Heat Stress and The Workplace
Every year, according to OSHA, thousands of workers fall ill to heat exhaustion or heat-related illness, while dozens die of heat stroke. The outdoor construction industry is most susceptible to this hazard, of course, but many indoor work environments are also affected by the heat.
Operations involving high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects or strenuous physical activities all have potential for causing heat-related illness in workers. Some of these workplaces include iron and steel foundries, brick-firing and ceramic plants, glass products facilities, rubber products factories, boiler rooms, commercial kitchens, laundries, food canneries, chemical plants, mining sites, smelters, steam tunnels and more.
Excessive exposure to heat can cause a range of heat-related illnesses—from the not-so-serious, i.e., heat rash and/or cramps—to the very serious (and potentially deadly) heat exhaustion and heat stroke.
Last month, Workplace Material Handling & Safety listed the warning signs of heat-related illnesses and heat stroke, as well as OSHA’s specific guidelines for how to identify dangerous heat conditions. (See “Beat the Heat: Keeping Workers Safe from Extreme Temperatures,” WMHS, March 2018.)
Scientific Evidence & Heat Measurement
There is a great body of scientific study on the effects of heat stress on the body, and even more specifically, its effects on workers. Evidence of cognitive function/performance show, first of all, that heat stress affects cognitive performance differentially, depending on the type of cognitive task. The same study shows an apparent relationship between the effects of heat stress and deep body temperature (Hancock & Vasmatzidis, “Effects of heat stress on cognitive performance: the current state of knowledge”).
Other studies have assessed the potential impact on occupational health and work capacity for people exposed at work to increasing heat due to climate change (Kjellström, et al, “Workplace heat stress, health and productivity”). This study found that, in countries with very hot seasons, workers are already affected by working environments hotter than that with which human physiological mechanisms can cope. Therefore, to protect workers from excessive heat, a number of heat exposure indices have been developed.
One that is commonly used in occupational health is the Wet Bulb Globe Temperature (WBGT). WBGT can be used to assess “the proportion of a working hour during which a worker can sustain work and the proportion of that same working hour that (s)he needs to rest to cool the body down and maintain core body temperature below 38C [approximately 104F].” Using this proportion, a work capacity estimate can be calculated for selected heat exposure and work-intensity levels. (Kjellström, et al.)
Because occupational exposure to heat can result in injuries, disease, reduced productivity and death, the National Institute for Occupational Safety and Health (NIOSH) has evaluated the scientific data on heat stress and hot environments and has updated the “Criteria for a Recommended Standard: Occupational Exposure to Hot Environments.” This was last updated in 1986; in recent years, including during the Deepwater Horizon oil spill response of 2010, questions were raised regarding the need for revision to reflect recent research and findings. The revision includes additional information about the physiological changes that result from heat stress; updated information from relevant studies, such as those on caffeine use; evidence to redefine heat stroke and associated symptoms; and updated information on physiological monitoring and personal protective equipment and clothing that can be used to control heat stress. [Editor’s note: a complete PDF of this report can be found at: https://www.cdc.gov/niosh/docs/2016-106/pdfs/2016-106.pdf.]
OSHA has also provided extensive information on how to protect workers from heat stress. The OSHA-NIOSH Heat Safety Tool is a useful resource for planning outdoor work activities based on how hot it feels throughout the day. It features real-time heat index and hourly forecasts, specific to one’s location, as well as occupational safety and health recommendations from OSHA and NIOSH. (See sidebar “OSHA-NIOSH Heat Safety Tool.”)
Help Workers Keep Their Cool
By providing the basic environmental safeguards, planning for emergencies and training workers on how to prevent illness/injuries, most heat-related problems can be prevented.
Luckily, there are many commercial solutions available that can be used to beat the heat and keep workers cool. These can include cooling base layers that absorb the body’s moisture and channel it though the fabric—thus reducing humidity next to the skin and lowering body temperature. Cooling bandanas; body cooling vests that maintain a safe temperature level in the body’s core; battery-powered cooling jackets; and hard hats with fans—all are designed to help mitigate the effects of heat.
One simple solution is to have a targeted heat-stress first aid kit available at all times. First Aid Only produces a Heat Stress First Aid Kit made of a weather-proof plastic case that is portable and can be wall-mounted. It contains such essentials as cold packs, disposable thermometers, oral electrolyte supplements, an emergency blanket, etc.
Some cooling machines are engineered to cool outdoor environments. For example, the Power Breezer, by Breezer Mobile Cooling, is an effective solution for cooling outdoor and partially covered spaces. It can quietly cool over 3,000 sq ft by up to 27°F, according to the company.
There are many commercial companies that make such coolers. They can be used in large warehouses; to relieve personnel from heat when working or training outdoors; or as a low-cost solution to augment electronic control units (ECUs) with cool air.
Additionally, portable air conditioners not only cool the air, but they also dehumidify it. This can be a crucial factor in calculating heat index and assessing the danger of heat-related stress, as humidity adds greatly to the body’s ability to have the sweat it produces evaporate on the skin. Moreover, a portable evaporative cooler can effectively cool areas and equipment where air conditioning is cost-prohibitive, impractical or unavailable. WMHS
The OSHA-NIOSH Heat Safety Tool features:
- A visual indicator of the current heat index and associated risk levels specific to your current geographical location
- Precautionary recommendations specific to heat index-associated risk levels
- An interactive, hourly forecast of heat index values, risk level, and recommendations for planning outdoor work activities in advance
- Editable location, temperature, and humidity controls for calculation of variable conditions
- Signs and symptoms and first aid information for heat-related illnesses
- A useful resource for planning outdoor work activities based on how hot it feels throughout the day
For more information on this tool or how to download the app onto most smartphones/devices, go to: https://www.cdc.gov/niosh/topics/heatstress/heatapp.html
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