Risks of Exposure

There’s nothing quite like the pungent smell ofjet-propulsion fuel in an Air Force hangar to get an environmental-healthresearcher’s adrenaline pumping.

"Walking in the hangar — wow, it’s really strong. Yourealize how volatile it is," says Kristen Weida Smith (SPH’06), a doctoral student anda research analyst in the School of Public Health environmental health department. She is working on a researchproject that has taken her to an Air Force base in the Midwestto collect data on jet-propulsion fuel exposure. "Over one million people inthe U.S. areoccupationally exposed to this every year," she says, "but there’s not a whole lot ofresearch on it."

Yet, that is.

Smith is part of a research team led by the U.S.Army Research Institute of Environmental Medicine (USARIEM) that is wrappingup a study on exposure to jet-propulsion fuel and neurological health inmilitary personnel. The study, led by Susan P. Proctor (SPH’92) of USARIEM, who is alsoan SPH research associate professor of environmental health, is looking atneurological health outcomes of personnel working both directly and indirectlywith jet-propulsion fuel JP-8, the primary fuel currently used by the U.S.military.

Michael McClean, an SPH assistant professor of environmental health, is a co-investigator on the study and Smith’s advisor. He designed andoversees the exposure-assessment piece of the project.

In October, Smith won an award from the InternationalSociety of Exposure Analysis (ISEA) for a student poster about the study. Theaward, given at the joint ISEA/International Society for EnvironmentalEpidemiology conference, recognizes outstanding research conducted by a studentin the area of human exposure science. Smith gave anoral presentation on the study at the conference.

Smith began working on the project for her dissertationtwo years ago. She had done previous research for Proctor on a study looking atthe effects of military deployments on neuropsychological functioning.

She says the JP-8 research has been a good fit for her,given her interest in exposure assessment and environmental epidemiology, and that it’s been a bonus to work for Proctor, who was the first doctoral graduatefrom SPH’s environmental health program.

The jet-fuel study is designed to examine whether repeateddaily exposure to JP-8, a newer fuel blend, is associated with adverse healtheffects, such as nervous system impairment. In 2003, a report by the Committeeon Toxicology of the National Research Council found that JP-8 was"potentially toxic" to the immune system, respiratory tract, andnervous system at high exposures — higher than the Air Force’s permissibleoccupational exposure limits. The committee recommended further studies on thehealth effects of inhalation and dermal exposure to JP-8.

Smith was involved in collecting and analyzing data onexposure — a process that entailed outfitting military personnel with personalair pumps and adhesive strips on the skin. Personnel were divided into threegroups, based on the likelihood of JP-8 exposure in their jobs: a high-exposuregroup (fuel-systems maintenance workers, some who work inside fuel tanks); a moderate-exposure group (refuelingmaintenance and fuel handling jobs); and a low-exposure group (office workers).

The research, which attempts to measure exposure tohydrocarbons, benzene, naphthalene, and other components of JP-8, also involvesurine and breath analysis. Smith will spend the next few months analyzing dataon those biomarkers.

Preliminary findings show personal air-exposure levelsincreased across the low- to high-exposure groups, with interior fuel-tankexposure levels much higher than levels in the hangar. Personnel who are mostexposed to JP-8 vapors wear respirators and other protective gear to limittheir personal exposure. One goal of the research is to identify key risk andprotective factors for exposure to JP-8.

Smith and Proctor say the next step in the research is toanalyze neurological health outcomes for personnel exposed to the fuel overconsecutive workdays while performing their job tasks.

McClean says the research is important because little isknown about the extent to which JP-8 exposure may affect neurological health. "We are particularly interested to see whether biomarkers ofexposure, which provide useful measures of total absorbed dose, are associatedwith performance on neuropsychological tests among these workers," he says.

Smithhas been "a great contributor to this project and is very integral to allaspects of the project efforts," says Proctor. She and the research team have traveled to several AirForce bases to collect data for the study, which was initiated about two yearsago.

"Currently, we are in the midst of the data-analysisphase," she says, "and anticipate having results to share regarding relationships betweenexposure and health effects later next year."