Reducing Heat Stress at Work Is a Matter of Life or Death

Lawrence Buirse

Summertime temperatures are reaching and exceeding climate records worldwide.1 Heat stress is not just a public health issue; it’s also a serious workplace health and safety problem. Overexposure to hot temperatures at work can lead to serious health problems and even death.In fact, a majority of outdoor fatalities, from 50% to 70%, occur within the initial days of working in warm or hot environments.Whether employees work outdoors in direct sunlight or inside warehouses with limited heating/cooling controls, employers must take the initiative to protect their workforces from the dangers of heat stress and related illnesses.

Heat-related illness signs and symptoms

Part of mitigating the risks associated with extreme heat is knowing the signs and symptoms of heat-related conditions. Heat-related illness typically occurs when the body loses its ability to cool due to prolonged or intense exposure to hot temperatures. This sends blood rushing to the skin surface and away from the brain and other organs, which can lead to their damage if not medically addressed. If the proper medical steps are not taken, an employee may experience the most serious consequences of heat-related illness: heatstroke, permanent disability, or death.2 And while obviously less severe than the loss of life, heat stress can also cause a loss of motor skills, mental confusion, and lethargy.

Heat-related illnesses include heat rash, heat syncope, heat cramps, heat exhaustion, and heatstroke. The most common is heat exhaustion. The affected individual may experience extreme sweating, headache, weakness, nausea, and mood changes. Heat exhaustion calls for rest, water, and shade, and it must be addressed quickly. If not, Heat exhaustion can lead to heatstroke, which is life-threatening if not treated emergently.4 Signs of heatstroke may include:

  • High body temperature
  • Red, hot, dry, or sweaty skin
  • Confusion
  • Irrational behavior

Heat cramps can be brought on by inadequate water and salt intake. Resting in a cool place and massaging the cramped area can help, along with drinking more water with electrolytes. Additional signs include convulsions and fainting. It is vital to call 9-1-1 immediately for emergency medical attention and begin immediate cooling measures if heatstroke is suspected.4

Heat illness can also result in dehydration, a breakdown of the muscle called rhabdomyolysis, and even kidney disease.4 Through training, supervisors and employees can learn to identify the symptoms of heat illness and their warning signs early. Regular reminders about the signs and symptoms of heat-related illnesses and their severity can help employees take the proper precautions to avoid heat’s adverse effects.

Risk factors for heat-related illness

According to Ronda McCarthy, MD, MPH, FACOEM, national medical director of Medical Surveillance Services, and Regulatory, Testing, and Examination Medical Expert Panel (MEP) chair for Concentra®, some employees could be more susceptible to heat illness. This could include employees who are not accustomed to working in hot conditions, employees who must wear personal protective equipment (PPE) that limits heat transfer, or employees with personal health risk factors, such as:

  • Obesity (body mass index over 30)
  • History of prior heat-related illness
  • Poor physical fitness
  • Certain medical conditions (e.g., heart disease, diabetes, asthma)
  • Use of certain medications (e.g., blood pressure prescriptions, diuretics, antidepressants)

McCarthy recommends that employees who are at higher risk consult their primary care physician or an occupational health clinician to discuss both their risk and strategies for avoiding them. They should share details about work duties, work intensity, length of time spent working in hot temperatures, and any special concerns or circumstances.

Heat stress monitoring

In addition to monitoring employees for signs of a heat-related illness, employers should also monitor the heat index. The Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) have developed a heat safety tool app that can determine when heat-related illness is a possibility based on an hourly heat index. It can also provide precautions and first-aid measures. And the National Weather Service offers the following recommendations that employers can use to mitigate heat exposure5:

  • Between 80 and 90 degrees Fahrenheit: While the risk of heat illness is lower, employers should take caution and prepare by providing drinking water, making medical services easily accessible, planning training efforts, and acclimatizing employees to the heat. As the heat index goes up, so does the risk of heat-related illness, and prevention measures should intensify.
  • Between 91 and 103 degrees Fahrenheit: It’ time to issue a “heat outlook,” as the potential for heat illness exists. Employers should alert employees of high-risk conditions, conduct training, schedule rest breaks in shaded areas, and encourage employees to drink water regularly.
  • Between 103 and 124 degrees Fahrenheit: It’s time to issue a “heat advisory,” as the risk of heat illness is high. Alert employees and limit physical exertion. Start work earlier or split work shifts. Personnel trained in heat stress should be available on site to help monitor employees. Make sure to establish and enforce regular rest periods and establish a buddy system so each employee can partner with a coworker to help monitor the signs and symptoms of heat illness.
  • Above 126 degrees Fahrenheit: The risk of heat illness is critical. Do not conduct work that requires protective clothing. Work evening/night shifts. Reschedule nonessential activities and move essential work tasks to the coolest parts of the day. Engineering controls, such as decreasing air temperature with cooling booths or air-conditioned break rooms, should also be implemented. If possible, add fans and exhausts to help increase ventilation or decrease humidity, and provide shade in outdoor environments. If these protective measures are not possible, stop work to avoid heat-related illness.

Heat stress prevention and surveillance

Because of the preventable nature of heat-related illnesses, employers should establish and implement preventive measures around heat stress. There are occupational health solutions available to help employers mitigate the risks.

“Useful resources are available to develop a heat stress prevention program, including the relevant portion of the OSHA technical manual and the criteria developed by the National Institute of Occupational Safety and Health for a standard on occupational exposure to heat and hot environments,” said McCarthy.6,7

The costs of not having a plan — from OSHA citations and productivity losses to serious illnesses and work-related deaths — can be significant, affecting far more than a company’s bottom line.

Concentra has a heat-related illness prevention info sheet with action steps for employers and self-monitoring instructions for employees. Concentra’s Medical Surveillance services help employers proactively address risks associated with working in extreme heat. Contact Concentra for assistance with your company’s heat stress prevention plan.


  1. A List of U.S., Europe, Global Heat Records Smashed This Summer. (2023, July 25). Weather Underground.
  2. Frequently Asked Questions About Extreme Heat. Centers for Disease Control and Prevention.
  3. Overview: Working in Outdoor and Indoor Heat Environments. Occupational Safety and Health Administration.
  4. Heat Stress-related Illness. National Institute for Occupational Safety and Health. Centers for Disease Control and Prevention.
  5. NOAA's National Weather Service. (2019, December 15). What is the heat index? Heat Forecast Tools.
  6. OSHA Technical Manual, Section 3, Chapter 4: Heat Stress. Occupational Safety and Health Administration.
  7. Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments, The National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. February 2016.