How hot is it for a human being?

About the episode

This week was the hottest day on record globally on average. June was also the hottest June on record globally. Records that should be broken again and again.

But when is it somewhere too hot for us humans? According to an English researcher, the upper limit is between 40 and 50 degrees. The problem, he says, lies with our resting metabolism: the amount of energy we need to function at rest. It would accelerate at too hot temperatures.

If it’s too hot outside, your breathing quickens and your heart rate increases. The body heats up, but can no longer evacuate the heat properly. Which can cause nausea, confusion, dizziness, headache and fainting.

In 2021, the researcher will publish the first results of a series of heat experiments. While 28 degrees and 50% humidity is still manageable for most people, we have problems at 40 degrees, he says. Especially at low humidity. At 50 degrees and 50% humidity, things go wrong. Body temperature increases by one degree and heart rate increases by an average of 64%. Sweating wouldn’t help in this case.

Your degree of severity then depends, among other things, on how long you are exposed to this temperature. Researchers guess this must be fatal at some point, but obviously didn’t expect this in the experiments.

In the latest tests, they mainly looked at heart activity. Interesting in itself, because the measuring equipment is not really designed to operate at 50 degrees and 25% humidity. They saw, among other things, that the heart rate of women at this temperature was on average much higher than that of men.

Well, all of this is not saying enough, more research is needed to really say anything about what exactly would happen to the body when exposed to such extreme heat for a long time. And then there is also the psychological side of operating at very high temperatures and the differences between individuals. But with rising temperatures, this kind of research is desperately needed. And it’s clear that your body gets heavier inside as the temperature rises. So relax when the sun is shining brightly.

Learn more here: Just how “too hot” is it for humans? Previous work by this researcher: The metabolic upper critical temperature of the human thermoneutral zone.