It has been nearly 30 years since the last American helicopter lifted-off from the roof of the US Embassy in Saigon (now Ho Chi Minh City), yet the possible effects of the Vietnam War on the health of over 3 million US veterans are only now beginning to receive adequate attention. One cause for concern is the aftermath of exposure to Agent Orange.

What is Agent Orange?
Agent Orange is the code name for a powerful chemical developed for the military, primarily for use in tropical climates. It is a mixture of two powerful phenoxy herbicides 2,4,5-T and 2,4-D. The former was also contaminated with high levels of 2,3,7,8-tetrachloro-p-dioxin ("dioxin"), which is highly toxic to animals and is rated a Class 1 carcinogen by the International Agency for Research on Cancer (IARC). The code name “Agent Orange” is derived from the orange band that was used to mark the drums in which the product was stored. The purpose of the product was to deny an enemy cover and concealment in dense terrain by defoliating trees and shrubbery. In particular, it was effective against broad-leaf foliage, such as the dense jungle-like terrain found in Southeast Asia. Over 19 million gallons of these and other herbicides were dispersed between 1961 and 1971.

Three C-123 aircraft sorties dispersing herbicides during a mission over South Vietnam.

The impact of chemical exposure
Beginning in 1991, the Institute of Medicine set up a Congressionally mandated Committee to study the health effects of Agent Orange on veterans (Alfred I. Neugut, MD, PhD, of NewYork Presbyterian Hospital was one of the original members). The Committee found "sufficient evidence" to link exposure to soft-tissue sarcoma, non-Hodgkin's lymphoma, and Hodgkin's disease, and "suggestive" evidence of association with lung and prostate cancer. However, the findings were based indirectly on occupational and other types of investigations because few veteran studies have assessed herbicide exposure.

In response to the need for further investigation, the National Academy of Sciences awarded a contract in 1998 to Columbia University researchers Drs. Jeanne and Steven Stellman to develop an exposure assessment methodology that would be applicable for large-scale epidemiological studies. Their work, which is nearly complete, involves the creation of a Geographic Information System (GIS), a powerful research tool that combines and integrates a variety of data resources. It links the locations of military units with those of herbicide spraying, and factors in amount and type of herbicide, distance, and duration of exposure, to create a numerical "exposure opportunity index" that can play the role of dosage in epidemiological studies. Data and resources for the project include so-called HERBS files—detailed listings of the flight path coordinates of over 9000 herbicide spray missions carried out by the US Air Force and others—which also specify gallons sprayed and herbicide type (organic arsenic and picloram were used besides Agent Orange). Considerable effort was spent to correct and update these files, using documents in the National Archives. The researcher team also created the first complete database of the 5000 military units and their locations in Vietnam.

Three generations of Vietnamese fishing villagers, 2002 (photo courtesy of Dr. Jeanne M. Stellman)

As part of the project, a user-friendly software system for exposure assessment will be made available to interested researchers in summer 2002. The project was also presented at a recent conference in Hanoi, jointly sponsored by the National Institute of Environmental Health Sciences and the Vietnamese government. Scientists from both countries expressed a great interest in using the tool for future epidemiological studies.

To read more about Dr. Jeanne Stellman’s research focused on women, gender bias, occupational health, and health of veterans, read her “Spotlight” article here.

Editor’s Note (About the Researchers):

Jeanne M. Stellman, PhD (principal investigator), is a Professor of Clinical Public Health (Health and Policy Management), at the Mailman School of Public Health, Columbia University.

Steven D. Stellman, PhD (co-principal investigator), is a Professor in Epidemiology at the Mailman School of Public Health, Columbia University, and a member of the Herbert Irving Comprehensive Cancer Center.