Health effects of extreme heat

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

Over the decades, Dr. Kenny has seen how heat stress affects many people in an intense environment: football players, soldiers in defensive suits, distance runners in the Sahara.

Of late, however, his research has focused on a more mundane subject: the common man. Do daily work Climate change is causing the planet to collapse.

Heat warnings and extreme heat warnings were effective throughout most of the eastern interior of the United States over the record-breaking heat weekend in the country’s southwest on Monday. According to the National Weather Service, the heat will move northeast in the next few days, in the upper Mississippi Valley, the Great Lakes West and the Ohio Valley.

Intense heat waves are now affecting different parts of the world with alarming regularity, scientists are researching how life in a heated world will get sick and kill us. The aim is to better understand how many more people will be affected by heat-related illnesses and how frequent and severe their suffering will be. And how to better protect the weakest.

One thing is for sure, scientists say: the heat waves of the past two decades are not a good predictor of the risks we may face in the coming decades. Already, the link between greenhouse gas emissions and heated temperatures is so clear that some researchers say that there is no point in trying to determine whether today’s extreme heat waves could have occurred two centuries ago, before humans began warming the planet. None of them could.

And if global warming is not slowed down, the warmer heat waves that many people experience will only be their summer norm, says Matthew Huber, a climate scientist at Purdue University. “It’s not going to be something you can escape.”

Dr. Huber said it is difficult for scientists to identify how these climate changes will greatly affect human health and well-being, especially in the developing world, where large numbers of people are already suffering but lack good data. Heat stress results from a number of factors – humidity, sun, wind, hydration, clothing, physical fitness – and a range of damages that make it difficult to project future effects with any accuracy.

There was not enough study, said. Instead of feeling the occasional summer roast, Huber says, it’s about surviving in a warm world full time. “We don’t know the long-term consequences of waking up every day, working three hours in the scorching heat, sweating like crazy and then returning home,” he said.

These problems are drawing on the growing urgency of researchers, such as Dr. Kenny, who did not always think of themselves as climate scientists. For a recent study, she and her colleagues placed young, healthy men and women in specially designed chambers, where they rode an exercise cycle at low intensity. Then the researchers dial up heat and humidity.

They found that their subjects began to dangerously overheat at much lower “wet-bulb” temperatures – a measure responsible for both heat and magnesium – based on previous theoretical assumptions made by climate scientists.

Effectively, under the condition of steam-bath, our body absorbs heat from the environment to cool itself as quickly as it can sweat. And “unfortunately for humans, we don’t sweat too much to keep going,” Dr. Kenny said.

Heat is the most destructive threat to climate change, destroying not only the landscape and the ecosystem and infrastructure, but also the depths of the individual human body.

Heat victims often die alone in their own homes. In addition to heatstroke, it can cause cardiovascular collapse and kidney failure. It damages our organs and cells, even our DNA. Its incidence increases manifold in people of very old and very young age 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 function are impaired. Excess heat is associated with greater crime, anxiety, depression and suicide.

Tolls on the body can be interestingly personal. George Havenith, director of the Environmental Ergonomics Research Center at Loughborough University in England, recalls an experiment many years ago with a large group of subjects. They wore the same clothes and did the same thing for an hour at 95 degrees heat and 80 percent humidity. But in the end, their body temperature ranged from 100 degrees to 102.6 degrees Fahrenheit.

“We’re doing a lot of work trying to figure out why one person ends up on one side of the spectrum and the other on the other,” he said.

For years, Vidya Venugopal, a professor of environmental health at Sri Ramchandra University in Chennai, India, has been studying how to heat workers in steel mills, car factories and brick kilns in India. Many of them are suffering from kidney stones due to severe dehydration.

A meeting a decade ago remained with him. He met a steel worker who had been working 8- to 12-hour days near a furnace for 20 years. When he asked her how old she was, she said 38 to 40.

He was sure he had misunderstood. Her hair was half white. His face went wrinkled. He was not shown to be under 55 years of age.

So she asked how old her child was and how old she was when she got married. Math check out.

“For us, it was a turning point,” said Dr. Venugopal. “That’s when we start thinking, heat increases human lifespan.”

Adelaide M. Lusambili, a researcher at Aga Khan University in Kenya, is investigating the effects of heat on pregnant women and newborns in Kilifi County off the coast of Kenya. In the communities there, women fetch water for their families, which means long walks in the sun while pregnant. Studies have shown that heat exposure is associated with preterm birth and low birth weight babies.

The most heartbreaking story, Dr. Lusambili said, is of women who suffer after childbirth. Some have walked long distances with their 1-day-old babies on their backs, causing blisters on the baby’s body and face and making it difficult to breastfeed.

“Everything is enough,” he said, to consider whether climate change is reversing the progress Africa has made in reducing neonatal and infant mortality.

Oli J, a professor of heat and health at the University of Sydney, says how many people do not have access to air conditioners that are themselves heating up the planet using large amounts of electricity, so societies need to find more sustainable defense.

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

Humans have some ability to adapt to hot environments. Our heart rate decreases; More blood is pumped with each stroke. More sweat glands are activated. But scientists initially understand how our bodies adapt to heat in controlled laboratory settings, not in the real world, where many people can laugh in and out of air-conditioned homes and cars, Dr. J. said.

Even in the lab, people have to endure weeks of uncomfortable strain to induce such changes, says Dr. Jay, who has done just that with his subjects.

“It’s not particularly pleasant,” he said. Hardly a real solution for life in a suffocating future – or, for people in some places, an increasingly oppressive present. Further profound changes in the body’s adaptive capacity will only occur on a scale during human evolution.

When Dr. Venugopal asked about his research on Indian workers, he was disappointed, “India is a hot country, so what’s the big deal?”

No one asks what the big deal is with a fever, but a heatstroke leaves the body in a similar state.

“It’s human physiology,” said Dr. Venugopal. “You cannot change this.”

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