Health hazard evaluation report: HETA-2000-0063-2907, United States Air Force Langley Air Force Base, Hampton, Virginia.
The National Institute for Occupational Safety and Health (NIOSH) received a health hazard evaluation (HHE) request from the management of the United States Air Force Institute for Environmental, Safety, and Occupational Risk Analysis (AFIERA), Brooks Air Force Base (AFB), San Antonio, Texas. The request indicated that Air Force personnel working as aircraft fuel systems inspection and repair workers at Langley AFB, Hampton, Virginia, were exposed to heat stress, jet fuel, and jet fuel vapors in confined spaces (aircraft fuel tanks). The employees reported experiencing dizziness, lethargy, skin irritation, and a ‘jet-fuel taste' during and long after exposure to jet fuel. The requesters asked NIOSH to evaluate the heat stress aspects of the employee complaints and make recommendations to prevent heat illness among the employees. The evaluation was part of an on-going collaborative study of Air Force employees' acute exposure to jet fuel (JP-8), and the other concerns were addressed by this larger study. Data were collected June 12-16, 2000. Individual and task-specific metabolic rates were estimated, and wet bulb globe temperatures (WBGTs) were measured. Heat strain monitoring included core body temperature (CBT) and heart rate (HR) measurements on 26 participants and pre- and post-shift body weight measurements on 12 participants. The sampling results were compared to the NIOSH recommended action limits and recommended exposure limits (RALs/RELs) and the American Conference of Governmental Industrial Hygienists (ACGIH®) Threshold Limit Values (TLVs®). NIOSH and ACGIH assess heat stress using sliding scale limits based on environmental (WBGTs) and metabolic heat loads. In addition, ACGIH provides physiological heat strain limits useful for those wearing impermeable personal protective equipment (PPE) and in situations of excess heat stress. For individuals with normal cardiac performance, ACGIH recommends that sustained (over several minutes) heart rate should remain below 180 beats per minute (bpm) minus age (in years), maximum CBT should remain below 100.4 degrees F for unselected, unacclimatized personnel (101.3 degrees F for medically selected, acclimatized personnel), recovery heart rate at one minute after a peak work effort should be below 110 bpm, and there should be no symptoms of sudden and severe fatigue, nausea, dizziness, or lightheadedness. The results of the evaluation indicated that some of the participants were exposed to heat stress conditions in excess of the NIOSH and ACGIH screening criteria for acclimatized individuals. Four of twenty-six participants (15%) experienced heat strain signs (HR in excess of the ACGIH criteria). The 12 participants who were weighed pre- and post-shift were within normal range of percent body weight loss, and no one exceeded the ACGIH recommendation that body weight loss over a shift not exceed 1.5%. The evaluation results and the potential for heat strain to increase as temperatures rise during the spring and summer indicate that FSM personnel should be included in a heat stress management program. In addition, participants were not aware of having developed heat strain, indicating a need for a physiological self-monitoring program to be added to the heat stress program. During our evaluation, health hazards from environmental conditions and overwork existed for fuel cell maintenance and other workers and 4 of 26 participants developed heat strain as indicated by the physiological monitoring results (heart rate levels were in excess of occupational criteria). Of the 12 participants who were weighed pre- and post-shift, 6 developed mild dehydration, but none exceeded the ACGIH recommendation that body weight loss over a shift not exceed 1.5%. Langley AFB has heat stress instruction; however, the instruction does not include a system for monitoring personnel wearing water- or vapor-impermeable clothing ensembles. Recommendations are made to implement physiological (heat strain) monitoring and to take WBGT measurements in or around immediate work areas at least hourly during the hottest parts of the shift and the hottest months of the year.