Characterizing Exposure of Veterans to Agent Orange and Other Herbicides Used in Vietnam: Final Report (2003)

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FINDINGS, CONCLUSIONS, AND RECOMMENDATIONS 36 ACCOMPLISHMENT • Analysis, in collaboration with IARC and the Midwest Research Institute, of tissue samples from Vietnam residents and comparison of the results with EOIs calculated for the subjects. FINDINGS, CONCLUSIONS, AND RECOMMENDATIONS Over the life of the study, the Columbia University researchers encountered unexpected sources of data and barriers to data access. The opportunities and challenges shaped the execution of their initial proposal for research. In consultation with the committee, tasks were expanded, modified, and in some cases abandoned to take advantage of some circumstances and adapt to the realities of others. However, the underlying goal of the work— creation of a herbicide-exposure assessment model for use in epidemiologic studies of Vietnam veterans— remained the same. The committee finds, on the basis of its oversight and evaluation of the work, that Jeanne Mager Stellman, principal investigator, and her research colleagues and collaborators have fulfilled the study goals set forth in the request for proposals (IOM, 1997) and have thus: • Developed and documented a detailed method for retrospectively characterizing the exposure of Vietnam veterans to the major herbicides used by the military in Vietnam—2,4-D; 2,4,5-T; cacodylic acid; and picloram—and the trace contaminants TCDD and its congeners. • Demonstrated the feasibility and appropriateness of the proposed method in sufficient detail to permit the assessment of its potential for use in the conduct of epidemiologic studies. 

FINDINGS, CONCLUSIONS, AND RECOMMENDATIONS 37 The committee therefore concludes that that the Columbia University researchers have satisfactorily completed the research project as defined in their proposal and modified in consultation with the committee. The committee also affirms all the findings and conclusions reached in its interim report released in April 2003: • The contractor has developed databases of wartime spraying and accidental dispersion of herbicides, of troop locations and movements, and of land features and soil typology. • The contractor has developed an effective exposure assessment tool to assign a metric—the E4 exposure-opportunity index (EOI)—for herbicide exposure that is based on proximity to spraying in space and time and on the amount and agent sprayed. • The range of calculated EOIs and information gathered to date on troop locations is sufficient to demonstrate the feasibility of future epidemiologic studies. Additional location data on troops not included in present databases appear to be available at the National Archives for abstraction and use by researchers and other interested parties in future studies. • Given current knowledge and available data, the contractor has adequately demonstrated that the draft model is a valid means of assessing wartime herbicide exposure of Vietnam veterans. On the basis of those findings, the committee concludes that a valid exposure-reconstruction model for wartime herbicide exposures of US veterans of Vietnam is feasible. It therefore continues to recommend that the Department of Veterans Affairs and other government agencies facilitate additional epidemiologic studies of veterans by nongovernment organizations and independent researchers.