23 research outputs found
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A geographic information system for characterizing exposure to Agent Orange and other herbicides in Vietnam.
Between 1961 and 1971, U.S. military forces dispersed more than 19 million gallons of phenoxy and other herbicidal agents in the Republic of Vietnam, including more than 12 million gallons of dioxin-contaminated Agent Orange, yet only comparatively limited epidemiologic and environmental research has been carried out on the distribution and health effects of this contamination. As part of a response to a National Academy of Sciences' request for development of exposure methodologies for carrying out epidemiologic research, a conceptual framework for estimating exposure opportunity to herbicides and a geographic information system (GIS) have been developed. The GIS is based on a relational database system that integrates extensive data resources on dispersal of herbicides (e.g., HERBS records of Ranch Hand aircraft flight paths, gallonage, and chemical agent), locations of military units and bases, dynamic movement of combat troops in Vietnam, and locations of civilian population centers. The GIS can provide a variety of proximity counts for exposure to 9,141 herbicide application missions. In addition, the GIS can be used to generate a quantitative exposure opportunity index that accounts for quantity of herbicide sprayed, distance, and environmental decay of a toxic factor such as dioxin, and is flexible enough to permit substitution of other mathematical exposure models by the user. The GIS thus provides a basis for estimation of herbicide exposure for use in large-scale epidemiologic studies. To facilitate widespread use of the GIS, a user-friendly software package was developed to permit researchers to assign exposure opportunity indexes to troops, locations, or individuals
The Extent and Patterns of Usage of Agent Orange and Other Herbicides in Vietnam
Herbicides including Agent Orange were sprayed by United States forces for military purposes during the Vietnam War (1961–1971) at a rate more than an order of magnitude greater than for similar domestic weed control. In 1974, the US National Academy of Sciences published estimates of the extent and distribution of herbicides sprayed. Here we present revised estimates, developed using more-complete data. The spray inventory is expanded by more than seven million litres, in particular with heavily dioxin-contaminated herbicides. Estimates for the amount of dioxin sprayed are almost doubled. Hamlet census data reveal that millions of Vietnamese were likely to have been sprayed upon directly. Our identification of specific military herbicide targets has led to a more coherent understanding of spraying. Common errors in earlier interpretations of the spray data are also discussed
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Health Outcomes Among Veterans in Relation to Service and Combat Exposure in Vietnam
Introduction. The relationships among military service, combat intensity and long-term health effects were investigated in a cohort of 6,355 Vietnam-era American Legionnaires who were recruited in 1984 and followed through 1998. First, the effect of Vietnam service on coronary heart disease (CHD) risk was assessed among 3,781 veterans who responded to both questionnaires. Next, the effect of serving in Vietnam and combat exposure was investigated as risk factors for the mortality of the cohort. Finally, potential threats to the validity of this study were evaluated.Methods. Military service and lifestyle factors were assessed by questionnaires in 1984 and 1998. Vital status in 1998 was determined and causes of death were ascertained through the National Death Index. Cox proportional hazards modeling was used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for CHD incidence and mortality in relation to service location and combat exposure, adjusting for age, smoking, alcohol consumption, body mass, and hypertension. Response bias and reliability of self-reported data were examined.Results. Serving in Vietnam was associated with an increased hazard of developing heart disease (HR=1.37, 95% CI: 1.09, 1.73), after controlling for independent risk factors. Vietnam veterans experienced a 50% higher mortality than non-Vietnam veterans during 14-year follow-up (HR=1.48, 95% CI= 1.13 - 1.93), which increased with combat intensity after adjustment for other risk factors, (low combat: HR 1.17, 95% CI 0.79 - 1.73; medium combat HR=1.51, 95% CI 1.05 - 2.17; high combat HR=1.82, 95% CI 1.20 - 2.76). A stronger relationship was observed by level of combat for CHD mortality (low combat: HR =1.48, 95% CI 0.75 - 2.95; medium combat HR= 2.01, 95% CI 1.06 - 3.79; high combat HR= 2.27, 95% CI 1.08 - 4.79). Results showed that non-respondents differed only slightly from respondents for important variables potentially related to exposures and chronic disease outcomes. Furthermore, veteran self-report was moderately to highly reliable when measured over a 14 year period.Conclusions. Vietnam veterans are still experiencing higher rates of adverse health effects, even more than thirty years after their military service. These data support a long term and independent adverse effect of military service in Vietnam on cardiovascular health