the exposure assignments it generates, and other proximity-based approaches with the potential of estimating exposure more accurately should be explored. Moving beyond proximity-based exposure measures would require additional data on herbicide fate and transport, individual behavior, and pharmacokinetics, and some of this information is not likely to be available.

To conduct epidemiologic studies using the exposure assessment model requires data on when and where each veteran served in Vietnam and on the veteran’s health outcomes. It is generally possible to obtain useful data on individuals’ unit assignments and unit locations, but the processes of gaining permission for access to relevant military records and of collecting data for individuals are likely to be administratively difficult for many researchers as well as time consuming and costly.

Despite the shortcomings of the exposure assessment model in its current form and the inherent limitations in the approach, the committee agreed that the model holds promise for supporting informative epidemiologic studies of herbicides and health among Vietnam veterans and that it should be used to conduct studies. The committee offers criteria that VA should draw on as a basis for developing a request for proposals, and it recommends that VA work with the Department of Defense and the National Archives and Records Administration to facilitate access to and interpretation of military records for use in the studies.

Between 1962 and 1971, several herbicides—most notably the product known as Agent Orange—were used in Vietnam by U.S. forces and their allies for defoliation of forest areas, destruction of crops, and control of vegetation around the perimeters of troop encampments. Since then, many studies have been conducted to examine whether health problems experienced by some Vietnam veterans might be linked to their wartime exposure to any of these herbicides or to a particular contaminant—2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)—that was present in some of them.1

A fundamental and persisting challenge in these studies has been to determine the amount of herbicide in the environment in Vietnam, identify military personnel who were exposed to the herbicides, distinguish them from personnel who were not exposed, and estimate the herbicide or dioxin dose that exposed individuals received. In an effort to improve exposure assessment for Vietnam veterans, a group of academic researchers has

1

Throughout this report the term “herbicide” encompasses the TCDD contaminant unless specifically stated otherwise.



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