Environmental Pollution, Health, and Performance, with Dr. Michael Koehle

Should we modify how, where, and when we train based on our potential exposure to pollutants?

Environmental Pollution, Health, and Performance, with Dr. Michael Koehle

As pollution levels increase around the globe, whether from vehicle traffic, wildfires, Ozone, industrial or other sources, it’s time to ask the question: Should we modify how, where, and when we train based on our potential exposure to pollutants? Furthermore, are certain pollutants worse than others? Finally, can we, and if so, should we try to “adapt” to certain pollutants? 

We’re joined by a leading expert in the field of environmental pollution and its effects on exercise performance and health, Dr. Michael Koehle, from the University of British Columbia. With his help, we’ll address the different risks associated with pollution exposure, and how those effects change based on the concentration and duration of our exposure, as well as how we breathe. 

Finally, Dr. Koehle, as well as environmental physiologist Dr. Stephen Cheung and pro cyclist Shayna Powless, share their recommendations for training in a polluted world. Ultimately, exercise is good, pollution is bad, and there are things we can do to lessen the impact based on the conditions that day.  

Episode Transcript

Chris Case  00:12

Hey everyone, welcome to Fast Talk your source for the science of endurance performance. I’m your host Chris Case. As pollution levels increase around the globe, whether from vehicle traffic, wildfires, ozone, industrial, or other sources, it’s time to ask the question, should we modify how, where, and when we train based on our potential exposure to pollutants? Furthermore, are there certain pollutants that are worse than others? Finally, can we, and if so, should we try to adapt to certain pollutants. We’re joined today by a leading expert in the field of environmental pollution and its effects on exercise performance in health, Dr. Michael Koehle from the University of British Columbia. With his health, we’ll address the different risks associated with pollution exposure, and how those effects change based on the concentration and duration of our exposure as well as how we breathe. Finally, Dr. Koehle, as well as environmental physiologist Dr. Stephen Cheung, and pro cyclist Shayna Powless, share their recommendations for training in a polluted world. Ultimately, exercise is good, pollution is bad, and there are things we can do to lessen the impact based on the conditions that day. Let’s make you fast.


Chris Case  01:39

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Chris Case  02:22

Welcome to Fast Talk Dr. Koehle, it’s a pleasure to have you on the program. I know you come well recommended from Dr. Stephen Cheung, who our listeners will know quite well. So, we’re looking forward to this conversation. Thanks for joining us.


Dr. Michael Koehle  02:36

Well, thank you both. It’s really a pleasure to be here. I’m a fan of the program. So, it’s an honor.


Looking at Pollution From a Health and Performance Perspective

Chris Case  02:41

So, today’s episode is really taking a look at pollution from both a health and performance perspective, and we’ll get there. I’m curious to know if you wouldn’t mind sharing a little bit about how does one end up focusing on this area? You have both an MD and a Ph.D., I believe, how did you land in this realm?


Dr. Michael Koehle: Background in Pollution Studies

Dr. Michael Koehle  03:04

A couple of factors. So, you’re right my job is a nice mix, I do practice clinical sports medicine, and then I do exercise environmental physiology research on the side. So, I kind of came into the job, the research job is an environmental physiologist like Stephen Cheung, Dr. Cheung does a lot of temperature-related stuff, and my background was more in altitude and sort of the interaction between high altitude and exercise, more from a health point of view than a performance point of view. I’m not sure exactly how I got involved in the pollution side of things, I think it was just an area of interest. It’s a bit of when you’re living in a place like Vancouver at sea level, it’s not the optimal place to study high altitude, whereas air pollution affects us all in varying ways. So, you know, I’ve always been fascinated by the human response to exercise, the pollution thing, which is a really complicated area, as is exercise, and I think the media messaging at the time is very confusing for consumers and for clinicians too because we know that we want to be exercising and doing it more for a variety of reasons, and we should know that air pollution is bad for us for a variety of reasons, but how they interact is really, at the time and still is kind of poorly understood and is an area that we really need to like, how do you balance the good effects of exercise with the bad effects of air pollution? I guess that’s sort of something that really interested us, especially for things like the active commuter, people that walk, run, or cycle to work in an inner-city, we wanted to be able to come up with some guidance for them.


Chris Case  04:55

Yeah, and I think that is a major point that we’ll touch upon throughout this episode is the balance between these two ends of the spectrum pollution being bad exercise being good, how do you make judgments on what amount of exercise to do if air pollution is high or low or somewhere in between? I think we’ll touch upon that throughout. I wonder if we should start with this reality, it might seem pretty simple, but I think this is where it actually begins to be complex is, what is pollution? How many types of pollution are we talking about here? And what are the different effects?


What Is Pollution?

Dr. Michael Koehle  05:39

Yeah, yeah, so that’s a great place to start, Chris, in that pollution is very complicated, it’s really a mix of gases and particles, and the gases can be things like ground-level ozone, or carbon monoxide, and then the particles can be things like pollen, or dust from a road, or soot from wildfires, which affects you guys in Colorado, and certainly affects us up here in British Columbia, or particles of even heavy metals, or products of the internal combustion. The pollution is always changing during the day, during the season, and in different locations. So, I like to think of it as a bit of a recipe, and every place and season a time of day, you’re having a different recipe, certain amounts of gases, versus certain amounts of particle. So, for example, you know, wildfire season, that’s really heavy in particles, things like soot from the fire. We have the Olympics coming up in Tokyo, Tokyo is unique in that they have particularly high levels of ozone, which has different effects from the wildfire. So, we can’t use our solutions for riding around Boulder that we use for Tokyo, and we must treat them differently.


Trevor Connor  07:07

There was something I really got out of your presentation that Chris and I watched, and also have to Dr. Cheung’s book, which is we tend to think of pollution as this big monolith, but it’s not, and it actually makes researching it very hard, because one study might look at one particular mix, another study, so you call it a recipe, which is kind of like, another study might look at a different recipe, and as you said, how you handle it, the effects it has on you and what you should do in terms of your training are going to be very different depending on that recipe.


Pollution as a Recipe

Dr. Michael Koehle  07:42

Yeah, that’s exactly right. So, when we look at the research, there are pros and cons, advantages and disadvantages, or every single study. So, we have colleagues we work closely with within São Paulo, Brazil, and they have a ready source of high-quality air pollution right next to their lab, which’s one of the busiest roads in São Paulo.


Chris Case  08:07

I like the high-quality source of air pollution, that’s a funny way of putting it.


Dr. Michael Koehle  08:12

Yeah, well, it really is the perfect recipe for São Paulo air pollution, they just pump it in from the highway, whereas here in Vancouver, we kind of have good air quality 48 to 50 weeks of the year, and then wildfire season shows up and then we have really bad air quality. So, we have to create or import our air pollution, and so we use sort of different models. Often, we use a bit, maybe you could say less realistic air pollution but perhaps more controlled. So, when we’re doing our studies with diesel exhaust, we set it so that we get a certain type of particle that is called PMT-.5 because it’s a certain size of the particle, and we want 300 micrograms per cubic meter every time we collect data. So, every participant has the same experience, and that’s good, but the whole thing is, well, diesel exhaust is representative of diesel, but we don’t have that much ozone in there and not as many oxides of nitrogen, so that’s why we have to look at everybody’s different model of research and take a little piece of everything to sort of trying to understand this puzzle.


Trevor Connor  09:31

So, I remember in your presentation you talk particularly about two, ozone and carbon dioxide, which appeared to have impacts on pulmonary function, particularly carbon monoxide because it has a much higher affinity for binding to hemoglobin then oxygen. So, basically, if you’re breathing a lot of carbon monoxide and oxygen it’s going to affect your ability to deliver oxygen to the work in cells.


Impacts on Pulmonary Function

Dr. Michael Koehle  09:59

Yeah, exactly. So, you’re right about sort of putting ozone and carbon monoxide a bit separate, because they’re separate for a few reasons. One of them is we understand their effects on the body, and carbon monoxide exactly for the reason you say, has this high affinity for hemoglobin, it competes with the oxygen, and so it has a very clear mechanism that have a detrimental effect on performance. Actually, it’s interesting, and maybe you’ve talked about this some previous episodes, there is a sort of a method of using carbon monoxide as a performance enhancer, because it’s almost like altitude in a bottle, in that you can make the blood hypoxemic mix low oxygen in the blood temporarily to stimulate the human sort of physiological adaptation or a climatization to the low oxygen, and then when it’s time to do a hard workout, you can have them in a low carbon monoxide situation, so that you have a lot of oxygen-carrying capacity of the blood, and you can work really hard. So, it’s almost like that live high train low concept. So, we understand the carbon monoxide really quite well, and the effects, especially on performance are quite clear, ozone is is different in that it’s we call it a secondary pollutant, ozone typically doesn’t come out of the back of cars or out of smokestacks, but it’s created later on. It’s a secondary pollutant in that you combine hydrocarbons, oxides of nitrogen, and ultraviolet light from the sun, and that creates ozone. So, on high heat, high sun, late in the day, ozone levels typically are higher. Ozone itself seems to be a bit of an irritant to the lungs. So, other than carbon monoxide, I’d say, ozone is the one that has the clearest effects, both in terms of health and performance as well.


Adapting to Ozone

Dr. Michael Koehle  12:12

I don’t know if you want to get into it now, but there’s also some evidence that we can adapt to ozone. This is something that they really figured out in actually in the 80s, and then they started to work on it, and then people stopped researching ozone, because, you know, especially with California’s pollution regulations and stuff, ozone became less of a factor compared to how it was in, say, the 70s. People who are exposed to ozone, have a reduction in their lung function, but if you keep that up and expose them to ozone for, say, four or five days in a row, they seem to become less responsive or more protected against the ozone and their lung function improves. There was a really neat modeling study where they looked at track and field meet in a high ozone location, and they looked at where everyone came from, did they come from a high ozone community or low ozone community? The people from the high ozone community who were presumably adapted to ozone at the track meet, perform better than the people who were not exposed routinely to ozone. So, that’s one thing that seems to make ozone quite different compared to the other pollutants, we may actually be able to adapt to it. So, that’s something to think about, especially coming up with the Olympics happening this summer, where ozone levels are higher than a back home lot of athletes, one of the things that we will publish an editorial on this is that maybe people may want to actually sort of pay attention to the amount of ozone they’re experiencing in the days up to the competition. Typically, especially for endurance sports, they’re going to be doing heat and humidity acclimation prior to the Olympic Games anyway, because Tokyo is a very hot, humid environment for endurance athletes, so they may get a bit sort of combined heat humidity and ozone adaptation prior to the game. So, that’s something that’s quite unique with ozone and we just got funded for a study we’re gonna actually be looking at that a lot in the next year or two, the adaptation effect.


Shayna Powless: Minimizing Exposure to Pollution

Trevor Connor  14:40

Shayna Powless, a pro in Team 2024, has had to deal with all types of pollution living in an urban environment like Los Angeles. She uses things like Zwift to reduce her exposure when exercising. Let’s hear her insights and how she’s dealt with training in pollution for both herself and for the athletes that she coaches.


Shayna Powless  14:58

Definitely not ideal to be an athlete, especially a professional athlete, living and training in a particularly polluted area. For me personally, I’ve lived in a couple of different places where pollution can be a pretty big issue. Living in the Los Angeles area, there are certain parts of L.A. that are definitely polluted, I would say. So, especially like with the amount of traffic and cars going through, I would say, pollution can definitely be an issue in bigger cities like L.A. So, I lived in L.A. for five years, I went to school at UCLA, and thankfully, a lot of my training actually was out on the PCH like along the coast, but whenever I would kind of go more inland, there were definitely days that were worse than others with the pollution, especially if you kind of go more inland in the LA area. So, on those particularly more polluted days, or if I have days where I am riding more inland, and it does tend to be more, you know, smoggy with traffic and everything in the big city area, I would always just make sure I communicate with my coach, and make sure that we’re modifying or adjusting, and then also, with my own athletes, they live in certain areas where it tends to be more polluted than other areas, or if it’s just a particularly more polluted day than others, then communication is key. From there, just adjusting, modifying training, so that either A, you’re spending as little time as possible outside training in that pollution, and then just kind of you know, riding inside whether it’s on Zwift, your trainer, that’s what I’ve personally done in the past, and that’s what I’ve told a lot of my athletes too, as well, on those polluted days.


Chris Case  16:48

So, the modifications you’d make are more in terms of time, how about intensity? Would you recommend that they don’t do anything intense? Or would you prefer that they do intense because it’s shorter, and get out of the bad air as quickly as possible?


Shayna Powless  17:04

If they have super heavy, intense intervals for that particular day, and it was a very particularly smoggy day, then I would just honestly have them stay inside, ride on Zwift. Ideally, if not on Zwift, then you know, just on the trainer, I mean, it would also just depend on exactly the smog levels, those pollution levels. So, it would just really just depend on that whether or not I would say, “Oh, like you definitely have to ride inside today,” versus, “Oh, you can probably just get away with going outside doing like some steady easy riding.” Yeah, it really would just all depend on the actual levels.


Chris Case  17:46

There are times that I’m sure you had to ride in bad air quality from time to time, how would you say it affects your performance?


Air Quality and Performance

Shayna Powless  17:57

I’m the kind of person that I’m very, I would say I’m sensitive to those kinds of things, especially with like my allergies, and I feel like it just kind of, it’s a big snowball effect for me when I go out personally and train when it’s muggy out. So, because of the fact that I have my trainer, Zwift, it’s so easy for me to just stay inside and still be able to get good quality training in. If on a particular day where I didn’t have the option of having my trainer and my Zwift handy and I had no choice but to outside then, honestly, it would just depend on how smoggy it is, and if it’s too bad, then I would just not train at all, but if it’s not too terribly bad, I would honestly just cut it short. Keep it easy, not be outside as much. So yeah.


Trevor Connor  18:52

The question I have for you since you basically have this different recipe everywhere that can really change from over the course of the day. At this point, everybody who’s got a weather app on their phone, it gives an air quality assessment. Is that useful? Is there a value in that? When when you can get such different mixes of these pollutants?


Is There Value in Checking Air Quality?

Dr. Michael Koehle  19:17

I think it’s a really important point we talk about the health effects a little bit later on. Sometimes people may get the impression that the air pollution isn’t actually so bad for our health when we get to the research, but no matter what we need to reduce our air pollution exposure during rest and during exercise and training as much as possible because air pollution contributes to lung disease, heart disease, hospitalizations, mortality. It’s bad for us and so paying attention to air pollution levels is really important. These apps, the EPA has an app, the Environmental Protection Agency in the U.S., there’s a French one that I like because it has a really nice forecast, it’s called pure, which is sort of a pun, that means like a feather, but also like a plume of smoke, because it gives you a forecast. So, say, you look at an 8 am, you can actually see what time of day, they expect the pollution to be at its lowest level.


Separating Yourself From Air Pollution in Terms of Time or Distance

Dr. Michael Koehle  20:27

We always recommend exercisers and cyclists to try to separate themselves from air pollution in terms of time or distance. So, there will be a lot of variation even locally in terms of air pollution levels. So, here in Vancouver, we’re right on the ocean, and so we have the wind coming off the ocean often, certain times of day, bringing fresher air, we’re also surrounded by mountains that can trap in smoke and smog. So, they’ll be significant variations, even within tens of kilometers or miles. So, for cyclists in Vancouver, if you live right in the city, there are two areas to go. You either go north into where the mountains are, or you go south, which is more kind of flat, but there’s good gravel riding there and some good sort of farmland riding. In a day wildfire season, there’s going to be a big difference between going into the mountains and the rural area, and these apps are really effective at showing you that difference. That’s one of the things I would recommend is if you are, say planning a long ride, have a look, see what it’s like in the various regions you would want to ride, choose the lower pollution region, and if you can, if you have that flexibility, choose a time of day which is better. So, often early in the mornings are best always on levels peaks sort of late in the afternoon. Particle levels peak a little bit later in places like Colorado and BC where wildfires an issue, it might be more constant, but you’ll still find dips, depending on how the weather is affecting it. So, the apps that are available, I think are really good tools for cyclists just to minimize that air pollution exposure.


Trevor Connor  22:33

So, what should you be looking for in the app? They all have different scoring systems, some of them are color-coded. Are you looking at absolute levels, or is that color-coding a good guide?


Dr. Michael Koehle  22:45

I do like the color-coding in that each jurisdiction has its own grading system. So, United States one is the AQI, whereas in Canada we use the AQHI, and then there’s a CAQI in Europe, that plume group, they have their own. They’re all derived slightly differently, so I find it a bit confusing for the end-user to sort of differentiating between the two. The thing that’s really fortunate is that all the scales have the same color coding. Whereas in low pollution or low pollution health affected environment, it’s going to be green, and then it progresses through sort of amber orange to red, and then it goes into sort of violet and burgundy when it’s sort of off the charts. So, when you’re planning a ride or an exercise event, ideally, you’re going to do it in at a time in a place where it’s more in the green and yellow area, and less sort of orange, red, burgundy. So, I think that’s helpful, the individual number would be different. So, here we have basically a scale in Canada of one to ten, and then 10 plus. The US scale is sort of centered around 100, whereas 100 is sort of based on the sort of public health guidelines. So, the numbers are really quite different, but the colors are the same, you know, a yellow in the US has pretty well the same interpretation been a yellow here. So, I think going by color is just a lot more convenient.


Trevor Connor  24:31

The question I really wanted to hit you with because I was a little surprised by this, but it makes more sense when you talk about this changing recipe of the pollutants, it seems like there is a fair amount of research that’s been done, it’s still pretty inconclusive. So, what would you say is the status of the research on pollution and exercise?


Status of the Research on Pollution and Exercise

Dr. Michael Koehle  24:54

Yeah, you’re right. I think the best way to think of it is to have two major divisions and Chris brought this up, there are the health effects and then there are the performance effects. I mean sort of exercise performance, so for cyclists, you know, wattage, heart rate, performance and velocity, obviously, performance, and want to study them differently and have different meanings. The way we group the pollutants I think is important, I think we’ve sort of spent a good amount of time talking about carbon monoxide and ozone. For the rest of the pollutants, like the particulates in the oxides of nitrogen, it’s kind of convenient to lump them together into sort of combustion-related or traffic-related air pollutants. So, because A, they typically were exposed to them, typically at the same time. So, cyclists, you’re riding in traffic or near traffic, and you’re going to be exposed to a lot of that traffic-related air pollution. The way people look at that are things like diesel exhaust, or like the Brazilians look at just direct traffic, and when we look at those pollutants from a health point of view, we can see that long-term, air pollution is bad for us. We look at long-term studies that look at exercise patterns over a decade or more, and combine it with air pollution data, the epidemiological studies, which are types of studies show that, yes, air pollution is bad for our health, but physical activity benefits on our health are clear, and they still present persist in most studies, when people are exposed to air pollution. So, from a health point of view, we take that to mean, avoid your exposure to air pollution as much as you can, but not so much that you become sedentary because all your listeners will have a good understanding of how being sedentary is really bad for our health. So, sort of in the long-term health point of view, it’s quite clear that we need to stay physically active. The short-term health effects of air pollution, they’re surprisingly hard to demonstrate with the internal combustion traffic-related air pollution. Exercise is such a complex phenomenon and intense exercise like your listeners will choose to partake in is such a large stimulus on the body that when we do studies of intense exercise in very high pollution conditions, can’t really discern negative acute health effects during exercise or immediately after. When we do the studies in our lab, we’re using quite high levels of air pollution that would, from a color point of view, be in the red zone, not sort of green and yellow, and we’re finding that we don’t see significant performance effects, and we don’t see significant acute health effects during exercise. The long term it seems clear, we need to stay active, we need to minimize air pollution exposure long-term. In the short term, we can’t see big significant effects of exercise almost synergizing with high levels of air pollution over the short- term. This is something that I think was unexpected and surprising, but we’ve just completed a review where we looked at 14,000 studies and sort of called them down to the important ones, and the consensus still holds up that there aren’t clear effects of acute exercise making air pollution effects worse, and you know, Chris, start off by saying you know, air pollution is bad, exercise is good, and that holds up air pollution is bad. We need to avoid it, but the sort of acute exercise in air pollution doesn’t seem to sort of synergizing and make it worse.


Trevor Connor  29:23

I remember as you did in your presentation, you put up on slide pollution bad, but it was lowercase bad, exercise good with upper case good to kind of imply yeah, you want to avoid pollution, but exercise is really good for you, so don’t stop exercising. I admit it was a little surprising that you didn’t find more because so quickly this was in Dr. Young’s book but talked about the effective dose that there there are several things that impact how much pollution you’re exposed to one is the concentration in the air. The second is how long you are exposed to pollution. But the third is ventilation. Obviously, if we’re on a bike or running and going really hard, we’re breathing heavier, which is increasing the amount that we’re breathing in, it’s getting deeper into our lungs. And there’s also that effect that as we start going hard, we move from nasal breathing to oral breathing, and the nasal passages have a filtering effect that you don’t get when you breathe through your mouth. So I would have thought hearing all that that exercise would have a big impact on our exposure to pollution and the damages.


Dr. Michael Koehle  30:42

Yeah, and you’re right about all those factors, and your metabolic rate is higher during exercise. So, all those things are theoretical reasons why exercise will increase the dose of air pollution over the short term, but why we would expect to see more pronounced negative effects of air pollution. But in our studies, and in studies that our colleagues do at other sites in Europe and in Brazil, we can’t see that consistent effect. I think one of the things that we really need to think about is we’re exercising only a portion of our day, whereas we’re exposed to air pollution 24 hours a day. The negative effects of air pollution are incontrovertible. The message we’d really like to get across is, you know, that one hour exercise during air pollution, we’re not seeing additive effects from the exercise, but still avoid the air pollution and then during rest, minimize your exposure. So, when we’re working with athletes, there was a world track and field championship a year and a half ago were in Qatar, and they had really high pollution levels, especially around midnight. That’s when they hold the marathon, the marathons start with something like 11:30 pm because of the temperature. So, the athletes we’re going to be running a marathon in the highest or very high pollution time of day, there were concerns around that. So, one of the strategies that we’re recommending for them is, you know, will get two masks later, probably but do everything you can to avoid air pollution for the rest of the day. Have them inside and climate-controlled areas with high-quality filtering, if they’re outside on their way to their event, maybe they should be actually wearing a mask to reduce that pollution exposure. Just because, you know, we spend, even elite athletes are spending more time at rest than during exercise in their day, and we can really minimize their pollution effect at rest, so that, you know, they’re minimizing their total dose even though they may still be exercising near pollution.


Trevor Connor  33:06

Dr. Stephen Cheung, cyclist, and researcher at Brock University is well versed in the science of environmental effects on training. We just talked about factors that affect our exposures such as concentration and time of day. Dr. Cheung takes it a step further and talks about how heat and cold can add to the effect that pollution has on our bodies.


Dr. Stephen Cheung: Temperatures and the Effects Pollution Has on Our Bodies

Dr. Stephen Cheung  33:25

They kind of affect you in different ways, let’s talk about heat first of all, and especially we’re coming up to Tokyo, we’re coming up to other major games in the summertime in polluted cities to begin with. In the summertime with the heat, it exacerbates pollution by increasing the level of overall smog. So, that’s why you always hear about smog alerts, and they usually coincide with days that are hot. The reason why that is is that ozone levels are greatly increased during the heat because they are a combination of the pollutants that are already in the air, like nitrogen oxides, like the volatile organic compounds, when they are mixed in with the addition of heat and sunlight, that’s what creates ground-level ozone. So, ground-level ozone greatly elevates during those periods of very hot weather in combination with already existing pollution. So, that’s going to be the big danger that there are just simply greater levels of ozone overall, than you would on the same day where it’s maybe not that sunny and also not that hot. So, that’s a big danger, that’s certainly what we saw in Beijing in the 2008 Olympics, where again, it was held in a very, very polluted city, on top of that, there was also very hot and humid weather mixing in with everything.


Dr. Stephen Cheung  35:00

So, we can talk more about how to kind of counteract that a little bit, but let’s get to the second part of the question, which was, how does cold weather affect pollutant levels in your exposure and response to pollution? The way that happens is not necessarily with the greater amount of pollutants, such as creating more ozone, what happens is, if you’re in a cold often, many of us already have some kind of exercise-induced bronchoconstriction, our airways are a bit more irritated, and because of the dry air that we are breathing in, and when we mix into that the impact of pollutants such as particulate matter, which also irritates our airways, so you kind of has two things that are irritating your airways instead of just the code itself. So, it can cause any pre-existing tendencies that exercise-induced bronchoconstriction and irritation of the airways become even more so when we are in cold. So, those are the two kinds of opposite challenges. In the heat, there are more overall pollutants, especially ozone, and in the cold, there is a greater risk for the pollutants affecting us in terms of bronchoconstriction.


Combating the Effects of Heat Amplification of Pollutants

Chris Case  36:24

Very good. You mentioned earlier there are some things you can do to combat the effects of heat amplification of pollutants effect on you, you want to dive into that a little bit?


Dr. Stephen Cheung  36:36

Sure. One of the things you can do is really time your exercise differently to be in the cooler parts of the day. Maybe before rush hour, you know, even if it means getting up earlier before there’s a lot of pollutants that are built up in the atmosphere because of whether it’s industry, whether it’s traffic, and also because of the warmer temperatures during the middle part of the day, so you can reduce your exposure that way. Then again on high alert days smuggler, you don’t necessarily want to be exercising outdoors. Just like if you’re in California and the wildfires you don’t want to be exercising when it’s a lot of wood smoke kind of coming through your part of the area. So, you want to minimize exposure, that’s obviously number one, you don’t necessarily want to be doing the really high-intensity efforts, because in those very high pollution days if you do a lot of hard, hard efforts, you’re also going to be breathing in deeper than you would if you were doing a light exercise. So, you’re breathing in more volume, but you’re also breathing in deeper, so for the same level of pollutants, they may be getting deeper into your airways and actually into your alveoli. So, those are the ways to kind of very broad strokes without the kind of doing any technology or anything is one is to reduce your exposure by altering your time of exercise, and the other is maybe modifying your exercise so that you’re not doing the really intense efforts. The other things you can do is to you know if necessarily exercise indoors if possible, and obviously assuming you have a decent filtration system in your indoor space, otherwise, you can be breathing in outside air, that but just indoors. So, that’s something else that you can be doing. Then there’s still some hesitation about antioxidants. whether they help or not. There’s some studies that do show that taking in more antioxidants can have a long-term benefit in terms of reducing your impact from pollution. There are some other studies that don’t show it. So. it’s somewhat equivocal, but it’s probably not really an acute benefit. It’s more kind of a long-term benefit if that’s the case.


Trevor Connor  39:29

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Pollutants That Exist in the Outdoor World Versus Indoor Settings

Chris Case  41:23

One thing that I don’t think we’ve really differentiated here is the pollutants that exist in the outdoor world versus those that might be specific to indoor settings. Certainly some, you know, last summer, for example, I don’t think any home in Boulder was immune to the smell of smoke entering into the house, right? So, you can assume that some of that pollution that was in the air was also inside your house, but I must believe that there are some types of pollution that primarily exist inside, is that true? And is that a different discussion altogether? For example, Zwifting is a big thing now, should people be concerned about the air pollution inside their house?


Dr. Michael Koehle  42:16

Yeah, you’re right, there’s sort of almost two kinds of air pollution during. wildfire season, for sure you get a lot of the particle and you can just smell it inside your house. I’m guilty, we’re bad at in terms of wildfire, I would do more Zwift and less riding outside trying to trick myself into thinking that it’s better for me. I think that pollution levels typically will be lower, especially if you have some sort of climate control, and you have filtration as part of that, but the other point that you bring up, Chris is there are also unique indoor air pollutants too. So, you know, things like candles, incense, solvents that are used for cleaning, or to glue down carpets, or we have a gas stove here. So, we have internal combustion in the house, creating particulates, but also even a little bit of carbon monoxide. It’s a bit of an unknown in that there isn’t a body of research looking at the air pollution in the indoor exercise equation. You go into a brand-new gym, they’ve just painted, they’ve laid down some new carpet, or that rubbery stuff, I’m sure there’s a lot of volatile organic compounds that are affecting us as well. So, it’s a conversation that we need to get into, but from a research point of view, we really haven’t looked at the exercise side of that and we need to.


Chris Case  43:54

Now we’ve talked about what affects exposure and that effective dose, one thing that comes to mind is the fact that cyclists they’re riding often four or five hours. What does the data say about that type of exposure versus something that’s a bit shorter in duration?


Duration of Exercise and Negative Impacts of Pollution

Dr. Michael Koehle  44:19

Yeah, Chris, I think it’s really important, especially for your listeners, because that is something that’s somewhat, I want a unique but characteristic of cyclists in that these long aerobic rides are a big, important part of the training. When we look at all the acute studies, I only know of one that’s longer than an hour in duration. Most of them are shorter than that, even if they are an hour they’re quite low intensity. So, that’s an area that we need to look at is this sort of long, slow ride, in that it’s four or five hours you’re going to have a much higher pollution dose over that long period of time. I think that would be sort of a caution message. We actually recommend that specifically on high pollution days. So, say it’s wildfire season in Boulder, if you must ride, it actually makes sense to do some intense shorter intensity work and not your long, slow distance. We studied that we had cyclists training in high pollution conditions, at rest, low intensity, and high intensity. We were expecting for all the reasons Trevor mentioned earlier, that the high intensity would compound the effect you’re breathing more high intensity or more through your mouth, all those things, you’d have more an effect. The only difference we saw between low and high intensity in cycling, cycling exercise was the VO2, the oxygen consumption in air pollution and diesel exhaust, in this case, was slightly higher and diesel exhaust versus clean air during the low-intensity exercise, and it was no different during the high-intensity exercise. So, that’s the opposite of what we were expecting. We wanted to see more negative effects, more metabolic cost during high-intensity exercise because that would make sense. We actually saw the opposite, and we looked at a lot of different factors in terms of blood vessel function, heart function, lung function, and we didn’t see a worsening effect in terms of high-intensity exercise. So, if my coach is giving me a long, four-hour easy ride to do today, but it’s a high pollution day, and tomorrow, I’ve got some, you know, sweet spot intervals, but it’s a much shorter ride, if you have to do that ride, you choose the best location and time of day, but I would recommend that sort of shorter, higher intensity sweet spot ride over that long, slow ride, you put that off until the wind picks up or you have some rain or something to clear out the pollution.


Trevor Connor  47:07

Yeah, that really surprised me in your research that I would have thought high intensity, for all the reasons we are talking about would really impact your exposure to the pollution and the effect it has on you. I was quite surprised when he said no, it seems low intensity and longer, the pollution has a bigger effect on you.


Dr. Michael Koehle  47:31

Actionable things would be you know, Zwift indoors is probably better than outdoors, but you know, it’s hard to do those five-hour rides on Zwift, but it’s easy to do something structured or something like that. So, those would be sort of actionable strategies for your listeners on really high pollution days is to have more of those short, structured workouts, maybe more indoors, and then we’ll leave the longer robot rides a little bit later until things clear up.


Trevor Connor  47:59

Before we talk a little more about how much this impacts performance, I do want to take a little deeper dive into just the general health impacts of pollution. It seems like most of it is in the cardiovascular system, you see rises in blood pressure, you see changes in endothelial function, and it also appears that it is causing a lot of this through inflammation.


General Health Impacts of Pollution

Dr. Michael Koehle  48:26

I would also add to that lung, lung function. So, especially where there are studies that kids that are exposed to either type of pollution sort of particulates from indoor ice hockey or ozone, their prevalence of asthma over time will increase. That’s sort of one of the long-term things to think about, and especially, you know, everything we’ve been talking about is really for healthy individuals, right? A lot of endurance athletes and a lot of top endurance athletes have some component of asthma or exercise-induced bronchoconstriction, as well. That does change things a little bit as well. I was mentioning earlier how the ozone effects seem to be a little bit clearer than the other sources of air pollution, and that’s particularly true in terms of people with asthma or exercise-induced bronchoconstriction, which is sort of asthma triggered by exercise and that they do seem to get a bit of impairment in lung function in response to that ozone, and that can lead to performance effects from that.


Trevor Connor  49:34

It also seems these bronchodilators could actually in a high pollution environment, they can potentially hurt, is that the case?


Dr. Michael Koehle  49:43

Yeah, so it’s sort of like what you’re talking about earlier with exercise, how a bronchodilator, a typical bronchodilator is Ventolin or albuterol is the American chemical name for it, we call it salbutamol up here, what it does is it relaxes the muscles around the airways, which will open airways make the diameter of the airways greater, and so you’d think, well, that would mean that the pollution gets deeper into the lungs, and increases the air pollution dose, right? So, theoretically, you think maybe these are problematic, and so, and there were some animal researches that indicated that might be the case. So, we specifically studied that we got a bunch of people with exercise-induced bronchoconstriction, so asthmatics who get airway issues during exercise, we exposed them to really high levels of air pollution or filtered air and it was blinded, and their asthma medication, their bronchodilators, or placebo, and there was no worsening effect at all, and the bronchodilators did what they were supposed to do, in terms of opening up the airways of the cosmetics, but so no negative effects. So, our sort of take-home message for people with asthma and exercise-induced bronchoconstriction is get good control of your asthma in conjunction with your physician if it is requiring medications, and typically, it may be one or two medications. If it’s a high pollution situation, don’t change that, meaning don’t forego your medications, thinking that you may increase your dose. In fact, it’s the opposite, follow your physicians’ guidelines and take your asthma medications, and they will do their job.


Chris Case  51:37

I would like to give you a hypothetical Dr. Koehle here, it was a particularly bad year for wildfires across the United States last year, and in a lot of places, honestly, around the world, and I feel like those conditions may be more likely to happen in the future because of lots of factors, including climate change. For people that are training, and they’re serious about their sport, whether they’re professional or elite, amateurs, they might go out and they’re doing their best to avoid heavy times of pollution, but they’re still going to get in their rides, they’re kind of they’ve got that attitude, like exercise, good, pollution bad, but exercise much better for me, I’m going to do it anyway, I need this. They might go out and it’s pretty bad air quality, maybe there’s a wildfire not far from them, and they’re going to get it in. They don’t necessarily feel terrible that day, or the next day or the next day. I’m curious if the research helps explain or if you can just give recommendations or maybe not recommendations, but what are the potentially permanent effects, negative effects that somebody could encounter if they do this, and somewhat disregard the recommendations to avoid heavy days of air pollution?


Permanent Effects of Air Pollution

Dr. Michael Koehle  53:05

The evidence I think about is that just by living in a city, you increase your risk of lung disease and even lung cancer, and that’s an air pollution thing. We also know that exposure to air pollution leads to cardiovascular disease, admissions to hospital for things like heart attacks, and so air pollution exposure over time will increase your risk of all of these things. I think in the last 10 years, we’ve seen an increase in the number of these wild wildfire situations, and there will be knock-on effects in terms of both lung and heart disease. I think it’s really important that it’s the 24-hour exposure to that air pollution that’s causing that, and during that brief period of exercise in that day, it’s not clear that we’re making it worse, and it’s the epidemiological data show that it’s not worth being sedentary. So, in both where you live in we live, the wildfire seasons are only a matter of typically a couple of weeks, and I think it does make good common sense if you can reduce the volume of your training over that period, and focus on some other things, maybe take that as a break to focus a little bit more on your form and your core and get a little bit time away from the bike so that you’re rejuvenated and excited to get back on it. I think it’s totally reasonable to back off a little bit during those periods. We’re fortunate that they only last a couple of weeks at a time. I think that’s a pragmatic approach.


Chris Case  54:45

I’m basically speaking from personal experience, I think Trevor was in the same boat, a lot of people in this area take cycling or running or their sport of choice as a lifestyle. It’s a lifestyle thing, they have a hard time giving it up, honestly, and we dealt with it unfortunately last year for us.


Trevor Connor  55:07

It was particularly bad.


Chris Case  55:08

It seemed like it went on for months, honestly. So, you know, we dealt with it for a while, and we probably some of us at least cut back, eventually we all sort of said, still gonna go out for some long rides. So, I just want to know, I guess I’m asking, what damage have I done to myself? A lot of people out there are in the same boat,


Dr. Michael Koehle  55:34

Whether you rode your bike or not last summer, you increase your risk of lung and heart disease. What we don’t know is whether you are riding and sort of still doing some long rides did anything.


Chris Case  55:54

Beyond what? Just being in this climate during that time already.


Dr. Michael Koehle  55:59

Exactly, yeah.


Chris Case  56:00



Dr. Michael Koehle  56:01

Exactly. If we sort of generalize it a little bit and say, okay, well, maybe it’s if we look at living in the city, a polluted city, which is nowhere near as bad as wildfire season in Colorado was, we know that the people that exercise they get strong, significant benefits to their health that far outweigh the air pollution. So, there’s sort of trying to interpolate between knowing that we don’t see these acute effects during that intense air pollution situation, and that the air pollution is bad. You know what? I’m as biased as both of you are, in wildfire season I’m still on my bike out in the smoke as well. I really think it’s that 24-hour exposure to air pollution that’s harming us.


Chris Case  56:55

I don’t want to jump on that fact too much, but the person that we brought on to this program to speak about the effects of pollution is also getting out there and enjoying himself despite the uptick in some of these pollutants occasionally and doing, taking other precautions that should send a bit of a signal that it’s, you know, exercise is, does outweigh the effects, especially if you’re taking the precautions you can.


Dr. Michael Koehle  57:24

You made me think of the smoker, you know, it’s like if I quit smoking, it’s not worth living. Anyway, I think, you know, for a lot of people cycling is like that.


Chris Case  57:38

Yeah. It’s not all that comparable to smoking let’s hope, but I hear what you’re saying that we get a little obsessed with what we do, and we love it, and sometimes we put blinders on when it comes to our cycling and getting that right in. We’ve touched upon some of the performance effects already, but let’s take a little closer look at that. Dr. Koehle, what’s the evidence there? What are we using in the research?


Dr. Michael Koehle  58:11

Yeah, I think it’s good to divide it up again by pollutant. So, Trevor did a nice job explaining the performance effects of carbon monoxide, and it’s clear, fortunately, it’s generally these days, not a huge pollutant to which we’re exposed. If you do know or that you’re going to be competing in an area where there’s high carbon monoxide, you will get a temporary negative effect, but so all your competitors. Ozone will have a bit of a negative effect in that you’ll feel more breathlessness and you may feel more chest tightness, and that’s in people with and without exercise-induced bronchoconstriction. It’ll be quite moderate, and you will be able to adapt to it a little bit. So, that’s kind of the good rosier side of that, I guess. In terms of the traffic-related air pollutants that the people that have done it the best are Dr. Bertuzzi is at the University of Sao Paulo, and they used, they did a 90-minute cycling time trial, comparing filtered air to that high-quality Sao Paulo air pollution that we talked about. They looked at power output, and it was actually a 50-kilometer time trial, and so you could tell if it’s 50 kilometers, and they’re doing it in about 90-minutes, they’re not the most elite cyclists, but there was absolutely no difference in power output, or heart rate or time to completion. In traffic-related air pollution, there may be a slight difference in how you feel in terms of both breathlessness and that sort of feeling slightly short of breath, but also in your legs. We ask in all our studies, we asked the participants to rate their legs and sort of the rating of perceived exertion, and it’s a very slight increase in pollution condition during the filtered air. It’s important that that doesn’t correlate to change in power or heart rate, or some of these other parameters. In traffic-related air pollution, the performance effects at least up to about 90-minutes, they seem very modest, and it’s more sensation thing, as opposed to power output or speed or heart rate. Where we do see a bit of a performance effect, It’s interesting when we expose people to air pollution before exercise, we did one study where it was again cycling exercise, and we found that if we pre-expose them to, this was diesel exhaust, during the exercise, their heart rate is a little bit higher, and their lung function was a little bit compromised, and that whenever anybody exercises, their airways open up is a response to the adrenaline, the sympathetic influence of exercise, our lungs open up, but that was inhibited a bit by pre-exposure to air pollution. So, in summary, I guess you have kind of a, your legs feel a little bit crappy, you’re noticing your breathing a bit more, but your numbers are the same in terms of your power. That pre-exposure, again, it comes to that sort of minimizing your air pollution outside of competition concept, pre-exposure may have a bit of a performance effect as well.


Trevor Connor  1:01:36

I said we’d come back to this and I want to ask about this. So, you said, for example, with ozone, you can adapt to it. I think to the Beijing Olympics, where most of the athletes tried to arrive at the last minute, you think of somebody like Cachoeiro who said, no, I’m going to show up two weeks early, and try to adjust to the pollution in the air and ended up getting the bronze medal in the road race and winning the time trial. So, you said you can adapt, but the question I want to ask is, is that a good thing? In the long run are you causing yourself greater health impacts by trying to adapt to it?


Long-Term Effects of Adapting to Ozone

Dr. Michael Koehle  1:02:21

It’s an important question to ask you about the sort of long-term consequences of ozone. We do know that repeated exposure may increase the prevalence of asthma in children, and how it was on works is its prooxidant generating these free radicals that cause inflammation and tissue damage. So, there’s probably no lower limit where there’s no negative effect of ozone. So, the levels that we would recommend in terms of adaptation would be very modest. Within this The World Health Organization Guidelines, which are 100 parts per billion, which is what you would see during rush hour on a bad day in July, in August in Tokyo, we’re not talking about exposing people to sort of supernormal or super high levels of it, but you know, I think the message is always that air pollution is bad for us, but if you know it’s going into your Olympics, this is your A competition of your entire year, your entire four years, if you’re doing a bit of four days of adaptation to ozone, it’s probably worth the trade-off if you’re going to get that a small fraction of percentage of improved performance on race day.


Dr. Michael Koehle  1:03:37

Yeah, I think it’s also worth talking about antioxidants in that there have now been a few studies that have looked at antioxidants. One study looked at red-orange juice, you know, the oranges with red pulp, but most of them just use vitamin C and vitamin E supplements, something like 500 milligrams of vitamin C, and 100 milligrams of vitamin E, they showed that this amount of supplementation for a couple of weeks prior to competition will reduce the negative effects of ozone because that ozone is a pro-oxidant causing the creation of free radicals. These vitamin C and E act to somewhat sort of diminish those effects or to soak up those free radicals. So, that’s a pretty easy, safe strategy to employ 500 milligrams of vitamin C and 100 milligrams of vitamin E daily for the two weeks leading up to competition,


Trevor Connor  1:04:39

Just because a lot of people have the more is better type attitude, if you’re taking antioxidants, be really careful about vitamin E. So, the recommendation you just gave, don’t go above that. Don’t start thinking that more is better. There’s been a lot of research showing that vitamin E if you take too much, can actually have really negative have health impacts on you, part of the reason is vitamin E is a lipid-soluble vitamin. So, once it’s in your system, your body has no way to excrete it. If you have too much in your system, it can do damage. So, don’t overdose on it, please. What are other recommendations? I know we’ve been talking about these all the way through, so maybe this is just a summary. What other recommendations would you give our listeners both for training and for performance when they’re in a place that has high pollution levels?


Masks and Air Pollution

Dr. Michael Koehle  1:05:33

Before getting into summary, I think I’ll just touch on masks because that’s something that people often want to ask about. It does make sense that a mask can reduce your pollution dose, especially on the particle size, there have been very few studies looking at exercise, masks, and air pollution. There’s only one somewhat relevant series of studies, and I say only somewhat relevant because it was walking, it was two hours of walking, which is nothing like the intensity or duration that your listeners would do, and it involved wearing masks for 48 hours. So, 24 hours the day before, and then 24 hours during the day of exercise. There were some modest benefits from a cardiovascular point of view, and so it’s not enough evidence to generalize to say people should be wearing masks when they exercise. The French Ministry of Health did a really nice white paper where they really looked at all the research around masks and exercise, and they did conclude that there wasn’t a clear benefit for it. The mask that they did do this study on was an n-95 mask where you have a complete seal, it was made by 3M, I think it was the 812 masks, but it looks like your standard n-95, it’s going to make it quite difficult for you to during high-intensity efforts, get enough air in and out. So, based on their research, our recommendations are in high pollution situations, especially leading up to competition, if you want to wear a mask outside of training and competition, do it just to lower your overall pollution dose during that day, there’s not enough evidence to recommend it during training, and certainly, during competition, it would affect your oxygen delivery and your ability to get rid of carbon dioxide. So, that sort of, we need to do a lot more work on masks, but that’s sort of the recommendation that we’re giving around that.


Dr. Michael Koehle  1:07:42

In terms of other general recommendations, I’ll sort of repeat, you know, air pollutions bad, so separate yourself by distance and by time. There’s lots of variations within the day in terms of weather and stuff, and so really try to take advantage of that. When it’s bad, it’s probably a little bit better inside, probably choose shorter duration, and maybe higher intensity over long-duration exposures. If you have asthma or exercise-induced bronchoconstriction, make sure that it’s well stabilized in consultation with your physician, take your medications, don’t be worried about taking them during high pollution days, they will be doing their job. If you’re being exposed to a high ozone environment, consider the vitamin C and vitamin E, that was 500 milligrams of vitamin C and only 100 of vitamin E in the lead up to that. I think the last point is when we’re building a good training program for cyclists, we want to take into account training stress, but also non-training stress, and just like altitude, high pollution should be considered non-training stress and you want to take that into account. You may find that your recoveries not quite what you’re expecting, and so you may need a little bit more recovery during high pollution conditions, or maybe you need to back off in terms of the intensity and duration.


Chris Case  1:09:21

Well, Dr. Koehle, we like to close out every episode with some take-homes, you just did a great job of recapping all the recommendations, but we’ll start with you. What would be your overall take-home message for this particular topic in this episode?


Takeaway Messages

Dr. Michael Koehle  1:09:38

Yeah, I think the real take-home message is there’s no doubt that air pollution is bad for us, but we need to reduce our exposure to it 24 hours a day. There’s no doubt that exercise is extremely important for our mental and physical health with a couple of exceptions around carbon monoxide and ozone, it’s really not clear that exercise is exacerbating the negative effects of air pollution. So, as as a result of that, I personally tried to minimize my air pollution exposure, and I still will exercise in high pollution conditions, but I choose where I ride choose when I ride in order to really minimize that


Chris Case  1:10:23

Trevor, what would you say?


Trevor Connor  1:10:25

Well, I think you just absolutely nailed the most important takeaway from here. I would say the second one for me is understanding that there are these different mixes of pollution like you called it, it’s a recipe, every place has its own recipe. It’s probably worth knowing a little bit about what sort of pollution are you dealing with in the region that you’re in. So, we just talked about here in Colorado, we’ve had to do a lot with forest fires, and that’s one pollution. When I lived in Toronto and was riding very close to cars, it’s another type. Depending on the type of pollutions you are dealing with, that might lead to different responses, different actions that you can take, Chris?


Chris Case  1:11:12

Yeah, I’m not sure what else to add both of those are great points. You have to know what you’re being exposed to where you live, and then you can plan accordingly to limit your dose, based on the time of day where certain pollutants might rise where you live, or might subside where you live. So, I think those are both perfect ways to end this episode. Thank you so much, Dr. Koehle, it’s been a pleasure to have you on the show.


Dr. Michael Koehle  1:11:45

Yeah, thank you both. It’s been a pleasure for me to be on the show too.


Trevor Connor  1:11:49

We loved having you, so thank you.


Chris Case  1:11:53

That was another episode of fast Talk. Subscribe to Fast Talk wherever you prefer to find your favorite podcast and be sure to leave us a rating and review. The thoughts and opinions expressed on Fast Talk are those of the individual. As always, we love your feedback, join the conversation at forums.fasttalklabs.com to discuss each episode. Become a member of Fast Talk Laboratories at fasttalklabs.com/join and become part of our education and coaching community. For Dr. Michael Koehle, Dr. Stephen Cheung, Shayna Powless, Trevor Connor. I’m Chris Case. Thanks for listening.