erans and Agent Orange: Update 1996 (IOM, 1996) and Update 1998 (IOM, 1999). In 1999, in response to a request from DVA, IOM called together a committee to conduct an interim review of the scientific evidence regarding one of the conditions addressed in the Veterans and Agent Orange series of reports: Type 2 diabetes. The committee, which consisted of individuals responsible for the Update 1998 report plus recognized experts in the field of Type 2 diabetes, focused on information published since the deliberations of the Update 1998 committee. This effort resulted in the report Veterans and Agent Orange: Herbicide/Dioxin Exposure and Type 2 Diabetes (hereafter, Type 2 Diabetes) (IOM, 2000). Although limited to one health outcome, this report otherwise adhered to the format of the VAO series.

In conducting their work, the committees responsible for these reports operated independently of the DVA and other government agencies. They were not asked to and did not make judgments regarding specific cases in which individual Vietnam veterans have claimed injury from herbicide exposure; this was not part of the congressional charge. Rather, the studies provide scientific information for the Secretary of Veterans Affairs to consider as the DVA exercises its responsibilities to Vietnam veterans.

To fulfill their charge of judging whether each of a set of human health effects is associated with exposure to herbicides or dioxin, the committees concentrated on reviewing and interpreting human epidemiologic studies, as well as experimental investigations that may contribute to biologic plausibility. The committees began their evaluation presuming neither the presence nor the absence of association. They sought to characterize and weigh the strengths and limitations of the available evidence. These judgments have both quantitative and qualitative aspects. They reflect the nature of the exposures, health outcomes, and populations exposed; the characteristics of the evidence examined; and the approach taken to evaluate this evidence. To facilitate independent assessment of the committee’s conclusions, Chapter 5 of VAO describes as explicitly as possible the methodological considerations that guided the original committee’s review and its process of evaluation. This methodology was subsequently adopted by successor committees. It is briefly summarized in Chapter 4 of this report.

To obtain additional information pertinent to the evaluation of possible health effects of herbicide exposure, the committees decided to review studies of other groups potentially exposed to the herbicides used in Vietnam (2,4,5-trichlorophenoxyacetic acid [2,4,5-T], 2,4-dichlorophenoxyacetic acid [2,4-D], cacodylic acid, and picloram), 2,3,7,8-tertachlorodibenzo-p-dioxin (2,3,7,8-TCDD, TCDD, or dioxin), phenoxy herbicides, chlorophenols, and other compounds. These groups include chemical production and agricultural workers; people possibly exposed heavily to herbicides or dioxins as a result of residing near the site of an accident or near areas used to dispose of toxic waste; and residents of Vietnam. The committees felt that considering studies of other groups could help address the issue of whether these compounds might be associated with particular health

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