Word: dioxin
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Obviously, instead of searching the Bests for this year's perfect metaphor, we should be studying the Worsts, some of which we have also identified. The Environment rubric "A Little Is Too Much" refers to the discovery that even trace amounts of dioxin can be harmful. Doesn't it also apply to the year as a whole? A little O.J. is too much; even a trace amount of Newt Gingrich goes a long way; a mere grain of Forrest Gump is dangerous. In the cases of love, valour and compassion, of course, too much would still have been too little...
...evidence from laboratory studies suggests there are also effects at lower concentrations. Endocrinologist David Crews has discovered, for example, that small PCB doses can dramatically influence the ratio of male to female offspring in red-eared slider turtles. When University of Wisconsin toxicologist Richard Peterson investigated the impact of dioxin on male rats, he found that the dose needed to cause reproductive-system problems was relatively high. "But when we exposed pregnant rats to a dose 1/100th as large," he says, "we found the male offspring showed signs of reproductive dysfunction," including smaller sex organs, reduction in sperm counts...
What is especially disturbing about Peterson's work is that the levels of dioxin needed to do that kind of damage were as low as 64 nanograms per kg of body weight -- only a little greater than the 5 or 10 nanograms of dioxin and comparable chemicals found in a typical kilogram of human tissue. It is not surprising that these compounds are so biologically active, since they are metabolized in a fashion similar to natural chemicals. Says Linda Birnbaum of the EPA's Health Effects Research Laboratory, who was one of the driving forces behind the agency's decision...
...this is a big but -- some species are more sensitive to dioxin than others. Just because rats and fish are affected in certain ways does not necessarily mean that humans will have comparable reactions. And doses that harm animals are not necessarily large enough to damage people. On the other hand, humans soak up many different chemicals, and the results may be cumulative...
Whatever the impact of pollutants on men and women, solid evidence is hard to come by. Even when a cause-and-effect relationship is established, as in major industrial accidents, the data are confusing. In the years after a large dioxin release in 1976 in Seveso, Italy, for example, the incidence of leukemias, lymphomas and soft-tissue cancers in men and gall-bladder and bile- duct cancers in women rose -- but breast and endometrial cancers in women actually went down. Possible reason: dioxin may sometimes interfere with the hormone system in beneficial ways...