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Endocrine Disruptors Rachel Carson first highlighted the subtle impacts of chemicals in our environment upon animals with her work on DDT in the 1950’s and 60’s. In recent years studies have begun to bring together the studies showing clearly the impacts of man-made chemicals like PCBs, dioxin and many pesticides act like hormones and interfere with or disrupt normal body functions exacerbating the development of breast cancer, reducing sperm counts, interfering with normal development among other health impacts. One book that describes these impacts is Our Stolen Future: Are We Threatening Our Fertility, Intelligence ad Survival? by Theo Colborn, Diane Dumanoski and John Peterson Myers. The Endocrine System The endocrine system acts as the chemical messenger system for communication throughout our body. The main purpose of the endocrine system is to control and regulate body functions especially growth and development. This is accomplished through hormones, potent, biologically-active chemical messengers that in very small amounts can produce significant biological effects. Hormones are released from the brain, thyroid, ovaries, testes and other endocrine glands and then carries them through the bloodstream to the target cells and organs where they activate and regulate various functions. The system is made up of the pituitary gland which acts as a control center telling the ovaries or the thyroid when to send their signals and how much hormone to send. The pituitary gets its cues from another gland, the hypothalamus, which acts as a thermostat telling the pituitary to increase production, slow down or shut off. These messages travel back and forth continuously to keep all parts of the organism operating as one coordinated being. Hormones also guide the growth of a baby’s nervous system and immune system and "programs" organs and tissues such as the liver, blood, kidneys and muscles so they will function properly. During early development this regulation of growth and development is critical for a child. The thyroid hormone, for example, is essential for normal neurological function and development. Deficiencies of thyroid hormones during fetal development or during early infancy can lead to mental retardation, hearing loss and speech problems. Children with thyroid deficiencies, even those with normal IQ’s, can have language comprehension problems, impaired learning and memory and hyperactive behavior. Chemicals are now being identified that interfere with this critical system. An endocrine disruptor is any substance that can interfere with normal hormone function. Most are synthetic, fat soluble compounds that are either pesticides or industrial use chemicals. The pesticides include chlorinated organic chemicals such as DDT, toxaphene and kepone. Industrial compounds include PCBs, phenol and dioxins. Their most common characteristics include persistence in the environment and in organisms for long periods of time, and solubility in fats, rather that water. There are different ways that these chemicals interfere with or disrupt normal hormone activity. Three classes or types of disruptors have been identified: mimics, blockers, and triggers. Those that "mimic" are chemicals that act like normal hormones in the body. DES, the synthetic estrogen given to women during the 1950’s and 60’s to prevent miscarriages, is a good example of a mimic. Daughters of mothers given DES have an increased risk of a rare cancer and endometriosis. Sons born to mothers given DES have an increase frequency of undescended testes, congenital birth defect, hypospadia, and decreased adult sperm count. A second group of disruptors are hormone "blockers". These interfere with how naturally occurring hormones function. Blockers bind to the same protein receptors as the real hormone, but do not stimulate any action. They just sit in the way of the natural hormone and prevent it from sending its message. An example of a blocker is how DDE (a metabolic breakdown product of DDT) blocked action of testosterone, in male alligators in Lake Apopka, Florida, which led to undersized penises. Testosterone, a male hormone is needed for proper reproductive development in males. "Triggers", the third category of disruptors, include chemicals that interfere by attaching to protein receptors but then trigger an abnormal response in the cell. These triggers cause growth at the wrong time, an alteration of metabolism or synthesis of a different product. The best known triggers are dioxin and dioxin-like chemicals. Dioxin acts through a hormone-like process to initiate entirely new responses.
When taken together, these studies paint a picture that has a "cumulative power that is compelling and urgent." These and other examples of research on wildlife and laboratory animals were highlighted in a historic meeting that took place in July 1991 at the Wingspread Conference Center in Racine, Wisconsin. At this unique meeting, twenty-one of the leading scientific researchers from around the world - specialists from diverse disciplines - came together to share what they knew about the role of hormones in normal development and about the devastating impacts of hormone disrupting chemicals on wildlife, laboratory animals and humans. The scientific evidence presented at this meeting was remarkably consistent and deeply disturbing. The primary conclusion drawn by the participants was that "hormone disruptors threatening the survival of animal populations are also jeopardizing the human future." At the end of the meeting, a paper summarizing the work of the meeting was issued. This group met a second time in November 1995 in Erice, Italy and issued another statement that provides further evidence of the impact of hormone disruptors on neurological and behavioral development.
The devastating effects of endocrine disruptors is also evident in people. Boys born to Taiwanese mothers accidentally contaminated by PCBs have developmental delays, symptoms suggesting attention deficit disorder and shortened penises at puberty. These effects were seen even though the mothers’ exposure occurred at least 6 years prior to the pregnancies. As described earlier, daughters born to mothers who took DES during pregnancy have a greatly increased risk of developing a rare vaginal cancer, having miscarriages and developing endometriosis. Sons are more likely to have undescended testes, hypospadia and lower sperm count. Mothers who frequently ate Great lakes fish while growing up gave birth to children with reduced crania at birth and continuing developmental problems including motoneural deficits. Children born to mothers carrying background levels of contamination in the Netherlands show behavioral and learning impairment and have weakened immune systems. Children born to Inuit mothers from the Canadian Arctic have even greater immune system problems and suffer from increased frequency of inner ear infections. Scientists are also attempting to understand why sperm counts worldwide have dropped by 50% in the past 20 years. Exposure to endocrine disruptors is suspected. The health problems caused by exposure to hormone disrupting chemicals are clearly defined in Our Stolen Future. While many of these chemicals may cause cancer, it now seems clear that exposure to these chemicals poses an additional, perhaps even more devastating risk – the subtle transgenerational effects on growth and development. "Hormone disrupting chemicals are not classical poisons or typical carcinogens. They play by different rules." It’s also clear that as scientists continue to look at the reproductive and developmental effects of these chemicals, they continue to find significant, often permanent, effects at remarkably low doses. This research on endocrine disruptors provides powerful new evidence that may explain the many increases in health problems that are occurring nationwide -increases such as in hormone related cancers, male and female reproductive disorders, infertility and learning disabilities. The contribution of exposure to endocrine disruptors to the increases in these health problems needs to be established. The effects of endocrine disruptors also provides powerful evidence for why we must stop exposure to chemicals such as dioxins, PCBs, DDT and other chlorinated pesticides and industrial chemicals. PCBs and DDT have already been banned from sale in this country, but PCBs can still be found in virtually every neighborhood transformer and capacitor. And, DDT continues to be manufactured for export to other countries. We need to get involved to get government and industry to remove PCBs from use in this country and to stop the manufacturing of DDT for export and use in other countries. Resources: Our Stolen Future. Theo Colborn, Dianne Dumanoski and John Peterson Myers, Dutton Press, 1996. Endocrine Disruptors, CCHW Fact Pack, 1996, $4.00. "Developmental Effects of Endocrine-Disrupting Chemicals in Wildlife and Humans," Theo Colborn, Frederick S. vom Saal and Ana Soto, Environmental Health Perspectives, October, 1993. Chemically-Induced Alterations in Sexual and Functional Development: The Wildlife/Human Connection," (Proceedings of the Wingspread Conference), ed. By Theo Colborn and Coralie Clement. Advances in Modern Environmental Toxicology, vol. XXI, Dr. Myron Mehlman, series editor. Princeton Scientific Publishing Co. Inc., Princeton, NJ 1992. Statement from the Work Session on Environmental Endocrine Disrupting Chemicals: Neural, Endocrine and Behavioral Effects; Follow-up to "Wingspread" statement, Erice, Sicily, Italy, November, 1995. Rachel’s Environment & Health Weekly, Issues #487, 486, 372, 343, 292, 290, 1996-1997, Published by Environmental Research Foundation, PO Box 5036, Annapolis, MD 21403-7036 (410) 263-1584. Also, see the Following websites: CCHW Center for Health, Environment and Justice Rachel's Environmental Health Weekly
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