Occupational heat stress is the heat load to which someone is exposed in the workplace, which is a function of the environment, physical exertion and clothing.
Heat stress causes increases in core body temperature and can cause dehydration if fluid lost to sweating is not replaced by drinking.
Traditional thinking is that increases in core temperature and dehydration mostly strain the cardiovascular system and can lead to impairments in cognitive function and decision making, which can decrease productivity while increasing the changes of an accident or injury.
Occurring alongside these challenges to cardiovascular and cognitive functioning are added stress on the kidneys. The job of the kidneys is to filter blood, removing waste and extra water to make urine. As a result, the kidneys play a major role in the regulation of body fluids.
Given this role of the kidneys in the body, it is perhaps not surprising that the kidneys were recently identified as an “at risk” organ system during occupational heat stress. For instance, a recent analysis published in the medical journal Lancet Planet Health indicates that about 15 percent of workers who typically or frequently worked under heat stress conditions experienced kidney disease or acute kidney injury.
Understanding heat stress
Occupational heat stress challenges the kidneys in two ways.
First, increases in core temperature and dehydration result in reductions in kidney blood flow, which are made worse when occurring alongside physical exertion. Second, dehydration makes the kidneys work harder to conserve body fluids.
Scientific evidence indicates that when decreases occur in kidney blood flow alongside making the kidneys work harder, there is an increased risk of developing mild acute kidney injury. It is believed that when mild acute kidney injury occurs on a regular basis over months or years, it can lead to chronic kidney disease, and even end stage renal disease.
There is good news, however. Scientific evidence, to date, supports that the development of subclinical kidney injury and chronic kidney disease can be easily prevented. Drinking water to help prevent dangerous increases in core temperature during heat exposure decreases the chances of the development of acute kidney injury.
Trials are currently ongoing to determine if occupational heat stress and hydration recommendations protect kidney health in workers. The effectiveness of these recommendations appears likely given new findings from occupational settings in Central America that indicate that providing shade, breaks, and encouraging drinking prevents subclinical acute kidney injury in sugarcane cutters who often work in hot environments.
Best practices
Protect yourself during occupational heat stress. Keep your kidneys healthy while working in the heat by staying hydrated through the day to limit increases in core temperature. When working in a hot environment, it is recommended that workers and their supervisors adhere to recommendations by governing bodies, such as the Occupational Safety & Health Administration. These recommendations are adjustable based on how hot the environment is and how hard laborers are required to work.
As such, these recommendations include provisions for workers taking frequent breaks in cooler, shaded environments; giving workers regular access to cool fluids; encouraging them to drink about one cup of fluid every 15 to 20 minutes; and having workers participate in heat acclimatization protocols, which can improve the capacity of the body to regulate temperature and stay hydrated.
Implementing these recommendations will largely prevent sustained increases in core temperature and dehydration and will safeguard kidney health in both the short- and long-term.
Zachary J. Schlader, Ph.D., FACSM is an associate professor in the Department of Kinesiology, School of Public Health – Bloomington at Indiana University. Nicole Moyen, is vice president of R&D at Kenzen, which focuses on on physiological monitoring and the prevention of heat injury and death among workers.