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Review of the Department of Defense Enhanced Particulate Matter Surveillance Program Report 5 Conclusions and Recommendations OVERARCHING CONCLUSIONS The Department of Defense (DOD) Enhanced Particulate Matter Surveillance Program (EPMSP) was an ambitious effort, as it was one of the first studies to measure and characterize exposures to particulate matter (PM) in an effort to assess the health effects on military personnel in the Middle East. The committee applauds the DOD’s ability to carry out such a large-scale exposure-monitoring study in the midst of a military operation, despite the inherent challenges that result from a harsh climate and a lack of personnel and resources. The results of the EPMSP provide the basis for planning future exposure monitoring efforts that can be tied to health-effects studies, and it can and should serve as a precedent for future research and surveillance. Although the ability to conduct such a study is a critical milestone, the design and conduct of the EPMSP and health-effects studies limit their usefulness.1 The EPMSP achieved data recovery of 88%, which is impressive in light of the challenges of implementing protocols and operating samplers in a Middle East war zone. In addition, the sampling design and analysis captured many of the important physical and chemical properties of PM that have been shown in previous studies to affect health outcomes. The EPMSP, however, did not clearly articulate its objectives a priori, nor did it demonstrate how the sampling design and analyses would address these objectives. The MiniVol sampler, although evaluated in the United States, has not been validated at the high PM concentrations observed in this study, for example, through collection of replicate samples. The sampling strategy, which was designed to collect only one set of filters at a time, collected insufficient particle mass and species data on a consistent basis to be useful for quality assurance (QA) and for health-effects studies. Fi- 1 The committee acknowledges that the monitoring study may not have been designed for the purpose of conducting health-effects studies, and it did not review the statement of work that DOD gave to the Desert Research Institute for conduct of the monitoring study.
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Review of the Department of Defense Enhanced Particulate Matter Surveillance Program Report 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. OVERARCHING RECOMMENDATIONS 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-
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Review of the Department of Defense Enhanced Particulate Matter Surveillance Program Report demiologic studies be undertaken in conjunction with appropriate monitoring studies so that exposure and health outcomes can be examined simultaneously. The committee recognizes the difficulty of performing sampling and health studies in an active theater. However, it also recognizes that exposure sources in this environment are more complex and potentially more toxic than in the United States and Europe, where health studies are traditionally conducted. A more complete inventory of all major sources of ambient pollutants and potential emissions in the theater should be constructed before assessment of health effects to ensure that all relevant pollutants are monitored. Such an exercise could be based mainly on an inventory of processes, substances, and materials disposed of in burn pits. Pollutants may include the criteria pollutants (fine and coarse particle mass, carbon monoxide, lead, nitrogen dioxide, ozone, and sulfur dioxide) and other hazardous air pollutants (for example, metals, selected volatile organic compounds, and PM-associated organic compounds, such as polycyclic aromatic hydrocarbons). After conducting an inventory of toxicants of concern and potential sources of those toxicants, health surveillance and epidemiologic studies that investigate the consequences of those exposures could benefit greatly from coordination with other large-scale efforts that are underway. An example is the Millennium Cohort Study, which has explored the impact of deployment on respiratory health. Given the complexities of pollutant exposures and the potential acute and chronic health effects associated with these exposures, the military should consider establishing an independent multidisciplinary advisory group composed of internal and external members to provide guidance in the development and conduct of future exposure-assessment and epidemiologic studies of military personnel in combat. The advisory group—comprising experts in statistics, analytic chemistry, exposure assessment, epidemiology, toxicology, and occupational and environmental medicine—would provide guidance on and review of study objectives, study design, protocols, and results. For example, the Ranch Hand Advisory Committee was established in 1981 by the secretary of the Department of Health and Human Services to provide oversight of the Ranch Hand Study and the Vietnam Veterans Health Study. To conduct a well-designed epidemiologic study of the potential adverse health effects of exposure to PM in deployed military personnel in the current Middle East conflict, a major effort of many units and possibly multiple military branches will be required. Such a study will be organizationally and logistically challenging, given the temporally and spatially comprehensive monitoring of PM and other pollutants and the large number of samples that would be needed. TECHNICAL RECOMMENDATIONS In designing a comprehensive monitoring scheme, a set of study objec-
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Review of the Department of Defense Enhanced Particulate Matter Surveillance Program Report tives should be developed that provides the rationale and selection of the samplers, filter media, sampling frequency, and data-quality standards to be used. Future studies should use particle samplers that operate reliably on the basis of field testing in environmental conditions that are similar to the conditions in which they are likely to be used. For the EPMSP, such field testing was not conducted, and high PM concentrations may have led to overloading of the samplers, judging by prior results from Kuwait. The frequency of sampling and the types of analyses applied to the samples should be tailored to the study objectives. Such an approach maximizes the benefits of the resources expended on the study. In future monitoring studies, it is critical that QA and control procedures be implemented and specified in writing to ensure the integrity of the samples collected and analyzed. Replicate samples should be collected at selected sites during future monitoring efforts, where feasible, to assess sampler performance. Measurement uncertainties should be reported for all PM components. That will make it possible to interpret, with caution, the concentration data on PM components whose concentrations are mostly below the detection limit of the analytic method, as in the case of the x-ray fluorescence data. Mass closure (that is, comparison of particle mass with the sum of the individual-particle components) should be performed as part of the overall QA process. Because this is likely to be a continuing effort, the military might consider developing real-time continuous particulate-matter monitoring equipment whose use is recommended in the EPMSP report. Such equipment could be based on commercially available models but adapted to withstand the theater environment, including extreme temperatures, moisture, and particle concentrations; rough handling; and minimal maintenance. The monitors should be battery-powered and should report particle-size mass concentrations. CONCLUDING REMARKS The committee recognizes the importance of this initial effort to characterize the composition of PM and to understand the potential for health effects of exposures in the active theater. The feasibility of conducting future exposure assessment and health surveillance has been demonstrated. The committee strongly endorses DOD’s effort and encourages it to continue and to expand its surveillance and research protocols to characterize health outcomes related to air-pollution exposures during military service. DOD should consider expanding medical surveillance, especially for deployed personnel, to include additional data (for example, results of pulmonary-function tests) that could be used to assess health outcomes. The information currently collected by the military in
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Review of the Department of Defense Enhanced Particulate Matter Surveillance Program Report medical databases is not designed for use in research studies to assess associations with air-pollution exposures. However, collection and use of that medical information, with an eye to developing a more robust surveillance system, could strengthen the ability to study environmental-health issues of concern. The committee also considers that, whenever feasible, efforts should be made to minimize exposures of the troops. There are a number of ways to accomplish that; for example, if there is a prevailing wind direction, emission sources (such as burn pits and incinerators) could be located downwind of bases. For periodic emissions, such as from waste-burning, burns should take place when the prevailing meteorologic conditions favor dispersion of the emissions. That would be a general approach for reducing exposures and improving health.