The Latest Science on Extreme Heat: How Hot Is Too Hot?

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1:39Bloomberg Audio Studios. Podcasts. Radio. News. Zahra Hirji covers climate at Bloomberg, and she recently had the opportunity to take a trip to one of the hottest places in the world. I took an elevator and upstairs. In a university building, the elevator comes out in a corner. And if you turn left. In Canada, there's this long, tall hallway. And all along that hallway is one of the world's largest research facilities dedicated to studying the effects of heat on the human body. And we kind of just spent the day walking through, opening door number one, door number two, door number three. Behind each one, there were people doing all kinds of tests.

2:26How's that? It's okay? People like Janet Spencer. She's 75 years old. She describes herself as a veteran of the lab. She's retired. Specifically, she's a retired mediator for Canada's Human Rights Commission. I never imagined that I'd be a guinea pig for science. What temperature are we at? We're at 36 degrees and 45 % humidity. So pretty warm for sure. Janet was doing what's called a passive trial, where she was just sort of hanging out in the heat. These can be full days. In March, she was there for three days straight, which meant she was sleeping in the room. And she described it as watching a ton of Netflix.

3:16When Zara met Janet, she'd only been in the lab for an hour. But she was already feeling the effects. When I started, I brought my paper to read, and I managed to read that in the first half hour. But right now, pretty much all I'm capable of is playing mindless, solitaire games. Down the hall, Bob Stryker was doing a very different kind of experiment. And how do you feel right now, since I just saw you walking on the treadmill for a while in the heat? I'm tired. I'm tired. And in another room, Lutz Suckstorf was recovering from a cycling test. Mentally, it really starts to drain you. It becomes an effort, literally that one foot in front of the other.

3:58If we had another half an hour, 45 minutes, my body would have started to say, no, this is no fun anymore. When Janet, Bob, and Lutz spoke with Zahra, they kept the mood light. But their motivations for participating in this research and the goals of the research itself are very serious. Nearly half a million people die every year as a result of extreme heat. according to research compiled by the reinsurance company Swiss Re. That's more than the total from hurricanes, earthquakes, and floods combined. And Zara says the real number is likely even higher. Often we're just maybe tracking the most extreme cases that are coming through hospitals.

4:40But, you know, if you're dying from a heart problem that was tied to the heat, that might not necessarily be recorded as a heat death. So, you know, it is a really big number that we don't even have a full grasp on. I'm Sarah Holder, and this is The Big Take from Bloomberg News. Today on the show, the researchers on the forefront of the latest science on deadly heat. Why everyone's at more risk than they think, and what actually works to mitigate those risks.

5:17The heat lab at the University of Ottawa, the Human and Environmental Physiology Research Unit, has been around since 2000. And over the last two decades, the lab has been at the forefront of studying humans' ability to live and work in the heat. A lot of the work that I am doing is really focused on understanding the impacts of heat exposure on the health and well-being of the general public and workers. The man in charge is Dr. Glenn Kenney. He's been studying the effects of heat on the human body for 35 years. And he says in many ways, this is an old problem. When we think about, for example, workers and we think about the impacts that heat has, this is not new.

5:57This is something we've known for decades. But as the climate changes, heat is only growing more extreme. It was only a couple of years ago in 2021 that the Western heat dome, which was this really deadly heat wave, hit the Western part of Canada, also the Western part of the U.S. But in Western Canada, like over 600 people died. A lot of them were elderly and a lot of them that were people living in their home who didn't have air conditioning. And they were basically cooking in their homes and people didn't have a way to kind of check in on them. And unfortunately, a lot of them didn't realize they were too uncomfortably hot until it was too late because of their impaired ability to sense it.

6:42Kenny says to keep people safe, you need to understand how heat affects different kinds of bodies. He says that older heat guidelines have typically been based on research focused on young, healthy people who've had limited heat exposures. Think a couple of hours at a time. That's where his test subjects come in. Kenny and his team use specialized equipment to measure how extreme heat can affect body temperature in simulated real-world conditions. We have an apartment-styled chamber where we have a bed, where we have a kitchen, a washroom, where we can bring in the patient and have them live within that chamber so that we can understand what happens to them and monitor them not only during the daytime, but also what is the impact of that heat exposure on sleep?

7:33Kenny also has another secret weapon, a one-of-a-kind air calorimeter, which his lab uses to measure the amount of heat released from or absorbed in the body. So we did that before and after the three-day exposure, so we can see if there's a decrease in my capacity to dissipate heat. So is that exposure also causing deterioration in my ability to thermoregulate? But that's not the only data the lab is collecting. The team keeps close tabs on participants' cognitive and physical performance and records detailed updates on their temperatures. These are actually pretty uncomfortable trials. I mean, the more I was learning about it and talking with people, I'm like, I'm not sure I would want to do this.

8:19They do a lot of tracking of your temperature. And we may think, oh, you can take their skin temperatures, right, when you go to the hospital or the doctor and they check to see if you have a fever. But that's really not the best way to get a gauge of how hot your insides are. That's called a skin temperature. But it's better to get a core temperature. And there are a couple of different ways they can do that, including putting something down your esophagus, which is like really intrusive. But also the more common is like a rectal probe. And that was tracking their core temperature that she was sort of wearing on a fanny pack.

8:56Armed with the data from these experiments, Kenny's lab has been assessing whether the upper limit for a safe indoor temperature recommended by some Canadian officials, 26 degrees Celsius or just under 79 degrees Fahrenheit, is actually safe. And they found that for a day, it seems to be. What they're trying to figure out now is how the body responds to those temperatures over longer periods of time. When you are exposed to temperatures above 26 degrees Celsius, older adults and individuals with chronic diseases are going to start seeing increases in their level of physiological strain. But I want you to imagine that increase in temperature is a strain.

9:38Go out and exercise and keep that stress. Now, that's a stress. And that stress is essentially maintained over time. That person is going to overheat. If that heat wave stays and overheating is consistent, that strain will remain. So in a warming world, how can people reduce the strains that come with extreme heat? And are all cooling options created equal? That's after the break.

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13:18Here in New York, where I am, when a heat wave hits, the city opens up public cooling centers. But Dr. Glenn Kenney, who runs one of the world's largest heat labs at the University of Ottawa, says cooling centers alone don't totally protect against the risks of extreme heat. The problem is upon re-entering to the heat, you haven't removed all that heat from the body. Air is not a good conductor of heat, unlike water, right? So one of the things upon re-entry of the heat, the body actually warmed up very quickly. So the challenge is, is that that person feels very well. They feel more relaxed. They feel cooler.

13:53Problem is within a couple hours, their body heats up very fast and get as hot as their non-cool counterpart. So imagine they're going to, they may not adjust their behavior because essentially they feel better. So the problem is, is feeling better actually masks the risk that they face because their temperatures are equally as high. Bloomberg's Zahra Hirji says another researcher, this one at the University of Sydney, who did his postdoc at Kenny's lab, looked at the efficacy of fans and how they could be used in Bangladeshi garment factories, where workers face especially hot and humid conditions.

14:28Every part of the world, heat is a combination of high temperatures and humidity. So in a place like Bangladesh, you can have much higher humidity than you might in some other places. And so that's a key thing to understand. And the type of solutions that you then have to keep people cool can be different. So, you know, when we're looking, for example, at electric fans, like how effective are they as compared to air conditioning? Air conditioning is always going to be the best, but not everybody has access to that, right? Especially across the developing world. So a key part of cooling is not just sweating, but then that sweat be able to cool or to dry off.

15:11It's that drying piece that is essential. If you're just sweating and sweating and sweating, you are going to keep overheating. And so you need it to continually be drying to be effective. And so that's one thing where a fan in a particularly humid environment might be helpful because it can help kind of encourage sweating to have that maximum potential. But it's worth noting fans also come with risks. In extremely hot and dry climates, fans can actually heat people up faster. And like cooling centers, Kenny says fans can give people a false sense of security. They can make you feel better while you're using them.

15:51So good that you may feel well enough to go back out in the heat. But what's important here is it doesn't reduce the strain on the body. It makes you feel better. That, again, masks the potential dangers that you might experience because you're not able to sense the fact that you are probably going to be overheated or you are overheated, you're under strain. The United Nations has used Kenny's research to inform its worker safety recommendations. And Zara says it's not just governments that are taking notice. Companies like SmartCone are too. They make devices and wearables to monitor the temperature on job sites.

16:29One of the clients they're currently working with is United, the airline company, which has told me how they are testing out smart cones wearable device, which helps monitor heat exposure and worker exertion at employees working on the tarmac and on the ground at Phoenix Airport. So this is still early days. Egg frying on the tarmac conditions, probably. Right. But real world example of how this is playing out. Zara says that when she asks heat researchers about the next big questions in their field, their answers usually fall into two camps. The first was what are the most practical takeaways we can get in the applications of this work to really help best improve people's safety today?

17:20And then it's what's going to happen in the future? How do we understand how hot is it actually going to get? And then what does that mean for people's health? Part of the interesting research that's going on is trying to understand that. And it really is a whole bunch of unknowns and really like we don't know what is the limit. I feel like that's a lot of what this work is trying to figure out.

17:49This is The Big Take from Bloomberg News. I'm Sarah Holder. The show is hosted by me, David Gura, Juan Ha, and Saleh Mosen. The show is made by Aaron Edwards, David Fox, Eleanor Harrison Dengate, Patty Hirsch, Rachel Lewis-Kriske, Naomi Eun, Julia Press, Tracy Samuelson, Naomi Shaven, Alex Sugiura, Julia Weaver, Yang Yang, and Taka Yasuzawa. To get more from The Big Take and unlimited access to all of Bloomberg.com, subscribe today at Bloomberg.com slash podcast offer. Thanks for listening. We'll be back on Monday.

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