Scientists say upper limit of human heat tolerance is 'even lower' than previously thought

Humans can be in danger at as low as 85º, researchers claim.
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A man refills a water bottle in Barcelona, Spain, during a heat wave, Jul. 13
A man refills a water bottle in Barcelona, Spain, during a heat wave, Jul. 13
(Europa Press News/Getty)

Researchers out of Penn State University this week claim that the upper bound of safe heat tolerance for human beings is "even lower" than earlier thought, a factor which could prove dangerous in the event of theoretical temperature spikes amid changing climate conditions. 

The researchers, including one professor of physiology and several postdoctoral researchers and students, argued in an op-ed at the Pennsylvania Capital-Star that "the combination of [heat and humidity] can get dangerous faster than scientists previously believed."

At issue is the concept of "wet-bulb temperature," or what the researchers describe as "extreme heat paired with high humidity."

Earlier research, they said, pointed to an upper safety limit of around 95º Fahrenheit at 100% humidity, "beyond which the human body can no longer cool itself" effectively. 

Laboratory observations on human subjects, however, indicate that "this upper environmental limit is even lower" than that, they argued, is closer to about 88º Fahrenheit at 100% humidity. 

"Current heat waves around the globe are approaching, if not exceeding, these limits," they write. 

The scientists argued that "staying well hydrated and seeking areas in which to cool down – even for short periods – are important in high heat." 

They further argued that humanity "must tackle head-on" what they said is the pressing issue of climate change.