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rose Drinking ally In -aver Subcommittee to Update the 1999 Arsenic in Drinking Water Report Committee on Toxicology Board on Environmental Studies and Toxicology Division on Earth and Life Studies National Research Council NATIONAL ACADEMY PRESS Washington, D.C.

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NATIONAL ACADEMY PRESS 2101 Constitution Ave., 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 Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineenug, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This prod ect was supported by Cooperative Agreement No. X-82899401 -0 between the National Academy of Sciences and the U.S. Environmental Protection Agency. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authoress and do not necessarily reflect the view of the organizations or agencies that provided support for this project. Library of Congress Catalog Card Number: 2001097317 International Standard Book Number: 0-309-07629-3 Additional copies of this report are available from: National Academy Press 2101 Constitution Ave., NW Box 285 Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington metropolitan area) http://www.nap.edu Copyright 2001 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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National Academy of Sciences National Academy of Engineering Institute of Medicine National Research Council 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. Wm. A. Wulf 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. 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. Wm. A. Wulf are chairman and vice chairman, respectively, of the National Research Council.

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SUBCOMMITTEE TO UPDATE THE 1999 ARSENIC IN DRINKING WATER REPORT ROBERT A. GOYER (Chair9, (emeritus) University of Western Ontario, London, Ont., Canada KENNETH P. CANTOR, National Cancer Institute, Bethesda, Maryland DAVID L. EATON, University of Washington, Seattle, Washington ROGENE F. HENDERSON, Lovelace Respiratory Research Institute, Albuquerque, New Mexico MICHAEL J. KOSNETT, University of Colorado Health Sciences Center, Denver, Colorado LOUISE M. RYAN, Harvard School of Public Health, Boston, Massachusetts KIMBERLY M. THOMPSON, Harvard School of Public Health, Boston, Massachusetts MARIE E. VAHTER, Karolinska Institutet, Stockholm, Sweden BOGUS WALKER, JR., Howard University Medical Center, Washington, D.C. Staff MICHELLE C. CATKIN, Project Director ROBERTA M. WEDGE, Senior Program Officer KULBIR BAKSHI, Senior Program Officer RUTH E. CROSSGROVE, Editor MIRSADA KARALIC-LONCAREVIC, Research Assistant BRYAN P. SHIPLEY, Project Assistant KELLY A. CLARK, Editorial Assistant Sponsor U.S. ENVIRONMENTAL PROTECTION AGENCY v

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COMMITTEE ON TOXICOLOGY BAILUSWALKER,JR. (Chair), Howard University Medical Center, Washington, D.C. MELVIN E. ANDERSEN, Colorado State University, Fort Collins, Colorado GERMANE M. BUCK, National Institute of Health, Washington, D.C. ROBERT E. FORSTER II, University of Pennsylvania, Philadelphia, Pennsylvania WILLIAM E. HALPERIN, New Jersey Medical School, Newark, New Jersey CHARLES H. HOBBS, Lovelace Respiratory Research Institute and Lovelace Biomedical and Environmental Research Institute, Albuquerque, New Mexico SAMUEL KACEW, University of Ottawa, Ottawa, Ontario NANCY KERKVLIET, Oregon State University, Corvallis, Oregon MICHAEL J. KOSNETT, University of Colorado Health Sciences Center, Denver, Colorado MORTON LIPPMANN, New York University School of Medicine, Tuxedo, New York ERNEST E. MCCONNELL, ToxPath, Inc., Raleigh, Norm Carolina THOMAS E. MCKONE, Lawrence Berkeley National Laboratory and University of California, Berkeley, California HAR1HARA MEHENDALE, University of Louisiana at Monroe, Monroe, Louisiana DAVID H. MooRE, Battelle Memorial Institute, Bet Air, Maryland LAUREN ZEISE, California Environmental Protection Agency, Oakland, California Stay KUEBIR S. BAKSHI, Program Director SUSAN N.J. MARTEE, Program Officer ABIGAIL E. STACK, Program Officer AIDA NEEL, Acl~ninistradve Assistant JESSICA BROCK, Project Assistant Al

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BoARD ON ENVIRONMENTAL STUDIES AND TOMCOLOGY] GORDON ORIANS (Chair), University of Washington, Seattle, Washington JOHN Douse ~ vice Chair),University of Kansas Medical Center, Kansas City, Kansas DAVID ALLEN, University of Texas, Austin, Texas INGRID C. BURKE, Colorado State University, Fort Collins, Colorado THOMAS BURKE, Johns Hopkins University, Baltimore, Maryland GLEN R. CASS, Georgia Institute of Technology, Atlanta, Georgia WIGWAM L. CHAMEIDES, Georgia Institute of Technology, Atlanta, Georgia CHRISTOPHER B. FIELD, Carnegie Institute of Washington, Stanford, California JOHN GERHART, University of California, Berkeley, California J. PAUL OILMAN, Celera Genomics, Rockville, Maryland DANIEL S. GREENBAUM, Health Effects Institute, Cambridge, Massachusetts BRUCE D. HAMMOCK, University of California, Davis, California ROGENE HENDERSON, Lovelace Respiratory Research Institute, Albuquerque, New Mexico CAROL HENRY, American Chemistry Council, Arlington, Virginia ROBERT HUGGETT, Michigan State University, East Lansing, Michigan JAMES F. KrrcHELL, University of Wisconsin, Madison, Wisconsin DANIEL KREWSKI, University of Ottawa, Ottawa, Ontario JAMES A. MACMAHON, Utah State University, Logan, Utah CHARLES O'MELIA, Johns Hopkins University, Baltimore, Maryland WILLEM F. PASSCHIER, Health Council of the Netherlands, The Hague ANN POWERS, Pace University School of Law, White Plains, New York KIRK SMITH, University of California, Berkeley, California Senior Staff JAMES J. REISA, Director DAVID J. POLICANSKY, Associate Director and Senior Program Director for Applied Ecology RAYMOND A. WASSEL, Senior Program Director for Environmental Sciences and ~ . . ~ngmeenng KULBIR BAKSHI, Program Director for Committee on Toxicology ROBERTA M. WEDGE, Program Director for Risk Analysis K. JOHN HOLMES, Senior Staff Officer RUTH E. CROSSGROVE, Managing Editor 'This study was planned, overseen, and supported by the Board on Environmental Studies and Toxicology. . V11

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OTHER REPORTS OF THE BOARD ON ENVIRONMENTAL STUDIES AND TOMCOLOGY Evaluating Vehicle Emissions Inspection and Maintenance Programs (2001) Compensating for Wetland Losses Under the Clean Water Act (2001) A Risk-Management Strategy for PCB-Contaminated Sediments (2001) Toxicological Effects of Methylmercury (2000) Strengthening Science at the U.S. Environmental Protection Agency: Research- Management and Peer-Review Practices (2000) Scientific Frontiers in Developmental Toxicology and Risk Assessment (2000) Modeling Mobile-Source Emissions (2000) Copper in Drinking Water (2000) Ecological Indicators for the Nation (2000) Waste Incineration and Public Health (1999) Hormonally Active Agents in the Environment (1999) Research Priorities for Airborne Particulate Matter: I. Immediate Priorities and a Long-Range Research Portfolio (1998~; II. Evaluating Research Progress and - Updating the Portfolio (1999~; III. Early Research Progress (2001) Ozone-Fo~'~ing Potential of Reformulated Gasoline (1999) Arsenic in Drinking Water (1999) Brucellosis in the Greater Yellowstone Area (1998) The National Research Council's Committee on Toxicology: The First 50 Years (1997) Carcinogens and Anticarcinogens in the Human Diet (1996) Upstream: Salmon and Society in the Pacific Northwest (1996) Science and the Endangered Species Act (1995) Wetlands: Characteristics and Boundaries ~ 1995) Biologic Markers (5 reports, 1989-1995) Review of EPA's Environmental Monitoring and Assessment Program (3 reports, 1994-1995) Science and Judgment in Risk Assessment (1994) Pesticides in the Diets of Infants and Children (1993) Setting Priorities for Land Conservation (1993) Protecting Visibility in National Parks and Wilderness Areas (1993) Dolphins and the Tuna Industry (1992) Science and the National Parks (1992) Assessment of the U.S. Outer Continental Shelf Environmental Studies Program, Volumes I-IV (1991-1993) Human Exposure Assessment for Airborne Pollutants (1991) Rethinking the Ozone Problem in Urban and Regional Air Pollution (1991) Decline of the Sea Turtles ~ 1990) Copies of these reports may be orderedfrom the National Academy Press (800) 624-6242 (202) 334-3313 w~w.nap.edu . . . V111

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Preface Under the Safe Drinking Water Act of 1976, the U.S. Environmental Protec- tion Agency (EPA) adopted an interim maximum contaminant level (MCL) for arsenic in drinking water of 50 micrograms per liter (,ug/L) as part of the National Interim Primary Drinking Water Standards; that standard was orig~- nally set in 1942. EPA conducted a risk assessment for arsenic in Mining water in 1988. In 1996, the National Research Council (NRC) was asked to review independently the scientific database and evaluate the validity of that risk assessment. The NRC's 1999 report Arsenic in Drinking Water, con- cluded that "the current EPA MCL for arsenic in drinking water of 50 ~g/L does not achieve EPA's goal for public health protection and therefore re- quires downward revision as promptly as possible." On January 22, 2001, EPA issued a pending standard MCL of 10 Egg. Then on March 23,2001, EPA delayed the effective date of the arsenic rule until further studies were conducted. In April, EPA's Office of Water requested that the NRC update its ~ 999 Arsenic in Drinking Water report. In this report, the NRC's Subcommittee to Update the 1999 Arsenic in Drinking Water Report reviews the available toxicological, epidemiological, and risk assessment literature that has been published since the 1999 report. The subcommittee reviewed data for dose-response assessment and risk esti- mation; assessed whether the most recent EPA analysis is adequate for esti- mating an effective dose for a ~ TO response; determined whether EPA' s analy- sis appropriately considers and characterizes the available data on the mode IX

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x PREFACE of action of arsenic and the information on dose-response and uncertainties when assessing the public-health impacts; and determined whether EPA' s risk estimates for 3, 5, 10, and 20 ~g/L of arsenic are consistent with available scientific information, including information from new studies. This report has been reviewed in Raft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC's Report Review Committee. The purpose ofthis inde- pendent review is to provide candid and critical comments that will assist the institution in making its 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 review comments and draft manu- script remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report: Bruce N. Ames, University of California, Berkeley; H. Vasken Aposhian, University of Arizona; Andrew A. Benson, University of California, San Diego; Kenneth G. Brown, Kenneth G. Brown, Inc.; Yvonne Dragan, Ohio State University; Marsha Ford, Carolinas Medical Center; Joshua W. Ham~- ton, Yarmouth College; Bruce P. Lanphear, University of Cincinnati; Denise Lewis, U.S. Department of Agriculture; Roger O. McClellan, Chemical Indus- try Institute of Toxicology; Mitchell Small, Carnegie Mellon University; Alian H. Smith, University of California, Berkeley; and Ronald Wyzga, Electric Power Research Institute. Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by Gilbert S. Omenn, University of Michigan, and Frank H. Stillinger, Princeton University. Appointed by the NRC, they were responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully consid- ered. Responsibility for the final content of this report rests entirely with the authonug committee and the institution. The subcommittee gratefully acknowledges the following individuals for providing background information and for making presentations to the sub- committee: Christine Todd Whitman, Ephraim King, Diane Regas, lames Taft, and Nanette Wiltse, EPA; Richard Bull, EPA's Science Advisory Board Drinking Water Committee; Lawrence Bazel, Western Coalition of Arid States; Erik Olson, Natural Resources Defense Council; Allan Smith, Univer- sity of California, Berkeley; Gerhard Stohrer, Risk Policy Center; Janice Yager, Electric Power Research Institute; Gunther Craun, City of Albuquer- que; Kevin Bromberg, U.S. Small Business Administration; Bob Fensterheim,

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PREFACE Xi Environmental Arsenic Council; Angela Logomasini, Competitive Enterprise Institute; Steven Lamm, Consultants in Epidemiology and Occupational Health, Inc.; Richard Nelson, Nebraska Department of Health and Human Services; and Tom Richichi, American Wood Preservers Institute. In addition, the subcommittee wants to give special thanks to individuals who provided data, further analysis, statistical analysis programs, and background informa- tion to the subcommittee: John Bennett, Andrew Schulman, Irene Dooley, and Charles Abernathy, EPA; Knashawn Morales, Harvard School of Public Health; Ming-Hui Chen, Worcester Polytechnic Institute; Claudia Hopenhayn- Rich, University of Kentucky; Michael Bates, University of California, Berke- ley; and John Potter, Fred Hutchison Cancer Research Center. The subcommittee is grateful for the assistance of the NRC staff for pre- paring the report. Staff members who contributed to this effort are Michelle Catlin, project director; James I. Reisa, director ofthe Board on Environmen- tal Studies and Toxicology; Roberta M. Wedge, program director for risk analysis; KuTbir Bakshi, program director for the Committee on Toxicology; Ruth E. Crossgrove, managing editor; Mirsada Karalic-Loncarev~c, informa- tion specialist; and Bryan P. Shipley, project assistant. Other staff members who contributed to this effort are Ellen Mantus, Abigail Stack, and Susan Martel, program of ricers; LeahProbst, Lucy Fusco, and Jessica Parker, project assistants; and Kelly Clark editorial assistant. Finally, ~ would especially like to thank all the members of the subcom- mittee for their exceptional efforts throughout the development of this report. The subcommittee members have gone above and beyond the call of duty to complete this report within a very short time frame. Robert A. Coyer, M.D. Chair, Subcommittee to Update the 1999 Arsenic Report

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Contents Recommendations, 133 References, 135 5 Quantitative Evaluation of Risks Using Modeling Approaches Overview of the Science Underlying EPA's 2001 Proposed Regulation, 141 Overview of the SAB's Report on the 2001 Risk Assessment, 148 The Subcommittee's Evaluation, 151 Summary and Conclusions, 1 73 Recommendations, 174 References, 175 6 Conclusions.~ ~ ~.~ ~ ~ ~ ~ ~.~ Findings of the Subcommittee, 180 Comparisons of Results of Dose-Response Assessments, 181 Plausibility of Cancer Risk Estimates, 185 Summary and Conclusions, 188 References, 188 ~ X11 .. 141 ... 180

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Contents Summary .... 1 Introduction . . ............ ~ 5 Summary of NRC's ~ 999 Arsenic in Drinking Water Report, ~ 6 Policy Background, ~7 Charge to the Subcommittee, 20 Organization of this Report, 21 References, 22 2 Human Health Effects 24 Summary of Human Health Effects Discussed in the ~ 999 Report, 24 Recent Studies of Noncancer Effects in Humans, 25 Recent Studies of Cancer Effects in Humans, 37 Latency Period, 6 Essentiality, 65 Summary and Conclusions, 65 Recommendations, 68 References, 69 3 ExperimentalStudies 75 Summary of Experimental Studies Discussed in the 1999 Report, 75 Toxicokinetics, 77 . . . x'''

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XiV CONTEN75 Animal Toxicity Studies, 86 Mechanisms of Toxicity, 91 Summary and Conclusions, 120 Recommendations, 121 References, 122 4 Variability and Uncertainty ........ .... 133 Variability Versus Uncertainty, 133 Variability and Uncertainties Discussed in the ~ 999 Report, ~ 34 Sources of Variability, 135 Sources of Uncertainty, 150 Value-of-Information Approach, 159 Summary and Conclusions, 160 Recommendations, 161 References, 162 5 Quantitative Assessment of Risks Using Modeling Approaches ~ 69 Overview of the Science Underlying EPA's 200 ~ Proposed Regulation, 169 Overview of the SAB's Report on the 200 ~ Risk Assessment, 177 The Subcommittee's Evaluation, 180 Summary and Conclusions, 207 Recommendations, 209 References, 209 6 Hazard Assessment ............. Findings of the Subcommittee, 214 Comparisons of Results of Dose-Response Assessments, 216 Plausibility of Cancer Risk Estimates, 221 Summary and Conclusions, 223 References, 224 ...... 214

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Arsenic in Drinking Water 2001 Update

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