By Ken Springer
When it’s hotter than a firecracker on the Fourth of July ~ Chill Out
With triple-digit heat waves becoming more frequent due to global warming, they may become the standard for the warmer months of the year – and we should be prepared.
Although this article will focus on hyperthermia (heat stress), extreme cold exposure, and heat exposure are opposite sides of the same coin when it comes to how a tiny portion of our brain attempts to protect us from excursions into heat stroke or cold stress.
Some 2,300 to 4,000 Americans die each year from heat-related causes. Extreme heat causes more fatalities annually than hurricanes, tornadoes and floods. Worldwide, the death toll from heat is approximately 500,000.
Beyond the susceptibility of our bodies to extreme heat, we find that heat waves are also associated with increases in homicides and road rage.
It cannot be overstated just how dangerous heat (or cold) stress is. At the same time, we can marvel at the body’s response to extreme temperatures, both high and low. So, let’s discuss the physiological aspects of thermoregulation.
First, it should be noted that in cases of heat stress, it is commonly thought that only the heart is affected. This is not the case with heat stroke. The brain, lungs, muscles, kidneys, and liver are subject to immense damage, often permanent.
Humans have evolved to maintain a core temperature between 95°F and 104°F. If our core temperature drops below 95°F, we are heading into hypothermia territory, while a core body temperature of 104°F crosses the threshold for heat stroke. This means that our existence is limited to a narrow range of 9 degrees F.
The human body is remarkable in its ability to maintain homeostasis in the face of extreme temperatures. However, we must acknowledge that once the body has used all of its physiological mechanisms to protect us, we will succumb to heat stress in the form of heat stroke, a potentially deadly condition.
So, what are the tricks our bodies use to protect us when our core temperature begins to rise beyond the safe zone? To do that, we have to examine a small structure deep inside the brain called the hypothalamus. It is charged with several regulatory functions, including hunger, thirst, satiation, sleep, hormone production and body temperature.
So, regarding heat or cold exposure, we can think of this little brain structure as our body’s thermostat. When we are exposed to cold temperatures, the hypothalamus stimulates shivering, which increases body temperature through muscular contractions, and, in hot conditions, causes us to sweat.
Sweating is a mechanism for cooling the extremities through evaporation. Sweating also uses a lot of our body’s water; hence, we should be aware of the need for increased hydration. Sweating is very effective at reducing body temperature, but that effort is stifled during periods of high humidity, when sweat runs off the body rather than evaporating.
In addition to sweating, the body uses several methods to maintain body temperature within a normal range in a hot environment. In a cold climate, we experience vasoconstriction, which reduces heat loss.
In a warm environment, we depend on vasodilation to deliver as much blood as possible to the extremities, where it loses heat to the surrounding environment convectively. How much heat we lose depends on the ambient temperature and the relative humidity.
Another heat-loss or heat-gain mechanism is conduction. A good example is when we apply hot compresses to warm us when cold: My toes and fingers get cold quickly in extreme cold, so I use heated gloves and products like Hot Hands toe warmers to stay warm when running or hiking.
In a hot environment, cold-water neck wraps leverage the dense network of blood vessels at the back of the neck to cool the blood returning to the heart, thereby reducing core temperature. The same can be said of cool vests, another way to shed heat conductively.
In foundries and steel mills, employees generally wear reflective suits and face shields to mitigate heat through radiation. OSHA, NIOSH and the CDC recommend work/rest regimens to protect workers from heat stroke.
Our brains offer one other function that can help us prevent heat or cold injuries – common sense. A couple of decades ago, a colleague decided to take a trip out west. An avid hiker, he walked out into the Mojave Desert early one morning and never returned.
His body was found a few days later, and the coroner ruled his death as heat stroke. He did die from heat stroke; however, his death was prompted by his failure to take enough water. His empty one-liter water bottle was found several miles from his body, apparently discarded.
The human body can be acclimated to heat, but only if done properly and effectively. OSHA, the CDC, and the National Institute for Occupational Safety and Health (NIOSH) all recommend a period of acclimatization in which workers are gradually exposed to high heat over two weeks.
Who is at greatest risk for heat stroke? In the work arena, construction workers account for 33% of heat stroke fatalities. Industries such as foundries, steel mills, plastics plants, glass plants, and bakeries are just a few workplaces where the risk of heat stroke is high.
Among the general population, those at higher risk of heat stroke are athletes, infants (they do not have fully developed thermoregulatory systems), and those with chronic diseases. Perhaps the most vulnerable are those 65 years and older – this group is 12 times more likely to experience heat stroke, particularly those in poor health who live without air conditioning.
I write and speak passionately about how temperature extremes affect people, including workers, athletes, outdoor enthusiasts, the young and old, and everyday people. I taught classes on heat and cold stress at the OSHA Institute in Des Plaines, Illinois, for many years. As well, I have investigated the deaths of people who have died from hypothermia and hyperthermia; tragedies that could have been avoided.
The heat wave last week gave us a small taste of what will likely become a reality in our future. Be wise, protect yourself and your family from heat stroke; stay hydrated, take breaks, and use common sense during extremely hot weather.
And, above all, keep your COOL.
Ken Springer
Ken1949bongo@gmail.com
