Protecting the health of Canadians and Canadian workers on our warming planet

Protecting the health of Canadians and Canadian workers on our warming planet

thank you very much and i really appreciate this invitation opportunity to speak to all of you today so let’s get started i’m just going to share the screen hopefully things will work out fairly easily so um let me just get this rolling um if you let me know is when you see this screen the full powerpoint you can see the full powerpoint yeah anna yeah yes okay perfect awesome so thank you very much again and i think the the the presentation today is timely certain in view of the heat wave that’s been experienced in bc and certainly out in the western parts of the us um and today i’m really going to cover two components the heat stress the the effects of heat stress and vulnerable population the elderly and patients with chronic disease and i’m also going then also take a look at the effects of heat stress in our aging workforce and give you some valuable insights into the recent work that’s been conducted over the last few years to help you again uh better handle and understand the impacts of heat stress um so it’s without question that essentially what we do know is that we are experiencing a rise in in temperatures globally and the impact is is that there’s a large number of a greater number of people are being exposed to these extreme conditions and i think this is not going to certainly is not going to uh get better it’s going to get worse over the decades to come and we have to be prepared for that to be prepared we need to understand how best to protect our most vulnerable so in terms of achieving that objective um i think we have to understand the impacts that extreme heat can have and certainly i think the heat wave in 2003 is probably one of the landmark um periods in in our history where we saw 70 000 excess deaths recorded in europe during the 2003 heat wave and certainly in russia following in 2010 but sadly in bc as we as as was experienced just recently just over 800 people have lost their lives uh during this brief extreme heat event and based off the news that i was able to see today even the uh heat temperatures are continuing to be elevated in bc which really poses a danger to the most vulnerable including workers before we get moving i do want everybody to be on the same page and perhaps many of you do understand the basics of thermal regulation it’s it’s an area of research that’s not well studied in terms of of of work that’s conducted relative to other areas but i think we need to understand some basics so essentially when you’re sitting down there right now as i would be right now i’m generating heat and i’m hopefully in heat balance unless i’m getting a little stress speaking to you but essentially my body is essentially gaining heat and i’m adjusting my heat loss to make sure that my core temperature remains stable so i’m essentially modulating my skin blood flow and sweat production so essentially again these two avenues will help us achieve heat balance but when we talk about metabolism we’re also talking about the fact that when we do any kind of physical activity we generate heat we’re not a very efficient system and probably only about 15 percent efficient that all of the energy that we take in essentially to and that that energy that’s used to do muscular work is is is lost in terms of heat energy so that is an additional heat gain the key challenge that we face when exposed to a hot environment is the fact that essentially that hot environment adds to the burn that’s placed on the system we end up gaining a little more heat why is that well number one is that skin temperature certainly if air temperature exceeds skin temperature then you’re going to see that essentially the system gains more heat so um what we do lose in terms of our capacity is the fact that we really lose less we’re unable to lose heat via dry heat loss mechanisms in fact we gain heat into our system the only avenue of heat loss that we have available to us thereafter is the production of sweat and hopefully the evaporation of that sweat and i always like to hear people talk about that there are great sweaters but that doesn’t mean anything especially if the sweat just drips off your body it provides absolutely zero cooling benefit to the individual so to put things in perspective again i think we have to look at how we different people respond to the heat we’re not all built the same way and there are reasons that essentially there are multiple reasons why for example if i was exposed to a heat stress and somebody that essentially uh of my age my size um same sex and may have type 2 diabetes makes be exposed to that same level heat stress they may experience a certain amount of heat gain when exposed to that heat stress and they’ll rate achieve a core temperature i might achieve a core temperature at a point a but if they have chronic disease like type 2 diabetes that may cause impairments in their ability to lose heat which would cause them to store even more heat causing the shift then to a much higher core temperature for the same exposure consequently that may lead to heat related injuries so when we assess the effects of heat stress in different individuals it’s not as simple as simply looking at whether they are young or older we also have to take into account a number of intra-individual factors that compromise that consist of sleep state medication use as well as duration of exposure number of consecutive days of exposure all these factor in and how we study or understand the effects of heat stress and we’ve studied all of these different mechanisms another challenge that we have and really understanding the risk somebody experiences is quantifying the heat exposure it’s not as simple as simply looking at a thermo thermometer and saying how hot is it the reality will be and we hear a lot about this that essentially because we live in canada temperate environment that we’re less at risk versus somebody that may live in the southern states where temperatures are much higher simply stated that threshold for heat related mortalities is simply lower in canada and certainly would be lower in the in the more northern uh provinces or northern areas if in fact uh temperatures were out elevated in those regions as well you would see that heat relate mentality would just be a lower threshold but even within the urban environment within a large city you will have variations across different sectors different neighborhoods and that’s to do with how the built up environment plays into the equation then we have building types as well some structures are highly insulated some structures have air conditioning some structures have multi-level residents uh all these play into it as well as to who might or might not be affected during a heat wave and then we have to consider the heat source again you know physical activity is is is an easy source of heat and certainly when you are perhaps cooking in the home you’re generating other uh heat within the home causing temperatures to rise and then we have the physical state of the individual being fitness health status and other factors that really define what that that exposure is going to be like um just try to get my my my laser pointer here so essentially that is important for us to to to take into account so looking at the variation i think this is important because when we look at extreme heat events typically we might refer to a heat alert based on a specific temperature it might be a designated temperature coming from the airport but how accurate is that in protecting all individuals i just said to you early on that essentially there are individual factors that affect one’s ability to lose heat but beyond that there’s also the variations within the the the exposure area so within different neighborhoods in this study conducted in philadelphia we can see that just being within one neighborhood your risk of heat-related mortality is much higher vis-a-vis and some other areas and you can see how this distribution varies across the different sectors of philadelphia and surprisingly um the one thing i hear a lot especially when we write grants and it’s always a bit bit of a quandary why we get these comments but i hear sometimes that people say well if he’s a problem just take them out of the heat it boggles the mind and i i want to go back a year 2020 covet 19 isolation of the most vulnerable these individuals especially those in long-term cares were isolated for long periods during the day with only periodic uh ex you know periodic times to to go and eat lunch in a common room these individuals faced high indoor temperatures and even here in ottawa we saw temperatures that exceeded 30 degrees in some rooms the reality is is that in this study conducted in detroit it showed that even in a non-heat wave situation so these are just normal summer temperatures that we essentially saw max temperatures of 35 degrees celsius so it’s it’s not impossible and what we do see is that progression temperature will increase over the summer period which is another important point is when that heat wave occurs because again we’ll see later on about adaptation over the summer but remember that in fact temperature will progressively get hotter indoors depending on the type of building and you can see here just from the imaging satellite imaging just the risk different communities will face as a function of rising temperatures and and obviously the red areas indicates a high danger zone so you can imagine that the heating of the homes would cause heating of the homes indoors and to that point a study conducted in the netherlands and this is an important point while it’s a temperate environment perhaps a cooler environment it does represent some of our of our areas in canada and i think this again this was a non-heat event but the changes show you over time what happens to indoor temperature as a function of changes in outdoor temperature even the living temperatures indoor can be hotter than the outdoors and this becomes problematic if you’re living in these in these conditions that will probably be even hotter when you have an extreme heat event and particularly we see the effects on bedroom temperature and that is important because in this study that was conducted in the elderly people many of the individuals felt very warm or uncomfortable and you can see it got progressively worse as the summer moved along and you would again and we do know that elderly people will get adopted over the summer and i’ll show you that data later on so in that context then uh what’s important to understand is that progressively as we as we see over here over successive weeks in the summer you can see that there are a number of heat related uh or heat related symptoms that show us that the elderly just don’t do as well over the summer period even though there may be some slight adaptation you’ll see that there are a number of heat related symptoms like sleep disturbance concentration problems fatigue thirst excessive sweating that really take away from the quality of life and again create a physiological burden on the system again it may seem rather benign in terms of looking at some of these systems but imagine having disrupted sleep and living in these extreme heat conditions day after day so for our work and the work that we’ve done over the past number of years has been really directed and understood all these different factors and how it can affect somebody’s capacity to lose heat their physiological capacity to speed heat why is that important not only do we on want to understand what the effects of aging are on the body sorry how how the calorimeter will essentially when we’re when we’re doing these kind of studies what we want to know is not only how aging will affect the body’s ability to dissipate heat we also want to define very specific thresholds so we know at what level of heat stress potentially a person with diabetes may be at greater risk so we have the world’s only whole body calorimeter and you can see it opened up here it would be closed so we see one of our elderly patients inside of this room and what that system allows us to do is measure very precisely the amount of heat dissipated by the body both evaporative and dry heat exchange and we can measure very precisely the amount of heat that the body stores and as the body stores more heat temperature will rise and so let’s take a look at some of this uh information so in one earlier studies that we started in around 2015 and subsequently published this work focusing on young to older adults we had elderly people exposed to three hour extreme heat events now you have to understand that back then there was not a lot of work done in elderly people and exposing an elderly person to 44 degrees celsius 20 was somewhat certainly raised eyebrows from the research ethics board because they were saying geez you’re going to put these people at risk but again exposing individuals if i take the same person exercise them they’re going to experience the same level of heat stress so it’s a bit of a challenge to to conduct this research but let me show you some interesting results so what happens when you enter the heat a hot environment your body gains heat remember what i said early on when temperatures are greater than the skin temperatures the body gains heat very rapidly and you can see that by the blue dots now the white circles not dots but the white circles show you the rate of heat loss so as heat is gained by the body the body tries very quickly to offset that and you can see here that by about two hours heat balance has achieved now i want to put this in context if you or i were going to go out and exercise right now it would take you so long as the conditions are compensable about 35 to 45 minutes to achieve heat balance what’s shocking is that it takes this long for even a young adult to achieve heat balance which shows us our the way we thermal regulate during a passive heat stress in an exercise heat stress is somewhat different but let’s take a look at an older adult why are they at greater risk well what we’re seeing after three hours is that there’s a separation between heat gain and heat loss so there’s we don’t have a balance young they’re bounced he gained heat loss balance core temperature elevated but now stable an older person no balance that means core temperature was rising quickly but attenuate so it’s still rising so what you see is they store about 1.7 times more heat in this three hour heat exposure now let’s migrate to look at what about diabetes we know from our work and work of others that patients with diabetes have a potential reduction in skin blood flow that essentially that impairment skin blood flow will cause potentially greater heat gain why because if skin temperature is lower that means the skin the skin blood flows lower that means skin temperature is also going to be lower and the gradient between the air and the skin is much higher so they’ll gain more heat is the evidence there well let’s take a look at it if we look at the blue line here you can see that this rate is much higher the rate of heat gain overall is much higher in a patient with type 2 diabetes so they’re gaining more heat but we look and we see that the values are roughly the same they store about the same amount of heat over that three hours so how’s that possible well to offset that what they had to do is increase the rate of evaporator sweating so that evaporative heat loss would increase so what it tells us is while they may have the exact same core temperature the patient with type 2 diabetes may be at risk down the road if they face or maintain that exposure for prolonged periods why because sweating is sustained at elevator if they sweat and don’t hydrate adequately what you’re going to see is a gradual dehydration in this individual and a greater burden on the cardiovascular system just to try to maintain perfusion to the skin and and release that heat all right one thing i always hear about is it’s you know when we talk about heat waves it’s all about ambient temperature or air temperature i should say it’s not all about air temperature you can have deadly heat at lower temperatures if humidity is high why because when air temperature is lower and humidity is high or even if it was high temperatures what you have is a situation where the air is saturated with moisture well the whole point of evaporation of sweat is that you want to essentially take that sweat evaporate and that moisture will fill the the the the air problem is if it’s saturated it’s ineffective and you’re going to get a lot of drip sweat so what you see in if we take two different conditions a young and older person in dry heat as you can see 20 relative humidity you see that the older still have these age-related impairment this is a two-hour exposure so the higher the bar the higher the increase in core temperature and you can see if we then expose them to 60 they store this much more heat so even a slight increase in humidity can increase the amount of heat stored in the body by nearly two-fold so humidity matters and even in a lower temperature you can still have an extreme uh you can still have heat related injuries a very important point to remember so let’s take a look at some of the other work that we’re just finishing now i’m giving you a first glimpse into work that we’re going to be submitting for publication very very soon what we have here is we said great you know we’re understanding what’s happening in the elderly when they’re exposed to to heat we see over three hours they’re not achieving heat balance well that raises questions does that mean that their core temperature is going to rise progressively over a day-long exposure that’s a big question an important question are they able to compensate for that exposure so in this study that we’re completing that we just completed we again isolated our patients within the calorimeter and we did a nine-hour day-long exposure to uh to assess the effects of on whole body heat exchange i’m going to present to you the rectal temperature so what you’re seeing here is over that nine hours you can see that they do eventually achieve a stable core temperature but in the first few hours you see like we saw before in the first three hours by fourth hour they started to achieve heat balance so that means now rate of heat gain matched by rate of heat loss but it took that long to get that heat balance that’s important and relative to the younger individual we still see again they reach achieve the heat bounce much much lower temperature and they have a greater capacity to lose heat as because of that you can see that essentially the older do exceed what would be the safe conditions that who recommends being that core temperature would be lower than one degree and we can certainly see a number this is your standard deviation number of the patients had temperatures well above that with some up to as high as 1.8 above baseline resting temperatures now the conditions that i’ve shown you thus far are in the more extremes and possibly more likely reflective of the heat wave in bc at the end of june start of july and that would be humidex between 40 and 50 degrees c in ottawa in 2018 we experienced a very extreme heat event in which we had a humid x of 47 degrees um sorry uh yeah humidex of 47. and again those are certainly the extreme now the reality will be is when we look at um the conditions indoors those conditions don’t always reflect what’s outdoor but they get very very hot and therein lies the problem it’s not that have elderly people sitting outside an extreme heat event that’s not the issue the issue is that elderly people spend the vast majority of their time indoors and some because of their situation and long-term care residents don’t have an option they’ll spend their whole day indoors so one of the things that we have to concern ourselves is what should the indoor temperature limit be the world health world health organization recommends an upper limit of 32 degrees albeit there certainly recently looking at revising or have revised this recommendation now astutely i think looking back at what toronto public health recommended 26 a few years ago i think this was a a good call and certainly was based off of uh you know heatwave heat wave uh heat event uh data on on mortality related to a heat event uh in ontario and quebec and i think that really uh set the stage for what might actually be an appropriate threshold so let’s take a look at that we are interested in understanding first of all what should that indoor temperature limit be so again to put it into perspective if we look at the humidity spectrum over here again you’re going to have the very hot condition that we’re going to test which is going to be around the 36 degrees temperature and we we’re going to test all the way down to the cooler condition which would be your temperate room uh condition so let’s take a look at what we see with rectal temperatures so our elderly patients aged 70 to 80 were not isolating the calorimeter this time it was a large chamber so they had a bit of a bit of more freedom but they did sit there all day long and there were clinical tests done throughout the day and you see here we had them exposed on one session at 22 26 indoor temperature limits suggested by toronto public health one degree celsius just below that of the who and 36 now these are temperatures again that are not uncommon within the indoor temperature environment as i said in detroit maximum temperatures did reach 35 and we do know that some homes you know that these temperatures can even move higher so these are realistic values and when we look at that story just to go back what we do see in terms of core temperature when we look at the blue line is that we essentially see that it’s pretty stable there’s really no increase in hyperthermia for the individual and same for the 20 26 degrees celsius or the toronto public health recommendation but when we migrate or move up to the 31 degrees celsius we clearly see that there’s an excursion core temperature over that day long exposure they do achieve heat balance at some point certainly the 36 it’s much higher now it’s not that that core temperature is dangerous by itself for that single exposure and that’s something to remember what’s important is that that same core temperature at 36 or even at 31 degrees is the equivalent that you might even see during exercise if i take that elderly person and do a low to moderate intensity exercise i will still see that excursion core temperature about that same magnitude the challenge is that that is a burden on somebody when they’re exercising it’s no different when you’re exposed to heat that creates a physiological burden that if sustained can create heat induced fatigue heat exhaustion and other factors even though it’s a low level of hyperthermia so let’s take a look now at the uh heart rate response what are we seeing we’re essentially seeing that the burden placed on the heart if we look at the cool to the hotter condition the burden placed on the heart becomes greater and again imagine why is that well again remember that when we generate heat the system is trying to increase blood flow to the skin and to do that obviously it has to dilate the vasculature in doing so now to maintain blood pressure the heart has to work harder to maintain perfusion through those through that vasculature so the heart is working harder so that means for an elderly person who may be sedentary that can lead to fatigue and distress what about blood pressure well this is a very interesting observation because in our day-long exposure especially in the elderly people what do we see it’s surprising to see that even in the most extreme heat condition you can see here in the cool condition normal blood pressure and then there’s a real gradual fall even at 26 degrees in a person’s ability to regulate blood pressure in these two patients over here we observe collapse in these two individuals what we do see in this day-long exposures is that the elderly adults really don’t recognize the fact that they’re hypothermic it’s not until very late in that the seventh hour that they start to show signs of distrust that they start to recognize that something is not going right here most of them don’t feel that that level of heat stress they’re just not sensitive to it and we know that that happens and also one other clinical test some of you might notice a 30 to 15 ratio which is essentially an evaluation of changes in heart rate is which is performed uh in initial phase of adaptation to an orthostatic stress so you’re looking at the maximum minimum response and heart rate and what you’re really trying to understand is the activation of the central nervous system to a stressor so going from press to upright can lead to syncope and we see that dramatically here so we see that even at 26 while we may not see that level of hyperthermia we’re seeing an impairment in somebody’s ability to deal with these kind of stressors now why is that important that means that potentially during an extreme heat event somebody could collapse fall as a result have a hip fractured hip or fractured skull uh it’s not impossible so we do see that below 1.04 that is considered a significant uh dysfunction in their ability to again uh maintain stable posture so we can see that over here all right let’s migrate to potential heat mitigations and i know that many of you have been advocating for the use of or you know promoting the use of cooling centers and i think that’s extremely important we’re talking about using air conditioner in and again not everybody has air conditioners in fact they’re in many individuals just do not have access we know that in quebec in ontario long-term care residents 90 of them do not have air conditioning sadly enough they’re relied only upon access to a common room to get any form of cooling and again i think the the challenge here is really trying to understand the the the the benefits of of a cooling center just to what extent does it actually help protect the vulnerable let’s take a look we do know that it’s any form of adaptation heat mitigation strategy is is beneficial because it lowers that risk but we need to understand exactly what the benefits are so looking at the work that we’re just in the process of completing again we just completed this work again in partnership with health canada what we did here if you can recall the the the tracing i showed you earlier during the nine hour exposure within the calorimeter the patients were then at a separate group was exposed to at midway to a three hour or two hour cooling period as you can see over here which then they re-entered the calorimeter at extreme heat and so what’s important to see here and this is important again we do have the calorimeter-based data that gives us body heat storage what we see here is a rapid decline in core temperature they’re not cooling period but let me say one thing when we’re looking at heat storage and the difference what a calorimeter does imagine if i can infuse 100 marbles into your bloodstream now the calorimeter will be able to tell you that there’s a hundred marbles in the in your body now if i was to insert a rectal probe and it is able to sense these marbles it might say i recognize they’re probably 35 around the vicinity unfortunately it doesn’t know where the other it doesn’t know that there’s a hundred it can only tell you that there’s 35 so it actually is only a surrogate measure of the amount of heat stored in the body so while core temperature is going down here i would tell you data that you’re not seeing is in fact there’s still a huge residual heat load here so core temperatures in park going down because the skin is cooling and and just how the blood is redistributed causes this slight drop in or a marginal drop in in core temperature but that said it’s still a drop and it’s still protective and what we do see unfortunately is that the minute they get back into the heat the rate of increase in core temperature is much quicker than it was before the exposure so while cooling centers are effective no question it will also help uh reverse that cardiovascular burden you have to remember as well that you have to provide guidance to the patient because if they go back let’s just say they’ve come from the cooling center and they’ve walked there and they walked back in no time at all by the time they get back home they’ll have that core temperature will have gotten even higher or even faster to uh increase to a greater rate so we have to be careful and explain to the patient that that benefit may be short-lived let’s transition to exercise we’re going to look at that how how heat stress will affect workers or just people engaged in physical activity one thing that we know is in the act of having appropriate thermoregulatory abilities and that means to increase skin blood flow and increase sweating it would not take long for the body to reach very elevated temperatures that essentially would uh kill you so it doesn’t take long so but you have to remember that as we age unfortunately we’re going to see a deterioration in that capacity when we get chronic disease or when we are sedentary so let’s take a look at that so one thing we have to remember and i’m going to talk today just again in the context of occupational heat stress we have an aging workforce and we have extreme heat events so i want to talk about this but it still applies to those that are physically active in the heat one thing that we know unfortunately as we get older as i’ve discovered myself over the last two decades it doesn’t matter how much i train essentially there is we’re still combating the effects of aging across our various physiological systems that there’s a gradual deterioration well the same holds true when we talk about a thermal regulatory capacity so ultimately with aging where performance is reduced the problem is is extreme heat exacerbates that quite profoundly and essentially that can create significant problems to a worker now the challenge we face today and i see it across many industries certainly the mining industry the electoral utility industry we see an aging workforce and that’s seen across europe is seen across northern the united states and across canada and that becomes a problem because as i’m going to show you aging is associated with dramatic reductions in the body’s ability to dissipate heat and as you’re going to see it’s an important point to consider especially in view of existing guidelines which don’t offer the level of protection to everybody that’s necessary to safeguard their health and well-being so many of you probably have used different indices to recommend the different indices to industry to use in terms of helping them monitor their workers some may use for example the acgh uh threshold limit or action limit values and these are what you’re seeing over here so essentially these these uh exposure limits are based on temperature clothing worn and the work intensity and it gives you a very specific exposure limit that you should adhere to at least try to adhere to to prevent potential dangerous increases in core temperature so what do we know about these guidelines the problem with the guidelines is that essentially it’s a one-size-fits-all approach these guidelines do not consider the age of the worker the sex of the worker the state of health of the worker their sleep state number of consecutive days that they may be working and other factors that essentially can compromise their capacity to dissipate heat these are real factors that play into how we should be monitoring our workers so where’s the evidence to say it doesn’t work well a number of years ago we undertook that challenge uh we essentially did a first scale study looking at uh older workers uh workers uh just under on our mean average age of around 60 years old 58 to 60 years old and we assess the acgi htlvs uh and what we’re looking at here again is uh the uh what we have here is we use modern intensity work in this trial why did we use modern intensity well we’ve conducted years of field work and electrical utility across north america texas uh arizona different areas across north america as well as in canada and we also assess workers in the mines and we know that on average the during a day-long work shift it’s roughly the largest proportion of work done is moderate intensity work so we want to sort of simulate that and what we did is we assess workers using a simulated work model in using the the the work to rest ratios or continuous work inside a calorimeter so we can measure very precisely and the first challenge was we did the continuous work so you see over here that essentially again exceeding that bar would be again the the the the limits that would be suggested by the acgi guidelines being or the world health organization when you exceed it by degree then you’re potentially putting your worker at risk again what you see in the young individuals here after two hours and that’s the open bars here the white bars you see that on average most of the younger are protected but the older is the gray bars over here for this condition you see the vast majority are not protected now the reason you see the four hours is is an extension based off the rate of heat storage and the reality is because most workers again might do a pre-lunch work shift so that’s four hours take the lunch and then go off for another four hours based on those projections you can see that even young would be at risk certainly the older would be experiencing moderate to severe hyperthermia of course some of these are just not you know these are theoretical by based solely on the rate of heat storage but even when we go to the work to rash of three to one which if we increase wbgt you can still see again that the young work generally protected but the older are not and again this raises many questions about the ability of the of the these existing guidelines to protect the most vulnerable so what about uh aging and this is important so before we move it forward anymore i want everybody to think about if you’ve ever taken an exercise stress test a vo2 max test you want to test your fitness you’re all excited about doing it and you go out there and you do a treadmill test right so if you’ve done a vo2 max test you know what it’s like or if you’ve had a heart check to verify if you had any heart conditions you’re going to do an incremental exercise test and the purpose behind that essentially is to measure your aerobic capacity the maximum ability of your of your of your active tissue to utilize oxygen during exercise so using a very similar concept we developed a test that’s conducted in our calorimeter that essentially allows us to measure the body’s maximum capacity to dissipate heat and we do it as an incremental model but this is a little longer it’s not these two minute increments up to 10 to 12 minutes this is a 90 minute test so you do 30 minutes at light 30 minutes at moderate 30 minutes of vigorous with 15 minutes of recovery and by doing that you can compare groups and see at what level of heat stress do you see impairments and what is that physiological capacity dissipate heat so based off of this we have here the data that looks at the effects of age and we’re looking at the lifespan here so you can see we have women in red men in blue and you can see them here the responses in moderate to vigorous where we see a difference in age-related effects are when we get to moderate to vigorous work and you can see the age-related decline across the lifespan in adults age 18 all the way to 70. and what we do know is that essentially that decrement in a person’s physiological capacity dissipate heat is about uh four percent and in women it’s four percent lower now why is it diff it is not it has to do with the end organs themselves the skin vasculature and the sweat glands that differ and they the different the mechanisms of control that’s why we see slightly lower uh capacity dissipating women so when you look at modern intensity work if i was to do intermittent work this is the effect an older stores this much more heat relative to younger for a modern intensity exercise boat now again coming back to the idea we can’t forget even though we may do studies in dry heat conditions we can’t forget the superimposing effects of humidity when you look at for example 30 oil performing exercise in dry heat this is how much heat they’re storing that’s how high core temperature will get but way higher 1.5 fold greater in a humid condition and you can see just how how how much hotter an older person will get when performing uh in in dry versus humid heat now in context of aging one thing that we do know is fitness matters and this is something that i’ve been advocating across the board when i speak executives across different companies about the importance of using uh you know health training programs or health programs because it’s important having people engaged in vigorous exercise is important because it can offset age-related changes case in point in this work that we showed that essentially if you take a middle-aged trained person and compare them to a habitually active worker they have the same response in terms of their capacity to dissipate heat so they have the same core temperature during exercise in the heat however if i have a trained 50 year old person and an untrained what you’re going to see is that untrained person actually responds very similar to an older active individual so fitness matters in the context that it will improve your capacity to spat heat and we know that exercise has a myriad of factors or benefits on other physiological systems what about diabetes so i’m older i have diabetes how’s this going to affect well in our first study a number of years ago we assessed the heat loss responses in patients that were relatively sedentary so we did a load of modern intensity work was relatively low but you can see that after the 60-minute exercise they stored more they stored more heat relative to their healthy counterparts the white bars that’s the area in pink that’s how much more heat they stored now when we assessed and did a subsequent study later on and looked at the physiological capacity to dissipate heat so it’s just like doing your vo2 max what was their aerobic capacity well what was their maximum physiological capacity to speed heat we saw that was 20 percent lower that’s huge that means that essentially i can do less work or i can be exposed to to a high heat stress condition for less time now importantly these have huge impact effects on work performance so let’s translate this information now to the worker let’s go back to again the acgih guidelines we just looked at them earlier uh in this large scale study that we just finished and published what we did is we assess how workers will respond under six different ambient conditions now we used in this case here again moderate intensity work we use a wbgt of of 25 as that sort of threshold and we compared responses in older young older adults with type 2 and older adults with hypertension a subgroup also did the conditions in the light gray area so we had a condition that would be above so the 24 and 16 were below the uh the action limit threshold for continuous work which was 25 wbgt and we had conditions above that and why is this important number one this work is important because a number one we see that if we look at our work in the intellectual utilities as well as mining the vast majority of workers always exceed 38 degrees in fact in some of the workers that we tested in in texas we saw a number of them reach love of 40 degrees doing their work outdoors so it’s a problem and the problem is how this can affect the older worker so let’s take a look so in this work we want to understand just how workers may be affected so what you’re looking at is a wbgt below the recommended action limit value so that means it should be safe if they were to perform prolonged exercise at a wgt of 16 or 24. well surprisingly we still see a number of workers even at 24 and at 16 that are essentially exceeding this one degree upper limit again again the guidelines are there to limit the increase in core temperature above one degree again you’re going to see excursions above one degree during a work session that’s a given it’s just you don’t want to sustain it there these are sustained increases above one degree and this simply shows you the proportion of workers in both conditions that exceeded that wh or the acgih upper limit okay so very simple graph so over what the workers did in this in this trial is the exercise for three hours so it’s like doing the pre-lunch period and we use moderate intensity to reflect the same kind of measurements that we’ve seen in our own field work but again you see there’s a risk as well and that some will still be seeing increases in core temperature okay reality will be and the reality that we’ve seen when we’re out in the field is we see a lot of workers that are obese we see a lot of workers that have type 2 diabetes we see a lot of workers that have hypertension that are older the problem is is that it’s not feasible to always be using the acgi guidelines and sitting down there and looking at a temperature and say oh i got to reduce my exposure time because when you’re out there in the work what you’ll see is the sun comes from behind the clouds maybe it’s under the behind the clouds for uh for 30 40 minutes maybe now you’re working be behind beside a a truck or an engine that’s generating heat things are changing all the time it’s not as simple as simply you know looking at a chart and revising your work effort so when we’re doing continuous work in the heat we have no option one of the things that we’re interested in understanding is what is the safe work limit when temperatures get hot for uh older workers and those with chronic disease so what you’re looking on the left is the safe work time and on the right to tolerance time so what are the differences walk through it with me down here so safe work time refers to the duration of work before each worker experience a sustained elevation core temperature exceeding recommended limits of one degree now the difference with tolerance time is that it indicates the duration of work performed before complete completing the 180 minute work period or terminating prematurely due to the participants requests valiant over fatigue or if core temperature exceeded 39.5 so the reality will be if you had a worker that had to go out there and that’s not unlike what we see in the mining industry mining industry you know they’re working at depth it gets extremely hot they’re working in unventilated air they’ve got to do the job and sometimes it requires that they be there continuously they can’t just stop if they’re laying new line electrical lines in an emergency they have no option they can’t just stop and take a break the work has to be continuous and what you see is that the safe work times drop dramatically as you get into more extreme heat conditions and again these are the 32 are very different from the the the 28 you can see that the safe work times drop dramatically and again when we look at tolerance we see very different responses in in the three groups you have your over here you have your you’re older you’re young you’re diabetic and your hypertensives so let’s finish off by looking at these uh last few things what about diabetes so what we’ve looked at thus far is is is and i was telling you about the physiological capacity dissipating and the type 2 diabetic is reduced now this was done in semi-nude conditions now we have workers they’re encapsulated with their work uniform let’s see what happens well see that when we compare the hot conditions and temperate condition we see that tolerance time goes down you can see that over here difference from temperature and exercise tolerance but here’s something to remember core temperature not different heart rate not different how does this make sense glenn when you just told me that a patient with diabetes has a reduced capacity to dissipate heat higher core temperature well let me explain to you you have a worker that essentially is now wearing coveralls so a healthy worker may sweat more that’s fantastic they sweat more but unfortunately that sweat doesn’t evaporate because it’s encapsulated within that uniform great sweater they’re gonna get their clothes gonna get a little more damp unfortunately that doesn’t help them so what you’re seeing is because of the uniform impeding heat loss is somewhat of an advantage to that more vulnerable person because even though they may be sweating less the person that is probably of somewhat vulnerable is going to be that that older person because they’re not benefiting from that sweat they’re going to dehydrate more properly so one thing to be careful of if you’re monitoring workers using heart rate that may not tell you the whole story if you’re monitoring core temperature that may not tell you the whole story because they have the same core temperature the same heart rate yet their tolerance time is completely different and you’re going to see that your patient with type 2 diabetes is likely to collapse earlier and same applies with hypertension so if i take the semi-nude and look at their capacity to dissipate heat the only difference here is that we did not see any differences in capacity dissipate heat in a patient with a hypertension and this is again controlled uh uncomplicated hypertension but what we did see when we have them dressed in their uniforms and doing prolonged work we did see again a reduction in tolerance time and we also saw that they had the same core temperature and heart rate so if you are monitoring workers that have hypertension it’s important to understand that while they may have the same heart rate response to doing the same work they’re greater risk of collapse all right and again this means that if we are going to down the road look at making you know readjusting or realigning our exposure limits we really have to think about how we should make those adjustments for the most vulnerable and that may be lowering that threshold so i want to finish off my last slide folks i guess i want to ask the question can we adopt that’s a great question can we adopt exposure to summer what our study showed after looking at a person’s capacity to dissipate heat again conducting the calorimeter pre-summer so this is done before the summer starts post summer you see that there’s an older person stores way less heat post summer so their capacity dissipate heat increases however i want to remind you that during the summer period temperatures get hotter so even though there may be some adaptation remember that the level of heat stress is also rising so that adaptation still may not be sufficient to protect the vulnerable even in the most extreme conditions what about a worker how do we protect workers well in in this study here we showed that when we expose uh older adults to seven days of consecutive work in the heat so exercise in the heat expose them to high core temperatures that they can improve their capacity dissipate heat surprisingly in this paper we published in jama we showed that we can reverse disease-related impairments so patients with diabetes had an even greater increase in their capacity to dissipate heat which was quite surprising so again there’s ways in which we can help workers improve their capacity dissipate heat so that they are able to compensate more easily ultimately that would mean lower temperatures so finishing off i want to thank again my partners at health canada who have provided great support for all this research and again we’re together working to create these heat resilient communities and workforce so thank you very much for your attention great thank you dr kenny that was a really fascinating um studies a couple of studies um and i’m just we have a few minutes left uh just wondering if the audience has any questions for dr kenny if you do please type them in the chat box or feel free to um unmute your audio and raise your hand and just as we’re waiting for questions i’ll just uh put the poll results up i don’t know if you were able to see this um but our first question was asking where the audience was joining us from um and it looks like we have a few from the atlantic region many from central canada and the prairies and also the west coast um and with the majority of the audience working in public health or for provincial or territorial government and ministry uh and also in education and research and over half of uh the respondents work um uh with uh in their organization’s uh emergency planning in relation to heat so the first question we have is what uh do you have any evidence of differences in tolerance for young children versus adults that’s an excellent question um we we were tasked with assessing that response um from health care with health canada and one of the things that again there’s such a lack of of data assessing uh responses thermal regulation in children and there’s mixed results in terms of our children that are at greater risk uh the evidence and we do review this in great detail in a review that was published in in medicine science sports and exercise just i think just over a year ago that there’s a real lack of evidence that suggests that children are at greater risk you know there are suggestions that essentially they may have a sort of an image term or regulatory apparatus or system but that is not necessarily true in fact we do see and we did a field study assessing heat stress in children which is also available for uh open access that you can you can search out but again we did not see differing responses in terms of their their tolerance to heat so i think there is a need for uh confirmatory studies in terms of looking at capacity dissipated heat uh you know physiological based studies because i do think that’s important but uh as far as based off the evidence that we have again it’s it’s kind of mixed findings okay thank you for that um and the next question is what made our recent bc heat dome driven event that that much more dangerous was persistent persistently high nighttime temperatures with respect to guidance of using cooling centers might that mean a policy change to enable accommodation for 24-hour operation at those centers an issue is also getting people their elderly people tend to want to stay close to home regardless of what it’s like yeah and it’s a great question because again you know um having my mother in long-term care uh and having had the opportunity to see the the effects of that and the extreme temperatures in inside her room um you know in in the way that the patient is is you know brought to uh the the common room to get some cooling the challenge that we have with cooling centers is that essentially what we don’t understand is what is the ramifications of exposing somebody to a cool room you have to think about the effects of this and i want to give you an example of workers what is advocated across the united states and i see quite commonly amongst workers is that after they’ve if special electrical utility workers that we’ve assessed they’re so heat stress and what they do they immediately after they get they finish uh doing their work their pull work they get into their into their trucks and they run the air conditioning think about this what happens is you’re not losing you’re essentially shutting down all of your thermoregulatory system you’re shutting down the sweating response you’re causing vasoconstriction so all you’ve done is essentially now create this the your restricted heat loss so it may be down the road when we look at these different models which we’re going to be testing soon is assessing just how much exposure should be and should we actually be using perhaps slightly warmer temperature to continue to activate the heat loss response while at the same time providing some cooling benefit because again when we look at workers the minute they go back into the heat they essentially see the more rapid increase in core temperature and it actually pushes them much higher so you’ve had that residual heat in the body and now you’re adding on to that and you can see this this after rise so this is why i think you know we have to really re-evaluate how we implement uh you know our practices towards using cooling centers and the other thing that we have to remember is even just walking to a cooling center now the adult will cause them to store a heck of a lot of heat so by the time that they’ve actually gotten there sat down and left they probably only lost the heat that they’ve gained getting there that’s probably what’s happening see um great um and we have maybe time for uh one more question there are more questions but uh email them to you later uh the next question is what are your recommendations to employers regarding ways to mitigate heat stress yeah and in one of those again it’s it’s uh and i was having this discussion before the presentation and i’ve had talks with company company owners in the united states as an example and surprisingly what i get is that heat stress is not a problem because nobody’s died i want to again indicate that one of the biggest problems we face is understand the effects of heat stress in workers and also implementing appropriate heat mitigation especially when you know workers may not have the luxury of being able to stop work because they have time constraints on them so in terms of of of uh being able to mitigate the the effects of heat stress the one thing again in those kind of working environments is using the buddy system because there’s no better way of understanding you know how workers responding by having somebody who knows that person well the one thing i can tell you having tested thousands of of of of people including workers is that the one thing you see is a change in behavior before you even see that level of hyperthermia that’s going to affect them you begin to see an isolation of that person in terms of how they’re doing their work they’re they’re they’re ignoring all of the safety uh rules so one of the things to do as well beyond just monitoring because that can be ineffective as we saw today without appropriate understanding of the of the worker what you know what their health status is what their age may be is to really try to to understand the worker over time so if you have a worker it’s a document information and essentially if you know that you’re going to have extreme heat then maybe it’s to create a double team and to and to essentially plan out you know those more intense works and have another team come in and play that in and out like that as opposed to having one team going in so there’s a lot of different excuse me different strategies that can be used that’s great those are great considerations um and we do have a couple more questions but i think that’s all we have time for right now so if you don’t mind um i will email you those questions and could answer uh yeah we could post the answers back to everyone thank you again dr kenny and everyone thank you for joining us for this great webinar and the evaluation is available in the chat box right now but i will email that to you later on today as well and if you have any questions please feel free to email and uh thank you for joining us again and have a great rest of the week thank you everybody thank you bye
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Protecting the health of Canadians and Canadian workers on our warming planet

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