Shiven: I first heard about air pollution impacting dementia through the Defy Dementia producer actually, and it's a very eye-opening experience and really interesting because you would never think those two were correlated together. Jay: That's Shiven Taneja. He's a teenager who makes low-cost, high-performance air purifiers to protect people from nasty things in the air, and he's just discovered he may also be helping them protect their brains. You'll meet Shiven later in the show. Allison: Welcome to Defy Dementia, a podcast series for anyone who has a brain. Jay: This podcast is all about living in ways that keep your brain healthy and reduce your risk of dementia. Allison: And that's because dementia is not preordained by genetics. Our genes can play a role, but there are other important risk factors like loneliness, poor sleep or hearing loss. Jay: Research suggests that if we make healthy changes to those lifestyle risk factors, we could reduce dementia cases worldwide by at least 40%. That's a huge number. Allison: Today on the show, a surprising and alarming addition to the list of dementia risk factors, air pollution, both the indoor and outdoor varieties. Jay: I'm Jay Ingram. I'm a science writer and broadcaster. I've been writing and speaking about dementia for more than a quarter-century, Allison: And I'm Allison Sekuler, president and chief scientist at the Baycrest Academy for Research and Education, and the Center for Aging and Brain Health Innovation. Jay: Join us as we Defy Dementia, because you're never too young or too old to take care of your brain. Air pollution has been on people's minds a lot recently because in many parts of the world, we've seen skies filled with the haze of wildfire smoke. We've been breathing it in, smelling it, even tasting it. Allison: We've known air pollution has been a health hazard for a long time, and we've built up a lot of knowledge about how it's dangerous to us and other living things. Jay: But the idea that air pollution may be a risk factor for poor brain health is relatively new. That idea gained new prominence in 2020 when scientists writing in the prestigious UK medical journal, The Lancet, added air pollution to their list of risk factors for dementia. Allison: Later on today's show, we've got expert information on that risk factor and we'll share some lifestyle tips that could help you reduce your exposure to both indoor and outdoor air pollution. But first, how big a deal is air pollution as a dementia risk factor? And for the sake of our brains, should we be worried? Jay: We've got a world expert on that subject. Dr. Marc Weisskopf studies how environmental factors, like air pollution, can affect the health of our brains. He's the Cecil D. and Philip Drinker Professor of Environmental Epidemiology and Physiology at the Harvard Chan School of Public Health at Harvard University, and he joins us from Newton, Massachusetts. Marc, welcome to Defy Dementia. Dr Mark: Thank you. It's a pleasure to be here. Jay: Marc, how big a concern is air pollution as a risk factor for dementia? Dr Mark: I say it is definitely a large concern. One of the issues with air pollution is that it comes in the air and frankly, everybody has to breathe, and so any bit of air pollution that gets into that air, we're all exposed to. And so that's a very large population that is potentially subject to the effects of that. And, so any type of effect that might have on brain function or dementia can really add up to some large numbers when you're exposing an entire population. Allison: And can you give us a quick rundown of what the main pollutants are? What are the major offenders in terms of what we're breathing and where are they coming from? Dr Mark: Sure, sure. Well, it's a long list. There are different things that we study specifically, probably most prominent among them, one we'll often hear about particulate matter and then you hear about particulate matter, or sometimes I'll refer to it as PM, of different sizes. And really, particulate matter is just a sort of catch-all for stuff in the air. So particles that float around, I mean you can think of it almost as the dust in the air, but it's dust we don't see, right? These are very, very small particles, much smaller than even the width of the human hair, for example. And partly because they're so small, they can penetrate deeply into the lungs, they can penetrate to other parts of the body. So particulate matter in itself is something we're concerned with. As I say, it's just the stuff we can get into the fact that depending on where you are, what particulate matter gets made up of can differ. But then there are also other things in the air. One issue is that some things come along with the particles. So you can have a particle come in, but it's carrying metals like lead or vanadium or cadmium. But then there are also gases in the air like nitrogen oxides, nitrogen dioxide, sulfur oxides, ozone. These are gases that are formed by combustion, by tailpipes or by processes in the air, sort of atmospheric chemistry processes from sunlight and the like, that again, float around and we get exposed to when we breathe. Allison: So let's start with these particulates that you mentioned. How small are they and how do they get into the brain? Dr Mark: Sure. So the ones we're most concerned about now that most of the focus on is what we call particulate matter of size 2.5 microns or less. That's maybe 40 of those, 30 to 40 would fit across a human hair. That's the kind of size fraction we're talking about. And how do they get to the brain is a great question. I mean, what we do know is there are a lot of effects of PM 2.5, very well established on the respiratory system and the cardiovascular system. We know these things get deep into the lungs and there's a lung blood barrier. To some degree, particles could go directly across into the circulation and via blood, get to the brain as the particles themselves. We also know though that they will trigger effects in the blood, like inflammatory processes that then are sort of the secondary effects that can also travel to the brain. But there's now actually more and more interest that there may be other routes, for example, simply inhalation through the nose and going directly back through the olfactory bulb, skipping the lungs and the circulatory system and almost going, well, really going directly into the brain is becoming of more and more interest as another root to affect brain function. Jay: So Marc, once they get into the brain, and it sounds like there's a myriad ways of doing that, do we understand how they affect the risk of dementia? Dr Mark: So yes and no. We know many mechanisms that can happen when particles affect the brain. Exactly which ones are responsible for what we see as an increased risk of dementia is still something that's widely under study. We think that one of the main mechanisms by which this may be happening is activation of neuroinflammation. So you sort of respond to insults to the brain, you get inflammatory processes. Those are in the short term and initially beneficial. This is how you protect yourself against external insults. If they go on for too long, they can be damaging. So it's a balance that you need to maintain. But one of the ways we think this may be happening is sort of aberrant activation of the primary immune cell in the brain, which is known as microglia. So that's one way, but there are other ways this can do that, the particles can have these effects. I mean, if you bring a lead atom into the brain, it can affect very particular types of proteins in the brain, disrupt very particular types of signaling that goes on the brain. So there are many different ways that these things could be affecting the brain, and it's an active area of research. Allison: It looks like we're going to have more and more wildfires, and those fires are getting hotter and hotter. So to what extent do major wildfires and the particulates that they produce increase the risk of dementia and cognitive decline? Dr Mark: Sure. So I will say that the research about specific sources of these things affecting dementia is not terribly advanced at this stage. The primary work is focused on that particulate matter, global exposure as a general thing. But of course, one of the ways you can get particular matter is from wildfires. You can get it from tailpipes of cars, you can get it from smokestacks. You can also get it from natural processes like volcanoes, right? So to the extent that wildfires create an extremely high particulate matter exposure, we would expect that they would have a strong influence on these brain effects, such as dementia. I will say that it's another area of very interesting research to try and identify where particular particles are coming from to see whether certain types are more responsible for certain types of outcomes. And a recent paper actually in JAMA Network Open, I believe did try to do this for different sources of particulate matter, which you can identify by sort of fingerprinting the types of things in the particulates. And they actually came away with the conclusion that wildfires as well as agricultural sources of particles were particularly bad for dementia. Allison: Given that at least it looks as though we're having more and more wildfires and the fires are getting hotter and hotter, do you think that that kind of a risk is going to be continuing to grow? That air pollution already was a risk, but is it going to be an even bigger risk in the future? Dr Mark: Absolutely. I mean, we are just seeing these things happen more and more and getting larger and larger in the fire, so I do believe that that's the case. The other really interesting thing about wildfires, someone recently pointed out to me that wildfires is almost becoming a little bit of a misnomer because it sort of conjures up ideas of forests burning. But more and more what we're also seeing now is it's sort of hitting the interface between urban and forest. And so it's now starting to burn things that we don't expect to burn, like buildings and cars, and that starts to release a whole other set of compounds that are quite toxic. And my suspicion would be, although more research needs to be done on this, that those will be even more detrimental for brain effects. Jay: Marc, we've been concentrating on particulates, but you did mention more than once that there are many compounds and you cited nitrogen compounds, especially. Without going into details about all the compounds, what role do nitrogen compounds play? Dr Mark: Yeah, I mean a lot of research in, not necessarily in dementia, although I would say the second most literature for dementia is probably on the nitrogen oxides or nitrogen dioxide, but certainly for other health effects of these types of exposures, nitrogen oxides have been found to cause many detrimental effects. Now I will say this could be from the, say, nitrogen dioxide itself, which could act as an inflammagen that creates inflammation in different tissues. The only other thing to say is that nitrogen dioxide we sometimes look at simply because it tells us it's sort of a marker for things coming out of, in particular like cars. And so when we see signals with nitrogen dioxide, that doesn't necessarily mean it's nitrogen dioxide itself. It could be that it's telling us about stuff coming out of a car's tailpipe, and something about that mix of compounds being spewed into the air is detrimental. But absolutely, even in animal studies or in vitro studies, we can see that nitrogen dioxide and nitrogen oxides can have detrimental effects for brain and for other organs in the body. Jay: We're going to be going into this in greater depth later in the episode, but what do you think, Marc, is the most important thing that people need to know about air pollution and its effects on brain health? Dr Mark: Yeah, I think at this stage, the most important thing to know is that there are these effects. This is relatively new, right? So the Lancet Commission only recently just added air pollution as a risk factor for dementia. And so the evidence base for this is still growing and getting all the details in there. What they need to know is that the evidence is to the point where we really think something is happening. There are still a lot of questions out there, like when in particular over your life does the exposure matter most? Does it have to be many years? Would one very large peak exposure do the same thing as several years of lower exposure? These are all questions we're still grappling with as well as this issue of is there a particular component in there that's the most important. But just the fact that there are effects of these air pollutants on the brain is something people should be aware of in order to try and, not only on a personal level do what you can to avoid excess exposure, but also to help work at a more higher level policy government level to try and limit the levels of these things in the air. Allison: Thank you so much for such an interesting overview of how air pollution might be affecting our brains. It was wonderful chatting with you today. Dr Mark: Thank you very much. Allison: Dr. Marc Weisskopf is the Cecil K. And Philip Drinker Professor of Environmental Epidemiology and Physiology at the Harvard Chan School of Public Health. He joined us from Newton, Massachusetts. Jay: In a few moments, we'll share some lifestyle hacks that can minimize your brain's exposure to air pollution. But up next, a breath of clean air, courtesy of a young caregiver. Shiven Taneja is on his way to visit his grandparents, and like every 16-year-old ever, he's thrilled to be a new driver. Shiven: I finished my driving lessons about a month ago, and they went really well. Jay: He is a little atypical though. He wants to be an engineer. Shiven: That's some pretty good parking, I'm not going to lie. Jay: But Shiven's life took a completely atypical turn during the pandemic. Shiven: Hi, Nani. Speaker 6: Hi, Shiven. Come on in. Shiven: Wait, my shoes. My shoes. Speaker 6: Okay. Jay: He was worried about his grandparents catching COVID. Speaker 6: Nani's waiting to give you a big hug. Jay: And that sent him off on a journey to engineer technology to protect them. Shiven: DaaDee Jii Speaker 7: My grandson. Jay: At the start of COVID, his grandparents were living in India. Shiven's parents invited them to shelter from the pandemic in their home in Mississauga. But even though his grandparents were safely quarantined in the basement of his house, Shiven was still worried about them. He figured that everyone in the house was breathing and rebreathing the same air and everything in it. Shiven: I was thinking because they're senior citizens, so they're more susceptible to the virus, I was thinking, what can I do to help? Jay: Then something on Twitter caught his eye, a tweet about a high-performance, do-it-yourself air purifier called a Corsi-Rosenthal box. Shiven: And when I came across this, I thought it would just be perfect. Jay: It was cheap to make, the plans were everywhere on the internet, and lots of people were making them at home. So Shiven got busy building one himself to protect his grandparents from the virus. Shiven: First, cut this a little bit so that it's perfect. Jay: He used a ruler, a craft knife and cutting board, and lots of duct tape. Shiven: So duct tape's important in order to make sure that the entire box is sealed and airtight so that it operates as effectively as possible. Jay: The cube-shaped Corsi-Rosenthal box uses four high-quality 20 by 20 inch furnace filters. The four filters are duct taped together to make the walls of the cube. The top of the cube is an electric box fan that pulls in room air through the filters and then blows out purified air. It's named after its two inventors. Dr. Richard Corsi, an engineering professor at the University of California Davis, who set out to design a cheap but effective way to remove virus-carrying droplets from the air. Shiven: Let's plug it in. Jay: And Jim Rosenthal, a Texas store owner who refined the design. Shiven: So I start by testing all the fan speeds, making sure the fan's not making any weird noises, just to make sure it's working properly. So start with 3, 2, 1. Then you can hear, speed one is a manageable sound. It's not that bad. Jay: Dr. Corsi and other researchers scientifically tested the performance of this DIY air purifier. They discovered that it removes about 60% of particulates from room air. Now, that might not sound so great compared to a commercial air purifier with a HEPA filter, which can remove almost a hundred percent of particulates, but when it comes to air flow rate, the Corsi-Rosenthal box is the champ. Dr. Corsi says his device can pull air through its filters at up to four times the rate of a three or $400 HEPA air purifier. Shiven: So in the end, this actually ends up becoming sometimes even more effective than a HEPA filter. Jay: With his newly built air purifier up and running, Shiven wasn't worried as much about his grandparents, but then he realized that others in the community were also threatened by the airborne virus. Shiven: I realized this is a very good cost-effective way, but it might be difficult for some people to build, especially seniors or immunocompromised. So I decided I can build these for my community at-cost. Jay: And so Shiven became a caretaker of many. He began making air purifiers for people in retirement homes, public libraries and private homes for $150 each. Shiven's story spread via the news media and the aspiring engineer found himself busy making and delivering air filters. He's made more than 150 of them. Shiven: I think it's taught me that the simplest design is often the best. Jay: Then in the summer of 2023, when forest fire smoke enveloped much of the Northern Hemisphere, people discovered a new appreciation for the device. Shiven: So when all the forest fire smoke was in the air, the Corsi-Rosenthal boxes were a great help since they were found to actually be able to filter it out and clean the air around. Jay: When 3M, the manufacturer of the furnace filters, learned about Shiven's good deeds, the company publicly acknowledged him and they arranged a surprise reward for him. A Zoom conversation with the inventor of the device, Dr. Richard Corsi. Shiven: I'm still in touch with Dr. Corsi. I'm constantly talking to him about different iterations of this, types of filters, fans, how we can decrease the costs and stuff like that. Jay: So what does this story have to do with dementia prevention? Well, when we began researching this episode, we asked scientists, how can people reduce air pollution in their homes? They recommended we speak to Richard Corsi about his air purifiers. We did that, and then Dr. Corsi recommended that we speak to a certain Canadian teen who's become famous for making them. Shiven: I first heard about air pollution impacting dementia through the Defy Dementia producer actually, and it's a very eye-opening experience and really interesting because you would never think those two were correlated together. But it feels very interesting to know that something that started off just as a tool used to filter out COVID and then it went to the wildfires, now to help combat dementia. It's like a never-ending kind of use for the Corsi-Rosenthal box. Jay: The Corsi-Rosenthal box that he made for his grandparents has seen one filter change, but it's still running fine. Speaker 6: I feel safe. Speaker 7: Anyway, we love you. Shiven: I love you too. Allison: If you're curious about building your own Corsi-Rosenthal box, we've got links to the plans on our website, defydementia.org. Speaking of ways to limit our exposure to air pollution, our next guest is an expert in exactly that field. Dr. Tara Kahan is a Professor and Canada research chair in Environmental Analytical Chemistry at the University of Saskatchewan. Her lab studies air pollution in homes, where it comes from and how people interact with exposure to it. She joins us from Saskatoon. Tara, welcome to Defy Dementia. Tara: Hi, Allison. Thank you. It's really great to be here. Allison: So Tara, you were just listening to Shiven. What struck you? Tara: I mean, I was just, first of all just impressed with what a great person he seems to be, but also with how much impact he's been able to have, just with learning a very simple method, making this really simple device and just helping so many people. Allison: And with respect to this particular device, these Corsi-Rosenthal boxes, is there any scientific legitimacy to the idea that they actually are doing something for us? Tara: Oh, absolutely. These have been really heavily studied, and when you take in all of the different considerations, how well they work, how expensive they are, how noisy they are, so will people even use them, these are some of the best things that you can use, better than even buying really expensive devices that are touted to be amazing. These are wonderful. I actually built one of these Corsi-Rosenthal cubes near the beginning of the pandemic, and it was easy enough that my three-year-old daughter actually did a lot of the work. And so, I mean, it's not very attractive, the duct tape is very crooked, but she was so excited about it that she named it Unicorn Sparkles, and she put tinsel all over it and lots of drawings, and then we brought it to her daycare where it was a huge hit. Jay: Tara, you're interested in indoor air quality, and I think most of us are much more familiar with measuring outdoor air quality and hearing about it every day on the weather report. I'd like to know why you focus on indoor and how exactly do you do that? Tara: So the why is such an important question, and the reason is that even though a lot of pollution is generated outdoors, from cars or whatever, we spend more than 90% of our lives indoors. So even if the pollution is made outdoors, we're breathing that air when we're inside. And secondly, there are a lot of sources of pollution, specifically indoors. So things that we do that we don't even think about, like cooking or cleaning, can actually make/generate pollutants. So studying the indoors is really important to understanding how air quality or how pollution in general affects our health. As to the how, that's one of the focuses, I guess, of my research is finding new ways to do this because we have so many techniques that work really, really well outdoors, but that we can't easily use indoors because, again, they're too big or loud or they have radioactive components that nobody will allow in a house. So we try to develop new ways to make measurements indoors that are safe and that won't bother the people who are in there. Jay: Now, you mentioned that there are a number of sources for indoor air pollution actually in the home, not just pollution that's making its way in. Could you give us some examples? Tara: Some of the biggest issues that we have with pollutants are some of the ones that were mentioned by Marc, which are particulate matter. So we think about PM 2.5 like he talked about, and also nitrogen oxides. These can be generated indoors and they're just as bad for us indoors as they are outdoors. Allison: And how are they being generated, and do you have any sort of lifestyle hacks that can limit our exposure to those pollutants in our homes? Tara: Right. So indoors, particulate matter is generally formed... Cooking is one of the biggest ones. And so just the food that you're cooking, like frying or deep-frying will generate a lot of particles. Allison: Or burning. Tara: Or burning. No, we'd never do that. But even if you're using a gas stove, for example, just the gas stove on its own can release a lot of particles and nitrogen oxides. I mean, anytime you have an open flame in your house, you're making these pollutants. So whether that's cooking with a gas stove or lighting candles or burning incense, those scent diffusers that people use, air fresheners, those are big sources. Allison: So things that we think are maybe helping our air smell better and be better is actually putting pollutants into the air. Tara: Yeah, yeah, exactly. There's a big disconnect between what we think of as clean and fresh and what's actually good for us. You're probably better off without them. There are so many ways that we can reduce this exposure. So one of the really nice things actually is that buildings are filters, right? So if you have really bad air pollution outdoors, the air quality is probably much better indoors because that air that's outside has to go through the walls or just sneak through cracks, and you can get much lower levels of pollutants indoors than outdoors. So when there's a bad air quality day because of wildfires or something, the advice is to stay indoors. And you can't necessarily do much about the seals, how leaky your house is or your building, but most houses are reasonably airtight in the sense that even if they're drafty, my house is pretty drafty, but we still don't get a lot of the pollutants outdoors coming in. So I mean, that's one thing, is just stay indoors. I mean, another thing that we can't do. I want to be really clear that although I'm talking about hacks and things that individuals can do, a lot of these issues are not on individuals to solve. These are systemic issues that really we need to address as a society because a lot of people can't choose where they live, right? Within a city, there can be huge differences in levels of outdoor air pollution, which will affect the levels of indoor air pollution, but you have to have enough money to buy a house in a nice part of the city in order to take advantage of that. So some of the things that we can do as individuals is when we know that we are generating pollutants, such as particulate matter and nitrogen oxides indoors, we can open the windows if it's nice enough out. We can use our range hood over our stove. I know most people don't use those, but they do help a lot as long as they're vented outdoors. If they're just the ones that recirculate, then they're just putting everything right back into your kitchen. But as long as they vent outdoors, that's a huge thing we can do. And if you're also looking for a new stove, for example, you could switch out your gas stove for electric or induction. And again, this is not an option everybody has. Unfortunately, induction stoves are expensive, but this is something that if you can consider, it's something that can help a lot. Allison: So Tara, you mentioned that obviously not everyone can choose where they live or work, so sometimes you have to be in these more polluted areas outside. And I'm wondering what's your view about what we can do to reduce our risk factor when we're outside in these more heavily polluted areas? Tara: So masks block particles, and that's always a great way of filtering, but if you can, just avoiding the sources of pollution are probably the best option. So if there are alternate routes you can take that aren't going by very heavy traffic or various sources of pollution that we see in cities, that's probably the best way to minimize your exposure. Jay: And what about the corresponding best strategy if you're indoors? We don't want to sort of dismay people with a long list of things that they should be doing, so if there were one habit or one thing you could do to limit your indoor air pollution, what would that be? Tara: I think I will still leave it as two things, I'm going to cheat a little, which is really just repeating the whole ventilate and filtrate. So if we can get outdoor air coming in... when we are generating more pollution indoors than is outdoors, of course, if there's wildfire smoke outside, you're not going to open your windows. But if you know that you're doing something indoors that's going to make the air quality worse, try to open those windows. I've been told that even a crack in the winter is good, but also some of the filtration, like if you buy a HEPA filter or make a Corsi-Rosenthal box, something like that can be really helpful as well. So just those two things are fairly straightforward and they will work for a lot of different pollutants. That's the really nice thing is you don't have to be thinking about, oh, I need to worry about particles, or I need to worry about nitrogen oxides. You can just know that you're making the air cleaner. Jay: Tara, I can just imagine that people are thinking, okay, there's indoor air pollution and there's outdoor air pollution. I can't really escape it. How concerned, how scared should I be? Tara: I'm really glad you asked that, Jay, because I get really excited talking about this because this is my research and so I can be throwing out all this information and making it sound like this is what's going to kill us all. Stop breathing immediately. But that's not the case. These pollutants that we talk about are risk factors, but they're one of many for all sorts of health concerns. If you smoke, the things that I talked about are probably not even on the radar. And a lot of these things, some people may be affected and some people may not. So while I think we should be aware of these issues, and if it's easy to do some of these hacks I talked about to minimize your exposure, then why not? But I don't think we should feel like we're hurting ourselves or hurting our families if we aren't able to make those changes. Jay: This is hugely useful. I honestly have not thought much about, maybe not burn the candles tonight, quite so much. Thanks a lot for this, Tara. Tara: It was my pleasure. Jay: Dr. Tara Kahan is a professor in Canada, research chair in environmental analytical chemistry at the University of Saskatchewan. She joined us from Saskatoon. Allison: So Jay, such interesting conversations today. What did you take out of all of that? Jay: One of the things that strikes me about this is just the awareness that particulate matter in the air, air quality generally, is a risk. And I don't think that's something that most of us are aware of, generally. We know other things that partly we've learned from the podcast series itself, but I just think knowing that you should be aware of air quality wherever you are is really important. Allison: And I think it's also important to recognize that there are some easy things that you can do to take action to protect the air quality around you yourself, whether it's wearing masks or building these Corsi-Rosenthal boxes, checking the air quality outside. But it's also critical for people to understand that the risk is relatively low and it's really a societal problem. So even if you're not able to sort of control the environment that you're living in, we can kind of all work together, can't we, to try to do things to reduce air pollution for everybody, to help everybody improve their brain health. To find out more about how you can reduce the risk of dementia or slow its progression, please visit us at defydementia.org there. You can check out other episodes of this podcast as well as our videos and infographics. And for the do-it-yourselfers out there, there are also plans included on how to build your own Corsi-Rosenthal box. Jay: Our podcast production team is Rosanne Aleong, Monique Cheng, Sylvain Dubroqua , and our Chase producer is Ben Schaub. Production is by Podtex, Music by Steve Dodd, and our cover art is by Amanda Forbus and Wendy Tilby. And we'd also like to thank Dr. Richard Corsi for his help on this episode. Allison: And we're also sending out a big thank you to the funder of this podcast series, the Public Health Agency of Canada. Please note that the views expressed here do not necessarily represent the views of the Public Health Agency of Canada. Jay: Your support is greatly appreciated, so please hit that subscribe button for Defy Dementia on Spotify, Apple Podcasts, Google Podcasts, wherever you get your podcasts. I'm Jay Ingram. Allison: And I'm Allison Sekuler. Don't miss our next episode of Defy Dementia. It's all about sleep, how the lack of it is a risk factor for dementia and what you can do to improve your sleep. So until then, sweet dreams and sleep well.