Risk Assessment of Radon in Drinking Water

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--> Risk Assessment of Radon in Drinking Water Committee on Risk Assessment of Exposure to Radon in Drinking Water Board on Radiation Effects Research Commission on Life Sciences National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1999

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--> NATIONAL ACADEMY PRESS 2101 Constitution Avenue, NW Washington, D.C. 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 competences and with regard to appropriate balance. This report was prepared under EPA Contract EPA X825492-01-0 between the National Academy of Sciences and the Environmental Protection Agency. Library of Congress Cataloging-in-Publication Data Risk assessment of radon in drinking water / Committee on Risk Assessment of Exposure to Radon in Drinking Water, Board on Radiation Effects Research, Commission on Life Sciences, National Research Council. p. cm. Includes bibliographical references and index. ISBN 0-309-06292-6 (casebound). 1. Drinking water—Contamination—United States. 2. Radon—Health aspects. 3. Indoor air pollution—Health aspects—United States. 4. Radon mitigation. 5. Health risk assessment—United States. I. National Research Council (U.S.). Committee on Risk Assessment of Exposure to Radon in Drinking Water. RA592.A1 R57 1999 99-6134 615.9'02—dc21 Risk Assessment of Radon in Drinking Water is available for sale from the National Academy Press, 2101 Constitution Avenue, N.W., Box 285, Washington, DC 20055; 1-800-624-6242 or 202-334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu Copyright 1999 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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--> COMMITTEE ON RISK ASSESSMENT OF EXPOSURE TO RADON IN DRINKING WATER JOHN DOULL (Chair), University of Kansas Medical Center, Kansas City, KS THOMAS B. BORAK, Colorado State University, Fort Collins, CO JAMES E. CLEAVER, Department of Dermatology, University of California, San Francisco, CA KEITH F. ECKERMAN, Oak Ridge National Laboratory, Oak Ridge, TN LINDA C.S. GUNDERSEN, US Geological Survey, Reston, VA NAOMI H. HARLEY, New York University School of Medicine, New York, NY CHARLES T. HESS, University of Maine, Orono, ME PHILIP K. HOPKE, Clarkson University, Potsdam, NY NANCY E. KINNER, University of New Hampshire, Durham, NH KENNETH J. KOPECKY, Fred Hutchinson Cancer Research Center, Seattle, WA THOMAS E. McKONE, University of California, Berkeley, CA RICHARD G. SEXTRO, Lawrence Berkeley National Laboratory, Berkeley, CA CLS ADVISER JONATHAN M. SAMET, Johns Hopkins University, Baltimore, MD NATIONAL RESEARCH COUNCIL STAFF STEVEN L. SIMON, Study Director, Board on Radiation Effects Research KAREN M. BRYANT, Project Assistant DORIS E. TAYLOR, Staff Assistant NORMAN GROSSBLATT, Editor SPONSOR'S PROJECT OFFICER NANCY CHIU, US Environmental Protection Agency

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--> BOARD ON RADIATION EFFECTS RESEARCH JOHN B. LITTLE (Chair), Harvard School of Public Health, Boston, MA R.J. MICHAEL FRY, Oak Ridge, TN* S. JAMES ADELSTEIN, Harvard Medical School, Boston, MA†‡ VALERIE BERAL, University of Oxford, United Kingdom EDWARD R. EPP, Harvard University, Boston, MA† HELEN B. EVANS, Case Western Reserve University, Cleveland, OH† MERRIL EISENBUD, Chapel Hill, NC (deceased August 1997) MAURICE S. FOX, Massachusetts Institute of Technology, Cambridge, MA§ PHILIP C. HANAWALT, Stanford University, Palo Alto, CA (member until 6/30/98)|| LYNN W. JELINSKI, Cornell University, Ithaca, NY WILLIAM F. MORGAN, University of California, San Francisco† WILLIAM J. SCHULL, The University of Texas Health Science Center, Houston, TX DANIEL O. STRAM, University of Southern California, Los Angeles, CA SUSAN W. WALLACE, University of Vermont, Burlington, VT H. RODNEY WITHERS, UCLA Medical Center, Los Angeles, CA NATIONAL RESEARCH COUNCIL STAFF EVAN B. DOUPLE, Director, Board on Radiation Effects Research RICK JOSTES, Senior Program Officer STEVEN L. SIMON, Senior Program Officer CATHERINE S. BERKLEY, Administrative Associate KAREN BRYANT, Project Assistant PEGGY JOHNSON, Project Assistant DORIS E. TAYLOR, Staff Assistant *   New BRER Chair effective 7/1/98 †   New members effective 7/1/98 ‡   IOM §   NAS.NAE ||   ;NAS

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--> COMMISSION ON LIFE SCIENCES THOMAS D. POLLARD (Chair), The Salk Institute for Biological Studies, La Jolla, CA FREDERICK R. ANDERSON, Cadwalader, Wickersham & Taft, Washington, DC JOHN C. BAILAR, III, University of Chicago, IL PAUL BERG, Stanford University School of Medicine, Palo Alto, CA JOANNA BURGER, Rutgers University, Piscataway, NJ SHARON L. DUNWOODY, University of Wisconsin, Madison, WI JOHN L. EMMERSON, Indianapolis, IN NEAL L. FIRST, University of Wisconsin, Madison, WI URSULA W. GOODENOUGH, Washington University, St. Louis, MO HENRY W. HEIKKINEN, University of Northern Colorado, Greeley, CO HANS J. KENDE, Michigan State University, East Lansing, MI CYNTHIA J. KENYON, University of California, San Francisco, CA DAVID M. LIVINGSTON, Dana-Farber Cancer Institute, Boston, MA THOMAS E. LOVEJOY, Smithsonian Institution, Washington, DC DONALD R. MATTISON, University of Pittsburgh, Pittsburgh, PA JOSEPH E. MURRAY, Wellesley Hills, MA EDWARD E. PENHOET, Chiron Corporation, Emeryville, CA MALCOLM C. PIKE, Norris/USC Comprehensive Cancer Center, Los Angeles, CA JONATHAN M. SAMET, The Johns Hopkins University, Baltimore, MD CHARLES F. STEVENS, The Salk Institute for Biological Studies, La Jolla, CA JOHN L. VANDEBERG, Southwest Foundation for Biomedical Research, San Antonio, TX NATIONAL RESEARCH COUNCIL STAFF PAUL GILMAN, Executive Director ALVIN G. LAZEN, Associate Executive Director

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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. Bruce M. Alberts 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 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. William A. Wulf is the 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. Kenneth I. 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 furthering knowledge and advising the federal government. Functioning in accordance with general policies 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 administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council.

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--> Preface At the request of the Environmental Protection Agency (EPA) pursuant to a congressional mandate (amendment to bill S. 1316 to amend title XIV of the Public Health Service Act commonly known as the Safe Drinking Water Act), the National Research Council has appointed a multidisciplinary committee to conduct a study and report on the health risks associated with exposure to radon in drinking water. The committee was also asked to prepare an assessment of the health-risk reduction associated with various mitigation measures to reduce radon in indoor air; to accomplish this task, the committee used the results of the latest scientific studies of risk assessment and relevant peer-reviewed research carried out by organizations and individual investigators. Finally, the committee was asked to summarize the agreements and differences between the various advisory organizations on the issues relevant to the health risks posed by radon in drinking water and radon-mitigation measures and to evaluate the technical and scientific bases of any differences that exist. The Committee on Risk Assessment of Radon in Drinking Water was appointed in May 1997, held its first meeting on July 14–15, 1997, and held six additional meetings during the next 9 months. The ability of the committee to comply with this extremely tight schedule is a reflection of the dedication and expertise of the committee members and the efforts of the committee staff. The committee acknowledges the help of those individuals or organizations who gave presentations during our meetings and/or provided information in response to requests by committee members or staff and to others who helped the committee in the completion of our task.

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--> Gustav Akerbloom, Swedish Radiation Protection Institute Hannu Arvela, Finnish Radiation/Nuclear Safety Authority Timothy Barry, Environmental Protection Agency David S. Chase, New Hampshire Radiologic Health Bureau Gail Charnley, Presidential/Congressional Commission on Risk Assessment and Risk Management Nancy Chiu, Environmental Protection Agency Jack Correia, Massachusetts General Hospital Bill Diamond, Environmental Protection Agency Joe Drago, Kennedy Jenks, San Francisco, CA Susumo Ito, Professor Emeritus, Harvard University Dan Krewski, Environmental Health Centre, Ottawa, Canada Jay Lubin, National Cancer Institute J.P. Malley, Jr., University of New Hampshire Sylvia Malm, Environmental Protection Agency Frank Marcinowski, Environmental Protection Agency Lars Mjones, Swedish Radiation Protection Institute Roger McClellan, Chemical Industry Institute of Toxicology Neal S. Nelson, Environmental Protection Agency David Paris, Waterworks, Manchester, NH Dan Pederson, American Water Works Association Frederick Pontius, American Water Works Association Jerome Puskin, Environmental Protection Agency Edith Robbins, New York University David Rowson, Environmental Protection Agency Richard Toohey, Oak Ridge Institute of Science and Education George Sachs, VA Medical Center, Los Angeles Anita Schmidt, Environmental Protection Agency Daniel J. Steck, St. John's University Grant Stemmerman, University of Cincinnati Neil Weinstein, Rutgers University Jeanette Wiltse, Environmental Protection Agency This report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council's Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the authors and the National Research Council in making their published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The content of the review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their participation in the review of this report:

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--> Antone Brooks, Washington State University, Tri-Cities Bernard Cohen, University of Pittsburgh Douglas Crawford-Brown, University of North Carolina-Chapel Hill Robert E. Forster, The University of Pennsylvania School of Medicine Sharon Friedman, Lehigh University Patricia L. Gardner, New Jersey Department of Environmental Protection Roger O. McClellan, Chemical Industry Institute of Toxicology Gilbert Omenn, University of Washington Frank H. Stillinger, Bell Laboratories Rhodes Trussell, Montgomery Watson, Inc. The committee members would like to express their gratitude to the staff of the National Research Council's Board on Radiation Effects Research. The committee members are especially appreciative for study director Steven Simon's technical guidance and encouragement. They are also grateful to Karen Bryant and Doris Taylor for assistance with administrative details related to the committee's work.

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--> Contents     Public Summary   1     Executive Summary   8 1   Introduction   23     The Origin of Radon   23     Absorbed Dose from Indoor Radon   27     Composition of the Report   31 2   Baseline Information on Indoor Radon and Radon in Water in the United States   32     Indoor Radon   32     Radon in Groundwater and Public Water Supplies   36     Ambient Radon   37 3   Transfer of Radon from Water to Indoor Air   50     Measurements of Transfer Coefficients   51     Modeling of Transfer Coefficient   52     Conclusions   57 4   Dosimetry of Ingested Radon and its Associated Risk   59     Intakes and Consumption of Water   59     Physicochemical Properties of Radon   60     Fate of Radon Decay Products in the Body   73

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-->     Cancer Risk Per Unit 222Rn Concentration in Drinking Water   76     Special Populations at Risk   81 5   Dosimetry of Inhaled Radon and its Associated Risk   82     Inhalation of Radon and Its Short-lived Decay Products   82     Risk Posed by Inhalation of 222Rn Decay Products   82     Lung Dose from 222Rn Gas   83     Dose to Organs Other Than the Lung from Inhaled 222Rn   84     222Rn Decay-Product Dose During Showering   84     Lung-Cancer Risk Posed by Inhalation of 222Rn Decay Products   93     Epidemiology of Childhood Exposure and Lung-Cancer Risk   100     Environmental and Domestic Epidemiology   100     Epidemiology of Cancer of Organs Other Than Lung   102     Evaluation of Risk Per Unit Exposure from Inhaled 222Rn in Air   103 6   Molecular and Cellular Mechanisms of Radon-Induced Carcinogenesis   105     Cells at Risk   105     Cellular Damage Induced by Radon Alpha Particles   107     Transformation of Cells by Alpha Particles in Vitro   110     DNA Damage and Its Repair—the Caretaker Genes   110     Deletion Mutagenesis and Chromosomal Changes Caused by Densely Ionizing Radiation   114     Control of Cellular Responses to Damage—the Arbitrator Gene   115     Apoptosis—the Undertaker Genes   116     Initial Genetic Changes in Carcinogenesis—the Gatekeeper Genes   118     Tumor Growth and Nutrition—the Caterers   119     Genetic Instability in Irradiated Cell Populations—the Diversifiers   120     Mutations in α-Particle-Induced Tumors—the Fingerprints   121     Epidemiologic, Biophysical, and Cell-Based Models of Radon-Induced Carcinogenesis   122 7   Defining Key Variabilities and Uncertainties   124     Reliability of a Health-Risk Assessment   126     Environmental Protection Agency Process for Assessing and Evaluating Uncertainties in Radon Risk   127     Issues in Uncertainty Analysis for Radon   129     The Committee's Evaluation of Uncertainties in Risk Assessment of Radon in Drinking Water   130     Communication of Uncertain Risk Information   137     Discussion and Recommendations   139

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--> 8   Mitigation   141     Mitigation of Radon in Indoor Air   141     Mitigation of Radon in Water   160     Conclusions   179 9   Multimedia Approach to Risk Reduction   180     Derivation of the Alternative Maximum Contaminant Level (AMCL)   181     Equivalent Risk-Reduction Scenarios   182     Scenario 1: High Radon Concentrations in Water   183     Scenarios 2-4: Effects of Distribution of Radon in Indoor Air   184     Scenario 5: Use of New Radon-Resistant Construction   187     Scenario 6: Multicommunity Mitigation   188     Scenario 7: Use of Outreach, Education, and Incentives   189     Scenario 8: Outreach for Other Health Risks   193     Equity and Implementation Issues and Risk Reduction   193     Summary   196 10   Research Recommendations   198     References   200     Glossary   223     Appendixes         A Behavior of Radon and Its Decay Products in the Body   233     B A Model for Diffusion of Radon Through the Stomach Wall   241     C Water-Mitigation Techniques   249     D Risks Associated with Disinfection By-products Formed by Water Chlorination Related to Trihalomethanes (THMs)   254     E Gamma Radiation Dose from Granular-Activated Carbon (GAC) Water Treatment Units   257     F EPA Approach to Analyzing Uncertainty and Variability   260     Index   269

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