Maximum temperature human body can survive identified

Scientists have identified the maximum mix of heat and humidity a human body can survive.

Even a healthy young person will die after enduring six hours of 35-degree Celsius (95 Fahrenheit) warmth when coupled with 100 percent humidity, but new research shows that threshold could be significantly lower.

At this point sweat - the body's main tool for bringing down its core temperature - no longer evaporates off the skin, eventually leading to heatstroke, organ failure and death.

This critical limit, which occurs at 35 degrees of what is known "wet bulb temperature," has only been breached around a dozen times, mostly in South Asia and the Persian Gulf, Colin Raymond of NASA's Jet Propulsion Laboratory told AFP.

None of those instances lasted more than two hours, meaning there have never been any "mass mortality events" linked to this limit of human survival, said Raymond, who led a major study on the subject.

But extreme heat does not need to be anywhere near that level to kill people, and everyone has a different threshold depending on their age, health and other social and economic factors, experts say.

For example, more than 61,000 people are estimated to have died due to the heat last summer in Europe, where there is rarely enough humidity to create dangerous wet bulb temperatures.

But as global temperatures rise - last month was confirmed on Tuesday as the hottest in recorded history - scientists warn that dangerous wet bulb events will also become more common.

The theorized human survival limit of 35C wet bulb temperature represents 35C of dry heat as well as 100 percent humidity or 46C at 50 percent humidity.

To test this limit, researchers at Pennsylvania State University in the United States measured the core temperatures of young, healthy people inside a heat chamber.

They found that participants reached their "critical environmental limit" - when their body could not stop their core temperature from continuing to rise - at 30.6C wet bulb temperature, well below the previously theorized 35C.

The team estimated that it would take between five to seven hours before such conditions would reach "really, really dangerous core temperatures," Daniel Vecellio, who worked on the research, told AFP.