Heat illness or heat-related illness is a spectrum of disorders due to environmental exposure to heat. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke.
A number of heat illnesses exist including:
- Heat stroke – Defined by a body temperature of greater than 40 °C (104 °F) due to environmental heat exposure with lack of thermoregulation. Symptoms include dry skin, rapid, strong pulse and dizziness.
- Heat exhaustion – Can be a precursor of heatstroke; the symptoms include heavy sweating, rapid breathing and a fast, weak pulse.
- Heat syncope – Fainting or dizziness as a result of overheating.
- Heat edema
- Heat cramps – Muscle pains that happen during heavy exercise in hot weather.
- Heat rash – Skin irritation from excessive sweating.
- Heat tetany – Usually results from short periods of stress in intense heat. Symptoms may include hyperventilation, respiratory problems, numbness or tingling, or muscle spasms.
Prevention includes avoiding medications that can increase the risk of heat illness (e.g. antihypertensives, diuretics, and anticholinergics), gradual adjustment to heat, and sufficient fluids and electrolytes.
Mild disease can be treated with fluids by mouth. In more significant disease spraying with mist and using a fan is useful. For those with severe disease putting them in lukewarm water is recommended if possible with transport to a hospital.
Heat stroke is relatively common in sports and is the cause of about 2 percent of deaths. Football in the United States has the highest rates.
Between 1999 and 2003, the US had a total of 3442 deaths from heat illness. Those who work outdoors are at particular risk for heat illness, though those who work in poorly-cooled spaces indoors are also at risk. Between 1992 and 2006, 423 workers died from heat illness in the US.
Heat illness used to be blamed on a tropical fever named calenture.
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 or heat rashes. Although heat exhaustion is less severe, hyperthermia is a medical emergency and requires emergency treatment, which if not provided can even 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 United States, occupational heat stress in becoming more significant as the average temperatures increase but remains overlooked. There are few studies and regulations regarding heat exposure of workers.
Heat-related illnesses from occupational heat stress have several risk factors. Some of these factors include high temperatures, humidity, radiant heat sources, limited air movement, metabolic heat from physical exertion of energy, not drinking enough fluids, personal protective equipment and clothing, physical condition and health problems, medications, pregnancy, lack of acclimatization, advanced age, having a previous heat-related illness and others.
Workers in many occupations are at high risk for exposure to heat stress. Some of the higher risk occupations include firefighter, bakery worker, miner, military personnel, construction worker, factory worker, boiler room worker, landscaper, and agricultural worker.
Symptoms of heat stress
The main symptoms of heat stress are perspiration, increased heart rate, and dehydration. Other general symptoms include painful muscle cramps, extreme weakness, nausea, dizziness, headache, breathing fast and clammy, pale, cool, and/or moist skin or red, dry skin.
Employers can establish prevention programs, which focus on having protocols to gradually increases workloads and concede on allowing on more breaks for new hired workers. Employers can control heat stress through engineering controls, work practices, providing training, implementing an acclimatization schedule, providing water and encouraging workers to drink often, and ensuring workers take appropriate rest breaks to cool down.
International Organization for Standardization helps set standards for monitoring environments, analyzing data, and interpreting results.
Section 5(a)(1) of the Occupational Safety and Health Act of 1970 declares that “Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.”
The Mine Safety and Health Administration provides guidelines and recommendations to employers for preventing heat stress among workers. There guidelines and recommendations are not enforced regulations, but instead completely voluntary.
National Institute for Occupational Safety and Health (NIOSH) conducts research on occupational hazards such as heat stress in order to provide better intervention methods and protect workers.
Only three of the fifty states have created worker regulations regarding heat: California, Washington, and Minnesota. California Code of Regulations states that employers of high risk outdoor workers are entitled to protection against heat. The employer must provide access to water and shade, practice high heat procedures, practice emergency response procedures, and practice acclimatization methods. Washington State Legislature states that employers of high risk outdoor workers follow regulations to prevent heat stress. Minnesota Administrative Rules state that indoor ventilation and temperature are regulated to prevent heat stress.
Beginning in 1972, NIOSH published a recommended standard for hot work environments, and has periodically revised to take new scientific findings into account. The intent of the NIOSH Recommended Standard for Occupational Exposure to Heat and Hot Environments is to prevent injury, disease, death, and reduced productivity. The recommendations include workplace limits and surveillance, medical monitoring, surveillance of heat-related sentinel health events, posting of hazardous areas, protective clothing and equipment, worker information and training, control of heat stress, and record keeping.
Control of heat stress
Control of heat stress has recommended general requirements, engineering controls, work and hygienic practices, and a heat alert program.
NIOSH recommends that every employer should create and implement a written program aimed at reducing heat exposures. Engineering and work practice controls should be used to reduce exposures, and a heat alert program should be implemented.
Air temperatures should be reduced so it does not exceed skin temperatures. Radiant heat should be reduced by creating barriers around the source. Evaporative heat loss can be increased by increasing air movement around the worker.
Work and Hygienic Practices
The time workers spend in hot environments should be limited, with an increase of recovery time spent in cool environments. Use of more efficient procedures and tools is beneficial to reducing metabolic demands of the job. Heat tolerance may be increased by implementing a heat tolerance plan and increasing physical fitness. Employees should be trained to recognize and treat the early signs and symptoms of heat illnesses, and employers should provide cool water for employees.
Heat Alert Program
Heat alert programs should be developed for implementation when hotter than normal temperatures, or a heat wave occurs.
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