Extreme heat and human health

Surviving (and thriving) in a warming world

What is the impact of extreme heat and hot weather on human health across the human lifespan? How can we thrive in a hotter world? In this Sydney Ideas event, experts from the University's Heat and Health Research Incubator discuss the latest research and provide us with some pretty cool solutions.

Did you know that extreme heat and hot weather have devastating consequences for human health and wellbeing? Or that heatwaves cause more deaths than all other natural disasters combined? With our planet heating up, we need to find solutions for how society can not only survive but thrive in extreme temperatures.

Hear Professor Ollie Jay (Director, Heat and Health Research Incubator) in conversation with cardiovascular health expert Dr Georgia Chaseling, environmental physiology researcher Dr James Smallcombe, neonatologist Professor Adrienne Gordon, and host Professor Tony Capon (Director, Monash Sustainable Development Institute), as they discuss the effects of extreme heat on our bodies and its impact on our health and wellbeing across the human lifespan.

Learn about the current and future impact of heat and heatwaves on society including reduced physical work capacity and motor-cognitive performances, with consequences for productivity, and an increased risk of occupational health problems. 

Our expert panel explores practical ways to tackle the health and societal impacts of extreme heat with sustainable, low-resource, evidence-based solutions, and how together, we can build a more resilient community to a warming world. What could be cooler than that?

This event took place on 13 December 2022 at the Susan Wakil Health Building and live online. 

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Audio transcript

- Welcome to Sydney Ideas. The University of Sydney's flagship Public Talks program. As we begin this evening's event, let's all acknowledge the traditional owners of the land we're on today here at the University of Sydney. The traditional lands of the Gadigal people of the Eora Nation. And we acknowledge elders, past, present, and future. And indeed, we acknowledge traditional owners wherever we're assembling. Today, online. Today's session is about extreme heat and human health, surviving and indeed thriving in a warming world. I'm Tony Capon, director of the Monash Sustainable Development Institute and I'm delighted to be hosting the event here tonight. Welcome to all here in the Sydney University campus, the Susan Wakil building, the School of Health Sciences, and online with us this evening. The event's in two parts. The first part are conversation with panelists here and the second part, the Q&A segment. And we encourage you to be thinking about questions for the panelists as we proceed through the event. You'll also have an opportunity to lodge questions online using the slido.com platform. The QR code here or going directly to slido.com and using the code SydneyIdeas. We also are delighted to have a number of pre-event questions registered and we'll weave those into the conversation. Worth noting that tonight's event is hosted by the heat and health research incubator here at the university. We're into December and looking ahead at the Australian summer, we can anticipate a number of extreme heat days across the country. And this has important health impacts. Tonight's event is about understanding those health impacts across the lifespan and also thinking about sustainable and low cost solutions in the context of a changing climate. We've got four great panelists here tonight. Sitting next to me, Adrienne Gordon, clinical professor here at the University of Sydney and senior staff specialist at the RPA Center for Newborn Care. Let's welcome Adrienne. Next to Adrienne, Dr. James Smallcombe, research associate here in the school of health sciences. And James's research is about increasing human resilience to these extreme heat events. Welcome, James. Next, Ollie Jay, professor Ollie Jay directs the heat and health research incubator here at the university and his research focuses on understanding the physiological and physical factors that determine human heat strain and the risk of heat related health problems during work and physical activity. Welcome Ollie. And our final panelist, Dr. Georgia Chaseling, who's also a research fellow here in the school of health sciences. Georgia's research focuses on the impacts of extreme heat on cardiovascular outcomes among vulnerable people. Welcome Georgia. So Ollie, can I invite you to just open up and set the context for this evening's discussion?


- Indeed. Thank you very much, Tony. So I think it's firstly important for us to set the scene and really accept that we live in an era of a changing climate. This is backed up by clear scientific evidence which I'll illustrate in this slide right now. So if we classify the prevailing temperatures that occurred over a 30 year period in the decades between 1951 and 1980, we can categorize those days in terms of being cold, moderate, hot, and extremely hot. Using those definitions for that particular period, we then apply them to the prevailing climate that occurred between 2005 and 2015. We can see there's a massive shift in the number of days in which we would, using the same criteria, consider hot and also extremely hot. Indeed, by the time we reach the year 2030 to 2035, extremely hot is going to rapidly become the new normal. So why is this a problem? Increases in average temperatures from a human health perspective when we're talking about heat are not what is at issue. What is at issue is the increase frequency, duration and timing of extreme heat events. Heat extremes or otherwise known as heat waves. There's also chronic hot weather that people have to cope with for prolonged periods of time throughout the year in certain parts of the world, particularly more vulnerable parts of the world such as lower middle income countries where a lot of the products that we consume here in Australia are made. So we can think about the way in which human health and wellbeing is impacted by extreme heat and hot weather in terms of its impacts across the human lifespan. And it's really important for us to think about it in this context because the nature of those impacts are very, very different depending on what type of person we're looking at and what stage of life they're particularly at. And this is a lot of the work that we are looking at in the Heat and Health Research Incubator here in the Faculty of Medicine Health at the University of Sydney. So the impacts of extreme heat on human health start even before birth is very good, strong epidemiological literature that is described in increased risk of stillbirths and premature deliveries following extreme heat exposure of pregnant women. We don't understand the physiological mechanisms necessarily, but Professor Adrienne Gordon's here on the panel today to talk a little bit more about that context. As we progress into the early stages of life through childhood, we have Dr. James Smallcombe who's working on a national health and medical research council project grant, which is developing Australia's first evidence-based extreme heat policy for child and youth sport. And we know that the impacts of extreme heat and hot weather on the wellbeing of children have been quite profound over the past couple of decades. As we then get into adulthood, I'm here to talk with my hat on from the perspective of looking at occupational health conditions and then as we get into the latest stages of life, primary aging and then the interaction between primary aging and chronic health conditions also serves as a massive risk factor or combination of risk factors for negative health effects of heat extremes and hot weather. And we have Dr. George Chaseling to talk about that, particularly from the perspective of cardiovascular disease. Across the bottom of this particular slide, there's also a variety of other contexts that occur across the human lifespan, which are kind of summarize some of the work that we are doing here in the incubator. We won't have time to talk about 'em specifically today in the first part of this session, but if any questions arise related to those particular settings, would be happy to continue those particular discussions. Another fact that I'd just like to quickly flag is that it's really important that we start to really not just think about extreme heat and hot weather as an individual stressor that's isolated from everything else that we're experiencing here on earth. There are dual environmental stressors such as bush fires and we were reminded of that in the black summer of 2019 and 2020. There's also the energy concerns surrounding providing enough electricity to enable people to keep cool using conventional air conditioning units, particularly the most vulnerable who can't afford those, the prices of energy. And that's particularly pertinent right now as we're experiencing two parallel crises, one associated with energy prices and one associated with the longer term climate change. And finally, there's impacts of extreme heat and hot weather in terms of human migration in the future and also the secondary effects of extreme heat on water-borne disease and vector-borne diseases. And we're starting to do some work in the research incubator here at the University of Sydney, looking at some of those particular factors. Now, it's all pretty doom and gloom so far. Indeed, we had one registrant yesterday who submitted a question and it simply said, is there any hope? So we are here today to make sure that people leave with assemblance of hope. And this is the reason why we've established the heat and health research incubator here at the University of Sydney. This is a multidisciplinary research center which is bringing together people from a variety of different disciplines to generate comprehensive solutions to the most complex problems that we face as a function of extreme heat and hot weather, particularly in the context of a changing climate. We are focusing initially in the first two years of our existence on five priority research themes, which is summarized here on the slide. Climate change in health, physical and mental wellbeing, women's health, built environment and health and heat and health policy. I believe below each of those particular categories, there is a few dot points given examples of some of the things that we're working on in those particular areas but that's not an exhaustive list by any stretch of imagination. And we are building capacity as we speak and the people that we have on this panel is testament to that effort in the first year of the incubator. So we are gonna be focusing on solutions as well as describing the problems today. And that's, I think it's a really important factor when we're considering how we're going to address these problems moving forward and we encourage you to think in that context as well as despairing over the problems even though they are indeed quite profound. Very finally, I'll just quickly tell you about a very unique facility that we have here at the University of Sydney which resides on the ninth floor in this beautiful new building that was opened last year. I have the privilege of also being director of the thermal ergonomics laboratory which houses a state-of-the-art climate chamber, which has been custom built to simulate heat waves of the past but also of the future so we can better understand the impacts of different futures based on different climate change scenarios right now so we can generate evidence to persuade people to act before it's too late. That's all I've got for now. I'll hand over back to Tony. Thank you.


- Thanks very much for that terrific overview, Ollie. And let's now explore this a bit further. Drill a bit deeper into the specific aspects here. So let me invite Adrienne to tell us a bit about the context of pregnancy and the newborn.


- Okay, so I'm privileged to start at the beginning in life and on the panel and I guess everybody thinks that their area of research interest is the most important but the beginning of life is the most important because otherwise none of you are here. So we are interested through the incubator in research involving the impacts of heat on pregnant women and their babies in uteral and in the newborn period. So we know globally there are really important outcomes that occur for pregnant women and their babies that are associated with extreme heat. So every 16 seconds globally, a baby is still born across the world. 15 million babies are born preterm every year and that's the biggest cause of death and disability in the under five age group. There are other really important factors like being born too small, also hypertension in pregnancy, preeclampsia and gestational diabetes. And they are different pregnancies in different parts of the world. But every one of those key conditions has an association in systematic review data and epidemiological data with extreme heat. So we know that for every one degree increase in temperature, for example, the increase of preterm birth and stillbirth goes up by an odds of about 1.05. So that's a 5% increase. And if you think about those numbers, a 5% increase on 15 million is something that we're definitely gonna want to try and understand a little bit more about. And one of the interesting things and what we're trying to do with members of the panel is to really try and work out why. So particularly for pregnancy, there's a lot of assumed knowledge. There's a lot of things put on pregnant women that they can't do or they've never been able to do or they've been restricted from doing. Much of that is not based on true physiological data. So there are concerns about physiological capacity in pregnancy and there are definitely some things that are true that you feel hotter when you're pregnant and you generate more temperature if here are two people. But there are concerns about things like reduced capacity to sweat and if you are trying to sweat and you're pregnant, might you direct blood flow away from the placenta to your skin. But a lot of those hypotheses haven't really been tested and until we get more understanding about that, we won't be able to really inform really good solutions. So I could talk a lot more but I'm not gonna take away from the rest of the panel.


- Yeah, no, well thanks very much for starting us at the beginning there Adrienne. So next to James to ell us us a bit about childhood in this context.


- Yeah, thanks Tony. And like Adrienne, I'm also a little bit biased but I think children also provide a really interesting population in the context of the issue of of heat and health. And not least because there are so many different settings in which children can be exposed to extreme heat. Now this can start right from the beginning being pushed around in a pram or a baby stroller during the early years of life. And then we advance into the, you know, the time when children and adolescents may be participating in structured youth sport on a Saturday afternoon in the heat. Or children even may find themselves in very uncomfortable hot classrooms whilst at school during the summer months. Now with this in mind, children have often been classified and often assumed to be a vulnerable population in the context of heat and it's suggested that children are much more likely to experience adverse outcomes when exposed to heat stress. Now if this is really the case and children are more vulnerable than adults to extreme heat exposure, it poses a number of very interesting questions as to why this might be the case. Now is it a question of or is it a case that children may be somewhat physiologically disadvantaged compared to the adult counterparts or is it more to do with the way that, or the different ways that children behave in comparison to adults? Now, it might not be as simple as one or the other and it's likely a combination of these two factors but these are some of the questions that we're currently trying to tease out here at the University of Sydney. Now, if we just for a moment touch upon some of the possible physiological reasons that a child may be more vulnerable to their heat, it goes without saying that childhood is a period of huge growth development and maturation. A child's body changes rapidly during childhood, both in size and shape and the physiological systems are also still developing. Now with that in mind, it has been suggested that a child might have a lower capacity to thermoregulate compared with the adult counterparts and particularly in their ability to sweat. And as we all probably know, sweating is one of the major avenues through which we dissipate body heat as it evaporates from the skin. However, some emerging evidence, some evidence that's beginning to emerge from our laboratory. Currently, we're working on a big, big project that sees children come into our state of the art climate chamber to exercise. It appears that the children maybe aren't physiologically disadvantaged compared to the adult counterparts. They seem to be able to sweat just as well and they seem to be able to dissipate their body heat effectively. So this begs the question whether it is perhaps more of a behavioral issue. And examples of this is, it comes down to this notion of whether children have the cognitive ability to make good decisions when exposed to heat stress. Now, examples of this might be understanding the need to wear less clothing when out and about in in hot weather or reducing the number of layers of clothing. Or it may come down to this, their ability to down-regulate the intensity of any given activity that they are performing under heat stress conditions. And it's also probably worth bearing in mind that children are often very heavily dependent on adults to make good decisions on their behalf. So examples of this might include the youth sport coach that has the, who has to make the call as to whether the environmental conditions are appropriate for play to continue on a Saturday afternoon or the teacher that is making the decision as to whether it's safe to send children out to play in the playground during periods of extreme heat. So I think it's this unique combination of these potential physiological differences and these behavioral considerations that make children such an interesting population.




- Yeah, no, thanks very much James. Certainly a lot to explore there, isn't there? Now Ollie, tell us a bit about the adult context including work.


- Yeah, so thank you Tony. And thank you Adrienne and James for your contributions. So I'll keep it relatively brief because I've spoken quite a lot already and we wanna make sure we have lots of time for questions. I think the way in which occupational heat stress is evident, it's important for us to think about the context. So if we first look closer to home, what are the impacts of extreme heat on occupational productivity in Australia? There was a paper that was published in Nature Climate Change in 2015 by an international research group and they estimated that the impact of heat on the Australian economy was north of $6 billion a year. That's with a b. And this was predominantly through, not through absenteeism but through presentism. And this is a phenomenon where in order to try to prevent from yourself from overheating if you're, it's an exertional job that you're engaging in, what we tend to do is that we slow down, owing to the fact that we can reduce the amount of heat that we're generating inside the body. And that in its, in and of itself is a behavioral protective measure to overheating. In an office environment, if we start feeling uncomfortable, then we know that that's going to alter the way in which we are going to be productive in an office-based workplace environment. Of course, the solutions maybe focused on things like air conditioning, et cetera. So, but I'll talk about that and the issues associated with that a little later on. If we look a little further afield in an international context, particularly in lower and middle income countries, the dynamic changes quite significantly due to the changing nature of labor law settings. So in Australia, we are protected quite relatively well by labor laws which prevent exploitation in the workplace in most cases. In some other countries, this is not necessarily the case because often people are paid by the unit of productivity by the bushel or by whatever output they're generating from that particular job. So if we think about that and then we think about the way in which we naturally behaviorally defend ourself against extreme heat in a workplace, then we realize that we slow down, we'll get paid less. So then there's this cost benefit analysis that a lot of people will be doing is either they slow down, protect themselves against extreme heat and they have to work longer to get paid the same amount or they try to ignore those signals that their body's giving them to tell 'em to slow down and they push forward and that's when they're exposed to greater risk of maybe not heat stroke but certainly along the spectrum of exertional heat illness. And there's a lot of great work that is looking at generating some evidence that's supporting that particularly for my European colleagues which have been part of the European heat shield project, which James was actually a part of before a just here at the University of Sydney. And maybe we'll touch on some of that information a little later on. But I think it's that context or that concept, beg your pardon, of climate justice. People who are responsible for contributing the most to climate change often don't feel the consequences as much of those who can contribute less. And that's certainly so in an occupational context. I won't talk anymore 'cause I wanna reverse allow more time for everyone to speak.


- Yeah, well thanks very much, Ollie. And I know in the incubator, you're doing really interesting work. I think with support from the welcome trust in Bangladeshi garment factories that's very relevant to this work context. So let's come now to Georgia to tell us a bit about aging in this context and including cardiovascular disease, yeah.


- Yeah, thanks Tony. I think continuing the trend on looking at the negative effects of heat on population wellbeing, I'm interested in looking at the association between extreme heat and aging and chronic disease as well. Unfortunately, a lot of increase in hospitalizations and mortalities that we see during extreme heat events do occur in adults over the age of 60 years old. And we see about 80% of these deaths are due to cardiovascular risks. People who do have cardiovascular disease are at an extremely increased risk of going to the hospital or unfortunately mortality during extreme heat events. And again, continuing the trend of understanding why we don't really understand the mechanisms that can explain this increased risk. So a lot of the work that I'm interested in doing is trying to understand why these individuals are at a greater risk and what can we do to absolutely protect them from harm during extreme heat events. So I don't think I need to touch on that much more .


- Great. Well look, thanks very much. I think you've given us a good overview of the, this life course understanding of heat and health. And as Ollie said earlier, we want to now get to the hopeful bit about what are some of those potential solutions, including those sustainable solutions that are lower cost, lower carbon solutions in this context. So perhaps beginning again at the beginning of life, Adrienne, tell us about what we know about solutions in pregnancy and the neonatal period.


- Yeah. So I think, I guess the first thing to say is we don't know very much because pregnant women are continually excluded from randomized trials or clinical trials because of the nature of being pregnant. And we've seen that most recently with the Covid pandemic. So I was part of the national task force for living guidelines for the country, for Covid. And you know, so much evidence coming out every week, no pregnant women included in any clinical trials, tiny percentages, no data on safety and really didn't get included in all of that work until it was about safety of vaccination. So I guess the first thing to say is if we're gonna have solutions for pregnant women, we need to include them in research and we need to include them in clinical trials. We also need to understand, as I said earlier, a little bit more about the unique physiology in pregnancy and what is different and what might not be so different. But we have thought it was. So James and Ollie have led a climate chamber study that was published a little while ago, randomizing pregnant women in the ergonomics lab to different temperatures and actually found that up to about 32 degrees, there was actually no thermo regulatory impairment. So some of the reasons that we don't include pregnant women in such studies might actually not be true. And now that we've got better ways to understand that, I think that's a really important place to start. I think some of the solutions will come down to things like policy that might affect work habits and culture for pregnancy. In many countries in the world, pregnant women are the workforce, particularly in rural or subsistence areas where they're often doing a lot of the farming, they're doing that right up until they have the baby, they're doing it afterwards with the baby on their back. So there might need to be some very low cost solutions to actually maintain a workforce but do that safely. So I think we've got a long way to go and I think we can follow some of the solutions and work that's happened in other populations, but I think it's a very important population to start including.


- Great, thanks Adrienne. And I think that's a really terrific message about this heat and health research incubator here at the University of Sydney. That it's really challenging some of this received wisdom in our understandings of relationships between heat and human health and the kinds of solutions that we need to be exploring. So James, the context of childhood, what are we learning in that context?


- Yes, absolutely. And just before I move on to to children, I think it's just worth touching back on the study that Adrienne alluded to the, it was a really interesting study. We got about 20 pregnant women to come and exercise in the climate chamber and despite them exercising for 45 minutes at a pretty moderate intensity, that their rise in core body temperature was no different to non-pregnant women. And importantly, these pregnant women got nowhere near what is thought to be the critical safe threshold for core body temperature. So this is, to us was good evidence that women can safely exercise in the heat.


- [Tony] Mm.


- Which I think is a, you know, a very useful finding. Moving on to the context of the pediatric population. Similar to the pregnant women, I think the take home message is there's still quite a lot of work that needs to be done but the good news is that over the last two years, we really have kick started this line of research in the thermal ergonomics laboratory. As Ollie alluded to, we currently hold an HMRC funded project which is designed to systematically examine the thermo regulatory responses of children as they develop through childhood and into adolescence. And the real aim here is to establish whether their thermo regulatory capacity changes with advancing age and if so, how these responses may differ to those of adults. Now, the big picture kind of side of this project is we hope that these data will help us inform an evidence-based extreme heat policy for the youth sport in Australia. Now we are, you know, working on this behind the scenes and our ultimate hope is that next, early next year, this will be rolled out in some kind of app form which end users can log onto, whether it be coaches or parents, select the type of activity the children are likely to be engaging in, and then based on the prevailing environmental conditions at that time, we can provide an overall risk score for youth sport, but also essentially evidence-based strategies that coaches, teachers, children can employ to help keep children both cool and safe during periods of extreme heat. And I'm not sure whether the app is something that Ollie might like to discuss in a little more detail in a slightly different context.


- Yeah, no that's great. Well thanks very much, James. And maybe at this point, just a reminder, here's the Slido QR code and I can see that questions are coming in, which is great. So thank you very much for that, James. So back to adulthood and yes, that work context, yeah.


- Thank you, Tony. Yeah, so I'll just briefly touch on two things and the way we'll categorize them are changes in policy, so work that's been done in that context, then interventions that can be used in the workplace that don't contribute to the problem further down the line. So first of all, if we focus on policy now, this is not necessarily work that we've done but good colleagues of ours have done in Europe. And probably the best exemplar of this type of work is some work that's been done by a colleague of ours in our field called Andreas Flores who's worked in Qatar trying to better characterize the impact of extreme heat on occupational workers in the preparation to the World Cup, which is taking place right now. And obviously that's very well documented, the impacts that that has had in terms of worker mortality. And what Andreas's team did alongside a bunch of other colleagues as well is that they tried to better understand what the problem was. They then used physiological evidence from people who understand how the human body thermo regulates and implemented that in the context of changing changes in work policy. And they've got some really strong data demonstrating really quite a dramatic reduction in workplace mortality and morbidity due to extreme heat since the implementation of those policies. And those policies might be something similar as ensuring that there's adequate breaks for recovery of body core temperature, adequate opportunities and supply of hydration. Some other work from in Copenhagen where they've demonstrated that agricultural workers in Europe often arrive at work in a dehydrated state already before they even start work and are exposed to these extreme heat conditions. So the provision of resources that enable people to maintain their thermal regulatory status, it might seem simple, but ensuring that these are embedded in policy is a really powerful way of ensuring that it's translated to changes in health outcomes. And I think that's a really nice example. In fact, some of that work was featured on the cover of Time magazine just before the start of the World Cup. So congratulations to them. In terms of interventions, one thing I would like to talk about is this notion and people who know me will not be surprised that I'm gonna talk about this, is this idea of moving air more and chilling it less. We've been quite preoccupied for a long time now thinking that the only way to cool the human body is by reducing the temperature that of the air that people are exposed to. But we exchange heat with the environment through a variety of different pathways. And one of them is a process called convection which is accelerated by air movement. And what it means is that you can lose the same amount of heat, feel pretty much the same thermal status but with a with a warmer temperature, with a higher air flow.


- Just demonstrated actually .


- And through a simple intervention such as moving air more with residential fans within an ambient air velocity range, which remains comfortable for other reasons which professor Richard Didier is here will be able to talk about that in far more detail than I can and with more authority. But within these ranges of air velocity, what we model is that people can maintain the same thermal experience but at higher temperatures, which means that you can set your thermostat of your air conditioning unit to about four degrees Celsius warmer. This means the air conditioning unit will turn on later in the day, it'll turn off earlier in the day. That means it'll be on for a shorter period of time and some days it might not even be used at all. Where as instilled air conditions, it would be. And collaborating with our colleagues of sustainability led by Professor Manfred Lanson and Aaron , we estimated that the reduction in electricity usage and cost for cooling when using this approach is fan first cooling approach saves 70% of electricity use for cooling throughout a typical year here in Australia. So if there's one thing that people can do at the end of this particular talk today, if you go home throughout the summer, if you use air conditioning, consider turning up that set point by about three or four degrees and invest in the fan and you should feel exactly the same but your bills will be far low. And that's really important in the context that we're finding with soaring energy prices as well. But that's a solution that can be used in a variety of different contexts including indoor working environments.


- Great. You know, thanks Ollie. And clearly, as Ollie points out, in the most recent Northern summer where the governments of Italy and Spain were requiring people to increase the set point of the cooling systems in buildings. This understanding of the importance of moving the air as well as cooling it is really a fundamental understanding that we seem to have lost. I remember when I was a child growing up in Brisbane, nobody had air conditioning and we all used fans and so, you know, there's been a rapid change of context in Australia and we seem to have lost this understanding and the heat and health incubator is trying to reclaim the understanding in part of this work. Georgia, tell us a bit about the aging context and the solutions that we're finding, yeah.


- Yeah, absolutely. So it kind of of continues on the theme of, you know, air conditioning is quite protective in extreme heat events for any vulnerable populations but we need to kind of look at ways that we can protect these populations for people who don't have access to air conditioning, who can't afford air conditioning use as well. So one part of my research is, you know, we're trying to understand why older adults and people with cardiovascular disease are at greater risk during extreme heat, but also finding solutions to protect them in the meantime as well. So I've spent quite a lot of years conducting research using the climate chamber here on level nine where we do simulate heat waves and we are looking at different cooling strategies that can be used during both hot and humid heat waves and hot and dry heat waves. So we can look at two different contacts. So one thing that's important to understand about people over the age of 60 is that they do have a reduced capacity to produce sweat. So this means that they're not able to lose as much heat from their body as someone who's maybe between 18 to 40 years old. So one strategy that you can look at is something as simple as putting cold water on your skin that can help you once you evaporate that water can help you to lose heat from the body. But fan use is quite beneficial in the context of extreme heat, especially in very humid heat waves where you are producing a lot of sweat, it's gonna help that sweat to evaporate from your body and help you to lose heat. And then even combining skin wetting with fan use but extending that to just things like going to a swimming pool or having a cold shower, getting a sponge and dabbing yourself with cold water. These are all very simple strategies that are low cost, consume no carbon or very minimal if you use a fan. Very economical for a lot of populations as well. So that's a lot of the research that we're doing. And again, just to follow on what Adrienne was saying before, you know, a lot of research doesn't include pregnant women but a lot of research doesn't include people with cardiovascular disease 'cause people are so concerned just to, you know, think about exposing these people to the heat with fear of what might happen. We know that there's an increased cardiovascular strain, the heart has to work a lot harder when we're exposed to a hot environment but it's understanding how hard does the heart work and how much heat is too much heat before we start to see some negative effects. And that's some of the work that myself with Ollie and the heat and health research incubator are trying to understand as well.


- Great. Well thanks very much Georgia. So now, it's over to you in the room here. An opportunity for a Q&A with the panel and also online. I can see a number of online questions. I can see one hand up in the room. Let's start here and then others in the room or we'll go online next, yeah.


- I went to a lecture with the chief scientist's Bobby towards nature, smart livable cities. Now that was talking about greening cities to keep them cooler using the plant's transpiration to take excess heat off. My other comment really is with the last floods and warmer weather, we're getting tropical diseases right down to Victoria. Do you think we're gonna end up with tropical diseases right throughout the East coast of Australia?


- Hmm, great. Well, thanks very much for those reflections. I might pass perhaps to Ollie in that urban context because I know you are doing work at different scales.


- That's right.


- And also for the second one, around mosquitoes, you just recently won a really interesting grant .


- Sure, yeah, yeah. I can briefly touch on that predominantly the first comment. So thank you for that. So there are a variety of different levels at which we can introduce interventions. And we actually recently described this in a series of papers that we published in the journal called Lancet. And there's a few copies are lying around that we'd be able to distribute to anybody that's interested in. So the way that we described it is that there's something called the heat cascade. So the reason that we ultimately get hot, whether we're outdoors or indoors, is due to the transfer of heat from the environment down to the individual. So if we think about us in this room right now, if it was 45 degrees Celsius and very humid outside, the reason that we would get hot is because of failure to intervene at the landscape level, which is what you are describing at the building level and then at the individual level. Now, I'll start at the landscape level 'cause I think that's what's probably most pertinent to your comment is that one thing that we can do is to reduce something called the urban heat island effect, which is essentially an increase in ambient temperatures in densely urbanized areas owing to the features of the built environment and the landscape environment. Heat retention from things like concrete, heat generation from things like cars, from air conditioning units, et cetera, et cetera. So I was thinking about ways in which we could reduce that generation of heat and retention of heat and one of the main ways in which we could do it at the landscape level is increasing something called green infrastructure, which is more greening, more parks. The central building down there has greenery on its walls and on its roof I believe. And that is owing to that process that you're describing, something called a evapotranspiration which is exactly the same way that humans keep cool is by having moisture on the skin surface, it's evaporation and ex, liberates latent heat with it. So that's why greening works. Very briefly at the built environment level, we can increase insulation of buildings, we can increase the reflectivity of buildings to try to slow down the transfer of environmental heat that's outside to the interior of the built environments. But in some settings, particularly in low income housing, which are predominantly constructed of low thermal performance materials that fails. So we are left at the, what could we do it in the individual level. And that's really what Georgia's work is informing a lot of. The question is, what should we be telling people to do to mitigate the physiological strain that evolves during extreme heats exposure which is ultimately responsible for making people ill, in some cases killing them. The physi, the cardiovascular strain, the thermal strain and the dehydration. So the, and it's important that we look at these interventions, thinking about it in a low resource context because the most vulnerable can't afford a, the latest ice fest, they can't afford the latest gadgets. We've gotta think about things that people can do right now with the resources that they have to them right now. And if that means in many cases that means simply using water potentially. In some cases, they won't even have clean water. So what can you do with clean, unclean water to keep cool without having to drink it? That's something that we're looking at. Very briefly, I'll just touch on the mosquito borne disease question. The deputy director of the thermal ergonomics laboratory, Dr. Yorgi Mavros is just, this is under embargo. So I don't really say too much about it. We keep it inside here, I think it'll be all good. We just received a very nice grant led by Yorgi and Georgia. Sorry, and so James is a chief investigator on that particular grant as well. She's looking at this in the context of trying to reduce the risk of mosquito-borne diseases in settings where people acquire those diseases due to mosquito bites overnight. And the number one way in which we try to prevent that is by having insecticide treated mosquito nets. But the number one barrier to overnight net use compliance is feeling too hot. So the question is what could we do to that? The interior of that mosquito net environment moving air is one of the things that we're looking at to try to improve sleep quality, improve over net use compliance. Once we understand that context, that's what really what we're trying to understand, the parameters of that, and try to scale that up to a field setting which we can actually demonstrate that these interventions cannot just reduce the impacts of direct impacts of heat but also the secondary impacts in the form of mosquito-borne diseases in that context.


- Yeah, I mean I think that's really interesting work. We won't talk about who the founder of that one might be.


- But maybe but you know, potentially, you know, very relevant the control of malaria for example in Sub-Saharan Africa. So thanks for that Ollie. I might go to one of the questions in the, from the pre-registration questions. There's one here I think for Adrienne. You know, as a clinician, what are pregnant women concerned about when they're thinking about hot weather and heat extremes?


- So we get questions around, can I go in a spa, that's a common question and can I continue to exercise when pregnant? So I think for the first one about going in a spa or not, a lot of that, you know, advice and temperature is based on older studies. Some of them are from animal herds like cows and looking at heat as a teratogen in cows, not in pregnant humans. And some of that data also comes from like maternal fever studies, so things like the Spanish flu and getting hot at different parts of pregnancy and whether that leads to miscarriage or not. So I guess the, to answer the question, if you are in hot water, does it actually make you hot? And I guess we do have some data to say it probably doesn't make you as hot as you think. The best way to cool yourself down is to get in water unless it's super, super hot. It's the best way to actually cool yourself down. So some of that might well be a, an urban myth, not that I'm gonna tell everybody to go and get in a spa, but I think some of it is based on flawed evidence and the exercise one I think is very interesting. So if you are a very fit pregnant woman, then the worst thing you could do is stop exercising in pregnancy. So if you have that physiological capacity being pregnant, she didn't really change that. And we know that if you look at cohort studies or just routine data in pregnancy, people exercise far too little in pregnancy. And so some of these criteria that happen I guess are based on not great evidence. So I guess we'd say if you're fit, continue to exercise, don't stop. If you don't exercise at all then you might want to do some exercise in pregnancy but you're not gonna suddenly take up running the 10k if you've never done any exercise before.


- Great, thank you.


- Do you think it's also perhaps it comes down to employing a little bit of common sense in terms of when you choose to exercise, maybe don't exercise in the peak hours of the day.


- Of course, yeah.


- Maybe thinking about how long you're gonna exercise for. Maybe half an hour, 45 minutes will do the job. You don't need to push it on for much longer. Just employing a little bit of common sense also.


- Yeah, I think common sense is very important but often lacking


- Yes, indeed. Yeah. The, here at, I think also online and an important question about differentiating between extreme heat when it's humid and extreme heat when it's dry. Georgia, would you like to say something about that and its importance?


- Yeah, absolutely. So there is a difference between what we call a very hot and humid heat wave and a very hot and dry heat wave. So I feel like more so lately in Sydney, it's been quite humid but typically in Australia, in the East here, we do experience dry heat waves. So that's when there's very low relative humidity. Up North Queensland and in North America, they experience quite hot and humid heat waves. So in hot and dry heat waves from a physiological perspective, a lot of the sweat that is secreted onto the skin surface evaporates. And so our body almost struggles to continue to sweat to allow us to lose heat from the body. So this can cause dehydration problems and you know, increases our core temperature. So we have, you know, increased heart rate and cardiovascular strain. From a human perspective, a lot of the sweat that's on the skin, if you start to notice it dripping off of your body, it's not evaporating so it's not actually contributing to heat loss from the body. So in that situation, we need to try and figure out ways to increase the evaporation of sweat onto the skin surface and that's where using things like fans or increasing airflow onto the body are going to be really beneficial to help keep us cool. So the different heat waves influence our body different ways. Hot, dry, we wanna look at getting as much water on the skin as possible, where hot, humid, we wanna look at trying to get the sweat off the skin as much as possible effectively. So yeah.


- Great, thanks. Thanks very much Georgia. And I think we've got another question from the room at the back.


- Yes, sir. Thank you for the interesting introductions. I've a plea to Ollie and a question to James. Ollie you are.


- [Ollie] It's not stop talking, is it?


- No. Your information on the air conditioning and the moving air and the temperature that you feel when the air is moving that feels four degrees


- [Ollie] Yeah.


- better. Can you please spread that message wherever you have a chance and let us do Westfield especially and to all restaurants and because wherever you enter in somewhere is freezing cold and that costs a lot of extra energy. Then my question to James, as parents, we hurt, we had a common understanding and it might be wrong that kids develop easier fever and higher fever. If that is correct, is there any link to what heat does with their bodies?


- Yes. So although that addresses a question to me, I wonder if Adrienne might be slightly better faced as a, from a clinical perspective to comment on that.


- Yeah. So I think they don't get a higher fever but they have a more rapid increase from a normal temperature to a high temperature. And they also have I guess a greater susceptibility to things associated with fever like febrile convulsions for example. So much, much more common for that to cause a problem when you're in the preschool age group than when you're, you know, over about the age of sort of seven or eight. So, but the, I don't think there's data to say that the actual temperature you get is higher. I think it's more the rise to get there that's higher. Yep.


- Great, thanks. And Ollie, would you like to respond to first question as well?


- just maybe ask James to reflect a little bit on some of the factors that could render young kids more susceptible to overheating, not in a fever context necessary, but in a physical active just from the terms of the body size and things like that.


- Yeah, sure. So I alluded to some of this when I spoke to you earlier and there's this kind of dilemma whether it's a physiological difference that perhaps exists between adults and children or whether it's behavioral. But if we think about some of the physiology that's going on during childhood, as we said, adults and children are very different. A very obvious way in which they differ is their body size and this is both their body surface area and their body mass. And this combination of the interaction between these two factors is relevant from a body heat storage perspective. Now, when we're younger we tend to have a larger body surface area, but a lower body mass. And in terms of from a heat balance perspective, this can be disadvantageous for children, especially when ambient temperature exceeds skin temperature. So once we get past around the 35 degree Celsius mark, what that additional body surface area to mass ratio can essentially accelerate is the amount of heat that's blown on to a child's skin, potentially accelerating the rate at which they heat up.


- With that said, what I'll just quickly say is, so we've got an honor student, Megan , he's writing an excellent paper at the moment. That's really trying to model the ways in which different surface air to mass ratios actually matter. And another key inconsideration is whether there's parallel reductions in the ability to sweat. So if you've got those two things happening at once, higher surface air to mass ratio and a reduction in the ability to sweat, then that's where it becomes really quite problematic.


- But as I also mentioned earlier, the evidence that's emerging from a lab suggests that children can sweat. They do have the ability to sweat.

- Yup.


- And it's very similar to that ability of adults.


- Yeah.


- So we don't think there's a problem from that perspective.


- Great. Well, thanks very much. Now, just doing a bit of a time check. I think we've got six or seven minutes left. I think we've got another question in the room. And is there one more up the back as well? We might have to have some of the questions just casually at the end. But let's go over here first and then up the back and see how we go time wise, yeah.


- Okay, thank you. My question's towards Adrienne. So I was wondering concerning pregnant women what the next step would be in, a next step in within the incubator research you're doing? So is it, are you also, for example, gonna look at if there's some fetal stress associated with increased heat or other pathways like you know, that mothers are more prone to pregnancy complications like gestational diabetes and hypertension and through that, there could be mechanism. Or I'm wondering even through sleep for example, right, that pregnant women during hot nights might not sleep as well and there could be something going on or is it all limited towards the physiology within the mother directly in that ? Yeah.


- Excellent question. Anyone from the welcome trust listener .


- [Ollie] Maybe. Hi, if you are.


- So we have applied for a grant to try and answer some of these questions, which has a field study in two different countries working with colleagues from the University of Sydney, the Institute in New Delhi and the Public Health Foundation of India. And those two field studies would be done in quite different populations. One, a rural low income population with a lot of subsistence farming and one a sort of low to middle income urban setting and a climate chamber study here in Sydney where we would look at maternal heap strain and fetal strain. So we would do that by fetal heart rate and some measure, some doppler studies looking at placental blood flow. And there are a number of new products to look remotely at fetal heart rate that I guess may or may not be ready or not under patent or if we were lucky enough to get funding. But they're actually, there's, I can show you this great paper published last week from The Gambia, 6th of December. Very similar to some of the work we're trying to do but obviously quite a different field setting. And I think there will need to be a lot of these studies to compliment each other because the experiences of pregnant women by occupation and by the temperatures and heat stress are exposed to is really different in all those populations. So hopefully we'll have the ability to answer some of those questions, yeah.


- Great. Thanks very much, Adrienne. I think there was one more question up at the back, yeah.


- Oh yeah, thanks. It's all extremely relevant and important stuff you're telling us. I was curious if, I know you're doing all the international research, if you had looked at populations around like say Saudi Arabia and Dubai who historically have lived with really high temperatures and obviously probably low levels of foliage in the environment, they look like they cover their bodies quite a lot. So I'm not sure how that affects evapotranspiration on the skin.


- [Tony] Mhm.


- If that has informed anything of your understanding about habits, cultural habits, maybe siestas, how we, how active we are at different parts of the day and how they as populations have coped before sort of having this wealth of oil and obviously cranking up the air conditioning if that's had any research done into it as well.


- Sure. Maybe I'll quickly take this. That's a, it's a great point. So I think one thing that we shouldn't get too preoccupied with is just temperature though. So those type of environments that you're describing have very high ambient temperatures and they're measured in the shade as well. That's another take home point for everybody is that the temperatures that we see are measured in the shade, not in the sun. They're typically 15 to 17 degrees Celsius, higher in the sun. But the humidity is very low. So under those particular conditions, the ability to sue to, to evaporate sweat is unimpaired by the climate but the impairments comes from the body as Georgia described. So the ability to secrete sweat. I think the behavioral component is a really important and interesting question and I actually was reflecting on this this past week, thinking about a longer term research project and really trying to acquire as much information from traditional sources where people have existed for thousands of years in certain parts of the world without any mechanical interventions such as air conditioning for example. Clearly this is being possible and documenting this and leveraging this traditional knowledge to inform contemporary policy. I think that's a really important consideration. And another thing that Tony and I have talked about in the past is also the role that certain cultural norms play into this whole situation as well. You know, just looking at people in business suits in Singapore for example and it's 36 degrees Celsius and 75% humidity and they're wearing all this clothing because it's the expert, the cultural expectation is to be wearing this business suit if you work for HSBC or whoever it is. It's trying to think about ways in which we can modify the personal factors, what people are doing and what they're wearing to not rely, to rely less on these carbon intensive cooling strategies such as air conditioning. there's lots of work again and it also demonstrates why we need the input of very different levels of expertise or different types of expertise. This is why we're seeking, not just to work with clinicians and physiologists, but we're seeking to work with social scientists and people who can, even historians who can understand this information better and help us synthesize it to make it useful moving forward.


- Great. Well, thanks very much, Ollie. I think that's a great way to finish the Q&A segment. Let's thank everybody for that. Now just as we close, I might invite the panelists to say one final message, like a takeaway message if you like from tonight's discussion that potentially might be useful here in Sydney and around Australia in the coming summer. So what would the takeaway message be? Where should we start?


- Start at that end so Adrienne can figure one out. I recognize that look.


- I actually thought about this earlier this afternoon 'cause I was thinking about a lot of the topics that we were talking about and I feel like it's a lot of doom and gloom. Like, you know, heat is bad, people are dying, people are going to hospital. And I was kind of thinking about like, you know, you get presented with such a big problem, but you know, we as humans have to adapt. Like I, it's only gonna get warmer and we need to learn to not run from our problem. We need to adapt to this problem and build resilience within our community. So as much as there are negative impacts associated with heat exposure, I think the work that the Heat and Health Research Incubator is doing to try and find solutions is so important. But I think as a community and as a population, as we move forward and we work together and with we adapt, I feel like it's not as doom and gloom as we might present it to be at some point. So that would be my take home message.


- Great. Thanks very much, Ollie?

- Increase your air conditioning set points by four degrees Celsius, remove the air.


- Thanks very much, James?


- I guess just a quick one for me in terms of the work that I'm doing with the children is that we are not trying to put children off being physically active in the heat. We're just trying to build a good, strong evidence base with which we can protect them, keep them cool, keep them safe so they can continue what they're doing into the future.


- Great and Adrienne.


- I think the last thing is collaboration. I think these are really big problems and they require lots of different people, lots of different organizations to help solve them and I think that's what the Heat and Health Incubator is trying to do.


- Yeah, great. Thanks, Adrienne. The, I do note that there were quite a lot of great questions online and maybe we encouraged the organizers to send them through to the incubator 'cause I'm sure we could have some more dialogue


- We're also happy to stick around for a little, well, unless Adrienne . known for like 28 hours . But yeah, happy to fill in any questions.


- Yeah, so for people in the room, hang around. And for those online questions that we didn't get to, I'm sure the incubator will be happy to respond to them.


- Absolutely.


- Via email as well. So let's thank our panelists once again.

Listen to the podcast

Further links and resources 

  • Hot weather and heat extremes: health risks (The Lancet Series, 2021)    
  • Reducing the health effects of hot weather and heat extremes: from personal cooling strategies to green cities (The Lancet Series, 2021)
  • The potential for indoor fans to change air conditioning use while maintaining human thermal comfort during hot weather: an analysis of energy demand and associated greenhouse gas emissions (The Lancet Planetary Health, 2022)

About the speakers

Professor Ollie Jay

Professor Ollie Jay is Professor of Heat and Health and Director of the Heat and Health Research Incubator in the Faculty of Medicine and Health at The University of Sydney. His research activities primarily focus on developing a better understanding of the physiological and physical factors that determine human heat strain and the associated risk of heat-related health problems during work and/or physical activity, as well as among the general population during heat waves. 

Adrienne Gordon profile photo

Professor Adrienne Gordon is a Clinical Professor in the Discipline of Obstetrics, Gynaecology and Neonatology at the University of Sydney and senior staff specialist Neonatologist in the RPA centre for newborn care. She trained in paediatrics prior to specialising in neonatal/perinatal medicine and is passionate about the public health impact of a healthy start to life and preventing adverse pregnancy outcomes, especially stillbirth. She is a Chief Investigator on the NHMRC Stillbirth Centre of Research Excellence and a Board Member of the International Stillbirth Alliance. 

James Smallcombe

Dr James Smallcombe is involved in several research projects at the University of Sydney aimed at increasing human resilience to extreme heat events, including a large research project funded by the Wellcome Trust which aims to identify low-cost and sustainable cooling strategies for use in Bangladeshi ready-made garment factories. James previously worked at  Loughborough University on an EU Horizon 2020 funded research project (HEAT-SHIELD) which adopted a multi-sector approach to help protect the European community against the environmental challenges associated with climate change.

Dr Georgia Chaseling

Dr Georgia Chaseling is involved in researching the impacts of environmental extremes on adverse cardiovascular outcomes amongst vulnerable populations. She is currently part of the SOLVE-CHD research team, funded by a 5-year NHMRC synergy grant, aimed at solving the long-standing evidence gaps associated with cardiac rehabilitation and secondary prevention of coronary artery disease.


Professor Tony Capon directs the Monash Sustainable Development Institute and holds a chair in planetary health in the School of Public Health and Preventive Medicine at Monash University. A public health physician and authority in environmental health and health promotion, his research focuses on urbanisation, sustainable development and human health. Tony is a former director of the International Institute for Global Health at United Nations University (UNU-IIGH), and has previously held professorial appointments at the University of Sydney and Australian National University.