By Nicole Moyen, Vice President of Research and Development at Kenzen and heat stress blogger
When it comes to planning for the prevention of heat-related injuries & illnesses among an entire workforce, a one-size plan does not fit all.
The research behind managing worker safety under hot working conditions has largely been based on studies of young, healthy men, which means that other populations – women, older adults, and people with other risk factors – will need different accommodations if a heat safety program is to be effective.
Sex, age, health status, and other factors can impact risk
According to researchers who study how heat affects workforces, “…existing guidelines adopted and recommended for use by government agencies worldwide to protect the public and workers also assumes a “one size fits all” approach to protect human health. These guidelines generally prescribe protective measures (e.g., heat advisories, exposure limits) using models defined by the assessment of heat strain in young and/or relatively healthy adults. They fail to consider key factors such as sex, age, health status, and other factors, which can markedly alter a person’s tolerance to heat, thereby leaving a large segment of the population under-protected…” (1)
For example, a man working at the same relative work rate as a woman will typically have a higher sweat rate. This is because men generally have a larger body-surface-area-to-mass ratio than women.
Given that sweating is the main way a body gets rid of body heat, this higher sweat rate among men means that their body temperature will be lower in hot-dry (low humidity) climates. As a result of this higher sweat rate & lower body temperature, men will likely be able to work for a longer period of time than women. However, in hot-humid climates where sweat can’t evaporate as easily and therefore doesn’t cool you down, women will likely be able to work for a longer period of time than men. This is because men will continue to sweat more than women, but this sweat won’t be cooling them down, and in fact, they’ll just lose a lot of body water. The effect: in hot-humid environments, men will become dehydrated more quickly than women, and see a faster increase in core body temperature – the primary trigger of heat-related injuries and illnesses.
Older workers more susceptible to heat stress
Another natural factor that can vary the susceptibility of heat-related injuries and illnesses among workers is age. After age 35, the body’s ability to dissipate heat, primarily through sweating, declines. As a result, older adults tend to have higher core body temperatures than younger adults, when working at the same rate in the heat. This difference between older and younger individuals can be minimized with heat acclimatization and endurance training.
In addition, some people are able to acclimatize faster and tolerate heat better than others; a portion of this appears to be attributable to genetic makeup.
Moreover, there are various diseases that can impair the body’s ability to effectively thermoregulate, such as various cardiovascular diseases (e.g., hypertension), sweat gland disorders (e.g., Type I and Type II diabetes), skin disorders (e.g., psoriasis), and metabolic disorders. Individuals with these diseases will be at increased risk for heat-related injuries and illnesses.
These factors (age, biological sex, and disease) affect each individual differently when working in the heat, and therefore require workforce supervisors to alter their approach in developing work/rest schedules for workers. It is important to observe changes in employees’ health while on the job site and take appropriate, individualized measures to ensure that each person remains at safe core body temperatures. Always listen to workers when they say they’re not feeling well, and allow them to take a break.
Smart PPE sensors can detect and relay warnings
Smart personal protective equipment (PPE) is available to monitor individual workers’ health during work in the heat. New sensors, worn on the body, can detect and relay warnings to both the worker and supervisor and alert when an intervention – such as stopping work, resting, and allowing the body to cool-down – should happen.
In the absence of such a system, active monitoring such as keen observation, a worker-buddy system that pairs employees with each other to do “check-ins,” and encouraging workers to be acutely aware of their body’s signals of heat injury/illness are all ways to help prevent the negative consequences of heat stress on workers.
When an employee begins to exhibit goosebumps or chills, light-headedness, nausea, and/or feels more weak or fatigued than usual, likely they are experiencing heat exhaustion. Other indicators include fainting, light-headedness, unusually hot skin, excessive sweating, potential vomiting, and difficulty working.
If the worker experiences hallucinations, behavior changes such as aggressiveness, irritability, confusion, and/or irrational tendencies, feels week, or is no longer able to work, their core body temperature may have reached greater than 104°F or 40°C. Likely, this person is experiencing exertional heatstroke. This is a medical emergency and the person needs to be immediately cooled in an ice-water bath.
Flexible work-rest schedules can make a difference
Again, given the person’s biological sex, age, genetics, and diseases, people on your workforce will react differently to working in hot and humid conditions. The main way to “customize” a heat safety program for a diverse team is to be flexible in work-rest schedules. Not all workers will need a break at pre-designated intervals. The body signals outlined above will dictate when rest is needed, where cooling (finding shade and/or air conditioning, and removing excess clothing) and hydration should be emphasized.
During the rest periods, continue to observe individual workers and check their ability to return to work every 10-15 minutes. Because each person will respond completely differently to working in the heat, only that individual can indicate when they’re ready to safely return to work.
Kenny, G.P., Notley, S.R., Flouris, A.D. and Grundstein, A., 2020. Climate Change and Heat Exposure: Impact on Health in Occupational and General Populations. In Exertional Heat Illness (pp. 225-261). Springer, Cham.
Budd, G.M., 2008. Wet-bulb globe temperature (WBGT)—its history and its limitations. Journal of Science and Medicine in Sport, 11(1), pp.20-32.
Regulation, T.R.A.D.O.C., 2016. 350-29. Prevention of heat and cold casualties. Fort Eustis, VA: US Army Training and Doctrine Command, Publication TRADOC Regulation, pp.350-29.
Coco, A., Jacklitsch, B., Williams, J., Kim, J.H., Musolin, K. and Turner, N., 2016. Criteria for a recommended standard: occupational exposure to heat and hot environments. control Ccfd, editor.
Nicole Moyen leads R&D at Kenzen, the smart PPE innovator focused on physiological monitoring and the prevention of heat injury and death among workers. Kenzen’s real-time heat monitoring system is used by companies to keep workers safe from heat. Moyen has a decade of research experience in industry and academia related to human physiology and wearable devices and advises companies on heat stress physiology and dehydration. Nicole has an M.S. in Exercise Physiology and is currently finishing her PhD in Biology from Stanford University.