James Nachtwey

Figuring out what the dioxin contaminant in Agent Orange has done to humans has involved dedicated scientists here and abroad in an investigation lasting decades.

At first, the scientific debate over the use of herbicides in Vietnam dealt with the ecological impacts of spraying such vast areas. Today, the controversy surrounds the effects on human health of TCDD or dioxin, the toxic contaminant in the 2,4,5-T component of Agents Orange, Pink, Purple and Green.


During the War

The scientific community began to protest the use of herbicides in Vietnam as early as 1964,when the Federation of American Scientists objected to the use of chemical and biological weapons that they felt violated the Geneva Agreements of 1925. The American Association for Advancement of Science (AAAS) issued a resolution in 1966 calling for a field investigation of the herbicide program in Vietnam. In 1967, seventeen Noble Laureates and 5,000 other scientists signed a petition asking for the immediate end to the use of herbicides in Vietnam.

The Department of State sent F.H. Tschirley, an American plant ecologist, to Vietnam in March 1968 to assess the ecological effects of the herbicides. He found that the herbicides “were having a profound effect on the plant life in Vietnam.” Unfortunately, his visit took place during the dry season when many of the trees were naturally defoliated, so he was not able to get first hand documentation of the extent of the damage.

The Society for Social Responsibility in Science decided to send its own expedition team in March 1969. The team found that “the chemicals had seriously damaged the ecology of Vietnam and may be a serious threat to health, livelihood and social structure of Vietnam hill tribes.” Even though the war made it difficult to access areas of the country, subsequent teams of American scientists traveled to Vietnam to document the ecological and health effects of Agent Orange.

It was not until 1969 that concern was raised about the health effects of the herbicides. Although reports had been coming back earlier of people becoming dizzy, coughing, having headaches, vomiting and experiencing diarrhea, this was often attributed to an allergic reaction to the herbicides, which were sprayed in 20–50 times the concentrations used for agricultural purposes. Complicating the reports of illness resulting from exposure to the herbicides was the simultaneous spraying by the US of the insecticide malathion, as a well the use the anti–personnel agent CS, which may have also caused these immediate reactions.

At first, the concern about the toxicity of the herbicides was limited to Agent Blue, which contained an arsenic compound with low animal toxicity. However, in 1969, Courtney et. al. found that the 2,4,5-T component was teratogenic (fetus deforming) in laboratory rats.

Subsequent analysis of 2,4,5-T found that it was contaminated by 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a fact that the chemical companies that were producing the 2,4,5-T had known for more than 20 years.

“Dioxin is a known carcinogen.”
– International Agency for Research on Cancer, 1997.

The National Academy of Sciences (NAS) began its own field study in Vietnam in 1970, concluding that indeed much damage had occurred and that the dioxin in the 2,4,5-T may have adverse effects on the health of the Vietnamese people.

In 1971, three scientists from Harvard University (Messelson, Baughman and Constable) tested fish from the Dong Nai and Saigon Rivers and the Can Gio coastal waters, and found elevated levels of dioxin ranging from 18–814 ppt. Tests of human breast milk revealed levels of dioxin as high as 1850 ppt. In 1986, Dr. Constable tested a random sample of 120 Vietnamese from southern Vietnam who were undergoing operations in hospitals in Ho Chi Minh City and found that 97 % of the patients had elevated levels of dioxin. There was no doubt that the dioxin from the herbicides was finding its way in the animal-life and humans in Vietnam, at least in the years during and immediately after spraying. Recent testing by Schecter et. al. at Bien Hoa, and the Hatfield Consultants near Da Nang and other former US military bases in southern Vietnam, found that the incidence of elevated levels of dioxin in human blood, breast milk or body fat is limited for the most part to those who live near these "dioxin hotspots," and eat fish or other animals that have been feeding in the dioxin contaminated regions.
Sampling by Hatfield Consultants outside Da Nang Airport, 2009.

The fact that dioxin causes reproductive abnormalities in laboratory animals has been proven over and over again by researchers and is not disputed. Similarly increased rates of particular cancers, diabetes and other diseases have been found when exposing laboratory animals to dioxin. The scientific debate occurs when attempting to transfer this finding to humans, because establishing laboratory conditions and exposing humans to dioxins is not ethical. Scientists must therefore rely on epidemiological studies, factoring out as many of the variables as possible to identify how exposure to dioxin adversely affects human health.
Quality Assurance/Quality Control in the field, 2009.

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