Short-term Particle Pollution
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. Learn more about short-term particle pollution.
Bakersfield, CA retains its ranking as the most polluted city for spikes in particle pollution in this report as it had in the 2016 report and in four other reports since 2010. Unfortunately, Bakersfield suffered more unhealthy days on average in this year’s report.
Fifteen of the 25 most-polluted cities had more days with higher episodes of particle pollution, including eight that suffered their most days since the report started and one that maintained its worst report ever.
Cities recording their worst short-term particle episodes in 2013-2015 concentrated in the western states: Visalia-Porterville-Hanford, CA; Fairbanks, AK; San Jose-San Francisco.; Reno, NV; El Centro, CA; Lancaster, PA; Anchorage, AK; and Bend-Redmond-Prineville, OR, marking that city’s first time on this list.
Seven other western cities recorded more unhealthy days than in the previous report. : Bakersfield, CA; Salt Lake City, UT; Logan, UT-ID; Los Angeles; Sacramento, CA; Seattle-Tacoma, WA; and Medford-Grants Pass, OR.
Fortunately, eight cities improved with fewer days of spikes in particle levels in 2013-2015 than in 2012-2014. Six of these are western cities: Fresno-Madera, CA; Modesto-Merced, CA; Missoula, Mont.; Yakima, WA; Eugene, OR; and Phoenix, AZ Two cities in Pennsylvania also improved: Harrisburg-York-Lebanon; and notably, Pittsburgh. Pittsburgh, which had been ranked the most polluted city in the same category in the 2008 report, experienced its fewest unhealthy days ever in 2013-2015.
Eight cities suffered their highest number of spikes in particle pollution since the reporting began.
Philadelphia and South Bend, Ind., recorded the same number of days in this year’s report as in last year’s report. However, as noted above, that kept South Bend stuck at its worst average number of unhealthy particle pollution days.
Regional differences. Locations with many days of spikes shows the burden of concentrated smoke from wildfires, brushfires and wood-burning devices. For example, Reno, NV, suffered wildfires, and Logan, UT-ID; Eugene, OR, and Fairbanks and Anchorage, AK, rely heavily on wood burning devices for heat. Wildfires have increased, in part, from drought and heat enhanced by climate change. Inversions trap particles in place behind mountains and ridgelines. For example, inversions in the San Joaquin Valley in California and in the Wasatch Ridge in Utah contributed to high pollution days in both states.