RACHEL MARTIN, HOST:
With many Americans staying home, traffic on the roads is down across the country. And many people are looking out the window noticing clearer air. But an NPR investigation finds that air pollution declines are not nearly as large as early indications suggest. One pollutant has barely decreased in some cities compared to levels over the last five years. That means having healthier air will take a lot more than just reducing our driving. NPR science reporters Lauren Sommer and Rebecca Hersher join me now to talk about the investigation. Thanks to you both for being here.
LAUREN SOMMER, BYLINE: Morning.
REBECCA HERSHER, BYLINE: Hi. Thanks.
MARTIN: So, Becky, this is a surprising finding. How'd you go about this? How'd you figure it out?
HERSHER: So this investigation started with a huge analysis by Jingnan Huo and Robert Benincasa on NPR's Investigations team. And what they did is they took half a million air pollution measurements from all across the country that were reported to the EPA over the last six years. They compared the average pollution this year between mid-March and the end of April to average pollution over the last five years. And what they found is that even though traffic has gone down about 40% in a lot of places, one pollutant - ozone - has only gone down by 15% or less in most of the country. And ozone is bad for your health. It exacerbates respiratory and cardiovascular disease. And it forms at ground level when pollution from cars and other things combines with sunlight, basically. So what they've found is - reducing car traffic, it appears it's not enough, even in places with notorious traffic and notorious smog.
MARTIN: Even in places like Los Angeles? I mean, Lauren, it seems like the drop in traffic had to make some kind of difference in the air quality there.
SOMMER: Yeah. Unfortunately, it's not quite that simple. I mean, when people started isolating in LA in mid-March, the air seemed to get cleaner. It was actually the longest stretch of clean air recorded in decades. And that was welcome news because the air in LA is often worse than federal health standards. Here's the thing, though - it was also really rainy. And rain helps clear the air. So more recently, as things have warmed up again, there in LA has hit unhealthy levels again.
MARTIN: So if cars are still largely off the roads, where's this pollution coming from?
SOMMER: Yeah. Well, cars are not LA's biggest source of air pollution. That might sound strange, but air regulators like Phillip Fine have been trying to emphasize that for years. He's with the South Coast Air Quality Management District.
PHILIP FINE: Fed a lot of newspaper articles over the past couple weeks that if only we can have people telecommute one day a week across the entire basin, our air quality problems will be solved. And unfortunately, it's not that simple.
SOMMER: That's because the biggest pollution source is heavy duty trucks, you know, even before the pandemic. And those have stayed on the roads more than cars have. You know, a lot of goods come through the ports of LA and Long Beach. It's 30% of the country's shipping container traffic. And regulators have been trying to get a handle on cutting that pollution. In fact, next month, state regulators are expected to vote on rules that would require electric trucks to be sold in California. And if it passes, it would be the first of its kind policy in the country.
MARTIN: Becky, what about other parts of the country? Has the lockdown affected different cities in different ways?
HERSHER: Yeah, absolutely. It really depends on what types of things are happening in your city. So, for example, I looked closely at Houston, Texas. It's also very car-centric, but it has a huge amount of petrochemical activity. And traffic has decreased there, but the industrial facilities have mostly kept operating during the lockdown. And when we looked, ozone has decreased less in Houston than in LA. Scientists are looking into whether it might be because pollution from refineries and other industrial sites continued. And we also looked at another pollutant - soot, you know, tiny particles of pollution. And in LA, soot pollution went down about 30%. But get this - in Houston, where there's all this industry still working, it only went down by about 13%.
MARTIN: Becky, what about power plants? What role might they be playing in the air pollution right now?
HERSHER: That's something we looked at. We looked at the Ohio River Valley, where most of the country's coal-fired power is concentrated now. And it's very clear that coal is still a major source of pollution in parts of the country like the Ohio River Valley. For example, Pittsburgh - the air is not much cleaner now than when all the cars were on the road. So I talked to a geochemist at the University of Pittsburgh. Her name's Emily Elliott. And she said this moment is actually a good opportunity to see where pollution comes from in different places.
EMILY ELLIOTT: I think that this really brings into clear view in a way that we've never seen before the choices that we have to make as a society.
HERSHER: Like where we get our electricity and how we manufacture things. It's all important if we want to have clean air.
MARTIN: But, Lauren, I guess it's important that we're even able to ask these questions, that there is some opportunity right now.
SOMMER: Yeah. It's actually a really interesting opportunity because this is kind of like a natural experiment for scientists, right? It's a very strange occurrence. And they're doing a lot of studies right now because it could help them understand a lot more just about how air pollution works. And that could really help communities put together more effective plans to reduce pollution, you know, down the road.
MARTIN: Lauren Sommer and Rebecca Hersher from our Science Desk. Thanks to you both.
HERSHER: Thanks so much.
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