The surprising science behind staying cool in a heat wave

This post first appeared on Canadian Geographic’s Compass blog

Emergency cooling centres are opening across Ontario and Quebec as parts of the provinces wilt under this week’s extreme heat.

Among the usual tips for staying cool are drinking cold water, using wet towels to shed heat and staying in the shade. But according to University of Ottawa professor Ollie Jay, whose research explores the body’s heat-loss mechanisms, not all advice is created equal — and drinking cold water might not be the best way to cool down.

“Obviously staying hydrated is important,” Jay says, “but it’s not going to necessarily save you.”

Jay explains that the body has a separate set of heat sensors in the stomach that, when cooled by cold water, actually signal to the body that it is cooler than it really is, inhibiting sweat production. Normally the body loses heat to the cooler outside environment by radiation, but at temperatures above 35 C, the only way the body can cool itself is by sweating — so throttling back this vital system on a hot day can be dangerous. The heat that is lost to the cool water is not enough to cause a net drop in body temperature, and the feeling of having cooled down might cause people to take fewer, more important precautions, such as seeking shade or limiting activity.

Sweating sheds heat by the endothermic (heat-requiring) process of evaporation. Water absorbs heat to turn into vapour, so when a person sweats, that heat comes from his or her skin, lowering the body temperature. If a person isn’t sweating, there is no way for heat to exit the body when it’s hot outside.

“We need to dissipate heat at the same rate that we’re producing it, otherwise we’re in what’s called a ‘heat imbalance,’” says Jay. “Our core temperature (normally about 37 C) starts going up and up and up. If we start reaching 39 C, 40 C, we start experiencing things like heat exhaustion, or eventually heatstroke if that core temperature reaches 41 C or 42 C.”

Heat exhaustion can cause nausea or dizziness and is a sign that the body is getting dangerously hot. Heatstroke can result in unconsciousness or even death. For elderly people, the most serious danger from heatstroke is that the heart goes into overdrive trying to shed heat by pumping blood to the skin’s surface, and this can expose frailties within the heart. For younger people, death by heatstroke could actually mean death by septic shock as the intestines become permeable like a sieve, leaking toxins into the body.

On a sunny day, temperatures in the sun can be 8 C to 10 C warmer than the reported temperature taken in the shade, and there will likely be plenty of places across Ontario and Quebec that will see temperatures well above the body’s natural core temperature of about 37 C. So find some shade, wear breathable clothing and stay hydrated — but maybe skip the ice-cold glass of water.

Editorial #6 – Cry me a bottle

What came first, the breakdown of every water fountain in the school, or the introduction of vending machines and Sodexo selling us water at $1.75 a bottle? After four years of never seeing a single fountain on campus in usable, working order, I’m inclined to wonder whether the chicken and the egg are conspiring to screw me out of my bar change.

Bottled water is a ridiculous industry. Regular bottled water ranges from about 50 cents a bottle to three or four dollars to drink what the kids on the OC drank. That’s not even taking into account the “designer” water now available – and here I was thinking that the last major innovation in water was, well, water.

Does your car run on water? You’d better hope not – at two bucks per litre, Nestle will be the next ExxonMobil before long. For the discerning vehicle, there will be premium mineral water, fresh from a spring in Tahiti where the hardworking indigenous people’s rich, ethnic culture is kept at a safe distance, so as not to disturb the unique balance of hydrogen and oxygen.

Speaking of oil, though, the relationship is even closer than some sad, hypothetical scenario: to produce, package and deliver 591 mL of the same thing that comes out of your hose, it takes over a quarter of that bottle in oil.

Why do people drink bottled water? For some, it just tastes better. But in a blind taste test conducted last year in the Bloomfield Centre, students (including myself) picked tap water just as often as bottled water. Other people will say it’s safer – but when was the last time someone got dysentery from drinking Antigonish water? For anyone that concerned with safety, his or her bottle should come with a lifejacket.

Thankfully, the recent recession in combination with the movement towards greener lifestyles does not bode well for the bottled water industry. Canadians not only can afford to buy less dihydrogen oxide, but can also feel more of the environmental pressure they exert with the unnecessary emissions from the plastic and transportation associated with it. Only a decade ago people were marveling at the marketing achievement that is bottled water; now, many of us marvel at the fact that it exists at all.

At least one campus in Canada – University of Winnipeg – has put a ban on the sale of bottled water. Students there are now faced with three options: bring a reusable bottle from home, drink from the fountain, or find their own way to get that sweet, sweet Aquafina. Dalhousie last year considered a similar ban, and just recently it was banned from Halifax City Hall.

At the moment, it may not be possible to implement such a ban at StFX – after all, there is hardly a working water fountain to be found outside the Millenium Centre. But why isn’t there? We need to put pressure on those who maintain our campus to keep tap water readily available, at least for those who don’t want to pay PepsiCo for something that falls from the sky and runs from the tap for free.

It’s not just about the economics, and the absurdity of the idea as a whole – although we are probably going to look stupid in retrospect for having thought that having competing brands of water was a good idea. What’s more important is that if we don’t take care to keep tap water available, this erosion of faith in our water supply might one day lead to an actual decrease in the quality of our water supply, as consumer emphasis is placed on a packaged, stamped and sold form of a Canadian resource increasingly envied the world over