Coronavirus (COVID-19): Press Conference with Joseph Allen, 09/02/20

You’re listening to a press conference from the Harvard T.H. Chan School of Public Health with Joseph Allen, assistant professor of exposure assessment science and director of the Healthy Buildings Program. This call was recorded at 11:30 a.m. Eastern Time on Wednesday, September 2nd. 


JOSEPH ALLEN: Thanks, everybody, for joining. And a special thank you to Nicole and the Communications team at the School of Public Health who have been holding these. I think they’ve been really quite helpful from my perspective. So thanks a lot, and happy to join you. Just to talk about a couple of things a little bit more my background, so you know where I’m coming from. I direct the Healthy Buildings program here, my background is exposure and risk science. I’m a certified industrial hygienist. That’s the field that anticipates, recognizes and controls hazards in the workplace. So I am the deputy director for an Ayash funded Education Research Center on Worker Health and Safety. Maybe more relevant is, I guess, I’m on the Lancet Commission on COVID-19. And so I’m a commissioner there and also director chair of the Task Force on Workplace, School and Travel Safety. Outside of Harvard and before I was at Harvard, I’d led forensic investigations of sick buildings for over a decade. I still do some of this and advising companies and organizations across the spectrum of the U.S. economy, from finance and biotech to K-12 schools, universities, health care facilities, community childcare services, homeless shelters, police departments, I’m a special advisor to the Massachusetts Supreme Court of reopening jury trials. So all that to say is on my hands across and seeing across the country on, let’s say, what good plans look like and maybe what not so good plans look like. 

Two things on schools, I want to point out, we’ve put out a lot of resources on schools. My healthy building program is at and the school’s resources are at 60 page risk reduction strategy for schools with other Harvard faculty. We published a document on when to open based on community spread metrics, 20 questions every parent should ask before they send their child back to school, a how-to guide on how to assess ventilation in schools. Four op eds since June on this topic of schools and what we can do? Last thing I’ll say is there was a good article in the Wall Street Journal yesterday on ventilation that featured some of our work that got some attention. And then my op ed yesterday came out late last afternoon, which was on bio aerosols in the bathroom and flushing toilets. So lots to talk about. Happy to take any questions or take this any way you’d like to. Thanks. 

MODERATOR: Thank you, Dr. Allen and I will do my best to get all those links into the chat, if anybody would like to look at that. Looks like first question. 

Q: Oh, yes, hi. Thank you very much for doing this. I know this is a ground you’ve covered already, but if you could just kind of simply put. So if a school has pretty good ventilation and does a good job of enforcing mask wearing and limiting the number of students in a building at any one time, you know, plus other measures, do you think schools will be relatively safe to go to this year? And could you kind of delineate why that is or is not? 

JOSEPH ALLEN: Yeah, so thanks for the question. Two conditions precedent for returning to school and if they’re met, yes, I think kids should go back to school. First is low community spread. And this is the guidance we put out with other faculty at Harvard, including Danielle Allen at the Safra Center for Ethics, and Ashish Jha who is now at Brown University when he was leading Harvard Global Health Institute. Second condition precedent, is it can’t be schools as usual. You have to have these risk reduction strategies in place like hand washing, universal masking, and importantly, what we’ve been writing a lot about, particularly my area of expertise, ventilation and filtration. If those are met, yeah, I think kids should be going back to school. And the reason is this. The conversation on schools has gotten very reductionist from my perspective, talking about risk in a very narrow sense, risk in the classroom. We have to have a bigger conversation of risk, and that includes the devastating consequences of keeping kids out of schools. Today’s headlines will be about the occasional case in a school. Next year’s headlines are going to be about the consequences of virtual drop out, stories of abuse and neglect, lack of access to food. I mean, there are stories already from talking to teachers that they don’t know where their students went after March. So these stories are hidden from view right now. But we’re certainly going to see them because you can’t have this many kids not in school and not see those problems. 

MODERATOR: Do you have a follow up? 

Q: Yes, I do have one follow up. I know your expertise is a lot about buildings, but I’m wondering what you think about the extracurricular activities that go outside of buildings like school sports. You know, in Maine, they’re kind of wrestling with what to do with fall sports. Do you think, you know, with some modifications in place that sports can be played safely or should be played safely, in particular, football? 

JOSEPH ALLEN: Yeah, so it’s a really good question, and, you know, while I direct the Healthy Buildings program, my background and my title here is exposure assessment science. So that’s really about exposure and risk more broadly speaking. So I do feel qualified to answer that question on risk. And so my feeling is, yes, it’s not necessarily about the sport. It’s about the sport activity. And we took this on in our report at this risk reduction report, we called Schools for Health: Risk Reduction Strategies for Reopening Schools, and Nicole can post that link. But we talk about sports and actually break it down into a continuum of risk based on the activity. So, of course, outdoor is better than indoor physically distance, better than close contact, and small groups are better than big groups. And I think there’s a way to do sports. I know there’s a way to do sports safely. It doesn’t have to be competitive in your face, indoor basketball. But could there be boys and girls soccer outdoors? Sure. I think they could do all sorts of drills and activities that are engaging. I think you could have the intramural version of that so you’re not mixing with other schools, the kids can wear masks when they do this. I know this from my own son, there are sport masks that are available. So I know it can be done safely, and actually my personal opinion is that schools should be having sports because that way they can manage the activity. My big concern is that when schools go into these hybrid models and they end the day early, people are going to be seeking out other pods to spend time with, either for teaching or learning or basic care. And the same thing goes for sports. I’ve seen this already in my community. Kids are signing up for leagues that are not related to the school where the mixing then of kids across many different schools and a wider region. So I think there could be some unintended consequences to not having sports at schools. My personal preference would be to have it at schools, manage the interaction, wear masks. And especially through the fall, when these sports, especially for the sports that can be played outdoors. 

Q: What about football? If you could just address football a little bit. 

JOSEPH ALLEN: I think the same thing applies if you have a group, if they’re wearing masks, you can do football activities, right? You could do drills, passing drills, kicking drills, running drills within that unit of the kids that are in the school who are already interacting anyway in the school. And you can have intramural games or limit the number of contacts and only physical contact in the football sense, but with other schools and wider regions. So, yeah, I wouldn’t exclude football. I think it’s more about the sport activity than the sport, per-say. That is how we address this. I want to be clear that on the sports, the same conditions precedent apply right before this goes wide out to any community. You have to start with low community spread. And then you also have to put it these risk reduction strategies. Thanks. 

MODERATOR: All right. Next question. 

Q: Thanks for making time for this. I really appreciate it. I appreciate the discussion on schools. I’m wondering, Doctor, if you can talk a little bit about how some of what you’ve learned in terms of sick buildings and aerosols might apply to other buildings, apartment buildings, for instance, where there is a single HVAC, or even daycare centers or other places where people will gather. Let me ask it this way. Are there concerns that air conditioning units, for instance, could be spreaders or I’ve even seen in the media maybe super spreaders of COVID-19? Is there evidence to suggest that this is a concern that needs more attention? 

JOSEPH ALLEN: Well, thanks for your question. Two things. One, airborne transmission is definitely happening. We’ve been saying it since early February. I think people are just coming around to that now more widely. So that’s a good thing that people are starting to recognize as every piece of evidence since February has supported this hypothesis. Even new evidence just this week. And I’m happy to talk about that. But to your specific question of air conditioning, it’s not necessarily air conditioning that’s bad. It’s the conditions in how it’s operated. So, for example, if you are running a system with no outdoor air ventilation and no filtration. In other words, you are just recirculating all the air. Well, that’s going to lead to a build up of indoor pollutants, be it chemical pollutants that off gas from your carpet or in this case, the buildup of viral particles. If someone is infectious and just breathing, it’ll just build up over time. So when you have these particles in the air, viral particles or otherwise, you have a couple mechanisms of removal. One is some will settle out eventually, but many particles will stay aloft indefinitely until one of three other mechanisms happen. One, it’s diluted out of the air through ventilation, it’s cleaned out of the air through filtration or it’s deposited in the lungs. And of course, we’re trying to avoid that fourth one. So it’s less about the equipment you’re using, but for example, the now infamous outbreak in the Chinese restaurant related to an air conditioning unit. It wasn’t necessarily the air conditioning unit that was the problem. The problem was it was recirculating air without bringing any outdoor air and there was no filtration. So you just had the accumulation of particles. There was one infector, one infectious person at a table, and the air was just circulating around a group of people at three different tables. And we’ve seen this over and over. I mean, look at the camp outbreak in Georgia. So you had kids inside, they were singing, which shouldn’t have happened anyway, no masks. And the CDC investigation says there was no to low ventilation. So same condition right there. Now, that’s a naturally ventilated space, same problem. They just didn’t open the windows or doors. So they had only recirculated air with no filtration at that point. And any time you do that, the risks are higher. And it doesn’t matter if we’re talking about a restaurant, a school, an office building, a preschool, a bus, an airplane, you name it. It’s the conditions that set up the spread, really, what’s more important than whether you have mechanical or natural ventilation. 

MODERATOR: Next question. 

Q: Nice to get a chance to chat with you again. It seems that as we kind of look at school reopening across the country, a large factor kind of beyond what the school boards might do or the superintendents and building changes has to do with comfort of teachers going into the buildings. We see negotiations between the teachers unions and, you know, whether or not they feel comfortable going in. What kind of a message do you have for teachers in this situation? As far as the safety of school buildings? 

JOSEPH ALLEN: Good question. You know, first I’ll say I understand their anxiety and I’m a parent and I have similar feelings about this. But this is where I think it’s really important to get back to the science and see that if those conditions are met, that we talked about low community spread and controls are in place, that the risks are significantly reduced. So there are many stories that are hitting the newspapers of cases. The Georgia camp I mentioned, the Israeli schools, which also, by the way, was a ventilation problem. And mask, problem, no mask. And we see many of these. But the reality is there are a lot of success stories happening that don’t make the news. And it’s similar what we have in science, where we have a publication bias, where no studies never make journals or rarely do. And so there are great stories from this summer. Even in one in Maine of camps that are open many hundreds or thousands of kids and no cases. YMCA stayed open in New York City right through the peak March, April, May, very few, if any, cases. I’ve advised and worked with community child care services, child care services that could not be discontinued, right through the peak in Boston and no cases either. 

So there are success stories out there. We know from health care workers, right? Same thing. If you look at what’s happening in hospitals in particular, to talk to folks who run infectious disease at the hospitals in Boston. And they’re protecting their workforce by doing a couple of things. Universal masking, hand-washing, and hospitals do a really good job with ventilation, filtration. And there, they can’t even physical distance. And it’s a high risk environment where every one or both people arriving or a large percent have COVID an are at peak infectivity. So that’s a little bit of the message that, you know, the strategies we’re talking about and we’ve advocated for are strategies that are designed not just to protect kids. They’re also designed to protect adults. And we have good evidence that this works. And we have good evidence based at this point, many months old by now on these risk reduction strategies that can work. I know, for example, the Mass Teachers Association, and they’re part of a larger group – I can’t remember the name right now – put out a notice yesterday. I think the day before where they actually cited our report and they brought in our Schools for Health Report. So last thing I’ll say is what else for teachers besides that message. That it’s designed to protect kids and adults. And if these are in place, then the risks can be significantly reduced. But we’ve put out many other resources. In addition to this long report, we just put out a guide, five step guide to checking ventilation rates in classrooms. We went out to a couple of schools, measured ventilation rate, even through just opening windows. We took dry ice, built up the carbon dioxide concentrations. You watched the decay curve and you can estimate how many air changes per hour of clean air you get. But we decide to write this up and we have this guide and we simplify it. So it’s technical but doesn’t have to be technical, including, could you use a carbon dioxide sensor to look at the CO2 concentration to get a quick understanding if your classroom is well ventilated or not. I mentioned we have that 20 questions every parent should ask. We have another tool we built for how to select a portable air cleaner for your classroom. To demystify this a bit, we have a technical report on our website, too. But if you don’t want that, there’s a five step, how do you select an air cleaner that sized appropriately for your classroom? So a couple of these strategies are happing mask wearing, you know, distancing. But if you have this couple air changes per hour of either outdoor air or recirculated air going through a good filter or a portable air cleaner with a HEPA filter, you can further drive down risk of your classroom. 

Q: I wonder, just as a follow up and looking at a different level of education with some of the outbreaks that have been seen on college campuses, you get a sense, is there a common theme between some of these smaller outbreaks, whether it is, are they all related to parties and things like that? Or are there things that maybe the universities or physical plant could be doing following your guidelines better? 

JOSEPH ALLEN: Yeah, I think it’s a little early to tell on the university side. And because, you know, for example, in the restaurant, it’s easy to figure out because everything is so controlled, but it’s quite hard to tease out what’s driving some of these. You know, it’s easy to blame and say, well, a group they had a party or something like this. It’s gonna be multifactorial for sure. But certainly these same risk reduction strategies apply it just different because now you have a lot of more kids that are more independent. Shouldn’t call them kids, young adults. They’re out and about off campus. They’re independent. They mix and interact with each other. And there’s a lot more of them on campus than, say, a K-12 school. And then, of course, they’re sleeping together, and I don’t mean I mean they’re sleeping, they’re roommates, right. And sometimes sleeping together. So you have all those factors. It’s hard to parse out and tease out. I think, you know what I really like, Harvard’s doing a really nice job. I’m on a committee at our university working on this for the past couple of months. And it’s really an aggressive testing program where that’s one way to be sure that any case or cases doesn’t explode and turn into an uncontrolled outbreak on a campus because that’s where it gets really tricky. Then where do you put the students that point? You can’t really send them home, I don’t think so. So the testing strategy becomes really critical in the university setting. 

Q: Very good. Thank you. 

JOSEPH ALLEN: Thank you. 

MODERATOR: I got a follow up question, since we don’t have control over how well the HVAC systems are working in schools, apartment buildings or workplace offices, what can we do to lower risks beyond wearing masks and social distancing? 

JOSEPH ALLEN: Yes, thanks for the follow up. I guess first I’d disagree with the premise. I think we have a lot of control over ventilation and most of our buildings. The problem, from my perspective, is that building ventilation systems have been designed to a minimum ventilation standard. There’s none that we don’t have control, in many cases we have a lot of control. We can put in better filters. We can bring in more outdoor air. The issue is that they’ve been designed to a standard that set for energy efficiency, not infectious disease control. I do agree with the premise, though for schools, it’s a bigger challenge because we’ve under invested in our school infrastructure for decades. So it’s quite common to find a unit ventilator in a school. That’s the ventilation system you’re probably familiar with, that’s against the wall. Usually people stack books on them or a fish tank or terrarium that draws in air from outdoors and conditions it. Many times those have not been maintained. I’ll put some numbers on it, at least for schools. The minimum standard is three air changes per hour. Most schools, so the average school in the U.S. gets about half that. Some schools only get one air change per hour, some classrooms.We’re recommending four air changes is good. Five is excellent. Six is ideal. So the idea of what you can do, I mean, one of the ideas with these series of op eds I’ve written since June, is that we’re running out of time and resources. What can you do? And so the one I wrote, I think was the end of July. This is in The Washington Post, really focused on making schools smart. And it was the use of portable air cleaners in every classroom, but they have to filter. Your air handling system needs more time to get up to speed, you can’t put in better filters, use a portable air cleaner, plug and play technology can really work. The latest op ed last week was we’re really short on time here, start opening up windows and we’ve measured this and showed you can get five, six, seven, sometimes over 10 air changes per hour from opening windows and doors. And that was the focus of the most recent op ed. And I just talked about New York City just a little bit ago. That’s what they’re doing right now, right? Going around, propping open windows, cranking them open. A lot of times windows aren’t working. And by the way, I say open windows. Our testing showed that even six inches is sufficient. So you don’t have to open windows with a multistory school, you don’t worry about a fall hazard. You just got to get them open a little bit. In fact, our testing in the schools we tested, some of their windows were broken and we couldn’t open up for the tests. We still found that benefit. So that’s really quite important. I guess the big picture is that there’s always something you can do. And this comes from my doing these forensic investigations and turning sick buildings into healthy buildings. Never came across a school, university, I’ve been on military bases doing this, never came across a sick building that couldn’t be rehabilitated. It just takes a little bit of attention. And you notice that a lot of the all of the recommendations I’m making are relatively affordable. I have not really talked about advanced air cleaning technologies. They exist. It costs more money, more sophisticated. I’m trying to give practical steps that nearly every building can implement right away. 

MODERATOR: All right. Thank you. Next question. 

Q: Can you hear me all right? 


Q: Great. Thank you. I was wondering if you have looked at all at ventilation in TransAm thinking, particularly public transit? I know that’s something that we’ve been talking a lot about schools and that there’ll be many students in cities who may be utilizing public transit as schools reopen, as well as other folks, workers and other people who may be returning to offices and other buildings. So I’m wondering if you’ve looked at that? I’m thinking particularly about public transit busses. Obviously, there are subways as well. Are there any concerns around ventilations in public transit and what should be done about that? 

JOSEPH ALLEN: Good question. My team has not looked at this specifically, so what I know is from reading reports and reading the science, we haven’t put out anything on our own. But what you see is that in terms of subways, New York Times wrote a really nice story a couple weeks ago looking at, breaking down the ventilation systems in the subway. You do get several, many air changes per hour in the subway. So that is a good sign. The issue, of course, is that during rush hour, and I used to live in New York, they’re jam-packed. So I think this is one of the keys here that if we think about it from a, let’s say, a societal level or what companies and schools need to do, the densification of office buildings and the staggered arrival times for school and allowing the workers who can arrive at different times can help the densify. I think it’s going to be a challenge if we start reopening the economy and we say, OK, everybody, Monday morning walked through the front door of your office at 9:00 a.m. and that’s when schools start to because that’s just going to jam public transportation at the same time. So I encourage office building companies to say, well, let’s extend the workday. You can start early, leave early or leave late. So our companies do their part in terms of densifying the public transportation. But if it’s typical occupancy, the ventilation is good, at least on a subway, from what I’ve read. That said, we should absolutely wear a mask. And these are times people should be hyper vigilant. 

That’s the time to make sure your mask is on. Exactly right, over the bridge of your nose, around your chin. Good. Tight fit. Ideally, no talking. I mean, we know when we talk, we emit greater amount of aerosols. So that’s not always possible on a subway. But it’s a really good idea. It’s a good practice or quiet talking anyway. Let’s see what else on the terms of busses. Well, there was a recent report, a bunch of cases on a bus. But it gets back to those fundamental principles. It was a bus with no ventilation, no filtration, and someone was sick, and it was a long bus ride. Our own modeling of school busses, and this would apply to any bus or anything else. You won’t be surprised when we rolled down the windows a little bit. And the bus is moving. 

We got 20 to 40 air changes per hour. Air change per hour to put numbers on it, six air changes per hour is an air change every 10 minutes. The full volume is refreshed, full to the space. So, you know, 20 air changes per hour and you’re getting up to every couple of minutes. So the same principles apply if you want to bring in more outdoor air, if you can. If you’re recirculating the air, it has to go through a better grade filter. We’ve done some modeling. I have an op ed in USA Today on cars. Not that many people are commuting in cars or by Uber taxis. Same thing we showed rolling down the window. Just three inches can significantly reduce the concentration of airborne particles. So to and from work, people have to be hyper vigilant, mask on hand sanitizer, hand washing before you leave that apartment, hand sanitizer as you’re off the bus or subway. I think that’s a good idea. 

MODERATOR: Do you have a follow up question? 

Q: I think I’m set. Thank you very much. 

MODERATOR: Next question. 

Q: Thanks. I was curious if you could kind of highlight what kind of national policy guidance would be good to be provided for schools and businesses? I’ve been kind of looking at like what’s in place by administration versus what could be different if Biden is elected, and just kind of curious what would be an ideal guidance, regardless of who is elected?

JOSEPH ALLEN: Any. All right. So that’s a that’s a smart aleck answer, but really it’s pointing to what I see as being a major problem going back to January is there’s been a lack of leadership and guidance coming from this administration. It’s been confused. It has conflicted with what the best science says. And that’s right from early on through even this week. And the result is that we’re stuck with an ad hoc approach. State by state, we’re trying to figure this out, states were competing for PPA early on. I mean, that’s totally unacceptable. And right now, it’s happening with schools. It’s like state by state they’re trying to figure this out. School district by school district. And so this is not the way it should be done. There’s been a real failure of national leadership that is not following the science, that is minimizing the threat, has not offered a clear and consistent voice in terms of what needs to be done and has actually divided us. That goes right from like I said early on through when we were recommending masks early, I wrote a piece in The Washington Post in early April. 

As soon as it came out, the president undercut it. So now he’s not going to wear a mask. Took many months to turn that around. I think that’s been a consistent problem right from the beginning and remains a problem today. I mean, really, I don’t necessarily think the Healthy Buildings program at Harvard School of Public Health should be the one writing a risk reduction strategy for schools. But we were looking in May. We didn’t see what we liked out there. We thought we would weigh in with what we think is a sound approach to reduce risks in schools and to try and fill that leadership gap. 

MODERATOR: Do you have a follow up question or are you all set? 

Q: No, I’m set. Thank you. 

MODERATOR: Next question. 

Q: Professor, thank you very much for doing this. So I read your op ed about air travel in The Washington Post and it really dispelled a lot of my just kind of immediate knee jerk intuitions about air travel. But I’m wondering, since, you know, on social media reports have been spreading about airlines, not, let’s say, enforcing mask use to the extent that maybe we’d like. And a lot of airlines are no longer keeping the middle seat open. And I was wondering if the fact that, you know, a lot of these reports have been coming out, whether or not you would still recommend or you would still say that air travel has shown itself not to really have been a vector for viral spread at this point. 

JOSEPH ALLEN: Yeah. So thanks for your comment and question there. So one just clarification. Airplanes are excellent, unfortunately, excellent vectors for spread. So I was clear in my piece that that happens, right. They spread people around the globe and country quite effectively, including sick people. The piece is really focused on the risks on the airplane while you’re flying. And yeah, and so for background, I’ve done 10 years of research on air quality in airplanes. I have studied this. In 2013, I was the lead author of the National Academies report on infectious disease mitigation in airports and on airplanes. And when you look at the science, you understand how the environmental control system works on an airplane. You see that the conditions are good in terms of keeping risk low. You have a good ventilation rate delivered to each person, not just general ventilation. You get over 12 air changes per hour. Any air that’s recirculated runs through a HEPA filter. So the way an airplane works, you get bleed air. It’s called bleed air. It’s bled off the engine. Most airplanes, except for maybe the 787, the new 787. So it’s bled off the engine condition, delivered 50 percent mix of clean outdoor air and recirculate air. Anything recirculate. It goes to the filter. So that’s why the airplane has been low risk. 

And if you look at the science across all diseases, you find very few outbreaks. Now, look, you can get sick on an airplane. And there have been high profile examples of this. But compared to the sheer numbers of people that traveled over the past many decades, it’s just not the hotbed of infectivity that people think it is. 

But you do get sick when you travel. The reality is the higher risk parts are probably on your way to the airport in the security queues at the airport many times your changing, your sleep is disrupted, your changing time zones. This impacts your immune system. You arrive at a novel place. You’re sleeping in a hotel, at a friend’s house. You’re in a taxi assembly. It’s all of these things are going to add up. But during that whole routine, the time of the airplane is lower risk than the others. That doesn’t change, now with SARS-CoV-2. But I do think it’s prudent and important that people wear masks when they’re on the airplane. So, yeah, I support policies for universal masking in airplanes. 

Q: Thank you. 

JOSEPH ALLEN: And this is good practice. I’ll say one other thing that was in our 2013 report, that to me is one of the really important areas that I’m not sure has gotten the attention it deserves, but we called it out in that report. First, I’ll say in our report, we said they should have a pandemic preparedness plan. So let’s hope airports and airlines did that. Second, when the plane is at the gate, our own testing with other collaborators has shown that the ventilation systems are not always on. And so that’s a period where there is higher risk. So that’s an absolute period where masks should be worn. You’re walking down the jetway, you get on that airplane. It’s not running. It’s not running its APU, auxiliary power unit, or not connected to gate based ventilation. Sometimes you’re not going to have sufficient airflow inside the airplane until they get moving. 

MODERATOR: OK. Next question. 

Q: So a question for you. You mentioned a couple of times, low community spread. I’m just curious what kind of numbers you’re using for that to define that? 

JOSEPH ALLEN: Yeah. So I defer to our work with colleagues at Harvard Global Health Institute. And we put this out for schools based across a couple of dimensions, including a number of cases, new cases per day, per hundred thousand, hospitalization rates and testing. So I’ll refer you to that report that’s been that’s been out for a few months at Harvard Global Health Institute. 

Q: One other question, you talked a lot about masks. How long do you expect us to to be wearing masks? Just going to go away anytime soon or are we going to be wearing masks for a long time?

JOSEPH ALLEN: I’m not sure you mean, you know, a long time, like years? 

Q: Or is this going to be when a vaccine comes next year? People are getting tired of them already. So I’m just wondering where if you see a day when we’re not going to have to wear them. 

JOSEPH ALLEN: Yeah. I mean, I understand people are getting tired of a lot of things already, but I actually see the opposite. If you look at the polling, you know, there’s widespread support of masking from the public and even those who were recalcitrant early on have turned the corner on this. It’s one of the most effective NPIs, non pharmaceutical interventions, we can have. And you know, people wear masks all day and it’s not the best. But, you know, our health care workers do this day in and day out. So certainly they can expect us to all do the same if we’re not in health care, you know. Do I think it’ll be a permanent fixture in U.S. society like it is in Asia more or less? I don’t know. I think some people have no problem wearing them when they’re going out to the grocery store. This era is certainly ushering in a heightened awareness of infection control. And I suspect some people will still feel more comfortable on the subway wearing a mask, or grocery shopping. And I wouldn’t have a problem. There’s no problem with that. That’s a personal choice. 

Q: Thank you. 

MODERATOR: One more follow up question. Dr. Allen, do you believe the risk of transmitting COVID-19 as a result of inadequate indoor building ventilation has been underestimated? In other words, is there a bigger threat here than most people think? 

JOSEPH ALLEN: Yes. We’ve been shouting from the rooftops about this since early February. There were telltale signs early on that airborne transmission was happening. But I’ve been writing about it personally almost every week since then, in Washington Post, stat news, USA Today, New York Times and even this one yesterday in The Washington Post about bathrooms, talks about ventilation. But if you looked at what CDC and WHO guidance has been saying in that time, they’ve been really reluctant to acknowledge it. And even, you know, I was one of the 239 scientists who signed a letter WHO in July urging them to recognize that all of the scientific evidence supports airborne transmission is happening. 

That is basic aerosol physics. Most of the particles we emit and we talk saying or just breathe, you are 10 microns or smaller. These particles travel beyond six feet and stay aloft for 30 minutes or more. Smaller particles will stay low for hours to air sampling data. We found viral RNA in places that can only be reached through through the air like inducts. Recent testing has found viable viral particles at 16 feet from a patient. In a hospital leak, case, studies all show that ventilation is important. The choir practice in Seattle. The restaurant example, the cruise ship, my own team, we put out a preprint three weeks ago on the cruise ship. We remodeled that. We estimate that airborne transmission is 35 to 40 percent of the transmission on that ship. We have case studies happening, unfortunately, almost every week now that support that hypothesis. So this is definitely been happening. 

But the guidance has been slow to acknowledge this, and I’ve talked to many organizations and I hear this frequently, we hadn’t thought about that until we talk to you that these healthy building strategies have to be part of the arsenal. And look, airborne transmission is nothing to be feared. It just means you have to include another set of controls in the strategies you’re already doing and washing, distancing as best as you can. Universal masking can better ventilation, filtration to open up your windows at home. Open your windows in your car. Use a portable air cleaner where the HEPA filter if you need to in your classroom or your office. So, yeah, and I’d say one thing on airborne transmission because there’s a big under misunderstanding out there too. The dose matters, so distance also matters for airborne transmission. So you can imagine if I’m infectious and we’re talking and you’re three feet away, where you’re going to get a big dose when I talk. If you’re six feet away, it’ll be less if you’re across the room. Sure. Some of those viral particles can reach you, but they would dilute in time and space. And if your building is performing well, meaning you have ventilation or air cleaning, you can decrease the likelihood that particles would reach someone on the other side of the room. Because now you have better additional mechanisms for removal. So the distance matters, right. For airborne transmission to the big point about airborne transmission is that you can be exposed beyond six feet. And these other factors, like ventilation infiltration, can really help because if you put someone who is infectious in a room with other people and you don’t have ventilation or filtration, particle concentrations will accumulate. And they will increase over time until they removed. So the risk for infection is higher in those situations. 

MODERATOR: All right, great. Dr. Allen, do you have any other final thoughts before we go? 

JOSEPH ALLEN: I don’t think so, no, I appreciate the comments and questions. I just pointed to my recent op ed yesterday on toilets. This has not gotten the attention, I don’t think, that it’s deserved. Again, the control strategies are quite simple, so I’ll just point that out. 

This concludes the September 2nd press conference. 

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