Heat Acclimation on Construction Jobs

Heat stress is a serious hazard on the construction job. The physical demands coupled with excessive temperatures can cause heat stress injury and heat related fatalities. Your body builds up heat when you work and sweats to get rid of extra heat. But sometimes your body may not cool off fast enough. New employees are at a higher than normal risk.

Heat Acclimation is one of the best defenses against heat stress injury and heat related fatalities. Heat Acclimation is achieved by gradually increasing exposure and physical activity in hot weather.

Heat acclimatization occurs when repeated heat exposures are sufficiently stressful to elevate body temperature and provoke perfuse sweating. Resting in the heat, with limited physical activity to that required for existence, results in only partial acclimatization. Physical exercise in the heat is required to achieve optimal heat acclimatization for that exercise intensity in a given hot environment. Workers who only perform light or brief physical work will achieve the level of heat acclimatization needed to perform that task. If they attempt a more strenuous or prolonged task, additional acclimatization and improved physical fitness will be needed.

Complete heat acclimatization requires up to 14 days with a minimum daily heat exposure of about two hours. The benefits of heat acclimatization will be retained for about 1 week and then decay with about 75 percent lost by about 3 weeks, once heat exposure ends. A day or two of intervening cool weather will not interfere with acclimatization to hot weather.

During acclimatization the systems of the body adapt to heat exposure at varying rates. During the first 5 days an improved control of cardiovascular function occurs. During the first 8 days the body goes through a body core temperature adjustment. During the acclimatization process the body chemistry changes as it learns to conserve minerals normally lost through sweat and urine. Sweating response becomes earlier and greater. Better cooling is achieved as blood flows closer to the skin. Total Benefits of Heat Acclimatization include improved thermal comfort, improved exercise performance, reduced core temperature, earlier and greater sweating, earlier skin blood flow, lower body heat production, lower heart rate, improved thirst, reduced salt loses, and improved organ protection.

Employers should be observant of new workers who may not have had much exposure to the heat and exercise. Also employees who have been moved from a cool environment may need to go through the acclimation process.

Wear light-colored clothes to see ticks more easily
Drink small amounts of water frequently
Wear light-colored, loose-fitting, breathable clothing-cotton is good
Take frequent short breaks in cool shade
Eat smaller meals before work activity
Avoid caffeine and alcohol or large amounts of sugar
Work in the shade
Find out from your health care provider if your medications and heat don't mix
Know that equipment such as respiratorsor work suits can increase heat stress

OSHA's fact sheet A list of hot weather recommendations

OSHA on Heat Stress