ENVIRONMENTAL "HORMONES" Author: Mike Kamrin, MSU Editor: Jeff Jenkins, OSU Reviewers: Art Craigmill, UCD Terry Miller, OSU Don Rutz, Cornell A Pesticide Information Project of Cooperative Extension Offices at Cornell University, Michigan State University, Oregon State University, and University of California at Davis. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program. ***** During the past year, numerous newspaper and magazine articles have suggested that humans may be at risk because small amounts of some well-known environmental contaminants, such as dioxins, PCBs and DDT, can affect hormone levels. Hormones are produced by the endocrine system as regulators of biological function in target organs. Because hormones play a critical role in early development, toxicological effects on the endocrine system often have impacts on the reproductive system. The term endocrine disruptors is used to describe chemicals than can mimic hormones and may either enhance or counteract their effects. It has been suggested that these hormone changes can, in turn, lead to a variety of health problems including cancer, decreased fertility, and abnormalities in newborns. Of special interest are those chemicals that mimic the female hormone estrogen which is thought to promote breast cancer. Publicity about these possible effects is being used to support demands for tighter emission controls and for drastic changes in the use of industrial chemicals and pesticides. One dramatic example is the proposal to phase out the chemical industry's use of chlorine as a raw material. Evidence provided to support these claims of human and wildlife harm is largely from laboratory studies in which large doses are fed to test animals, usually rats or mice, and field studies of wildlife species that have been exposed to the chemicals mentioned above. In laboratory studies, high doses are required to give weak hormone activity. These doses are not likely to be encountered in the environment. In field studies, toxicity caused by endocrine disruption has been associated with the presence of certain pollutants. Findings from such studies include: reproductive disruption in starfish due to PCBs, bird eggshell thinning due to DDT, reproductive failure in mink, small penises in alligators due to DDT and dicofol. In addition, a variety of reproductive problems in many other species are claimed to be associated with environmental contamination although the specific causative agents have not been determined. One recent discovery that complicates the situtation is that there are many naturally occurring "phytoestrogens", or chemicals of plant origin that exhibit weak estrogenic properties. While it is likely that some of the effects noted are due to the chemicals of concern, these problems have occurred when contamination levels were high: e.g., the alligator problems resulted from a spill directly into the lake in which the alligators lived. In addition, many of these effects have been reversed as contaminant levels decreased. For example, bald eagle populations have increased dramatically in recent years. Cormorants, nearly wiped out in the Great Lakes region, are now at such high population levels in this area that some consider these birds as nuisances. Many of the detrimental effects cited by some authors are known to have other causes, such as infectious disease or changes in the environment, such as those resulting from the introduction of exotic species or habitat destruction. Some human studies are cited to support the idea that environmental contaminants are interfering with hormones and causing reproductive effects. Actually only one epidemiological study is commonly mentioned in this regard, a study of the offspring of Michigan fisheaters that reported subtle changes in behavior and a small reduction in head size at birth. This study has not been reproduced elsewhere and has been the subject of much criticism. In addition, the authors of the study believe that the contamination levels are so much lower than at the time the exposure occurred almost fifteen years ago that they would be unlikely to detect any effects if they repeated the work. Additionally, epidemiological studies suggest that women with breast cancer have higher levels of PCBs and/or DDT in their bodies. However, more recent studies show no differences in levels between women who have breast cancer and those who don't. Proponents of the idea that environmental contaminants are affecting hormones also point to the reports of large decreases in sperm counts in human populations during the past 40 years. However, a recent re-evaluation of the data used in this study shows that since 1970 sperm counts have increased slightly. They also point to laboratory studies on animals indicating that dioxins can have reproductive effects. However, many other factors could account for these effects, such as increases in some types of sexually transmitted diseases, increased use of many drugs, etc. In addition, the data used to estimate the magnitude and time course of these sperm level changes has been challenged. The suggestion that such large changes have occurred and that they are associated with these environmental contaminants is speculative at this time. Thus, those who believe that environmental contaminants are causing a variety of hormone-mediated effects in humans base their conclusions on new and old studies of wildlife and human populations. Much of this research was conducted when environmental levels were much higher (at least in certain locations) and may have involved especially sensitive types of animals. It has not been demonstrated that any of these effects in wildlife are currently occurring except in "hot spots" where levels remain high. These "hot spots" are results of previous contamination and are not likely to be significantly affected by increased stringency of emission standards. With respect to humans, there are no convincing studies that show that any adverse hormone-mediated effects are occurring. Epidemiological evidence does not support such a link, although isolated studies may be interpreted that way. The suggestions that many human reproductive changes are a result of environmental contaminants are not based on a significant body of scientific findings. Because of the many claims that have been made and the fact that some hormonal effects are seen at high exposures, scientists continue to expand their efforts to understand how these environmental contaminants produce these effects. In addition, they are looking at other possible causes of these problems. It may soon be possible to determine the most likely causes for these effects and take the appropriate steps to reduce these risks, both in wildlife and in human populations. Selected citations/additional information Colborn, T., F.S. vom Saal and A.M. Soto. 1993. Developmental effects of endocrine-disrupting chemicals in wildlife and humans. Environmental Health Perspectives 101(5):378-384. Davis, D.L., H.L. Bradlow, M. Wolff, T. Woodruff, D.G. Hoel and H. Anton-Culver. 1993. Medical hypothesis: xenoestrogens as preventable causes of breast cancer. Environmental Health Perspectives 101(5):372-377. Felsot, A. 1994. Pesticides, estrogen activity and breast cancer: new cause for regulatory concern? Agrichem. Environ. News 97:8-10. Hileman, B. 1992. Hormone mimics may harm human development. Chem. Eng. News, November 16:5-6. Hileman, B. 1993. Concerns broaden over chlorine and chlorinated hydrocarbons. Chem. Eng. News, April 19:11-20. Krieger, N., M.S. Wolff, R.A. Hiatt, M. Rivera, J. Vogelman and N. Orentreich. 1994. Breast cancer and serum organochlorines: a perspective study among white, black and Asian women. Journal National Cancer Institute 86(8):589-599. MacMahon, B. 1994. Pesticide residues and breast cancer? (Editorial). J. National Cancer Institute 86(8):572-573. Raloff, J. 1994. The gender benders, are environmental "hormones" emasculating wildlife? Science News 145:24-27. Stone, R. 1994. Environmental estrogens stir debate (News & Comment) Science 265:308-310. Wolff, M., P.G. Toniolo, E. Lee, M. Rivera and N. Dubin, 1993. Blood levels of organochlorine residues and risk of breast cancer. Journal National Cancer Institute 85:648-652.