Characterization of Exposure to Agent Orange in Vietnam Veterans as a Basis for Epidemiological Studies

Between 1961 and 1970, the U.S. military engaged in massive chemical defoliation and crop destruction operations in Southeast Asia. In 1985, nearly two decades after the spraying had ceased, a landmark tort settlement was reached between a class of Vietnam veterans and the chemical manufacturers that had supplied the Agent Orange and other military herbicides to the U.S. Department of Defense. It is notable that, at the time of the settlement, there was little convincing epidemiological evidence available, either positive or negative, on the health consequences to veterans of the herbicide operations. Today, more than three decades after this massive environmental exposure, there is still a dearth of epidemiological data on the extent to which adverse health consequences resulted from the use, storage, and disposal of the herbicides in Vietnam. This paucity of epidemiological data stands in stark contrast to the extensive amount of experimental data available on dioxin, an important contaminant in about 60% of the herbicide sprayed. Much laboratory data convincingly demonstrate dioxin's extreme toxicity. The scientific literature also is growing with respect to the carcinogenicity of the organic arsenical that was a primary component of the Agent Blue used to destroy enemy food crops. Many epidemiological studies have been carried out on other, much smaller populations exposed to the same chemicals. Indeed, when the Institute of Medicine (IOM) conducts its biennial review of the scientific literature and provides the Department of Veterans Affairs (VA) with a summary, including its appraisal of the relationship between herbicide exposure and a list of health outcomes, it relies to a large extent on the studies carried out of non-veteran populations to support its conclusions. The degree to which these other studies correctly estimate the health effects in Vietnam veterans is not known. Thus there continue to be practical ramifications to the paucity of definitive epidemiological studies on a sufficiently large exposed population of either veterans or Vietnamese citizens