Word: dioxins
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Dates: during 1990-1999
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Environmental groups still fear that even minute amounts of dioxin, which was an ingredient in the Vietnam-era defoliant Agent Orange, can cause epidemics of cancer. But Vernon Houk, the federal official who recommended the Times Beach evacuation, is no longer sure. Recent studies suggest that the chemical may not be so dangerous. In an interview with the St. Louis Post- Dispatch, Houk declared, "We should have been more up front with the Times Beach people and told them, 'We're doing our best with the estimates of the risk, but we may be wrong.' I think we never added...
...truth, the Environmental Protection Agency has ordered a reassessment of dioxin's risks and, depending on the findings, may relax rules on exposure to the chemical. That will be cold comfort to the displaced citizens of Times Beach. "Houk announced his decision with all the power and authority of science behind him," says Marcel LaFollette, a professor of science policy at George Washington University. "Now he's saying 'Never mind.' A reasonable person would ask the scientist, 'Why can't you make up your mind...
...unavoidable amount of uncertainty is built into every scientific investigation. To determine the risk of disease from trace amounts of dioxin, researchers had to assume that if it caused cancer in laboratory animals, then it could cause cancer in humans. In addition, because no one completely understands how toxins trigger cancer, scientists chose a mathematical model that assumes a linear relationship between the amount of toxin consumed and the incidence of malignancy. In other words, if a pound of dioxin caused cancer in 50 out of 100 subjects, then half a pound would trigger 25 cases...
Using such calculations for dioxin produced a conclusion that ingesting an infinitesimal amount of the compound each day over a lifetime -- about 0.006 trillionths of a gram per kilogram of body weight (or 0.014 trillionths of an ounce for a 150-lb. man) -- would cause 1 cancer among 1 million people. The contamination at Times Beach was 1,000 times as great as this safety limit...
Since then, however, a lot more has been learned about how dioxin affects the body. As a result, some scientists believe dioxin and other chemicals may trigger cancer only if a certain threshold amount is present -- and that amount could be well over 1,000 times as great as the safety limit, i.e., above the level of most of the contamination at Times Beach. If so, the government has reason to amend its regulations on many compounds in addition to dioxin. One of the biggest beneficiaries would be the paper industry, which is under pressure to reduce the level...