Screening for Estrogen-mimicking Chemicals: An Assessment of the E-screen and Its Implications by Edmond Toy B.A.S. Civil Engineering and Values, Technology, Science, and Society Stanford University, 1993 Submitted to the Department of Civiland Environmental Engineering in Partial Fulfillment of the Requirements for the Degrees of Master of Science in Technology and Policy and Master of Science in Civil and Environmental Engineering at the Massachusetts Institute of Technology September 1995 © 1995 Massachusetts Institute of Technology. All rights reserved. Signature of Author: Department of Civil and Enviromental Engineering August 11, 1995 r'o / I' i /E Certified by: David H. Marks, Ph.D. James Mason Crafts Professor of Civil and Environmental Engineering Director, Program in Environmental Engineering Education and Research Thesis Supervisor A/ Certified by: Richard de Neufville, Ph.D. Professor of Civil and Environmental Engineering Chairman, Technology and Policy Program Accepted by: / 1- ! J'dseph M. Sussman, Ph.D. Chairman, Departmental Committee on Graduate Studies ;;ASSACHUS'T S INSTIlU'rE OF TECHNOLOGY Barker Eng OCT 25 1995 Screening for Estrogen-mimicking Chemicals: An Assessment of the E-screen and Its Implications by Edmond Toy Submitted to the Department of Civil and Environmental Engineering on August 11, 1995 in Partial Fulfillment of the Requirements for the Degrees of Master of Science in Technology and Policy and Master of Science in Civil and Environmental Engineering There is a growing concern that chemicals in the environment may be affecting the endocrine systems of wildlife and humans. Some scientists believe that these endocrine disrupting chemicals are responsible for a wide variety of cancer and noncancer effects. Declines in the reproductive success of wildlife have been observed. In humans, declines in sperm quality and increased incidence of breast cancer and cancers of the male and female reproductive tract may be caused by exposure to endocrine disruptors from the time of fetal development through to adulthood. The effects are difficult to detect and not routinely examined by current chemical testing technologies and strategies. This study examines the developmentof short term tests to detect endocrine disruptors. Bioassays that are quick, inexpensive, and reliable may play an important role in screening large numbers of chemicals for their endocrine disrupting characteristics. This research examines one particular test that has often been cited as a potentially valuable testing tool: the E-screen. This test identifies only those endocrine disrupting chemicals that mimic the hormone estrogen. While other hormones and other mechanisms of action are also of concern, a focused examination of the E-screen will provide insight into the general development of screening tests for endocrine disrupting chemicals. This research investigates the factors that are likely to affect how the E-screen will be used and the ways that it can influence government and industry decision making. The scientific basis and the regulatory context of the E-screen are discussed. Insight is gained from interviews with a number of scientists in academia, government, and industry. In addition, a case study is presented of the most widely used short term mutagenicity test for cancer risk assessment, the Ames Test. Scientists and regulators have over two decades of experience with the Ames Test. Although the Ames Test and the E-screen are used to examine different scientific phenomena, the case study provides a framework for an assessment of the E-screen. This assessment finds that the use and implementation of the E-screen will be affected by the level of public and political concern for endocrine disrupting chemicals, the predictive power of the test, the existence of a testing infrastructure (complementary tests), and the current regulatory framework. The test can fill several but certainly not all niches. At this point, it is premature to adopt the E-screen as part of a formal testing program. Most interviewed scientists believe that considerable research on both a testing infrastructure and the E-screen itself must still be pursued before the E-screen can be used as a basis for government and industry decisionmaking. To facilitate this research, it is recommended that the test should be more widely disseminated; guidelines for its use should be developed; validation studies should be performed by scientists in academia, government, and industry; and validation studies should attempt to find the classes of chemicals for which the E-screen is most predictive. Thesis Supervisor: David H. Marks, Ph.D. Title: James Mason Crafts Professor of Civil and Environmental Engineering Director, Program in Environmental Engineering Education and Research Acknowledgments The completion of a thesis typically marks the academic capstone of graduate school. It is difficult for me, however, to think of a suitable capstone for my two years at MIT when I consider the new things I've learned, the people I've met, and the truly incredible experiences I've had. These will surely not end with this thesis. So while I have many people to thank for helping me in this research, my thanks are certainly for much more than what you hold in your hands. For encouraging me to sail through many uncharted territories, I must thank David Marks. He was always willing to let me do some exploring on my own and also gave me a pull when I needed it. The personal attention that Professor Ana Soto gave to my questions are much appreciated. I must also thank my parents, who deserve more than can be expressed here. They have supported a son who has done things a little differently. I also thank my sister Lily for her encouragement. As for my friends at MIT, they have made graduate schoola surprisingly pleasant way to spend two years. My experience here would have been less rewarding without Kid Kelly, Jonathan Kleinman, Mort Webster, Narasimha Rao, Alice Yates, Nick Gertler, Alice Caponiti, Mark Stoughton, Tyson Browning, Gail Hickey, Rene Smith, Gooseberry'sand TPP hockey. Dale Fried deserves a hearty thanks for his encouragement. Special thanks to Joe Bambenek for the little things that matter and for his lessons in spontaneity. Much credit must be given to the other members of the August Club, Andrew Green and Shanthi Muthiah; I cannot imagine how things would have turned out without them. And to my constant companionsthis past year-Andrew Green and Erin O'Neill-I cannot express what wonderful friends you have been. Many roads must still be traveled. Table of Contents List of Tables and Figures . ..................................................................... 9 A bbreviations ................... .............................................................................................. 1 1 Chapter One: Introduction ............................................. 13 Warning signs and concerns...............................................................................13 The role of screening tests..................................................................................16 Research methods................................................................................................ 17 Chapter Two: Endocrine Disruptors in the Environment ............................. 21 Endocrine disruption............................................................................................21 Evidence of effects................................................................................................25 Chapter Three: An In Vitro Test for Estrogen-mimicking Chemicals: The E-screen........................................... 31 Identification of estrogen-mimicking chemicals. .............................. 32 The E-screen ................................................................................................ 33 Basis and methodology..............................................................................34 Early results ................................................................................................35 Problematic issues......................................................................................40 Conclusions............................................................................................................ 42 Chapter Four: Cancer Risk Assessment and the Ames Test .............................43 Cancer: the dread disease...................................................................................44 Development of the Ames Test ........................................................... 49 The need for short term tests............................................ 50 The Ames Test ............................................ 51 Early Results............................................ 52 Maturation of the Ames Test ............................................. 55 The Ames Test in the regulatory arena...........................................................58 Risk assessment guidelines .......................................................................58 OSHA risk assessment guidelines..................................................60 EPA cancer risk assessment guidelines. ............................. 61 Environmental statutes and regulations ............................................ 62 FIFRA ..................................................................................................63 TSCA ........ .............................................................................................66