Millions of American workers are exposed to excessive temperatures on the job each year, with thousands suffering heat-related illnesses and dozens losing their lives.
Although employers are required to follow heat stress prevention guidelines created by the Occupational Safety and Health Administration (OSHA), workplace failures reportedly cost the U.S. economy upwards of $100 billion annually.
And low-income workers, who perform manual labor under adversity, lose time and wages when severe conditions sideline them. By better understanding heat stress hazards and control measures such as personal protective equipment (PPE), employers and employees can cut productivity losses and the toll it takes on working families.
How Does Heat Stress Occur?
Heat stress illnesses happen when external temperatures affect the body’s ability to effectively use its natural cooling system. When people work in high temperature settings, the body produces sweat. This moisture is designed to interact with the surrounding air and cool internal temperatures. The body also sends blood to the surface anticipating the air will cool the sweat and the nearby blood.
When high humidity and external heat impedes this cooling process, the body responds by sending even more blood to the surface. Unless external temperatures change and the sweat begins to cool the surface blood, the body begins to overheat. These are the most prevalent heat related illnesses, according to the Centers for Disease Control and Prevention (CDC).
- Heat Stroke: A leading cause of heat related deaths, it arises from insufficient blood supporting the brain and internal organs. Sufferers experience confusion, slurred speech, and loss of consciousness.
- Heat Exhaustion: Excessive loss of sweat creates physical and mental exhaustion. Symptoms include headaches, nausea, and dizziness, among others.
- Rhabdomyolysis: People who perform manual labor in intense heat over a prolonged period begin to suffer muscle tissue death. Symptoms include cramps, dark urine, and weakness.
There are also less severe conditions that present before life-threatening ailments occur. Heat cramps and rashes may be precursors to more severe illnesses or fatalities.
What Occupations Experience Highest Heat Stress Risk?
It’s not surprising that workers with salaries among the lowest 20 percent suffer heat stress illnesses and fatalities five times more frequently than the top 20 percent earners. As their physical and mental capacity declines, manual productivity drops by a reported 2.6 percent for every degree above 75.2 degrees Fahrenheit. In extreme heat above 91.4 degrees, companies see the medical costs to treat ailing employees spike by 41.6 percent. Given the empirical data, one would expect industry leaders to require PPE for heat stress in the following vulnerable industries.
- Road Construction
- Boiler and Furnace Operations
- Commercial Laundry Facilities
- Iron and Steel Mills
- Manufacturing Plants
It’s also important to consider that some people are more susceptible to heat-related illnesses. Personal risk factors include lack of physical fitness, obesity, high blood pressure, substance abuse, and medical conditions.
How Can Employers Mitigate Heat-Related Illnesses?
Employers have an opportunity to reduce heat stress risks by educating workers about the dangers of working in high temperatures, providing effective PPE for heat stress, and implementing control measures. These are ways decision-makers can reduce employee exposure to excessive heat.
- Schedule the most strenuous work during the coolest hours of the day.
- Provide ample drinking water and shade.
- Schedule frequent hydration breaks.
- Encourage workers to rest in the shade during scheduled breaks.
- Use a buddy system to monitor for signs of heat-related symptoms.
- Follow heat index reports and suspend work during critical temperatures.
- Provide power tools to replace those that require physical force.
- Discourage the use of caffeinated beverages during hot days.
- Provide heat-effective protective disposable clothing.
Reducing heat stress and other conditions is in the best interest of employers and employees alike. Lower productivity, medical expenses, and lost wages are among the monetary costs associated with heat stress and related ailments. But diminished health and loss of life make heat stress a continued tragedy. That’s why employers are tasked with following the regulations that loosely comprise OSHA heat stress standard guidelines.
What is the OSHA Heat Stress Standard?
In the absence of a specific OSHA heat stress standard, an Advance Notice of Proposed Rulemaking for Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings was issued on Oct. 27, 2021. The rulemaking process was prompted by record-breaking heat that endangered the health and wellness of millions of workers in 2021.
California Congresswoman Judy Chu also filed a heat stress prevention bill requiring OSHA to establish a federal standard to protect workers. In early 2023, neither effort produced a clear OSHA heat stress standard. However, employers are responsible for mitigating heat stress hazards and control measures based on the following federal rules.
- OSHA General Duty Clause: Under the Occupational Safety and Health Act of 1970, employers must maintain a workplace “free from recognized hazards that are causing or likely to cause death or serious harm to employees.” This general rule has been repeatedly litigated and judges typically interpret it to include heat stress prevention.
- Personal Protective Equipment (PPE) Standard: Under this regulation, employers are tasked with conducting hazard assessments and providing appropriate PPE for heat stress and other workplace hazards.
Perhaps recognizing that Congress and the federal bureaucracy move slowly, states are crafting their own heat stress regulations to ensure worker safety. California’s Heat Illness Prevention Standard requires employers to provide adequate training, water, shade, and planning. The health and safety rule gets triggered any time the outdoor temperature reaches 80 degrees.
A Minnesota standard applies to indoor temperatures, and it focuses on ensuring workers enjoy adequate ventilation and fresh air. The measure also limits the amount of time employees can be exposed to high temperatures. The Minnesota standard comes into play when employees performing heavy work experience indoor temperatures of 77 degrees, moderate labor at 80 degrees, and light duties at 86 degrees or higher.
Washington State issued an Outdoor Heat Exposure Rule that speaks directly to the use of PPE for heat stress. The health and safety guidance specifies the use and appropriate PPE and disposable protective clothing at certain temperature thresholds. General safety clothing can be worn up to 89 degrees in many settings. Heavy, double-layer coveralls, jackets, and sweatshirts are only reasonably safe up to 77 degrees. Non-breathable clothing, such as chemical-resistant suits are considered appropriate at cooler temperatures of approximately 52 degrees.
How Does PPE for Hot Environments Work?
Washington State’s Outdoor Heat Exposure Rule does not necessarily cite the Moisture Vapor Transmission Rate (MVTR) behind its PPE and personal protective disposable clothing usage guidelines. However, MVTR involves the measurement of how quickly water vapor transfers through a given material.
This is crucial when determining appropriate protective garments in hot environments. Wearing the wrong material can hinder sweat evaporation and cause unnecessary heat buildup, leading to heat stress.
For occupational protective clothing to prove effective in high temperature environments, it must allow effective sweat evaporation to occur so that workers can gain the cooling relief their body needs. That’s why breathable disposable protective clothing provides greater employee comfort while reducing the possibility of heat stress and related illnesses.
Protective clothing that allows for seamless wicking also proves more comfortable to wear. When PPE causes discomfort, employee non-compliance rates tend to increase, as do workplace injuries and illnesses. When considering PPE for working in the heat, look for product data and testing related to moisture vapor transmission rate (MVTR) to keep workers comfortable, safe, and cool.