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Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam
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Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides. Division of Health Promotion and Disease Prevention. Institute of Medicine. Washington, D.C.: National Academy Press; 1994. $79.95.
This landmark book is the most current review of Agent Orange, dioxin, and health by a committee of the National Academy of Sciences. It represents the result of several years of literature review and both public and private meetings with dioxin scientists, Vietnam veterans, and others. The review was commissioned by the Office of Veterans Affairs to establish guides to issues of policy, compensation, and areas of fruitful future research. The committee, unlike the typical National Academy of Sciences committee, was not composed of experts in the field of dioxins, phenoxyherbicides, and health, but rather was a senior, prestigious group of university-based scientists who had had no previous experience with this field and presumably had no preconceived biases. It might be noted that, should this selection criterion be adhered to in the future, it would disqualify all members of this committee from membership on future committees dealing with this matter.
The committee concluded that the scientific literature contains sufficient evidence to support a positive association between certain types of cancer and exposure to Agent Orange and its dioxin contaminant. These cancers include soft-tissue sarcoma, non-Hodgkin lymphoma, and Hodgkin disease. Chloracne and porphyria cutanea tarda also fall into this category of evidence. Further, the committee found only limited, suggestive evidence of an association between Agent Orange and respiratory cancers (lung, larynx, and trachea), prostate cancer, and multiple myeloma. Evidence linking other health effects, including birth defects, cognitive and neuropsychiatric disorders, and circulatory disorders was judged insufficient to show an association; other areas had limited, suggestive evidence of no association. The committee made one unusual recommendation: Vietnam-based Agent Orange research should be done to produce new health information useful to American veterans of the Vietnam War.
The committee did not consider in any depth the relatively new, experimentally validated concept of "dioxin toxic equivalents." This concept states that dioxins and the chemically similar dibenzofurans and dioxin-like polychlorinated biphenyls act in a qualitatively similar fashion but vary quantitatively in dioxin-like toxicity. Because this was not considered, valuable data on reproductive outcome from the rice oil poisoning incidents in Japan and Taiwan were largely ignored.
Another controversial aspect of the otherwise valuable literature review was related to exposure assessment. A major dichotomy currently exists between scientists preferring to assess exposure by direct measurement of 2,3,7,8-TCDD, the dioxin contaminant of Agent Orange, in blood or adipose tissue and those who prefer indirect environmental modeling and estimation. The committee strongly tilted toward the latter opinion, to the surprise of many working in the field, including this writer.
The book complements the separate Toxicological Profiles for the dioxins, the dibenzofurans, and the polychlorinated biphenyls produced by the Agency for Toxic Substances and Disease Registry of the Centers for Disease Control and Prevention as well as the Environmental Protection Agency's extensive review of health aspects of dioxins that should be completed this year. It will be useful for the physician who needs a one-volume summary of Agent Orange and health. It should be updated in several years because extensive research on dioxins and health is currently being done. The next edition is awaited with great interest.
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