Risk Assessment for Chemicals in Drinking Water

Contributors ix

Foreword xi

Preface xiii

1 Introduction to Drinking Water Risk Assessment 1
Robert A. Howd

Development of Drinking Water Regulations 2

The Risk Assessment Process 8

Public Perceptions and the Precautionary Principle 13

References 14

2 Summary of the Development of Federal Drinking Water Regulations and Health-Based Guidelines for Chemical Contaminants 17
Joyce Morrissey Donohue and Wynne Maynor Miller

Selecting Candidates for Regulatory Consideration 19

Key Components for Regulatory Development 20

Development of Regulatory Values 28

Nonregulatory Options 30

References 32

3 Interpretation of Toxicologic Data for Drinking Water Risk Assessment 35
Robert A. Howd and Anna M. Fan

Animal Toxicity Studies 38

Human Toxicity Studies 47

Conclusions 57

References 57

4 Exposure Source and Multiroute Exposure Considerations for Risk Assessment of Drinking Water Contaminants 67
Kannan Krishnan and Richard Carrier

Exposure Source Considerations in Risk Assessment 68

Routes of Exposure and Dose Calculations 72

References 86

5 Toxicokinetics for Drinking Water Risk Assessment 91
John C. Lipscomb

Evaluation of Toxicity Data 93

Toxicokinetics: PBPK Modeling 95

Risk Assessment 101

Conclusions 117

References 118

6 Health Risk Assessment of Chemical Mixtures in Drinking Water 123
Richard C. Hertzberg, Glenn E. Rice, Linda K. Teuschler, J. Michael Wright and Jane E. Simmons

Drinking Water Mixture Concerns 124

Estimating Exposures to Multiple Chemicals in Drinking Water 130

Toxicological Concepts for Joint Toxicity 139

Chemical Mixtures Risk Assessment Methods 143

New Approaches for Assessing Risk from Exposure to Drinking Water Mixtures 155

Conclusions 162

References 163

7 Protection of Infants Children and Other Sensitive Subpopulations 171
George V. Alexeeff and Melanie A. Marty

Factors Influencing Differences in Susceptibility Between Infants and Children and Adults 173

Critical Systems and Periods in Development 185

Age at Exposure and Susceptibility to Carcinogens 189

Drinking Water Standards Developed to Protect Sensitive Subpopulations 190

References 192

8 Risk Assessment for Essential Nutrients 201
Joyce Morrissey Donohue

Assessment Approaches 203

Comparison of Guideline Values 206

Risk Assessment Recommendations 210

References 211

9 Risk Assessment for Arsenic in Drinking Water 213
Joseph P. Brown

Occurrence and Exposure 214

Metabolism 216

Health Effects 221

Risk Assessment 245

Conclusions 250

References 252

10 Risk Assessment for Chloroform Reconsidered 267
Richard Sedman

Carcinogenic Effects 268

Noncancer Toxic Effects 268

Mechanisms of Carcinogenicity 271

Regulation of Cancer Risk 280

Discussion 281

References 283

11 Risk Assessment of a Thyroid Hormone Disruptor: Perchlorate 287
David Ting

Background 287

Human Health Risk Assessment 292

Risk Characterization and Conclusions 296

References 298

12 Emerging Contaminants in Drinking Water: A California Perspective 303
Steven A. Book and David P. Spath

Emerging Chemicals of the Recent Past 304

Newer Emerging Contaminants 306

Future Emerging Chemicals 306

Conclusions 311

References 312

13 U.S. EPA Drinking Water Field Office Perspectives and Needs for Risk Assessment 315
Bruce A. Macler

The Nature of Regulatory Risk Assessments 315

Use of Drinking Water Risk Information in EPA Field Offices 318

Conclusions 322

References 322

14 Risk Assessment: Emerging Issues Recent Advances and Future Challenges 325
Anna M. Fan and Robert A. Howd

Emerging Issues 326

Advances in Science Approaches and Methods 332

Conclusions 357

References 359

Index 365