Endless cycle of wildfires threatening gains on air pollution in CA, Stanford experts say

ByJulian Glover and Tim Didion KGO logo

Thursday, September 21, 2023

Wildfires threatening gains on air pollution in CA: Stanford experts

Researchers at Stanford's Doerr School of Sustainability say an ongoing cycle of wildfires is literally tipping the balance on air pollution in California.

PALO ALTO, Calif. (KGO) -- The smoke that's blanketing our Bay Area skies will eventually clear. But researchers at Stanford's Doerr School of Sustainability say an ongoing cycle of wildfires is literally tipping the balance on air pollution in California.

"What we find in the study is, particularly in California, wildfire smoke is undoing a bunch of progress towards air quality improvements. And California specifically, we estimate that the trends in air quality have reversed because of wildfire smoke," says co-author Marissa Childs, Ph.D.

And that reversal has been dramatic. They say particulate pollution in California and Nevada had actually fallen by nearly a third from 2000 to 2015. But since then, the same pollution index has risen 14%, driven in part by the wildfires that have swept through the Sierra and elsewhere.

MORE: Here's when Bay Area might see air quality improvement as wildfire risk increases

"So it used to be the case that wildfires would just -- wildfire smoke would blow through for a day or two and then we'd get our nice clean California Bay Area Air again. What we're seeing now, is that for days at a time or weeks at a time, or even months at a time, in recent years, we get wildfire smoke that really sticks around. And when it does that, and it sticks around in high levels, it can have a substantial effect on the overall annual air pollution in a given area," said lead author Marshall Burke Ph.D.

Enough to threaten air quality gains made by cutting pollution from cars and factories, with the help of the Clean Air Act, passed more than half a century ago. And while the landmark law regulates most sources of pollution, researchers are concerned that it does not include wildfires.

"I think this study and others before, I'd have made the point that that's not going to be sufficient. If we want to think about clean air for, you know, the population, wildfires are starting to have a really big influence on total air quality. And if we omit them from regulation, we're just not going to be able to protect people's health in the same way," Childs said.

And whether that's controlled burns or other fire management techniques, researchers believe the wildfire trend could trigger a serious rethinking about managing a growing threat.