Agent Orange

Agent Orange was the nickname for an herbicide used in Vietnam between 1961 and 1971 for tactical defoliation of dense terrain consisting of broad leaf plants and crops. Agent Orange was used to deny the enemy a protective jungle canopy that would cover and conceal, thereby protecting American and allied troops from undetected enemy movement. Chemically, the product is a mixture of two chemicals, known as 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid). Agent Orange was combined with diesel fuel or kerosene and usually sprayed at an altitude of 150 feet by aircraft. An estimated 19 million gallons of herbicidal agents, including more than 12 million gallons of Agent Orange, were used by the United States Armed Forces in South Vietnam during the war.

The earliest health concerns surrounding Agent Orange pertain to the product's contamination with TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), the most toxic of the dioxin chemicals. Neither the extent of exposure nor the long-term health effects among the 3.2 million Americans who served in Vietnam are fully understood. However, researchers in Vietnam are still discovering new connections between herbicide exposure and health problems in many veterans and their children. In the year 1991, The Agent Orange Act instructed the Secretary of Veteran Affairs to obtain a comprehensive evaluation of the available scientific evidence regarding the health effects of dioxin and other chemical compounds in herbicides. Since 1994, the Institute of Medicine (IOM) has issued several reports examining the health risks posed to Vietnam veterans by exposure to Agent Orange. These reports also recommended that the Department of Veteran Affairs facilitate additional epidemiological studies by independent researchers and non-governmental organizations.

The dioxin in Agent Orange accumulates in mammalian fat cells and is excreted by the body very slowly. North American scientists believe that Vietnam remains contaminated with approximately one-quarter of the dioxin introduced into the country's environment during the war, and that the best way to determine the effects of Agent Orange exposure is to conduct research in Vietnam. In 1996, the National Academy of Sciences (NAS) issued a proposal for the development of an exposure model that would become the foundation of new epidemiological research. A geographic information system (GIS) was developed as an exposure methodology to be used in large-scale epidemiological studies. A GIS is a relational database that facilitates exposure assessment by integrating extensive data resources, such as herbicide dispersal (i.e. flight paths, type of chemical, gallons dispersed), military unit locations, and locations of civilian populations. A software package transforms the locations, troops, and individuals into vectors comprised of exposure opportunity indexes. The GIS provides the ability to perform otherwise complex exposure model calculations with straightforward arithmetic procedures. Stellman et al. analyzed the HERBS data of Ranch Hand aircraft flight paths and discovered that the spray patterns of herbicides in Vietnam were not uniform. Herbicide application displayed geographic and temporal variation, and residential and military locations were located among the sprayed areas.

In March 2002, a four-day conference in Hanoi brought together toxicologists, epidemiologists, and environmental scientists from 13 countries. Following this conference, the United States and Vietnam signed an agreement establishing the first joint research program to study the health and environmental effects caused by Agent Orange and dioxin. However, as of April 2003, a joint advisory committee required to manage the initiative has not yet been established. According to American spokespersons, Vietnamese officials have not proposed its members and have not responded to requests for information regarding the program's current status in Vietnam. In addition, lack of special funding and the unwillingness by some U.S. and Vietnamese government officials to disclose details of the damage have led some experts to doubt whether the project can truly determine the health and environmental effects of this defoliant.