#21 - Richard Corsi: Do particulates matter? - The National Academies report and a CR Box

Dr. Richard Corsi

Dean of the College of Engineering at the University of California, Davis. His team has researched indoor source dynamics, indoor chemistry, and innovative and accessible control technologies for reducing exposure to indoor air pollutants.

During his 24 years as a faculty member at the University of Texas at Austin. He was an endowed research chair and member of the Academy of Distinguished Teachers, and served as Director of a National Science Foundation program on Indoor Environmental Science and Engineering that spawned many successful scholars of indoor air science.

Richard's work has been cited in the New York Times, Washington Post, Los Angeles Times, The Economist, Forbes, National Geographic …….

He is a past President of the Academy of Fellows of the International Society of Indoor Air Quality and Climate (ISIAQ) and past President of the society’s signature conference Indoor Air 2011 in Austin, Texas.

He recently chaired a National Academies committee report on Health Risks of Indoor Exposure to Fine Particulate Matter and Practical Mitigation Solutions. A truly multidisciplinary endevour that has produced a state of the science report that is truly phenomenal. And I think is going to be the go to reference  for some time.

I was really keen to talk to Richard about this report, as his overview of the work is a must listen for anybody working in the built environment, and his ability to bring to life a 270 odd page report in plain english is truly a skill.

I was also keen to talk to one of the people behind the Corsi Rosenthal box, the DIY air cleaner that burst into prominence during the pandemic and turned the sector on its head in many ways.

Ive been looking forward to bringing this conversation to you, I hope you enjoy it as much as I did. 

Richard Corsi LinkedIn
Richard Corsi UC Davies
National Academies Report
Corsi-Rosenthal Foundation

Chapters

• 0:15 The Importance of Indoor Air Quality
• 9:43 Understanding Fine Particulate Matter in Buildings
• 18:28 Indoor Air Quality and Human Behavior
• 30:14 Building Impacts on Particulate Exposure
• 47:46 Indoor Air Quality and Health Impacts
• 54:38 Indoor Environmental Factors and Health
• 1:05:16 Indoor Air Quality Report Recommendations
• 1:15:49 Dean of College of Engineering Research
• 1:24:01 DIY Air Filter Invention and Impact
• 1:35:40 Future of DIY Air Cleaners

Transcript

Simon: 0:15

Welcome to Air Quality Matters, and this is a conversation with Richard Corsi, dean of the College of Engineering at the University of California Davis. His team has researched indoor source dynamics, indoor chemistry and innovative and accessible control technologies for reducing exposure to indoor air pollutants. During his 24 years as a faculty member at the University of Texas at Austin, he was an endowed research chair and member of the University of Texas at Austin. He was an endowed research chair and member of the Academy of Distinguished Teachers and served as a director of a National Science Foundation program on indoor environmental science and engineering that spawned many successful scholars of indoor air science. Richard's work has been cited in the New York Times, the Washington Post, the Economist, forbes, national Geographic the list goes on. He's a past president of the Academy of Fellows of the International Society of Indoor Air Quality and Climate, isiac, and past president of the Society's Signature Conference on Indoor Air quality in 2011 in Austin in Texas.

Simon: 1:26

He recently chaired a National Academies Committee report on health risks of indoor exposure to fine particulate matter and practical mitigation solutions, a multidisciplinary endeavour that has produced a state-of-the-science report that is truly phenomenal and, I think, is going to be the go-to reference for some years to come. I was really keen to talk to Richard about this report, as his overview of the work is a must-listen to anybody working in the built environment, and his ability to bring to life a 270-odd-page report in plain english is truly a skill. I was also keen to talk to one of the people behind the causey rosenthal box, the diy air cleaner that burst into prominence during the pandemic and turned the sector on its head in many ways. I've really been looking forward to bringing this conversation to you. I hope you enjoyed as it as much as I did and, as always, thanks for listening. I really mean that this is a conversation with Richard Corsi.

Richard: 2:31

So particulate matter does matter. There are literally decades worth of epidemiological studies on the impacts of increases in particulate matter concentrations outdoors causing population-wide health impacts, and those health impacts vary from respiratory, lung cancer, cardiovascular impacts, reproductive impacts, neurological impacts so there's lots of known impacts of increases in exposure to fine particulate matter measured outdoors. One of the things that's really important for us to understand is, while those concentrations of particulate matter are measured outdoors, most of our exposure to that particulate matter, even of outdoor origin, happens when we're indoors, and so we know that when we're exposed to particles, at least of outdoor origin, and when those levels increase, there are population-wide negative health impacts. So particulate matter really matters and, in fact, if you look at epidemiological data for a lot of the pollutants in the air that we regulate or that we study, particulate matter really has the greatest impact on us when it increases.

Simon: 3:49

We've had on this show as well Ben Jones and Max Sherman, who've been looking at the harm intensities of various pollutants indoors, and particulate matter is the standout in their work as well um in their work as well.

Richard: 4:09

Absolutely, and I think that um, we don't have as much information about the health impacts of particles of indoor origin and specific sources. There is some in the literature, things like incense causing specific types of diseases, of course, secondhand tobacco smoke doing the same, um, but but we still have a much longer ways to go to sort of parse out the relative significance of particles of indoor sources, particularly linking them to the source themselves.

Simon: 4:39

What started the National Academies? Wanting to look at this Because you were involved in this consensus report that was put out this year, weren't you?

Richard: 4:52

Absolutely. Yeah, it was actually the US EPA asked the National Academies to do the study, to do the consensus study. The National Academies responds to government agencies that need more information on certain subjects, and so it was the EPA that initiated the study. National Academies organized the team and was responsible for making sure the study happened and the report came out. The US EPA certainly has been a leader over the decades, at least in the United States, with respect to regulating outdoor air pollution. It doesn't have a mandate to regulate indoor air pollution, but it certainly has motivation to understand where people are being exposed to pollutants of outdoor origin, et cetera and it does have a role in educating the public about indoor air quality. While it cannot mandate or set standards or regulations, it does have a mandate to educate the public about indoor air quality and what people can do to reduce their exposure to harmful pollutants like fine particulate matter that the National Academies does is it assembles scientists and academics for certain subject matters that they feel or other organizations feel need further investigation.

Simon: 6:14

Is that kind of the idea of it?

Richard: 6:17

That's a primary role of the National Academies, that's correct, the National Academies of Science, engineering and Medicine. So they assemble experts and attack problems and put out reports that are clearly intended to be independent, non-biased reports by um, by, you know, experts in the field. They've been doing this for 160 years or so, since the academy was formed in the 1860s well, it must be.

Simon: 6:48

It must be a real privilege to be part of something like that. It kind of struck me as the the academic version of avengers assemble, um, that there's this uh crack team of of academics brought together to solve a world problem which, I guess, kind of makes you the tony stark of the uh the outfit.

Richard: 7:07

Well, no, no, you know, it was a real it was a real honor to chair the committee, but the committee was a committee of all stars right. We had over 10 other people on the committee who were incredibly well known in their fields both outdoor atmospheric aerosol scientists to uh to building scientists, to building scientists, to exposure scientists and also some great health scientists. So it was a really good mix and a cross-disciplinary mix of big names in their field.

Simon: 7:35

Yeah, I think it shows how broad the mix was, that there's some real superstar names on there from areas that I'd understand, but there are names there that I didn't recognize at all, which shows how cross-disciplinary it is that there's people being pulled from sectors that are so far outside my day-to-day exposure to air quality.

Richard: 7:57

Absolutely. And the health science team. There were three people, health scientists. Chapter six, to me, ought to be a critical review that's published in scientific journals, because it really establishes, I think for the first time, the true health impacts of exposure to fine particulate matter in homes and in schools, which was the focus of our study. It's a great chapter.

Simon: 8:26

Yeah, no, no, absolutely, and I think it really shows this new frontier of linking health with air quality. You know it's such an exciting area of research at the minute.

Richard: 8:40

I agree, and I think the indoor air quality field in many ways has suffered from not having a stronger link or studies that show that strong link. And I think we're starting to see that now. I think you know sadly I think the pandemic brought that around that people realize that things they're exposed to indoors can get them infected. And now there's this heightened awareness that gee, other things we're exposed to indoors that may not just necessarily be infectious agents can do harm to us. And I think we're at sort of a pivot point here in the indoor air quality field where there's a lot of public awareness, a lot of company and corporate awareness. Schools are becoming more aware of how important indoor air quality is and what we can do to try to improve indoor air quality so that everybody's healthier right.

Simon: 9:30

Yeah, and I think the more of these kind of deep reports like this that look at one particular area or another, the better, because it really helps pull in a lot of these multidisciplinary links. But perhaps as a kind of a back to basics 101 for people, we talk about particular matter quite a lot on this podcast but we haven't really stopped and paused to talk about what it is, because we tend to talk about particular matter as a single entity, as just dust that floats in the air. Somehow. I think everybody understands the plain English of what a particulate probably is, but we very rarely stop to think about how complex a thing it can be. So perhaps explain a little bit about. When we talk about fine particulate matter, what are we actually talking about?

Richard: 10:26

Yeah, it's a great question. So fine particulate matter are the collection of particles that have a diameter that's less than 2.5 microns, less than or equal to 2.5 microns. And to give you a sense of what that means, the typical cross-section microns. And to give you a sense of what that means, the typical cross section. The diameter of the cross section of a human hair is anywhere from 50 to 120 microns, depending upon how fine or how coarse your hair is. Coarse would be at the higher end and fine would be the lower end. So these are particles that are really tiny particles that we can't see with the naked eye. Sometimes with just the right light and if there's enough of them, we can't see with the naked eye. Sometimes, with just the right light, and if there's enough of them, we can actually see the collection of them, but generally there's no way you can pick out one single particle with the naked eye.

Richard: 11:14

These particles that are less than 2.5 microns, these very small particles, can easily negotiate the airways in our respiratory system and deposit in various parts of the respiratory system, including the deepest part of the lungs, the alveolar region of the lungs, which is a part of the lungs we don't want to scar at all. That's a part of the lungs where gas exchange occurs. That's the place where we get oxygen from air into our blood. It's also a place where we take all of the carbon dioxide that's generated by all the cells in our body and expel it into the lungs that we exhale. So we don't want to be able to expel less carbon dioxide. That's not good for us, and we certainly don't want to reduce the amount of oxygen we get into our bloodstream. So we don't like things depositing and scarring that part of the respiratory system or infectious agents depositing there so that they can cause things like pneumonia.

Simon: 12:06

One of the problems with that part of your lung is it's also the place where chemicals and medicines and other things transition from air into the bloodstream. So so some of the things that particulates are made of are transitioning that mechanism into our bodies and in fact, fine particulate matter has a.

Richard: 12:32

even these very small particles have a distribution of particle sizes that go into the very, very small range of what we call ultra fine particles. Those are particles that are one, one thousandth the diameter of the cross section of a human hair and those particles can actually get through that membrane directly into our bloodstream and can be easily transported to different organs in the body. So ultra fine particles, which is a segment or a section of fine particulate matter, are also really important because of the fact that they can actually be delivered directly to the bloodstream. The other part of the particle equation is the composition of the particles. This is something that varies from source to source of particulate matter.

Richard: 13:15

The types of chemicals that make up the liquid and the solid part of the chemicals is really important. And even when you get into the fine particulate matter range, even for the same source of particles, the chemical composition can change from one end of fine particulate matter, say the higher end of things, close to 2.5 microns, and as you get to smaller and smaller and smaller particles, the composition of those particles changes even from the same source. So there's a lot of complexity here and that chemical composition, as you say, simon, um can affect organs in the body, right um yeah yeah, really, and you.

Simon: 13:57

And it just shows how complex it is. I mean, there's a whole chapter, uh, put aside to particle dynamics in buildings as well. It's not just the complexity of what it is, it's how it moves through a building, how it changes as it moves through the building. I mean it's it's a an enormously complex field, isn't it?

Richard: 14:21

when you actually start breaking it down and trying to understand the if you followed an individual particle right the journey of a particle as it's emitted it, as either it's an outdoor particle that penetrates through a building envelope and becomes part of the indoor mix of particles, or a particle it's emitted from an indoor source, there's all sorts of transformations that happen to it in the air that depend on things like the environmental conditions in the space. What is the relative humidity? What is the temperature? That affects the shrinkage and the growth of particles, depending upon those conditions. The temperature also affects the degree of partitioning of chemicals that are in the air into the particles, so that the chemical composition of the particle is changing as it's suspended in the air and moving through a building, and it may change from one room in a building to another room where there are other sources of gases and chemicals, and so that particle is continuously evolving in a very dynamic way.

Richard: 15:17

Particles can come together and collide with one another and grow into bigger particles.

Richard: 15:22

That changes their dynamics. That changes how effectively they can be removed in a filter. That changes where they deposit on indoor surfaces, even particles that deposit on indoor surfaces. Those surfaces may contain plasticizers and flame retardants that are slowly leaching out of those materials and they tend to concentrate in those particles that are sitting on those surfaces and then those particles get resuspended when somebody walks by or somebody is dusting a countertop or dusting a bookshelf, and those particles then get resuspended with this concentrated plasticizers and flame retardants and it's a really, really complex problem and it's so dynamic and it is so heterogeneous in time, which means that things change rapidly with time in the indoor environment, but also with space from room to room in the same building. I think for people that like complex systems, particles in buildings are complex and it's a very complex system, are complex and it's a very complex system and there's a whole field of researchers who study just complex systems and complex dynamics of all kinds. This is a great example for them to sort of sink their teeth into.

Simon: 16:36

And I think it probably points to how important basic principles are and managing risk, and one of the first things we do in the built environment when we talk in terms of risk is understand the three r's, or the hierarchies of control, and try and understand how we limit those sources from being in the air in the first place. So we have to fundamentally understand, I guess, where these particles come from. We've spoken about the complexity of what's happening to them, but they're coming from all sorts of places both inside and outside the building, aren't they?

Richard: 17:18

Yeah, I mean literally dozens to hundreds of sources of particles that we identify indoors, come, dozens to hundreds of different sources. Particles that we identify indoors come, you know, dozens to hundreds of different sources of the particles that we see that make up this mixture of fine particulate matter indoors. And you mentioned the three R's, right, we always teach our students in our air pollution classes or our indoor air quality classes at the university the three R's, and the first R is remove the source. We need to identify the sources, particularly those sources that are the most detrimental to our health. Right, we need to remove those sources. Right, that's the first step. There's a famous quote by Max von Pettenkofer from 1858, I think where von Pettenkofer says I'm paraphrasing now but if there's a pile of manure in the middle of the room, the solution isn't to increase ventilation, the solution is to remove the pile of manure, right.

Richard: 18:16

So we don't want to get to the point where we're trying to increase ventilation or spend a lot of money on complex engineering controls if we don't have to. That's really the last resort. That's the third R, which is remediate the air. The first two R's really are remove the source, identify it, remove it. And then the second one is if you can't remove it but you can reduce the emissions, reduce the emissions then you go to remediation.

Simon: 18:43

If you failed at the first two, then then you have to remediate the air yeah, yeah, it's similar to the hierarchies of control where you you remove the hazard, substitute it with something less harmful, engineering controls, and you know you're getting down the list of lesser and lesser effective ways of managing risk, all the way to PPE, I suppose. So it's the case of understanding where they're coming from and are there ways of us eliminating and substituting that risk? There's not much we can do about outside air. That's a macro problem that's being sorted out by governments and local authorities and so on. But we can have an impact when we start talking about those pollutants coming in to buildings and also the types of pollutants that we're creating in buildings, can't we?

Richard: 19:40

Absolutely, and we do make a pretty big point in the report I think this is in Chapter 7, that as a recommendation for the future is that, you know, should we really be looking just at PM 2.5 mass? Is there maybe a more effective way of doing the research to understand what sources of particulate matter are emitting particles that are particularly detrimental to human health? And if we focus on removing those sources or removing those particles associated with those sources, you know, would we have a much bigger bang for our buck than just trying to remove everything? And that's an interesting question. I think that hasn't been answered and certainly hasn't been answered and hasn't certainly hasn't been addressed from a research standpoint and that's where that link with health becomes so important in understanding that.

Simon: 20:34

Um, you know, that's what I remember mostly from ben and max's work around the harm intensities of pollutants. It's not that something is present in a space, it's that something is present and it has an impact on us is the important thing and you. It means that you can concentrate the resources that you do have dealing with the things that actually cause us harm. Right, it turns out the particulate matter does appear to cause us a lot of harm, but again, if we can break that down into subsets and go, is it cooking pollutants that are causing harm? Is it bioaerosols that are causing harm? What is it in the space that we need to focus our attention on could, because we never have ultimate resources to fix everything all at once.

Richard: 21:18

So if we can understand where the most risk is, we can prioritize, I guess 100, and and there's one additional complexity to all of this, and that is the occupant that we're trying to protect, because we have populations that are particularly vulnerable children that have asthma, um, adults with copd and and etc.

Richard: 21:42

Right. So so mixing in that part of the equation is also important. That perhaps particulate matter that triggers asthma attacks is, you know, not as significant in a household where nobody has asthma right, but it can be incredibly significant in a household with with a seven year old child or a 10 year old or a six year old child that has asthma right, but it can be incredibly significant in a household with a seven-year-old child or a 10-year-old or a six-year-old child that has asthma. And so we have to account for the human part of all of this is who are we trying to protect from what? And there's certain indoor pollutants, certain sources of indoor particulate matter that we want to protect everybody from, but in other situations there's very specific sources that we want to make sure that people or those with specific conditions and homes are not exposed to our schools, right.

Simon: 22:35

Yeah, absolutely, that's another thing.

Richard: 22:38

And also recognizing that the occupants of buildings play a huge role in the levels of particulate matter in a building.

Richard: 22:46

You know we make decisions on whether we're going to burn candles or burn incense, or whether we're going to turn the exhaust fan on on our range hood when we're cooking, or you know all these types of things.

Richard: 22:58

We make decisions on how we set our thermostats that affect those environmental conditions that affect the dynamics of particles in indoor environments. We make decisions on whether we're going to open a window or not, for better or for worse. It can be for worse if we have bad outdoor air quality and we open the window, but it can be for better if we have good outdoor air quality and we have indoor sources and we want to ventilate more. So the people in buildings do a lot of things that affect the environment and affect what they themselves inhale, and that's that's bringing in the human behavioral element which, quite frankly, has really been missing from the indoor air sciences for forever. Right, we need to, we need to, we need to open our arms to those in the social sciences and human behavioralists that can help us understand all of those things, to kind of optimize buildings for the people that are in those buildings.

Simon: 23:52

Yeah, hallelujah to that, and it was one of the things I was really pleased to see in the mitigation and controls elements of the report. One of the recommendations was partnering much more with community-based organizations that look at things like habits and behavior and culture and so on, because they play such a significant part in outcomes. I was interviewing Priyanka Koltretta from Delhi, who looks at particulate matter in slums and places like that in Delhi and the impact they can have with social science and habits and culture there is phenomenal. You know we run around with our hair on fire here when we see particulate matter up at 60 micrograms per meter cubed, but you know they're cheering when they get it down below three or 400 in a lot of environments there. So impacting the way people cook and the type of fuels they use and some of the things they have around, culture of burning sage and things like that can have enormous impacts on outcomes, absolutely.

Richard: 24:58

And then there's this other issue that sometimes, as environmental scientists or environmental engineers, we don't think about, which is the mental aspects of all of this, is that, you know, burning sage is really cleansing in many ways, psychologically and spiritually, for a lot of people. And you know, I look at it and I say, oh, my goodness, the huge fine particulate matters and ultra fine particles people are being exposed to, and but. But you know, in in some communities it's hard for me to say this, but perhaps there are benefits in some way to to certain communities to being exposed to those bad things, right?

Simon: 25:53

yeah, well, health and well-being go hand in hand, you know, and well-being is a complex thing to to judge and um, yeah, it's a really interesting point and you made me think of something else there which just slipped my mind, but it was around. Yeah, risk is relative, right, I mean that's. You know everybody's perception of risk is different and you know it's human beings we're dealing with and we build buildings for people and we have to be able to communicate risk in a way that's sensitive to culture and habit but also understands that people will take a view. You know, we know that cooking sources are a major source of particular matter. We're not suggesting for a moment that people don't cook in their home. You know, in fact, we encourage that the air quality community would be much better off if everybody just got takeaways in um, but I don't, I don't think the obesity clinics would thank us that's the trade-off, right?

Richard: 26:56

yeah, exactly for sure.

Simon: 26:57

One of the things I thought was really interested in the report, um, particularly when you looked at sources and PM, was that one of the big recommendations out of that section was the need to establish a uniform criteria for the information that you collect and how you assess sources and PM. That seems to be a problem that's generic across the entire air quality community is language and figuring out what will mean the same thing and collecting information in the same way. Was that a real challenge when you were pulling this stuff together? It was looking at literature and reviews and studies and trying to find commonalities in language and how you collect data.

Richard: 27:49

The short answer is yes. So you know, we reviewed for the whole report thousands of papers the committee reviewed and the sections that I wrote were mostly in the sources section, and it was definitely an issue with the sources section. You know, we read dozens of papers on candles, for example, right, and of those dozens of papers there must have been, you know, 25 different methods for measuring particle emissions from candles and trying to distinguish the chemical characteristics of the particle image and 25 different ways of doing it. And sometimes you see studies with similar types of candles giving you completely different results and it's not clear whether that was because candles emit significantly different amounts, even if they're similar types of candles, or it's because the methods that the researchers used were just substantially different from one another. Right, I suspect that the methods had some impact on it, and that's where we have kind of a call for people to come together to do this kind of research and develop standards, particularly for particulate matter emissions, that'll narrow that range a bit, right.

Simon: 29:07

Yeah and I guess some of this is time orientated that the air quality sector is advancing so quickly. Our ability to measure things is improving all of the time. So you know, even with low cost optical sensors, their ability to zone in on more accurate readings is improving year on year on year. More accurate readings is improving year on year on year. You know, you and I were having this conversation even five years ago.

Simon: 29:34

It would be a dramatically different conversation around our ability to measure pm with low-cost sensors as it is today I agree they've improved dramatically and they've, you know, also come down in cost, which is great yeah, um, on the particle dynamics and buildings part of the report, you know, as a built environment person and a kind of at the coalface practitioner, I found that section particularly interesting because it's it's the part that often I'm advising people on how to have an effect on outcomes the understanding how buildings impact. You know how engineering controls impact on particulates. I thought it was really interesting that how much emphasis you put on the fact that the building itself affects a lot of these processes, of these processes, that to me seemed as complex a part as almost any other part of the report in that there's an enormous impact to buildings. I mean clearly, obviously, ventilation and filtration and so on, but even layouts and orientations and volumes and there's all sorts of things going on that impact outcomes when it comes to particulate matter isn't there.

Richard: 30:50

Absolutely so. If we focus on the building, even things like how much surface area is there in a room. I've done a lot of work with public schools. When I was at the University of Texas, schools across the state of Texas and you'd walk into one sixth grade or fifth grade classroom and you'd walk into another one and perhaps the second one was so cluttered with bookshelves and boxes stacked and all sorts of things that you just provide this huge surface area for particles to deposit on.

Richard: 31:19

One might argue that's a good thing because the particles are being removed from the air. But then you have these very dusty surfaces all over the place so that when students come into the classroom and somebody walks on the floor or or, you know, nudges up against a bookshelf or something, you get these sort of clouds of particles coming off the surfaces that are resuspended. So you know geometry, the height of the ceiling, the, the, how the air is mixed in classrooms, the nature of the ventilation systems, where the supply vents are relative to sources, where the return grills are, whether windows can be opened or not in the building these are all building-related factors that affect the transport, the concentrations of particles in buildings, and I could go deeper and deeper and deeper than what I just said. Buildings really have a great impact on levels of pollutants of all kinds. We're talking about particles today, but also of all kinds, even gaseous pollutants, especially those emitted from indoor materials.

Simon: 32:25

And is that where you start to talk about having to adopt a more building, aware epidemiology approach to particulate matter? Is that effectively what you're talking about? That context Cause that seemed like a a really important statement in that document, but it seems like it's something you could almost write another report on is like taking a coming at it from a building perspective.

Richard: 32:55

Yeah and I'm smiling because that was something that the committee, over the year and a half we were working on this, just kept running up against over and over and over Was that we would read these studies on the health impacts of fine particulate matter or on the benefits of certain interventions right, the health benefits of interventions with a portable air cleaner or opening windows, whatever it is right and we would see these differences in studies. Again, just like with the differences I mentioned in sources, we'd see these differences in the health-based studies. What we found, though, is, in almost all of those studies, there was a complete neglect of collecting any metadata related to the building itself, right as simple as ventilation rates in the building, right? Or the geometry of the room, or whether windows were open when the study was being done with portable air cleaners, you know all these kinds of things just missing in the published literature, and so it's very hard, when you're reading papers that have different outcomes from health studies, to understand why, without having that building metadata, which I think would be a key that could open up answers to a lot of reasons as to why, and so a significant call in the report that those that are epidemiologists and health scientists that are doing health-based studies should be working with building scientists on those studies to make sure that all the proper building data are collected when those studies are done. Data are collected when those studies are done and vice versa.

Richard: 34:37

Building scientists need to as we're doing studies and measuring things in the indoor environment need to be working with health scientists. So at the same time, we're collecting health data on the occupants of the building, on the occupants of those buildings. Those two communities just simply have not been speaking historically and we really need to bring them together to get the get to the next level, I think, with respect to knowledge of the impacts of the indoor environment on occupants I'm constantly pulling my hair out when I'm looking at studies on indoor air quality and potential health effects of this or that, and you're screaming at the screen where's the ventilation information?

Simon: 35:12

like how many air changes, a rate were going on there, like what was? Was it filtered, was this is? There's so much contextual information missing that you know, because we know we tend to run buildings to failure so often and often with these studies, all you're doing is measuring the outcomes of poor ventilation and, um, if you don't have that context, it's very difficult to understand why you're seeing one impact or another. Um, I think it's a really it's a really interesting part of it. The other really interesting aspect of it is exposure how we're exposed and the challenges of metrics for exposure Difficult subjects here, aren't they with PMs?

Richard: 36:05

It is a difficult subject, it's gotten a little bit easier in some ways, gotten, you know, a little bit easier in some ways. You know the traditional exposure studies fall into three different categories. One is direct measurements, where somebody is literally wearing a device that's measuring, say, the fine particulate matter they're exposed to throughout the day and, you know, perhaps with a GPS system on it so we know when levels go up at certain locations. Right, so those can be really valuable studies. So that's a direct measurement study. Now, in the old days, with old particle monitoring equipment, people would be wearing backpacks with all this heavy equipment in them and tubes coming around their shoulder into their breathing zone. It was very cumbersome. But, as you just said a few minutes ago, simon, our ability to measure fine particulate matter even with little optical particle counters that are low cost and small now makes doing those kinds of studies much, much easier. As long as you're not interested in composition which if you're going to do composition, you need to really at this point still collect the particles and analyze them. But that's a direct measurement. A second type of study is using biomarkers, usually looking at metabolites in urine of somebody at the end of a day right to see what kinds of chemicals associated with the particles that they might right, to see what kinds of chemicals associated with the particles that they might have been exposed to. We see pesticide metabolites and those kinds of things.

Richard: 37:38

And the third type of study is probably the one with the greatest. Well, it is the one with the greatest uncertainty, and that is modeling, where we try to model what's happening in buildings and we look at a person's time activity patterns and say, well, they were in this place at this time and that place at that time and this place at this time. We try to predict what they were exposed to. I think the very first one, which is the direct measurements, which is more of the gold standard, right, I think that's becoming a bit easier and I think that we'll gain a lot more knowledge just because of geographic positioning information. That's much. All of those things are still difficult and all of them have difficulty in capturing the steep temporal or time gradients that we see throughout a day in terms of the concentrations of particulate matter, especially indoors.

Simon: 38:50

Yeah, that's one of the challenges, isn't it, of particulate matter? It is a very transient pollutant. We talk in terms of thresholds and limits in WHO parlance of very low levels, but that's not really how we're exposed to particulate matter. We're exposed to it mostly through spikes and acute events, aren't we?

Richard: 39:11

Absolutely, and we do know that so many of the sources that we think are important indoors are dominated by ultrafine particles and we haven't gotten to the point yet where these optical particle counters don't capture the ultrafine range. They usually capture particles greater than, maybe around 0.3 microns, if we're lucky, 0.3 microns and up. That's another thing we recommended in the report is that we do better at being able to measure exposures to ultrafine particles.

Simon: 39:44

Yeah, my hope would be. I think, as we move into this era of metadata, where we've not only got think, as we move into this era of metadata where we've not only got, you know, personalized monitoring in a lot of cases, particularly under studies, but we're also starting to capture, building data more frequently, just for other reasons as well, that we can combine data sets together and get a much richer picture than we would have been able to do even a decade ago, where everything was data loggers and people have to go back and collect data. You know, it's all so much more available to us now than it ever has been, right? Yeah, agreed, um, I thought one of the interesting things in exposure was that you did note that there isn't even distribution to exposure, certainly at a population level, that some people are exposed more than others. That's a challenge. That there are at-risk groups by the nature of where they live or their socioeconomic class or their geographic position that's a real challenge, isn't it?

Richard: 40:49

There's definitely some subsets that are really exposed to particulate matters and others, yeah, I mean all, all of the literature, all of you know, everything points to that. Right, there are big arrows pointing to certain communities as being not only more vulnerable but also exposed to much higher levels of fine particulate matter. What was striking to us, however, is, while there, while there's information that points in that direction, definitely not enough research being done and measurement campaigns in vulnerable and marginalized and underserved communities to actually say definitively, yes, they're exposed to two or three or four or five times as much exposure as the general population. Right, we don't have those studies and we pointed that out. But you know, when you think about outdoor air pollution, and we do know that particles of outdoor origin cause, as we said at the beginning, all sorts of health impacts, right, and we do know that particles of outdoor origin cause, as we said at the beginning, all sorts of health impacts, and we do know that our exposure to those particles is dominated by the air we inhale indoors, even of particles of outdoor origin. And many communities live closer to heavy industry, petrochemical industries, concentrated near freeways, concentrated near freeways, where we know transportation related particulate matter can have detrimental effects and much higher levels of those particulate matters outdoors and indoors if you live within 100 meters of a freeway and you know they're just the physical location of certain communities puts them at much higher risk of what they inhale indoors much higher risk of what they inhale indoors, right. And then there are issues with, you know, living in much leakier homes near those communities and so not able to control the air that's coming in so it can be effectively filtered when it's coming into a home. Many living in multifamily units where the units are connected so somebody's smoking or burning incense in the next apartment over and you're being exposed to it. We know that.

Richard: 42:59

The fact that oftentimes we're talking about individuals who live in much smaller housing units and the lower the volume if you have an indoor source, the higher the levels are going to be, sometimes not having functional or even having any exhaust fans on their hoods above the ranges they cook on, having multi-generational families living together, and so during flu season and during COVID, right, there's greater family spread just because of the concentration of individuals in those homes.

Richard: 43:38

So just a whole bunch of stuff there that says that there's certain communities that suffer the ills of fine particulate matter much more than the general population. More than the general population and that was a thread throughout the report, whether it was in the sources section or the building dynamics section, or the exposure section or the health section, and also even on the mitigation section, because many communities simply don't have the resources to purchase a $300 HEPA air cleaner for their home or to purchase MERV 13 filters for their mechanical systems, if they even have one. There's a lot to unpack there, but the main point is that all the arrows point towards there's certain parts of our community that we should really make priorities in terms of research, but also in terms of action to help them yeah, but you know, even though the evidence generally across the population is our exposure to particulate matter is reducing, that's clearly not happening equally to all people.

Simon: 44:49

Um, I forget what's the quote? That the future is already here, but not just. It's just not evenly distributed. Um, yeah, perfect.

Richard: 44:56

You know that's uh, it's a.

Simon: 44:59

It kind of points to a moral imperative to to look after the more vulnerable in society, because it's it's always them that seem to suffer the ills of poor environment. You know, whether that's fuel poverty or energy or air quality, you know there's a trend.

Richard: 45:21

Yeah, and I'm glad you picked that up in the report because that's something that the committee, you know. We were all working in our own sections, reading the literature and coming together and having meetings and sharing and trying to figure out commonalities, and this was one of those. Oh my gosh right, the whole committee felt like we needed to get this point across, that you know, from this point forward, let's focus on the most vulnerable and the most underserved communities and the most underserved communities.

Simon: 46:03

Those are the ones that have the greatest impact on their health and on their livelihood from poor indoor air quality, including fine particulate matter. About understanding the building epidemiology. Why that will be so critical? Because there are also unintended consequences of driving a horse and cart through the way people live in their homes.

Simon: 46:28

I remember speaking to Priyanka. She was working with mothers in homes in the middle class of Delhi that had very poor practices of cooking and were exposed to incredibly high levels of particulate matter in, you know, in the thousands at times, acute exposure levels. But one of the unintended consequences of lifting an entire class out of poverty into the middle class is that they now can air condition their spaces and as they start to air condition their spaces they start to close them off. They're exposed to much less acute particulate matter. But now they're exposed to much less acute particulate matter. But now they're exposed to much higher chronic levels of particulate matter because those homes are more sealed and they're trying to control the environment in them and it was a really good. It really struck home to me that there are in every case there are unintended consequences of moving people out of run risk that you might put them into another and I think that's where the building epidemiology will be so important is got to understand the risk factors so that you can mitigate the consequences downstream good or bad.

Richard: 47:44

Right, yeah, absolutely. In the United States there's a great example of this as sort of this huge population migration to the Southeast, southeastern states in the US, from North to South, and we're talking about new housing, but new housing in really wet areas, close to wetlands, rainy areas, and so you have a lot more people being exposed to damp environments and of all the environments we spend our time in. We spend 54, 56 years of our average life inside of our home and now we're moving mass populations down to areas where there's a lot more dampness and dampness-related illnesses are real, right. So unintended consequence moving people out of older homes in the north, the newer homes in the south, and now suddenly having this, this, this sort of dampness set of illnesses that comes with it how much of the report was and did it get to look at things like mold and mold spores as part of the particulate bio aerosol picture?

Simon: 48:52

because I know it's. I mean, you know we're, I'm in ireland. It's a very damp part of the world as you can imagine, but you know certainly this northern european area that I'm in suffers dreadfully in social and public housing with damp and mold and it is the big question mark really over our air quality science. Are we picking up the risk of mold adequately yet, because it kind of sits in a and it is the big question mark really over our air quality science. Are we picking up the risk of mold adequately yet? Because it kind of sits in a couple of camps there's the PM camp that it kind of contributes to, but also separately in a kind of a bioaerosol camp as well, and it just doesn't seem like we're picking up the true risk of mold. Was that something that you guys were discussing as part of the work, where mold might sit in that picture?

Richard: 49:42

Yeah, so it is not a major part of the report. A lot of mold spores, airborne particles associated with mold, are larger than PM2.5. That's not to say that there isn't a component that's pm 2.5 because, you know, pieces of mold fungi break down and they can break down and dry up into smaller and smaller pieces. But we didn't emphasize it simply because it tended to be in a larger size range than pm 2.5. We do mention bioaerosols in Chapter 3, the short section in Chapter 3 on sources, and there is a little bit in the health section, chapter 6, that deals with fungi and spores and those kinds of things. Fungi and spores and those kinds of things and the health effects on some that have that are triggered by either allergic reactions or or um asthma.

Simon: 50:39

One of the one of the points you did point to in the report was the the the lack of um research in schools as a subset of buildings and particularly from a health impact. We we seem to have an idea that air quality is impacting cognitive function and learning and absenteeism and all sorts of things. It can have a very powerful impact potentially on our children. That was a definite recommendation out of the report, wasn't it that there needs to be much more focus in some of these subsets of the built environment.

Richard: 51:17

Absolutely. It was actually pretty surprising when we sunk our teeth into the literature on how little there was on fine particulate matter in schools and the health effects of fine particulate matter in schools and mitigation of fine particulate matter in schools. That's not to say there hasn't been a lot of research on indoor air quality in schools. It's just that much of that research has been focused on. If we increase ventilation, we get better math scores, we have less absences, we get better reading scores right. Or if we reduce carbon dioxide levels, we get better reading scores right. Or if we reduce carbon dioxide levels, we get all of these things right. But it may be that when we increase ventilation we're reducing some sources of indoor fine particulate matter. That's actually giving us those health benefits.

Richard: 52:06

We don't know that because fine particulate matter just hasn't been the focus of those health and performance types of studies in schools. And so we do make a point that at least the pm 2.5 part of of schools needs to be addressed. Um, you know, the ventilation part and the carbon dioxide part, quite honestly, are relatively easy things to measure, Find particular matters more complicated. And if we get into gases, you know, speciated follow, organic compounds is more complicated. So the school literature is fairly robust, but fairly robust in the simplest of ways and not robust enough in terms of identifying specific pollutants that improve the performance and health of children in schools. And fine particulate matter is definitely something that's lacking. We only found one paper on fine particulate matter that suggested that. You know, lowering fine particulate matter levels in schools did have a cognitive benefit.

Simon: 53:09

Yeah, I think that was. Uh, pavel varchok varkochky was involved in one of those papers, I think that was. There was a fairly recent one, I think last year. That was looking at pm. Yeah, that was, that was very good. Um, I think that's always the problem.

Richard: 53:24

He's very good at what he does and uh, profs to paul, you know we need to make sure paul gets more resources to do more studies, because he's really good. He and his team are really good at what they do.

Simon: 53:34

Yeah, we need to clone more Pavels, basically, um, you'd figure that one out. There's a few people we need to clone more, but Pavel's definitely one of them. Um, and isn't that always the problem with air quality is the confounding factors of outcomes? Um, you know, I think we've got better and better of of finding links, um, but we're never really sure if what we're looking at is a proxy for something else or not, and that's always been the challenge, no more so than with volatile organic compounds. But particulate matter could be another one of those that you know. High particulate matter, as you say, is associated with some other condition, um, of thermal comfort or general sense of air quality, and you know it's a really hard one to unpack that. That's why we need the health people involved more, that we really understand the toxicological and epidemiological impacts and constring it out and stop guessing.

Richard: 54:30

Yeah, I agree, you mentioned thermal comfort. That's another issue that's wrapped into all of this. It's so fascinating.

Richard: 54:38

My team and my colleagues and I did a study, a big study in Texas six or seven, eight years ago, of high schools and we looked at all these factors that affected people's perceptions of their indoor environments.

Richard: 54:51

And we looked at all these factors that affected people's perceptions of their indoor environments and it turned out it really didn't matter what the CO2 levels were or the particle levels were or the VOC levels were, and we did look at even speciated volorganic compounds, right, the one thing that correlated with perceptions of the indoor environment as being good, neutral or bad was thermal comfort.

Richard: 55:15

People respond to the temperatures of the room that they're in and it was pretty shocking how strong that correlation was with people's perception of the quality of their indoor environment. And all of the other parameters didn't really correlate at all. Right, we didn't see high particulate matter levels or high VOC levels correlating with people's perceptions of the indoor environment. It was thermal comfort. So, from an occupant standpoint, back to that occupant standpoint right is that occupants are who we care about in buildings and they tend to react in ways that relates to their perceptions of the indoor environment, and if thermal comfort is what causes them to react, they may react in such a way that they change the indoor environment that may actually expose them to higher levels of harmful pollutants.

Simon: 56:12

Because at least they're feeling a little bit cooler, a little bit warmer right they're, they're feeling more comfortable, and understanding that behavior is is so important as we move forward and I think we understand that quite well, with that risk of conditioning of spaces where we the perception of clean, fresh air is driven by the temperature of that air and actually is exacerbating other things like relative humidity in the space, our vulnerability to various bioaerosols. You know, it's a. It's a really complex intertwinement of different factors and one of the things that fascinates me about thermal comfort is there's a. You don't really class it as a pollutant, but it clearly has impacts on people's performance and and other things. But we talk about people's ability to adapt to temperatures, whereas you can't adapt to something that has a toxicological impact on you necessarily right so so some things we can tolerate.

Simon: 57:16

Better than you know. People can tolerate very high levels of co2 if they're trained to. Isn't necessarily going to cause them harm, um, but there are pollutants that we you cut. There isn't a threshold for you, just there's a zero. You don't want any of it in the space, and that's the thing I think we've got to find out about particulate matter. Is just goes back to earlier in your conversation.

Simon: 57:40

When we break down particulate matter, what do we actually really care about? What do we want zero of in a space and what can we? You know sea salt. If you live by the sea, you're going to be exposed to all sorts of particulate matter. Not necessarily going to be that harmful, although I saw a report out in the Guardian one of our papers over in this part of the world the other day showing that people who lived near the sea were exposed to higher levels of the plastics that were being aerosolized into the air through the sea salt. So they found much higher levels of microplastics and some of the forever chemicals because they float to the surface and they're being aerosolized into the air as the water breaks on the ocean. So yeah, anyway yeah, amazing.

Richard: 58:27

And also, um yeah, and kim prather at u at UC San Diego has been doing fascinating research her team just amazing research also on bacteria from sewage outfalls, aerosolizing from ocean spray and coming onto land and so people are exposed through aerosolization of crashing waves to stuff that's in sewage right.

Simon: 58:57

That's the stuff of nightmares. Talk about going, talk about going, living near the coast to get the sea. Air brings a whole new context to it, doesn't it?

Richard: 59:05

Yeah.

Simon: 59:06

Yeah, typical scientists, we ruin everything for people.

Richard: 59:16

I remember when Kim started doing her research some know, many years ago. I mean there was a big focus on surfers and san diego is a big surfer place, right, and surfers being exposed to really high concentrations of bacteria from sewage outfalls and it causes kind of uproar and concern amongst the surf community, which was really fascinating to see.

Simon: 59:34

Yeah, no, really interesting. So I mean, the report isn't all doom and gloom. What I thought was really interesting about it was it's a very practical report in the sense that it talks about very meaningful mitigation and control, and I think the perception that I got from this was that, yes, this is complex, but we do understand this well enough to know that this yes, there's enough evidence to say this is really important and we should care, but there are also very practical mitigation methods that we can put into place to impact our health. That was a really good part of the report. I think that this wasn't just a look. This is the problem, and the usual requires further research outcomes that actually we do know how to do some stuff here.

Richard: 1:00:32

Absolutely, and it's always refreshing to me when you get 11 academics together that are used to doing lots of research and tuned into research to actually conclude, maybe we don't need a whole lot more research in this area. We already have the tools available to us to dramatically reduce our exposure, to find particulate matter. If there's any research that's needed, it's going to be much more sort of practical, nuanced nibbling around the edges to improve technologies that we already have, as opposed to spending tens of millions of dollars in developing new technologies and new control devices. I found that very refreshing actually, as an academic who spent my career thinking about research, that we came together and said you know, this is an area where we really don't need that much more research. We know what to do, and this is, I think, where the human behavior part comes into things.

Richard: 1:01:24

Really is that how do we get people to understand what they need to do to reduce their exposure, get people to understand what they need to do to reduce their exposure and, once they understand, actually get them to follow through and do the things that will improve the quality of life for them and their children, or for schools to do the right things to improve the health and the performance of children in schools. Right, we have it, we know what to do and there's plenty of published literature on the benefits of improved filtration. In the right circumstances the benefit of increased ventilation, certainly during wildfire season or really extraordinary situations or during the middle of a bad pandemic we know that personal protective equipment is highly protective. Right, so we have everything we need. It's just a matter of utilizing it and getting people to use it correctly.

Simon: 1:02:23

Yeah, and I often say this as complex as air science is, ultimately it always falls down to what levers do we actually have at our disposal to pull in the built environment, to affect an outcome, and and effectively? You talk about four levers and that is the basic source control, good ventilation, filtration and possibly some PPE. I would add to that administrative controls, ie education and habit and social science, and that's probably the more complex of the levers. Ironically, but we understand how to remove a lot of the primary pollutant sources from our building. The electrification of buildings through sustainability is removing a lot of combustion products from the home. Increasing in increases in standards and regulation and policing and control is improving ventilation. We know filtration works in spaces. That's a an old science, now engineering practice. At this stage. We know it's very effective at removing particulate matter.

Simon: 1:03:37

Worst case scenario we've always got a ppe mask but it really does come down to those fundamentals, ultimately, doesn't it, and nothing more really it does.

Richard: 1:03:46

it boils down to that. I want to mention one more time that there is a swath of communities in our populations that don't have the benefits of those things and cannot afford those things. Right, it's those that are fortunate, as myself and, I assume, yourself, simon, you know, we can go out and do those things, we can purchase those things, we can retrofit the homes we're in to make them healthier for ourselves, but that's not true for everybody, and that's another point. Getting back to that thread of needing to help and focus on underserved communities, economically disadvantaged communities, this is an area where, yes, we know what to do, but unfortunately, some people don't have access to those things that we need to do and your findings around mitigation and control, found pretty much overwhelming literature when it came to filtration, but not a lot with the other stuff.

Simon: 1:04:55

I mean, there's significant amounts of research, I guess driven by industry that has made these products, but there's a lot of literature on filtration and its impacts isn't there.

Richard: 1:05:09

But I think we need to focus more on some of the other there is. We did with chapter seven was a decision was made. The team came together there's so much literature on mitigation of indoor air quality. The team came together and said, look, we have a ton of literature that says we can do these things and find particular matter levels will be much lower inside buildings. Let's focus on that subset of papers that deal specifically with interventions that had a, that had a health component to the research study.

Richard: 1:05:47

And so all those studies that didn't deal with measuring health but just dealt with measuring lowering of levels of particulate matter were not included in the report. Right, there was a couple of sentences that said there's an overwhelming amount of information that says we can lower fine particulate matter levels in buildings. We believe as a consensus committee that that would have a dramatic, that would cause dramatic improvements in health. But we're gonna focus just on the studies that actually measured health outcomes. Right, and of that subset of the studies, those studies dealing with filtration dominated the literature, and not just filtration, but portable air cleaners dominated the literature.

Simon: 1:06:33

And is that just a hangover of the three years we've been through, or is that just driven by something else?

Richard: 1:06:41

No, I think most of the literature is driven by um the use of portable air cleaners to um improve conditions and in homes, that where you have children with asthma I mean asthma was sort of the dominant health metric for those kinds of studies oh interesting, I mean what?

Simon: 1:06:59

one of the one of the conclusions you came to, though, was that there's no silver bullet here, that the solution there there isn't one solution, that that solves all ills. This is a building by building, scenario by scenario, problem to solve absolutely.

Richard: 1:07:18

Uh, there is no silver bullet, it's it's. It's not right to just say we need to dramatically increase ventilation in all buildings, right? Well, that's not necessarily the solution. If you're near a major outdoorway, if there's wildfires outside or agricultural activities with lots of combustion sources in fields near your home, that's not necessarily the right solution. The solution is going to depend upon the building, but also the conditions around the building and the conditions in the building.

Simon: 1:07:58

This must have taken up quite a considerable part of your life in the last um few years. I don't know when you finished working on it, but you certainly are doing the tour at the moment talking about it. Um, I mean, it's a phenomenal piece of work. I mean I you know I'll share a link in the, the podcast notes, but I do encourage people to go and read it. Even if you just read the, it's not the abstract, is it? There's a summary, basically at the beginning that I think just really one of the most concise summaries actually I've read that just talks about the state of the science at the moment when it comes to particulate matter. Even if you just read that, I think most people be in a better place than they are today. Um, are you kind of glad to see the back of this now? Was it? Was it uh, was it a chore towards the end? Because consensus reports um, consensus anything are generally a nightmare yeah, absolutely we were.

Richard: 1:09:00

I was fortunate that the committee worked really well together and there were certainly areas where we had to come together and come to agreement on how we were going to do something or their differences of opinions, but we sort of talked it through. I would say, um, if you look at the, the members of the committee, these are all incredibly busy, incredibly successful people with a thousand other things going on and in the background we were, all you know, for a better part of two years right A year and a half plus. In the background we were just kept working on this and coming together. We physically met one time on the West Coast of the United States and all got together for several days and kind of hammered out a lot of things and then we went back home. We had frequent Zoom meetings during this year now, but we all feel like family now, I think, and, yes, it's nice to have it behind us now.

Richard: 1:09:54

I think it's a report that benefits mostly because I think it's a report that people benefit from. I think the last 10% of the report was probably the hardest to kind of get across the finish line and get the report in the shape that we all felt really proud of. At times it felt like we were running in slow motion with a bear running after us that was running in fast motion just trying to. We've got to get this done, but I think we're all really really proud of it.

Simon: 1:10:21

um yeah, do you think we could learn something from this report beyond particular matter, that there's an approach here that was taken that could be applied to other areas of indoor environmental quality? It seems to me that it was a great multidisciplinary endeavor that produces a body of work that's useful. I get the sense that that could be an interesting thing to apply to volatile organic compounds, say, or some other area of air quality, other area of air quality that you know. When we look at the hierarchy of the things that are causing us harm, like formaldehyde and nitrogen, nitrogen, dark sides and radon and other things, you do wonder if this kind of an approach would have value in other fields.

Richard: 1:11:14

Yeah, I think the number one thing was that the committee was made up of. It was a truly multidisciplinary committee. We had aerosol scientists, building scientists, exposure scientists, health scientists, many of whom, when we got started, didn't know each other and had never heard each other's names. And, because we work in very different fields, certainly there were people on the committee that knew each other for a long time, but there were many who had never met right, and by the end of this study, we all understood each other better. I learned a lot more about health from the health scientists that were on the committee and I feel like I gained personally from that, from working with them, and I think our field can definitely benefit by pulling together people from different disciplines to work together in a really robust, meaningful way, not to get together for a one-hour meeting occasionally, right. This was almost like living in the same home with the committee for two years and it was a really great experience.

Richard: 1:12:20

And I think that the multidisciplinary nature of the committee made the report what it is. Had we just had building scientists or just health scientists, it wouldn't have been what it was. It really took all those pieces coming together. It's like cooking a nice pie. Right, there's more than one ingredient that goes into a pie, and so we had all the right ingredients there, and we're really dedicated to the outcome. The other thing I think we're all proud of is that you know these reports are intended to be non-biased reports. Right, and we set your biases aside. This is based upon what we know in the literature and what we can say in the literature, and not something that is an agenda that we want to try to get across, so that was also something that I'm really proud of.

Simon: 1:13:09

Yeah, really interesting. And if you could I mean if Richard Corzai was in charge of the national purse strings and budgets, of the national purse strings and budgets If you could take one thing away from this report what would you like to see taken on board and gone at with gusto to do?

Richard: 1:13:32

Well, I will say and I get in trouble by saying this in the United States, but in the US, the indoor air quality field as a whole has always struggled with finding the funding to do the right thing. And so, you know, nih has funded studies involving health scientists and epidemiologists without many building scientists at all in those studies, right, and other agencies have focused on let's hire people that can measure indoor air quality without bringing any health scientists on board. And so this coming together of connecting the dots between what people are exposed to indoors and the health implications of that has never really it hasn't happened. Right, and we need that to happen. And that was one of the major recommendations of this report is that there needs to be kind of a unified effort at the federal level in the US and I think this is true for all countries, right, but at the federal level, perhaps, and working with states and working with nonprofits and professional organizations like ASHRAE, et cetera. But we need a unified effort.

Richard: 1:14:53

This fragmented effort hasn't been working for us and it's been detrimental to actually identifying ways where we can make buildings healthier and because we spend so much time in buildings, our population health improved, right, so we need that that was. That was one another another big one, if I held the first rings. Besides bringing people together at larger studies with with that are more multidisciplinary, is is really focusing on, um, on economically disadvantaged communities, and making those the you know, the focus of our, of our efforts moving forward right those that don't have the resources to to make their own lives, um, um, more healthy yeah those are the two things here here to that, that's for sure.

Simon: 1:15:46

So so you're back to your day job now. Um, I am explain what that is for listeners.

Richard: 1:15:53

Uh, you're dean of I'm I'm the dean of the college of engineering at the university california davis. Um, I'm, I'm. It's an honor and a pleasure to be the dean of the College of Engineering at the University of California Davis. It's an honor and a pleasure to be the Dean of this college because I'm a graduate of this college. I did all of my graduate work in the College of Engineering at University of California Davis in the 1980s and so a long time ago returned after about a 34, 35 year journey in academia, and now I oversee the whole college.

Richard: 1:16:23

So we have eight departments. Um, we have uh, we're a very research focused faculty. Our faculty expend close to $700,000 per year in research per faculty member, which is, um puts us kind of in in in a good place amongst our, amongst our peers in the US, and it's a college that's rooted in a history of, I would say, sustainability. It's a big part of our ethos, it's a big part of the ethos of the University of California Davis. So it's really good to be back. It's not an easy job being a dean, as you know, in academia there's all sorts of challenges these days and so sometimes I don't get much sleep, but despite that, it's an incredibly fulfilling place to be for me right now, at this point in my career and my life fulfilling place to be for me right now, at this point in my career, in my life, and are you directing some research at the moment?

Simon: 1:17:26

that's getting you excited. That's pushing your buttons. What's the uh? What's getting you jumping out of bed on a monday morning at the moment?

Richard: 1:17:35

yeah, so deans don't don't have a lot of time to build research programs because we're we're dealing with so many other issues all around us and sort of crises that happen in the moment when we get to work right. And so I've always loved even though I've worked with lots of PhD students and other graduate students I've always loved working with undergraduate students, and so I've hired two undergraduate students on my research team. There's a wonderful research staff member that I've connected with, named Teresa Pistachini, and she's at the Western Cooling and Efficiency Center, and so she's on a day to day basis. She's the person really guiding the undergraduate students, but I'm providing their funding and I get together with them on a weekly basis and try to guide the research. So we're doing some really interesting studies on Corsi-Rosenthal boxes or CR boxes. We're doing a really neat study right now where we've got boxes in different locations on campus, some of which are really filthy locations. There's soils labs where there's particles all over the place. Some are just in offices, like the dean's office suite that I'm in and some other locations on campus, and we're measuring their effectiveness over time. So we measure the clean air delivery rate, the single pass removal efficiency through the filters. We measure noise, we measure power draw, we measure a bunch of things every about 700 hours of usage, of actual usage when these things are turned on, and that's a really neat study. So we'll be presenting the results of that study at Indoor Air 2024 in Honolulu to show A that they all continue to perform very, very well for a period of time that would be equivalent to about 1.5 or more school years If you assumed eight hours a day, five days a week for eight or nine months a year. So that's really satisfying.

Richard: 1:19:36

But we also see some degradation in the performance over time flying. But we also see some degradation in the performance over time. Right Even we see degradation performance but the performance is still good. It's gone from great, I'd say, to kind of good right over that period of time and we've identified why. So it's not because of less flow, because the fan is becoming burdened because of the pressure drop as we collect particles on the filters. It's really that the single pass removal efficiency not because of less flow, because the fan is becoming burdened because of the pressure drop as we collect particles on the filters it's really that the single pass removal efficiency decreases over time and likely because the electrostatic attraction associated with electrostatic filters is or you know, filters that are initially charged is decaying over time, so that mechanism for removal of particles is no longer significant, right? So it's all the other mechanisms for moving of particles and filters that are still doing the job, but the electrostatic attraction part isn't.

Richard: 1:20:33

And then another study which is really interesting that a student has just started is we've got this array of carbon dioxide analyzers and we're setting up a sort of human breathing, fake human breathing mechanism sitting across the table from one another and there's an array of CO2 analyzers between one person and another person sitting across the table and we're putting CR boxes in different arrangements around the room to see how the tremendous increase in mixing that these boxes cause in a room, how that affects the dispersion of a respiratory plume between an infector and somebody sitting across the table from them, and that's. We've just finished the first set of practice experiments and they look really, really good. So that addition of power or turbulent kinetic energy that causes greater mixing in room air from one of these CR boxes does, I think, have likely we'll see some benefit in terms of rapid dispersion of a respiratory plume between an infector and another individual in the space that they're talking to or eating across from.

Simon: 1:21:48

So kind of getting back into particle dynamics again and all of that good stuff. I imagine that's really interesting. I suppose we should back up a little bit for anybody that hasn't made the connection yet. You're world famous well, in our sphere anyway for the Corsi-Rosenthal box. So Richard Corsi and Jim Rosenthal somehow between you were associated with this DIY filter box arrangement that I think there's not many corners of the world that probably don't know what a CR box is at the moment if they've been looking at filtering cost effectively a space. I'd love to know that story like how did you, how did that come about? What was the birth of the CR box, if you like?

Richard: 1:22:47

Yeah, so it was in the summer of 2020. I was the dean at another university there, portland State University up in Portland, oregon, and the university closed down because of COVID. We had no idea when things were going to open back up. I think for psychological reasons, I was going for really long walks every evening in Portland. When I say long walks, I mean some of these walks were seven miles, right, just several hour walks. And my mind was continuously grinding during these walks on lots of issues, mostly related to the pandemic, as it affected so many people in so many ways, and one of the things that was obvious to me was that there was a big swath of the United States, of Americans, who didn't have the ability to help themselves. They didn't have live. I mean, so many Americans live paycheck to paycheck and they, you know, ask to many it's 300 bucks for a HEPA air cleaner no big deal, but to many it is a big deal, right. And so just started thinking about what can we do to help people. The first focus was on education, so I was developing these models that could allow people to see what they could do by saying if I had a portable air cleaner and I had this clean air delivery rate, this is how much my levels of exposure to respiratory aerosol particles would decrease, et cetera. Right, and I teamed up with a team at the University of Oregon. We put a really nice user interface on that. They did a great job. I'm not a user interface guy, I don't know how to do those things, but I know all the math behind it. And we put out this program called Safe Air Spaces for really intended for schools to use, to play around with, as you say, these levers that can be used to lower inhalation dose of respiratory aerosol particles.

Richard: 1:24:45

And then I kept thinking on my walks about what else can we do, right? And this idea came about of what if we create it? What if people had the power to create their own air cleaner? At that point I really hadn't thought about what that air cleaner would look like, right, but I was thinking about it. And then, point, I really hadn't thought about what that air cleaner would look like, right, but I was thinking about it. And then one night I came home and, just on a piece of engineering paper, started sketching out well, what if we had filters in parallel so that we reduce the pressure drop, and we had a box fan that could blow air through those filters or suck air through those filters, right, sort of thinking about that would be a bad arrangement because it would be like this big plenum of filters you would need in your house. And so I started to think well, what if they were arranged in parallel but as a box and the filters were actually the walls of the air cleaner, and I didn't had no idea at that point the volume of air that could be moved by a $20 box fan. And so, like most people, I went online and I started looking at box fans for sale online Amazoncom, et cetera and realizing, oh my God, the amount of air these things move is five, six, seven, eight times the air that moves through a HEPA air cleaner that costs $300. If we could move that much air and actually filter reasonably efficiently even less single pass removal efficiency than a HEPA air cleaner right, we could still remove more particles than a HEPA air cleaner. And that's how the kind of idea came about.

Richard: 1:26:21

And then started looking at the size of particles associated with respiratory aerosols and as more information was coming out, sort of where the viral you know where the virus has tended to be concentrated, in those sizes. It turned out MERV 13 filters could do a pretty good job of removing the particles that seem to be the sizes that conveyed a lot of viruses that came out of our respiratory system. So it was kind of just MERV 13 it is and sort of threw that idea out there on social media I don't even remember the sequence now of social media or an interview with Wired Magazine. I think it was Jim Rosenthal. So that's my part of the story. Right, I didn't build one and I just threw the idea out there. People could build this for pretty cheap. I think I costed it out and it would be $60 or $70, something like that in the US US dollars or $70, something like that in the US US dollars.

Richard: 1:27:27

And Jim Rosenthal, who I knew when I was at the University of Texas for almost 25 years. Jim had a series of stores that sold air cleaners and I was always impressed with his store in Austin because he didn't sell the air cleaners that many of us don't like. That are additive air cleaners that add things to the air. He was really focused on filter-based air cleaners and I met him through that, through the fact that he had a store in Austin even though he lived in the Dallas-Fort Worth area, and got to know him and over time Jim became very interested in my research and very interested in my research and very interested in the research that my colleagues at the University of Texas were doing. We had a pretty big indoor air quality team and he would from time to time when we needed filters for things, he would give us filters and he would give us whatever we wanted. It was a really good relationship, but always interested in the research and always trying to figure out how our research could help improve indoor environments.

Richard: 1:28:28

And so I think it was the very next day after I kind of threw out this idea, jim tweeted a picture of this box that he had built, based on what I said, and it was this beautiful looking box, like something you would buy off the shelf. That was really nice looking and he said here's a Corsi box. And then I emailed him, or maybe I responded to his tweet, and said you built it, it's a Rosenthal box, and this kind of went on for a couple of weeks as to what to call it. And then Don Milton, who's a very famous airborne infectious disease researcher at University of Maryland, he got excited about this and he said, damn it, just call it a Corsi-Rosenthal box and be done with it. So that's how the name stuck. It really came from Don Milton and it's a bit of embarrassing. So normally when I talk about it now I'll just say CR box or DIY box.

Richard: 1:29:21

I don't really feel like I did much.

Richard: 1:29:22

It was scribbling on a piece of paper and just kind of throwing out the idea.

Richard: 1:29:27

But it certainly has caught on. This thing has probably been, I don't know. I said one time I've spent a lot of taxpayers' money during my career. I've done a lot of research, I've published a lot of papers, like many academics do. None of the things that I've done up to this point has had the impact of this couple of hours of scribbling on a piece of paper and throwing out an idea one night.

Richard: 1:30:05

It was. It's just. It's kind of unbelievable in many ways, but it's so satisfying. And perhaps the most satisfying thing to me as being an educator is when I hear of children in classrooms building them and getting the experience of starting to understand indoor air quality and what a particle is and what a filter is and how filters work. And I hear from teachers that when the students build them and then they switch them on and they feel the air blowing out, um, that the students get really excited that they've done something, and, and when you see pictures of fourth graders and fifth graders doing this, um, it's really, really satisfying to me there's nothing better than seeing citizen science, particularly at a kid's level, where you see them engaging practically.

Simon: 1:30:48

And air quality is phenomenal for kids because it has chemistry and physics and engineering and you know social science and it brings to life so much of what they learn. It's amazing and I was listening to you talk there and it's amazing with the view of the power of hindsight that we're talking about how effective this filter has been. But if we cast our mind back to that period of time, you know how effective this filter has been. But if we cast our mind back to that period of time, we were still trying to figure out what type of filter was. You know what kind of aerosol we were dealing with and and how that risk was associated to infection. And I remember back at the time lots of conversations about was it going to be merv 13 or was it going to be a hepa class filter? Like, where did the line sit? Was it single pass? Was it multi to be MERV 13 or was it going to be a HEPA class filter? Like, where did the line sit? Was it single pass? Was it multi-pass? That was important. It's brought enormous benefit to CRBox, but it's also caused an awful lot of arguments, you know I ended up ringing Jim Rosenthal up. We had both because I was part of the Irish advisory group during the pandemic around ventilation, and a friend of mine, kath Noakes, who was part of the SAGE, the UK group. We came together and I said, look, we've got to have a chat with Jim about this, because we were getting enormous pressure from industry about whether something should be an iso standard, filter standard, or whether it should be hepa class or what you know, what you know.

Simon: 1:32:26

Governments were looking to mandate and specify filter filters and air cleaners for schools nationally. It became a really hot topic for about six to nine months and I was right in the middle of that whirlwind and all the time you had this diy product proliferating across the industry, tearing up the rule book about how you deploy something. How do how do you, how do you specify something at scale nationally that people can make in their shed? Was it c marked? Was there going to be fire safety risks? Right, what about? You know? What about touching it and infection? You know it was. It was an incredible period of time really, but what's been really interesting out the other side of this is as the evidence has started to become available on the effectiveness of this product. Quite how effective it turned out to be, both from a CADR, from a clean air delivery rate, but also from a reduction of particulate levels in a space. I mean it's you know. It's turned out to be an amazing product from a box fan.

Simon: 1:33:41

You know it's turned out to be an amazing product from a box fan and I still don't even really understand what the box fan was ever for before the cr box. To be honest, I yeah. Was it something that people stuck in windows to bring fresh? What was the box fan actually for before the cr box? Because we know that was the big problem we had in europe nobody could get a hold of the box fan. We kept hearing about it in the states yeah and people had terrible trouble getting.

Simon: 1:34:01

So people started using pc fans, all sorts of things. There were big arrays of 30 pc fans being used.

Richard: 1:34:09

You know all sorts of things yeah, I mean yes, um, and there was this other connection. For me personally that was really interesting was, you know, when I was contacted, I was still in Portland and I was contacted by the search committee at UC Davis about the dean's position here and that was in spring of 2021. And I didn't even know UC Davis had an open dean position. I wasn't looking and I probably would have said no to any other university but UC Davis, because I had this strong connection and my wife and I we moved to Davis two weeks after we were married to start graduate school. I mean, it's like coming home, right, I show up here. I had no idea that there was a research team at UC Davis doing really important work on Corsi-Rosenthal boxes, right, and so I showed up and they said, hey, dean, you know this, got your name associated with it, you want to be part of this study. They were 75% of the way done with the study when I showed up and I was able to make a couple of small contributions. But that was the first study, the first academic or research study published on how effective these could be, and it was at UC Davis and it was really neat to just kind of fall into the middle of that accidentally right. That was really satisfying, satisfying.

Richard: 1:35:40

I want to go back to something else you said. You mentioned you'd work with kath noaks and I know kath very well and kath, to me, is one of my heroes during the pandemic of the pandemic. She's done such important work and has been such an important voice. Um remarkable person. So glad you've been working with calf yeah, I love calf.

Simon: 1:36:01

She's brilliant I. I first came across calf a couple of years before the pandemic, and she was the strange bio aerosol lady that turned up at air quality conferences. Um and boy did she burst into prominence during that period and quite rightly got a obe for it as well. And, most importantly, you got to appear on the BBC's Christmas lectures, which was I don't know if you yeah, if you grew up in England before the internet, as I did.

Simon: 1:36:33

One of the highlights if you're into science was the Christmas lectures, which were a series of live lectures at the BBC every Christmas, talking about something or other space or engineering or something. And Kath was the same. She grew up on the Christmas lectures, so she got to be a presenter on the Christmas lectures. That was all about COVID, which I thought was brilliant.

Richard: 1:36:57

That's fantastic.

Simon: 1:36:59

What do you think the future of the cr boxes I mean we've spoken about this before, that you've got this spectrum and you kind of noted in the report, to bring it full circle is that there's lots of innovation potential for technology, particularly when it comes to cleaning air. We see standards like ASHRAE 241 starting to talk about equivalent air change rates and this concept that it isn't just about outdoor air, it's about what we do with air in a building as well. There's this huge room for innovation and you've got this spectrum from one end of the scale with approaches that would have filters and uv and ionization and a whole load of things at a very expensive end of the scale for an air cleaner, all the way to the other at a diy cr box. As you pointed out, there's overwhelming evidence that filtration has a dramatic impact on particulate matter in spaces. So clearly filtering has a place.

Simon: 1:38:08

Where do you think that needle will fall? Because I can't imagine you think that the solution is DIY products in every space or DIY products everywhere. It must be somewhere on that spectrum up from there. But what the CR box has demonstrated is it doesn't necessarily need to be at the other end of the spectrum to have a really big impact. So when you imagine classrooms across the country having the ability to filter a space because realistically they're not going to get round to fixing hevac systems at a scale quickly enough, right right that there's going to be an intermediary measure needed out there, built in vibe, not just in schools but in all sorts of parts of the built environment, where do you think that needle will fall when it comes to this type of approach?

Richard: 1:39:05

well. I hope that people realize, moving forward, that media-based filtration is the solution, is one of is amongst air cleaners, is the way to go right. That is the gold standard in my mind and it works, and there's tons of research to show that it works in general, right, whether it's HEPO or whether it's something else. I think the thing about the CR box that's been so fascinating to me is that I do think there's a psychological element to this as well, that there's something about the empowerment of being able to make something that cleans your own air as opposed to dishing out a bunch of money to purchase something that cleans it for you, that kind of satisfaction and empowerment, and I think that that is something that will continue and that's a good thing for people that want to do that. That'll be part of the solution. It'll be part of that spectrum, right?

Richard: 1:40:14

I'm also so impressed with all of the innovation that's come around the CR box. I mean people have taken this initial idea and there's minis and there's, you know, the PC fan. I mean we've got so much innovation that I shudder to even call them CR boxes anymore. They're their own thing right. Own thing right. They're, you know, less less, much less noisier, nicer looking, smaller footprint. They tend to have lower clean air delivery rates than the classic box and they are more expensive. So there are these trade-offs, but but even within that little slice of the larger spectrum you talked about, there's a spectrum with respect to diy right, people can choose, you know, maybe, maybe you just need a single four inch filter on a single box fan. If the space is small enough, that will. You don't need to have a, you know, mini refrigerator sized cr box. There's, there's so many possibilities there. It really depends on the space that you're in and what you're trying to accomplish.

Richard: 1:41:25

Um, yeah, that's not sure that answers your question, simon, but I know I think it's a really good perspective.

Simon: 1:41:32

Actually, I wrote down here self-determination, you know. I think it's a really interesting thing. It brings it full circle. Back to risk.

Simon: 1:41:40

You know that people's perception of risk and tolerance of risk is different and one of the things that the cr box has shown is that you can have an impact on your own environment. You're not necessarily reliant on a building's, not necessarily reliant on a building's infrastructure or on industry to remove a certain pollutant from a product. That you can actually determine your own outcome, sometimes with the right approach, and I think that's powerful across all sorts of areas of risk, but particularly air quality. I think that's powerful across all sorts of areas of risk, but particularly air quality, because one of the challenges we've just seen a big article in Science looking to mandate indoor air quality for public spaces and I think a lot of that has been born out of this fear or anxiety that we're somehow going backwards a little bit at the minute.

Simon: 1:42:39

What the pandemic did was that we all started to backwards a little bit. At the minute that we've what? What the pandemic did was that we all started to care about our indoor environment and we seem to be losing that a little bit. I get the sense that people fear that, that we're losing that ground that we've gained, and I think things like the cozy rosenthal box um shows that if you can get people to care enough, they can actually have an outcome. And that can translate to everything from opening the windows every now and then to making sure that your ventilation systems are maintained, to caring about the types of products that you bring into your home or your workplace. It's that people caring enough about air quality and health and well-being outcomes to make a change or to demand it.

Richard: 1:43:24

I agree 100%. The other thing that's very inspiring to me is people using this new technology, this possibility of building your own or building DIY air cleaners is helping others, not just helping yourself. And so you know, on social media you see a lot of this of people building a dozen of them or two dozen or, in some cases, hundreds of them and distributing them to schools in their areas or to nursing homes in their areas, et cetera. Schools in their areas or to nursing homes in their areas, et cetera. At University of California Davis there's a there's a team that works with migrant farm workers in the state of California and they've been distributing them to migrant farm worker families and showing them how to use them, and I was actually building some in my garage for a while to give to this team that go to give to migrant farm workers. You know there's opportunities here, especially when you get to lower and lower cost of something that's still an incredibly effective device to help more and more people that don't have the resources to help themselves.

Simon: 1:44:37

Yeah, no, brilliant Richard. Look. Thanks a million for taking time out of your day to talk to me. It's been absolutely fascinating. Um, congratulations to you and all the co-contributors to the report. Again, I will put a link in the show notes because I think it's well worth people going and having a look at, as I say, even if you can't stomach the what 240 odd pages of the report?

Richard: 1:45:06

Yeah, read the executive summary if you can't read 270 pages.

Simon: 1:45:10

I think yeah, no, indeed, Look, Richard, thanks a million. I really appreciate your time today.

Richard: 1:45:17

It's been an absolute pleasure. Thank you so much, Simon.