Star reporter steps into lab to learn what 38.5 C with 60% humidity — the lethal conditions in Montreal last summer — does to the human body
MONTREAL— Diane Brouillet was proudly independent. She had lived on her own for 40 years.
Last summer, as the temperature and humidity skyrocketed during one of the worst heat waves in a century, the 73-yearold grandmother refused to leave home. She might not have had air conditioning, but she didn’t like the dry air and didn’t think she needed it.
“She goes: ‘People buy tickets and they spend money to go to Cuba. But I feel like I’m in Cuba in my apartment!’” her daughter Carina Houle told the Star.
“And I said: that’s not funny. But she says: ‘I’m good, I have this fan.’”
Diane lived in a second floor walk-up in LaSalle, a post-war neighbourhood at the southern end of Montreal. She sometimes complained about her knee, which bothered her on the climb up the stairs, but was otherwise healthy.
As June turned into July last year, temperatures in eastern Ontario and western Quebec rose to between 33 and 35 degrees each day.
The humidity, which hit 94 per cent that week, made that heat feel far more suffocating. On the humidex, Montreal peaked at 44 — just below the threshold for conditions Environment Canada calls “dangerous” to human health.
In LaSalle, where you can walk blocks before finding the shade of a tree, the heat was even more stifling.
“There’s barely any grass,” said Carina. “And up on the second floor, there’s no air. It’s very hot.”
On July 5, when Diane didn’t answer the phone, Carina thought she was napping, or out for a coffee. But when she discovered her door was locked from the inside, she knew her mother was home. She called the police. The officers wouldn’t let her go in.
“When I last spoke to her, she was giggling and laughing. She was outside with the neighbours the night before and they were chatting and having fun.
“If I had known it was going to be our last conversation, I never would have hung up,” Carina said. “I wasn’t ready to lose a parent.”
Carina had heard the publichealth announcements warning Montrealers to go somewhere with air conditioning for a few hours every day and to drink lots of water. She’d offered up her air-conditioned home several times. Her kids took their grandmother out to the movies for a few hours respite from the heat. But when Diane said she wanted to stay at home, Carina hadn’t insisted.
“I was aware of the danger, but not, you know, not enough,” she said. “If I would have been instructed and warned differently, then I would have not given her an option. She would have spent the whole summer with us and that’s it.”
The what-ifs are inevitable. But even if Carina had brought her mother home that week, Diane might not have survived the next hot spell.
“Every time I hear that the humidex is going to hit 40 degrees, I say: ‘Maybe today would have been the day she died.’ ”
Last summer, the month of July was the hottest Montreal had experienced in 97 years.
During the heat wave, hospitalizations almost doubled and deaths outside hospitals more than tripled. Public health officials recorded almost 6,000 ambulance calls and 66 heatrelated deaths.
Fewer than 200 kilometres away, in Ottawa, the weather was almost identical. The heat and humidity were just as brutal and lasted just as long. But according to the provincial coroner, no one died.
How could it be that so many died in Quebec, while there was not one heat-related death in Ontario?
It’s a question that risks exacerbating the divide between Canada’s two solitudes, but also one that will become vital for people from coast to coast to coast in the years to come.
Environment Canada’s comprehensive climate change report, published this spring, predicts that climate change will cause heat waves in Canada to “become more frequent and more intense” in the near future.
Depending on how quickly we reduce greenhouse gas emissions, extreme heat that now occurs once every 20 years could happen once every five, or even every other year, by 2050, the report says.
Couple that with the fact that heat is worse in cities, where more than 83 per cent of Canadians live, and contrary to our snowy reputation, we’re going to have a heat problem.
Cities can be as much as 12 degrees hotter than surrounding areas because of what’s known as the urban heat island effect: asphalt and concrete, which heats up, covers much of the ground instead of soil and vegetation, which would otherwise provide shade and cool the immediate area.
Concrete also exacerbates heat waves because it radiates heat even after the sun goes down, keeping temperatures up overnight and prolonging hot stretches.
Another compounding factor is age. Because older people are more susceptible to heat, and Canada’s population is rapidly aging, summers are getting much more difficult for seniors.
And because heat builds up in sick and elderly people over time, the longer the heat wave, the more deadly it becomes.
Heat may be the most visceral effect of climate change. Unlike projected sea-level rise or distant melting polar ice caps, urban heat waves are already killing Canadians. I arrived in Montreal in April, under grey skies and with snow lingering on the streets, so it was difficult to picture the city under a beating sun.
But at the Montreal Heart Institute’s integrative human physiology laboratory, there’s a climate-controlled chamber that acts like a time machine. Professor Daniel Gagnon can recreate the precise conditions of any heat wave — the hot and dry Australian heat wave last January that had highs of 46 degrees or1995’s hot and humid heat wave in Chicago, when temperatures reached 39 degrees, but with the humidity, it actually felt like 56 degrees.
Gagnon graciously offered up his lab and invited me to feel exactly what Montrealers felt last summer. The chamber was set at 38.5 degrees with 60 per cent humidity (55 on the humidex) to mimic a stifling apartment during the peak of the heat.
After weighing me, lab workers attached five heart-monitoring sensors, a sweat rate monitor and four thermometers to my body.
I was led into the climate-controlled chamber. I was expecting a sauna (80 degrees, 20 per cent humidity,126 on the humidex) but people only stay in those for five or six minutes at a time. This was more of a slow bake.
Inside the oven, everything was tightly controlled. No getting up. No talking when readings are being taken. I watched my heart rate and skin temperature rise.
I was only permitted 69 millilitres of water every 20 minutes.
The sweat started beading on my forehead and hands and soon it was dripping down my chest.
Gagnon explained the body has two ways to cool itself. The primary method is by producing sweat, which evaporates off the skin and creates a cooling effect.
The secondary method is by increasing the skin’s temperature by dilating the blood vessels to push more blood to the surface of the body. When the skin temperature (which can rise from 32 degrees to 39 degrees or higher) is hotter than the surrounding air, the body sheds heat through dry conduction.
No matter how hot the air is, if your skin is hotter, heat will transfer from your hot skin to the surrounding air. When your skin is hot to the touch, it’s actually your body trying to cool itself.
But age decreases these abilities. Starting at age 40, but especially after 65, people can’t sweat as much, nor can their capillaries dilate as well.
Humidity, beyond making the heat feel worse, actually thwarts your body’s ability to cool itself.
“For the sweat to evaporate, there needs to be room in the air to accept the sweat,” Gagnon said. “The more humid it is, the less room there is for the sweat to move from the skin into the air.
“Even though somebody can produce a lot of sweat, it won’t evaporate,” he said. “It’s a much more stressful environment … that way of losing heat is just completely blocked. It just drips and it doesn’t provide any cooling power.”
Since the sweat has nowhere to go, it stays on the skin’s surface and you end up sweating less as a result.
As we wrapped up, removing the wires and sensors, I felt light-headed. I had to be helped up as I walked, on unsteady legs, out to the scale to weigh myself.
After compensating for the water I drank while inside, we were able to determine that I sweat out a whole pound during my 90 minutes in the chamber. It became clear just how easy it is — even for a (relatively) young and healthy person like myself, and even in the humid heat where you sweat less — to become dangerously dehydrated.
Sixty-six people died from the heat in Montreal in the first week of July 2018. Eighty-nine across Quebec.
Yet zero in Ottawa. Zero in Ontario.
The Ottawa River, which divides the two provinces, didn’t separate two major weather systems last summer. Heat and humidity ignore political borders. Some speculated that a lack of air conditioning caused more people to die in Quebec.
Statistics Canada data seem to bear this out. Only 53 per cent of households in Quebec have central air or use a window unit, while 83 per cent of Ontarians have some form of A/C at home. In Montreal, 65 per cent of households have A/C, while in Ottawa it’s 82 per cent and 87 per cent in Toronto.
But could this really account for the stark difference in deaths between the two provinces?
Dr. David Kaiser, a preventive medicine specialist with Montreal public health, doesn’t think so.
“It’s because of the way things are counted,” he said.
Rather than being an issue of more people dying in Quebec, the death discrepancy reflects the fact that Montreal healthcare workers count better. They’re finding the kinds of heat-related deaths that are surely occurring in Ontario as well but remain hidden because no one is looking for them.
This is because people who die during heat waves are not dying from heat stroke, a diagnosis that is coded into medical records, Kaiser said. If you only count deaths by heat stroke, you’re missing the vast majority.
“If somebody comes to the emergency room who is 75 years old, has underlying heart disease and he’s dehydrated and … has a heart attack due to his low blood pressure, he will be coded as a heart attack. And we won’t be able to get any further information out of medical records,” Kaiser explained.
“If the coroner doesn’t have information that he had an elevated body temperature, signs of heat-related illness, heatstroke and shock, they won’t count it as a heat-related death.”
People who die in heat waves are often already very frail, and this can obscure for health-care workers the role that heat might have played to hasten their demise.
“In a typical Canadian city, most of the health impacts of extreme heat, and even of just hot days during the summer, are felt by people who have underlying medical conditions: Continued on next page