Issue Date: March 17, 2008
Agent Orange's Legacy
THE RECENT COURT of appeals decisions on several long-running cases dealing with the herbicide agent orange reminded me of just how complicated and drawn out this story is. In some ways, the herbicide—and its notorious contaminant—is as responsible for changing the perception of chemicals in the U.S. as the explosion in Bhopal, India, in 1984 and the leaking waste dump at Love Canal, N.Y., in 1978.
The agent orange story began simply enough. The U.S. government was looking for a way to deprive the enemy of shelter by defoliating the forests in Vietnam in the 1960s. It settled on a 50-50 combination of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), which it called agent orange because the drums holding the mixture were painted with an orange band. It was known at the time that 2,4,5-T was contaminated with low part-per-million levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the toxicity of which was just beginning to be realized.
Between 1962 and 1970, Air Force planes sprayed between 10 million and 12 million gal of agent orange on the Vietnamese countryside and, presumably, anyone there. By the 1970s, Vietnam War veterans were complaining of numerous health problems they claimed were caused by exposure to agent orange and specifically to 2,3,7,8-TCDD, which was by then being called simply dioxin.
Years of uproar followed. Many congressional hearings, court cases, and toxicology studies took place, and charges of government cover-ups, industry cover-ups, and government-industry conspiracies were reported. Dioxin was labeled "the most potent carcinogen known to man" and discovered to be ubiquitous in the environment.
Several incidents kept dioxin contamination before the public. In 1971, dirt roads in Times Beach, Mo., were sprayed with oil that was subsequently found to be highly contaminated with dioxin. In the panic that followed, everyone in the area was evacuated and the entire town was bought by the federal government. In 1976, a chemical plant accident spread dioxin contamination over Seveso, Italy, in what is probably the worst human exposure to dioxin.
By the end of the 1970s, some sources were reporting that Vietnamese living in areas sprayed with agent orange during the war were suffering from significant health problems and that dioxin levels in the population were high. Demands were made that the U.S. help these people and clean up the contamination.
But against the strident calls for protection from dioxin was a steady stream of research reports that could find little or no health problems to associate with most dioxin exposure. Only industrial workers with the highest exposures had diseases that researchers could show were directly caused by dioxin.
But the damage to the public's perception of chemicals had been done. The constant barrage of news reports on dioxin-caused diseases and disagreements among scientists over whether dioxin was really responsible for the health problems created a deep lack of public trust in both the government and industry when it came to chemical safety. And the research done on dioxin had secondary impacts affecting chemical regulations today.
In seeking to understand how dioxin might cause so many kinds of diseases, it was discovered that the compound mimics the action of the hormone estrogen by attaching itself strongly to estrogen receptors in cells. This discovery and the finding that other snythetic chemicals could also mimic the body's endocrine chemistry opened the door to the field of endocrine disruptors, the class of compounds that disrupts the normal chemistry of the body by replacing hormones with synthetic chemicals.
TODAY, endocrine disruptors are viewed as major environmental contaminants. They include compounds such as bisphenol A, used to make polycarbonate plastic, and the whole class of halogenated phthalates used in children's toys and other products. All are under intense scrutiny for adverse health effects.
But 2,3,7,8-TCDD is not the only dioxin found in the environment. Many toxic polychlorinated dioxins and furans are contaminants resulting from industrial manufacturing or natural processes. The Environmental Protection Agency subsequently lumped all of the dioxins and furans together, along with the more prevalent polychlorinated biphenyls (PCBs), because they have similar mechanisms of toxicity. The whole group is regulated under the name "dioxins."
The court of appeals cases were recently dismissed primarily because of legal technicalities. They involved Vietnamese citizens and Vietnam War veterans seeking compensation for injuries claimed from exposure to dioxin and agent orange. No new data on health effects were heard, and no debate occurred over who was exposed and who wasn't. Maybe people are getting tired of agent orange.
But its impact is significant. Just like the right-to-know debates after the Bhopal explosion and the cleanup laws after the Love Canal hazardous waste mess, the agent orange and dioxin saga spawned numerous regulations impacting chemical manufacturing and disposal. And as those other events did, agent orange also contributed to the low-level, general loathing many people feel for "chemicals," and that may be the most persistent legacy of all.
Views expressed on this page are those of the author and not necessarily those of ACS.
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