Too Hot to Handle: Considerations for A Heat Stress Management Plan

By: Margaret C. Morrissey-Basler, Ph.D., Contributor

The extreme heat continues to show its teeth as we progress into the summer. Unfortunately, these conditions will continue to get worse as the frequency, intensity and duration of heat waves increase1. Climate change is a major public health priority that places many at risk for life-threatening heat injuries and illnesses.

Workers are particularly vulnerable to heat-related injuries, as they often engage in heavy physical exertion for prolonged hours2–5. Moreover, occupational heat stress is a combination of environmental heat, physical activity and personal protective clothing (PPE) which, taken together, exacerbates the level of heat strain placed on the body3,6.

Unfortunately, there are no federal standards to protect the health and safety of workers. OSHA has created a National Emphasis Program on Outdoor and Indoor Heat Hazards, which is a nationwide enforcement mechanism to inspect workplaces for heat-related hazards. In other words, OSHA can perform heat-related inspections on high-risk worksites to make sure workers are not susceptible to preventable heat-
related injuries, illnesses and fatalities. Therefore, it is your responsibility as an occupational and environmental health and safety professional to ensure heat safety practices are in place and workers are protected during times of high heat exposure.

So, where do you start? Here are some considerations and strategies to implement within your heat stress management plan.

Written Heat Safety Policies & Procedures

Like any hazard, it is important to have clear and written heat safety policies and procedures. During an inspection, this may be the first item OSHA personnel will ask to see. Successful heat safety policies and procedures include, but are not limited to, the following elements:

  • Heat safety education (onboarding and annual training)
  • Prevention strategies (heat acclimatization, work to rest ratios, environmental monitoring, etc.)
  • Emergency procedures for heat-related medical emergencies (i.e., exertional heat stroke)

Your plan must include what you will do to prevent heat-related injuries and illnesses from happening in the first place (i.e., prevention strategies). But it also must consider what happens when all systems fail, and someone suffers an exertional heat-related illness.

As no health and safety plan is 100% failproof, there needs to be clear guidance that outlines what workers should do in the event of a heat-related emergency. An exertional heat illness that is life-threatening is exertional heat stroke.

The signs and symptoms of exertional heat stroke include:

Signs Symptoms
Extreme Hyperthermia* (greater than 105°F) Dizziness
Altered Consciousness* Headache
Disorientation* Nausea
Confusion; Look “out of it”* Muscle Cramps
Vomiting Dehydration
Staggering Irritability/Combative
Decreased Performance Muscle Weakness
Profuse Sweating Irrational Behavior
*diagnostic criteria

Extreme hyperthermia, altered consciousness, disorientation and confusion are characterized as diagnostic criteria for exertional heat stroke7. If you suspect that someone is succumbing to exertional heat stroke, you must act quickly to reduce their core temperature as quickly as possible. This requires aggressive body cooling within 30 mins of collapse7. The gold standard method to reduce core temperature and to treat exertional heat stroke is aggressive, whole-body cold-water immersion8.

Heat Safety Prevention Strategies

To reduce the risk of exertional heat illnesses, it is key to have evidenced-based prevention strategies in place. Here are a few key prevention strategies to include in your heat stress management plan.

Hydration

Heat acclimatization is one of the most underutilized heat stress prevention strategies. Most heat-related illnesses occur within the first three days of work, when workers are not accustomed to performing the level of physical exertion, sometimes in PPE, in the heat. (photo courtesy of Adobe Stock Images)

Dehydration has been reported to increase rise in core temperature (i.e., increase risk of heat-related illness), negatively affect performance, productivity and mood9. Maintaining a hydrated state during work can improve your workers’ health and safety while preserving or improving productivity. It is important to recognize that hydration is only part of the puzzle regarding risk of heat-related illness—it is not characterized as the primary factor. Staying hydrated means paying attention to your body and using simple, hydration assessment tools to track your own hydration.

  • Urine Color

Workers should be encouraged to pay attention to their urine color before, during and after work. A pale yellow or “straw-colored” urine color would be an indicator that the worker is adequately hydration. The darker the urine, the more at risk an individual is to dehydration10.

  • Urine Output

More urine is typically produced when adequately hydrated, and less urine is produced when dehydrated. Therefore, a reduction in daily urine frequency (how often you urinate) may be an indicator of dehydration.

  • Thirst

When in a dehydrated state and body water content is low, fluid regulatory mechanisms in the body will initiate sensation of thirst as a signal to consume more fluids. It is important to note that the absence of thirst does not indicate the absence of dehydration10.

Heat Acclimatization

Heat acclimatization is one of the most underutilized heat stress prevention strategies, but it is arguably one of the most important. Most heat-related illnesses occur within the first three days of work, when workers are not accustomed to performing the level of physical exertion, sometimes in personal protective gear, in the heat11.

Heat acclimatization is the gradual and progressive exposure to your physical work environment in the heat to achieve heat adaptations that allow workers to perform better in the heat12. Although there is limited research on industry-specific heat acclimatization protocols, NIOSH recommendations increases work by 10-20% over a 5-7 day period13.

Environmental Monitoring for Activity Modification

As exertional heat illness is primarily driven by the metabolic heat generated by the individual, modifying the work-to-rest ratios is very effective to reduce risk. The industry standard for activity modification is the use of environmental monitoring, specifically Wet Bulb Globe Temperature (WBGT). WBGT uses four main meteorological components: air temperature, relative humidity, air velocity and radiant heat14. The National Institute for Occupational Safety and Health (NIOSH) and American Conference of Governmental Industrial Hygienists (ACGIH) provide WBGT-based activity modifications to protect workers during times of heat stress13,15.

Body Cooling

Body cooling can be considered an effective method of reducing thermal strain. For body cooling to be successful, there are several considerations:

  • Cover as much body surface area as possible.

Cooling rates are higher when more of the body’s surface area is cooled. This is why whole-body, cold-water immersion is an effective strategy, as the individual’s head and neck are typically the only body parts that are not submerged8,16.

  • Make sure the product is COLD and replace frequently.

This seems obvious, but the cooling capacity of a cooling product is often very limited, and the product must be “re-activated” continuously to ensure the individual will experience a cooling effect. For example, for cooling towels, they must be resubmerged into cold ice water <5 mins to allow the body to cool effectively.

  • Make sure the method you select works for your unique work environment.

Not all industries can allow certain types of body cooling during work or breaks. Your unique work environment must be considered before selecting an appropriate product or method. For example, workers with encapsulating PPE have benefited from a cooling vest. However, the cooling vest must be replaced frequently.

Margaret C. Morrissey-Basler, Ph.D., is President of the Occupational Safety & Heat Safety & Performance Coalition, Korey Stringer Institute, at the University of Connecticut.

References:

  1. Ishida H, Kobayashi S, Kanae S, et al. Global-scale projection and its sensitivity analysis of the health burden attributable to childhood undernutrition under the latest scenario framework for climate change research. Published Online First: 2014. doi:10.1088/1748-9326/9/6/064014

  2. Gubernot DM, Anderson GB, Hunting KL. Characterizing Occupational Heat-Related Mortality in the United States, 2000–2010: An Analysis Using the Census of Fatal Occupational Injuries Database. Am J Ind Med 2015;58:203–11. doi:10.1002/ajim.22381

  3. Morrissey et al.,. Heat Safety in the Workplace: Modified Delphi Consensus to Establish Strategies and Resources to Protect U.S Workers. GeoHealth 2021.

  4. Morrissey MC, Kerr ZY, Brewer GJ, et al. Analysis of Exertion-Related Injuries and Fatalities in Laborers in the United States. Int J Environ Res Public Health 2023;20:2683. doi:10.3390/ijerph20032683

  5. Spector JT, Sheffield P. Re-evaluating occupational heat stress in a changing climate. Published Online First: 2014. doi:10.1093/annhyg/meu073

  6. Bernard TE, Luecke CL, Schwartz SK, et al. WBGT Clothing Adjustments for Four Clothing Ensembles Under Three Relative Humidity Levels. J Occup Environ Hyg 2005;2:251–6. doi:10.1080/15459620590934224

  7. Casa DJ, DeMartini JK, Bergeron MF, et al. National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses. J Athl Train 2015;50:986–1000. doi:10.4085/1062-6050-50.9.07

  8. Casa DJ, McDermott BP, Lee EC, et al. Cold water immersion: the gold standard for exertional heatstroke treatment. Exerc Sport Sci Rev 2007;35:141–9. doi:10.1097/jes.0b013e3180a02bec

  9. Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr Physiol 2014;4:257–85. doi:10.1002/cphy.c130017

  10. Ln B, Y H, Dj C, et al. Practical Hydration Solutions for Sports. Nutrients 2019;11. doi:10.3390/nu11071550

  11. Tustin AW, Cannon DL, Arbury SB, et al. Risk Factors for Heat-Related Illness in U.S. Workers: An OSHA Case Series. J Occup Environ Med 2018;60:e383–9. doi:10.1097/JOM.0000000000001365

  12. Périard JD, Racinais S, Sawka MN. Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports. Scand J Med Sci Sports 2015;25 Suppl 1:20–38. doi:10.1111/sms.12408

  13. Jacklitsch B, Williams WJ, Musolin K, Coca A, Kim J-H, Turner. Criteria for a recommended standard: occupational exposure to heat and hot environments – revised criteria 2016. Published Online First: 2016. doi:10.26616/NIOSHPUB2016106

  14. Budd GM. Wet-bulb globe temperature (WBGT)–its history and its limitations. J Sci Med Sport 2008;11:20–32. doi:10.1016/j.jsams.2007.07.003

  15. ACGIH. TLVs and BEIs: threshold limit values for chemical substances and physical agents and biological exposure indices. American Conference of Governmental Industrial Hygienists 2017.

  16. McDermott BP, Casa DJ, Ganio MS, et al. Acute Whole-Body Cooling for Exercise-Induced Hyperthermia: A Systematic Review. J Athl Train 2009;44:84–93.

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