Heat stress in the workplace.

BUMC PROCEEDINGS 2000;13:349–350 Many work environments expose workers to extremely hot and humid conditions. The most vivid example of this is the firefighter, who inevitably must tolerate heat stress as part of the risks inherent to his or her job. Whereas the worker is expected to report imminent heat exhaustion before catastrophe occurs, ultimately the employer is held liable by the Occupational Safety and Health Administration (OSHA) for providing a safe work environment for its workers. Therefore, it is incumbent upon employers to screen workers for susceptibility and to rotate workers in and out of a hot work environment so as to prevent deleterious health outcomes, even fatalities. Heat-related illness is a problem for many types of workers: metal smelters, outdoor construction and law enforcement workers, plastics manufacturing workers, landscaping and recreation maintenance personnel, staff in warehouses without air conditioning, cooks and kitchen workers, and athletes. A number of human factors contribute to a worker’s susceptibility to heat stress, such as medical conditions, increasing age, overall level of fitness, presence of other metabolically stressful illnesses, the use of certain medications, dehydration, alcohol intake, and individual ability to acclimatize to extreme temperatures. Environmental factors that can contribute to heat stress besides high ambient temperature are low convection currents, high humidity, low evaporative loss, and high insulation levels around the body. Acclimatization is defined as the time needed for physiological adaptation to extreme temperature changes. An average individual takes about 1 to 2 weeks to adapt to extreme cold or hot temperatures. Successful acclimatization occurs if the physiologic mechanisms of the cardiovascular, pulmonary, and renal systems interrelate effectively to adjust the body’s core temperature by using evaporative heat loss or conservation. The process of acclimatization requires intact and responsive cardiovascular and renal systems. The National Institute of Occupational Safety and Health has recommended that post-offer and surveillance examinations for heat stress include a complete history and physical examination to screen for relative or absolute contraindications to hot environments (1). These recommendations were made with the intent to screen workers who are more susceptible to heat stress before a catastrophic event occurs in the workplace. No specific examination exists to screen workers’ susceptibility to hot environments. However, specific questions directed at screening for risk factors for heat stress can be included in the medical history to identify susceptible individuals. These questions should highHeat stress in the workplace