The human body activates specific thermoregulatory mechanisms to maintain a safe core temperature when ambient temperatures rise [3].
Understanding these biological responses is critical as extreme heatwaves increase the risk of dehydration and heatstroke, particularly in confined urban environments. Maintaining a core temperature of approximately 37 °C is necessary to prevent cellular damage [3].
Dr. Gérald Kierzek, a physician and heat expert, said that the body cools itself through several simultaneous processes. These include sweating and the vasodilation of skin vessels, which allows more blood to reach the surface to release heat [1, 2]. To support this process, the heart rate and respiration typically increase [1, 2].
These mechanisms can be overwhelmed in extreme conditions. For example, temperatures inside a metro carriage were recorded at 41 °C during a heatwave [1]. Dr. Kierzek said that physiological effects become noticeable after only 20 minutes of exposure at that temperature [1].
While some theoretical discussions suggest the human body could adapt to temperatures as high as 50 °C [4], practical evidence shows significant strain occurs at lower thresholds. In contrast, typical daytime temperatures around 30 °C are generally more manageable for the body's cooling systems [2].
When the body cannot dissipate heat fast enough, the risk of heatstroke increases. This is especially dangerous in confined spaces where air circulation is limited, such as the Paris metro [1]. Prolonged exposure to such heat leads to rapid dehydration, as the body loses critical fluids through sweat, and keeps the internal organs cool [1, 2].
“Maintaining a core temperature of approximately 37 °C is necessary to prevent cellular damage.”
The disparity between theoretical adaptation limits and actual physiological strain highlights a dangerous gap in public heat safety. While the body has robust mechanisms to handle moderate heat, the rapid onset of symptoms in confined, high-temperature environments like public transit suggests that urban infrastructure may fail to protect citizens during extreme climate events.
