See the listing entitled: " Health effects of Vietnam service, ADF Health, Vol 4, Sept 2003 - PDF File Health effects of Vietnam service
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By Dr Eileen J Wilson, MSc, PhD
Dr Keith W A Horsley, MB BS, MPubAdmin
The Institute of Medicine publication Veterans and agent orange 15 provides researchers with an extensive review of information on the health effects of dioxin exposure and Vietnam service. This literature review, first published in 1994, is updated every two years and draws on veteran studies and studies of occupational and environmental exposure. The report categorises the association between specific health outcomes and exposure to herbicide into four groups: conditions with sufficient evidence of an association, conditions with limited/suggestive evidence, conditions with inadequate/insufficient evidence, and conditions with limited/suggestive evidence of no association. These categories are based on statistical association reported in the literature, not on causality. The strength of the reported association is assessed on the quality of the study and the extent to which chance, bias, and confounding were addressed. In the latest update of Veterans and agent orange,
16 five diseases were classified as having sufficient evidence of an association with herbicide exposure. These diseases are: chronic lymphocytic leukaemia, soft-tissue sarcoma, non-Hodgkin's lymphoma, Hodgkin's disease, and chloracne. An additional seven diseases have limited or suggestive evidence of an association between herbicides and outcome. That is, there is at least one high quality study that shows a positive association, but the results of other studies are limited and inconsistent. The seven conditions are: respiratory cancer, prostatic cancer, multiple myeloma, acute and subacute transient peripheral neuropathy, porphyria cutanea tarda, type 2 diabetes and, in children of veterans, spina bifida maxima. Recent developments The difficulty for epidemiological studies of Vietnam veterans has been the inability of researchers to accurately quantify and separate the exposure associations of herbicides and other wartime hazards with long-term health outcomes. Australian studies have generally assessed exposure as Vietnam service and refined this only to the level of Service branch, corps grouping, and time in Vietnam. A recent Australian report by the National Research Centre for Environmental Toxicology has identified a potential exposure of Navy personnel to dioxins through potable water produced by evaporative distillation.
17 By constructing a model of the evaporative distillation system used on HMAS Sydney, this study has shown that, in the process of evaporative distillation of potable water, organochlorine pesticides and dioxins, if they had been present in the source sea or estuarine water, would have codistilled and been concentrated. Possible exposure to dioxin for Navy members through the ingestion and personal use of the potable water was estimated to have been several orders of magnitude above what are acceptable standards today. Exposure assessments in US studies have relied on the US Department of Defense HERBS file. This is a comprehensive file of the Air Force Ranch Hand herbicide spray missions. However, the file did not contain sufficiently coherent data to formulate an exposure reconstruction. Recent advances by the Columbia University group led by Stellman have greatly increased the potential for researchers to make more accurate assessments of exposure to herbicides for specific military units deployed during the Vietnam conflict.
18 The group has developed a geographic information system that characterises exposure to herbicides in Vietnam. The system has combined several databases, some only recently discovered in US Defense archives, which incorporate flight paths of aerial spray missions, the amount and type of agents sprayed, identification and location of military units and troops, land features, soil typology, and location of civilian populations to produce an exposure opportunity index (EOI). The EOI is based on the proximity in time and space to spraying. It does not measure dose, but provides a systematic method for assessing potential exposure. A user-friendly system is being developed which will The Army Vessel (AV) 1355 Vernon Sturdee on the Mekong River, 1967, with US riverine boat. Note the defoliated riverbanks and lack of protective clothing worn by the gunner. Courtesy of David Perham, veteran of 32 Small Ship Squadron.