Sweeping public health acts for everything from clean water to the control of cholera have revolutionized modern life as we know it. The Clean Air Act, which sets standards for outdoor air, has been around for decades. But as we spend more time inside amid the pandemic, scientists are now recognizing the need for a new form of quality control: regulating indoor air. How do we design and reconfigure spaces to have cleaner air capable of combating airborne viruses? This week, Chris talks with a leading expert on the topic. Dr. Linsey Marr is a professor of civil and environmental engineering at Virginia Tech and has spent over a decade researching the transmission of airborne viruses. She joins to discuss the science behind how COVID is transmitted within structures, the short- and long-term effects of regulated indoor air and why an Indoor Clean Air Act could be transformative in homes, schools and businesses.
Note: This is a rough transcript — please excuse any typos.
Linsey Marr: We have outdoor air quality standards in many countries worldwide, which has been useful for improving our outdoor air quality. But we spend on average 90% of our time indoors. And so, if we’re worried about health, we should be thinking more about the indoor air. It’s not just for the respiratory virus pandemic.
Chris Hayes: Hello and welcome to Why Is This Happening with me, your host, Chris Hayes.
So, I think everybody knows that there was a time in countries like the U.S. or the U.K., particularly where waterborne illness was common. There’s very famously a cholera outbreak in London, which is the subject of a phenomenal book by Steven Johnson called Ghost Map, in which people started getting cholera and a bunch of kind of infectious disease experts figured out using this map that this was because it was from a contaminated well.
And if you’ve traveled across the world, one of the key indicators often of development, the development level of a country is the cleanliness of its water supply, can you drink the water. It’s even like a cliche, like don’t drink the water. People would say that about Mexico 20 years ago.
By the way, Mexico City has like perfectly good water now. I happen to know this because I have a friend who’s like an anthropologist who literally studies the Mexico City water supply. But water quality as indicator of development was this kind of key metric and it says something about the ability of a society to marshal collective public resources to create the conditions for public health and sanitation.
It would seem really crazy if the solution for London to cholera was, well, everybody just filter your water. In 2022, like they never went through the collective process to improve water quality in a collective way, so that what came out of the tap was drinkable, and instead said, the water is not great, but do what you can. See if you could buy a filter, maybe buy bottled water. That’s not the way we deal with water quality.
Same thing is true for outdoor air pollution. We have the Clean Air Act, which regulates outdoor air pollution. The levels of outdoor air pollution tend to be quite correlated with levels of wealth and development in a country. Countries that are in the process of developing rapidly often have a lot of air pollution to deal with. Air pollution is incredibly, incredibly dangerous and bad for people.
In fact, every week, it seems we learn more about how bad air pollution is for people for the development of children’s brains, for long-term health effects, life expectancy, all these things.
Then there’s the question of indoor air. Indoor air, we don’t really think about it. I never thought about indoor air quality once in my life before the year of 2020. I mean, sometimes you’d be like, “Oh, this room is stuffy. Let me open a window.” Or, “Oh, it’s cold. I’m going to put an HVAC unit.”
But it never occurred to me that there was anything even to think of about the air circulating in, say, 30 Rockefeller Center, the place that I work. To think of one way or the other along the metrics of health, the way that you might think about water when you travel around for air quality. Then, of course, this big thing happened, which is that a once in a century pandemic of a airborne respiratory virus started getting around.
The more we learned that indoor air quality was an enormously important thing, that close quarters indoors with insufficient airflow filtering or outside air coming in was going to produce conditions in which lots of people got the virus. One way to think about all this is, well, we have masking and that helps.
But masking is a little bit – to take the analogy – it’s a little bit like telling people in London during the cholera thing to boil your individual water. What we would like to get to is a universe in which we have just created the conditions, the regulatory structure, so that indoor air is as clean as it can possibly be, whether that’s in schools, train stations, public places, places of worship, concert venues, karaoke bars, all the places that inside the people congregate that we have a set of technologies and regulations that are deployed that won’t completely get rid of the risk of transmission of airborne viruses, but would greatly reduce it.
Right now, it seems like we’re not doing a ton on that front. Yet, it seems to me one of the most promising and one of the most important and so I wanted to talk to a person who just thinks about this, just thinks about airborne transmission of viruses, and air quality and indoor air quality.
So today, we’re going to talk to Dr. Linsey Marr. She’s a Professor of Civil and Environmental Engineering at Virginia Tech. She’s expertise in airborne transmission of viruses, air quality, now technology. She’s a fellow of the International Society of Indoor Air Quality and Climate. She serves on the National Academies of Sciences, Engineering, and Medicine Board of Environmental Studies and Toxicology, she’s a member of the American Association for Aerosol Research. Dr. Marr, it’s great to have you on the program.
Linsey Marr: Thanks so much for having me. It’s a pleasure to be here and talk about some of my favorite topics.
Chris Hayes: Well, let me start with that metaphor, if that scans to you, like this idea of water quality, and outdoor air pollution as threats to public health, threats to public well-being that have to be tackled through collective public effort and regulation, through a public health framework and that’s something that we should now be applying in the realm of indoor air.
Linsey Marr: Absolutely. The waterborne disease analogy really resonates with me, because I was trained in environmental engineering and environmental engineers are formerly known as sanitary engineers or sewage engineers are the ones who helped bring about water treatment that we have, we can turn on our taps, and drink the water, water goes down the tap and it doesn’t end up totally polluting our rivers, ideally, because we set up all these treatment systems. That was maybe a hundred years ago.
Before that, you couldn’t just take that for granted and waterborne disease was one of the major causes of death, especially for young people. Now we’re at a point where we’re realizing, oh, we have all this airborne disease around not just COVID-19, but probably colds and the flu. The flu in the U.S. kills an average of 30,000 people per year, far more than that worldwide and we’re at a similar point where, oh, maybe it’s time for a revolution in our indoor air, where we spend about 90% of our time, we’re breathing this all the time and it’s making us sick, not just with diseases, but also other pollutants in the air.
I think we’re at a point where things are going to shift and we’ll have kind of much healthier air in our buildings, if we start addressing this problem.
Chris Hayes: How did you get interested in this topic? I did not know this. I mean, obviously, people can study anything and everything in the world. You’re constantly learning new areas of inquiry. It never even occurred to me that this was a thing that people studied or were experts in just because I think we all take it for granted like how did you get into this topic?
Linsey Marr: Well, as you mentioned earlier, outdoor pollution, people recognize that and that’s where I got my start looking at emissions from cars and trucks and how they move around in the atmosphere and undergo reactions and how they affect our health. But then I kind of realized, well, we actually spend 90% of our time indoors and the air indoors is not equal to the air outdoors. There’s different sources and, obviously, with pathogens coming from humans, those are more indoors than outdoors.
So I was studying indoor air and then I had kids, 14 years ago, my first child. That really changed everything for me in my whole life, obviously, but also in my research because he started daycare, and we’d get the phone call every one or every week or two of, “Your son is sick. You need to come pick him up,” and I’d go pick him up and I’d find out that, well, half the kids in the room were sick all at once or even more than that, sometimes three quarters of the kids were sick.
I knew this daycare center had really good hygiene practices, lots of washing your hands, wiping down surfaces. So I started to wonder, well, could the diseases be transmitted through the air, because that would be much easier. Everyone’s there sharing the air all day.
I did some reading in the literature, scientific papers and I was surprised to find out that we did not even know really how the flu was spread, whether it was through direct touching or maybe people coughing on you or possibly through the air. I think people thought we knew, but some of the explanations that I saw just didn’t make sense with my understanding of how particles move in the air and viruses are really just another type of particle and they obey the same laws of physics as our particle air pollution does.
Chris Hayes: It’s funny you say that because it is such a distinct moment of being a parent, where as soon as you start putting them in environments with other kids, they start getting sick a lot. Then you start getting sick and the household sick all the time and it makes you realize, you’re like, oh, I remember being a kid and getting sick a fair amount. Then I remember a period of my life as a young adult where like it just didn’t happen. Maybe it happened once or twice a year and now I’m back here where like there’s a cold going around all the time.
Clearly, there’s one variable that’s changed. I have a kid who’s in a contained indoor setting with other kids all the time, who is now a vector – this is all pre-COVID for me – a vector of transmission. It is a rude awakening, but it’s funny that I think we all just take it for granted. Like you just think, well, kids are snotty kind of, like touching each other like, of course, they’re getting each other sick, but you had the thought of like maybe this is preventable.
Linsey Marr: Yes. A hundred years ago, people just kind of lived with waterborne diseases like cholera, which you mentioned. It was not unusual for someone to have their younger sibling die during childhood. Right now we just kind of live with colds and the flu, we just accept them as part of a way of life. But I started thinking, well things change for waterborne diseases, why can’t they change for airborne diseases.
Really, for the past two years, I don’t think I’ve had any respiratory infections —
Chris Hayes: It’s amazing.
Linsey Marr: — maybe something really mild. Usually, I would get two or three per year. When my kids were younger, it was kind of constant, so it’s made me realize and others too like maybe we don’t have to live with this. Right now, our buildings are engineered to have a comfortable temperature and to keep odors down and for energy savings and really, that’s it. They’re not engineered with the thinking in mind of, oh, we should try to reduce transmission of disease in our buildings.
Actually, one of the side effects of designing for good energy savings is that our buildings are tighter, the air can become staler and that means that viruses and bacteria and things can build up in the air and then if someone is sick around then everyone else in the room is going to be breathing those viruses and bacteria, too.
Chris Hayes: Let’s talk about airborne transmission. There’s a strange story here, which is that there was real resistance on the part of a lot of people in public health to describing COVID that way. There was a real debate, I mean, this was a very unsettled thing. There was back and forth the WHO and others. There was a sort of vanguard of experts who were like it’s airborne, it’s airborne, it’s airborne.
If you look at the folks in Asia, particularly in the Asia-Pacific, this includes; New Zealand, Australia, Vietnam, Cambodia, Thailand, Singapore, Taiwan, China, Japan, South Korea, they were all kind of acting from the beginning like this is airborne, masking ventilation makes sense. Why didn’t we realize this? Why was this a subject to debate? What do we think? How do we think it was transmitting and how is it actually transmitting? I never actually understood this.
Linsey Marr: Doctors in this country thought that colds and flus, and this virus initially, were transmitted mainly when people cough or sneeze in each other’s face when they’re close to each other and that there’s these large, wet droplets that you can see that come out of your mouth when you cough or sneeze, and they land in someone else’s eyes or on their nostrils or on their lips, and that that’s how the disease is transmitted.
That has been kind of the conventional wisdom within the medical community for the past 50 to a hundred years. But I knew when I first started studying this 14 years ago and reading about how they think about transmission via these large wet droplets versus what they had called airborne transmission or aerosols, it just didn’t make physical sense.
Because when you’re close to someone – well, there’s a couple things going on – first of all, when you cough or sneeze, in addition to those large, visible wet droplets that are kind of gross and that you can see, there are hundreds of much smaller droplets. They’re microscopic. We can’t see them. We call those aerosol particles or aerosols. When you just breathe or talk, those are coming out too, those smaller ones.
Those are coming out of our mouths all the time. I know from my research and other people’s that those can contain virus and these very small particles, I know, from physics that we learn and I teach in my class that size of particle can remain floating around in the air for many minutes to hours, so that was part of it.
As part of the conventional wisdom about how these diseases were transmitted, airborne kind of had this very special definition, which was transmitting at long distance – so beyond six feet – and then it also had a special meaning in hospitals where if you say the word airborne, that means that you need to follow a certain set of procedures, including providing N95s for all the healthcare workers and putting patients into negative pressure rooms. That is resource intensive, so you really don’t want to do that unless you really have to.
Chris Hayes: Sorry. Negative pressure rooms have a fan blowing the air out, right?
Linsey Marr: Yes. They’re sucking the air out so that if the patient is sick and they’re spewing lots of viruses into the air, it all gets sucked out and removed and it doesn’t spread into other areas of the hospital. That patient would be by themselves, you couldn’t have people together because if two people in a room because then one person could transmit to the other.
Chris Hayes: This is fascinating to me. So there was a special category that was airborne illness and then the other stuff was considered like assumed to be droplet?
Linsey Marr: Everything is kind of assumed to be transmitted by droplets. Airborne diseases were thought to be kind of really strange, like odd ducks, weird, unusual or rare. After much misunderstanding about measles and tuberculosis, they were finally accepted as transmitting by the airborne route. Again, the default assumption is that diseases are transmitted by these large visible droplets.
Now, interestingly, there is actually no direct evidence that a disease has been transmitted by these large direct droplets landing in our eyes, nose or mouth. We have lots of evidence that they’re transmitted by us breathing in viruses or bacteria from the air, whether we’re close to someone or whether we’re far away.
I think what was happening was that transmission, epidemiologically, you can see, well, people tend to get sick if they’re close to another person. Well, what’s happening is that they’re actually breathing the other person’s exhaled viruses or bacteria. It’s not because these large wet droplets are landing in their eyes, nose or mouth it’s like being close to a smoker, you’re breathing a lot of smoke when you’re close to them compared to if you’re farther away.
I think there was some misinterpretation of that data or that observation. Early in 2020, there was a nice paper that came out showing that, okay, if we consider about breathing in these microscopic particles from the air versus having these large wet droplets land on you, you have to be uncomfortably close for those large wet droplets to be more important than breathing in the aerosol particles.
Chris Hayes: Yes. What you’re describing, A, it makes a lot of sense of some of the early public health messaging, which was don’t touch your face, wash your hands, clean surfaces, because that’s all droplet focused. Those are all ways of mitigating what would be droplet exposure.
But you’re also describing, I don’t think I quite conceptualize the size and scope of the error here, like back when we’re talking about cholera, there’s people that think it’s like the humors or there’s something called the miasma theory.
Linsey Marr: The air.
Chris Hayes: The air, right.
Linsey Marr: The bad air.
Chris Hayes: The bad air. There’s this miasma theory that people use and that there’s all sorts of stuff like opening windows, blah, blah, blah, people operated on it, but it was just wrong. The cholera wasn’t traveling that way. The cholera was traveling through water.
It sounds like you’re describing something like that’s almost that level of wrong, the conventional story here.
Linsey Marr: Yes, I would agree that it is quite wrong. Now, I think cholera, I think, plays into this because once people realize, oh, cholera was waterborne, it discounted and disproved the miasma theory of the bad air are bad humors and so that was left behind.
Chris Hayes: Right. It’s like a discredited theory that you don’t want to go back to.
Linsey Marr: Exactly.
Chris Hayes: Right.
Linsey Marr: Exactly.
Chris Hayes: So if you start talking bad air, it’s like you’re talking about bleeding people or something, like this is a discredited theory for disease transmittal.
Linsey Marr: Exactly. Now, miasma and cholera were thought to come from like bad air from dead bodies that was wafting around outside. What we’re talking about with airborne is very different, we’re talking about people who are infected and are releasing viruses into the air, which are going to be just like cigarette smoke more concentrated close to that person and it’s going to spread throughout the room.
If the room is poorly ventilated, you have no windows, no doors, no fans or anything, that can build up in the air over time, and everyone else who’s in the room is going to be exposed to that and will end up breathing some of that.
Chris Hayes: We’ll be back after this quick break.
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All right. So it becomes clearer over time that COVID-19 is in fact transmitted in these airborne particles, describe the physics and biology of this, so walk me through it like there’s these microscopic, it’s a virus.
Linsey Marr: Yes. The virus itself is very small, it’s a 10th of a micron. Just for reference, your hair is about 50 to a hundred microns in diameter, so we’re talking about something that’s really tiny. Now, if you’re infected, there’s lots of these virus particles in your body along your respiratory tract, but they’re not coming out just naked by themselves. Just in the normal course of breathing or talking and coughing and sneezing, we generate respiratory particles from the fluid that lines our respiratory tract, you could think of it as like mucousy, saliva type material that goes all the way down into our lungs.
One way that that’s generated is that in those small airways, you can imagine a straw or a really skinny straw, as it opens and closes, there’s this kind of film of layer like if you’re blowing bubbles, that kind of forms across there. As the airway opens, that kind of stretches out and it breaks and it poofs and it creates these tiny microscopic particles of respiratory fluid.
That fluid is not just water, it also contains salts and proteins, mucousy, snotty stuff and the viruses could be in there too. You exhale, talk or —
Chris Hayes: Sing.
Linsey Marr: — just breathe out.
Chris Hayes: Shout.
Linsey Marr: Those come out. They some of them might be carrying viruses in them. They are very small. They range in size anywhere from, well, the smallest one you could have would be size of the virus, but the virus isn’t naked, so it’s probably in things that are a little larger, all the way up to things we can see. But the ones that we can’t see are far more numerous. There’s probably hundreds of them for every one that you can see. Those come out into the air. They evaporate a little, so a little. The water is lost, but there’s still a lot of salts and proteins and other gunk left behind along with any virus.
Those are small enough to remain floating around in the air for a while. They kind of span a range of sizes and behave like cigarette smoke particles and that they’re more concentrated close to the person who released them, who’s anyone really. They travel more than six feet. Cigarette smoke doesn’t just stop at six feet. It can fill a room if it’s poorly ventilated.
If you’re outdoors, obviously, it becomes rapidly diluted and it’s not as much of a problem.
Chris Hayes: Cigarette smoke is I think useful conceptually. It’s helping me conceive of what we’re talking about. Do people have the reaction? Do they get grossed out when you’re talking about this? Because I find it weirdly like, oh, there’s all this mucus, and gunk, and proteins floating around. I guess that’s just what it is to be a human breathing air around other humans.
Linsey Marr: Yes, that’s what it is. I mean, I’ve shown some videos before. I think they were from the New Zealand public health department from years ago. They show people in slow motion, sneezing, I think and it’s really pretty gross. That’s where the visible thing that you can see.
We have to use our imagination, because these are things we can’t see. But people have talked about sharing the air is kind of like being in a swimming pool with someone who’s peed in their maybe.
Chris Hayes: Right. These are suspended in the air. How long can they last in the air? If you’re in a room, I’m in a one-room studio structure right now, pretty small, say 400 square feet, if you’re in here and you had COVID and you exhaling, and then you left, and then I come in the room, does it dissipate? Does it fall to the ground? Where does it go?
Linsey Marr: Yes. Kind of all of the above. There’s three main ways it can be removed. The first is through ventilation, which is the air in your studio probably changes out, even if you don’t have doors open, air comes through cracks and things around the edges of the doors and windows and other ways. It probably changes out every one to two hours. Some of those particles are small enough that they can remain floating around for more than that.
They’re just hanging out until the entire air moves out of your studio, which would be one to two hours. Some of the ones that are a little bit larger could hang around. They may fall to the ground. The bigger ones fall faster than the smaller ones. The things that we’re talking about probably take anywhere from 30 minutes to a few hours to fall to the ground. But if they haven’t fallen to the ground, within a couple hours, they’ve probably been removed by the ventilation effect.
Then the other thing is that because we’re talking about a biological organism, even if it’s still physically present, it can die off over time. Studies have shown though that this virus is pretty hardy and it seems to survive in these aerosol particles for hours anyway, so that doesn’t seem to be a limiting factor.
Chris Hayes: Then, when I inhale it, so let’s say just to keep track of the transmission, so there’s some parts per million, I guess, of a virus in the air. I don’t know how you quantify it.
Linsey Marr: Yes. We talk about so many viruses per volume of air that you breathe in. Yes.
Chris Hayes: Okay. So there’s some quantity and I’m breathing it in. Let’s say there was these two weeks in New York in December, basically, after Thanksgiving like one weekend after another weekend where it was like, oh, we’re vaxed and boosted and we’re not going to go through another COVID winter and so and so is having a birthday party, and so and so is having a holiday party and we’re going to go to those. Then like literally the next day it was like, well, everyone at the party got Omicron. This was before we realized how much Omicron was out there.
So you’re at a party, this is perfect transmission, the music’s loud. I’m like shouting at you to be heard, which is why bars we know are just like the worst. I’m shouting at you to be heard. Because I’m shouting, I’m expelling even more than I normally would, so there’s more and more in the air and you’re also like leaning in. You’re trying to hear me. So you’re inhaling it, what happens with the virus when it enters your air passageway?
Linsey Marr: Yes. So you inhale, it goes in through your nose or your mouth. It’s in these respiratory particles. Depending on how big they are, they could deposit like they could kind of come into contact, touchdown, let’s say, on the inside of your nose or maybe the inside of your throat or maybe they’ll get even deeper down into your lung and the larger ones could either settle or as they’re going around the curves in your respiratory passages, the air is moving fast and they’re too big to make the turn, so they slam into the inside of your nasal passages.
Or another way is that if they’re really small, then they have a bit of random motion to them and this is also how masks and N95s are able to filter out really tiny particles smaller than the holes between them. But anyway, really small particles have this random motion associated with them, almost like, I like to say, a drunk stumbling around and they may stumble into the walls of your respiratory passages and then stick there. Then that’s where my knowledge ends and we need to talk to a virologist about kind of what happens at that point.
Chris Hayes: Right. Because then they bind on with the receptors and they get in there and they start —
Linsey Marr: Right. They get into the cells and they start replicating.
Chris Hayes: I guess the next question then becomes to think about airflow and ventilation inside structure. I just had this very interesting experience, which was the opposite of this and you referenced it before, so I’m going to call that, which is that I did a weatherization efficiency upgrade on a house where they do what’s called a blower door test. They create negative pressure, you close all the windows, you open the door, they like sort of zip a fan in and the fan is blowing out at like 60 miles an hour, so there’s incredible negative pressure.
What you’re testing is that negative pressure is sucking air into the house and you’re able to sort of sense, you can even put your hand places and you can feel where outside air is coming in or you can use a heat gun, which is also really cool, because it’s like you’re doing it in the summer, for instance, you can see where the hot air is coming in. Then they went about sealing up the house because it was incredibly inefficient. That’s one way to think about like efficiency. First of all, what’s the basic dynamics by which air enters and leaves an indoor space? Like let’s just start at the most fundamental way of like how does that happen?
Linsey Marr: It’s most obvious if you open a window or door. The wind is blowing and it blows air through there. I’m glad you went through the process of trying to seal up the cracks, there’s always those types of cracks and things around and so there’s temperature differences like the ceiling is warmer than the air near the floor and so that sets up these kind of thermal forces that move the air around.
Between inside and outside, you have differences in temperature and so the air is going to want to come in or out through those cracks. If you have wind blowing on the building, even if you have the doors and windows closed, air can come in through these cracks under the door and other even just like kind of where the walls and ceilings and floors meet. Those are areas where the air can – what we call infiltrate.
Then if you have an HVAC system, some kind of forced air heating cooling system, then that actually intentionally brings in some outdoor air, some systems bring in all outdoor air, some bring in just a fraction of outdoor air, but that’s another way that you’re getting outdoor air moving through your residence.
Chris Hayes: In the structures that we’ve spend a lot of time in which are schools, office buildings, large public spaces and homes when we don’t have the windows open, like a lot of that is our HVAC systems, basically. If you’re designing a large office building, a big part of that design is going to be the airflow, right?
Linsey Marr: Oh, yes. There are engineers who are dedicated to designing and installing HVAC systems and there are standards that they are supposed to meet that are put out by a professional organization called ASHRAE for the American Society of Heating, Refrigeration Air-Conditioning Engineers. The system that they install is supposed to be designed depending on whether you have a gym or a school or a nursing home or a restaurant, it’s designed to put a certain amount of air through there. The initial intent is there, often they may not be maintained and operated correctly, so you may not get the intended performance.
Chris Hayes: Are the standards written as they exist with the idea of airborne illness in mind?
Linsey Marr: Absolutely not. They are written with the idea of odors in mind. I’m actually serving on one of the committees that is revisiting these standards to think about how we might update them to account for the spread of disease indoors.
Chris Hayes: My next question becomes like how solvable a problem is this with proper ventilation? Because it just seems to me like you’ve got all these particles and got people around each other. They’re going to be in the same space like how good can you make it such that it’s just like whisking the virus like right out of their mouth?
Linsey Marr: Yes. You’d have to have pretty high ventilation to do it right out of your mouth, but we know there are studies that have shown that if you have higher ventilation, you have less incidents of tuberculosis in one study or of other respiratory diseases like colds. That was a study done in a dormitory in Maryland by a team at University of Maryland.
We know that there is empirical evidence, observational evidence. We also have just based on fundamental understanding of how viruses move around in the air that if we have better ventilation, that will bring down the amount of virus in the air fewer people will get sick. Hospitals do this. They have to have – we talked about in your studio – maybe the air changes over every one or two hours in hospitals. That happens every like four to six minutes or four to 10 minutes. It’s much faster. That’s possible.
I don’t know if that’s practical for all other buildings, but there are other things you can do besides ventilation to reduce the amount of virus in the air. Those include filtration and also there’s a germicidal UV treatment, which are very effective too. With filtration, you’re just removing the particles from the air. With germicidal UV treatment, you are very effectively killing off the virus in the air.
Now, these things were kind of at the room scale, but if you are really close to someone, and you’re at the birthday party, and you’re yelling, because it’s loud and they’re close, because it’s loud, these things we’ve talked about; the ventilation, and filtration, and UV, they’re not going to help much because there’s no time for those respiratory particles. Before they go from the other person’s mouth to your face, there’s no time for them to pass through the ventilation system or filtration system or be inactivated or killed off by UV and so that’s where masks are quite useful. Outside of those situations, ventilation can make a big difference.
Chris Hayes: Let’s talk about those two, the filters and the germicidal UV and just walk through. We’ve purchased a few HEPA filters at different points in the pandemic. We actually used them for our holiday gatherings. We had people here. We had everyone take a rapid test. Then as a kind of backup, we put the HEPA filters on.
I think it’s probably an added layer at the margins of protection. It’s not going to stop people from getting COVID, did that make sense?
Linsey Marr: Oh, yes. No, I think HEPA filters can be really useful and I would say not marginal but one of the very effective layers of prevention by, again, reducing the amount of virus that’s in the air. Again, if you have a smoke-filled room and you turn on your HEPA filter, that can really filter out the particles well.
The key thing is to look for a portable air cleaner or HEPA air filter unit that passes enough air through it that you’re actually going to bring down the amount of virus and other particles in the air. Because if it just has just a small amount of air passing through it, it’s only treating a small amount of the air, so in order for it to work, the air in the room has to pass through it. It needs to have high enough of what we call a clean air delivery rate for the size of the room that you’re in.
Chris Hayes: So that’s the number to look for?
Linsey Marr: You’re looking for a high clean air delivery rate. Sometimes they talk about, oh, this air cleaner is sized for a certain area of room, so many square feet, so you definitely want to get one that’s sized for your room. Or better yet, if you want an extra protection, get one that’s even bigger, bigger than you need.
Chris Hayes: Oh, I see. So they’ll size them for the square footage?
Linsey Marr: Yes. Sometimes they’ll advertise it for a certain amount of square feet, go big.
Chris Hayes: We’ll get back to germicidal UV, but this connects to a question I’ve had. Schooling has been a very contentious issue and for understandable reasons. You have, until recently, very large unvaccinated populations, children that were not eligible for the vaccine now they are. But you’ve also got kids indoors and to return to our original story of kids as transmitters of infectious disease, like lots of stuff moves around school germ-wise.
It’s been very controversial. There was something like almost $200 billion in the ARP to improve schools and make them safer. That money got spent on lots of things, including like new football stadiums in some districts and things like that. I’m a little frustrated with it, because it comes down to about a million dollars per school structure in America and it just seemed to me like just at a base level like you could just buy a HEPA filter for every room.
Linsey Marr: That would be a very effective use of the money if you’re trying to reduce transmission in schools or upgrading the HVAC system, older schools certainly could use that so that it can run more air through there or it can handle more effective filters. But that would have been a very good way of spending the money if you wanted to address transmission.
Chris Hayes: When we say upgrade HVAC systems, what do you mean by that?
Linsey Marr: We’re talking about the system. If you have an older system, it may not be capable of handling better filters, so the HVAC system has filters in there that remove particles from the air and there are different levels of quality of filters. There’s ones that you just put in your house that probably aren’t that great. They can stop leaves and big dust balls, but there’s also really better quality filters that could filter out a lot of the virus.
Those, however, it takes a little more work. It’s a little harder to push the air through them.
Chris Hayes: Got you.
Linsey Marr: You need to have fans or blowers in your HVAC system that are capable of handling that without burning out. That’s one way of doing it or installing a system where you can adjust it easily to bring in more outdoor air during periods when the building is occupied. There’s some cost to that, because if you’re bringing in more outdoor air, that means you have to do more heating or cooling, so there’s there are some trade-offs. Those are a couple of other things.
A lot of systems really would benefit just from some routine maintenance, make sure everything’s working. I’ve seen stories of ones that people find out that parts of it aren’t working or broken and it just needs some attention.
Chris Hayes: Well, this is the thing about HVAC is that they’re actually pretty labor-intensive and like good ductwork is not as it exists now and at least in just in my experience with it. It’s a very hands-on part of a building. It takes maintenance, it takes costs, it takes some real expertise to make sure that the ductwork is air sealed, that it’s well done, that it’s not coming apart. All of those are not trivial concerns, like you have to actually know what you’re doing.
Linsey Marr: Yes. Additionally, do we have enough expertise to address every school right now? No. But hopefully over time we could, over a longer timeframe. Then I think the HVAC system – nobody sees it really or even or thinks about it and so spending money on it is not the first thing that comes to most people’s mind.
Chris Hayes: Talk about germicidal UV, because that I’ve not encountered. HEPA filters, we own a few and those are fairly straightforward.
Linsey Marr: Yes. Germicidal UV is used very effectively in hospitals in certain areas and there’s a couple of ways of doing it. One is that you can have UV in the HVAC system, so the filters can remove virus. Germicidal UV can kill off the virus and you don’t need a filter, but it has to be well designed so that there’s enough time for virus to be exposed to the UV light to kill it off. If it just whooshes by and that’s it, that may not be enough to kill the virus.
Another way of doing it is putting it in the room what we call upper-room UV and that would be where you put it up towards the ceiling, because UV light can be harmful to people so you don’t want people to be exposed to it. But if you put it up in the ceiling kind of aimed upward toward the ceiling then air that’s passing by there, any viruses or bacteria will be killed off. That can be very effective. That also requires special expertise in designing to make sure you’re installing something that’s going to be effective and won’t harm people.
I think it’s worth thinking about that type of treatment in places that are especially risky, things like a crowded school cafeteria, for example.
Chris Hayes: Right. Because there you can’t really mask, you got people yelling, you got people eating. There’s lots going on there.
Linsey Marr: Yes. That is kind of one of my – where would I not want to be during a respiratory virus pandemic and it’s crowded, people are on these tables packed together. I’ve attended lunch with my kids once when they were young. It is loud in there, people are yelling and, right, you can’t wear a mask.
Chris Hayes: Are there places that are doing a really good job of this to point to of using – whether it’s new money available or thinking about it in the terms of COVID and the pandemic to really change the sort of air quality and respiratory infrastructure?
Linsey Marr: There are. I’ve heard of a restaurant. I know one of my colleagues at the University of Colorado is consulting for. This restaurant has installed sensors for carbon dioxide, which is in our exhaled breath. So it’s an indicator of how good the ventilation is, lower is better. They’ve also installed some sensors for particles in the air. Now, you have to be careful with that because there’s far more other types of particles in the air than there are people’s respiratory particles. There’s just like dust particles coming from skin flakes and dirt and other things around.
It’s not really a direct measure of respiratory particles, but it can tell you something about if the level is really high and you turn on some filtration device and it comes down, it shows that your filter is working. I think they have also put small HEPA filters around the restaurant and I think they may even have them on tables. I’ve heard of a restaurant in Canada that did this too. They kind of isolated different seating areas and then put a portable HEPA air cleaners on each table or in each partitioned area. That seems like a great idea for making diners safer during a pandemic.
Chris Hayes: It also seems that – to go back to this sort of original conceit that there has to be – I think you may have even tweeted about the idea of a Clean Air Act, an indoor Clean Air Act that some macro intervention that says, look, we don’t have to live with this level of airborne disease, there’s COVID but there’s other stuff too and there might be another pandemic down the road.
In some ways, I think one of the things that you’ve seen in this is that the experience of SARS had a kind of inoculating effect on the Asia Pacific region that has been much better in dealing with COVID than almost any other part of the world, partly because of the trauma of SARS and having to deal with that and recognizing this airborne and recognizing it as a respiratory illness. If we were doing that here, like if you and your colleagues were getting together to draw up an indoor Clean Air Act, how would we think about that?
Linsey Marr: Well, I would kind of use some of the ideas of the outdoor Clean Air Act and one of the main things there is setting standards. We have standards for outdoor air pollution where if the amount of particles or amount of ozone in the air is higher than a certain level, then localities are required to come up with a plan to address that and try to bring the levels down. It requires measurements, of course, to know what your air quality is outdoors and so we have hundreds of monitoring stations around the country that measure our outdoor air.
For indoor air, we have almost no information and so I think the first step would be to setting some standards and it would take some work. We’d have to have a scientific expert committee working on this. There would be disagreements, I’m sure, but I think they could work through. We have enough information available that they could come up with some metrics for easily measurable pollutants that are in indoor air, where at least we have some benchmarks or some targets so that people know, oh, is my air quality good or bad or somewhere in between.
If it’s bad, then, okay, what do we need to do about it and that brings up another piece of this kind of indoor Clean Air Act, which is kind of providing advice or, I guess, having some kind of reference about good ventilation practices, and filtration, and UV treatment and then ways to make it easier for the average person to evaluate those systems when they’re out shopping for them, because right now it’s a marketing mess, really.
Chris Hayes: Right.
Linsey Marr: In addition to the technologies I mentioned, there are other things out there that are being marketed as cleaning the air killing off the virus that really don’t do what they claim and so something to help sort through that and make it clear, improve transparency to the consumers of what really works and what doesn’t.
Chris Hayes: That’s great. Like the appliances have those energy ratings that are regulated, that you know that they can’t just make up what their energy rating is, like there’s actual regulation that guides that. Like something for that for things that deal with airflow and air circulation, where there’s some stamp that says like what you’re getting here and what it will do.
Linsey Marr: Yes, exactly. The energy star idea is a great one for this, so, yes, the indoor air star or the air star, whatever it is.
Chris Hayes: Are there places that do this very well outside the U.S. or the places that have really thought about this and implemented this at scale?
Linsey Marr: There are not a lot of indoor air standards around the world. I think there are only a few countries that I know of that have them. I think South Korea has them and I think Taiwan has them for certain types of buildings like schools, and universities, and train stations and other big public buildings. I’ve heard that in Japan is not uncommon for stores to have a carbon dioxide monitor and to display that level in the window so people know, can decide when they’re outside whether to go in or not. If the level is high, it’s like, oh, no, okay, maybe I’ll come back another time.
Then, I heard that a country in Europe had also implemented that idea of making carbon dioxide measurements more easily available to the general public. But beyond that, I’m not aware of anything. But I think it’s something we really need at this point. We have outdoor air quality standards in many countries worldwide, which has been useful for improving our outdoor air quality. But, again, we spend on average 90% of our time indoors and so if we’re worried about health we should be thinking more about the indoor air, not just for the respiratory virus pandemic, but we’re talking about asthma and other illnesses, and academic performance and productivity. We’re talking about kids and workers, if they have healthy, good air, they’re going to and we as a country will be more productive.
Chris Hayes: Do we have evidence establishing that?
Linsey Marr: Yes. There are a lot of studies showing that with better air quality you get better, what I mentioned, like better test scores, reduced absenteeism, reduced asthma attacks, reduced number of doctor’s visits and things like that.
Chris Hayes: There’s also – I don’t know if you sent this over or tweeted it – that China has developed a bioaerosol nucleic acid detection system they’re going to use in the Winter Olympics and I didn’t quite understand what it was, but is it testing the air for COVID?
Linsey Marr: I believe so. I think what it’s doing – it’s not like a new approach, overall, my laboratory and other laboratories around the world do this. We collect air samples. We bring them back to the laboratory. We measure the nucleic acid and see if there’s the COVID-19 virus in there. I think what the next step is that they’ve made this all automated. They put it into a package that they can distribute easily to lots of different places. They don’t need PhD-level scientists running each one and they get the results fast. It’s all kind of built into the instrument what we would do in the laboratory that would take us a day for a PhD-level scientist to do that, it’s all automated in their box, it looks like.
Something like that would be amazing, I think. If you want to go to see a movie and they have that there and they can tell you, oh, yeah our air is virus-free or for at schools, for example, or workplaces even. Because another way you could do this is, oh, you test each person but that’s hard.
Chris Hayes: Right.
Linsey Marr: If you could just measure the air around that everyone’s breathing and if you detect it, that’s an easy indicator of, hey, if you find it, we need to do something about this.
Chris Hayes: It’s kind of wild to me that – well, two things here – one is that like I don’t feel like this will be the last pandemic necessarily. I think that airborne respiratory infections are a thing that we should be thinking a lot more about going forward. But in a weird way, this conversation has been more encouraging than I thought insofar as it feels like it’s not some huge, great leap forward really. I mean, when I talk about climate stuff, the transition to a hundred percent carbon-free grid and energy power system is daunting.
Now, the technology is getting closer and closer. In fact, you can almost argue it’s there and it’s 70% or 80% there, but it’s daunting. What you’re describing sounds less daunting, I have to say. Like it really doesn’t sound like this is something outside of our reach if we were to focus on this and implement it and provide the resources and the regulation, that this is something that’s quite doable.
Linsey Marr: I agree. I mean, it’s totally doable. We have the knowledge. We have the technologies available today to do this and it’s a matter of raising people’s awareness about it, making it a priority and putting the resources toward it. Any investment I think will pay off in terms of reduced health costs and improved productivity.
Chris Hayes: Dr. Linsey Marr is a Professor of Civil and Environmental Engineering at Virginia Tech. She studies airborne transmission of viruses and air quality. She’s a member of a whole variety of professional bodies that are working on this problem as well. Dr. Marr, it’s great to have you on the program.
Linsey Marr: Thanks, it’s been fun to talk with you about this.
Chris Hayes: Once again, my great thanks to Dr. Linsey Marr. If you’d like to hear more episodes, particularly about COVID, coronavirus coverage we’ve done, Dr. Peter Hotez was on talking about vaccines and vaccine efficacy. You can check that out in our archives. We’d love to hear your feedback. Send us emails WITHPod@gmail.com. Tweet us with #WITHPod.
Why Is This Happening is presented by MSNBC and NBC News produced by the All In team and features music by Edie Cooper. You can see more of our work including links to things we mentioned here by going nbcnews.com/whyisthishappening.
Tweet us with the hashtag #WITHpod, email WITHpod@gmail.com. “Why Is This Happening?” is presented by MSNBC and NBC News, produced by the “All In” team and features music by Eddie Cooper. You can see more of our work, including links to things we mentioned here, by going to nbcnews.com/whyisthishappening.