Written by Mariana Vieira de Moura, Mining Engineer (Consulting Engineer), in the Mining & Energy Division, RESPEC Company, LLC.
Extreme temperatures can be hazardous to people working in hazardous environments and can cause heat stress, leading to injuries, illnesses, and can also to death. Several types of workers are affected by the heat when working in an environment where they are frequently exposed to the hot weather. This type of industry could endanger the individual to short-term exposure, long-term chronic heat exposure, and even humidity, causing problems with the health, safety, and productivity of workers. This variety of workers ranges among farmers, construction workers, oil and gas workers, and others like armed forces personnel, fire-fighters, and miners . The importance of the prevention of heat stress in the population increases as the effects of climate change progress each day .
The workers who are prolonged exposed to high levels of heat and humidity can have major consequences; the body reacts, and the heart rate increases, as well as the stroke volume and, therefore, the cardiac output . From 2000 to 2010, just in the United States, a total of 359 deaths were reported to the Census of Fatal Occupational Injuries, CFOI, due to exposure of the workers to environmental heat, and the average annual heat-related fatality rate was 0.22 deaths per million workers . In the last decade – from 2011 to 2019, 344 work-related deaths occurred from heat exposure to environmental heat . In 2020, CFOI reported 1,940 non-fatal injuries and illnesses related to exposure to environmental heat in the workplace .
With this data, it is possible to realize the importance of the application of resources to address heat exposure in these industries. Several mechanisms can be used by industries to avoid injuries, illnesses, and deaths related to exposure to extreme temperatures. First, the company must adopt acclimation and hydration programs, to the worker build resources in their body to adjust to higher temperatures as they normally expose themselves, and increase the water intake of the workers, respectively. Second, by implementing training programs, workers will be more prone to prevent excessive heat exposure, recognize symptoms related to heat illnesses, and take the necessary measures to avoid fatalities.
Acclimation and Hydration Programs
When people start new jobs at industries in which they are exposed to high temperatures, the body takes up to five days to adjust both physiological and psychologic to the heat. In the first day, workers should have their schedule not to be exposed more than 20% of the total workload and time exposure, in the second day, 40%, 60% in the third day, 80% in the fourth day, and, finally, 100% in the fifth day [Figure 1]. This approach will develop the capability of the workers to perform their activities in a gradual pace and decrease the risk of heat-related illnesses and hazardous behaviors, it will also increase the efficiency of sweating, which reduces the core temperature, and adjust replacing the water loss due to sweating. Experienced workers also need to be acclimated to the hot temperatures if they take days away from work for the body to adjust again. For them, acclimation occurs in three days of gradual exposure .
In order to dissipate the heat to the surrounding environment, part of this blood flow will be redirected to the peripheral circulation, which reduces the amount of oxygenated blood going to the metabolically active muscles causing the decay of individual’s work capacity. To maintain thermal homeostasis, the internal heat in the peripheral circulation is lost to the environment through sweat, which causes gradual water and electrolyte loss . Consequently, hydration programs are very important, bringing awareness about the effect of water on our body, helping workers to increase their water intake and mitigating dehydration. In order to implement the program correctly, the companies have to make sure that the employees have available at least 4 cups of water per hour for the entire shift, ensure that the water containers are clean and sanitary, and provide disposable cups or encourage each worker to bring their own bottle, in this way the cups are not shared, and the workers frequently drink water before feeling thirsty every 15 minutes .
Training Programs to Address Heat Exposure in Hazardous Industries
During training programs, workers learn how to monitor the signs that the body gives if it is suffering from the exposure of high temperature, what are the heat-related illnesses and how to prevent them. Workers are exposed to several information regarding the importance of water intake, rest, shade, and acclimation. They also learn the importance of the use of personal protective equipment (PPE), importance of self-paced work, and communication to avoid the health and safety hazards caused by heat stress.
Safety hazards regarding heat stress can be caused by the lack of care in the working environment. This carelessness can cause fatigue, loss of concentration, impaired mental capacity, and misapplication of PPE.
Heat Stress: Health and Safety Hazards
The health hazards caused by heat stress are numeral types of heat illnesses that may develop when the environmental and metabolic heat loads suppress the ability of the body to dissipate the heat . These heat-related illnesses can range from mild severity as heat rash and heat cramps, moderate severity as heat exhaustion and heat syncope, to more severe as heat stroke, rhabdomyolysis, and hyponatremia . Also, the excessive loss of body water, which consists in sweating continuously for a significant amount of time, can lead to a state of hypo dehydration or even dehydration . Dehydration combined with high core body temperatures can cause adverse behavioral effects such as physical fatigue, loss of dexterity and concentration, lethargy, and impaired judgment .
It is important to know the symptoms of heat exhaustion and heat stroke. Heat exhaustion is a heat-related illness with moderate severity which can lead to heat stroke if not treated. Heat stroke is a high severity heat-related illness that can result in death if action is not taken. Figure 2 shows the signs and the action process for each case:
Safety hazards regarding heat stress can be caused by the lack of care in the working environment. This carelessness can cause fatigue, loss of concentration, impaired mental capacity, and misapplication of PPE. Fatigue can cause many symptoms, which decrease overall safety in the workplace. Some signs of fatigue are sleepiness, moodiness, loss of appetite, irritability, lack of concentration, and depression, and it is caused by the continued exercise of an activity and a distress caused from the heat at a minor level. There are some ways to prevent fatigue as well as the other heat illnesses, such as drinking plenty of water, eating healthy, coworkers looking after each other, schedule rest breaks when exposed to heat, and more related to fatigue, the prevention tips besides these are to develop adequate sleeping habits, avoid heavy work during night shift and after lunch break, vary job task to eliminate repetition, and avoid excessive noise. Even though fatigue cannot result in other heat illnesses, it decreases the ability of making decisions, performance, and attention, and increase the tendency to misapplication of PPE, increasing the accident rate and safety hazards.
Despite all the training and programs used in the industry, several factors contribute to the reaction of the body when exposed to high environmental temperatures. Some of these factors are personal such as age, gender, fitness, obesity, history of heat illness, history of other diseases, experience and skills, knowledge, mental capacity, as well as personal behaviors, such as lifestyle, drug and alcohol use, medication use, smoking, and sleep quality. Other factors are related to the environment, including air temperature, humidity, wind speed, radiant temperature, and behavioral factors such as level of activity and clothing.
Some factors can be changed through the instructions given by the company when providing the proper training and utilizing the acclimation and hydration programs as previously discussed, as well as with employers providing shade where workers can rest and take a break. Proper communication about signs of heat stress on you or any co-workers should be encouraged, and lastly, the alert of not working alone when exposed to extreme heat. Even though not all characteristics can be changed regarding the workers, the utilization of the proper resources is very significant and saves lives.
Visit New Mexico Institute of Mining and Technology website for more information and to access the training materials provided in one of the research projects being conducted in the university by the Mining Engineering Department: https://nmt.edu/academics/mining/faculty/rog-research/training.php
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Mariana Vieira de Moura is a Brazilian mining engineer who graduated from the Federal University of Ouro Preto in 2016 and completed her master’s degree in Mining Engineering with Specialization in Geotechnical Engineering at the New Mexico Institute of Mining and Technology in 2020. During her master’s program, she worked as a research assistant focusing on Health and Safety, where she developed the research and educational training material addressing Heat Exposure for the Occupational Safety and Health Administration (OSHA), a large regulatory agency of the United States Department of Labor.
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