nally, the use of different filter media, which were analyzed with different techniques, introduces artifacts that make it difficult to compare results, so source-apportionment and mass-balance assessments are infeasible.
Although interpretation of the epidemiologic and health-surveillance studies was encumbered by uncertainties regarding the actual exposures, the small number of study subjects, and the limited amount of exposure data, the EPMSP results clearly document that military personnel deployed in the Middle East during the current Afghanistan and Iraq conflicts are exposed to high concentrations of PM and that the particle composition varies considerably over time and space.
The committee concludes that it is indeed plausible that exposure to ambient pollution in the Middle East theater is associated with adverse health outcomes. Some of the outcomes may present themselves as acute, affecting troop readiness during service, and some as chronic, occurring years after exposure. Therefore, to investigate further the health effects of exposure to a complex mixture of pollutants, the monitoring strategy needs to be tailored to the specific goals and hypotheses that future health-surveillance and research studies are designed to address. That includes matching the monitoring period with the deployment period of the military personnel being studied. In particular, different types of exposure monitoring may be required for the study of potential persistent effects, such as asthma and chronic obstructive pulmonary disease, compared to the study of acute effects, such as day-to-day variability in respiratory or cardiac responses.
Future monitoring studies need to include other ambient pollutants that military personnel may be exposed to in the field and that may be relevant to human health, such as ozone, air toxics, and other gaseous materials. In addition, more repeated sampling with the same filter type (for example, Teflon) would provide a greater library of gravimetric and chemical-specific data and thus increase statistical power. Finally, increasing the sampling frequency will make it possible to estimate more accurate annual-average concentrations of particle mass and chemical components.
The committee developed several overarching recommendations that cut across the entire EPMSP, including sampling, analytic approaches, and health effects. The incorporation of these recommendations would strengthen the exposure-surveillance study design and the robustness of the health-outcome analyses.
In the development of future studies by the DOD, it is important that study objectives be clearly defined to ensure that the environmental-sampling strategy meets the desired study objectives. That is, the questions that are being asked should be clearly specified a priori. Therefore, it is critical that future epi-