee and much of Georgia.1

The problem grew worse in many places in 2011-2013 Episodes of high levels of particles increased compared to the 2010-2012 period covered by last year's report. Western states were especially hard hit, with drought and wildfires contributing to the existing problem. Many cities suffered more days as short-term particle pollution worsened, especially in the West. Five cities had their worst records since the State of the Air reports began.

Six cities set a record for their highest weighted average number of unhealthy particle pollution days ever, while 14 other cities had additional high particle days on average in 2011-2013 compared to 2010-2012.2

  • Cities that recorded their largest number of days with high particle pollution on average were Visalia (CA), San Francisco, Fairbanks (AK), Phoenix, Yakima (WA) and Reno (NV). San Francisco is included because of the addition last year of San Joaquin County to the San Jose - San Francisco - Oakland Consolidated Statistical Area.
  • The other cities with higher weighted average number of days in this report include Fresno-Madera (CA), which retained its ranking as the most polluted for short-term particle pollution in the nation; Modesto-Merced (CA); Los Angeles; Salt Lake City; Logan (UT- ID); Sacramento (CA); Seattle; Harrisburg-York (PA), Eugene (OR); Lancaster (PA); Philadelphia; Boise City (ID); and Medford-Grants Pass (OR).

Five cities reduced their average number of days with unhealthy particle levels.

  • One city - Pittsburgh - had its fewest unhealthy days on average ever in our report history.
  • The other four cities that reduced their pollution were: Missoula (MT); New York City; El Paso-Las Cruces (TX-NM); and Indianapolis.

Increased heat and continuing drought in the West likely contributed to the worsening problem, although they are not the only sources. High particle days frequently result from use of wood-burning stoves for heat, dust storms, wildfires and weather patterns that trap in emissions from power plants, trucks, buses, trains, ships and industrial sources.

Data are missing on one city that was listed among the most polluted in the 2014 report. Data are unavailable for Chicago so it is impossible to know whether the air quality there improved or worsened. Problems with data processing in Illinois, most of Tennessee and part of Georgia prevented people in those states from having information on their particle pollution levels for this period.

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

  1. These trends are based on prior available data. Not all cities had counties with complete annual averages posted for all prior years.
  2. Note that the full metropolitan areas often include multiple counties, incorporated cities and counties in adjacent states, as the Office of Management and Budget defines them. Not all counties in any metro area will have monitors.
Did You Know?

Did You Know?Cleaner power plants and diesel engines helped cut year-round particle pollution in many areas in State of The Air 2015.

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