July 29, 2005

Tips for coping with heat stress

The heat-related death of a man harvesting peppers in Kern County last week is a tragic reminder of the dangers of heat stress.

To help reduce dangers of becoming overheated, a University of California Cooperative Extension specialist explains how heat-related illnesses develop and how to avoid them.

UC Berkeley-based agricultural personnel management specialist Howard Rosenberg warns that excess heat can impair the body even before a person feels ill. Symptoms of heat stress may include general discomfort, loss of coordination and stamina, weakness, poor concentration, irritability, muscle pain and cramping, fatigue, blurry vision, headache, dizziness, nausea, confusion, and unconsciousness.

Although some of the heat that people have to deal with at work comes from the sun and ambient air, most heat is generated by their own bodies, Rosenberg says. “At rest the body produces little heat, but at work it demands more energy and faster metabolism, which greatly increases internal heat production,” he explains.

To cool itself, the body first increases blood flow toward the body surface. This reduces the flow available to carry oxygen and nutrients to the muscles, brain and other internal organs, which in turn impairs strength, diminishes alertness and accelerates fatigue.

“When this mechanism doesn’t release heat fast enough, sweat glands kick in,” says Rosenberg. “They draw water from the bloodstream to form sweat that carries heat across outer layers of the skin and then evaporates.” The loss of water through sweating impairs the body’s ability to cool itself later, and the loss of electrolytes in sweat can cause muscle cramps.

The longer sweating goes on, the less blood volume remains and the greater the health risk. Rosenberg gives this cautionary example: a 150-pound man working moderately in warm weather would lose about 3/4 quart of water — or 1 percent of his body weight — per hour. At that rate, without replacing the lost fluid, he would likely experience diminished energy and endurance after three hours, serious fatigue and nausea after six hours, and loss of consciousness after eight hours.

He recommends drinking water even before being prompted by thirst because thirst is a late signal of a water deficit. “Chugging to quench an intense thirst is like pouring water on a wilted plant,” Rosenberg says.

For farm operations, Rosenberg recommends that managers and foremen try to keep drinking water containers as close as possible to centers of activity. If the water is too far away, such as at the end of a long row, workers may not want to take time away from their tasks or exert the extra effort to get to it.

Rosenberg also recommends bringing “a little heat-stress physiology 101 to the field” — helping workers understand the causes of heat stress, their own bodies’ heat release mechanisms, and the critical importance of replenishing the fluid they lose as sweat. “We hope the new card enables more growers to effectively deliver information that their employees need to know.”

If workers begin experiencing heat stress symptoms, Rosenberg advises having them rest, preferably in a cooler area, and drink plenty of water or electrolyte fluids. In case of heat stroke, immediate medical attention should be sought.

AB 805, a bill pending in the California Legislature, would add specific heat-illness prevention and response requirements to employers’ existing obligations for workplace safety. This month, after more than three inactive years, a Cal/OSHA advisory committee resumed its consideration of a new industrial regulation that would help prevent heat illness and injury in the workplace.

More references about heat stress are available on the Web site: http://are.berkeley.edu/heat/.

Heat illness symptoms and first aid

Heat rash

Acute skin inflammation and clogging of sweat ducts. Regarded as the least severe of heat illnesses. Though it usually causes only temporary discomfort, it can lead to a bacterial infection that shuts down the function of sweat glands.

Advice: Cleanse the affected area thoroughly and dry completely. Calamine or other soothing lotion may relieve discomfort.

Heat syncope

Loss of consciousness, generally sudden, due to lack of sufficient blood and oxygen to the brain. Greatest danger is secondary injury from a fall. Most likely to affect people not yet acclimatized to work in hot environments. Heat stress can cause it by diverting blood to extremities or lower body at the expense of the brain.

Advice:  Rest, ventilate, and drink plenty of water or electrolyte fluids.

Heat cramps

Heavy sweating, thirst, and painful, involuntary muscle contractions — most commonly in calves, thighs, arms and abdomen. Often extremely uncomfortable and can be completely disabling. Typically occur during or after hard work and are induced by electrolyte deficiencies that result from extended periods of intense sweating.

Advice: Rest and drink plenty of water or electrolyte fluids.

Heat exhaustion

Symptoms include fatigue, headache, dizziness, muscle weakness, nausea and chills, tingling of hands or feet, confusion, loss of coordination, fainting and collapse. Occurs during work and results from dehydration, lack of acclimatization, reduction of blood in circulation, strain on circulatory system and reduced flow of blood to the brain.

Advice:  Rest in the shade or a cool place. Drink plenty of water (preferred) or electrolyte fluids.

Heat stroke

The most extreme consequence of heat stress, a medical emergency that can occur suddenly if heat exhaustion is not treated. Skin is hot and dry, body is typically hotter than 104 degrees and no longer able to cool itself, and mind is confused, delirious or convulsive. Brain damage and death may result.

Advice:  Immediately move to coolest place available, loosen clothing, fan and douse or spray the body continuously with a cool liquid, begin to replenish body fluids by drinking, and summon or rush to aid. Get medical attention or/and transport to a medical facility as soon as possible.

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