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Characterizing Exposure of Veterans to Agent Orange and Other Herbicides Used in Vietnam Interim Findings and Recommendations INTRODUCTION AND BACKGROUND From 1962 to 1971, US military forces sprayed more than 19 million gallons of herbicides over Vietnam to strip the thick jungle canopy that helped conceal opposition forces, to destroy crops that enemy forces might depend on, and to clear tall grass and bushes from around the perimeters of US base camps and outlying fire-support bases. Most large-scale spray- ing operations were conducted from airplanes and helicopters, but herbi- cides were also sprayed from boats and ground vehicles, and by soldiers wearing back-mounted equipment. After a scientific report concluded that a contaminant of one of the primary chemicals used in the herbicide called Agent Orange could cause birth defects in laboratory animals, US forces suspended use of the herbicide; they subsequently halted all herbi- cide spraying in Vietnam in 1971. In response to concerns about the possible health consequences of wartime exposure to herbicides, Congress passed Public Law 102-4, the Agent Orange Act of 1991.~ The legislation directed the Secretary of Veterans Affairs to request that the National Academy of Sciences con- duct a comprehensive review and evaluation of available scientific and medical information regarding the health effects of exposure to Agent Orange, other herbicides used in Vietnam, and their components, in- Codified as 38 USC1116. 1

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2 EXPOSURE OF VETERANS TO AGENT ORANGE AND OTHER HERBICIDES eluding the contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin, informally known as TCDD or dioxin. A committee convened by the Institute of Medicine (IOM) of the National Academies conducted the review and in 1994 published a comprehensive report titled Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam (IOM, 1994~. The committee responsible for the 1994 report encountered a severe lack of information about the exposures of individual Vietnam veterans to herbicides and found that this lack of information had hampered previ- ous attempts to study the effects of exposure to herbicides on the health of Vietnam veterans. That committee felt, however, that it might be possible to develop better methods of determining exposures of individual veter- ans by drawing on historical reconstructions. The methods might take into account such factors as troop movements, ground and perimeter spraying, herbicide shipments to various military bases, the terrain and foliage typical of the locations sprayed, the military missions of the troops located there, and biochemical techniques for detecting low concentra- tions of dioxin in the blood. If better models of exposure could be devel- oped and validated, the committee believed, a number of important epi- demiologic studies of exposure to herbicides and health outcomes might become possible. As part of the 1994 report, recommendations were offered concerning the need for additional scientific studies to resolve areas of continuing scientific uncertainty. Three of these recommendations addressed expo- sure assessment studies of Vietnam veterans (IOM, 1994~: A nongovernmental organization with appropriate experience in historical exposure reconstruction should be commissioned to develop and test models of herbicide exposure for use in studies of Vietnam veterans. The exposure reconstruction models developed according to [the previous recommendation] should be evaluated by an independent, non- governmental scientific panel established for this purpose. If the scientific panel proposed [above] determines that a valid exposure reconstruction model is feasible, the Department of Veterans Affairs and other government agencies should facilitate additional epide- miologic studies of veterans. In response to that report, the Department of Veterans Affairs (VA) asked IOM to establish a committee to oversee the development and evaluation of models of herbicide exposure for use in studies of Vietnam veterans. That committee would develop and disseminate a request for proposals (REP) consistent with the recommendations; evaluate the pro- posals received in response to the REP and select one or more academic or

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INTERIM FINDINGS AND RECOMMENDATIONS 3 other nongovernmental research groups to develop the exposure recon- struction model; provide scientific and administrative oversight of the work of the researchers; and evaluate the models developed by the re- searchers in a report to VA, which would be published for a broader audience. The Committee on the Assessment of Wartime Exposure to Herbi- cides in Vietnam was formed in 1996 to accomplish those tasks. Its initial work resulted in the report Scientific Considerations Regarding a Request for Proposals for Research Characterizing Exposure of Veterans to Agent Orange and Other Herbicides Used in Vietnam (IOM, 1997~. The report which com- prised a statement of work, criteria for selecting researchers, and an ap- pendix providing background information for potential respondents- was released to the public on March 18, 1997. It summarized the RFP's intent as follows (IOM, 1997, p. 3~: 1. Develop and document a detailed methodology for retrospective- ly characterizing the exposure of Vietnam veterans to the major herbi- cides 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. The proposal should address how exposure to this array of chemicals will be evaluated. However, the ability to separately identify or quantify expo- sures to each of these substances is not necessarily a requirement for a successful proposal. The exposure methodology proposed must be ap- plicable to specific types of epidemiological investigations that could be conducted at a future date under a separate contract or subcontract. 2. Demonstrate the feasibility and appropriateness of the proposed methodology in sufficient detail to permit the assessment of its potential for use in the conduct of epidemiological studies. A formal, complete RFP, including the scientific input and contrac- tual requirements, was developed and was issued on tune 30, 1997. It was initially sent to individuals and organizations that had requested it or were thought to have an interest in exposure characterization research. Availability of the RFP was publicized on the Web sites of IOM's Board on Health Promotion and Disease Prevention and the Society for Risk Analysis and was posted to relevant e-mail lists. Members of the veteran community and other interested persons were also informed of the RFP through public events held by IOM committees involved in Vietnam vet- eran health research and through contacts made at meetings and confer- ences attended by committee members and staff. Three proposals were submitted by the due date of September 4, 1997. Committee members evaluated the technical and scientific merit of these proposals on the basis of the criteria set forth in the RFP. They concluded unanimously that a proposal submitted by researchers at Co- lumbia University's Mailman School of Public Health Jeanne Mager

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4 EXPOSURE OF VETERANS TO AGENT ORANGE AND OTHER HERBICIDES Stellman, PhD, Principal Investigator) merited funding. That conclusion was transmitted to VA on February 24, 1998, and the National Academies initiated a contract with the researchers using funds provided by VA. The REP specified that the researchers were to submit scientific progress reports every 6 months over the length of the contract. The progress reports were to include: "a description of the overall progress; descriptions of the specific work accomplished, including problems en- countered and corrective actions; pertinent data or other information in sufficient detail to explain significant results achieved and any prelimi- nary conclusions resulting from analysis and scientific evaluation of data accumulated to date; and a description of the work to be accomplished over the following six months" (page 10~. Progress reports were pre- sented in public meetings of the committee to disseminate the informa- tion to a larger audience and facilitate interaction between the committee and the researchers. The first of these took place in a November 6, 1998, meeting of the committee. Communication was maintained between meetings on a less formal basis. Discussion between the researchers and the committee played an im- portant role in the project. In addition to being an essential component of the committee's oversight of the contractor's work, it allowed for the work plan to be more easily refined as the project progressed and for the researchers to obtain opinions on alternative means for addressing the challenges and opportunities that presented themselves. As of January 2003, nine 6-month reviews had been completed. A1- though the Columbia University effort (as specified in the response to the REP and modified in consultation with the committee) has not yet been completed, the committee believes that sufficient progress has been made to permit some judgments to be stated. On the basis of the committee's review of the contractor's 6-month update reports, presentations through month 54, and published and draft papers prepared by the contractor, the committee has reached the follow- . .. .. ng imclmgs: 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 epide- miologic studies. Additional location data for troops not currently in-