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1 Executive Summary
Pages 1-16

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From page 1...
... (IOM, 1996~. The present IOM report is the second updated review and evaluation of the newly published scientific evidence regarding associations between diseases and exposure to dioxin and other chemical compounds in herbicides used in Vietnam.
From page 2...
... whether there is a plausible biological mechanism or other evidence of a causal relationship between herbicide exposure and the disease. In addition to bringing the earlier scientific evidence up to date, the committee has addressed five specific areas of interest identified by the Department of Veterans Affairs (DVA)
From page 3...
... The committee focused most of its efforts on reviewing and interpreting epidemiologic studies, in order to evaluate the extent to which the scientific literature does or does not suggest that particular human health effects are associated with exposure to herbicides or dioxin. The committee weighed the strengths and limitations of the scientific data in VAO and Update 1996, as well as the newly published scientific data, and reached its conclusions by interpreting the new evidence in the context of the whole of the literature.
From page 4...
... Results suggest that in utero and lactational TCDD exposure selectively impairs rat prostate growth and development. TCDD exposure in gestating animals results in malformations of the external genitalia, including complete to partial clefting of the phallus.
From page 5...
... Limited evidence from bioassays published during the past two years suggests that cacodylic acid may promote urinary, bladder, kidney, liver, and thyroid gland cancer in some species of animals. EXPOSURE ASSESSMENT Assessment of individual exposure to herbicides and dioxin is a key element in determining whether specific health outcomes are linked to these compounds.
From page 6...
... Participants in Operation Ranch Hand and members of the Army Chemical Corps are exceptions to this pattern, and it is likely that there are others who served in Vietnam who had exposures comparable in intensity to members of the occupationally exposed cohorts. Although it is currently not possible to identify this heavily exposed fraction of Vietnam veterans, the exposure assessment research effort presently under way may allow progress to be made on this important question.
From page 7...
... There is limited/suggestive evidence of an association between exposure to herbicides and the following health outcomes: Respiratory cancers (lung/bronchus, larynx, trachea) Prostate cancer Multiple myeloma Acute and subacute transient peripheral neuropathy Spina bifida in the children of veterans Porphyria cutanea tarda Inadequate/Insufficient Evidence to Determine Whether an Association Exists The available studies are of insufficient quality, consistency, or statistical power to permit a conclusion regarding the presence or absence of an association.
From page 8...
... Immune system disorders (immune suppression and autoimmunity) Circulatory disorders Respiratory disorders Skin cancers Limited/Suggestive Evidence of No Association Several adequate studies, covering the full range of levels of exposure that human beings are known to encounter, are mutually consistent in not showing a positive association between exposure to herbicides and the outcome at any level of exposure.
From page 9...
... New studies of production workers continue to show weak but consistent evidence of effects on prostate cancer mortality, whereas new research on agricultural workers shows no indication of increased risk. A detailed and wellconducted analysis of Australian male Vietnam veterans' mortality (Crane et al., 1997)
From page 10...
... A recent community based case-control study examining herbicide exposure and skin cancers drew the attention of the committee (Gallagher et al., 1996~. This study, which controlled for a number of factors known to influence skin cancer rates, found increasing risk of squamous cell carcinoma with increasing lifetime exposure to herbicides.
From page 11...
... Many animal studies provide potential biological mechanisms for an association between herbicide exposure and diabetes risk. Although the majority of earlier reports on humans suggest little association, the potentially more definitive 1997 report from the Ranch Hand study (Henriksen et al., 1997)
From page 12...
... A variety of practical difficulties relating to exposure assessment and other data requirements, however, have limited the use of these methods in epidemiologic studies of environmental carcinogens. In response to the request from the DVA to explore latency issues related to herbicides used in Vietnam, the committee attempts in Chapter 8 to establish a methodology to address the timing of herbicide exposure and the risk of cancer.
From page 13...
... Thus, further data on prostate cancer incidence would be of great help, since relatively few men with prostate cancer die from it. Overall, the data on latency do not alter the committee's conclusions with regard to the categories of evidence for individual cancer sites, but they do provide some information on how long the effects of herbicide exposures last.
From page 14...
... The committee found this body of evidence sufficient for reaching the conclusions about statistical associations between herbicides and the health outcomes. However, the lack of adequate data on Vietnam veterans per se complicates the quantification of any increased risk of disease among individuals exposed to herbicides during service in Vietnam.
From page 15...
... 1996. Chemical exposures, medical history, and risk of squamous and basal cell carcinoma of the skin.
From page 16...
... 1996. Cause specific Sty Ad cancer Incidence mung employees exposed to 2,3,7,8-TCDD ^r ~ 1933 rector ~cidenL OccupOon~ Ad ~v1mn~nt~ Redo cine 33:606-612.


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