Heat-Related Hazards & Controls
Date Posted: 02/17/2024
Workers exposed to extreme heat or working in hot environments may be at risk of heat stress. Exposure to extreme heat can result in occupational illnesses and injuries. For example, heat stress can result in heat-related illnesses such as heat stroke, heat exhaustion, heat cramps, or heat rashes. Heat can also increase the risk of traumatic injuries as it may result in poor grip, fogged-up safety glasses, and problems with balance. According to the Bureau of Labor Statistics (BLS), high temperatures can be dangerous to people at work and can lead to injuries, illnesses, and even death. Exposure to environmental heat led to 37 work-related deaths and 2,830 nonfatal occupational injuries and illnesses involving days away from work in 2020. Thirty-three of the 37 fatal work injuries caused by exposure to environmental heat occurred in the summer months of June through September.
On June 27, 2023, the Washington State Department of Labor & Industries (L&I) adopted updates to Outdoor Heat Exposure rules to prevent heat-related illness and reduce traumatic injuries associated with heat exposure. The adopted rules include requirements for shade, rest, and acclimatization and lowers the temperatures at which some preventive actions must be taken.
Washington State Action Levels
| Clothing/PPE Worn | Action Level Temperature |
|---|---|
| Nonbreathing clothing, including vapor-barrier clothing or chemical-resistant suits | 52° |
| All other clothing | 80° |
The Importance of Acclimatization
Workers are at higher risk of heat-related illness if they are not acclimatized or used to the heat. Acclimatization typically takes 7–14 days to develop and can be lost after seven days away from working in the heat. A sudden increase in temperature does not allow time for workers to acclimate.
Acclimatization is a process by which the physical processes of a worker’s body adjust to the environment over some time. Based on data obtained from the Occupational Safety and Health Administration (OSHA), this process usually takes five to seven days. However, this process could take up to three weeks, depending on the individual and their work environment. According to the American Industrial Hygiene Association (AIHA), the process requires a consistent work level for at least two hours each day during the acclimatization period for a worker to become acclimatized. Exposure to heat at one temperature does not guarantee proper acclimatization, nor does acclimatization at one temperature level confer resistance to heat at a higher temperature or more vigorous workloads. Workers who are not adequately acclimatized to the heat may experience temporary heat fatigue, resulting in a decline in performance, coordination, or alertness. This can be prevented through the gradual adjustment to the hot environment. A person’s physical condition can have an effect on a person’s ability to acclimatize.
According to the Centers for Disease Control and Prevention (CDC), acclimatization is the beneficial physiological adaptations that occur during repeated exposure to a hot environment. These physiological adaptations include:
Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
Stabilization of the circulation.
The ability to perform work with lower core temperature and heart rate.
Increased skin blood flow at a given core temperature.
To acclimatize workers, gradually increase their exposure time in hot environmental conditions over a 14-day period. New workers will need more time to acclimatize than workers who have already had some exposure. In order to quickly catch signs and symptoms of heat-related illness for those who have not been acclimatized, close observation for 14 consecutive days is required for new workers, those returning from absences of seven consecutive days, and all workers during a heat wave.
Note: A heat wave is defined as days when heat will be at or above the action levels and at least 10 degrees higher than the five-day average high.
Signs & Symptoms of Heat-Related Illness
| Heat-Related Illness | Symptoms and Signs |
|---|---|
| Heat stroke |
|
| Heat exhaustion |
|
| Heat cramps |
|
| Heat syncope |
| Heat rash |
|
| Rhabdomyolysis (muscle breakdown) |
|
Heat Stress Controls
Engineering Controls – The best way to prevent heat-related illness for indoor workers is to make the work environment cooler. Wherever possible, use air conditioning to cool the work area. Alternatively, increase the general ventilation as much as possible by opening windows or doors. When available, use cooling fans to aid in increasing ventilation.
Safe Work Practices – Employees working outdoors or indoors without air conditioning or ventilation take scheduled breaks in cool and shaded areas. Ensure plenty of cool water to drink, and take water breaks as needed. Immediately report any problems to a supervisor. Supervisors should consider scheduling the hottest work for the coolest part of the day, assigning extra workers to high-demand tasks, and using work-saving devices (e.g., power tools, hoists, or lifting aids) to reduce the body’s workload. All workers should watch out for the safety of their coworkers.
Note: Plenty of cool drinking water should be available for workers. Sufficient water must be available for each worker to drink one quart per person per hour.
Resources
F417-300-000 Permanent Changes to Outdoor Heat Exposure Rules (wa.gov)
