Exhaust exposure potential from the combustion of JP-8 jet fuel in C-130 engines

Abstract

This project was requested by the Air Force Institute of Environment Safety and Health Risk Analysis to evaluate personal exposure to turbine engine exhaust. Quantifiable indicators of exhaust exposure were identified based on selected components of turboprop exhaust-soot-borne polycyclic aromatic hydrocarbons (PAH), elemental carbon particulate matter and carbon dioxide. Since there were no U.S. occupational exposure limits (OELs) for the first two components, working OELs were chosen by analogy to assess exposure potential. Airborne concentrations of soot-borne PAH were compared with a working OEL of 0.2 mg/m³, elemental carbon particulate matter with 0.05 mg/m³ and carbon dioxide with 5,000 parts per million (volumetric) all on an 8-hour time weighted average (TWA) basis. Breathing zone levels were less than 10 percent of working OELs. Estimated transient elemental carbon particulate concentrations periodically exceeded excursion limits for the working OEL (0.15 mg/m³ for 30-min excursions and 0.25 mg/m³ for 5-minute excursions). The primary health hazard associated with elemental carbon particles is that they serve as a vehicle for adsorbed PAH. Since PAH are relatively harmless compounds until metabolized by the body to their potent polar derivatives and excursion limits are "rules of thumb", bodily repair mechanisms are believed to keep pace with damaging mechanisms from short-term PAH exposures. The photoelectric aerosol sensor (PAS) is a quantitative instrument known to respond to particle-bound PAH. The PAS shows something is particle bound, but does not confirm that the photoactive species are exclusively PAH. Knowledge of the source being sampled reduces this uncertainty. The NIOSH Analytical Method 5506 for PAH did not detect any. I conclude that the PAS is useful for identifying turbine engine exhaust concentration gradients throughout the workplace. Its short averaging time permits correlation of work activities with exposure events and allows documenting process conditions in a near real-time and time history fashion. This instrument needs more developmental work before its response can be stated in terms of an OEL for turbine engine exhaust. TWA elemental carbon concentrations were highly correlated with computed averages of PAS output. Real-time carbon dioxide measurements with an electrochemical cell correlated poorly with PAS response.