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Characterizing Exposure ... Final Report
CONTRACT SUMMARY
The overall goal of the Columbia University research effort was to determine whether a valid
and useful method could be developed for estimating Vietnam veterans' opportunity to be
exposed to herbicides on the basis of historical reconstruction of relevant military records. The
conceptual framework for the overall project included research on and quality control for the
identification and reconstruction of military records, development and testing of exposure-
opporiunity models that used those records, and research on selected Vietnam veterans to
understand the extent to which covariates or confounders need to be taken into account in
epidemiologic studies of the health effects of herbicides on Vietnam veterans.
The goal was to elucidate the basic determinants of exposure: person, place, and time. With
regard to person, the aim was to identify the specific locations of a veteran's military units and
the specific tasks that may have resulted in exposure to herbicides. The Columbia University
researchers were also interested in elucidating in-service and post-service experiences that might
have affected any potential response to herbicide exposure so that they could be controlled for in
future epidemiologic studies. They aimed to determine the extent to which the long period since
the end of the spraying activities could affect a veteran's recall and the researchers' ability to
identify and locate potential epidemiologic cohort members.7 With respect to place and time,
the researchers' goals were to optimize the quality of the data available on herbicide spraying
and to develop statistically robust models for herbicide-exposure opportunity for the entire
period of the Vietnam War.
Another research aim was to provide guidance for future epidemiologic studies on the degree
to which important confounders and covariates might influence the outcome of epidemiologic
health studies with respect to herbicide exposures. On the basis of previous studies of veterans'
6 Several terms are used to specify the organizational position and size of a military unit. The primary terms used in
the US Army during the war were corps, division, brigade, battalion, company, platoon and squadron. Other
services used different designations.
7 All protocols involving human subjects were submitted to the Columbia University Institutional Review Board and
were approved. They included procedures and systems for preventing records access by persons who were not
members of the study team.
7
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Characterizing Exposure ... Final Report
health, including their own published work (StelIman SD et al., 198Sa, 198Sb; StelIman IM et
al., 1988; Snow et al., 1988), the contractors hypothesized that the experience of combat might
have a profound effect both on subsequent health and on such important lifestyle factors as
smoking and drinking, which, in turn, heavily influence disease outcomes. They thus undertook
a large-scale survey of veterans to gather and evaluate the association among demographic,
socio-economic status and behavior variables; military service history; self-reported exposures to
herbicides and to combat; measures of post-traumatic stress disorder (PTSD) and other
psychiatric symptoms; and numerous health outcomes. A focused study of women veterans was
also conducted and an outreach effort was conducted to involve black and Hispanic veterans in
order to evaluate the generalizability of such measures.
The working plan proposed by the contractor consisted of fives interrelated projects on
various methodologic aspects of characterizing herbicide exposures of American troops who
served in Vietnam. Each project was related to an aspect of the historical reconstruction of
exposure to herbicides. The projects were as follows:
Project ]: Military Unit and Herbicide Spraying Databases, and Exposure Assessment Mode!
Development
· Compilation and assessment of data on troop locations.
· Collection of data on the application of herbicides in the wartime aerial spraying program
and other releases such as perimeter spraying.
· Analysis of the database contents to evaluate their suitability for use in the historical
reconstruction of exposure to herbicides.
· Development and refinement of a means of characterizing wartime exposure of US veterans
to herbicides.
A sixth proposed project would have developed priorities and methods for epidemiologic research based on the
findings of Projects 1-5, other available health-outcome databases, and additional technical and pragmatic
considerations. This project was not included in the final contract, because a decision was made to focus on
activities related to the development of an exposure-assessment model.
8
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Characterizing Exposure ... Final Report
· Creation of a user-friendly software system to facilitate the estimation of exposure.
Project 2: Covariates, Confounders, and Consistency: Characterizing the Vietnam Veteran for
Epidemiologic Studies
· Examination of self-reports of military service, exposure to herbicides, and confounders and
covariates of methoclologic interest (such as combat experience).
· Evaluation of validity of veteran recall and various approaches to obtaining self-reportec3
data.
Project 3: Evaluation and Standardization of Military Records for Use in Epidemiologic
Studies9
Certification of the Vietnam-era military personnel ant! other records that contain
information potential relevant to epiclemiologic studies.
· Development and testing of a standardized means to abstract records data needler! to
determine a veteran's ciates of service in-country, military unites), occupationts), and other
service-relatecl information potentially relevant to epidemiologic studies.
Evaluation of the consistency of the records data with self-reports of military service and
experience.
Development of a guide to obtaining and abstracting military records for use in
epidemiologic research.
Project 4: Biomarkers of TCDD (DioxinJ Exposure in Vietnam Veterans
9 This project was entitled Evaluation and Standardization of Military Personnel Records for Epidemiologic Studies
in the contractor's proposal. It is revised here to clarify that both personnel and other records were examined.
9
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Characterizing Exposure ... Final Report
.
· Evaluation of TCDD in blood serum samples from selected veterans likely to have been
heavily exposed and of an appropriate selection of Vietnam-era veteran controls using high-
resolution gas chromatography/high-resolution mass spectrometry analysis.
Examination of the utility of chemical-activated luciferase gene expression (CALUX)
analysis as a lower-cost method of screening for TCDD exposure in studies of Vietnam
veterans.
Project 5: Analysis of International Agency for Research on Cancer (lARC) Tissue Samples
of Selected Vietnamese for Dioxin and Dibenzofuran Levels in Archived Adipose Tissues
· Evaluation of the correlation between levels of TCDD and dioxin- and dibenzofuran
congeners in adipose tissue collected *om Vietnamese citizens as part of an lARC case-
contro! study tissue archive with lifetime residence-history data and herbicide-spray records,
on the basis of the exposure-opportunity index developed in Project ~ .
Evolution of Project Development and Implementation
In the course of the study, the Columbia University researchers entered considerable amounts
of data into new composite databases, creating, cleaning, and expanding archives for use in
future epidemiologic studies. They also refined their computational approaches and developed
new approaches to classifying and analyzing existing data. The researchers conducted two large
surveys to elucidate the extent to which covariates and confounders must be considered in
designing and executing studies of the effects of herbicide exposure on Vietnam veterans. In the
course of seeking access to military personnel records for research purposes, they documented
gaps and flaws in the data and identified potential barriers to conducting new studies of veterans'
health.
10
Representative terms from entire chapter:
vietnam veterans
