The science behind heat-related illness and what to do about it.
By Randy DeVaul
Anyone exposed to high heat and high humidity can be at risk of suffering from a heat-related illness, which can also lead to injury. The term “heat stress” is used so frequently that it becomes almost cliché – to the point that we may also tune it out. We get complacent, we get bored, we believe we have heard it all. Yet every year, workers experience heat-related injuries and illnesses. Why?
Here is a basic review of how heat stress occurs, the signs and symptoms of the three most common types of heat stress, and a discussion of prevention tips.
How heat stress occurs
Our bodies have many built-in mechanisms to maintain normal and consistent core temperature. As our bodies are exposed to heat, the brain triggers the blood vessels to expand closer to the surface of the skin and the warmer temperature triggers the sweat glands, located in the dermal skin layer. As sweat works through the pores to the outside (epidermal) layer of skin, the sweat becomes exposed to air. This causes the evaporation process to function during which the heated sweat is wicked away and the skin surface is cooled. In physics, heat always travels to cold, so as the blood vessels have heat removed, sweat provides the exposed skin surface with water and the air evaporates it away. The body temperature begins to cool and normal body temperature is maintained.
|Heat Cramps||Heat Exhaustion||Heat Stroke|
|Painful muscle spasms||Weakness, nausea||Extreme emergency|
|Profuse sweating||Profuse sweating||Stop/no sweating|
|Fatigue||Mental confusion||Possible unconsciousness|
|Normal body temperature||Temperature 99-103 F||Temperature 104+ F|
|Loss of fluids thru sweating||Loss of more body fluids||Body dehydrated|
|Normal, wet, warm skin||Pale, cool, clammy skin||Red, hot, dry skin|
|Treat with sips of tepid water (not salt); get to cool area||Treat with sips of tepid water (not salt); get to cool area||Treat with rapid cooling of body; emergency transport to a health care facility|
When working in heat with high humidity, the air becomes saturated and evaporation of water into the air cannot effectively take place. This is what happens when you walk outside on a hot, humid summer day and immediately feel “sticky.” The air is full of water molecules, and our sensory nerves close to the surface of the skin “feel” its presence. Then as we begin to sweat, there is nowhere for the water to go and it stays on the body. Soon our internal mechanics begin to change, causing chemical changes inside our bodies, as well.
In already-saturated air in hot, humid environments, our problem worsens as we attempt to perform work. Heavy exertion that causes us to sweat in the first place compounds the problem and prevents the body from cooling itself fast enough. This results in elevated body temperature with little or no evaporation of sweat. Body fluids, with the all-important electrolytes (sodium, potassium, etc.) are lost. It is possible to lose up to three gallons of body fluids each day through sweating and breathing – perspiration and respiration. Without appropriately replacing such fluids and electrolytes, bad things can happen.
Heat-related injuries occur because normal reactions to heat can cause distractions, impair judgment and encourage workers to make poor choices. For example, safety goggles, glasses or welding hoods that fog up while attempting to perform tasks may tempt the worker to remove the eye protection, thus creating an exposure to an already known eye hazard. In addition, shortcuts become popular to reduce the strain or effort in the task or to shorten the exposure to the heat, setting up workers for an injury. Hard hats are removed, leathers aren’t worn, ear protection is taken off, and the list goes on.
Slippery, sweaty palms can prevent a worker from gripping a tool firmly or ensuring a good grip when carrying materials or parts. Not only can the person become injured if he drops the material or the tool slips from his hand, but there is also the risk of damaging the item as well.
Exposure to the heat can also create an increase in blood pressure, dizziness, headaches, possible fainting, early onset of fatigue, heat rash and other skin irritations – all things that can distract a worker from the focus of the task at hand.
Another condition that develops in a high-heat, high-humidity environment is a change in mood or behavior. This chemical imbalance in the body can cause even little irritations to develop into workplace violence issues.
Heat stress conditions
The three most common heat stress conditions are heat cramps, heat exhaustion and heat stroke. To the left is a summary of signs, symptoms and treatment for each.
Heat cramps occur when muscles become overexerted and electrolytes are removed from the body due to sweating. The active muscles may begin to spasm, causing painful cramps. Treatments include giving the victim a 15-minute break in a cooler environment and giving him some tepid or cool water. A little electrolyte-replacement fluid is OK, too, as long as it is balanced with water intake. For the remainder of the shift, the worker should perform other duties, if available, to enable the active muscles and electrolytes to return to pre-stress status.
Heat exhaustion occurs with rapid, heavy sweating when electrolytes are lost through the sweat glands. The victim will exhibit symptoms of shock: skin that is pale, cool and clammy to the touch (though internal temperatures would indicate a low-grade fever). The person will feel weak or even nauseated. In more advanced stages, look for signs of mental confusion. Treatment includes getting the worker to a cooler environment, cool or tepid water to drink, and a light-duty assignment for the remainder of the shift. Watch the worker carefully during the next day’s shift to ensure signs and symptoms do not return.
Heat stroke is a true medical emergency. In this situation, the person has passed through the heat exhaustion phase and, if left unchecked, will move into this life-threatening condition. Sweat glands and other cells are dehydrating, and the water balance and electrolyte balance are shot. The victim of heat stroke will appear flush/red, very hot to the touch and very dry – even clothing will begin drying from the inside out. Internal core temperatures can exceed 105 F, and the person will be losing or will have lost consciousness.
Heat stroke requires immediate action – ice or very cold water on the skin, fans or moving air across the victim to expedite evaporation of heat off the body, and an immediate 9-1-1 call. Advise the dispatcher/operator that heat stroke is suspected so the rescue crew will know to pack the IV fluids in ice while enroute to the plant or job site. You cannot cool the person too quickly or for too long. Keep chilling the victim until the ambulance arrives, then the crew will continue to chill the person on the way to the hospital. This person will most likely be admitted to the hospital for observation and miss the next day’s work. It may take a week or longer for the heat stroke victim to be able to go back into the heat, and then it will be light duty for a while.
Heat-related problems often occur during the first few days of summer or with wide swings in temperatures. Watch closely when new hires are working in high-heat environments, when experienced workers return from vacation, or when reassigning workers into a higher-heat work environment than they are normally accustomed.
Most precasters work in a hot, humid environment at least some of the year. So what can we do to protect ourselves and our people in these situations? To prevent or minimize heat stress from developing, we can take some common sense measures.
- Allow time for your body to become conditioned to the heat. This is especially important if you have been off for a while – vacation, temporary transfer of duties to cooler work area, etc. Our bodies will acclimate to the temperature changes if we just give them a chance.
- Let employees take frequent, short breaks versus infrequent, long breaks. This equates to five to 10 minutes each hour when workers are exposed to temperatures exceeding 88 F, according to the summary findings by the National Institute on Safety and Health (NIOSH), and perhaps 15-20 minutes for lunch rather than a half hour or longer.
- Stress the importance of avoiding dehydration by drinking plenty of fluids. Encourage workers to drink at least eight 8-ounce glasses of water at an absolute minimum. Tell them not to wait until they feel thirsty – you will never feel thirsty enough. By the time our bodies tell us we need a drink, we have already lost too much fluid. NOTE: If you drink electrolyte-replacement fluids, DO NOT drink those fluids only! Using these fluids for primary drinking may cause kidney problems. Always drink three to four glasses of water for every one glass of these specialty fluids. Make sure there is an ample supply of drinking water readily available throughout the plant or on the job site.
Other tips for employees:
- Do not use salt tablets. This causes excessive salt (sodium) to enter the system at one time. Since water always travels to the salt concentration, you will dehydrate your cells even more than they are already. Additional salt in your system can be safely maintained by using a little extra table salt at lunch.
- Eat light. This means eating cooler foods as well as avoiding heavy foods. Keep foods refrigerated, and don’t bring foods that require heating.
- Dress sensibly and protect yourself. Wear clothing that lets your body “breathe,” such as cotton. Wear a white cotton T-shirt under clothing and light-colored, lightweight fabrics on top. This does not, however, take the place of wearing the appropriate personal protective equipment for tasks performed! Since PPE may generate more heat, schedule frequent but short breaks to enable your body to cool while you replenish lost fluids. Also wear a cap with a brim, if possible. Include sunscreen to this list if you are outside full-time.
- Do not consume alcohol. A cold beer after work (hopefully not during) will continue to dehydrate cells. Beer or other alcohol does NOT replenish fluids. It actually removes more fluids from your cells.
Finally, if possible, schedule the highest level of strenuous activity during the cooler parts of the day. A little preplanning on projects can go a long way toward keeping your body functioning properly in hot, humid conditions.
Following these basic, common sense prevention techniques will help reduce the potential for a heat-related illness or injury. Teamwork is also important – encourage all employees to keep an eye on their co-workers. If you recognize that they are getting into trouble, help them out. Get them a drink, tell them to take a break, slow them down for a couple of minutes – whatever it takes.
Your quality of life on and off the job can be affected, sometimes permanently, depending on your level of heat exposure and risk. Don’t chance it. The power is within your control to prevent heat stress! Optimize that power with common sense, sensible controls and prevention.
Randy DeVaul is a 25-year safety professional and internationally published writer from Westfield, N.Y. ([email protected]). He has written three performance-based workplace safety books (www.filbertpublishing.com/safety.htm) and is a regular presenter at seminars and conferences. Comments are always welcome.