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 Members Only > Group Members > The Truth About Endocrine Disruptors
The Truth About Endocrine Disrupting Chemicals
The impact of endocrine disrupting chemicals (EDCs) on people's health has generated great controversy. Industry is up in arms over the issue of whether, in their words, "exposure to small amounts of these chemicals in the environment can interfere with the endocrine system and lead to harmful effects on wildlife or human health." Desperately trying to counter solid scientific data that clearly shows that EDCs do interfere with normal hormone function in both animals and people, with adverse developmental and reproductive effects, industry is on the attack.
Endocrine disrupting chemicals, sometimes called environmental hormones, are man-made chemicals that act like hormones and interfere with the normal function of the body's hormone system. This disruption can lead to reproductive and development problems such as lowered sperm count, birth defects of the reproductive organs and higher risks for breast, prostate and testicular cancer. Sometimes these effects fail to show up until a child reaches puberty or afterward, even though exposure took place in the womb.
Endocrine disrupting chemicals are everywhere in the environment and many consumer products. Although there is no set list, some 70 substances including many common chlorinated substances such as PCBs, dioxin, and the pesticides atrazine, chlordane, DDT, and lindane act as endocrine disruptors. Other probable hormone disruptors include alkylphenols such as nonylphenol and octylphenol, which are industrial additives used in a wide variety of detergents and plastics, and bisphenol-A, found in dental sealants and in the lining of some food cans. A 1997 study at the University of Missouri showed that daily exposure of mice embyros to bisphenol-A produced permanent changes in the endocrine system (see Nagel, 1997 in the resource list.)
Industry has dedicated a significant amount of its time, effort and money to this issue. The Chemical Manufacturers Association (CMA), the target of CCHW's Convention ‘97 Action (see Organizing Toolbox), has published a booklet distributed widely to the media called simply "The Environmental Endocrine Issue." The purpose of this booklet is to set the record straight about the "allegations...related to declines in sperm count; increases in breast, prostate and testicular cancer; developmental effects on children; and reproductive effects in wildlife."
Some of the arguments laid out in the CMA booklet include that these effects occur only at high doses, not at the low doses that people and most wildlife are exposed to; that some of these chemicals are no longer manufactured or sold in the U.S. (DDT, PCBs and some pesticides - aldrin, dieldrin, heptachlor, kepone); and that we really don't know what substances are hormone disruptors, that more studies and "good science" are needed.
The Chemical Industry Institute of Toxicology (CIIT), a research lab funded by nearly 40 major chemical companies and closely aligned with CMA, has begun a special research project called "The Endocrine Mystery" that asks the same questions raised in the CMA booklet. It concludes that "the assertion that widespread exposure to low levels of environmental chemicals has contributed to the incidence of breast cancer and other hormone-related disease is only a hypothesis. The available data are not sufficient to clearly confirm or refute it. The difficult work of investigating this mystery is just beginning."
The strategy illustrated by such statements is consistent with past industry approaches. They argue that we cannot be sure, that the data is insufficient, that we need more research, and most importantly that we must use "good science" to clearly answer the questions. What they don't say is that all this will take decades and that we should do nothing until we are "sure."
Industry is never satisfied with what we know. This dissatisfaction is not based on the quality of our knowledge. In fact, most of the current research on hormone disrupting chemicals is as "good" as it gets. Nor is it based on the existence of major gaps in our knowledge. While you can always stand to know more, we know enough to act in a protective way. Industry's attitude is based on the desire to prevent government interference in how they do business. Their strategy is to delay - delay government from taking any actions that would regulate or control the use or distribution of hormone disruptors. If government acts on what we know, if they take action to prevent exposures to EDCs, the impact on industry would be substantial. And if history has taught us anything, industry will fight to the death against anything that impacts on business as usual and their profits.
Another issue that industry has pushed is that just because a chemical mimics endocrine behavior doesn't mean that an adverse effect has occurred. The problem with this argument is that many of the developmental effects of EDCs often do not show up until steroid levels increase at the onset of puberty. So, it is extremely difficult to associate these latent effects with specific developmental exposures. The only way to "prove" if exposure to hormone disrupting chemicals caused adverse health effects would be to allow our children to be exposed to these chemicals and then follow these children for their lifetime - 60 to 70 years - to determine whether the incidence of prostate cancer, or other disease, differed as a function of exposure. There are other problems in "proving" this relationship, including the lack of data on national norms, the inconsistent reporting and characterization of adverse developmental effects, and the low sensitivity of epidemiological studies. More importantly, the burden of proof should not be on the public to show that adverse effects are occurring, but rather on the industry to show that their chemicals do not cause adverse health effects.
Industry arguments were further fueled this past August when researchers at Tulane University withdrew a research paper that was published a year earlier in the magazine Science. The original paper showed that exposure to combinations of hormone disruptors produced effects that were many times - 1,600 times - greater than the effect of exposure to single chemicals alone. This work marked one of the first times that synergistic effects had been found to be so dramatic and the work was hailed as having significant public health implications. The results were especially credible because the lead author, John McLachlan, is a distinguished researcher, prominent in the scientific community.
What McLachlan and others found was that these results were not reproducible. Other attempts to replicate these synergistic effects had failed. So McLachlan thought it best to retract the study, primarily because so many people "on their own put great weight on this report." It is very rare for a researcher to withdraw a study. One of the foundations of the scientific process is for other researchers to duplicate a study. If testing and retesting do not bring a consensus, then the original report is usually quickly forgotten.
An editorial in the scientific journal Environmental Health Perspectives commended McLachlan and his colleagues, stating that they deserve significant credit for taking this step and that they have "served science appropriately and well." But the editorial also states that the withdrawal does not mean that there is no evidence for synergy. Several studies reported by a number of researchers and laboratories, including McLachlan's, have found synergy among contaminants, although not with the marked effects shown in the withdrawn study.
Industry has argued that the withdrawn study was the "scientific basis for regulatory concern over endocrine disrupting chemicals" and that, based on the retraction, there was no longer a need to test chemicals for hormone activity or to issue regulations. But in a letter to the Washington Times, Lynn Goldman, Assistant Administrator for EPA, in charge of the agency's endocrine program, was clear was about the impact of the withdrawal. The retraction "does not overturn the substantial scientific literature on either endocrine disruptor or synergistic effects. Scientific literature clearly and repeatedly documents endocrine effects in humans, laboratory animals and wildlife. The strongest evidence has been generated for a few pesticides and for industrial chemicals with well known public health and environmental problems (e.g. DDT, PCBs, dioxin)."
The industry arguments are predictable and as usual ring hollow. The industry spin doctors are good at defining issues in ways that fit their agenda (and arguments) but rarely follow the facts. For example, one of their main points is that the adverse health effects that result from exposure to hormone disrupting chemicals only occur at high levels used in experimental studies in animals and not at levels that people are generally exposed to. This is not true and there is plenty of data to back it up.
Researchers such as Louis Guillette, at the University of Florida, Ana Soto at Tufts University in Massachusetts, and Frederick vom Saal at the University of Missouri have all found adverse reproductive or developmental effects in animals or wildlife exposed to extremely low levels of EDCs. According to the EPA, people are being currently being exposed to similar levels of hormone disrupting chemicals. Many of these studies are summarized in the book, Our Stolen Future, by Theo Colborn, Diane Dumanoski, and J.P. Myers. Many scientific papers describing these studies are also described in EPA's draft reassessment document for dioxin.
Dr. vom Saal described the importance of low level effects in discussing some of his research in a workshop at CCHW's Convention ‘97. "Steroid hormones regulate the development of the reproductive system. The issue is not whether males have just testosterone and no estradiol or that females have just estradiol and no testosterone, rather it is the relative amounts of these hormones in the fetus that determines the course of development of the reproductive system, such that the fetus can end up with male or female accessory reproductive organs.
"The difference between becoming a female and a male is the difference between changing, not by very much, by parts per trillion to parts per billion, levels of the hormones estradiol and testosterone. These changes result in your having the appearance of a male or a female. We are not talking about necessarily very subtle outcomes. A little difference of hormone determines whether the embryonic tissue becomes a vagina or a prostate...You can image what happens if external chemicals get into the fetus' body and act like hormones; they can change the course of development of these tissues."
While scientists do not yet know for certain how dangerous low level environmental exposures to EDCs might be, we certainly know enough to act to protect our children and our future. We should follow the lead of Theo Colborn and others who are urging government to take a precautionary approach, maintaining that persistent hormone disrupting chemicals should be phased out and the burden of proof (of harmlessness) shifted to industry. If human beings and animals are vulnerable to the same chemicals, how long must we wait for regulation? How long must we wait for government to protect us?
For Further Reading:
"Endocrine Disruptors," Stephen Lester, and Patty Lovera, Everyone's Backyard, Vol 14, No 3, pp 6-10, Fall 1996. This paper is included in CCHW's Endocrine Disruptors Fact Pack. Available from CCHW for $4.00 plus shipping and handling.
Our Stolen Future, Theo Colborn, Dianne Dumanoski and John Peterson Myers, Dutton Press, 1996.
"Getting to the Truth About What We Know and Don't Know About the Hazards Posed by Endocrine Disrupting Chemicals," Adapted from a speech delivered by Fredrick vom Saal, PhD at the National Coalition Against the Misuse of Pesticide's Fifteenth Pesticide Forum, March 14- 17, 1997. Published in Pesticides and You, Vol 17, No. 1-2, Winter, 1997. Available from NCAMP, 701 E Street, SE, Suite 200, Washington, DC 20003 (202) 543-5450.
"Relative Binding Affinity - Serum Modified Access (RBA-SMA) Assay Predicts the Relative in Vivo Bioactivity of the Xenoestrogens Bisphenol A and Octylphenol," Susan C. Nagel, Frederick S. vom Saal, Kitrina A. Thayer, Minati G. Dhar, Michael Boechler and Wade V. Welshons, Environmental Health Perspectives, Vol. 105, No 1, pp 70-76, January 1997.
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