Table Of ContentTOXICOLOGY
Simon
Environmental Risk Assessment
A Toxicological Approach
The purpose of risk assessment is to support science-based decisions about how
to solve complex societal problems. Indeed, the problems humankind faces in
the twenty-first century have many social, political, and technical complexities.
E
Environmental risk assessment in particular is of increasing importance as a means
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of seeking to address the potential effects of chemicals in the environment in
both the developed and developing world. v
i
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Environmental Risk Assessment: A Toxicological Approach examines various o
aspects of problem formulation, exposure, toxicity, and risk characterization n
that apply to both human health and ecological risk assessment. Aimed at the
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next generation of risk assessors and students who need to know more about
developing, conducting, and interpreting risk assessments, the book delivers
e
a comprehensive view of the field, complete with sufficient background to
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enable readers to probe for themselves the science underlying the key issues in
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environmental risk. Written in an engaging and lively style by a highly experienced
a
risk assessment practitioner, the text:
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• Introduces the science of risk assessment—past, present, and future R
• Covers problem formation and the development of exposure factors i
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• Explains how human epidemiology and animal testing data are used k
to determine toxicity criteria
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• Provides environmental sampling data for conducting practice
risk assessments s
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• Examines the use of in vitro and ‘omics methods for toxicity testing e Environmental
• Describes the political and social aspects of science-based decisions s
in the twenty-first century s
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• Includes fully worked examples, case studies, discussion questions,
Risk Assessment
and links to legislative hearings
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Readers of Environmental Risk Assessment: A Toxicological Approach not only
learn how to execute site-specific human health and ecological risk assessments t
but also gain a greater understanding of how science is used in deciding
environmental regulations. A Toxicological Approach
K20881
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K20881_cover.indd 1 11/25/13 10:02 AM
Environmental
Risk Assessment
A Toxicological Approach
Environmental
Risk Assessment
A Toxicological Approach
Ted Simon, Ph.D., DABT
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
CRC Press
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Version Date: 20131126
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© 2010 Taylor & Francis Group, LLC
Contents
Preface...............................................................................................................xvii
Author ................................................................................................................xxi
Chapter 1 Introduction to Risk Assessment with a Nod to History .................1
Risk Assessment: Does Consistency Achieve
the Goal of Fairness? .......................................................................1
Knowledge versus Fear: The Precautionary Principle
and Unintended Consequences .......................................................4
History of Environmental Risk Assessment in the United States ...5
Risk Assessment under the National Environmental Policy Act ....5
Events of the Late 1960s Facilitated the Passage of NEPA .......7
How Much Risk Is Enough? ............................................................8
Environmental Risk Assessment Paradigm as Defined by the
Red Book .......................................................................................10
Science and Judgment in Risk Assessment: The Blue Book ........12
EPA’s Use of Defaults ...............................................................14
Validation of Models, Methods, and Data ................................15
Information and Data Needs ....................................................15
Accounting for Uncertainty ......................................................18
Understanding and Dealing with Variability ...........................18
Aggregation of Risks ................................................................19
1997 Federal Commission Report .................................................19
Realism, Cost, and the Separation of Risk Assessment
and Risk Management ...................................................................20
USEPA Addresses Variability and Uncertainty .......................21
Compounding Conservatism ....................................................22
Risk Assessment as Practiced Internationally ..............................23
Risk Assessment in China May Blaze a Trail for the
Developing World .....................................................................24
Risk Assessment in the European Union .................................25
Risk Assessment in Canada ......................................................26
Sangamo-Weston Superfund Site: What Happens When
Things Go Right! ...........................................................................27
Perception Is Reality: Risk Communication and Stakeholder
Participation ..................................................................................28
Public Perception of Hexavalent Chromium:
A Cautionary Tale ....................................................................32
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© 2010 Taylor & Francis Group, LLC
viii Contents
Perception Is Reality: Why the Movie Erin Brockovich
Changed the Public’s View of Chromium ................................34
Assumption of Causation ..............................................................35
Key Concepts in Modern Risk Assessment ..................................37
Mode of Action .........................................................................37
Point of Departure ....................................................................37
Biomarker .................................................................................37
Biomonitoring Equivalent ........................................................38
Physiologically Based Pharmacokinetic Modeling ..................38
Exercises for Thought and Discussion ..........................................38
Current Debate about Chemical Safety ....................................38
Risk Assessment History: Robert F. Kennedy’s Speech
at the University of Kansas .......................................................39
Animal and Human Carcinogens .............................................39
References .....................................................................................39
Further Readings ...........................................................................47
Chapter 2 Perception, Planning and Scoping, Problem Formulation,
and Hazard Identification: All Parts of Risk Assessment .............49
What Is Risk and How Can We Estimate Risk? ...........................49
Risk of Being Struck by Lightning ...........................................50
Frequentist or Actuarial Risk ..............................................50
Predicted Risk: Using a Model ............................................50
Perceived Risk .....................................................................52
Designing Risk Assessments: Planning and Scoping versus
Problem Formulation .....................................................................53
Need for Problem Formulation Is Not Limited to
Ecological Risk Assessment .....................................................54
Recognition of the Importance of Problem Formulation
for Human Health Risk Assessment .........................................55
Hazard Identification versus Risk Characterization ......................60
What Is Hazard Identification? .................................................60
Uncertainty Classifications Used in Hazard Identification ......62
Weight of Evidence ...................................................................63
Epidemiologic Studies for Hazard Identification ..........................65
Biomonitoring and the Use of Biomarkers ...............................66
Biomarkers of Exposure and Biomarkers of Effect .............67
Historical Reconstruction of Exposure ....................................69
False Positives in Epidemiologic Studies ............................70
Use of Quantiles Reduces Statistical Power ........................70
Example of Hazard Identification from Epidemiology ............71
Animal Bioassays as the Basis for Hazard Identification .............72
In Vitro Testing as the Basis for Hazard Identification .................73
© 2010 Taylor & Francis Group, LLC
Contents ix
Toxicity Pathways, Adverse Outcome Pathways, and MOA ....74
Implementing Toxicity Testing in the Twenty-First
Century (TT21C) ......................................................................75
Can In Vitro Assays Cover All Toxicity Pathways? .................75
In Vitro Assays May Be Useful for Hazard Identification Only ....76
In Silico Prediction Models as the Sole Basis for Hazard
Identification ..................................................................................76
Quantitative Structure–Activity Relationships .........................77
Conclusions ...................................................................................78
Exercises for Thought and Discussion ..........................................78
Understanding Statistical Power ...............................................78
Discussion of the Differences in Problem Formulation
between NATO and the Silver Book ........................................80
Exploring QSAR: Part 1 ...........................................................80
Exploring QSAR: Part 2 ...........................................................80
References .....................................................................................80
Chapter 3 Exposure Assessment ....................................................................89
Scenarios and Receptors ...............................................................89
External Dose, Point of Contact, and Internal Dose .....................90
Individual and Population Exposure .............................................94
Frequency Distributions as a Representation of Exposure
Factors in a Population: The Lognormal Distribution as an
Example .........................................................................................95
Common Sense Thinking about Exposure ...................................97
Common Sense about Variability .............................................98
Common Sense about Uncertainty ...........................................98
Compounding Conservatism ..................................................100
Concentration Term .....................................................................100
Exposure Unit Concept ............................................................101
Random versus Nonrandom Exposure ....................................101
Temporal Variation in Concentration .....................................102
Variability of Concentration in Various Environmental Media ....102
Variability of Concentrations in Air ..................................102
Variability of Concentrations in Groundwater ..................103
Variability of Concentrations in Surface Water ................103
Variability of Concentrations in Soil .................................103
Variability of Concentrations in Sediment ........................104
Variability of Concentrations in Fish ................................104
Assessing Exposure Factors and Supporting Data ......................104
Soil and Dust Ingestion ..........................................................104
Mass Balance of Fecal Tracers ..........................................105
Children’s Microactivity Studies .......................................107
© 2010 Taylor & Francis Group, LLC
