Dioxin is the name given to a class of highly toxic substances found in Agent Orange and some of the other Agent herbicides. The U.S. Department of Veterans Affairs claimed that Agent Orange had only "minute traces" of dioxin (in this case, the potent dioxin known as TCDD), but areas where Agent Orange was sprayed or stored show high concentrations of the compound. In some areas of Vietnam, people have blood levels of dioxin tens of times above normal [source: BBC News]. Small doses of dioxin may actually decrease the incidence of certain cancers, but in anything above small doses, dioxin has been linked to numerous, potentially deadly health problems.
The World Health Organization has classified dioxin as a "known human carcinogen" that can damage essential bodily systems, such as the endocrine, immune and nervous systems [source: WHO]. It also has been linked with miscarriages in women [source: Bertazzi et al]. Studies of people exposed to dioxins through workplace accidents have been found to have an increased risk of cancer (about 40 percent) [source: GreenFacts]. Studies of dioxin on animals have yielded similar adverse health effects.
There are different types of dioxins, some of which appear naturally in the environment, though in small quantities. Dioxin develops as a byproduct of some industrial processes, usually those that involve something being burned, like copper smelting or incinerating waste. It can also be manufactured synthetically, as it was during the Vietnam War [source: Schechner].
When dioxin isn't contained, it seeps into the ground and the groundwater sources, polluting the local ecology and becoming part of the food chain. Dioxin pollution has, in general, decreased in recent years as government regulations have caused companies to make various industrial processes cleaner, but it remains a pressing issue in Vietnam [source: Dioxin Facts].
When people eat animals and plants contaminated with dioxin, it begins accumulating in their fat tissue, since the poison is fat-soluble. Everyone has at least a small amount of dioxin in his or her body. It's unknown how long it takes dioxin to dissipate. Some forms of dioxin have half-lives lasting seven years or more, but more recent research shows that when found in large concentrations, dioxin takes far longer to decay [source: Dioxin Facts]. And when dioxin seeps into soil, its half-life increases significantly [source: Dioxin Facts].
The effects of dioxin can be clearly seen in the case of Ukrainian politician Viktor Yushchenko, who was poisoned with dioxin but survived. After being poisoned, Yushchenko's appearance changed dramatically. His once youthful face became pockmarked, scarred and shaded an eerie green-grey. He had terrible pain in his torso, in part because of lesions that contributed to his facial scarring. It's amazing that he even survived. His blood-dioxin levels were 6,000 times above normal, the second highest number recorded in a human being [source: CBC News]. He has recovered, and some of the scarring on his face has receded, but some dioxin will likely continue to be in his body for several years.