What is Heat Stress?

Heat stress is an illness that can be caused by exposure to extreme heat. It occurs when the body is unable to maintain a healthy temperature in response to a hot environment. Workers who are constantly exposed to high temperatures or an otherwise hot environment may be at risk for developing heat stress, as they typically have long shifts and may be either ill-equipped or inadequately trained by their employers to recognize this illness and take preventative measures.

Hot conditions present a definite threat to workers. High temperatures can be dangerous and even fatal at work, as they lead to injuries, illnesses, and death. In 2015, exposure to environmental heat led to 2,830 nonfatal occupational injuries and illnesses, as well as 37 work-related deaths. Of these deaths, 33 of them occurred during the months of June to September.

The Occupational Safety and Health Administration (OSHA) has published a map of U.S. heat-related fatalities for outdoor workers. This map shows the locations of these fatalities, and according to OSHA, there were 109 occupational fatalities that were heat-related from 2008 to 2014 alone. As time goes on and high temperature records continue to be broken, risk of heat stress is likely going to increase and precaution will become more important than ever.

Besides being a personal hazard, hot conditions may also put workers at risk for further injuries and can endanger their coworkers. For example, heat may result in sweaty palms, burns, fogged-up safety glasses, or dizziness. Measures should be taken to prevent or handle these factors so they do not interfere with a workers’ ability to perform safely and efficiently.

How Does Heat Stress Occur? 

Heat stress is a common workplace hazard and many workers experience drastic changes as a side effect. Other than shifting climatic patterns, workers are more likely to suffer heat related illnesses due to the nature of work of certain occupations. Construction sites, fire departments, warehousing and other workplaces are susceptible to heat related illness. Multiple studies indicate that construction workers in the U.S are 13 times more likely to die from heat-related illness compared to workers in other working environments. 

Workers starting out in new working settings with warm or hot environments in all likelihood experience severe heat stress symptoms due to the lack of heat tolerance. The process of building tolerance to high temperature working conditions is called heat acclimatization. ABout 50% to 70% of occupational incidents occur in the first working days due to lack of heat acclimatization. The body’s initial reaction to experiencing hot temperature working conditions is by displaying signs of heat stress. 

Here is a list of working conditions where risk of heat stress is inevitable: 

• Heavy Physical Activity: Construction workers are potentially susceptible to heat illnesses due to heavy physical workload requiring extended periods of activity in the sun or warm temperature working conditions. (e.g outdoor, roofing, construction work.)

• Lack of heat Acclimatization: Workers starting out in high temperature working environments possess little to no tolerance for heat and undergo fatal reactions to it. 

• Lack of PPE: It is mandatory for workers to adhere to thermal clothing that aids in the heat exchange, in comparison to clothing that holds in body heat resulting in heat stress related illness. 

The Buildup of Heat: Stages of Heat Stress

Occupational heat stress can generate heat stress related symptoms which can induce fatal illnesses including death. The buildup of heat in the human body can manifest in three stages which makes it easier to take heat stress prevention measures to prevent the possibility of a heat stroke. 

Stages of Heat Stress: 

First stage of heat stress: The first stage of heat cramps. Excessive sweating causes the lack of salt and water in the body to initiate severe muscle contractions in the hands, calves and feet. Muscle cramps are an involuntary response which spontaneously stops after a period of time, however soreness may persist for 24-48 hours

Heat Exhaustion- Second stage: The initial stage follows after with heat exhaustion. With persistent strenuous physical activity with extended periods of exposure to heat and humidity will result in the increase of the body’s core temperature. Heat stress symptoms like, headache, dehydration, low-grade fever, nausea or vomiting contribute to the possibility of stroke if left untreated. 

Heat Stroke- Final stage: The final stage is heat stroke, if anyone experiencing heat stress symptoms should receive immediate medical attention. Continuous exposure to heat combined with physical exertion can stimulate the possibility of a heat stroke. 

Who’s At Risk for Heat Stress?

Specific work environments may put workers especially at risk for heat stress. These environments are either outdoors or within a confined, heated space, and they include:

Individual factors may also put workers at risk of illness from heat. These include:

There are technical methods of determining the risk of heat stress, such as determining the wet bulb globe temperature of the work environment. This measure considers radiant heat sources, air movement, and humidity on top of temperature. There are also occupational exposure limits (OELs) to consider as well. Certain operational and environmental variables can have an impact, such as:

People who work in certain states may also be particularly at risk. For example, California, Kansas, and Texas tend to have the highest rates of work-related injuries and illnesses caused by environmental heat.

Symptoms of Heat Stress

It is highly recommended that employers use personal observations as well as technical measures to ensure that workers are safe. Certain indicators of heat stress can be observed, and it’s important to use professional judgement in order to assess the situation and quickly take action. An essential aspect to heat stress prevention training is recognizing the signs of heat stress, which include:

OSHA and the National Institute for Occupational Safety and Health (NIOSH) have worked together to provide a Heat Safety Tool App that not only provides real-time information on heat index information and weather conditions, but also acts a as a guide to identify symptoms of illnesses related to the heat.

There are also different severities of heat stress. For example, the illness may lead to heat rashes, heat cramps, heat exhaustion, or heat stroke. The most serious severity is heat stroke, which is a real medical emergency and may be fatal, as in this case the body becomes completely unable to regulate its temperature. During a heat stroke, a worker’s body temperature will be 103ºF or higher, and they may be confused or lose consciousness.   

What to Do When A Worker Suffers from Heat Stress

When it has been determined that a worker is ill due to the heat, remain calm and get help immediately. If there is not a supervisor nearby or the supervisor determines it’s a serious situation, call 911. If possible, move the worker into the shade or a cooler area, remove any outer clothing, and have someone stay with them until help arrives. As soon as possible, provide cool water to the worker to drink, apply ice, and attempt to fan or mist them. If the worker is confused or unable to stay alert/conscious these are indications they may be suffering from a heat stroke. In this case, call 911 immediately and apply ice as soon as possible.

An important aspect of assessing heat illness is creating a buddy system for workers. Implementing this system brings attention to occupational risks, and ensures that action is taken as quickly as possible. Workers should be familiar with the symptoms of heat illnesses and heat stroke in particular in order to monitor the situation. Or, a responsible person may be designated to monitor conditions and protect workers. A complete heat illness prevention program will prevent injuries and fatalities.

Heat Stress Prevention: What Methods to Apply? 

Understanding the signs of heat stress can lead to the second step of establishing heat stress prevention measures to combat occupational heat stress. Here are a few heat stress management methods you can apply to minimize heat related illnesses in the workplace. 

Heat Management: 

The most effective aspect of minimizing the threat of heat related illnesses is to effectively take control of the factors contributing to heat stress. Incorporation of engineering controls such as implementing a change in workplace structure with adding heat absorbing shields or administrative controls such as putting up signs advocating to remain hydrated or changing schedules or tasks to reduce heat exposure. 

Training:

The duty of a responsible employer consists of providing ample training to the workers before authorizing work. Employees should be able to grasp the possible casualties and what a certain working environment entails. A viable heat stress program should consist of: 

1. Understanding the signs and symptoms of heat-related illnesses and to recognize them in fellow colleagues or members.
2. Recognizing safety signs indicating locations where the possibility of heat exposure is high and taking appropriate measures such as incorporating personal protective equipment
3. Abiding by heat-protective clothing and equipment to promote heat exchange caused by strenuous physical activity.
4. Emphasis on understanding the importance of acclimatization and taking effective steps to develop it.
5. Practicing standard procedures to access emergency medical services and operation of first aid.

Implementation of Acclimatization:

Tolerance to occupational heat stress can minimize the fatalities associated with heat stress. Employers should ensure that new workers are acclimatized prior to working in high temperature work environments. Listed below is a pattern to promote heat acclimatization: 

For new workers:

Day 1: Not more than 20% of overall duration of work under hot temperatures. Gradually increasing the workload by 20% on each day. 

For experienced workers: 

Day 1: Not more than 50% of the overall duration of work under hot temperatures. 

Day 2: Increase of 10% of the overall duration of work under hot temperatures. 

Day 3: Increase of 20% of the overall duration of  work under hot temperatures. 

Day 4: Enabling workers to work 100% of the duration of work under hot temperatures. 

Managers or supervisors should keep an eye on new employees for the first 14 days or until they are fully acclimatized to the working environment. Additionally, employers should invest in heat stress safety products and training to effectively combat the threat of occupational heat stress.

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Additional Heat Stress facts:

• Heat stress is the effect of heat load on a worker’s body from exposure to a combination of factors such as the environment, metabolic heat, and clothing. Heat stress causes the body to lose the ability to control heat and can lead to heat exhaustion and heat stroke. Source: https://safetyculture.com/topics/heat-stress/
• Heat stress can result in heat stroke, heat exhaustion, heat cramps, heat syncope, heat rash, or rhabdomyolysis. These conditions vary in severity and symptoms, but all require immediate medical attention. Source: https://www.cdc.gov/niosh/heat-stress/about/illnesses.html
• Workers who are exposed to extreme heat or work in hot environments may be at risk of heat stress. Exposure to extreme heat can result in occupational illnesses and injuries. Workers at risk of heat stress include outdoor workers and workers in hot environments such as firefighters, bakery workers, farmers, construction workers, miners, boiler room workers, factory workers, and others. Source: https://ehs.research.uiowa.edu/occupational/heat-stress
• Workers at greater risk of heat stress include those who are 65 years of age or older, are overweight, have heart disease or high blood pressure, or take medications that may be affected by extreme heat. Source: https://www.mayoclinic.org/diseases-conditions/heat-exhaustion/symptoms-causes/syc-20373250
• Prevention of heat stress in workers is important. Employers should provide training to workers so they understand what heat stress is, how it affects their health and safety, and how it can be prevented. Source: https://www.osha.gov/heat-exposure
• Some of the prevention measures for heat stress include: acclimatization, rest breaks, fluid intake, shade, ventilation, cooling fans, personal protective equipment, and heat stress monitoring. Source: https://safetyculture.com/topics/heat-stress/
• Heat stress is one of the most frequently cited OSHA standards, with over 4,000 violations issued in fiscal year 2020. The most common violations include failure to maintain a written program, failure to provide training, and failure to monitor the heat index. Source: https://www.cdc.gov/niosh/heat-stress/about/illnesses.html