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IMPROVING RISK COMMUNICATION Committee on Risk Perception and C ~ . ommun~cat~on Commission on Behavioral and Social Sciences and Education Commission on Physical Sciences, Mathematics, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1989

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National Academy Press 2101 Constitution Avenue N.W. Washington D. C. 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Researeh 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 eompetences 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 Aeademy of Seienees, the National Aeademy of Engineering, and the Institute of Medieine. The study reported here was supported by the Ageney for Toxie Substanees Disease Registry, Allied-Signal, Ameriean Cyanamid Company, Ameriean In- dustrial Health Council, Ameriean Petroleum Institute, Bristol-Myers Com- pany, U.S. Department of Defense, U.S. Department of Energy, Dow Chemieal USA, Eleetrie Power Researeh Institute, U.S. Environmental Proteetion Agency, Exxon Corporation, Hereules Incorporated, ILSI Risk Seienee Institute, Mobil Oil Corporation, Monsanto Company, Motor Vehicle Manufaeturers Assoeiation, and National Scienee Foundation. It also has received support from the National Research Council Fund, a pool of private, discretionary, nonfederal funds that is used to support a program of Academy-initiated studies of national issues in which science and technology figure significantly. The NRC Fund consists of contributions from a consortium of private foundations including the Carnegie Corporation of New York, the Charles E. Culpeper Foundation, the William and Flora Hewlett Foundation, the John D. and Catherine T. MaeArthur Foun- dation, the Andrew W. Mellon Foundation, the Rockefeller Foundation, and the Alfred P. Sloan Foundation; and the Aeademy Industry Program, which seeks annual contributions from companies that are concerned with the health of U.S. science and technology and with public policy issues with technological content. Library of Congress Cataloging-in-Publication Data Improving Risk Communieation / Committee on Risk Perception and Commu- nication, Commission on Physical Sciences, Mathematies, and Resourees, Commission on Behavioral and SoeiaI Seiences and Edueation, Na- tional Research Council. p. cm. Bibliography: p. Includes index. ISBN 0-309-03946-0. ISBN 0-309-03943-6 (pbk.). 1. Risk Communieation. I. National Researeh Council (U.S.). Committee on Risk Perception and Communieation. T10.68.I47 1989 89-9464 363.1-dc20 CIP Copyright A) 1989 by the National Academy of Scienees No part of this book may be reproduced by any mechanical, photographic, or electronic process, or in the form of a phonographic recording, nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use, without written permission from the publisher, except for the purposes of official use by the U.S. government. Printed in the United States of America First Printing, August 1989 Second Printing, January 1990 Third Printing, March 1990 Forth Printing, June 1990 Fifth Printing, July 1994 Sixth Printing, March 1996 Seventh Printing, 1998

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COMMITTEE ON RISE PERCEPTION AND COMMUNICATION JOHN F. AHEARNE, Vice President, Resources for the Euture, Washington, D.C., Chairman ERNESTA BALLARD, Consultant, Seattle, Washington RUTH FADEN, Professor, Department of Health Policy and Management, Johns Hopkins University, Baltimore, Maryland JAMES A. FAY, Professor, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge BARUCH FISCHHOFF, Professor, Department of Engineering and Public Policy and Department of Social and Decision Sciences Carnegie-Mellon University, Pittsburgh, Pennsylvania THOMAS P. GRUMBLY, President, Clean Sites, Inc., Alexandria, Virginia PETER BARTON MUTT, Partner, Covington & Burling, Washington, D.C. BRUCE W. KARRH, Vice President, Safety, Health & Environmental Affairs, E. I. du Pont de Nemours & Co., Wilmington, Delaware D. WARNER NORTH, Principal, Decision Focus, Inc., Los Altos, California; Consulting Professor, Department of Engineering-Economic Systems, and Associate Director, Center for Risk Analysis, Stanford University, Stanford, California JOANN E. RODGERS, Deputy Director of Public Affairs and Director of Media Relations, The Johns Hopkins Medical Institutions, Baltimore, Maryland MILTON RUSSELL, Professor of Economics, University of Tennessee, Knoxville, and Senior Economist, Oak Ridge National Laboratory, Oak Ridge, Tennessee ROBERT SANGEORGE, Vice President for Public Affairs, National Audubon Society, New York HARVEY M. SAPOLSKY, Professor of Public Policy and Organization, Political Science Department, Massachusetts Institute of Technology, Cambridge JURGEN SCHMANDT, Professor, LB] School of Public Affairs, University of Texas, Austin, and Director, Center for Growth Studies, Houston Area Research Center, The Woodlands, Texas MICHAEL SCHUDSON, Chair, Department of Communication, and Professor, Department of Sociology, University of California at San Diego, La JolIa .. 111

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PERCY H. TANNENBAUM, Professor of Public Policy and Director, Survey Research Center, University of California at Berkeley DETLOF VON WINTERFELDT, Director, Risk Communication Laboratory, and Professor, Department of Systems Science, Institute of Safety and Systems Management, University of Southern California, Los Angeles CHRIS WHIPPLE, Technical Manager, Electric Power Research Institute, Palo Alto, California SUSAN D. WILTSHIRE, Senior Associate, OK Associates, Hamilton, Massachusetts Staff ROB COPPOCK NANCY A . C RO WELL LAWRENCE E. MCCRAY PAUL STERN DEBORAH REISCHMAN 1V.

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COMMISSION ON BEHAVIORAL AND SOCIAL SCIENCES AND EDUCATION RoBERT MCC. ADAMS, Secretary, Smithsonian Institution, Washington, D.C., Chairman PHILIP E. CONVERSE, Institute for Social Research, University of Michigan, Ann Arbor ARTHUR S. GOLDBERGER, Department of Economics, University of Wisconsin, Madison BEATRIX A. HAMBURG, Mt. Sinai School of Medicine, New York LEONID HURWICZ, Department of Economics, University of Minnesota, Minneapolis JOSEPH B. KADANE, Department of Statistics, Carnegie Mellon University, Pittsburgh, Pennsylvania EDWARD O. LAUMANN, Department of Sociology, University of Chicago, Chicago, Illinois ALVIN M. LIBERMAN, Haskins Laboratories, New Haven, Connecticut STEWART MACAULAY, School of Law, UniversitY of Wisconsin. Madison ~, ROGER G. NOLL, Department of Economics, Stanford University, Stanford, California SAMUEL PRESTON, Population Studies Center, University of Pennsylvania, Philadelphia FRANKLIN D. RAINES, hazards Freres & Co., New York LAUREN B- ~ A. RESNICK, Learning Research and Development Center, University of Pittsburgh, Pittsburgh, Pennsylvania JOHN M. ROBERTS, Department of Anthropology, University of Pittsburgh, Pittsburgh, Pennsylvania ELEANOR B. SHELDON, New York JEROME E. SINGER, Department of Medical Psychology, Uniformed Services University of the Health Sciences Bethesda, Maryland MARSHALL S. SMITH, School of Education, Stanford University, Stanford, California JOHN A. SWETS, Bolt, Beranek & Newman Laboratories, Inc., Cambridge, Massachusetts SIDNEY VERBA, University Library, Harvard University, Cambridge, Massachusetts P. BRETT HAMMOND, Acting Executive Director v

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COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND RESOURCES NORMAN HACKERMAN, Robert A. Welch Foundation, Houston, Texas, Chairman GEORGE F. CARRIER, Division of Applied Sciences, Harvard University, Cambridge, Massachusetts HERBERT D. DOAN, The Dow Chemical Company (retired), MicIland, Michigan PETER S. EAGLESON, Massachusetts Institute of Technology, Cambridge DEAN E. EASTMAN, IBM T. J. Watson Research Center, Yorktown Heights, New York MARYE ANNE FOX, Department of Chemistry, University of Texas, Austin GERHART FRIEDLANDER, Brookhaven National Laboratory, Upton, New York LAWRENCE W. FUNKHOUSER, Chevron Corporation (retired), Atherton, California PHILLIP A. GRIFFITHS, Duke University, Durham, North Carolina CHRISTOPHER F. MCKEE, Department of Physics, University of California at Berkeley JACK E. OLIVER, Cornell University, Ithaca, New York JEREMIAH P. OSTRIKER, Department of Astrophysical Science, Princeton University, Princeton, New Jersey FRANK L. PARKER, Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, Tennessee DENIS J. PRAGER, MacArthur Foundation, Chicago, Illinois DAVID M. RAUP, Department of Geophysical Sciences, University of Chicago, Chicago, Illinois RICHARD ]. REED, Department of Atmospheric Sciences, University of Washington, Seattle ROY F. SCHWITTERS, EG&G, Inc., Wellesley, Massachusetts ROBERT E. SIEVERS, Department of Chemistry, University of Colorado, Boulder LEON T. SILVER, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena LARRY L. SMARR, Department of Astronomy and Physics, University of Illinois, Urbana-Champaign EDWARD C . STONE, JR., Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena V1

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KARL K. TUREKIAN, Department of Geology and Geophysics, Yale University, New Haven, Connecticut RAPHAEL G. KASPER, Executive Director LAWRENCE E . MC C RAY, A ssociate Executive Director (untiT August 1, 1988) MYRON UMAN, Associate Executive Director (as of August 1, 1988) V11 .

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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished 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 federal 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 out- standing engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences 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 matters 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 government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Samuel 0. Thier is president of the Institute of Medicine. The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the federal government. The Council operates in accordance with general policies determined by the Academy under the authority of its congressional charter of 1863, which establishes the Academy as a private, nonprofit, self-governing membership corporation. The Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National Academy of Engineering and the Institute of Medicine were established in 1964 and 1970, respectively, under the charter of the National Academy of Sciences. ~ van

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Preface In 1983 the National Research Council completed a study on managing risk, leading to a report Risk Assessment in the Federal Government: Managing the Process. This report focused on im- proving risk assessment and risk decisions within the government. However, a major element in risk management in a democratic so- ciety is communication about risk. Growing concern that risk com- munication was becoming a major problem led to the chartering of a National Research Council committee to examine possibilities for improving social and personal choices on technological issues by improving risk communication. The National Research Council initiated the study out of recog- nition that technological issues, in addition to being critically im- portant, are complex, difficult, and laden with political controversy. Because the issues are scientific and technical in content, and cut across the concerns of many government agencies, scientific disci- plines, and sectors of society, the National Research Council seemed to provide an ideal forum for the conduct of such a study. Moreover, in past work on policy in the areas of risk assessment and risk man- agement (notably, the above-mentioned report on risk assessment), the National Research Council has helped develop concepts widely used in thinking about the policy issues. It became evident in discussions with representatives of some key federal agencies that no single agency was willing to undertake 1X

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x PREFA CB the needed study on its own or even to act as the primary source of support for a study at the National Research Council, even though representatives of several agencies recognized the importance of risk communication to their activities. As a result, the National Research Council initiated the study with its own funds, eventually receiving support for about half the cost from a consortium of federal and private sources. To reflect the breadth of issues to be studied, the Committee on Risk Perception and Communication was made responsible to two major units of the National Research Council, the Commission on Physical Sciences, Mathematics, and Resources and the Commission on Behavioral and Social Sciences and Education. The committee represents a cross section of many relevant kinds of experience and expertise. It includes members with extensive experience analyzing, managing, and communicating about diverse risks, including those from radiation, chemicals, drugs, disease, and consumer products. Members have experience in diverse settings, including federal and local decision-making bodies, industry, the mass media, and envi- ronmental and citizens' groups. The committee also exhibits diverse disciplinary backgrounds, including physical and social sciences, law, journalism, public health, and communications research. The Na- tional Research Council has tried in constituting the committee to achieve a balance of perspectives on all these dimensions. The committee's charge was to offer knowledge-based advice to governments, private and nonprofit sector organizations, and con- cerned citizens about the process of risk communication, about the content of risk messages, and about ways to improve risk commu- nication in the service of public understanding and better-informed individual and social choice. This report does not provide a set of prescriptional guidelines, a "how-to" manual for risk communicators. The committee concluded that many participants in the process lack fundamental understanding of the important points that form the basis for successful risk communication. Therefore this report con- centrates on developing those points. The committee believes that without such understanding detailed guidelines would not be useful. With such understanding, organizations should be able to develop their own guidelines to fit their own somewhat unique functions. Committee members met six times during the period from May 1987 to June 1988. The committee sought knowledge from several

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PREFACE X1 sources: experimental research on processes of perception, cogni- tion, and understanding in individuals, including studies of the un- derstanding of risk estimates; laboratory and field research on the conditions affecting the effectiveness of communications; and the col- lected experience of individuals and organizations that have engaged in organized communication about risk. The committee discussed a wide range of hazards, including but by no means restricted to those posed by toxic and carcinogenic substances and by radioactivity. It considered communication both about social choices, such as whether or how strictly to regulate hazardous substances or processes, and about personal choices, such as whether to change eating habits to avoid cancer or sexual habits to avoid AIDS. And the committee considered addressing advice to several audiences, including public agencies at all levels of government; legislatures; firms and industrial associations; environmental, consumer, and citizens' groups; journal- ists and mass media organizations; scientists and the organizations that employ them; and the interested public. This report presents the insights of the committee. The report should significantly improve the understanding of what the problems are in risk communication, particularly the risk communication ac- tivities of government and industry. The committee's recornmenda- tions, if followed, would significantly improve the risk communication process. JOHN F. AHEARNE, Chairman Committee on Risk Perception and Communication

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Acknowledgments Although this report represents the work of the comrn~ttee, it would not have been produced without the support of professional staff from the National Research Council, who drafted the chapters and refined them on the basis of the committee's discussions and con- clusions: Paul Stern (Chapters 1 through 4), Rob Coppock (Chap- ters 5 and 6), and Lawrence McCray (Chapter 7~. Their resumes are included with those of the committee because of their intellectual contributions, which advanced the committee's efforts throughout the study. The report was greatly improved by the diligent work of its editor, Roseanne Price. In addition, invaluable support was provided by Deborah Reischman for the first half of the committee's tenure and Nancy Crowell for the second half. The committee acknowledges with appreciation presentations made at committee meetings by the following persons: FREDERICK W. ALLEN, Associate Director, Office of Policy Analysis, U.S. Environmental Protection Agency BETSY ANcKER-JoHNsoN, Vice President, General Motors Corporation GERALD L. BARKDOLL, Associate Comrn~ssioner for Planning and Evaluation, U.S. Department of Health and Human Services, Food and Drug Administration RICHARD BAXTER, Senior Vice President, The Roper Organization .. x~n

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XIV A CKNO BLED GMENTS DON BERRETH, Director, Office of Public Affairs, Centers for Disease Control D. CHRISTOPHER CATHCART, Associate Director for Health and Safety, Chemical Manufacturers Association JOAN CLAYBROOK, President, Public Citizen DEVRA DAVIS, Director, Board on Environmental Studies and Toxicology, National Research Council ANN FISHER, Manager, Risk Communications Program, U.S. Environmental Protection Agency LOWELL HARMISON, Deputy Assistant Secretary for Health, U.S. Department of Health and Human Services NANCY HOLLAND, Executive Director, American Blood Commission THOMAS H. ISAACS, Deputy Associate Director, Office of Geologic Repositories, Office of Civilian Radioactive Waste Management, U.S. Environmental Protection Agency EDWARD KLEIN, Director, TOSCA Assistance Office, U.S. Environmental Protection Agency ANTHoNY Z. ROISMAN, Cohen, Milstein & Hausfeld, Washington, D.C. BEN C. RUSCHE, Director, Office of Civilian Radioactive Waste Management, U.S. Environmental Protection Agency CHRISTINE RUSSELL, Alicia Patterson Foundation Fellow (on leave from The Washington Post) and President, National Association of Science Writers LINDA SMITH, former Executive Committee member, STOP IT, Warren, Massachusetts ROGER STRELOW, Vice President, Corporate Environmental Programs, General Electric Company LEE M. THOMAS, Administrator, U.S. Environmental Protection Agency

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Contents SUMMARY . . A New Perspective, 1 Common Misconceptions About Risk Communication, 3 Problems of Risk Communication, 4 Conclusions and Recommendations, 8 1 INTRODUCTION The New Interest in "Risk Communication," 16 A New Definition of Risk Communication, 19 Risk Messages as Part of the Risk Communication Process, 23 Successful Risk Communication, 26 Notes, 29 2 UNDERSTANDING HAZARDS AND RISES. Toward Quantification of Hazards, 31 Knowledge Needed for Risk Decisions, 33 Gaps and Uncertainties in Knowledge, 38 xv . . 14 .............. 30

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XVI CONTENTS Scientific Judgment and Errors in Judgment, 44 Influences of Human Values on Knowledge About Risk, 47 Implications for Risk Communication, 52 Notes, 53 3 CONFLICT ABOUT HAZARDS AND RISES 54 Is Risk Increasing or Decreasing?, 54 Changes in the Nature of Hazards and in Knowledge About Them, 57 Changes in U.S. Society, 62 Politicization of the Technological Debate, 64 Implications of Conflict for Communication, 68 Notes, 71 4 PURPOSES OF RISE COMMUNICATION AND RISE MESSAGES............................................. Settings of Risk Communication, 72 Information and Influence: The Purposes of Risk Messages, 80 Use of Influence Techniques in Risk Communication, 85 Notes, 93 5 COMMON MISCONCEPTIONS ABOUT RISE COMMUNICATION ....................................... Expectations Regarding Risk Communication, 95 Beliefs About the Functioning of the Process, 100 Stereotypes About Intermediaries and Recipients, 102 Note, 107 6 PROBLEMS OF RISE COMMUNICATION Problems Deriving from the Institutional and Political System, 108 Problems of Risk Communicators and Recipients, 117 Summary, 142 Note, 142 72 . . . 94 108

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CONTENTS 7 RECOMMENDATIONS FOR IMPROVING RISK COMMUNICATION ......................................... XV11 143 Management of the Process, 149 The Content of Risk Messages, 165 A Consumer's Guide to Risk and Risk Communication, 176 Research Needs, 179 APPENDIXES A Background Information on Committee Members and Professional Staff, 185 B Bibliography, 193 C Risk: A Guide to Controversy, 211 Baruch Fischhoff D Availability of Working Papers, 320 E Key Terms and Distinctions, 321 INDEX . . 323

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IMPROVING RISK COMMUNICATION

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