QUANTITATIVE ENVIRONMENTAL RISK ANALYSIS FOR HUMAN HEALTH

Robert A. FjeldClemson University

Norman A. EisenbergUniversity of Maryland

Keith L. ComptonSilver Spring, Maryland

A JOHN WILEY & SONS, INC., PUBLICATION

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QUANTITATIVE ENVIRONMENTAL RISK ANALYSIS FOR HUMAN HEALTH

QUANTITATIVE ENVIRONMENTAL RISK ANALYSIS FOR HUMAN HEALTH

Robert A. FjeldClemson University

Norman A. EisenbergUniversity of Maryland

Keith L. ComptonSilver Spring, Maryland

A JOHN WILEY & SONS, INC., PUBLICATION

Copyright 2007 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

Fjeld, Robert A. Quantitative environmental risk analysis for human health / Robert A. Fjeld, Norman A. Eisenberg, Keith L. Compton. p. ; cm. Includes bibliographical references. ISBN-13: 978-0-471-72243-4 ISBN-10: 0-471-72243-X 1. Health risk assessment. 2. Health risk assessmentMethodology. I. Eisenberg, Norman A. II. Compton, Keith L. III. Title. [DNLM: 1. Environmental Exposure. 2. Risk Assessmentmethods. WA 30.5 F455q 2006] RA427.3.F554 2006 362.1dc22

2006017999

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

http://www.copyright.comhttp://www.wiley.com/go/permissionhttp://www.wiley.com

This book is dedicated to our wives:

Pam (Fjeld)

Wendy (Eisenberg)

Nilofar (Compton)

vii

CONTENTS

Preface xi

1 Introduction 1

1.1 Risk Analysis 21.2 Risk 41.3 Contaminants in the Environment 81.4 Uses of Environmental Risk Assessment 101.5 Risk Assessment Process 13References 19Additional Reading 21Problems 21

2 Fundamental Aspects of Environmental Modeling 23

2.1 Introduction 232.2 Modeling Process 232.3 Physical and Mathematical Basis for Risk Assessment Models 292.4 Contaminant Transport Equation 44References 55Problems 55

3 Release Assessment 60

3.1 Introduction 603.2 Conceptual Model 603.3 Contaminant Identifi cation 623.4 Emission-Rate Quantifi cation 66References 78Additional Reading 78Problems 78

4 Environmental Transport Theory 81

4.1 Introduction 814.2 One-Dimensional Solutions of the Contaminant Transport Equation 834.3 Three-Dimensional Contaminant Transport 964.4 Advanced Solution Methods 97References 100Additional Reading 100Problems 101

viii CONTENTS

5 Surface Water Transport 104

5.1 Introduction 1045.2 Types of Surface Water Bodies 1065.3 Sorption 1095.4 Transport Modeling 116References 123Additional Reading 124Problems 124

6 Groundwater Transport 127

6.1 Introduction 1276.2 Subsurface Characterization 1296.3 Saturated Flow in Porous Media 1306.4 Sorption 1376.5 Subsurface Contaminant Transport Modeling 1396.6 Other Considerations in Groundwater Transport 148References 152Additional Reading 153Problems 153

7 Atmospheric Transport 156

7.1 Introduction 1567.2 Atmospheric Dispersion 1567.3 Atmospheric Transport Models 1617.4 Other Considerations 172References 178Additional Reading 179Problems 179

8 Food Chain Transport 183

8.1 Introduction 1838.2 Concentration in Soil 1868.3 Concentration in Vegetation 1908.4 Concentration in Animals 195References 197Problems 197

9 Exposure Assessment 199

9.1 Introduction 1999.2 Dose 2009.3 Contaminant Intake 2049.4 Dose Calculations 209References 216Problems 217

CONTENTS ix

10 Basic Human Toxicology 219

10.1 Introduction 21910.2 Fundamentals of Anatomy and Physiology 22010.3 Mechanisms and Effects of Toxicity 237References 242Additional Reading 244Problems 244

11 DoseResponse and Risk Characterization 245

11.1 Introduction 24511.2 Biological Basis of DoseResponse Modeling 24511.3 Elements of Quantitative DoseResponse Analysis 24711.4 DoseResponse Modeling 26111.5 Risk Characterization 26711.6 Regulatory Implementation 270References 277Additional Reading 279Problems 279

12 Uncertainty and Sensitivity Analyses 283

12.1 Introduction 28312.2 Types and Sources of Uncertainty 28312.3 Statistical Fundamentals 28912.4 Uncertainty Propagation 298References 311Problems 314

13 Stakeholder Involvement and Risk Communication 316

13.1 Introduction 31613.2 Stakeholder Involvement 31713.3 Risk Communication 325References 332Problems 335

14 Environmental Risk Management 336

14.1 Introduction 33614.2 Risk Management Process 33614.3 Risk Management Methods 337References 354Problems 355

15 Environmental Laws and Regulations 356

15.1 Introduction 35615.2 General Legal and Regulatory Structure for Environmental

Protection 356

x CONTENTS

15.3 Major Federal Environmental Laws and Regulations 35715.4 CERCLA Process 36715.5 Additional Regulations 372References 373Problems 374

Appendix A Mathematical Tools 375

A.1 Special Functions 375A.2 Laplace Transforms 376References 380Additional Reading 380

Appendix B Degradation and Decay Parameters 381

Index 383

xi

PREFACE

Environmental risk analysis for human health is the systematic analytical process of assessing, managing, and communicating the risk to human health from con-taminants released to or contained in the environment in which humans live. It is a discipline central to the development of environmental regulations and the dem-onstration of compliance with those regulations. The goal of the book is to provide both the methods that are commonly used in environmental risk analysis and the underlying scientifi c basis for these methods. Although the text covers all three of the activities involved in environmental risk analysis (risk assessment, risk manage-ment, and risk communication), the focus is on environmental risk assessment, especially the computational aspects.

The book is designed for both academic and professional audiences. It may be used to instruct graduate students and advanced undergraduates with a background in a quantitative science or engineering. Practitioners may fi nd the book useful for gaining an understanding of the science and methods outside their specialty. To make the text as accessible as possible, we presume no prior knowledge of envi-ronmental processes or environmental modeling, although we do expect readers to have a working knowledge of the fundamentals of physical science and mathematics through vector calculus, including some knowledge of statistics.

Development of a textbook on environmental risk analysis is a challenging undertaking. Environmental risk analysis encompasses a variety of diverse techni-cal disciplines, including surface water hydrology, groundwater hydrology, air dis-persion meteorology, chemical process engineering, toxicology, health physics, decision analysis, and risk communication, to name a few. Each of these disciplines is a separate fi eld of technical study, often with individual academic curricula and professional certifi cation. A signifi cant challenge in developing the book has been choosing the appropriate degree of depth and detail for each of these many techni-cal disciplines. Our approach is to provide enough information for each discipline so that the reader can develop an understanding of its role in the overall analysis, its methods, and signifi cant uncertainties. Because the treatment of each specialty is limited, practitioners are likely to seek more focused texts for their particular specialty.

Certain perspectives on environmental risk analysis have shaped the treatment:

1. Most environmental risk analyses require a completely integrated approach to be successful.

2. The risk analysis is driven by the questions asked and the nature of the systema single approach does not fi t all.

3. Quantitative analysis is a useful tool, but analysts, reviewers, and managers should understand the limitations and uncertainties of the analysis.

xii PREFACE

4. Although risk assessment is the main focus of the book, risk communication, risk management, and regulatory requirements are essential features of most risk analyses and have a signifi cant impact on virtually all technical aspects of the analysis.

Several unifying principles are used to address these perspectives and to assist in organizing the text:

1. The paradigm for the risk assessment calculation is four sequential steps (release assessment, transport assessment, exposure assessment, and conse-quence assessment) in which the output of one step provides the input to the next.

2. The contaminant transport equation and its solutions may be used to model a wide variety of environmental systems by choosing model aspects and con-ditions appropriate to the system.

3. The characterization of human health consequences as either deterministic or stochastic, as is commonly done in health physics, is extended to include both chemical and radioactive contaminants, thereby providing a unifi ed basis for describing and quantifying human health consequences.

4. Both qualitative and quantitative uncertainties are important at every step of the analysis.

The book has its origins in class notes for a risk assessment course taught since the mid-1980s in the Department of Environmental Engineering and Science at Clemson University. These evolved into a set of instructional modules prepared for the U.S. Department of Energy and published in 1998. These modules were sub-sequently used at Clemson University and for six semesters of instruction in the Professional Master of Engineering Program at the University of Maryland. The book represents a signifi cant enhancement and update of the original modules and has benefi ted from extensive classroom experience.

The overall organization of the book is as follows: Chapter 1 is an overview of environmental risk analysis and environmental risk assessment, Chapter 2 describes the modeling process and fundamentals of environmental models, Chapters 3 through 11 are concerned with environmental risk assessment, Chapter 12 deals with uncertainty and sensitivity analysis, Chapter 13 covers risk communication, Chapter 14 describes methods of risk management, and Chapter 15 presents envi-ronmental laws and regulations. Since a four-step paradigm is used for the risk assessment calculation, the risk assessment chapters are organized as follows: Chapter 3, release assessment; Chapter 4, generic transport; Chapters 5 to 8, surface water, groundwater, atmospheric, and food chain transport, respectively; Chapter 9, exposure assessment; and Chapters 10 and 11, basic human toxicology and doseresponse; respectively. Much of the material presented in Chapters 2 through 11 is in the form of deterministic quantitative relationships. There are exceptions to this practice; for example, Chapter 3 contains an abbreviated treatment of proba-bilistic methods used for analyzing releases. For historical, pedagogical, and practi-cal reasons, probabilistic methods are not described substantially until Chapter 12.

PREFACE xiii

This approach allows treatment of the various disciplines in a simplifi ed, largely deterministic fashion conducive to instruction at this level.

The book is designed to allow fl exible approaches to instruction. We recognize that some readers will benefi t from certain mathematical treatments, and some will not. To accommodate varying degrees of facility with mathematics, the book is structured to facilitate passing up mathematically demanding parts without interrupting the orderly presentation of material. Thus, selected sidebars, exam-ples, and problems with heavy mathematical content can be skipped without seri-ously affecting the readers ability to proceed through the remainder of the book. Similarly, Chapter 12, Chapter 14, or both may be omitted in a one-semester course. Our experience is that readers who have stronger backgrounds in mathematics have a greater appreciation for, and accrue greater benefi ts from, using the contaminant transport equation as a unifying theoretical basis for most of the mathematical models that are used in risk calculations. Consequently, the instructor must decide whether the material in Chapter 4 is appropriate for a given class. To fi t the course into a single semester, some chapters will probably need to be skipped, depending on the course focus. For instructors wishing to emphasize the overall environmen-tal risk analysis process, Chapters 13, 14, and probably 15 are essential; however, one or more of the environmental transport chapters (Chapters 5, 6, 7, or 8) could be omitted. For instructors wishing to emphasize the risk assessment calculation, all or parts of Chapters 13, 14, or 15 could be omitted.

We are indebted to the many people who have contributed to the book. We thank Sandra Clipp for her invaluable help in preparing the manuscript, Debbie Falta for checking the examples and assisting in preparation of the solutions manual, Rachael Williams for her careful review of Chapters 1 through 9, graduate students at Clemson University and in the Professional Master of Engineering Program at the University of Maryland for valuable comments and corrections, Mary Shirley for her assistance with the fi gures, and Tom Overcamp for his review of the atmo-spheric transport chapter. Thanks are also extended to Kevin Farley, David Hoel, Owen Hoffman, Tom Kirchner, Frank Parker, Art Rood, and Linda Wennerberg, who reviewed a set of educational modules that served as a precursor to the book. We also want to thank Jerry E. and Harriet Calvert Dempsey for fi nancial support through their endowment to Clemson University.

Robert A. Fjeld Norman A. Eisenberg Keith L. Compton