We now know when heat becomes dangerous to our bodies

This was discovered by an American research team that examined the combinations of temperature and humidity harmful to the human body.

Many are wondering with the increasing length and frequency of heat waves due to climate change How hot the human body can handle. And above all, what is the maximum beyond which it is dangerous to carry out even normal daily activities. The answer to these questions comes from a research team at Penn State University that conducted new research to assess the threshold beyond which our body cannot maintain a stable internal temperature and we are at risk of hyperthermia.

The study recently published in Journal of Applied Physiologystarts from the assumption that in addition to the temperature we read on the thermometer, our perception of heat also depends From the moisture in the air, which shows how the combination of these two factors strongly influences the maximum that a person can tolerate. “mostly – Scientists point out – Referring to a study published in 2010 (Sherwood et al. PNAS), which indicated that a wet bulb temperature of 35°C (equivalent to 35°C at 100% humidity, or 46°C at 50% humidity) was the upper limit of human safety, beyond which heatstroke or death from prolonged exposure could occur. . However, this limitation has only recently been tested in laboratories, and the results of these tests show that combinations of low temperature and humidity They are more harmful than previously thought“.

Specifically, the researchers found that this environmental maximum is less than 35 °C in theory, and about 31 °C in a wet bulb (equivalent to 31 °C at 100% humidity) which is equivalent to 38°C at 60% humidity, even for young and healthy people.

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The combination of temperature and relative humidity within critical environmental limits, above which the core body temperature rises.  The boundary between the yellow and red areas represents the average critical environmental limit for young men and women who engage in light physical activities.

The combination of temperature and relative humidity within critical environmental limits, above which the core body temperature rises. The boundary between the yellow and red areas represents the average critical environmental limit for young men and women who engage in light physical activities.

For older adults, who are more susceptible to heat, this threshold is likely to be even lower, they highlight scientists who, as part of the PSU HEAT (Human Environmental Age Thresholds) project, are examining how hot and humid the environment must have been before. Older adults begin to have problems withstanding heat stress. “If we look at heatwave statistics, most people who die during these extreme events They are old – He explained. Larry Kenny, professor of physiology and kinesiology at Penn State University and senior author of the study. The climate is changing, so there will be more (and more intense) heat waves. The population is also changing, so there will be more and more elderly people. So it’s really important to study the confluence of these two sides“.

How hot is the human body?

In this study, before focusing their work on older subjects, the researchers recruited them 24 participants aged 18-34 years, who was asked to take a tiny wireless measuring device contained within a capsule to measure basal body temperature during the experiment. Then each participant was allowed to enter Specialized Environmental Roomwith adjustable temperatures and humidity levels, and light physical activities, such as cycling or walking slowly on a treadmill while the camera was gradually brought to different combinations of temperature and humidity to assess the so-called critical environmental limit, this is the point beyond which the human body becomes unable to maintain a relatively stable internal temperature over time. In other words, after this threshold, the internal temperature begins to increase and the risk of reporting heat-related consequences increases with prolonged exposure.

After analyzing the data, the researchers found that the critical temperatures of wet bulbs vary 25°C to 28°C in hot, dry environments and 30°C to 31°C in hot, humid environments, reporting theoretical temperatures below 35 °C. “Our findings suggest that in the humid regions of the world, we should start to worry, even for the young and healthy, when the wet bulb temperature rises above 31 degrees. Kenny added. As we continue our research, we will explore what this limit is for older people, as it is likely to be lower as well“.

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