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.

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.

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Objectives This study compares a statewide telephone health survey and EHR data from a large Wisconsin health system to estimate asthma prevalence in Wisconsin. Methods Frequency tables and logistic regression models were developed for children and adults using Wisconsin Behavioral Risk Factor Surveillance Survey (BRFSS) and University of Wisconsin primary care clinic data. Adjusted odds ratios (OR) from each model were compared. Results Between 2007 and 2009, the EHR database contained 376,000 patients (30,000 with asthma) compared to 23,000 (1,850 with asthma) responding to the BRFSS telephone survey. Adjusted ORs for asthma were similar in magnitude and direction for the majority of covariates, including gender, age, and race between survey and EHR models. The EHR data had greater statistical power to detect associations than survey data, especially in pediatric and ethnic populations, due to larger sample sizes. Conclusions EHRs can be used to estimate asthma prevalence in Wisconsin adults and children. EHR data may improve public health chronic disease surveillance using high quality data at the local level to better identify areas of disparity, risk factors, and guide education and healthcare interventions.