When do high temperatures become deadly?

The summer of 2024 has the potential to become the hottest season in recorded history. High temperatures mercilessly affect societies globally – from Poland, to Greece, to Spain, not sparing the United States either, where heat waves bring serious health and social consequences. The increasing number of deaths among vulnerable groups resulting from extreme conditions is compounding existing health problems, contributing to human tragedies. Scientists have studied what is the threshold of our endurance.

The limits of human endurance

As climate change leads to more frequent and intense heat waves, scientists are intensively studying the limits of the human body’s ability to withstand extreme heat and humidity conditions. Recent studies show that these limits are much lower than previously thought. The key parameter used to determine this is the so-called. wet-bulb temperature. This measurement combines air temperature with humidity to determine potential heat stress on living organisms.

Method of Measurement:

• Dry thermometer: measures standard air temperature.
• Wet thermometer: its sensor is wrapped in a wet cloth, and the evaporation of water from the cloth lowers the reading temperature.
• Measurement: the difference between the dry and wet thermometer temperature gives the relative humidity value.

This method assesses how effectively the body can cool itself through perspiration, which is critical in extreme heat conditions.

Based on research conducted in 2010. Climatologists have determined that a wet thermometer temperature of 35°C is the upper limit of human survival and adaptability without the need for cooling methods. At this value, the body is unable to dissipate heat effectively, leading to a rapid rise in internal temperature and potentially fatal heat stroke in about six hours. However, recent studies show that the actual endurance limits may be much lower.

A study published in the Journal of Applied Physiology conducted in a specially heated room found that the wet thermometer temperature threshold for young and healthy people oscillates between 30-31°C. At these values, the temperature poses significant health risks, especially for seniors and those with comorbidities. The results of the study, published last winter, emphasize that the limit of resistance to high temperatures is individual for each person and depends on a number of factors, such as age, sun exposure, health status, and level of physical activity. As the study’s author, Jennifer Vanos, points out, the assumption of a universal threshold for survival is flawed and can be dangerous.

Tragic balance sheet overseas

Recent heat waves have covered much of the United States, affecting more than 135 million people in 48 states. Record temperatures, often exceeding 100 degrees Fahrenheit (37.8 degrees Celsius), have been recorded in cities such as Las Vegas, Phoenix and Salt Lake City. In the first days of July alone, 14 heat-related deaths were reported in Santa Clara County, California alone. In Sacramento, a 58-year-old man died of heat stroke, and in Death Valley National Park, a motorcyclist lost his life when the temperature reached 127 degrees Fahrenheit (53.3°C).

In Arizona, a 4-month-old girl died after losing consciousness on a boat on Lake Havasu due to overheating, according to station KJZZ. The effects of the heat waves were also felt on the East Coast, where a record temperature of 106 degrees Fahrenheit (41.1°C) was recorded in Raleigh. The Maryland Department of Health has reported two heat-related deaths.

Number of deaths may be underestimated

The total number of deaths caused by the recent heat waves may not yet be fully known, and experts in the field of health and safety are also working to determine the number of deaths. Public health officials warn that official statistics may be understated. Heat is the leading cause of weather-related deaths in the US, ahead of hurricanes, tornadoes and forest fires. Statistics show a steady increase in heat-related deaths: from about 1,600 in 2021, to 1,700 in 2022 and more than 2,300 in 2023. However, scientists, coroners and doctors are finding it difficult to accurately determine the number of victims, as heat-related deaths are often misclassified as heart failure or other cardiovascular problems, even when heat is the main trigger.

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