Environmental Stress Factors

Outdoor operations conducted in hot weather, such as construction, refining, asbestos removal, hazardous waste site activities, and emergency response operations, can cause or contribute to heat stress. Workers who are required to wear semi-permeable or impermeable protective clothing are at a higher risk of heat-related stress and illness. This is due to the extra weight and potential for trapped heat within the garments.

Temperature and Humidity

Temperature is not the only factor that workers and employers should take into account when preparing to work outdoors. Although high temperatures can contribute to the heat index, humidity - the measurement of moisture in the air - affects the heat index as well. Because sweating is a primary response to cooling the body, the amount of moisture in the air can inhibit the body's ability to sweat effectively. This is because the perspiration does not cool the body as well when the moisture content in the atmosphere is too saturated to evaporate the moisture that appears on the skin, thus limiting the cooling effect.

Direct Sunlight and Daytime

Another preventive measure that workers can use to protect themselves from heat-related stress is avoiding both direct sunlight and working during peak daylight times. Direct sunlight exposure can increase outdoor air temperatures by 14°F, which also increases the heat index, associated risks, and the need for special precautions.

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