In response to the request, the Institute of Medicine (IOM) of NAS convened a committee, whose conclusions IOM published in 1994 in Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam (hereafter referred to as VAO). The work of later committees resulted in the publication of biennial updates (Update 1996, Update 1998, Update 2000, and Update 2002) and in focused reports on the scientific evidence regarding type 2 diabetes (Type 2 Diabetes), acute myelogenous leukemia in children (Acute Myelogenous Leukemia), and the latency period for respiratory cancer (Respiratory Cancer). This report is the fifth review of recently published scientific evidence regarding associations between health outcomes and exposure to TCDD and other chemical compounds in herbicides used in Vietnam.


In accordance with PL 102-4, the Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides (Fifth Biennial Update) was asked to “determine (to the extent that available scientific data permit meaningful determinations)” the following regarding associations between specific health outcomes and exposure to TCDD and other chemical compounds in herbicides:

A) whether a statistical association with herbicide exposure exists, taking into account the strength of the scientific evidence and the appropriateness of the statistical and epidemiological methods used to detect the association;

B) the increased risk of the disease among those exposed to herbicides during service in the Republic of Vietnam during the Vietnam era; and

C) whether there exists a plausible biological mechanism or other evidence of a causal relationship between herbicide exposure and the disease.

In conducting its study, this committee operated independently of the Department of Veterans Affairs (VA) and other government agencies. The committee was not asked to and did not make judgments regarding specific cases in which individual Vietnam veterans have claimed injury from herbicide exposure. This report provides scientific information for the Secretary of Veterans Affairs to consider as VA exercises its responsibilities to Vietnam veterans. The committee was not charged to focus on broader issues, such as the potential costs of compensation for veterans or policies regarding such compensation.


To fulfill its charge of assessing whether specific human health effects are associated with exposure to at least one of the herbicides or TCDD, the committee concentrated its review on epidemiologic studies. The committee also consid-

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