Health hazard evaluation report: HETA-2000-0060-2904, United States Air Force, Dyess Air Force Base, Abilene, Texas.
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 recruits employed as aircraft fuel systems inspection and repair workers at Dyess AFB, Abilene, Texas, 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 February 29-March 2, 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 10 participants and pre- and post-shift body weight measurements on 6 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 100.4F for unselected, unacclimatized personnel (101.3F 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 none of the ten participants were exposed to heat stress conditions in excess of the NIOSH and ACGIH screening criteria for acclimatized individuals and none experienced heat strain signs (HR and/or CBT in excess of the ACGIH criteria). However, five of the six participants who were weighed pre- and post-shift were mildly dehydrated (body weight change of -1.5% or less). Body weight changes ranged from -1.4% to 0%. The evaluation results and the potential for heat strain to increase as temperatures rise during the summer indicate that fuel systems maintenance (FSM) personnel should be included in a heat stress management program. During the NIOSH evaluation, health hazards from environmental conditions and overwork did not exist for fuel cell maintenance and other workers. However, five of the six participants who were weighed pre- and post-shift developed mild dehydration, indicating they were at greater risk for developing heat-related illnesses. Dyess AFB has a heat stress instruction; however, the instruction does not include a system for physiological monitoring, and its work/rest regimen does not factor in clothing insulation values for other than mission-oriented protective posture (MOPP) tasks. There are also no guidelines for monitoring personnel wearing water- or vapor- impermeable clothing ensembles. Recommendations are made to implement physiological (heat strain) monitoring, 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, and to establish and maintain accurate records of heat-related illnesses and incidents for follow-up.
Region-6; Heart-rate; Heat; Heat-exposure; Heat-stress; Body-fluids; Body-temperature; Body-weight; Confined-spaces; Aircraft-engines; Aircrews; Military-personnel; Jet-engine-fuels; Jets; Maintenance-workers; Physiological-effects; Physiological-measurements; Exposure-levels; Exposure-limits; Temperature-effects; Hazard-Confirmed