The Pandemic Cut Down Car Traffic. Why Not Air Pollution?


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SOFIA: You’re listening to SHORT WAVE from NPR.

Maddie Sofia here with NPR climate correspondent Lauren Sommer. Hey, Lauren.


SOFIA: And science reporter Rebecca Hersher.

REBECCA HERSHER, BYLINE: Hey, Maddie. Do you remember March?

SOFIA: Yeah, Becky, of course I do. It was last month.

HERSHER: (Laughter) Do you remember what was going on outside in March?

SOFIA: Yeah. I mean, I remember looking at it, the outside. I looked at it.

HERSHER: And what did you see while you were looking at it?

SOFIA: I feel like this is a weird trap – but birds, fresh air, not a lot of traffic.

SOMMER: Bingo.


UNIDENTIFIED REPORTER #1: From a shockingly smog-free New Delhi in India…

SOMMER: Fresh air.


UNIDENTIFIED REPORTER #1: …To unusually clear waters in the canals of Venice, the world is suddenly learning what can happen if humans stop polluting the environment.

SOMMER: In fact, if you listened to the news back in the beginning of the pandemic in the U.S…


UNIDENTIFIED REPORTER #2: With more of us staying inside and off the roads…

SOMMER: …You probably heard it was the freshest, cleanest air ever.


UNIDENTIFIED REPORTER #2: …Cities around the globe are reporting less air pollution.

UNIDENTIFIED REPORTER #2: We’re also seeing wild animals roam in very unexpected places.

SOFIA: Right. Nature is healing, Lauren, as they say – and keep saying.

SOMMER: Yeah. And it is true that traffic plummeted in mid-March. I mean, it dropped around 40%.

SOFIA: So you get rid of car traffic, you get clean air. Is that it because, like, I don’t know if we need a whole episode for that, you two.

HERSHER: Yeah, actually, that’s it. That’s the whole thing. I’m going to go now.

SOMMER: OK. Becky’s kidding. We’re science reporters here. We look for data – right? – to back up what the headlines say about the world. So we called up our colleagues in the investigations unit at NPR. They’re data journalists. And we asked them – was the air really that much cleaner? Can we measure that? And they said, sure, give us a few weeks.

They analyzed half a million air pollution measurements from across the country during the pandemic, and they analyzed the five years before that.

SOFIA: In a few weeks?

SOMMER: They’re very good.

SOFIA: Yeah.

SOMMER: And that way, they compared the average amount of pollution from this spring to the average amount of air pollution from the previous five years. And just to be clear here, I know you already know this. Right? But we’re not talking about carbon dioxide, which is a greenhouse gas that locks in heat, makes the planet warmer – you know, climate change. What we’re talking about are pollutants that make smog and soot, which make the air dirtier.

SOFIA: Right. OK. So you measure those pollutants. What’s the answer? Becky, did the air get a lot cleaner because of the pandemic?

HERSHER: No. It only got a little bit cleaner. Our analysis found that during the pandemic, a pollutant called ozone only dropped by 15% or less in most parts of the country. And in a lot of places, it barely dropped at all.

SOFIA: So today in the show – why the pandemic air isn’t as clean as a lot of the headlines suggested and a lot of people hoped – and how scientists are making the most of this time to study where air pollution comes from and how to tackle it. You’re listening to SHORT WAVE, the daily science podcast from NPR.


SOFIA: So there was definitely one picture that I remember seeing – a freeway in Los Angeles, arguably the traffic capital of the United States, and there were no cars. It was like empty freeway, clear blue sky. And now you came here on this podcast, and you’re taking that all away from me.

SOMMER: Well, actually, the air was cleaner in Los Angeles in March. It was the longest stretch of clean air that had been recorded in decades. And you know, that’s a big deal for LA because their air is not great sometimes. There’s high levels of ozone, which is a pollutant that’s formed by all the stuff that comes out of tailpipes and smokestacks and power plants. What it does is it mixes in the air at ground level, you add some sunlight and you’ve got ozone. And it’s not good stuff. It exacerbates respiratory and cardiovascular illness.

SOFIA: So it makes sense that everybody would be pretty psyched about cleaner air.

SOMMER: Yeah. And it seemed like that made sense – right? – with all the lockdown and people staying at home. I mean, they started asking the air regulators about that, like Philip Fine of the South Coast Air Quality Management District.

PHILIP FINE: There was a lot of pressure on us to come up with the answer that everyone wanted to hear, which is that the COVID-19 measures have cleaned the air in Southern California.

SOMMER: But here’s the thing – it was also really rainy in LA during the same time, and rain helps clear out the air. So as the weather has dried out recently, air quality has gotten worse again. I mean, it went back to the unhealthy category actually.

SOFIA: Yeah. OK. So I guess when you think about there was this 40% reduction in traffic and only a 15 or so decrease in ozone in lots of parts of the country, it’s not nothing. Right?

HERSHER: It’s more of a, like, not much, not a ain’t nothing.

SOMMER: Yeah. It certainly helped some. But you know, believe it or not – sounds kind of strange – cars are not LA’s biggest source of pollution when it comes to the pollutants that make ozone. And that’s actually true in a lot of places in the U.S, which, as Fine told me, that means what’s happening now with reducing car traffic just isn’t really enough.

FINE: I’ve read a lot of newspaper articles over the past couple weeks that have said if only we can have people telecommute one day a week across the entire base, then our air quality problems will be solved. And unfortunately, it’s not that simple.

SOMMER: And that’s because the big source in LA is trucks. And a reason is because there’s just a lot of shipping that comes through the ports of LA and Long Beach. And they handle about 30% of the country’s shipping container traffic. And that gets moved around on trucks after it comes in. So truck traffic, it didn’t decrease as much as the car traffic did, so a lot of that pollution was still being emitted.

SOFIA: OK. So trucks are the problem in LA. Becky, what about other places?

HERSHER: Yeah. So other places have other pollution sources, like Pittsburgh. We looked at Pittsburgh, and ozone only fell by 9% about between mid-March and the end of April. And when I asked atmospheric chemists about this, they were, like, the reason is coal.

SOFIA: Oh, the coal.

HERSHER: Coal that’s burned to make electricity, primarily, but also coal that’s used to make steel – right? The history of Pittsburgh is all about steel.

EMILY ELLIOTT: We still have some very active industrial sources near the city.

HERSHER: And this geochemist at the University of Pittsburgh, Emily Elliott, says coal is really dirty.

ELLIOTT: We’re in closer proximity to the places that are generating power, the coal-fired power plants in the Ohio River Valley, that contribute quite a bit to pollution.

SOFIA: OK. So Pittsburgh has coal. LA has trucks. Anything else I should know about?

HERSHER: Yeah, Houston has this thing with factories. Oh, right.

SOFIA: Rebecca Hersher, we’ve talked about that on the show before.

HERSHER: Indeed, we have. And for those who might not remember, Houston has one of the largest concentrations of petrochemical facilities in the country. So to see how ozone levels have changed there versus other places, that was an interesting question for us. And what we found is that those facilities, they mostly kept operating during the pandemic, actually. In fact, a lot of them, they make the raw materials for masks and gloves, the PPE that hospitals need so desperately right now.

SOFIA: So I’m guessing that ozone levels didn’t decrease a lot in Houston.

HERSHER: Exactly. Ozone decreased less in Houston than it did in LA.

SOFIA: OK. So it sounds like industrial pollution versus pollution from our, like, private cars is a big deal. Are scientists looking into that, Becky – like, how much industry plays into this?

HERSHER: Yeah, they are. And it’s possible that the overall air chemistry has also changed when we remove cars from the picture, which is kind of an intriguing idea. Like, air pollution is kind of a soup of different chemicals and bits, and that soup is different now.

SOMMER: And there’s something even more confusing that happens with that soup, that air chemistry. And this is really strange, so stay with me.

SOFIA: This is really strange, so stay with me is actually SHORT WAVE’s tagline. So go on, Lauren. You’re at home.

SOMMER: Well, we mentioned that stuff coming out of tailpipes and other sources is what makes ozone, right? That stuff is nitrogen oxide. So nitrogen oxides help form ozone. But here’s where it gets weird. Under some conditions – you know, in the short term – nitrogen oxides can break down ozone molecules instead of forming them.

SOFIA: So some pollutants can break down other pollutants is what you’re telling me?

SOMMER: Yes. And I called up one environmental engineer that’s looking into this, Cesunica Ivey at the University of California, Riverside. She says with fewer cars, nitrogen oxides are down. But that means they aren’t doing the job of suppressing ozone, so ozone goes up. And to get over that weird effect, you actually have to cut pollution a lot more.

CESUNICA IVEY: What it shows is that the level at which we decreased was not enough to reduce ozone. And so we’re just going to have to be more aggressive with our sustainable transportation solutions.

SOFIA: OK. So that’s kind of weird. I mean, it means we can be doing the right things for air quality, like driving less, but it’s not going to necessarily have the effect you’d want to see – at least not at this level.

SOMMER: Yes. And then, you know, on top of all of that, the federal government added another wrinkle to this story.


JOHN BARRASSO: We will now hear from our witness, the Honorable Andrew Wheeler, administrator of the Environmental Protection Agency.

HERSHER: So this is congressional testimony from last week. The head of the EPA was testifying, and the big issue that came up was whether the EPA is doing enough to control air pollution during the pandemic.

SOFIA: Why was that such a big issue? Like, isn’t it always the EPA’s job to enforce air pollution regulations?

HERSHER: Yeah. But in late March, when COVID-19 cases were ramping up, the EPA put out this document, and it was addressed to companies that are regulated by the EPA. It basically said, hey, so we understand that the pandemic might make it hard to, for example, check how much pollution is coming out of your smokestacks or repair leaks in chemical storage tanks or file those monthly reports that you usually have to that show that you’re only releasing the pollution you said you were going to. And this is how the EPA administrator described this guidance document in his testimony.


ANDREW WHEELER: We regulate over 1.1 million facilities across the country. And many of those facilities have been shut down, and they do not have the staff on hand to submit their reports to us.

HERSHER: So basically, the EPA was saying to companies, if they can’t comply with pollution regulations because of the pandemic, that’s OK. The EPA probably won’t punish them.

SOFIA: Because these are extraordinary circumstances, this global pandemic.

SOMMER: Exactly. But one thing that makes a lot of people nervous about this policy is, you know, we’re in the middle of a respiratory disease outbreak.

SOFIA: Right, right.

SOMMER: So some people are like – wait a second – now the EPA isn’t doing everything it can to make sure we’re breathing clean air right now? Especially in places with a lot of industry. Like – Delaware Senator Tom Carper, he pushed the EPA administrator on this in a pretty blunt way.


TOM CARPER: Will you stopped writing rules that make things actually worse, not better?

WHEELER: All of our rules make things better, sir.

SOMMER: The EPA doesn’t require companies to tell them if they’re not complying with pollution regulations during the pandemic, so it’s hard to know if there’s extra air pollution and where it’s happening.

SOFIA: Oh, wow. So they don’t even have to say like – hey, we’re not going to be able to comply with this?

HERSHER: Yeah, they’re not required to.

SOFIA: Wow. OK. All right. So I’m going to be honest – you’re bumming me out. Is there anything we can do to fix the pollution soup? And also, I will not forgive you for calling it soup.

SOMMER: Well, science – let’s think of science as the silver lining here.

SOFIA: Always do, OK.

SOMMER: This is, like, a strange, natural experiment that is kind of exciting for scientists. Like, when have we ever removed 40% of cars from the road just to see what happens? Now scientists who study air pollution and where it comes from, they have this whole new set of data that they never would have had before.

SOFIA: Sure. But I also think, like – you know, this like what-a-time-to-do-experiments mentality feels a little weird to me. Like, so many people have lost their jobs. A hundred thousand people, you know, have died in the United States. How can we feel good about anything that comes from that?

HERSHER: Yeah. I totally feel the same way. And I actually asked a lot of the scientists that I talked to that same question. And some of them were like, yeah, it’s sad and hard. But data are data, and we’re excited to have this information that we would never have gotten otherwise. That’s kind of the, like, boiler plate response.


HERSHER: But one scientist – she’s actually a statistician who studies air quality; her name is Jenna Krall – she said something that I hadn’t thought about before, which is that some of the biggest leaps forward in our understanding of air pollution, historically, have come during public health catastrophes.

JENNA KRALL: Like, if we think back to the Donora smog or the London fog events, yeah, maybe it is a silver lining. Or maybe it’s just an opportunity to help to be smarter, I guess, in the future – to learn what we can so that when we think about how changing the pollution mixture in the future might impact health, we’ll be that much smarter.

SOFIA: All right, you two – thank you for all these data, the greatest gift you can give a person.

HERSHER: Thanks, Maddie.

SOMMER: Thanks, Maddie.

SOFIA: This episode was produced by Brent Baughman, edited by Viet Le and fact-checked by Emily Vaughn. And a reminder before we go to make sure and subscribe or follow this podcast to make sure you get new episodes as soon as they’re available, which you want. I’m Maddie Sofia. Thanks for listening to NPR’s SHORT WAVE.