This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

reputable news agency

proofread

Saudi hajj pilgrims' deaths highlight how extreme heat kills

Pilgrims at the hajj were laid low by the scorching heat
Pilgrims at the hajj were laid low by the scorching heat.

More than 1,000 people have died at this year's hajj pilgrimage in extreme heat in Saudi Arabia, an AFP tally showed on Thursday.

The pilgrimage involved hours of walking and praying in a country where temperatures reached 51.8 degrees Celsius (125 Fahrenheit) this week.

The World Health Organisation (WHO) has calculated that heat kills at least half a million people every year but warns that the real figure could be up to 30 times higher.

Here a scientist explains how damages the body and how physical activity outdoors raises the risk.

Heat effect on body

In normal conditions, the body regulates its own like a thermostat, holding it steady at about 36.8C (98.2F).

When outside heat rises, the body cools itself by raising blood-flow to vessels near the skin.

This emits heat at the surface, while perspiration also cools the outside of the body.

"To ensure the correct functioning of the cells, enzymes and , the body's temperature must stay constant, whatever the external conditions," said Pieter Vancamp, a neurobiologist at the French research institute INRAE.

Dying of heat

During an activity such as the hajj, where pilgrims spend hours outdoors in the sun, "the body can quickly become exhausted and can no longer find the reserves of water needed to perspire", Vancamp said.

Effects of heat stress on the body
Effects of heat stress on the body.

Then the kidneys, heart and brain risk overheating and "stop working", he added.

When the body's natural thermostat is overwhelmed in this way, symptoms strike: fatigue, headaches, fever and broken sleep.

These can herald more serious effects, such as dehydration, which chokes off water to the vital organs.

The biggest risk is heatstroke, when the body's temperature exceeds 40C (104F).

"The body has its limits," said Vancamp. "When the weather is too hot or when extreme heat is combined with physical activity, for example, the body can find itself unable to self-regulate."

Aggravating factors

Babies, the elderly, people with and outdoor workers are most at risk.

The number of sweat glands in the body decreases with age, leaving the body less able to cool itself.

"Several factors determine our reaction to heat: age, , , genes," said Vancamp.

Graphic explaining wet-bulb temperature
Graphic explaining wet-bulb temperature.

"But when the heat is too strong, even young, healthy bodies can lack the energy to keep the temperature close to 37C."

The WHO warns that hot nights pose a particular health risk.

Nighttime heat gives the body no chance to cool down, leading to a rise in heart attacks.

Graphic explaining the most common health effects or symptoms caused by extreme heat
Graphic explaining the most common health effects or symptoms caused by extreme heat.

More heat deaths in future?

Worldwide, people were exposed to an average of 86 days of life-threatening temperatures in 2022, according to The Lancet Countdown report last year.

The number of people over 65 who died from heat rose by 85 percent between the periods 1991-2000 and 2013-2022, the leading medical journal added.

Climate change caused by humans burning is increasing and other .

On the current trajectory, the world is on track to warm about 2.7C above the pre-industrial average by the end of this century, according to Climate Action Tracker.

The Lancet Countdown projected that under a 2C warming scenario, about five times as many people will die from the heat each year by 2050.

© 2024 AFP

Citation: Saudi hajj pilgrims' deaths highlight how extreme heat kills (2024, June 20) retrieved 14 July 2024 from https://phys.org/news/2024-06-saudi-hajj-pilgrims-deaths-highlight.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Explore further

Michael Mosley reportedly died from heat exhaustion. How can extreme heat turn deadly?

16 shares

Feedback to editors