Occupational heat stress

Occupational heat stress is the net load to which a worker is exposed from the combined contributions of metabolic heat, environmental factors, and clothing worn, which results in an increase in heat storage in the body. Heat stress can result in heat-related illnesses, such as heat stroke, hyperthermia, heat exhaustion, heat cramps, heat rashes, and chronic kidney disease (CKD). Although heat exhaustion is less severe, heat stroke is a medical emergency and requires emergency treatment, which if not provided, can lead to death. Heat stress causes illness but also may account for an increase in workplace accidents, and a decrease in worker productivity. Worker injuries attributable to heat include those caused by: sweaty palms, fogged-up safety glasses, and dizziness. Burns may also occur as a result of accidental contact with hot surfaces or steam. In the United States, occupational heat stress is becoming more significant as the average temperatures increase but remains overlooked. There are few studies and regulations regarding heat exposure of workers.

Risk factors Heat-related illnesses from occupational heat stress is impacted by multiple factors. Workers exposed to high temperatures, humidity, and limited air movement, especially outside workers, are vulnerable to heat illness. Physiologic factors can also impact a worker's vulnerability, specifically if their job requires physical exertion, which produces metabolic heat. Workers can also be more vulnerable to heat illness if they are dehydrated from sweating and not drinking enough water or have a low level of physical fitness. Certain medications can also make it more difficult for someone to adapt to high temperatures, such as some common antibiotics, as well as some diabetes, cardiovascular disease, and psychiatric medications. Workers who have cardiovascular diseases, respiratory illnesses, diabetes, hypertension, or obesity, or who are currently pregnant, are also at higher risk for heat illness. Additionally, wearing heavy or thick personal protective equipment and clothing can prevent workers from sweating properly, which prevents the body from effectively cooling. A recent umbrella review suggests that female and relocated workers face greater physiological strain due to occupational heat exposure. A study estimates that climate change is to blame for an additional 25 billion working hours lost annually in India from 2001 until 2020 compared to the previous 20 years. Due to their physical demands and exposure to the elements, agricultural workers have among of the highest rates of heat-related disease. According to studies, low-income workers are disproportionately affected by heat stress because they are less able to take breaks or leave hazardous work environments.

Acclimatization According to the National Institute for Occupational Safety and Health (NIOSH), acclimatization is a biological process that an individual will go through to adjust to a stimulus following continued exposure. Physiologically, acclimatization to heat will allow a worker's body to more efficiently cool itself when exposed to high temperatures. When a worker has adjusted to working in a hotter environment, they will have a lower heart rate, earlier onset of sweating, and increased blood flow to blood vessels near the skin, allowing their body to more efficiently cool itself than a worker who is not acclimatized. (see below section on acclimatization schedules for specific processes).

Examples of high risk occupations Workers in many occupations are at high risk for exposure to heat stress. Especially vulnerable are outdoor workers who have highly physical tasks to complete, such as firefighters, miners, military personnel, construction workers, landscapers, athletes, delivery persons, and agricultural workers. Additionally, many indoor jobs also require high-exertion work in very hot conditions, for example factory workers, boiler room workers, welders, and kitchen staff. In unusually hot conditions, all workers should be aware of their risk for heat illness and should ensure that they drink plenty of water and take breaks in cool places to avoid any severe impacts.

Vulnerable populations Certain populations face increased risk of occupational heat stress due to a combination of environmental exposure, occupational conditions, and socioeconomic factors. While physiological vulnerability is addressed elsewhere in this article, structural and social determinants also play a significant role in determining who is most affected.

Outdoor and physically demanding work Outdoor workers, including agricultural and construction workers, face disproportionate occupational heat stress risk due to the combination of prolonged sun exposure, physically demanding labor, and structural barriers that limit access to protective resources. The International Labour Organization (ILO) estimates that agricultural work accounts for approximately 60% of productive hours lost globally to heat stress, with construction contributing an additional 19%.

Low-wage and seasonal workers Workers in low-wage or seasonal employment may face additional risk due to limited access to protective resources such as protective clothing, shade, hydration stations, and scheduled rest breaks. In some occupational settings, piece-rate payment structures, in which workers are compensated per unit of output rather than by the hour, may discourage workers from taking breaks, increasing cumulative heat exposure during shifts.

Socioeconomic and structural factors Socioeconomic conditions can contribute to disparities in heat-related illness by affecting exposure both during and outside of working hours. Workers with lower incomes may have limited access to air-conditioned housing or transportation, increasing total heat burden across the day. In the United States, immigrant and migrant workers are disproportionately represented in outdoor, low-wage, and agricultural occupations, and may face additional barriers including geographic isolation, substandard housing, limited access to occupational safety training, and language barriers that affect comprehension of heat illness prevention information. Research indicates that the disproportionate burden of occupational heat stress is concentrated in regions with high rates of informal employment and limited social protections, including parts of West Africa, Southern Asia, and Latin America.

… excerpt ends here. Continue reading the full article.