Quantitative environmental risk analysis for human health

QUANTITATIVE ENVIRONMENTAL

RISK ANALYSIS FOR

HUMAN HEALTH

QUANTITATIVE ENVIRONMENTAL

RISK ANALYSIS FOR

HUMAN HEALTH

Robert A. Fjeld

Clemson University

Norman A. Eisenberg

University of Maryland

Keith L. Compton

Silver Spring, Maryland

A JOHN WILEY & SONS, INC., PUBLICATION

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

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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 assessment—Methodology. I.

Eisenberg, Norman A. II. Compton, Keith L. III. Title.

[DNLM: 1. Environmental Exposure. 2. Risk Assessment—methods. WA 30.5

F455q 2006]

RA427.3.F554 2006

362.1—dc22

2006017999

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

This book is dedicated to our wives:

Pam (Fjeld)

Wendy (Eisenberg)

Nilofar (Compton)

vii

CONTENTS

Preface xi

1 Introduction 1

1.1 Risk Analysis 2

1.2 Risk 4

1.3 Contaminants in the Environment 8

1.4 Uses of Environmental Risk Assessment 10

1.5 Risk Assessment Process 13

References 19

Additional Reading 21

Problems 21

2 Fundamental Aspects of Environmental Modeling 23

2.1 Introduction 23

2.2 Modeling Process 23

2.3 Physical and Mathematical Basis for Risk Assessment Models 29

2.4 Contaminant Transport Equation 44

References 55

Problems 55

3 Release Assessment 60

3.1 Introduction 60

3.2 Conceptual Model 60

3.3 Contaminant Identifi cation 62

3.4 Emission-Rate Quantifi cation 66

References 78

Additional Reading 78

Problems 78

4 Environmental Transport Theory 81

4.1 Introduction 81

4.2 One-Dimensional Solutions of the Contaminant Transport Equation 83

4.3 Three-Dimensional Contaminant Transport 96

4.4 Advanced Solution Methods 97

References 100

Additional Reading 100

Problems 101

viii CONTENTS

5 Surface Water Transport 104

5.1 Introduction 104

5.2 Types of Surface Water Bodies 106

5.3 Sorption 109

5.4 Transport Modeling 116

References 123

Additional Reading 124

Problems 124

6 Groundwater Transport 127

6.1 Introduction 127

6.2 Subsurface Characterization 129

6.3 Saturated Flow in Porous Media 130

6.4 Sorption 137

6.5 Subsurface Contaminant Transport Modeling 139

6.6 Other Considerations in Groundwater Transport 148

References 152

Additional Reading 153

Problems 153

7 Atmospheric Transport 156

7.1 Introduction 156

7.2 Atmospheric Dispersion 156

7.3 Atmospheric Transport Models 161

7.4 Other Considerations 172

References 178

Additional Reading 179

Problems 179

8 Food Chain Transport 183

8.1 Introduction 183

8.2 Concentration in Soil 186

8.3 Concentration in Vegetation 190

8.4 Concentration in Animals 195

References 197

Problems 197

9 Exposure Assessment 199

9.1 Introduction 199

9.2 Dose 200

9.3 Contaminant Intake 204

9.4 Dose Calculations 209

References 216

Problems 217

CONTENTS ix

10 Basic Human Toxicology 219

10.1 Introduction 219

10.2 Fundamentals of Anatomy and Physiology 220

10.3 Mechanisms and Effects of Toxicity 237

References 242

Additional Reading 244

Problems 244

11 Dose–Response and Risk Characterization 245

11.1 Introduction 245

11.2 Biological Basis of Dose–Response Modeling 245

11.3 Elements of Quantitative Dose–Response Analysis 247

11.4 Dose–Response Modeling 261

11.5 Risk Characterization 267

11.6 Regulatory Implementation 270

References 277

Additional Reading 279

Problems 279

12 Uncertainty and Sensitivity Analyses 283

12.1 Introduction 283

12.2 Types and Sources of Uncertainty 283

12.3 Statistical Fundamentals 289

12.4 Uncertainty Propagation 298

References 311

Problems 314

13 Stakeholder Involvement and Risk Communication 316

13.1 Introduction 316

13.2 Stakeholder Involvement 317

13.3 Risk Communication 325

References 332

Problems 335

14 Environmental Risk Management 336

14.1 Introduction 336

14.2 Risk Management Process 336

14.3 Risk Management Methods 337

References 354

Problems 355

15 Environmental Laws and Regulations 356

15.1 Introduction 356

15.2 General Legal and Regulatory Structure for Environmental

Protection 356

x CONTENTS

15.3 Major Federal Environmental Laws and Regulations 357

15.4 CERCLA Process 367

15.5 Additional Regulations 372

References 373

Problems 374

Appendix A Mathematical Tools 375

A.1 Special Functions 375

A.2 Laplace Transforms 376

References 380

Additional 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

system—a 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

dose–response; 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 reader’s 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