This chapter discusses data on the possible association between exposure to the herbicides used in Vietnam—2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), picloram, and cacodylic acid—and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a contaminant of 2,4,5-T, and several noncancer health outcomes: respiratory disorders, immune-system disorders, diabetes, lipid and lipoprotein disorders, gastrointestinal and digestive disease (including liver toxicity), circulatory disorders, and adverse effects on thyroid homeostasis. The committee also considers studies of exposure to polychlorinated biphenyls (PCBs) and other dioxin-like chemicals informative if their results were reported in terms of TCDD toxic equivalents (TEQs) or concentrations of specific congeners.
In previous updates, chloracne and porphyria cutanea tarda (PCT) were considered along with these chronic noncancer conditions. These are conditions that are quite well accepted to be associated with dioxin exposure, but when they occur this happens within a matter of months of the exposure. In this update these two health outcomes have been moved to an appendix on short-term effects along with transient early-onset peripheral neuropathy, which had previously been discussed in the chapter on neurologic disorder.
For each type of health outcome, background information is followed by a brief summary of the findings described in earlier reports by the Institute of Medicine (IOM) Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides. In the discussion of the most recent scientific literature, studies are grouped by exposure type (Vietnam veteran, occupational, or environmental). For articles that report on only a single health outcome and that are not revisiting a previously studied population, design information is summarized