What extreme heat waves can do to your body

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Humans, with millions of sweat glands, are by far the most prodigious sweaters on Earth.

We sweat to cool. But our bodies have a limit on how much heat we can take before the heat sickens us, or worse. This is especially the case for people who live in cooler areas, like Portland, Oregon, who aren't acclimated to heat extremes. Yet in a world continuously warmed by fossil fuels, heat extremes are more frequent, resulting in more of us exposed to dangerous temperatures.

The recent historically unprecedented heat wave in the Pacific Northwest and Canada killed hundreds of people. Multnomah County, in Oregon, called the spike in deaths between June 25 and June 30 a "mass casualty event." Four times the usual number of people died during this period, likely from overheating (hyperthermia). In British Columbia, the record-obliterating heat contributed to hundreds of sudden deaths, according to CBC, Canada's national public broadcaster. Many of these victims, tragically, were older adults, some of society's most vulnerable people.

What follows is guidance from experts on how extreme heat makes us sick, the warning signs, and crucially, how to prevent heat sickness. It's ever-salient information, because Earth's climate will continue warming for *at least* the next few decades. This means more extreme weather and heat.

"These are very extreme weather events," said Mike Tipton, a professor of human and applied physiology at the University of Portsmouth and an expert in thermoregulation, referencing severe weather made worse by climate change. "We're not seeing a small increase in flooding or heat," noted Tipton. "These are enormous changes."

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Who can get heat illness?

Heat illnesses, ranging from mild episodes to medical emergencies, happen when the body can't cool itself down.

Though older adults are especially vulnerable, anyone exposed to extreme heat can get sick. In Multnomah County, where Portland is located, a 44-year-old (relatively young) likely died of heat illness during the recent heat wave. Common activities like farm work and hot, indoor warehouse jobs can result in excessive heat. No one is immune, stressed Tipton.

There are other factors that can make heat illness more likely in an individual, too, including sunburn, certain medications, obesity, how acclimated one is to hot weather, and more.

Crucially, heat illnesses are not just a matter of people getting hot. Heat, which causes sweating, also dehydrates us. This leaves people, particularly older folks, seriously vulnerable. The loss of water in the body decreases blood volume, resulting in too little blood, ultimately impairing blood flow to the brain, gut, heart, kidneys, and beyond, explained Tipton. What's more, thicker blood increases the likelihood of blood clotting, and the elderly are more susceptible to blood clots.

Warning signs of heat illness

There's a whole spectrum of symptoms associated with heat illness.

The early signs are muscle cramps, along with symptoms like weakness, nausea, thirst, and heavy sweating, among other symptoms, explained Dr. Elizabeth Werley, an emergency medicine physician at Penn State Health Milton S. Hershey Medical Center.

These symptoms (generally called "heat exhaustion") mean someone is on the path of worsening, dangerous heat illness.

"It's time to intervene," emphasized Tipton (prevention and intervention is discussed below). Your body is now gaining heat faster than it can lose it, so the body's temperature continues to rise. "The heat can catch up with you quickly," said Tipton.

During heat exhaustion, people can also develop cold, clammy skin and a fast, weak pulse. But things can get much worse if the body continues heating up.

The different types of heat illness. Credit: cdc

The most dangerous stage of heat illness is "heat stroke," when body temperatures reach some 103 degrees Fahrenheit, or higher. Dr. Werley has seen temperatures of some 108 degrees Fahrenheit in the emergency room.

People become confused, stop sweating, and can lose consciousness. "Those are people that need immediate attention," said Dr. Werley. "Call 911."

Preventing heat illness during extreme heat

Fortunately, there are proven and simple ways to cool our overheating bodies before someone even develops heat exhaustion.

"There are some really simple interventions that make a large difference," said Tipton."Your behavior is by far your most powerful intervention."

The idea is to minimize your own heat production, minimize the heat you're gaining from the environment, and maximize the heat you lose:

• Stay hydrated: "You should be taking fluid as you would medicine in these conditions," said Tipton.

• Stay out of the sun. If you're outside, stay in the shade.

• Avoid activity — that will churn heat in your body.

• Use a fan to blow air over the body. Air currents evaporate sweat from the skin, removing more heat. Don't just fan your head. "It's best to fan the whole body," said Tipton. You can mist the body, too, to amplify heat loss with "artificial sweat." But if you're in an excessively hot room or area over 95 degrees Fahrenheit (try to avoid these places!), fans aren't recommended because they can potentially heat your body.

• Immerse hands in cool water. "Your hands are great at losing heat," noted Tipton.

• Wear light or as little clothing as possible, so sweat can evaporate from the skin.

Of course, some people work outside, at least for part of the time, during heat waves. If someone starts experiencing mild symptoms, like lightheadedness or cramps, move them (or yourself) to the shade and start drinking fluids, said Dr. Werley.

If conditions worsen and emergency responders haven't yet arrived, "you don't need medications or IV fluids to help people out," Dr. Werley emphasized. Apply ice packs or cold compresses to the armpits, groin, and neck to start cooling down victims of heat illness.

(And, as the CDC notes in the infographic above, don't give a heat stroke victim something to drink. In an altered mental state, many heat stroke victims "cannot safely be given fluids to drink.")

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Protect the vulnerable

Older adults and the elderly, tragically, are often the greatest victims of extreme heat. In our modern, progressive, industrialized societies, this is unacceptable.

We can limit these deaths.

"Keep your elderly relatives cool and hydrated," said Tipton.

"Be socially aware," stressed Dr. Werley. "Check on neighbors, check on family members for those populations at risk."

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