Play Live Radio
Next Up:
0:00
0:00
Available On Air Stations
podcast_1400-MiddayEdition.jpg
KPBS Midday Edition Segments

’We Know It Is In The Air’ — Local Scientist Reacts To Changing CDC Guidance

 September 22, 2020 at 10:53 AM PDT

Speaker 1: 00:00 In order to defeat a virus, you need to understand how it spreads, but the CDC, the U S centers for disease control has changed its COVID-19 guidance several times on what is safe and what is not leaving Americans confused and uncertain about what to believe the latest change came about yesterday. When the CDC removed recently added language about how the virus spreads through the air and aerosol particles, one of many scientists reacting to the administration's confusing message is Kim Prater, who is distinguished chair in atmospheric chemistry at UCS D Kim. Thanks for joining us. Speaker 2: 00:36 Thank you for having me. Speaker 1: 00:38 So now describe to us what the CDC website on COVID-19 Tina, Jean, how it changed last Friday. Speaker 2: 00:46 Yeah, so I got on Friday CDC, um, sort of quietly put up some changes, some very important changes, um, and how they believe this particular virus is being spread. So they added the fact that it is, can be, um, and is likely largely transmitted through the air in the form of aerosols and then on, um, you know, so then there was a very positive reaction to the community because that support that is supported by the science and this was, we were very excited cause this provides super helpful guidance to those opening schools and businesses. And then Monday mornings where I'm just as quietly, they took it off and went back to the old guidance, which quite frankly doesn't help as much, um, in providing guidance on how to, and this virus. Speaker 1: 01:34 Okay. Can you clarify how aerosols differ from droplets? Speaker 2: 01:39 Sure. So aerosols are really tiny, um, and they float, they're invisible. You don't see them and they tend, they're so small that they, when they're released, they're produced in your speech. And when you talk, when you breathe, they just come out and lots of aerosols come out. Um, and largely for this virus, they come from people who don't know they're sick. And so these will just get in the air and float for hours. And anyone particularly indoors can inhale and be potentially infected, um, by these aerosols. Whereas droplets are just bigger, much bigger. And when they come out and they're largely producing coughs and sneezes, which isn't as much of an issue for this virus, but nevertheless there's droplets. Those are really big. And those have like a, almost like a Cannonball trajectory, right. They come out and they fall to the ground within six feet. And so, um, you know, we don't worry as much about inhaling those as we do the aerosols. Speaker 1: 02:38 So now in view of the CDCs actions, tell us what is the scientific evidence that aerosols are a significant mode of transmission? Speaker 2: 02:48 Well, they're the, you know, the evidence that's out there, the scientific evidence, which is growing almost daily shit, all of, all of the studies have detected it only in the, um, they're really just there isn't that many droplets as I mentioned. And so it's in the air, the scientists don't question that we just had a national Academy workshop by distinguished scientists from around the world. We all agree it is in the air. We know it is in the air. And so that is what we need to be out there clearly, um, for public guidance. Speaker 1: 03:21 But do the scientists agree that aerosols are more likely to be the cause of spread than droplets? Speaker 2: 03:26 Yes. I mean, basically what comes down to what the, one of the big debates quite honestly is between different communities that Devon the defining, let's say this sort of arbitrary size of what is an aerosol, what is a droplet? So in this national Academy, a workshop that we did, we finally defined it very clearly a hundred microns. So that's, you know, anything smaller than that will float in the air. You can inhale it and get infected anything bigger than that, we'll settle within six feet. And so, you know, basically that you have to sort of touch a surface, right? You're back to contact. Um, whereas the smaller stuff floats around. So sometimes people will call aerosols droplets and some people call droplets aerosols. They're all things, you know, in the, at the end of the day, what matters is that it's in the air and you can inhale it and get sick. Speaker 1: 04:20 There does seem to be a difference in the behavior of the aerosols and the droplets. And I wondered if you could answer how the CDCs change affects the idea of, of whether it's a good idea to wear a mask. Speaker 2: 04:31 So masks work for both droplets and aerosol. So they would argue, and I just heard dr. Fowchee talk this morning. He basically said, nothing changes. You still need masks. You still need to be, you know, at least six feet apart, the further, the better you still need, good hygiene. Um, you know, sort of all the things work for droplets or aerosols ventilation actually works better for aerosols. There's a little hint that it's aerosols. You want to be in more ventilated places. Um, you know, things that have better filtration, you can filter them out. Um, so there's, you know, there's extra layers. What I see I'm helping schools reopen right now and giving them advice. And one of the biggest things that we're protecting against is exposure indoors. So we're suggesting that everybody wears masks indoors all the time. There is no safe social distance, right? Speaker 2: 05:23 So that's one big, one better ventilation, open the windows, open the doors. Those will have a tremendous effect on reducing the concentration of aerosols. They have virtually no effect on the droplets. The droplets just spew out, hit the ground within seconds. So we don't see that big of an effect, but for the aerosols, which we really believe in, it's really been shown so far. In many cases, acquire restaurants, bars, where people are talking and not wearing masks. That's where we see these big super spreader and cluster events. And those are aerosols without question. Okay. The CDC says it changed the language over the weekend because it had not been properly vetted. What's your assessment of why it changed the language. Speaker 2: 06:09 I don't know until I see how they change, how you know, what the changes are. Uh, I will tell you that in reading, it, it, it looked quite honestly a bit like a rough draft. So maybe they're just my hope, our hope as scientists is that they're just polishing it more, um, to make it a little clearer for the public, but we will see, I, you know, I won't be able to know for sure until we see the new version. Okay. Now you were quoted in the LA times as suggesting that it was dangerous to go surfing and swimming because of COVID, um, and even dangerous waiting to be at the beach. But I don't know if we've seen any data to suggest that surface are getting sick from COVID. Do you still hold that position? Uh, let's just say that I was misquoted very comment taken out of context, unfortunately, which, um, basically I'll clarify here. Speaker 2: 07:01 Um, my concern when I saw people at the beach was that people were super crowded at the beach at that time. You know, everybody was too close to each other. They were not social distancing. And that was my concern. I have a separate project in San Diego, actually in Imperial beach that looks at sewage going into the ocean, right? And so we are in the process actively looking to see which viruses and bacteria make their way into the ocean and into the air. It's a complete, like a research project, you know, still in process. Um, we are looking to see, as I say, which viruses make it their way in, but the beach closers closures have largely focused on what's in the water. And our question is which, which, you know, which if any of these viruses and bacteria could get into the air and people could inhale. Speaker 2: 07:50 So that's a totally separate issue. You know, the beach being outdoors is one of the safest places you can be. So what should the average citizen do to respond to this ever changing news? I would hope that the public will continue to trust the scientists that are not influenced by any politics masks are really, really important. You know, the guidance is being given to avoid places right now where the community spread is high indoor locations are not as safe. I can tell you that as scientists, we haven't flipped our message. We've been speaking with Kim Prager. Who's distinguished chair of an atmospheric chemistry at UCS D Kim. Thanks so much for joining us. Thank you for having me.

MiddayEd_generic-new_kuWKfof.jpg
On Monday, the Centers for Disease Control removed language about the spread of the coronavirus through aerosol particles from its website, information they had just posted Friday. A renowned UC San Diego atmospheric chemist explains what science believes about aerosols and the coronavirus on KPBS Midday Edition.
KPBS Midday Edition Segments