We are sending you background information about a serious environmental and public health problem--endocrine disruptors-- which will be widely discussed in the media during the coming days. Because of your important role in public health, the environment and sustainable agriculture, we thought you might want to be briefed prior to the media attention which will be devoted to this problem. The ensuing debate will probably reprise the contentiousness of the release of "Silent Spring" since it will threaten industrial production of many chemicals currently in wide spread use.
The following information outlines the problem, defines 'endocrine' and 'hormone', explains endocrine disruption processes and sources of contamination. Finally, it offers some options for action. Please forward this on to anyone you think might be interested in this issue.
Scientists are certain that a number of synthetic chemicals act like hormones (especially estrogens) and interact with hormone systems. Scientists have known for years that some of these chemicals are able to affect animals in subtle ways, as Rachel Carson so eloquently described. Scientists also agree that the magnitude of the problem (including human exposure) is uncertain. The puzzle is still being pieced together.
Studies over several years and recent reports of those studies in both the scientific literature and popular media have demonstrated serious wildlife and human health problems caused by endocrine disruptor chemicals. A new book on the subject due out in March, outlines the detective story and the consequences of these chemicals in biological systems. The book, "Our Stolen Future", raises important issues of science, regulation and policy concerning the effects of pesticides, industrial chemicals and other toxic substances on human health and the environment.
The definition of 'endocrine"' is a hormonal pathway characterized by the production of a biologically active substance by a ductless gland; the substance is carried through the bloodstream to initiate a cellular response in a target cell or tissue. (See, the Dictionary of Science and Technology.)
The biologically active substances are hormones that serve as chemical messengers. Hormones are active at very low concentrations and most are specific in what responses they cause in the body. Endocrine systems generally control body growth, organ development, metabolism, and regular body processes such as kidney function, body temperature and calcium regulation.
Endocrine systems are complex, looping cascades that can be disrupted or modulated at many points. Hormones circulate in the body and, even at low levels, are responsible for maintaining balanced conditions, such as blood pressure and reproductive cycling. Different hormones act in complementary ways on the same organs to regulate function. Hormones can also act on each other's synthesis and distribution to affect organ function.
Just about all animals have endocrine systems, and certainly all animals more complicated than a sponge rely on endocrine systems for normal life functions. In wildlife, hormones regulate mating behaviors, migration, fat deposition, hibernation, insect metamorphosis and the shedding of shells by shrimp, crabs and lobster.
Endocrine disruptors are chemicals that interfere with the normal function of hormones and the way hormones control growth, metabolism and body functions. There are different WAYS that chemicals can interfere with or disrupt hormones, and there are different KINDS of chemicals that disrupt. There are more than 70,000 chemicals in commerce, few of which have been tested for carcinogenicity, much less their capacity to disrupt endocrine systems.
Endocrine Disruption - Mimics, Blocks and Triggers
Based on what we do know about the effects of chemicals on endocrine systems, three classes or types of disruptors have been identified. These three classes are mimics, blockers and triggers.
Hormone mimics are chemicals that act like normal hormones in an animal's body. DES, the synthetic estrogen given to women with problem pregnancies, is an excellent example of an estrogen mimic. (Daughters whose mothers were given DES have a range of serious reproductive disorders.) Several other chemicals identified as endocrine disruptors are estrogen mimics.
The second group of disruptors are comprised of hormone blockers that interfere with how naturally occurring hormones function. These chemicals often act by binding to the same protein receptors as the real hormone, but no action is stimulated. The blockers just sit in the way of the natural hormone. The developmental problems of male alligators in Lake Apopka Florida are caused by one of the DDE's blocking the action of testosterone which is one of the class of male hormones called androgens. (DDE is metabolic breakdown product of the pesticide DDT.)
Triggers, the third category of disruptors, include chemicals that interfere by attaching to protein receptors but then trigger an abnormal response or action in the cell - a response that the regular hormone would not cause. The abnormal action may be growth at the wrong time, an alteration of metabolism or synthesis of a different product. The best known of this type of endocrine disruptor is dioxin, and the dioxin-like chemicals. Dioxin acts through a hormone-like process, but neither mimics nor blocks natural hormones.
Research on wildlife populations, especially in the Great Lakes, has demonstrated that endocrine disrupting chemicals profoundly impair animal reproduction and development. Birds with deformed beaks, female birds that nest with females, and male alligators with underdeveloped penises all have high levels of endocrine disruptors, PCB's, dioxins and DDE's, respectively. Laboratory research reveals that fish eggs do not develop when exposed to even low levels of PCB and dioxin. Pregnant rats given ma single low dose of dioxin at a specific time give birth to male rats with a range of reproductive problems.
In humans, scientists are attempting to determine the relation, if any, between low sperm count and exposure to endocrine disruptors, especially the estrogen mimics and androgen blockers. Dioxin and PCB's are known to impair liver function and cause cancer in workers and veterans who were exposed years ago. Children whose mothers used cooking oil contaminated with PCB's and dioxin-like chemicals show a range of developmental problems. Scientists are now investigating possible links between these chemicals and other reproductive and developmental disorders in people.
In both humans and wildlife, these effects are not obvious at the time of exposure, but show up later, or even in the next generation. Daughters of DES exposed women demonstrate this trans-generational aspect of endocrine disrupting chemicals.
Most of these chemicals are synthetic, fat soluble compounds that are pesticides or industrial use compounds. The pesticides include chlorinated organic chemicals such as DDT and kepone. Industrial compounds include PCB's, phenols and dioxins, some of which are manufactured intentionally while others are accidental by-products. The most common characteristics are that they are long lived, remaining in the environment or animals for very long periods, and dissolve in fats, rather than water. As a result, the DDT and dioxin that was released decades ago still contaminates soils, fish and even humans.
All of us carry a certain body burden of these chemicals from past exposures and on-going intake. We get most of these chemicals from animal-based foods, primarily animal fats that have low levels of these chemicals contained in them. Fish from contaminated areas carry higher concentrations in their fat, as may beef, pork or chicken.
A certain amount can also come from drinking water if the water system does not remove any pesticide that has endocrine disrupting properties. Pesticides used at any point in food production can almost always be accumulated and passed on to the eventual consumer -- humans, pets and wildlife.
There is still some uncertainty about the extent to which humans are exposed. In the past six years, a number of chemicals with estrogenic properties have been identified in waste waters, in the leachate from plastic material and in the material used to coat tin cans. (Leaching is the process of separating a soluble substance from a solid by washing or percolation of a fluid through the substance. Coffee made through a drip process is a leachate.)
Estrogenic chemicals have now been identified in commercial products, industrial materials, pesticides, and in the waste stream. It is not clear if the human population is exposed to these chemicals, and what the effect of that exposure is or might be.
The uncertainty is partly due to the fact that we have learned much about the sources and exposures of the endocrine disruptors from studying wildlife and lack the same data from human populations. Bald eagles, mink and cormorants in the Great Lakes were poisoned by eating contaminated fish and small birds that in turn ate other fish that were contaminated by sediment, algae or contaminated water.
The sources of these chemicals are twofold -- pesticides that get into our food supply, and industrial processes that release chemicals that eventually get into our food. Pesticides applied to crops, facilities, animals, animal food and produce can remain on or in the food.
Industrial chemicals can get into our food supply if the emissions or releases are deposited into the environment and picked up by fish, cattle, hogs, poultry, etc. (As noted above, one of the biggest avenues for exposure is animal fat where these toxins accumulate.) Note, the atmospheric emissions from incinerators and other combustion processes are, in fact, the major sources of exposure to dioxins and PCB's.
The great unknown is whether any of the materials used in plastics and other artificial materials can and do get into the food and then into our bodies. Researchers have identified several products found in plastics as estrogenic and at least some of these can "leach" out of the plastics into liquids. There is a potentially large exposure pathway here in the form of all the plastics used in food preparation, storage and cooking. No data are available to show that these chemicals are NOT absorbed into the food. Clearly this is an area where the public should use a great deal of caution.
What can Be Done?
In the coming debate on endocrine disruptors, we will all be faced with the question of what actions to take when we are uncertain of the outcome of future research. But we offer the following options for actions which will reduce exposure to probable endocrine disruptors.
Reduce intake of fats and oils that potentially contain these chemicals. Avoid cooking or microwaving in plastics, and reduce or eliminate storage of food in plastics, especially long term storage and storage of hot foods. Use pesticide-free, organically produced food, where ever possible, and ask for it in our stores. (Check for third party verification to avoid fraud.) Eliminate the use of pesticides in homes and workplaces. Check the origin of fish, beef, and other meats by asking the grocer for the source. We all want to eat food from uncontaminated waters, farms and rangelands.
Finally, it is time to consider the necessity of all industrial processes (particularly incineration) which generate endocrine disruptor chemicals either intentionally or as a by-product. We can and should exercise our right to know, and ask our government officials to prevent this pollution at the source.
Peter L. deFur Center for Environmental Studies Virginia Commonwealth University E-Mail:email@example.com Phone: (804)360-4213
Carolyn Raffensperger the Science and Environmental Health Network E-Mail:firstname.lastname@example.org Phone: (701)763-6287
Known Endocrine Disruptors (according to T. Colborn, 1995):
Herbicides 2,4 D, 2,4,5 T, Alachlor, Amitrole, Atrazine, Metribuzin, Nitrofen, Triflurilan Fungicides Benomyl, Hexachlorobenzene, Mancozeb, Maneb, Metiram -complex Tributyl tin, Zineb, Ziram Insecticides B- HCH, Carbaryl, Chlordane, Dicofol, Dieldrin, DDT and metabolites, Endosulfan, Heptachlor and H-epoxide, Lindane, Methomyl, Methoxychlor, Mirex, Oxychlordane, Parathion, Synthetic pyrethroids, Toxaphene, Transnonachlor Nematocides Aldicarb
Industrial chemicals Cadmium, Dioxin [and furans], Lead, Mercury, PBB's, PCB's, Pentachlorophenol (PCP), Pent- to Nonylphenols, Phthalates, Styrenes
Chemicals screened for estrogenicity using the E-screen protocol (Soto et al., 1995) Positive for estrogenicity:
o,p' DDT, DDD & DDE, Chlordecone, p,p' DDT, Dieldrin, Endosulfan, Alpha endosulfan, Beta endosulfan, Methoxychlor, Toxaphene
(3) Dichlorobenzenes, (3) Trichlorobenzenes, (5) Tetrachlorobenzenes, Hexachlorobenzene; 2,2',3,3',6,'6 4-OH alkyl phenols, Bisphenol -A, 4 OH -biphenyl, t-butylhydroxyanisole, Benzylbutylphthalate, Diphenylphthalate
Prepared: Mar 20 10:12:57 1996 Author: thomasje
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