Heat stress exposure of aerial spray pilots

Heat stress (WBGT index) in the cockpits of agricultural spray pilots, and its physiological and subjective effects, were measured for 9 pilots flying in hot weather for a large Israeli aerial spray company. There was concern that heat exposure may be one of the factors involved in a recent increase in the fatal and non-fatal crash rate among Israeli spray pilots. WBGT index calculations were based on sequential cockpit wet bulb, dry bulb, and globe temperatures read when aircraft landed. The WBGT was always above 25 degrees C and exceeded 26.7 degrees C in 70% of observations. In pilots, a daily weight loss of 0.6-1.2% of total body weight was usual, as were rectal temperature increases of 0.5 degrees C. Daily water intakes ranged from less than 100 ml to 2000 ml per workshift. Questionnaires indicated that 42 of 45 pilots said they would drink more fluids if they were provided between flights by ground crews. An unresolved problem was whether conventional threshold standards for heat exposure were set at levels that may produce insidious impairments in pilot psychomotor performance. Cockpit air cooling is suggested as a measure for preventing heat stress in hot climates. However, appropriate filter technologies would be needed to prevent pesticide exposures during flight. Engineering and other measures to prevent heat stress and dehydration should rank high as part of a comprehensive program to protect the health and performance levels of agricultural spray pilots.