A new study from the University of Ottawa’s Human and Environmental Physiology Research Unit (HEPRU) has confirmed that humans can tolerate far less heat than previously estimated, with dire implications as global temperatures rise.
Published in PNAS, the research highlights the urgent need to address climate-driven health risks.
Led by Dr. Robert D. Meade and Dr. Glen Kenny, the study exposed 12 volunteers to extreme conditions of 42C and 57% humidity—equivalent to a humidex of 62C—to test thermoregulation limits.
“Recent projections suggest that large geographical areas will soon experience heat and humidity exceeding limits for human thermoregulation,” researchers noted in the paper.
Participants’ core temperatures rose uncontrollably during prolonged exposure, with many unable to complete the nine-hour trial. “The results were clear: once thresholds are crossed, the body cannot cool itself,” said Meade.
The research validated “thermal-step protocols,” a decades-old method for estimating human heat limits, but revealed these thresholds are significantly lower than past models suggested.
Dr. Kenny emphasised the urgency: “Regions may soon experience heat and humidity levels exceeding safe survival limits. This data is critical as global temperatures climb”.
The study emphasizes the increasing risk of heat-related illnesses, especially for vulnerable people, as heatwaves get worse.
The study emphasizes the increasing risk of heat-related illnesses, especially for vulnerable people, as heatwaves get worse.
Given that even healthy people experience physiological strain in harsh environments, cities must now reconsider their safety regulations. “This helps predict where and when heat will become unlivable,” Kenny emphasized, emphasizing the importance of incorporating physiological data into climate models.
This study provided more accurate findings by simulating real-world heat exposure rather than relying on artificial heating suits like previous lab simulations did.
In order to simulate extended heatwave conditions, participants endured daylong trials that were somewhat above their thermoregulatory limitations. The results are consistent with climate projections that suggest large areas, including portions of the Middle East and South Asia, may soon exceed the criteria for livable heat and humidity.
