Jet Fuel Exposure among Military Personnel

Funding Source: Henry M. Jackson Foundation Award #000125796
PI: Susan Proctor, DSc, US Army Research Institute of Environmental Medicine
Co-Investigators: Michael McClean, ScD, BUSPH; Kristen Smith, DSc, Harvard School of Public Health; Ema Rodrigues, DSc, Harvard School of Public Health

ebrg_4Jet propulsion fuel 8, also known as “JP8”, is a common occupational exposure among US military personnel that affects over 2 million workers worldwide. Some of the most highly exposed Air Force personnel include fuel systems workers who performance maintenance activities inside of aircraft fuel tanks. Civilian airline personnel are also exposed to similar kerosene based jet fuels, such as Jet A and Jet A1. Exposures in occupational settings occur primarily through inhalation and dermal absorption, although there is also potential for exposure via incidental ingestion. While there is little information on the human health consequences associated with exposure to JP8, previous studies have suggested that adverse neurological health effects may result.

We have partnered the US Army Research Institute of Environmental Medicine (USARIEM, Natick, MA) to conduct a large-scale investigation to assess the potential adverse neurological health effects associated with exposure to JP8 among US Air Force personnel. As there are no standard exposure assessment techniques for JP8, we were first interested in determining which exposure measures might be most appropriate to use in this epidemiologic study. Accordingly, this study was divided into two phases: an exposure assessment phase (Tier 1) and the neuroepidemiologic study (Tier 2).

In Tier 1, conducted in the winter of 2007, 24 workers were recruited from one active US Air Force base and assigned a priori to low, moderate, and high exposure groups based on job characteristics. In addition to questionnaire information, breathing-zone air and dermal tape-strip samples were collected over three consecutive workdays and analyzed for total hydrocarbons (as a measure of total JP8 exposure) as well as components of JP8 such as benzene and naphthalene. Urine samples (analyzed for metabolites of naphthalene: 1- and 2-naphthol) and exhaled breath samples (analyzed for unmetabolized components of JP8 including n-hexane and benzene) were collected during the same days. We found that while a priori exposure groups were useful in distinguishing breathing-zone JP8 exposure levels, task-based categories were a stronger predictor of JP8 exposure and should be considered for use in epidemiologic studies to minimize the potential for exposure misclassification. A priori exposure group and breathing-zone air levels were also significant predictors of post-shift urinary and exhaled breath biomarkers. Job-related factors (e.g. wearing gloves) were found to influence post-shift naphthol levels among highly exposed workers. Finally, due to their longer half-lives, we found that urinary naphthols are likely more useful as surrogates of exposure to JP8 over a full work-shift, while exhaled breath analytes may be more useful for measuring exposure immediately following short-term exposure. Three Tier 1 manuscripts have been prepared are in various stages of submission.

In the Tier 2 phase of this study, conducted in the winter and spring of 2008, 74 workers were recruited from three active US Air Force bases and assigned a priori to low or high exposure groups based on job characteristics and task information was obtained as guided by the results from Tier 1. In addition to a larger sample size and multiple Air Force bases, this study was conducted over 6 consecutive workdays. The assessment of neurological health outcomes included a neurological screening examination, a neurobehavioral performance battery, a postural sway evaluation, and the collection of questionnaire information. Additionally, breathing-zone air samples were collected over 4 consecutive workdays and analyzed for total hydrocarbons as well as components of JP8 such as benzene and naphthalene. Urine samples (analyzed for 1- and 2-naphthol and mercapturic acid conjugates) were collected during the same days. The fifth workday included the collection of exhaled breath and dermal tape-strip samples (analyzed for the same components as in tier 1), as well as blood samples which were analyzed for genetic polymorphisms such as GSTM1 deletion and various JP8-related volatile organic compounds. Approximately seven Tier 2 manuscripts are planned or in various stages of preparation.

Publications

  • Merchant-Borna K, Rodrigues EG, Smith KW, Proctor SP, McClean MD. 2012. Characterization of Jet Fuel Inhalation Exposure among U.S. Air Force Personnel. Ann Occup Hyg. Published on-line March 20, 2012.
  • Smith KW, Proctor SP, Ozonoff A, McClean MD. 2012. Predictors of urinary biomarkers of jet fuel exposure among Air Force personnel. J Expos Sci Environ Epidemiol. 22: 35–45.
  • Proctor SP, Heaton KJ, Smith KW, Rodrigues EG, McClean MD. 2011. The occupational JP8 exposure neuroepidemiology study (OJENES). 27th International Neurotoxicology Conference. Oct 30-Nov 2. Research Triangle Park, NC.
  • Proctor SP, Heaton KJ, Smith KW, Rodrigues E, Widing D, Herrick RF, Vasterling JJ, McClean MD. 2011. The Occupational JP8 Exposure Neuroepidemiology Study (OJENES): Repeated workday exposure and central nervous system functioning among Air Force personnel. Neurotoxicology. 32: 799–808.
  • Smith KW, Proctor SP, Ozonoff A, McClean MD. 2010. Inhalation Exposure to Jet Fuel (JP8) among US Air Force Personnel. J Occup Environ Hyg. 7(10): 563-72.