Air pollution in New York and across the eastern United States, driven by an outbreak of wildfires across Quebec and Nova Scotia, has reached the worst level since 2005, when modern records began, according to a Stanford economist.
“I pulled the data for the past 18 years, and it’s almost off the charts,” Marshall Burke, an economist who specializes in climate change and an associate professor at the Stanford Doerr School of Sustainability, told me.
Surveying the dangerous haze that stretched across the country on Tuesday, he said it could conceivably be one of the worst days for air pollution even before the 2000s. Rarely have so many people been exposed to so much particulate matter, or PM2.5, a toxic haze of microscopic soot and ash that is linked to early death and can penetrate the blood-brain barrier. (It’s called PM2.5 because it measures 2.5 or fewer microns across.)
New York City’s air pollution index — which spiked to more than 200 on Tuesday, a level considered “very unhealthy” for all groups — was comparable to a “pretty bad event that we’d get on the West Coast,” he said. But it is unheard of for such toxic air to afflict such a densely populated part of the country. In the late evening, New York briefly had the worst air quality of any city on Earth, beating Delhi, India, and Doha, Qatar.
Burke has published widely on climate change’s costs, studying how rising temperatures might affect crop yields, suicide, and the outbreak of wars. But on Tuesday evening, he said that the economic impacts of wildfires — and their voluminous smoke output — might be one of the biggest unknown dangers of climate. Our conversation also touched on the heinous health effects of wildfire smoke, especially for women and children. It has been edited and condensed for clarity and readability.
From a PM2.5 standpoint, is this on par with the San Francisco 2020 event? Are East Coasters experiencing what West Coasters now experience every summer?
That’s a great question. We’ll have to see how long it lasts. A lot of the West in 2020 — really, in California — basically had what you guys are having but for a month. Sometimes it wasn’t quite as acute, but often we got days and days of stuff about as bad as what you guys are having. So I think it’s a hopefully very short-run vision of what some of the rest of the country has dealt with.
But the important part here is the number of people getting exposed. You get days in the West where, like, Missoula, Montana, is hit pretty hard. Or in the 2020 event, we had parts of California get hit pretty hard for weeks. But today we’re talking about the most populated parts of the country just getting hammered. So in that sense, it’s pretty anomalous — it’s different from the Western events where you have unpopulated areas getting dosed.
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Thinking more broadly, when you talk about this much wildfire smoke over this many people, what are the health consequences we can expect?
People have been studying the health impacts of wildfire smoke for a while — and it’s interesting. You would think we would have a pretty precise answer, but we still don't have a great one.
That’s mainly because these levels of air pollution are so high they induce some weird behaviors. So people actually notice the smoke, and they respond in a way that shapes health outcomes.
So you see some things you would expect. Respiratory hospitalizations or emergency department visits go way up — that’s been shown by a lot of groups. And that’s caused by asthma, that’s COPD, that’s bad stuff.
But other stuff changes — car wrecks go down, there are fewer fractures, people don’t break their legs playing soccer. Basically, what economists would call avoidance behavior pushes back in the other direction pretty substantially. So on really bad days, it’s this funny mix of worsened respiratory outcomes and declines in other, “non-smoke-related” visits.
That’s really interesting.
That said, there are demonstrable negative health impacts for vulnerable groups. And all the research suggests we should draw the circle wider and wider in terms of what we call “vulnerable groups.”
Any pregnant moms — if my wife or anyone I knew was pregnant right now — I would be texting them to stay inside and sit by an air filter. We see very large impacts on preterm birth for moms who are exposed while their kids were in utero. Like I said, my daughter has asthma, so on days like this, she gets to blow it out on the iPad sitting next to the air filter.
So part of the story is not nuanced. If you’re a vulnerable group, it’s a good time to protect yourself.
There is also an ongoing debate about whether wildfire-sourced PM2.5 is better, worse, or the same as PM2.5 from fossil fuel combustion. Some early evidence suggests it’s maybe a lot worse for respiratory function — I’m not fully convinced myself but it could be true. We see a lot of nasty stuff in wildfire smoke. We see heavy metals that get aerosolized, all this stuff that’s in your sink when houses burn, that gets aerosolized. But I think broadly, the PM2.5 literature is a good guide for what’s happening.
As a scholar of air-pollution policy, how do you even begin to think about dealing with the problem of wildfire smoke?
For me, it's so important to mention the backdrop, which is just this remarkable policy success in improving air quality. And it was driven by bipartisan public policy that was really good and really worked. You can look at papers on this: You just don’t get bad air-pollution days anymore on the East Coast. They’re gone. They just don’t exist.
You’re talking about the Clean Air Act here?
Yeah, the Clean Air Act, exactly. And that is being so quickly undone in the West by wildfires. Less so in the East — we saw fingerprints of it last year — but this is going to be a big event, and it’s going to change our estimates a lot. So this really nice progress that we had made is just being rapidly eroded now, and I thought that was just a West Coast story, but maybe now it’s happening in the East too.
Now, I don’t think this is going to happen every year for you guys on the East Coast. I don’t think the data suggests that yet. But it’s not going to happen never — it’s going to be more common.
It’s funny, when you look at the big climate reports, like, you’ll sometimes see a line like increased wildfire activity in the Southeast or increased wildfire in the boreal forest. And in the past when I've read that, I've been like, well, what’s that going to be like? Wildfires already happen in the East, and they’re never as big a deal as the ones in the West. It was hard to look at those sentences and ever imagine the East Coast facing an event like California now regularly faces. But now…
They were never going to originate in the East Coast, almost surely. Wildfire smoke might affect the East Coast, but it was going to come from somewhere else.
And last year, we did have some wildfire smoke — the AQI maybe got above 100 — but it was Western smoke floating over, it was not smoke from an Eastern fire.
Exactly. And I think honestly that’s what you should still expect. Although the forecast for the next couple of days suggests there’s pretty high fire risk across a bunch of the Northeast, so it’s not out of the question. We could see some starts in the Northeast that could contribute to the smoke, but certainly that's not the case right now.
I think that the modal case is going to be one that looks a lot more like what we’re seeing today, where you get big Canadian fires blowing in. But that just makes the air-pollution problem harder, because now we have a transboundary problem.
So what do we do? Do we sue the Canadians? Do we buy them off?
Your point about the Clean Air Act is interesting, because the Clean Air Act, what it ultimately addressed was this point-source pollution. I mean, factories, power plants, and cars, basically. And what we did was shut down or put scrubbers on smokestacks and put catalytic converters on the cars. And it worked. But it’s not clear what the policy remedy is for large-scale air-pollution events is for wildfires — beyond, you know, decarbonizing.
The way I think about it is that the Clean Air Act was built on one main fact, which is that local pollution concentrations depend on local emissions. So if you regulate local emissions, you improve local air quality. And that worked really well for a while.
But that logic no longer holds. Look at the Canadian fires — number one, it's not a point source, and number two, it doesn't stay locally. We’re not equipped to deal with this, and we have dug ourselves a massive hole in terms of a century of putting out fires that have just made this problem a monster.
What do you think about this, as a West Coaster looking east?
My pitch for a while on the West Coast has been that wildfire smoke is going to be one of the main — if not the main way — we encounter climate change viscerally. I'm sure it’s going to get hot, but these episodic events that sit with us and really disrupt our activity, this is going to be one of the most widespread ways we encounter it.
But I would not have told that story for you guys on the East Coast. And this is still one very historic event, so I’m not ready to tell that story, but I’m going to draw the boundary a little wider next time I give a talk on this.
Wildfires are this clear, almost first-order effect of climate change, especially in the West. And not to bring your profession into this, but when we think about the economics of climate change, and wildfire smoke shutting down travel in an entire metro area for three days and discouraging outdoor activity or exercise — that’s not necessarily something that it seems like there's any historical comparison for. It doesn’t seem like something we can model very well.
That’s exactly right. None of the existing monetized economic costs of climate change — like when we come up with the social cost of carbon or any of that stuff — wildfires are not in there at all. So this is fully un-costed in all the sort of headline climate-change cost numbers that we have.
Certainly, folks are making the links, and if you read the National Climate Assessment then wildfires are in there, but in terms of monetizing the cost, you're 100% right. We have not done that. Honestly, this is a big push in my groups to try to do it back to that, try to monetize these, and I think they're going to be really big.
When we've done back of the envelope estimates, they suggest the costs are at least as large as heat, potentially. Especially if we get more events like the one today.
Wow.
The effects go beyond that too. There are all these papers now that show cognitive decline when exposed to air pollution and wildfire smoke. We can look at test-score data and in smokier years, kids do worse on tests. The effects are individually small, but you add them up across schools and across counties and they get pretty big.
Are they lasting? Do the cognitive effects go away over time?
The question is, is there catchup, right? In terms of learning losses, we would have to follow people for longer than we’re able to right now. But they certainly last within the year. So if I’m exposed in September, and I take a test in April, I can still see the effects of the wildfire.
Wow.
We see that in our data. Now, we can’t nail the cognitive channel [as being at fault here] — like, it could be because you didn't go to school. But mostly schools don't close during smoke events, and so it’s consistent with the cognitive channel. But maybe the next year you learn what you missed and, you know, we can’t rule that out.
I think the more proven long-term outcomes is the relationship between in utero exposure and later-in-life outcomes. That’s been shown for other air pollutants, and I don’t think there’s any reason to think it’s not true for wildfire as well. In-utero exposure has this lifelong, negative imprint, including on earnings and cognitive function.
Offshore oil rigs in California. Mario Tama/Getty Images