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ISSUES IN RISK ASSESSMENT

Committee on Risk Assessment Methodology

Board on Environmental Studies and Toxicology

Commission on Life Sciences

National Research Council

NATIONAL ACADEMY PRESS
Washington, DC
1993



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About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. ISSUES Washington, DC 1993 National Research Council Commission on Life Sciences ASSESSMENT NATIONAL ACADEMY PRESS ISSUES IN RISK Committee on Risk Assessment Methodology Board on Environmental Studies and Toxicology i

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ii original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. NATIONAL ACADEMY PRESS 2101 Constitution Ave., NW Washington, DC 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sci- ences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, non-profit, self-perpetuating society of distin- guished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the fed- eral government on scientific and technical matters. Dr. Frank Press is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sci- ences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy mat- ters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal govern- ment and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of further- ing knowledge and advising the federal government. Functioning in accordance with general poli- cies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is adminis- tered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council. The project was supported by the U.S. Environmental Protection Agency under Cooperative Agreement #CR-815682, the American Petroleum Institute, and the American Industrial Health Council. Funds were also contributed by the National Institute for Occupational Safety and Health and the U.S. Army Biomedical Research and Development Laboratory. Library of Congress Catalog Card No. 92-61838 International Standard Book Number 0-309-04786-2 Additional copies of this report are available from the National Academy Press, 2101 Constitution Avenue, NW, Washington, DC 20418. B-023 Copyright 1993 by the National Academy of Sciences. All rights reserved. Printed in the United States of America First Printing, January 1993 Second Printing, March 1993 Third Printing, March 1995 Fourth Printing, September 1997

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iii original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Committee on Risk Assessment Methodology BERNARD D. GOLDSTEIN (Chairman), Environmental and Occupational Health Sciences Institute, Robert Wood Johnson Medical School, and Rutgers University, Piscataway, NJ DONALD R. MATTISON (Vice-Chairman), University of Pittsburgh, Graduate School of Public Health, Pittsburgh JOHN C. BAILAR, III, McGill University School of Medicine, Montreal PAUL T. BAILEY, Mobil Oil Corporation, Princeton LAWRENCE W. BARNTHOUSE, Oak Ridge National Laboratory, Oak Ridge, TN KENNY S. CRUMP, Clement Associates, Inc., Ruston, LA JOHN DOULL, University of Kansas Medical Center, Kansas City MICHAEL A. GALLO, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway RICHARD A. GRIESEMER, National Institute of Environmental Health Sciences, National Toxicology Program, Research Triangle Park, NC WILLIAM E. HALPERIN, National Institute for Occupational Safety and Health, Cincinnati ROGENE HENDERSON, Lovelace Biomedical and Environmental Research Institute, Albuquerque BRIAN P. LEADERER, John B. Pierce Foundation, Yale University School of Medicine, New Haven, CT ALAN W. MAKI, Exxon Corporation, Houston FRANKLIN E. MIRER, United Auto Workers, Detroit DANIEL W. NEBERT, Institute of Environmental Health, University of Cincinnati Medical Center, The Kettering Laboratory, Cincinnati D. WARNER NORTH, Decision Focus, Inc., Mountain View, CA RICHARD H. REITZ, The Dow Chemical Company, Midland, MI

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iv original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Staff RICHARD D. THOMAS, Principal Staff Scientist GAIL CHARNLEY, Project Director KATHLEEN R. STRATTON, Project Director (until March 1992) MARVIN A. SCHNEIDERMAN, Senior Staff Scientist ANNE M. SPRAGUE, Information Specialist IAN C.T. NISBET, Technical Adviser DANIEL KREWSKI, Technical Adviser LINDA V. LEONARD, Senior Project Assistant RUTH DANOFF, Project Assistant JOYCE WALZ, Project Assistant Sponsors U.S. Environmental Protection Agency American Petroleum Institute American Industrial Health Council National Institute for Occupational Safety and Health U.S. Army Biomedical Research and Development Laboratory

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v original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Committee on Risk Assessment Methodology Federal Liaison Group WILLIAM H. FARLAND (Co-chair), U.S. Environmental Protection Agency, Washington, DC ROBERT SCHEUPLEIN (Co-chair), U.S. Food and Drug Administration, Washington, DC DEBORAH BARSOTTI, Agency for Toxic Substances and Disease Registry, Atlanta, GA JAMES BEALL, U.S. Department of Energy, Washington, DC JAMES BILSTAD, U.S. Food and Drug Administration, Rockville, MD WILLIAM CIBULAS, Agency for Toxic Substances and Disease Registry, Atlanta, GA MURRAY S. COHN, Consumer Product Safety Commission, Bethesda, MD JOSEPH COTRUVO, U.S. Environmental Protection Agency, Washington, DC GERALD A. FAICH, U.S. Food and Drug Administration, Rockville, MD HENRY S. GARDNER, U.S. Army Biomedical Research Development Laboratory, Frederick, MD HERMAN GIBB, U.S. Environmental Protection Agency, Washington, DC WALTER H. GLINSMANN, U.S. Food and Drug Administration, Washington, DC BRYAN D. HARDIN, National Institute for Occupational Safety and Health, Cincinnati RONALD W. HART, National Center for Toxicological Research, Jefferson, AR RICHARD N. HILL, U.S. Environmental Protection Agency, Washington, DC

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vi original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. KAREN HOGAN, U.S. Environmental Protection Agency, Washington, DC PETER INFANTE, U.S. Department of Labor, Washington, DC MICHAEL A. LIDSKY, U.S. Department of Agriculture, Hyattsville, MD RONALD J. LORENTZEN, U.S. Food and Drug Administration, Rockville, MD JOHN MARTONIK, U.S. Department of Agriculture, Washington, DC GERALD F. MEYER, U.S. Food and Drug Administration, Rockville, MD EDWARD OHANIAN, U.S. Environmental Protection Agency, Washington, DC RICHARD ORR, U.S. Department of Agriculture, Hyattsville, MD RICHARD PARRY, JR., U.S. Department of Agriculture, Beltsville, MD DOROTHY PATTON, U.S. Environmental Protection Agency, Washington, DC PETER PREUSS, U.S. Environmental Protection Agency, Washington, DC LORENZ R. RHOMBERG, U.S. Environmental Protection Agency, Washington, DC MATTHEW H. ROYER, U.S. Department of Agriculture, Hyattsville, MD LILLY SANATHAN, U.S. Food and Drug Administration, Rockville, MD LINDA SCHIEROW, U.S. Library of Congress, Washington, DC JENNIFER SEED, U.S. Environmental Protection Agency, Washington, DC MICHAEL SLIMAK, U.S. Environmental Protection Agency, Washington, DC JANET A. SPRINGER, U.S. Environmental Protection Agency, Washington, DC BRUCE V. STADEL, U.S. Food and Drug Administration, Rockville, MD LESLIE T. STAYNER, National Institute for Occupational Safety and Health, Cincinnati ROBERT J. TEMPLE, U.S. Food and Drug Administration, Rockville, MD ANGELO TURTURRO, National Center for Toxicological Research, Jefferson, AR MICHAEL T. WERNER, U.S. Department of Agriculture, Hyattsville, MD MAURICE ZEEMAN, U.S. Environmental Protection Agency, Washington, DC

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vii original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Board on Environmental Studies and Toxicology PAUL G. RISSER (Chair), University of New Mexico, Albuquerque FREDERICK R. ANDERSON, Cadwalader, Wickersham & Taft, Washington, DC JOHN C. BAILAR, III, McGill University School of Medicine, Montreal GARRY D. BREWER, University of Michigan, Ann Arbor JOHN CAIRNS, JR., Virginia Polytechnic Institute and State University, Blacksburg EDWIN H. CLARK, Department of Natural Resources and Environmental Control, State of Delaware, Dover JOHN L. EMMERSON, Lilly Research Laboratories, Greenfield, IN ROBERT C. FORNEY, Unionville, PA ALFRED G. KNUDSON, Fox Chase Cancer Center, Philadelphia KAI LEE, Williams College, Williamstown, MA GENE E. LIKENS, The New York Botanical Garden, Millbrook JANE LUBCHENCO, Oregon State University, Corvallis DONALD MATTISON, University of Pittsburgh, Pittsburgh HAROLD A. MOONEY. Stanford University, Stanford, CA GORDON ORIANS, University of Washington, Seattle FRANK PARKER, Vanderbilt University, Nashville GEOFFREY PLACE, Hilton Head, SC MARGARET M. SEMINARIO, AFL/CIO, Washington, DC I. GLENN SIPES, University of Arizona, Tucson BAILUS WALKER, JR., University of Oklahoma, Oklahoma City WALTER J. WEBER, JR., University of Michigan, Ann Arbor Staff JAMES J. REISA, Director DAVID J. POLICANSKY, Associate Director and Program Director for Natural Resources and Applied Ecology RICHARD D. THOMAS, Associate Director and Program Director for Human Toxicology and Risk Assessment LEE R. PAULSON, Program Director for Information Systems and Statistics RAYMOND A. WASSEL, Program Director for Environmental Sciences and Engineering

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viii original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Commission on Life Sciences BRUCE M. ALBERTS (Chairman), University of California, San Francisco BRUCE N. AMES, University of California, Berkeley J. MICHAEL BISHOP, Hooper Research Foundation, University of California Medical Center, San Francisco DAVID BOTSTEIN, Stanford University School of Medicine, Stanford MICHAEL T. CLEGG, University of California, Riverside GLENN A. CROSBY, Washington State University, Pullman LEROY E. HOOD, University of Washington, Seattle MARIAN E. KOSHLAND, University of California, Berkeley RICHARD E. LENSKI, University of Oxford STEVEN P. PAKES, Southwestern Medical School at Dallas EMIL A. PFITZER, Hoffmann-La Roche Inc., Nutley, NJ MALCOLM C. PIKE, University of Southern California School of Medicine, Los Angeles THOMAS D. POLLARD, Johns Hopkins Medical School, Baltimore PAUL G. RISSER, University of New Mexico, Albuquerque JOHNATHAN M. SAMET, University of New Mexico School of Medicine, Albuquerque HAROLD M. SCHMECK, JR., Armonk, NY CARLA J. SHATZ, University of California, Berkeley SUSAN S. TAYLOR, University of California at San Diego, La Jolla P. ROY VAGELOS, Merck and Company, Inc., Rahway, NJ TORSTEN N. WIESEL, Rockefeller University, New York Staff ALVIN G. LAZEN, Acting Executive Director

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PREFACE ix original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Preface This volume is the first in a series to be prepared by the Committee on Risk Assessment Methodology (CRAM) in the National Research Council's Board on Environmental Studies and Toxicology. The committee was charged with identifying and investigating important scientific issues in risk assessment. Three issues related to risk assessment are addressed here: use of the maximum tolerated dose (MTD) in animal bioassays for carcinogenicity, the two-state model of carcinogenesis, and a paradigm for ecologic risk assessment. The use of the MTD in animal bioassays has been standard practice in the United States for more than 15 years, and controversy surrounding its use is not new. However, questions continue to be raised about the utility of the data derived from such tests and about the validity of inferences drawn from the data. Stimulated by the information presented in a workshop held on September 6, 1990, and discussions held at later meetings, CRAM has examined the issues related to the MTD. The first report in this volume contains its findings and recommendations on the issues. The workshop included presentations by Eugene McConnell on "Definition and Application of MTD," by Daniel Krewski on "Correction Between the MTD and Measures of Carcinogenic Potency: Implications for Risk Assessment," and by Bruce Ames on ''What Are Bioassays Conducted at the MTD Telling Us?" The program, a workshop summary, and a list of attendees appear as appendixes to the first report in this volume. Dr. Krewski's presentation summarized findings from a review paper with the same title, which was developed specifically for the work

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PREFACE x original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. shop. Invited to discuss the presentations were Edmund Crouch, Kenny Crump, John Emmerson, Reto Engler, Michael Gallo, David Gaylor, Ian Munro, Thomas Starr, James Wilson, and Lauren Zeise. In the second report in this volume, CRAM examines the use of the two- stage model of carcinogenesis, which is based on a paradigm that is thought to reflect the biologic mechanisms underlying carcinogenesis, for human risk assessment. Like the use of the MTD, the use of empirically based mathematical models for evaluating the relationship between dose and response in rodent bioassays and extrapolating from high to low doses is standard. However, questions have been raised about the biologic relevance of such procedures and about the validity of human risk assessments based on the models. This report was based on information presented in a workshop held on November 8, 1990, and discussions held at later meetings. The workshop included presentations by Alfred Knudson on "Biological Factors in Two-Stage Models," by Suresh Moolgavkar on "Two-Stage Clonal Expansion Model of Carcinogenesis," and by Samuel Cohen on "Application of the Two-Stage Model to Animal Data." Invited to discuss those presentations were Carl Barrett, William Farland, Robert Maronpot, Robert Sielken, Todd Thorslund, and James Wilson. The third report in this volume examines the overall process of ecological risk assessment and was stimulated by information presented at a workshop held on February 26-March 1, 1991, and discussions held at later meetings. The workshop included numerous speakers and discussants, whose goals were to survey existing approaches to ecological risk assessment, consider developing a consistent framework for ecological risk assessment, and identify major uncertainties and research needs. The keynote speakers were Terry Yosie, of the American Petroleum Institute; Michael Slimak, deputy director of the Office of Ecological Processes and Effects Research, U.S. Environmental Protection Agency; and Warner North, of Decision Focus, Inc., a member of the committee. Some of the other reports being prepared by CRAM will re-evaluate established practices or principles in light of potential alternatives, and some will address new concepts to advance the science of risk assessment. It is hoped that the series of reports that result from the committee's deliberations will help scientists in regulatory agencies, academe, and industry to find common ground for defining, understanding, and discussing important ideas in the field.

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PREFACE xi original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. The conclusions and recommendations presented herein were arrived at by the committee in executive session. Thus, the scientific interpretations are those of committee members and not necessarily those of other participants in the workshops. The committee's reports were reviewed according to standard NRC practices, and the committee thanks the reviewers for their close attention and useful comments. The workshop summaries in the appendixes were prepared as working papers for the committee by the workshop organizers and participants; they are not NRC reports and have not been subjected to NRC review procedures. The committee thanks the persons who participated in the workshops, especially the speakers, whose presentations provided important information for the consideration of the committee. Special thanks also are given to the members of the federal liaison group, whose names and affiliations are listed in the front of this report. Two task groups of the committee took special responsibility for the workshops and reports. Although the entire committee shares the responsibility for the contents of the reports, the task-group members listed below must be credited for having done the key work of organizing the workshops and preparing their findings and recommendations for review and endorsement by the full committee. No effort of this kind can be accomplished without the hard work and dedication of a talented staff. The committee joins me in thanking the following staff of the Board on Environmental Studies and Toxicology: James Reisa, Richard Thomas, Gail Charnley, Kathleen Stratton, Mary Paxton, Marvin Schneiderman, Anne Sprague, Ruth Danoff, and Linda Leonard. Bernard Goldstein Chairman, CRAM

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About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution.PREFACE Lois Gold Paul T. Bailey Alan W. Maki Ian C.T. Nisbet Daniel Krewski Richard H. Reitz D. Warner North Michael A. Gallo Rogene Henderson Donald R. Mattison Technical Advisers Kenny S. Crump, Chairman, MTD Lawrence W. Barnthouse, Chairman Richard A. Griesemer, Chairman, Two-Stage Ecological Risk Assessment Task Group Members MTD and Two-Stage Model Task Group Members xii

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About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. 3 2 1 CONTENTS PREFACE Background Correlations Scope of Report INTRODUCTION Observed at MTD EXECUTIVE SUMMARY Qualitative Information Quantitative Information Definitions and Background SAYS THAT USE THE MTD Contents MAL BIOASSAYS FOR CARCINOGENICITY CORRELATIONS BETWEEN CARCINOGENIC Relationship Between Toxicity and Carcinogenicity USE OF THE MAXIMUM TOLERATED DOSE IN ANI- ADVANTAGES AND DISADVANTAGES OF BIOAS- POTENCY AND OTHER MEASURES OF TOXICITY xiii 49 43 43 33 24 21 21 18 15 15 1 ix

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CONTENTS xiv original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. 4 OPTIONS CONSIDERED 53 Option 1 53 Option 2 54 Option 3 55 Option 4 57 5 CONCLUSIONS AND RECOMMENDATIONS 61 REFERENCES 67 APPENDIXES 79 A Workshop Summary—Maximum Tolerated Dose: Implica- 79 tions for Risk Assessment B Workshop Organizing Subcommittee 91 C Workshop Federal Liaison Group 93 D Workshop Program 95 E Workshop Attendees 97 F Correlation Between Carcinogenic Potency and the Maxi- 111 mum Tolerated Dose: Implications for Risk Assessment G Informal Search for "Supercarcinogens," 173 THE TWO-STAGE MODEL OF CARCINOGENESIS ISSUES IN RISK ASSESSMENT 187 Introduction 187 Biologic Considerations 188 The Two-Stage Model 190 Applications of the Two-Stage Model to Animal Data 196 Discussion 212 Conclusions and Recommendations 215 REFERENCES 217

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CONTENTS xv original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. APPENDIXES A Workshop Summary—Two-Stage Models of Carcinogenesis 223 B Workshop Program 233 C Workshop Federal Liaison Group 235 D Workshop Attendees 237 E Workshop Organizing Task Group 239 A PARADIGM FOR ECOLOGICAL RISK ASSESSMENT 1 INTRODUCTION 243 2 SCOPE OF ECOLOGICAL RISK ASSESSMENT 247 3 REVISION OF 1983 FRAMEWORK TO INCORPO- 249 RATE ECOLOGICAL RISK ASSESSMENT Components of the 1983 Framework 249 Consistency of Case Studies with the 1983 Framework 251 Integration of Ecological Risk into the 1983 Framework 254 Definition of Framework Components 255 4 KEY SCIENTIFIC PROBLEMS LIMITING APPLICA- 259 TION OF ECOLOGICAL RISK ASSESSMENT Extrapolation Across Scales 259 Quantification of Uncertainty 261 Validation of Predictive Tools 262 Valuation 263 5 CONCLUSIONS 265 6 RECOMMENDATIONS 267

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