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*%.W 1*-W Environmental factors that contribute to heat stress include air tem- perature, radiant heat exchange, air movement and humidity. The body's response to heat stress is reflected in the degree of symp- toms. When the stress is excessive for the exposed individual, a feeling of discomfort or distress may result and a heat-related disorder may ensue. The severity of the response will depend not only on the mag- nitude of the prevailing stress, but also on the age, physical fitness, degree of acclimatization and dehydration of the worker. Heat stress is a general term used to describe one or more of the follow- ing heat-related disabilities and illnesses. Heat Cramps. Painful, intermittent spasms of the voluntary muscles following hard physical work in a hot environment. Cramps usually occur after heavy sweating and often begin at the end of a work shift. Heat Exhaustion. Profuse sweating, weakness, rapid pulse, dizziness, nausea and headache. The skin is cool and sometimes pale and clammy with sweat. Body temperature is normal or subnormal. Nau- sea, vomiting and unconsciousness may occur. Heat Stroke. Sweating is diminished or absent. The skin is hot, dry and flushed. Increased body temperature, if uncontrolled, may lead to delirium, convulsions, coma and even death. Medical attention is needed immediately. Workers will be trained on the signs and symptoms of the forms of heat stress and will be encouraged to monitor themselves and others. In addition, experience has shown that the work/rest regimen (Table 1) is appropriate for field workers performing various degrees of work while wearing Level D (no protective clothing). All values are given in °C Wet Bulb Globe Temperature (WBGT). WBGT (wet bulb globe temperature) is defined according to the follow- ing formula (outdoors with solar load) where WB, GT, and DB are the wet bulb, globe and dry bulb temperatures, respectively: WBGT = 0.7WB + 0.2GT + 0.1DB The workload classes are defined in The American Conference of Governmental Industrial Hygienists booklet, Threshold Limit Values and Biological Exposure Indices for 1991-1992. 4-3