How much heat can you bear?


A young man cools himself with water in the sun. — Reuters/File
A young man cools himself with water in the sun. — Reuters/File

As global temperatures rise, the United Nations has warned we are now living in an era of “global boiling”.

But an oft-overlooked question is how the changing climate affects our bodies and health.

We might have the answer through an interesting experiment conducted by Prof Damian Bailey from the University of South Wales, UK.

According to a report on BBC, Bailey experimented with recreating a typical heatwave encounter and observing its impacts on the human body.

The experiment started by placing the test subject at 21°C and then raising the temperature to 35°C and 40.3°C — equivalent to the hottest day in the UK.

Prof Bailey’s environmental chamber is a room where temperature, humidity and oxygen levels are tightly controlled.

At 21°C, Prof Bailey remarked to the subject: “Blood pressure is working nicely, heart rate is working nicely, all of the physiological signals at the moment are telling me that you’re in spiffing shape.”

But as the external temperature was cranked up to about 37°C, his reports showed that “the thermostat in the brain, or hypothalamus, is constantly … [sending] out all of these signals to try to maintain [the body’s core temprature]”.

At around 37°C, the subject is redder because the blood vessels near the skin’s surface are dilating to allow heat to escape into the air.

The subject also started to sweat slightly.

Then, the temperature was raised further still to 40.3°C.

At the end of the test, the following observations were made about changes to the body:

  • Blood flow to the brain fell 8.5%
  • Core body temperature: 36.2 t0 37.5°C
  • Breaths: up from 10 to 15 per minute
  • Sweat: 400ml during the one-hour experiment
  • Heart Rate: 54 to 87 beats per minute
  • Skin temperature: 31.3 to 35.4C
  • Memory puzzle score: fell from 23/30 to 17/30

What does this mean for me?

As heatwaves become more frequent, severe and longer in duration, they’re becoming more humid too, researcher Rachel Cottle said.

This is a matter of concern as higher humidity levels may contribute to sharp increases in core body temperatures, which is dangerous for people.

“That’s when it becomes dangerous. Our core temperature starts to rise and that can lead to organ failure,” Cottle said.

In Pakistan and India last year, a severe heatwave with critical temperatures and high humidity became life-threatening.

“Once the core temperature rises to around about 41-42 degrees centigrade we start to see really, really significant problems and if not treated the individual will actually die as a result, succumbing to hyperthermia,” says Prof Bailey.

What should I do?

Some tips for coping with heat and heatstrokes are:

  • Stay in the shade.
  • Wear loose-fitting clothes.
  • Keep your house cool.
  • Don’t exercise in the hottest parts of the day.
  • Stay hydrated.
  • Try not to get sunburned. 


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