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This Is Already One of the Worst Wildfire Pollution Events in U.S. History

Tuesday was a top three day for wildfire pollution, Stanford researchers have found. Wednesday will be worse.

Empire State
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UPDATE JUNE 8 AT 2:15 PM ET: Researchers have found that Wednesday was the worst day for wildfire pollution in American history. Read more.

Today — Wednesday, June 7 — is virtually guaranteed to be among the worst two days for wildfire smoke in American history, and possibly the worst day ever, a new and rapid analysis conducted by Stanford researchers suggests.

The research found that Tuesday was the third-worst day in American history for exposure to wildfire smoke on a population-weighted basis. Given that conditions have been worse on Wednesday than Tuesday, today is all but certain to rank even higher on the list, the researchers said. Not since California’s conflagrations in September 2020 — when the Bay Area clouded with soot and ash, and the sky over San Francisco turned flame-orange — have so many Americans been exposed to so much toxic wildfire smoke.

worst wildfire days chart.Stanford.

“It’s pretty off the charts,” Marshall Burke, an economist and sustainability professor at Stanford who led the research, told me. “It’s pretty historic. We’re talking about the most populated parts of the country just getting hammered.”

The new analysis drives home the importance of Thursday’s mass air-pollution event. From New York City to Norfolk, Virginia, and from Detroit to Ottawa, record-breaking levels of microscopic soot and ash canceled flights, concerts, and sporting events.

The new analysis looked at two variables: how intense the “dose” of wildfire smoke was, and how many people it affected. In essence, it focuses on the average of the American experience: On what days in history is a statistically random American likely to breathe the most wildfire smoke into their lungs? Tuesday and Wednesday of this week, it found, are likely among the top three to hold that distinction.

Although wildfire-driven air pollution reached higher concentrations in some parts of the West in 2020 and 2021, it never affected so many people, living in such a densely populated area. That is what makes this week different, Burke said. “It’s mainly due to the East Coast having so many people. It’s New York, Boston, D.C., Detroit. Out West, our cities are just smaller.”

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  • The finding also clarifies how much wildfire smoke the East Coast has already faced this year. As my colleague Jeva Lange showed, even before this week, East Coasters had faced worse wildfire-driven air pollution so far this year than Americans living out west. (That said, the Western fire season has only barely begun.)

    Burke and his colleagues looked at data from 2006 to 2023. But given that the American population has grown, and wildfires have expanded in size, it is unlikely that wildfire smoke affected more people than before the current period.

    The team cannot formally establish that today, Wednesday, was among the worst days in American history until the day ends and records become available. But the intensity of pollution already observed virtually guarantees that Wednesday is worse than Tuesday, Burke said: “I would be shocked if today doesn’t move up the list.”

    Speaking in a separate conversation on Tuesday, Burke mused that some photos of New York’s ashy sky reminded him of California’s hellish wildfire experience three years earlier. “This looks like you're in California in August 2020 … not in New York City in early June,” he said at the time.

    As his analysis later showed, he was more right than he realized.

    We’ll update this story as more data becomes available for today.

    Robinson Meyer

    Robinson is the founding executive editor of Heatmap. He was previously a staff writer at The Atlantic, where he covered climate change, energy, and technology. Read More

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