Document 3N3E839EEwJKj8O0qx9K5gRV6

RACHEL'S HAZARDOUS WASTE NEWS #270 Providing news and resources to the Movement for Environmental Justice - January 29, 1992 EPA's Dioxin Reassessment-Part 2 DIOXIN DAMAGES HUMAN IMMUNE SYSTEM U.S. Environmental Protection Agency [EPA] is presently reassessing the dangers of dioxin, one of the most toxic chemicals ever tested on laboratory animals. As a result of animal tests, EPA has de clared only exceedingly small amounts of dioxin "safe" for the human food supply. Americans eat food routinely containing roughly 10 to 100 times more dioxin than EPA considers safe. [See RHWN #269.1 No one makes dioxin intentionally, but many industries create dioxin as a byproduct of their main activity. Industries that emit dioxin into the environ ment (paper, plastics, chemicals, and solid waste incinerators) are being sued for their emissions by citizens claiming harm from exposure, and one industry-paper-faces billions of dollars in lawsuits. Partly to please the paper industry, and partly because there were new scientific findings worth considering, EPA chief William Reilly announced a year-long dioxin reassessment to begin in April, 1991. Now, nine months into the year-long process, EPA scientists responsible for parts of the reassess ment have begun talking openly about new findings that make dioxin seem as bad as, or worse than, EPA used to think. For two decades dioxin has baffled toxicologists. They are used to seeing cancer-causing chemicals that predominantly cause cancer in one organ or another-like asbestos, which chiefly affects the lungs, or benzene, which chiefly affects the bloodforming cells, causing leukemia. But dioxin seems to cause cancer in many organs, raising the general level of cancer in a population without causing a huge increase in any one type of cancer. In addi tion, dioxin causes certain toxic effects in one spe cies and other effects in another species. Likewise, dioxin at low doses causes one kind of illness, and at higher doses it causes different illnesses. Only recently have EPA scientists concluded that this puzzling pattern occurs because dioxin acts like an "environmental hormone." Hormones are potent natural chemicals that send messages via the blood stream, turning on and off chemical switches throughout the body, creating an array of effects in different organs. Dioxin behaves this way. Hor mones are present in the body in tiny amounts, yet they can trigger huge changes in various bodily systems. For example, it is hormones that trigger the different stages of growth in a fetus, and that cause young humans to go through puberty. New Inform ation EPA chief William Reilly was right-there is new information about dioxin. But it won't be reas suring to the paper industry. On the contrary, two studies of workers exposed to dioxin, published during the past year, have shown unmistakable in creases in cancers of several types. A study of 5172 American workers revealed a cancer rate 46% above the norm.1 Likewise, a study of 1583 Ger man workers revealed a cancer rate 39% above the norm; among German workers 20 years on the job, the rate was 82% above the norm, and among the most heavily exposed Germans workers, the cancer rate was three times the norm.2 Notably, among female German workers, the risk of breast cancer was doubled. Whereas a year ago one might have argued whether dioxin had ever been shown to cause cancer in humans, now such arguments are only voiced by the kind of people who say it still isn't proven that cigarettes cause lung cancer. Linda Bimbaum, one of the scientists conducting EPA's reassessment of dioxin, says these two studies have convinced her that dioxin causes cancer in humans, at least at relatively high exposures. But, she told Science News (January 11, 1992, pgs. 2427.), she has an even greater concern about dioxin: "I'm very concerned that much lower exposure to dioxin may result in adverse health effects that are very subtle and difficult to detect." She was talking about dioxin's impact on the immune system. The immune system is an exceedingly complex network of organs, cells, and chemical secretions (hormones) that react to preserve health in the face of a vast array of hostile microorganisms and toxi cants that our bodies encounter every day. The immune system fights against common colds, influ enza, and the body's own cells that go haywire and start to multiply uncontrollably (a definition of can cer). A degraded immune system leaves the body less able to defend itself against hostile forces in the natural environment. Dioxin attacks the immune system. EPA's dioxin reassessment will "focus much greater attention on toxicological data revealing TCDD's [dioxin's] reproductive, developmental, and immunotoxic effects," says Science News. Imraunotoxic means toxic to the immune system. Fur thermore, "This document [EPA's draft reassess ment ][ will also establish TCDD as the first pollu tant to be regulated on the basis of toxicity observed at the cellular level." This is one reason why the dioxin controversy is being followed so carefully by industry and by en vironmentalists. It promises to set precedents in the C00088 way chem icals are regulated in the future. In the past, chem icals were considered harmless if they caused no "clinical" damage (damage your family doctor might detect). Now, with the dioxin reassess ment, evidence o f chem ical changes inside individual cells is being considered important to a person's w ell being. "So far, studies in m ice suggest that dioxin's immunotoxic punch occurs in extremely low doses and may w ell be more important than cancer in determining dioxin's primary health risk," says Bim baum." To study TCDD's toxicity to the immune sys tem, researchers use m ice, whose immune systems model those o f humans. For example, EPA resear chers have measured how w ell TCDD-treated mice withstand the influenza virus. M ice pre-treated with TCDD readily die after exposure to a quantity o f virus that rarely kills healthy mice. Naturally, it would be. very difficult to detect such effects in people. If people exposed to unusu ally high levels o f dioxin, say from a solid waste in cinerator, had damaged immune system s and conse quently experienced various illnesses, no one might ever suspect dioxin as a cause. People might question whether som e o f dioxin's low -level effects represent real harm to people, but "...few people w ill contend that suppression o f the immune system is not an adverse health effect," Bimbaum told Science News. Unlike hormones, which remain in the body only a few hours, dioxin has a half-life in the body of seven years. At the end o f one half-life, half the initial dioxin remains. What this means is that diox in has, relatively, a very long half-life in the body, unlike the hormones that it mimics, so it stays around to play havoc with the body's chemical sys tems year after year. "Thus one TCDD [dioxin] m olecule can continuously disrupt normal cell physi ology," says Science N ews, citing work by w ellknown dioxin researcher Thomas A G asiewicz at the University o f Rochester (NY ) M edical School. EPA's Bimbaum, and Michael Holsapple, a well-known di oxin researcher at the M edical College o f Virginia, say studies o f humans at Tim es Beach, Missouri, and o f Vietnam veterans, were essentially bungled. Holsapple says, "If I were to take m ice and ask the same [research] questions that are routinely asked o f the populations o f lim e s Beach or in the Ranch Hand study [o f Vietnam vets exposed to dioxincontaminated herbicide], I would com e up w ith a very nebulous picture [o f dioxin's immunotoxicity]," says Holsapple. "But when w e ask different ques tions [in m ice], w e can certainly show very strong effects on the immune response," he says. Is there a threshold for dioxin's damage to the human body? Is there a level o f dioxin below which no effects can be observed? George Lucier o f the National Institute o f Environmental Health Sciences in Research Triangle, North Carolina, has been asking this question in his laboratory. H is data show no evidence o f any threshold. "My data might not prove that a threshold doesn't exist," he told Science N ews, "but there's also no evidence o f any thresholds." In other words, any amount o f dioxin does som e damage, according to Lucier's findings. This means the only safe amount is zero. This conclusion is not what the paper industry wanted to hear when its executives urged W illiam R eilly to initiate EPA's dioxin reassessment. A s the reassessment reaches its draft stages early this sum mer, w e'll have new measures o f the potency not only o f dioxin, but also o f industry's m uscle in a contest with' unwelcome scientific conclusions. For all o f us, much is riding on the outcome. 1 Marilyn Fingerhut and others, "Cancer Mortality in Workers Exposed to 2^3,7,8-tetrachlorodibenzo-pdioxin," N ew England Journal o f M edicine V ol. 324 (1991), pgs. 212-218. * A Manz and others, "Cancer Mortality Among Workers in Chemical Plant Contaminated W ith D i oxin," The Lancet Vol. 338 (October 19, 1991), pgs. 959-964. 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