Combat and herbicide exposures in Vietnam among a sample of American Legionnaires

A cross-sectional survey of 6810 randomly selected members of The American Legion in six states who served in the U.S. Armed Forces during the Vietnam Era was conducted by a mailed questionnaire. Combat stress was evaluated by a previously validated eight-item scale. Exposure to Agent Orange and other herbicides was estimated via exposure probability index previously developed by the authors which uses an algorithm based on the combined Air Force and Joint Services HERBS files of spray data. Two-fifths of the men had served in Southeast Asia, generally at the same time during which the major proportion of herbicides were used; the remaining subjects served elsewhere. Both combat and Agent Orange exposure exhibited distinct, meaningful distributions among Vietnam veterans with service in Southeast Asia and were also correlated with each other (r = 0.24). Our analysis demonstrates conclusively that mere presence in Vietnam cannot be used as a proxy for exposure to Agent Orange. Categorization of Vietnam veterans according to herbicide exposure can be successfully accomplished, based on an existing detailed herbicide application data base. This analysis, together with the consistent dose-related results obtained in this series of papers on health and behavioral effects, demonstrates the utility of questionnaire-derived herbicide and combat exposure measures for epidemiologic study of Vietnam veterans.