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OTTAWA, ON – A groundbreaking study conducted by the University of Ottawa’s Human and Environmental Physiology Research Unit (HEPRU) has delivered a stark warning: the human body’s ability to withstand extreme heat is significantly less than previously understood. The research, published in the prestigious journal Proceedings of the National Academy of Sciences, underscores the urgent need to address the escalating impacts of climate change on human health.
Led by Dr. Robert D. Meade and Dr. Glen Kenny, the study utilized a rigorous approach, exposing 12 volunteers to varying heat and humidity conditions. Unlike previous research, this study included a prolonged, day-long exposure to conditions just above the estimated thermoregulatory limit. Participants were subjected to extreme conditions, specifically 42°C with 57% humidity, translating to a humidex of approximately 62°C.
“Our research provides important data supporting recent suggestions that the conditions under which humans can effectively regulate their body temperature are actually much lower than earlier models suggested,” stated Dr. Kenny. “This is critical information as we face increasing global temperatures.”
The results were alarming. “The results were clear. The participants’ core temperature streamed upwards unabated, and many participants were unable to finish the 9-hour exposure,” Dr. Meade explained. “This data provides the first direct validation of thermal step protocols, which have been used to estimate upper limits for thermoregulation for nearly 50 years.”
The study’s findings indicate that many regions may soon experience heat and humidity levels that exceed safe limits for human survival. This revelation has significant implications for climate modeling and public health policies.
“Our findings are especially timely, given that estimated limits for thermoregulation are being increasingly incorporated into large-scale climate modeling,” Dr. Meade added. “They also underscore the physiological strain experienced during prolonged exposure to extreme heat, which is becoming more common due to climate change.”
The researchers emphasized the importance of integrating physiological data with climate models to better predict and prepare for heat-related health issues. As cities worldwide grapple with rising temperatures, this research aims to inform and guide public safety measures.
“By integrating physiological data with climate models, we hope to better predict and prepare for heat-related health issues,” Dr. Kenny concluded.
The study serves as a critical reminder of the vulnerability of human physiology in the face of increasingly extreme environmental conditions.
More information: Robert D. Meade et al, Validating new limits for human thermoregulation, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2421281122
Journal information: Proceedings of the National Academy of Sciences
Disclaimer: This article is based on the provided information and should not be taken as medical advice. Readers are encouraged to consult with healthcare professionals for any health concerns. The information presented is based on a single study and further research may be needed to confirm these findings. Climate models are complex and predictions may vary.(
