NATIONAL ACADEMY PRESS
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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 panel responsible for the report were chosen for their special competences 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 Sciences, the National Academy of Engineering, and the Institute of Medicine.
This project was prepared under Grant No. X-816115-01-0 between the National Academy of Sciences and the U.S. Environmental Protection Agency.
Library of Congress Cataloging-in-Publication Data
Comparative dosimetry of radon in mines and homes / Panel on Dosimetric Assumptions Affecting the Application of Radon Risk Estimates, Board on Radiation Effects Research, Commission on Life Sciences, National Research Council.
p. cm.
Includes bibliographical references and index.
ISBN 0-309-04484-7
1. Radon—Measurement. 2. Radiation dosimetry. 3. Indoor air pollution. 4. Mine safety. I. National Research Council. Panel on Dosimetric Assumptions Affecting the Application of Radon Risk Estimates.
RA1247.R33C66 1991
628.5′35—dc20 91-10157
CIP
Cover: Mine photograph by Samet.
Copyright © 1991 by the National Academy of Sciences.
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
PANEL ON DOSIMETRIC ASSUMPTIONS AFFECTING THE APPLICATION ON RADON RISK ESTIMATES
JONATHAN M. SAMET (Chairman),
University of New Mexico, Albuquerque, New Mexico
ROY E. ALBERT,
University of Cincinnati, Cincinnati, Ohio
JOSEPH D. BRAIN,
Harvard School of Public Health, Boston, Massachusetts
RAYMOND A. GUILMETTE,
Inhalation Toxicology Research Institute, Albuquerque, New Mexico
PHILIP K. HOPKE,
Clarkson University, Potsdam, New York
ANTHONY C. JAMES,
Battelle Pacific Northwest Laboratories, Richland, Washington
DAVID G. KAUFMAN,
University of North Carolina, Chapel Hill, North Carolina
Staff
RAYMOND D. COOPER, Study Director
WILLIAM H ELLETT, Senior Program Officer
RICHARD E. MORRIS, Editor,
National Academy Press
Sponsor's Project Officers
NEAL S. NELSON,
U. S. Environmental Protection Agency
ANITA L. SCHMIDT,
U. S. Environmental Protection Agency
BOARD ON RADIATION EFFECTS RESEARCH
MORTIMER L. MENDELSOHN (Chairman),
Lawrence Livermore National Laboratory, Livermore, California
ERIC J. HALL,
Columbia University, New York, New York
DANIEL L. HARTL,
Washington University School of Medicine, St. Louis, Missouri*
LEONARD S. LERMAN,
Massachusetts Institute of Technology, Cambridge, Massachusetts
FREDERICK MOSTELLER, professor emeritus,
Harvard University, Cambridge, Massachusetts
JOSEPH E. RALL,
National Institutes of Health, Bethesda, Maryland
WARREN K. SINCLAIR,
National Council on Radiation Protection and Measurements, Bethesda, Maryland
THOMAS S. TENFORDE,
Battelle Pacific Northwest Laboratories, Richland, Washington
ARTHUR C. UPTON,
New York University Medical Center, New York, New York
Ex Officio
BRUCE M. ALBERTS,
University of California, San Francisco, California
Staff
CHARLES W. EDINGTON, Director
RAYMOND D. COOPER, Senior Program Officer
WILLIAM H ELLETT, Senior Program Officer
CATHERINE S. BERKLEY, Administrative Associate
DORIS E. TAYLOR, Administrative Assistant
COMMISSION ON LIFE SCIENCES
BRUCE M. ALBERTS (Chairman),
University of California, San Francisco, California
BRUCE N. AMES,
University of California, Berkeley, California
FRANCISCO J. AYALA,
University of California, Irvine, California
J. MICHAEL BISHOP,
University of California Medical Center, San Francisco, California
MICHAEL T. CLEGG,
University of California, Riverside, California
GLENN A. CROSBY,
Washington State University, Pullman, Washington
FREEMAN J. DYSON,
Institute for Advanced Study, Princeton, New Jersey
LEROY E. HOOD,
California Institute of Technology, Pasadena, California
DONALD E HORNIG,
Harvard School of Public Health, Boston, Massachusetts
MARIAN E. KOSHLAND,
University of California, Berkeley, California
RICHARD E. LENSKI,
University of California, Irvine, California
STEVEN P. PAKES,
University of Texas, Dallas, Texas
EMIL A. PFITZER,
Hoffmann-LaRoche, Inc., Nutley, New Jersey
THOMAS D. POLLARD,
Johns Hopkins Medical School, Baltimore, Maryland
JOSEPH E. RALL,
National Institutes of Health, Bethesda, Maryland
RICHARD D. REMINGTON,
University of Iowa, Iowa City, Iowa
PAUL G. RISSER,
University of New Mexico, Albuquerque, New Mexico
HAROLD M. SCHMECK, JR.,
Armonk, New York
RICHARD B. SETLOW,
Brookhaven National Laboratory, Upton, New York
CARLA J. SHATZ,
Stanford University School of Medicine, Stanford, California
TORSTEN N. WIESEL,
Rockefeller University, New York, New York
JOHN E. BURRIS, Executive Director
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 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. 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 O. Thier 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. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council.
Preface
Among the recommendations in the Biological Effects of Ionizing Radiation (BEIR) IV report was a statement on the need for further research and analysis on uncertainties in applying the lung cancer risks characterized for underground miners to people in their homes. Specifically, the BEIR IV committee stated:
Further studies of dosimetric modeling in the indoor environment and in mines are necessary to determine the comparability of risks per WLM [working level month] in domestic environments and underground mines.
Because of the importance to the public of the risks of radon exposure in homes and schools, the U.S. Environmental Protection Agency (EPA) asked the National Research Council (NRC) to initiate a study of the dosimetric considerations affecting the applications of risk estimates, based on studies of miners, to the general population. EPA asked that a panel be assembled to investigate the differences between underground miners and members of the general public in the doses they receive per unit exposure due to inhaled radon progeny.
CHARGE TO THE COMMITTEE
The committee was asked to do the following:
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Review the basis of current dosimetric models for inhaled radon progeny, paying particular attention to the assumptions that are a part of these models and the experimental data that are used to verify them. Compare these models with lung deposition models developed for nonradioactive pollutants.
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The committee's study should be directed toward estimating the dose per unit exposure and not exposure levels that may exist in homes or in mines.
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Examine the experimental data base for characterizing aerosols and radon progeny concentrations in underground mines and home environments, taking into account the possible changes in these environments that have occurred in the last 40 years.
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Examine differences in breathing patterns of working miners and individuals in the mining environment, taking into account the level of physical activity, sex, age, and so on. Determine to what extent the relevant physiological parameters are based on experimentally derived values, with particular reference to underground miners and other manual laborers doing similar work.
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Determine which parameters, such as bronchial generations and tissue depth, are most useful for characterizing a dose-risk relationship for radiogenic lung cancers.
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With the foregoing information, estimate the ratio of the dose per working level month to an underground miner to the dose per working level month to people of different ages and sexes in a variety of domestic environments. To the extent possible, characterize the uncertainties in these estimates.
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Define research needs, including judgments on the relative importance of the various parameters needed to calculate the dose from radon progeny. Present the results in an NRC report.
ORGANIZATION OF THE STUDY
The NRC established a committee of seven members with expertise in radon risks, radon dosimetry, aerosol physics, respiratory physiology, carcinogenesis, and lung modeling to carry out the study. General guidance was provided by the Board on Radiation Effects Research of the Commission on Life Sciences.
The committee held five meetings, four in Washington, D.C., and one in Woods Hole, Massachusetts. During an early meeting, the panel invited several outside experts to present the results of their research on lung modeling and lung cancer to ensure that a broad cross-section of the scientific community had provided input.
The study was divided into two parts. The first part was the determination of the differences in atmospheres, breathing rates, and other factors between mines and miners and homes and the people who live in them. The second part included the application of a new lung model to these factors in order to determine a ratio of dose per unit exposure in homes and mines. The report covers these areas and a discussion of other considerations affecting the risk of lung cancer from radon exposure.
ORGANIZATION OF THE REPORT
The report is arranged so that the major elements of the committee's analysis and conclusions are described first, followed by a number of background chapters that include technical details of the data and models used and the reasons for choosing the models used. After a summary of the committee's findings and recommendations for further research and analysis, the main body of the report begins with an introduction to the dosimetry of radon (Chapter 1) and how this differs in mines and homes (Chapter 2). A description of the data used by the committee on exposures of miners and people in their homes follows. Chapter 3, the main element of the report, answers the questions posed to the committee. It includes the major results of the committee's analysis. The main body of the report concludes with a description in Chapter 4 of factors other than those involved in dosimetry, that are important in determining risk.
Five background chapters describe in greater detail many of the elements that went into the first part of the report. Chapter 5 is a general description of radon dosimetry and the lung models that were used. Chapter 6 discusses aerosols in homes and mines, their diffusion and growth, and the means by which they are measured. Oral and nasal breathing and the deposition and clearance of particles in the lung are described in Chapter 7, and Chapter 8 discusses the different types of lung cancers and the cells of origin that are the targets for the dosimetry. Finally, Chapter 9 describes the specific lung model used by the committee and the calculations that led to the results given in the first part of the report.
ACKNOWLEDGMENTS
The panel acknowledges with thanks the scientific input provided by a number of invited participants. These included Dr. Geno Saccomanno, who described his studies on lung pathology; Dr. Naomi Harley, who discussed radon dosimetry; Dr. Elizabeth McDowell, who described the types of lung cells at risk; and Dr. David Swift, who spoke on the fate of inhaled radon and its progeny. All of these scientists gave freely of their data and findings and were of great help in clarifying some of the scientific issues under study.
The lung model used by the panel was developed, in part, by the task group of the International Commission on Radiological Protection (ICRP). The committee would like to thank the ICRP task group and, particularly, M. J. Egan and W. Nixon, who developed the theory for aerosol deposition in the lung upon which the model is based. The committee thanks Doris Taylor for her work on several drafts of this manuscript and for her help in making arrangements for committee meetings and travel.
Finally, thanks are due to the radon research programs sponsored by the U.S. government. Many of the data used by the committee were developed by the radon research program of the U.S. Department of Energy.