(Web Desk) - Inside our bodies, there are multiple reasons hot weather can be deadly.
Heat exhaustion and heat stroke are serious conditions caused by heat, and these can be fatal on their own.
Heat is also an exacerbating factor for certain preexisting conditions or cardiovascular diseases, the category that includes strokes and heart attacks.
And there’s a separate form of heat stroke that affects athletes, because the way exercise works in the body can become a runaway heating process that must be stopped by medical professionals.
The major way heat causes injury to the body is through water.
The body’s water equilibrium is precise and temperamental, and it’s highly exposed to the surrounding air through our skin and respiration.
In hot weather, and especially hot and dry weather, water can evaporate from the skin and through respiration so rapidly that it can’t be replaced in time.
Evaporating sweat cools the body, but too much water lost through sweating leads to dehydration.
Did you know? Extreme heat is the leading cause of weather-related deaths in the U.S.
The body’s temperature itself is affected by blood circulation. Having impaired blood circulation is like running your car’s engine when the oil has drained out.
Blood circulation is one of the major ways the inside of the body stays at the right temperature, and one of the only ways it is able to do that.
When we breathe in, the air is almost always a cooler temperature than the inside of our bodies, and that cools the blood as it spreads out into the lungs for oxygenation.
Externally, the upper limit of the human body’s thermoneutral zone—the ambient temperature range in which the body can effectively maintain its temperature and equilibrium—likely falls somewhere between 104 and 122 degrees Fahrenheit, according to a 2021 study published in Physiology Report.
Once the air temperature hits 122 degrees, our bodies can no longer dissipate heat and our core temperature rises.
But another study cites a much lower limit of 89.6 degrees—the temperature at which humans start sweating. Beyond air temperature, humidity plays a big role too, and the higher the humidity the harder our bodies have to work to stay cool.
The limits for internal body temperature are even more restrictive.
According to MedlinePlus, brain damage can occur once the body reaches an internal temperature of 107.6 degrees Fahrenheit.
A 2022 Outside article on heat stroke cites the highest known body temperature that a human was able to survive: “The highest body temperature measured was only 17 degrees above normal.
Willie Jones, a 52-year-old Atlanta man, was rescued from his apartment during a heat wave in 1980. His internal temperature was 115.7.” What about extreme cold? According to that same Outside article, “The lowest body temperature a human has been known to survive is 56.7 degrees [Fahrenheit], nearly 42 degrees below normal.”
This makes intuitive sense, now that we understand the effects of heat on evaporation rates.
As body temperature grows colder, it causes different problems, but does not lead to dehydration.
In fact, medical researchers are exploring a new technology called emergency preservation and resuscitation, where patients are cooled intravenously down to 50 degrees Fahrenheit in order to slow severe blood loss while they undergo emergency surgery for traumatic injury.
Cold temperatures slow the blood, which can cause more severe cold weather injuries like frostbite. Without blood to warm the tissue, it freezes, and those ice crystals damage the cells and tissue. As the climate warms, people will need to adapt in order to survive. This year, residents of Phoenix, Arizona, experienced 31 days in a row of highs at or above 110 degrees Fahrenheit. That’s in a 12-month period—the hottest ever recorded for the entire planet.
As climate change continues, especially without efforts by the world’s governments to counteract it, more people will become climate refugees. Some places, like Arizona, may become uninhabitable altogether.