For short term pollution — like in the winter inversion season — the west coast dominates the American Lung Association’s list of the top 25 most polluted cities. In the Mountain West, Missoula, Montana is the worst. It ranks 5th in the country, with the Wasatch Front not too far behind at number 8. Logan, 11, and Pocatello, 25, make the list too.
That means those cities had a high number of days where particle levels were above EPA standards. Between 2015 and 2017, Salt Lake County had about 11 of those days.
But these cities aren’t all that bad when compared globally. The U.S. has some of the cleanest air in the world, according to a recent New York Times air quality analysis. India, for example, has some of the worst air on the planet. Air quality monitors show the entire country in red, with deep pockets of purple for “very unhealthy.”
Officials there shut down schools and declared a public health emergency in November.
“They’re up in the 400s [micrograms per cubic meter of PM2.5 particulate pollution] and we’re worried about going over 35,” said Bo Call, manager of the Utah Division of Air Quality’s monitoring section.
Call said overall emissions in Utah have been going down, especially as cars — by far the biggest source of pollution — have been getting cleaner.
“We have a lot fewer days where we exceed the [EPA] standard,” Call said. “Now we’re just flirting with the [standard limit] line and it’s been trending down steadily.”
That’s not to say Utah is in the clear. Wasatch Front counties are currently labelled nonattainment areas for PM2.5, where burning restrictions are in place. As more and more drivers fill the roads, mobile source pollution will continue even with cleaner cars, though the state places no restrictions on driving.
Air quality issues are also a function of weather, Call said. A major part of the winter inversion comes from particles already in the atmosphere, which combine with each other to create a kind of dirty, particle soup.
And some of that is coming from overseas.
“I think a couple years ago we were tracking the smoke from a fire in Siberia,” Call said. It “was coming over here and impacting us, and we could see it on our monitors.”
So while people need to continue to improve air quality at home, Call says pollution is still a global problem.