How extreme heat kills, sickens, overwhelms and ages us

How extreme heat kills, sickens, overwhelms and ages us

When W. Larry Kenney, a professor of physiology at Pennsylvania State University, began studying how extreme heat harms humans, his research focused on workers inside the Three Mile Island nuclear power plant, where temperatures reached 165 degrees Fahrenheit. .

In the decades that followed, Kenney analyzed how heat stress affects a range of people in intense environments: soccer players, soldiers in protective suits, long-distance runners in the Sahara.

Lately, however, his research has focused on a more mundane subject: ordinary people. Doing everyday things. As climate change roasts the planet.

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Heat alerts and excessive heat warnings were in effect Monday across much of the eastern interior of the United States, following a record-breaking weekend of heat in the southwestern United States. The heat will shift further northeast in the coming days, according to the National Weather Service, to the upper Mississippi Valley, western Great Lakes and Ohio Valley.

With severe heat waves now affecting parts of the globe with frightening regularity, scientists are investigating the ways in which life in a warmer world will sicken and kill us. The aim is to better understand how many more people will be afflicted by heat-related illnesses and how frequent and severe their suffering will be. And to understand how to better protect the most vulnerable.

One thing is certain, scientists say: the heat waves of the last two decades are not good predictors of the risks we will face in the coming decades. The link between greenhouse gas emissions and stifling temperatures is already so clear that some researchers say there may soon be no point in trying to determine whether today’s most extreme heat waves could have happened two centuries ago, before humans began to warm the planet. None of them could have.

And if global warming is not slowed down, the hottest heat wave many people have ever experienced will simply be their new summer norm, said Matthew Huber, a climate scientist at Purdue University. “It won’t be something you can escape.”

What is more difficult for scientists to define, Huber said, is how these climate changes will affect human health and well-being on a large scale, particularly in the developing world, where large numbers of people are already suffering, but good data. are scarce. Heat stress is the product of so many factors – humidity, sun, wind, hydration, clothing, fitness – and causes so much damage that accurately projecting future effects is tricky.

There haven’t been enough studies either, Huber said, of living full-time in a warmer world, rather than just experiencing the occasional summer of roasting. “We don’t know what the long-term consequences are of waking up every day, working for three hours in near-deadly heat, sweating like crazy and then coming home,” he said.

The growing urgency of these questions is attracting researchers, like Kenney, who don’t always consider themselves climate scientists. For a recent study, he and his colleagues placed young, healthy men and women in specially designed chambers, where they pedaled an exercise bike at low intensity. Then the researchers adjusted the heat and humidity.

They found that their subjects began to overheat dangerously at much lower “wet bulb” temperatures – a measure that explains both the heat and the stifling – than they had expected based on previous theoretical estimates from climate scientists.

Effectively, under steam bath conditions, our bodies absorb heat from the environment faster than we can sweat to cool off. And “unfortunately for humans, we don’t sweat much to keep up,” Kenney said.

Heat is climate change at its most devastatingly intimate, devastating not just landscapes, ecosystems and infrastructure, but the depths of individual human bodies.

Heat victims often die alone, in their own homes. In addition to heat stroke, it can cause cardiovascular collapse and kidney failure. It damages our organs and cells, even our DNA. Its damage is multiplied in the very old and the very young, and in people with high blood pressure, asthma, multiple sclerosis and other conditions.

When mercury is high, we are not as effective at work. Our thinking and motor functions are impaired. Excessive heat is also associated with higher crime, anxiety, depression and suicide.

The toll on the body can be surprisingly personal. George Havenith, director of the Center for Research in Environmental Ergonomics at Loughborough University in England, recalled an experiment years ago with a large group of subjects. They wore the same clothes and performed the same work for an hour, in 95 degree heat and 80% humidity. But in the end, their body temperature ranged from 100 degrees to 102.6 degrees Fahrenheit.

“A lot of the work we’re doing is trying to understand why one person ends up on one end of the spectrum and the other person ends up on the other,” he said.

For years, Vidhya Venugopal, a professor of environmental health at Sri Ramachandra University in Chennai, India, has been studying what heat does to workers in India’s steel mills, automobile factories and brick kilns. Many of them suffer from kidney stones caused by severe dehydration.

A date a decade ago stayed with her. She met a metal worker who had been working 8 to 12 hours a day near a furnace for 20 years. When she asked how old he was, he said 38 to 40.

She was sure she had misunderstood. Her hair was half white. Her face was shrunken. He didn’t look younger than 55.

Then she asked how old her son was and how old he was when he got married. The math worked.

“For us, it was a turning point,” Venugopal said. “That’s when we started to think that heat ages people.”

Adelaide M. Lusambili, a researcher at the Aga Khan University in Kenya, is investigating the effects of heat on pregnant women and newborns in Kilifi County, on the Kenyan coast. In communities there, women fetch water for their families, which can mean walking long hours in the sun, even when pregnant. Studies have linked heat exposure to premature births and low birth weight babies.

The most moving stories, Lusambili said, are of women who have suffered after giving birth. Some walked long distances with 1-day-old babies on their backs, causing the babies to develop blisters on their bodies and mouths, making breastfeeding difficult.

It was enough, she said, to make her wonder whether climate change is reversing the progress Africa has made in reducing infant and child mortality.

Given the number of people who lack access to air conditioners, which are making the planet warmer by consuming large amounts of electricity, societies need to find more sustainable defenses, said Ollie Jay, a professor of heat and health at the University of Sydney.

Jay studied the body’s responses to sitting near an electric fan, wearing wet clothes, and sponging with water. For one project, he recreated a Bangladeshi garment factory in his lab to test low-cost ways to keep workers safe, including green roofs, electric fans and timed water breaks.

Humans have some ability to acclimate to hot environments. Our heart rate slows down; more blood is pumped with each hit. More sweat glands are activated. But scientists primarily understand how our bodies adapt to heat in controlled laboratory environments, not the real world, where many people can get in and out of air-conditioned homes and cars, Jay said.

And even in the lab, inducing such changes requires exposing people to uncomfortable stresses for hours a day for weeks, said Jay, who has done just that with his subjects.

“Not particularly pleasant,” he said. Hardly a practical solution to life in a suffocating future – or, for people in some places, an increasingly oppressive present. Deeper changes in the body’s adaptability will only occur on the timescale of human evolution.

Venugopal is frustrated when asked about her survey of Indian workers: “India is a hot country, so what’s the problem?”

Nobody asks what’s wrong with having a fever, but heat stroke puts the body in a similar state.

“That’s human physiology,” Venugopal said. “You can’t change that.”

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