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MILITARY UNIT AND HERBICIDE SPRAYING DATABASES, AND EXPOSURE ASSESSMENT MODEL DEVELOPMENT 15 information about unit location and enables researchers to locate military records more easily at the National Archives and in other reference materials. Classifying and Modeling the Mobility of Military Units The Columbia University researchers developed a new concept for studying troop movement for use in reconstructing herbicide-exposure histories based on a concept they called the mobility factor. The mobility factor is a three-part classification system for characterizing the location and movement of military units in Vietnam. It comprises a mobility designation (stable, S; mobile, M; or elements mobile, E), a distance designation (usually in a range of kilometers) to indicate how far the unit might travel in a day, and a notation of the modes of travel available to the unit (air; groundâtruck, tank, or armored personnel carrier; or water). They then assigned a mobility factor to every unit that served in Vietnam. The mobility-factor concept simplifies the task of characterizing exposure of military personnel to hazardous substances and conditions during the course of military conflict. The mission of the organization had to be considered in conjunction with the organizational structure when mobility factors were being assigned. For example, if the mission was transportation, the mobility of the unit would vary with the command. In some cases, the mobility factor was determined in whole or in part by the type of installation to which it was assigned (for example, an airfield or a fire-support base). Not all stable units remained in the same location throughout the war. The researchers wrote a program that provides a list of all stable units that âmovedâ, according to the database. In assessing the data, they found that in most cases the âmoveâ was realâa unit was reassigned to a different location. In some cases, however, typographic errors were responsible for the ostensible movement. In other cases, units were reclassified because some elements were, indeed, mobile. Because the mobility factor was a new concept, the researchers assembled a panel of military experts to review the concept itself and to examine the designations given to the military units stationed in Vietnam. In general, the concept was strongly endorsed by the panel, and the mobility assignments given to particular units were approved.
MILITARY UNIT AND HERBICIDE SPRAYING DATABASES, AND EXPOSURE ASSESSMENT MODEL DEVELOPMENT 16 Stable Units An important distinction made by the researchers was that the great majority of military units assigned to Vietnam were âstableâ; that is, their missions did not require routine movement around Vietnam, and they were assigned to a specific base-camp location. Thus, the military-occupancy probability assigned to these units would be 100% for the grids that they occupied. Initially, the Columbia University researchers made a rough working estimate of the exposure-opportunity scores for the stable units. Most units were in the low-exposure category for aerial applications because the strategy underlying the herbicide projects was to defoliate or destroy crops in areas away from the main support- troop locations. However, some stable units were in heavily sprayed areas, and the perimeters of the base camps were also subject to backpack and other, more poorly documented spraying. In investigating the issue further, the researchers identified a previously unrecognized source of supplementary data in the National Archives. From those data, they deduced that each time an installation or base camp was built or occupied by American forces, a formal land-transfer agreement was executed between the governments of South Vietnam and the United States. These agreements contained specific maps and descriptions of, for example, base camps and power stations. The researchers reviewed those documents and extracted extensive quantitative data, including complete dimensions of about 200 base camps, locations of airfields, water supplies, and hospitals. In addition, they were able to identify the precise locations of 36 military units that were stationed in those installations. They also obtained coordinates for a large number of perimeters of U.S. installations. The data were used for additional quality control of the stable-units database. The stable-units database of base-camp locations and dates of residence created by the researchers covers about 80% of the troops stationed in Vietnam. Mobile-Troop Location Modeling The Columbia University researchers developed and tested algorithms and programs for describing and analyzing the movement of mobile battalions and their elements to further the goal of developing models of troop movement and unit dispersion. The ultimate aim was to assign military- occupancy probabilities to specific grids in the map of
