No one knows what sparked the violent fires ablaze in the hills of California wine country. In the last five days, the flames have torched more than 160,000 acres across Napa and Sonoma counties, reducing parts of Santa Rosa to piles of cinder and ash and leaving more than 20 dead and hundreds missing. And far from the white-hot embers of destruction, residents from San Francisco to Sacramento to Fresno have been waking up this week to choking fumes, commuting to work under skies tinged orange with dust and soot.
Now, in just a single fire season, ash has rained down on Portland, Seattle, San Francisco, and Los Angles. That might seem like an anomaly—but it’s more a portent of the country’s new, char-coated normal. As climate-change fuels increasingly large and frequent wildfires that hit closer and closer to densely populated urban centers, the smoke they produce is becoming a public health crisis.
“Over the past two days we’ve experienced unprecedented levels of air…