White Paper: Dehydration and Heat Stress

Overview

Dehydration and heat stress are legitimate concerns of the working world that can cause decreases in performance and efficiency, as well as an increase in the likelihood of injury. Employers, safety managers, and employees all want to work
safely while maximizing productivity. Each person wants to prevent accidents or injury at all costs, and to do so it is critical to know the symptoms of dehydration. This white paper examines dehydration, dehydration-caused illness and injury, and the risks associated with operating while dehydrated.

Dehydration and Heat Stress Defined

Dehydration is defined as a 1% or greater loss of body mass as a result of fluid loss¹. The human body weight is made up of around 60% to 70% fluid. Dehydration occurs when the body is losing more fluids than being consumed, which causes the
body to not perform maximally. It is important to note that the sensation of thirst is not a reliable indicator of dehydration because most people do not sense thirst until they are already dehydrated. In addition, it is considered to work best during rest². 

Fluid loss from the body through normal daily activity, breathing, perspiration, urination, and defecation, is around 2.5L that needs to be replaced daily¹. Even in mild dehydration, losses of 2% body mass or more can cause a decrease in performance of up to 50%³.

The impairment of performance and productivity worsens exponentially with prolonged fluid restriction, and an increase in the level of dehydration. The signs of early dehydration are thirst, darkened and less regular urination, headache, dizziness, and slower reaction times⁴. The signs of dehydration can mimic other serious medical issues, so it is critical to talk with a healthcare provider for an appropriate diagnosis. As the time of fluid restriction lengthens, the body’s core temperature and pulse begin to elevate, causing an increased likelihood of a heat stress event.

As the intensity of the work or activity increases, so does the risk for dehydration or a heat stress event. For each 2.2 pounds of weight a person loses in an activity, the fluid loss is around 1L². Extreme activity in hot environments can cause the body to lose 2.5L per hour, which is greater than the body’s ability to absorb consumed fluids³. If the fluid loss is 5% to 6%, cognitive function declines significantly, and tingling is often felt in the limbs³. A loss of 10% to 15% can cause muscle cramps, skin crinkling, less frequent and painful urination, and even delirium³. If fluid loss becomes greater than 15%, death becomes almost imminent³.

The National Safety Council defines three levels of heat stress as heat cramps, heat exhaustion, and the more extreme as heat stroke. Heat cramps typically first appear in the abdomen or upper and lower extremities, and present as spastic muscles in these areas⁵. Heat exhaustion occurs when too much fluid is lost from the body. A person experiencing heat exhaustion can have symptoms of pale and clammy skin, elevated heart rate, fatigue, and nausea⁵. The early signs of heat stroke occur when the body stops sweating and the core temperature begins to increase, which typically causes hot skin, slowed mental capacity, and in extreme circumstances seizures or coma⁵. Heat stroke is very serious, and can often lead to lasting organ damage and even death. Dehydration and heat stress are harmful to the body as well as to the workplace.

Factors That Increase the Risk of Dehydration

There are many factors that can increase the risk of dehydration and heat stress. The body is constantly losing fluids through natural body functions to maintain homeostasis and a core body temperature. The preparation of the body, as well as the condition, both play key parts in the risk level. Other factors include age, gender, and environmental exposure. Fluids, nutrients, and body salts that are lost must be replaced to prevent dehydration². Part of this replacement is through fluids and foods that contain water, sodium, potassium, calcium, and magnesium.

Stressors on the body such as diarrhea, vomiting, fever, excessive sweating, or frequent urination can deplete these nutrients and fluids and lead to an increased risk for a heat stress incident³. Drinks that are caffeinated or carbonated can also lead to dehydration, because these lead to higher urine outputs⁶. Medications for high blood pressure often contain diuretics, which increase the volumes of urine loss from the body.

Chronic illnesses such as diabetes, kidney disease, and even common colds put workers at a predisposition to dehydration⁴. Even with minor colds or illnesses people tend to eat and drink less, which increases the chance of dehydration⁴. Older adults
are also at a higher risk of dehydration. Older adults have smaller volumes of fluid reserves, and have diminished thirst sensations, which cause a delay in the awareness of dehydration⁴.

On top of medical preconditions and physical health, there are also external factors that contribute to fluid loss. The amount of exertion, poor air flow and circulation, radiant heat from equipment, heavy personal protective clothing, extreme temperatures, and humidity all have a negative effect on the loss of fluid from the body. It is important to note that humid temperatures can cause an increase in the vulnerability for dehydration. When the temperatures are extreme and humid, the body is unable to cool the core temperature by evaporating sweat as fast as usual⁴. This, in turn, leads to a higher core temperature and further fluid loss.

Cold temperatures also put people at an increased risk for dehydration. Cold weather can cause the chemistry of the body to confuse the mind, and can lead to a decreased awareness of sweating in thick clothing, decreased sensation for thirst, and an impaired capacity to know when to replace lost fluids⁶. Also, cold temperatures cause body fluids in the outer limbs to move inward to maintain a core temperature, but in doing so causes an amplified urine flow and increased risk for heat stress or dehydration⁶.

More specifically, the human body has a temperature range called the thermal neutral zone. The thermal neutral zone is the ambient temperature range a normal adult can conserve the core body temperature of around 98.6 degrees Fahrenheit without using more energy than required for the standard basal metabolic rate . Researchers have found that the thermal neutral zone for a clothed person doing light office work is between 14.8°C-24.5°C (58.6°F-76.1°F)¹⁴. Ambient temperatures outside of the thermal neutral zone will cause a change in the internal core temperature that activates the central nervous system and hypothalamus to regulate the heat loss or production¹⁵.

The thermoregulatory response to cool the body’s core is by vasodilation of extremity blood vessels and sweating, but to heat the body’s core temperature, extremity blood vessels are constricted and muscle shivering occurs¹⁵. More people die each year from being exposed to dangerous hot and cold temperatures outside of this range than all other weather-related deaths collectively¹⁵. Knowing how the body can be affected by these risk factors helps people to be more prepared against the threats of dehydration.

Liability of Operating Industrial Equipment Dehydrated

Operating industrial equipment while dehydrated can be just as hazardous as operating while intoxicated. During a study at Loughborough University, researchers discovered that slightly dehydrated drivers had similar errors as those whose blood
alcohol concentration was above .08%⁷. According to the Department of Motor Vehicles, a blood alcohol concentration of .08% is the highest legal limit before being considered as driving under the influence or driving while impaired⁸.

Similarly to alcohol, minor dehydration has been shown to decrease concentration, cognitive function, alertness, and alter mood⁹. The study was conducted by accessing the performance of the participants on a driving simulator while properly hydrated and while mildly dehydrated. For the hydrated trial, participants were given 85 ounces of fluid the day before the trial and 16 ounces the day of⁹. The mildly dehydrated participants were only give one-fourth of this amount before the driving test⁹.

The primary author, Dr. Phillip Watson, wanted to ensure the dehydration level of the participants was minor as to create real-life conditions⁷. The conditions were intended to mimic having a hectic day, and forgetting to take breaks to rehydrate. The level the participants were dehydrated was minimal, but the research found this was still significant enough to cause double the amount of errors as the hydrated participants⁹. These errors correlated to the same mistakes made by previous participants while inebriated⁹. The errors also increased with time as well as with prolonged limitation of fluids⁹. The interpretation of the study is as such, mild dehydration can lead to an impaired ability to safely and maximally operate⁹.

The impaired ability to operate while dehydrated is not only a physical liability, but is also a financial liability. Illness, injury, and even death from dehydration and heat stress is almost always preventable. Each year businesses lose $170 billion
because of injury, illness, or death of members of the workforce¹⁰. The loss of productivity alone costs companies around $60 billion annually¹⁰. These losses impact employers, employees, and the communities not only financially, but also physically and emotionally.

Most of the stress and suffering caused from occupational injury or illness can be prevented. Each year in the United States alone, over 4,500 workers die and over 4.1 million are seriously injured because of a job-related incident¹¹. OSHA estimates that each life lost because of an occupational incident costs around $8.7 million¹¹.

According to the National Safety Council, the likelihood to die from subjection to too much heat is 1 in 16,584 persons¹². In one year alone, 244 individuals lost their lives because of dehydration and heat stress, and over 500,000 were hospitalized^5,13. On top of the direct costs recorded to companies, indirect costs are estimated to be an additional two to four times more¹¹. These indirect costs include having to retrain new employees, more missed days, and a decrease in the product or service quality¹¹.

By being aware of the liabilities associated with operating industrial equipment dehydrated, the chances of conflict because of occupational injury are reduced significantly. This helps not only to save lives, but also leads to a more fulfilling and prosperous business model.

References:
1) Shepherd A. Measuring and Managing Fluid Balance. Nursing Times. 2011; 107: 28, 12-16.
2) Hydration. Korey Stringer Institute. https://ksi.uconn.edu/prevention/hydration/#.
3) Dehydration. Rehydration Project. http://rehydrate.org/dehydration/.
4) Dehydration. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/dehydration/symptoms-causes/syc-20354086. Published February 15, 2018.
5) Heat Illness Can be Fatal; Would You Know What to Do? National Safety Council. https://www.nsc.org/home-safety/tools-resources/seasonal-safety/summer/heat
6) Winter dehydration. USU. CHAMP. HPRC. https://www.hprc-online.org/articles/winter-dehydration. Published February
28 2016.
7) Why Dehydrated Driving Is as Dangerous as Drunk Driving. Men’s Journal. https://www.mensjournal.com/health-fitness/why-dehydrated-driving-is-as-dangerous-as-drunk-driving-20150716. Published December 5, 2017
8) DUI & DWI Laws & Enforcement. DMV.ORG. https://www.dmv.org/automotive-law/dui.php
9) Watson P, Whale A, Mears SA, Reyner LA, Maughan RJ. Mild hypohydration increases the frequency of driver errors
during prolonged, monotonous driving task. Physiology & Behavior. 2015; 147:313-318
10) Safety and Health Add Value. Occupational Safety and Health Administration. 
11) Injury and Illness Prevention Programs. Occupational Safety and Health Administration. 
12) What Are the Odds of Dying From. National Safety Council. Injury Facts 2017 Edition, pages 40-43. 
13) Kim S. Preventable Hospitalizations of Dehydration: Implications of Inadequate Primary Health Care in the United
States. Annals of Epidemiology. 2007;17(9):736.
14) Kingma BR, Frijns AJ, Schellen L, Lichtenbelt WDVM. Beyond the classic thermoneutral zone. Temperature.
2014;1(2):142-149
15) Temperature, Humidity, Winds, and Human Comfort. Atmo336 - Fall 2014. atmo.arizona.edu/students/
courselinks/fall14/atmo336/lectures/sec1/comfort.html

To learn more about how Sqwincher can help protect workers against dehydration and heat stress, see their landing page on MSCDirect.com.