This past weekend, doctors in Vienna confirmed that Ukrainian presidential candidate Viktor Yushchenko has been suffering from dioxin poisoning. Since September, Yushchenko has had ulcers in his stomach and intestines, problems with his liver and spleen, and disfiguring facial cysts that have left him looking far older than he is. What is dioxin, anyway, and why does it have such wild effects?
The term dioxin actually refers to a family of more than 70 isomers of highly toxic, man-made organic compounds—dioxins—that are byproducts of some industrial processes and waste incineration. Dioxins are fat-soluble, so they tend to accumulate in the tissues of the animals who encounter them, and it can take many years for the compounds to break down. Any person living in an industrialized country has dioxins in his or her body—we ingest them when we eat animal fats or animal-fat byproducts.
It's unclear how harmful these low doses could be. Some animals begin to show symptoms of poisoning when they're given doses only two or three times the level of dioxins in the average person's body. Research has shown that dioxins increase the risk of certain kinds of cancer but lower the risk of others.
At higher concentrations, though, there is no doubt about its severity: Dioxin poisoning can cause organ disease, an increased risk of cancer and heart attacks, a suppressed immune system, hormonal imbalances, diabetes, menstrual problems, increased hair growth, weight loss, and, most obviously, the facial cysts known as chloracne. No one really knows how dioxins create this rash of maladies. Chloracne, for example, seems to be the result of an excess growth in cell linings that leads to the production of more facial oils—i.e., a volcanic acne breakout—but scientists don't understand why dioxins have this effect on cells.
Yushchenko could have been poisoned with as little as a drop of relatively pure dioxin, which could have been synthesized in a lab. Because some isomers of dioxin can have half-lives longer than seven years, significant amounts of poison could remain in Yushchenko's system for the rest of his life, in effect continually poisoning him and leaving him permanently disfigured. But it is also possible that his symptoms could clear up within a year or two.
Another feature of the poison is that it takes a long time for the symptoms to show up—one reason Yushchenko's malady was not diagnosed earlier is that his chloracne took several weeks appear. The long onset time, however, means it is less likely that Yushchenko could have been poisoned only one night before he fell ill, when, as has been widely noted, he dined with the head of Ukraine's security service.
There are very few known cases of dioxin poisoning in history. In 1976, tens of thousands of people in Seveso, Italy, were exposed to several pounds of airborne dioxins after an industrial accident; many exhibited very severe symptoms similar to Yushchenko's. And 1997 in Vienna, five employees of a textile institute may have been intentionally poisoned with a particularly strong isomer of dioxin, which rendered two very ill but killed neither. The police were never able to figure out who or what was responsible.
Explainer thanks Arnold Schecter at the University of Texas School of Public Health at Southwestern Medical Center in Dallas and Robert Moore of the University of Wisconsin in Madison.