How the body reacts to heat
Published: Monday, Aug 12th 2024, 10:50
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Heat can be life-threatening for the human body. However, it is not possible to say in general terms at what temperature heat is fatal for humans.
Basically, in order to survive, humans need to maintain their body temperature at around 37 degrees Celsius. If the temperature rises above this for a longer period of time, it becomes life-threatening.
When the body temperature rises in the heat, the body initiates countermeasures to lower the temperature. To maintain this temperature, the body dissipates heat through the skin. The skin vessels become wider in order to dissipate heat over as large an area as possible. At the same time, blood flow to the skin increases. This lowers blood pressure and increases the heart rate - a challenge for the circulatory system.
Sophisticated cooling mechanism
If the surface of the skin becomes too hot, the body tries to cool it down by sweating. It brings water to the surface of the skin, where it evaporates. This process consumes energy. Energy that is obtained from heat. The evaporation of sweat therefore removes heat from the body and cools it down.
This is where the next danger for humans lurks: Sweating causes the body to lose fluids, increasing the risk of dehydration. At the same time, the body loses many important salts, magnesium and other electrolytes.
Humidity plays a major role
In addition to the ambient temperature, humidity plays a major role in the cooling mechanism. At high humidity, the environment is already saturated with moisture. This means that the sweat on the skin evaporates more slowly or not at all. As a result, the body is less able to cool down. The risk of overheating increases.
In this context, experts refer to the so-called wet bulb or cold limit temperature, the lowest temperature that can be achieved through evaporative cooling. At 100 percent humidity, the ambient temperature and the cooling limit temperature are the same. At a temperature of 30 degrees Celsius and a relative humidity of 50 percent, the wet bulb temperature is 22.3 degrees Celsius.
As a study by Pennsylvania State University in 2022 showed, a cooling limit temperature of over 31 degrees leads to overheating, or hyperthermia, in healthy young people in the shade. This means that at a humidity of 100 percent, 31 degrees could be enough to lead to overheating. At a humidity of 20 percent, this value is not quite reached even at an air temperature of 55 degrees.
Such temperatures have not yet been reached in Switzerland. However, such events are increasing worldwide. According to a study published last year in the journal "Nature Sustainability", a third of humanity could be living in regions with inhumane temperatures by the end of this century.
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