The deadly wildfires in Northern California have killed at least 23 people, with hundreds still missing, and destroyed more than 3,500 homes and other buildings. The human tragedy of the fire is devastating (here are ways you can help). And as climate change makes wildfires like these more likely, the effects will be dramatic even for people not directly affected: As a result of the fire, the entire area surrounding the fire currently has some of the worst air quality in the world, worse than many of the most polluted cities.
Early on Monday morning, the air quality index in parts of Napa was 442 for PM2.5, particles of tiny pollution that can lodge in the lungs and even enter the bloodstream. On Tuesday, it reached 486. A level above 100 is unhealthy for sensitive people; anything over 150 is unhealthy for everyone. By Wednesday morning, when the index in Beijing was in the thirties, it was well over 300 in Napa.
Even relatively far from the fires, near Richmond, the index reached 246 on Monday–higher than the extreme pollution in New Delhi, where the index went to 225 that day. In parts of San Francisco, the index reached 189. The pollution is particularly dangerous for people with asthma or heart disease; in places where such high levels of pollution are common, like New Delhi, the air quality can cause irreversible lung damage in children, strokes, and early death.
Such high levels of pollution are rare in the United States after the advent of the EPA. But climate change may make them more common. In August, pollution spiked in Portland, Seattle, and other parts of the Pacific Northwest because of wildfires; in early September, wildfires prompted air quality warnings in Colorado. While wildfires occur naturally, and multiple factors–including changes in land use–cause them, heat and drought because of climate change is making them worse. One study suggests that global warming will increase the risk of wildfires in California by six times. The U.S. has done very good work over the last few decades to clean the air of our cities. Climate-change-fueled wildfires could start to undo that work.