A student at Magnolia Elementary cleans up her desk after finishing an art assignment. Magnolia is one of several schools in the Cajon Valley Union School District to offer child care for families during the coronavirus pandemic. / Photo by Adriana Heldiz

In an appearance on our livestream series Voice of San Diego at Home, Scripps Institution of Oceanography scientist Kim Prather, who’s also part of a team working to help reopen schools, said students could be safely back in the classroom in eight weeks if we “buckle down” now.

Prather emphasized wearing masks, getting outdoors and cleaning the air as key to fighting the spread of COVID-19, but also said the current “start and stop is not working.”

“If we keep delaying, if people keep balking, we’re going to sit here for another five or six months,” Prather said. “It won’t go away. But we have the power as a community to decide.”

VOSD editor in chief Scott Lewis spoke with Prather about how the virus spreads, how schools can adapt and what we need to do to reset. Here are some of the best parts of that conversation, edited for clarity and brevity. Watch the full interview here.


Scott Lewis: What is the difference between an aerosol and a droplet? Are they the same thing?

Atmospheric Chemist Kim Prather
Atmospheric chemist Kim Prather / Photo courtesy of UC San Diego

Kim Prather: The question of the day. It depends on whether you’re a doctor, an epidemiologist or an aerosol scientist. I’ll just tell you an aerosol is all suspended droplets in the air. So technically droplets are aerosols. So, when you cough or you sneeze, which is typical for normal sickness, you project big drops that you can see really easily, right? So that’s what the medical world has been very focused on — the big stuff. That’s where the six feet came from because those really big things will fall to the ground. Aerosols don’t behave that way. They will follow the air and they will float in the air, particularly indoors for hours. They’re much tinier. They’re invisible, you can’t see them. And there’s many more of them. For this virus, we think they’re playing a key role. They can’t be ignored anymore. And why we think that is because up to half of the people who are sick don’t know they’re sick, and they’re walking around and they’re not coughing and sneezing. If you cough and sneeze, stay home. Right? But these people think they’re fine. They have no symptoms. They’re spreading it for sometimes two weeks. They’re infectious and they’re breathing out aerosols when they talk. And so that’s why bars and restaurants, indoor locations, churches are so dangerous right now if you don’t have adequate ventilation. This is why masks are so important. If you are sick and you don’t know it, you’re protecting others. They also will protect you. They go in both directions, but they’re largely sort of cutting off the aerosols from getting out into the air and floating around.

SL: I did pick up that there’s a really big debate in your world of science and scientists who are studying this virus about aerosols. Apparently, that debate about whether it’s in the air and can get to somebody else is actually still going on. Right? What is the contention on the other side?

KP: It’s a disagreement over what is a droplet and what is an aerosol based on size. That’s the simple answer. So, the (World Health Organization) says that everything at five microns – which is really small – and above will settle within a meter. That’s a droplet. But the reality is aerosol scientists like me that study particles know that that’s not true. This all sort of started when Anthony Fauci said something about, “Oh, if they’re above five microns, they’ll just fall.” But they don’t. The actual cut should be 50 microns. Those, if it’s 50 microns, when you spew it out, it will fall fine. But anything between say one and 10 microns, which is produced when you speak — they are produced when you cough and you sneeze. But again, this disease doesn’t have as many coughers and sneezers walking around. So it’s from speech, and that’s really important. That’s where you’re just getting this massive amount of these light, airy aerosols that can just float in the air. And so the battle is over what you call them.

SL: So the next step in the logic is that if it is airborne, and it can travel farther, then the key is to address it, as you said, with ventilation and with masks? To protect people from spewing these things out, but then to also, once they’re out, to what? Spread them out?

KP: Outdoors is much safer than indoors because there’s just so much clean air. It’s like dropping a drop of dye into a swimming pool. You know, that kind of dilution happens to aerosols outdoors. Unfortunately, one of things I’ve learned, because I’ve learned a lot about ventilation lately, is that the buildings, when we had the energy crisis, we went to LEAD buildings. That’s sealed. That means we’re not bringing in fresh air. That’s recirculated. So that’s not going to be enough. You have to filter the air using the right filters. MERV 13 and above is what they’re recommending, and you have to do the right number of air exchanges per hour. But for classrooms and older schools, they’re going to be more challenged. There are some really nice solutions for cleaning the air in a classroom, but the bottom line is, you know, filtering the air or at least opening the windows. The cheapest way is to open the windows and open the doors and we can do that in San Diego.

SL: Or go outside, right? Let’s take my school for example. It’s very, very old. But they literally just installed air conditioning. Is air conditioning good or bad?

KP: It’s recirculating things. Here’s the deal: It’s better to bring in clean air and that’s not what air conditioning does. But also keep in mind that we don’t know, like if it gets sucked into an air conditioner and churned through, does it stay alive? Nobody knows that. I’ll just say it again, it’s much better to have clean air from the outside.

SL: Have you actually talked to San Diego Unified lately? What are those conversations like?

KP: They’re just trying to figure out how to open, when it can open the most safely. The air thing is, unfortunately, I would say what they’ve got the least guidance on. There’s not a uniform plan for schools anywhere. San Diego Unified will be safe, I promise, when you go back. I’m going to help, and there’s other people that are going to help. I’m talking to all the other people that are helping all across the country reopen schools and what they’re doing and what they’re recommending. So, you know, the biggest thing is just how and when to open safely. The other thing I will say, this is a little plug to the public, that if people would just listen to what they’re being told in terms of, you know, stay at home as much as you can, wearing masks when you’re out, social distancing. I hear people will say, “Oh, masks are taking away our freedom.” It’s quite the opposite. If we wear masks, we can go out. We can get our lives going again. They’re a little inconvenient. They’re getting some nicer ones out there. We’re trying to get better materials. We’re going to have them for a while. But if we keep delaying, if people keep balking, we’re going to sit here for another five or six months. It won’t go away. But we have the power as a community to decide. Look at other places that have done it like New York. They all decided as a community, we’re in it together. They had to see a lot of deaths. I don’t want us to go through that to believe that you can.

If we just started today, if everybody in San Diego just said, we’re in this. And I do see it’s getting better, which is great. It’d be about eight weeks. We estimate that it would be so much safer to open schools. So we can either make a plan now and force our way back into schools and then probably have it not work so well because there’s still quite a bit of community spread here in San Diego. Or we can just buckle down and do the right thing and open school safely, much more safely in eight weeks. So what that means is that people have to be happy with dining outside. We’re in San Diego. It’s not that bad. And you know, we have to quit pushing. Because if we keep starting and stopping and kind of going and kind of stopping, it’s just delaying it. And then we’ll never open the schools. And then we’ll never get daycare and childcare and all that stuff going, you know what I mean? So, the order has to be buckle down, eight weeks, open school safely so that you don’t get a rebound and then everything should take off. But this start and stop is not working.

Megan is Voice of San Diego’s director of marketing. She is responsible for producing and overseeing strategies that extend the reach of the organization....

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