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Heat Injury and Illness Prevention: Past, Present and Future

On October 27, 2021, OSHA published in the Federal Register an advance notice of proposed rulemaking for heat injury and illness prevention in outdoor and indoor work settings. This followed OSHA implementing an enforcement initiative on heat-related hazards and the development of a National Emphasis Program on heat inspections in September. At the same time, the agency formed a Heat Injury and Illness Prevention Work Group of the National Advisory Committee on Occupational Safety and Health to start collecting information in preparation for the rulemaking.


Not many hazards found in the workplace share the same historical prevalence as heat stress. In fact, one could surmise that workers getting sick or injured while working in the heat dates to the beginning of human history, except maybe during the Ice Age. One might also think this problem would be figured out by now, so why is it still an issue in the workplace? Some point to climate change, that exposure to heat is more widespread than in the past and temperatures climb higher and for longer durations. Another potential reason is that exposure to environmental heat is seen as a fact of life, a hazard presented by Mother Nature herself in most cases. Many readers can recall a time when they had to work in the heat and possibly a time when the heat was too much to manage. Images of overstressed workers gathering under a tree trying to cool off are easy to conjure up. In fact, heat stress has been managed this way for a very long time – and still is in many places. Traditional controls tend to focus on the worker’s ability to manage their own health while working in high heat. This is usually supported with reminders from the employer to be careful, take breaks and drink plenty of water. Great advice, but it’s not much of a strategy, especially when considering that by the time a worker perceives the threat, it may already be too late.

Traditionally, OSHA has chosen to address the hazard through education and the General Duty Clause, which obligates all employers to provide a work environment “free from recognized hazards that are causing or are likely to cause death or serious physical harm.” There are also 28 states that have their own safety and health programs, typically referred to as “state plans.” Four of these state plans have developed regulations that specifically target heat illness and injury prevention. California began developing a regulation in 2005; Washington did so in 2008, followed by a more protective emergency standard in 2021; Minnesota did so in 2014; and Oregon was the most recent state to develop a regulation, in 2021.

Beyond these regulations, many organizations have conducted research on the topic and developed, or are working to develop, recommended standards for OSHA to adopt. Most notably, the National Institute for Occupational Safety and Health has been working on a recommended standard since 1972. There have been some revisions to their recommended standard since then, and it’s safe to say that NIOSH is eager for their research to find its way into the proposed OSHA regulation. In addition, the American Society of Safety Professionals has been working on BSR/ASSP A10.50 as part of their ANSI/ASSP A10 Construction & Demolition Standards. For some, a federal regulation is long overdue, and with the rulemaking process underway, things are definitely heating up.


According to the National Oceanic and Atmospheric Administration, in 2021 the U.S. experienced the hottest summer since 1936. American workers continue to get sick or injured due to the heat, and in fact, 2018 and 2019 saw the highest numbers of deaths from heat since 2011. Exposure to harmful environments, including heat, consistently ranks as the fifth leading cause of death in the workplace since 2016.

Why are there still such high percentages of death from a hazard that we are so familiar with? Two issues come to mind: metabolic heat load and acclimatization. Let’s start with metabolic heat load.

The human body creates heat in a variety of ways, most notably as a byproduct of muscles performing work. Our bodies are miraculous machines that can raise or lower our internal temperature in response to changes in the environment. For example, blood vessels enlarge in the skin, moving heat away from the body’s core, and sweat glands release sweat to cool the skin. Under normal conditions, a healthy person will maintain their internal temperature at a safe level. However, there are several risk factors that can adversely affect the body’s ability to do this. These include age, drug and alcohol use, hypertension, diabetes, and respiratory and cardiovascular disease. When environmental temperatures and humidity rise to dangerous levels, human bodies have more difficulty with thermoregulation, especially when personal health risk factors exist. It has long been known that a person who has experienced a previous heat-related illness is more susceptible to heat illness in the future. It is critical to assess and understand individual risk for heat illness before starting work in hot environments. Currently, it is unclear whether the proposed OSHA standard will include a requirement for employer-managed medical evaluations and/or monitoring, but an understanding of metabolic heat contributions is an important consideration in the overall heat injury and illness prevention program.

Acclimatization is a method for protecting workers and is especially important for new workers and during the first heat wave of the season. It has been well documented that the human body can adapt its physiology in response to high heat levels, but it must be a gradual process. There are limits to how fast and to what degree a person can acclimate to hot environments, and personal health risk factors can significantly affect the body’s ability to do so. It is generally accepted that minimum exposure times to high heat levels are necessary for safely triggering this physiological response. Some studies suggest a minimum of two hours of exposure time, which could be broken down into one-hour increments separated by a period of relief. Some experts recommend that standards require a formal acclimatization process with a phased-in approach for vulnerable workers. For example, a new worker would not be permitted to work in high heat environments for more than 20% of their normal workday, with a gradually increasing exposure each day until they reach 100% of their normal activity. Others argue that a standard with these types of specifications would be overly burdensome and, in some cases, infeasible. An alternative would be a performance-based standard that focuses on the result, not necessarily the means to get there. In other words, employers could make sure the result is acclimatized workers, but how that is accomplished would be left up to them. This may be a more practical approach because it allows for more flexibility with a transient workforce, during storm response, and in a market where utility contractors operate in a large geographic area.


It is unclear what OSHA’s final rule will look like at this point, but it is sure to have a broad impact on the utility construction industry. Employers that don’t have an established heat injury and illness prevention program are advised to start organizing the key elements of a program. At a minimum, the program should address basic controls to prevent heat illness and injury. Considerations include training employees about heat hazards and personal risk factors; having provisions for rest, shade and water; and establishing a method for monitoring workers. Whether OSHA will decide to develop a prescriptive, specification-based standard or a performance-based standard remains to be seen. One thing is for sure, however: Employers will have to assess their current safety and health program to ensure that they are compliant with the final rule and keep their workers safe from heat hazards.

About the Author: Mike Starner, CUSP, is the director of outside line safety for the National Electrical Contractors Association. He is an OSHA-authorized outreach trainer with 29 years of operational and safety management experience in the electric utility field, including time with investor-owned utilities and electrical contractors before joining NECA.

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