In the years 2017, 2018 and 2019, close to 54.4 million people lived in the 88 counties that experienced unhealthy spikes in particulate matter air pollution. This represents a million more people than in last year’s “State of the Air”, and higher numbers than in any of the last five reports.
Many cities reached their highest number of days with unhealthy levels of particle pollution ever reported. Of the 25 most-polluted cities, 5 of them, including worst-ranked Fairbanks, posted their highest-ever average number of days with spikes in particle levels – for the second year in a row.
The list of the 25 worst cities for short-term particle pollution is very similar to last year’s report, with minor shifts in rank-order. The exceptions are Salt Lake City, which improved dramatically from 7th worst to 17th worst; Salinas, California, which improved enough to be removed from the list; and Lancaster, Pennsylvania which returned to the list for the first time since the 2018 report (see Figure 2).
Thirteen of the 25 most-polluted cities improved and had fewer unhealthy air days than in the 2020 report. However, as a general rule, improvements were modest, and all of these areas remained seriously polluted. For example, Bakersfield, though the only city among the worst 25 that improved to its best ever, nevertheless ranked third worst in the nation.
In “State of the Air” 2021, all but two of the 25 worst cities for short-term particle pollution are in the western U.S., with 10 in California, 8 in the Pacific Northwest and 5 in the Southwest. Only two cities are in the eastern U.S. This continues a shifting geographic trend being driven in large part by the increasing number and size of wildfires resulting from climate change-induced heat and drought.
Page last updated: April 15, 2021