EPA Region 10
Supplemental Ecological Risk Assessment
Guidance for Superfund
EPA910-R-97-005
June 1997
Prepared by:
US EPA Region 10
Office of Environmental Assessment
Risk Evaluation Unit
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FOREWORD
The purpose of the EPA Region 10 Supplemental Ecological Risk
Assessment Guidance for Superfund is to summarize and highlight
important concepts and steps of the Remedial Investigation/Feasibility
Study (RI/FS) relevant to the risk assessment. Also, it is designed to identify
specific deliverables that should be submitted to Region 10 during the
development of the baseline risk assessment. This guidance is a
supplement to the national Ecological Risk Assessment Guidance for
Superfund: Process for Designing and Conducting Ecological Risk
Assessment (EPA 1996a), Risk Assessment Guidance for Superfund,
Volume II (RAGS) (EPA 1991c&d, EPA 1989c&d) and the Framework for
Ecological risk Assessment (EPA 1992a).
This regional guidance applies solely to risk assessments conducted
at region 10 National Priorities List (NPL) sites. This guidance is primarily
intended to clarify and extend the national RAGS, and unless other wise
agreed upon with EPA Region 10 project manager (RPM), and/or risk
assessors, the regional guidance should prevail.
Region 10 guidance is intended for use by RPMs and risk assessors
preparing human health and ecological risk assessments for CERCLA NPL
sites in Region 10. Other uses (e.g., risk assessments conducted at RCRA
facilities) may be appropriate, but should first be approved by the RPM.
This guidance does not constitute rule-making by the Agency, and
may not be relied on to create a substantive or procedural right enforceable
by any other person. Region 10 reserves the right to take action that is at
variance with this guidance. Contextually appropriate application of the
concepts presented in EPA Region 10 Supplemental Ecological Risk
Assessment Guidance for Superfund should help to create scientifically
sound, technically defensible and consistent risk assessments in Region
10.
Updates to this guidance relating to specific technical issues and/or
regarding particular relevant case study examples will be issued in the form
of the Region 10 Risk Report, a new, intermittent regional publication. This
guidance document, and subsequent issues of the Region 10 Risk Report,
supersede all previous Ecological Risk Assessment Guidance issued from
the Office of Environmental Assessment and Superfund in Region 10.
Copies of the regional guidance and other related documents may be
obtained from the Environmental Protection Agency, Region 10 homepage
(http://www.epa.gov/r1 Oearth/r10.html).
*******
For questions regarding this regional guidance, contact:
Julius U. Nwosu, Region 10, Risk Evaluation Unit, 206/553-7121.
E-mail: Nwosu.Julius@epamail.epa.gov.
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Table of Contents
1.0 INTRODUCTION 1
1.1 Regional Technical Guidance 2
1.2 Focus of Risk Assessment 4
1.3 Scheduling of Deliverables 5
2.0 RI/FS PROJECT PLANNING 10
2.1 Preliminary Phase (Steps 1 & 2) 10
2.2 Conceptual Site Model 11
2.3 Preliminary Remediation Goals 14
2.3.1 List Expected Contaminants 15
2.3.2 Identify Potential ARARs 16
2.3.3 Identify Risk-based Concentrations 16
2.3.4 Present PRG Information in a Table 17
2.4 Consideration of Risk Assessment Data Needs in the Work Plan 17
2.4.1 Use of Sampling Data for the Risk Assessment 18
2.4.2 Analytes and Detection Limits 18
3.0 Preliminary Data Analysis 19
3.1 Scheduling of Risk Assessment Deliverables During Preliminary Data Analysis
19
3.2 Evaluation of Laboratory Contaminants and Natural Background 20
3.2.1 Site Related Contaminants 21
3.2.2 Natural Background 21
3.2.3 Identification of Contaminants of Concern (COPCs) 23
3.3 Ecological Risk-based Screening 23
4.0 BASELINE ECOLOGICAL RISK ASSESSMENT 27
4.1 Introduction 27
4.1.1 Chapter Objective 28
111
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Supplemental Ecological Risk Assessment Guidance for Superfund
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4.12 Roles of Parties Involved in the Ecological Risk Assessment 28
4.2 Step 3: Problem Formulation 28
4.2.1 Refinement of Contaminants of Concern 29
4.2.2 Further Characterization of Ecological Effects 29
4.2.3 Review & Refinement of Contaminant Fate and Transport, Exposure
Pathways, and Ecosystems at Risk 29
4.2.4 Selection of Assessment Endpoints 30
4.2.5 Refinement of Conceptual Site Model and Testable Hypotheses .... 30
4.2.6 Literature Search 31
4.3 Step 4: Selection of Study Design & Data Quality Objectives 32
4.3.1 Selection of Measurement Endpoints 32
4.3.2 The Relationship Between Measurement Endpoints and Assessment
Endpoints 33
4.3.3 Lines of evidence 35
5.0 Step 5: Site Assessments (Verification of Field and Sampling Plan) 36
5.1 Sampling and Analysis Plan 36
5.2 Verification of Exposure Pathways 36
5.3 Estimation of Exposure Point Concentrations 36
5.4 Toxicity Tests 39
5.5 Toxicity Bioassays 39
6.0 Step 6: Analysis Phase (Field Investigation and Data Analysis) 40
6.1 Field Studies 42
6.2 Analysis of Ecological Exposures and Effects 42
7.0 Step 7: Risk Characterization 44
7.1 Risk Estimation and Uncertainty Analysis 45
7.1.1 Risk Estimation 45
7.1.2 Risk Description 46
7.1.2.1 Current Adverse Effects 47
7.1.2 .2 Future Adverse Effects 47
7.1.3 Risk Calculation 47
7.1.4 Uncertainty Analysis 50
7.1.5 Interpretation of Uncertainty 51
IV
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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7.2 Interpretation of Ecological Significance 52
7.2.1 Conclusion with Evaluation of Ecological Significance 53
8.0 Step 8: Risk Management 54
9.0 RISK ASSESSMENT TASKS FOR THE FS 55
9.1 Risk Evaluation of Remedial Alternatives 55
9.2 Scheduling of Risk Assessment Deliverables for the FS 55
10.0 ECOLOGICAL RISK ASSESSMENT RESOURCES 56
10.1 General Guidance 56
10.2 Screening Values 57
10.3 Uncertainty References 57
10.4 Where to Obtain Documents 58
11.0 REFERENCES 59
v
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APPENDICES
Appendix A Background Determination for Inorganics in Soils
Appendix B (I) Bioavailability of Inorganic Contaminants in soil
(ii) Oak Ridge Toxicological Benchmark Values
Appendix C Risk Report ("Tool Box")
Technical Issues:
Radionuclide Exposure Parameters for Ecological Receptors
Appendix D Risk Report Case Study Summaries
ATTACHMENTS
Attachment 1
VI
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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List of Common Risk Assessment Acronyms
ARAR applicable or relevant and appropriate requirement
AWQC ambient water quality criteria
BTAG biological technical assistance group
CERCLA Comprehensive Environmental Response, Compensation and
Liability Act of 1980 (Superfund)
COPCs contaminants of potential concern
CSM conceptual site model
DQO data quality objectives
EPA [United States] Environmental Protection Agency
ERA ecological risk assessment
FS feasibility study
HI hazard index
HQ hazard quotient
IAEA International Atomic Energy Agency
LD50 dose which produces a 50% mortality rate in a given species
LOAEL lowest observed adverse effects level
MCL maximum contaminant level
MCLG maximum contaminant level goal
NCP National Oil and Hazardous Substances Pollution Contingency Plan
NPL National Priorities List
NOAEL no observed adverse effects level
PRG preliminary remediation goal
PRP potentially responsible party
RAGS EPA Risk Assessment Guidance for Superfund
RAO remedial action objectives
RBC risk-based concentration
Rl remedial investigation
ROD record of decision
RPM regional project manager
SAP sampling and analysis plan
SARA Superfund Amendments and Reauthorization Act of 1986
SMDP scientific management decision point
TRV toxicity reference value
TEF toxic equivalency factor
TEQ toxicity equivalence
Vll
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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List of Common Risk Assessment Acronyms (cont'd)
UCL upper confidence limit
UTL upper tolerance level
WP work plan
Vlll
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List of Exhibits
EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Lists of Exhibits & Text-boxes
Exhibit 1-1
Exhibit 1-2
Exhibit 1-3
Exhibit 6-1
Exhibit 7-1
List of Text-boxes
Text-box 1-1
Text-box 1-2
Text-box 1-3
Text-box 2-1
Text-box 2-2
Text-box 2-3
Text-box 2-4
Text-box 2-5
Text-box 3-1
Text-box 3-2
Text-box 3-3
Text-box 4-1
Text-box 4-2
Text-box 4-3
Text-box 4-4
Text-box 5-1
Ecological Risk Assessment Framework 3
Eight-step Ecological Risk Assessment Process for Superfund . 7
Ecological Risk Assessment In the RI/FS Process 9
Analysis Phase 41
Risk Characterization Phase 43
Highlights of Region 10 Guidance 1
Ecological Risk Assessment Steps & Decision Points 4
Integrated Risk Assessment Deliverables in RI/FS Process .... 6
Risk Assessment Interim Deliverables During RI/FS Process . . 10
Steps Involved in Preliminary Ecological Risk Assessment ... 10
Steps in the Development of PRGs 14
Guidelines on the Presentation of PRGs Values 17
Other Issues Related to DQO Determination 17
Risk Assessment Interim Deliverables During Prelim. Phase . . 20
Ecological Risk-based Screening 24
Ecological Toxicity & Exposure References 25
Potential Sources of Ecological Effects & Toxicity Data 31
Components of the Work Plan & Sampling and Analysis Plan . 32
Suggested Measurement Endpoints 33
Characteristics of Assessment & Measurement Endpoints ... 34
Possible Toxicity Tests & Bioassays 39
IX
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
1.0 INTRODUCTION
As stated in the foreword, the
purpose of the Region 10 guidance is to
summarize important concepts from
national risk assessment guidance,
highlight steps of the Remedial
Investigation/Feasibility Study (RI/FS)
relevant to the risk assessment, and
identify specific deliverables that should
be submitted to Region 10 during
development of the baseline risk
assessment. Highlights of the Region
10 guidance are in Text box 1-1. The
anticipated users of the regional
guidance are project managers, who
need to identify stages of the remedial
process in which a risk assessor should
be involved, as well as technical staff
who write or review risk assessments.
Text Box 1-1 Highlights of Region 10
Guidance
Screening Level Ecological Risk
Assessment (Sections 3.4)
Baseline Ecological Risk Assessment
(Section 4)
Radionuclide Exposure Formulas and
Equations (Appendix A)
Ecological Benchmark Screening Values
(Appendix B)
Updated Resources and References
(Section 7.0)
• Technical Issue Papers Section
(Append ixC)
Case Studies Section (Appendix D)
Ecological Risk Assessment is a process that evaluates the likelihood that adverse
ecological effects may occur or are occurring as a result of exposure to one or more stressors
(EPA 1992a). Ecological risk assessment is an integral part of the Remedial Investigation and
Feasibility Study (RI/FS). The three components of the Remedial Investigation (Rl) process are:
(1) characterization of the nature and extent of contamination; (2) ecological risk assessment; (3)
human health risk assessment. The investigation of the nature and extent of contamination
determines the chemicals present at the site, as well as the distribution and concentration of the
chemicals. The ecological and human health risk assessments determine the potential for adverse
effects to the environment and human health, respectively.
The current EPA approaches to ecological risk assessments for Superfund are based on
the human health risk assessment format, but modified for the increased complexity of organisms
encountered and their interactions in the ecosystem. The purpose of ecological risk assessments
may vary within programs, but they generally serve to provide risk managers with an estimate of
the extent and magnitude of adverse effects on the ecosystem of concern.
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
The Region 10 supplemental guidance is a region-specific document that outlines the
process and tools used for conducting ecological risk assessments at Superfund sites. This
document borrows heavily from the EPA headquarters documents: Ecological Risk Assessment
for Superfund: Process for Designing and Conducting Ecological Risk Assessments (EPA 1996a),
the Proposed Guidelines for Ecological Risk Assessment (EPA 1996b), the Framework for
Ecological Risk Assessment (EPA 1992a), the Review of Ecological Assessment Case Studies
(EPA 1993b & 1994c) and other EPA regional ecological risk assessment documents. Exhibit 1-1
outlines the major components of the ecological risk assessment process.
1.1 Regional Technical Guidance
The region will issue an update to this guidance to address evolving risk assessment
technical issues. The Region 10 Risk Review will be released intermittently in response to
selected ecological risk assessment technical issues. It will be a separate publication from the
Region 10 Risk Assessment News, and will provide more in-depth, technical discussions than the
News. Issues of the Region 10 Risk Review will be placed under Appendix C, "The Tool Box," of
this document. Appendix D will similarly be comprised of special releases of the Region 10 Risk
Review which will focus on actual case studies related to ecological risk assessments.
This guidance is intended as a supplement to the upcoming EPA headquarters Ecological
Risk Assessment for Superfund: Process for Designing and Conducting Ecological Risk
Assessments (EPA 1996a). It focuses on issues related to Superfund sites in Region 10.
Furthermore, this document does not determine the scale of the ecological risk assessment or give
specific details about investigative techniques which may be used in the ecological risk
assessment. It provides the tools (e.g., toxicity bioassays) and examples (site-specific case
studies) that will enable risk assessors and site managers to make sound decisions which are
technically defensible and cost effective.
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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EXHIBIT 1-1
Ecological Risk Assessment Framework (U.S. EPA, 1992a)
Discussion
Between the
Risk Assessor
and
Risk Manager
(Planning)
Ecological Risk Assessment
PROBLEM FORMULATION
A
N
A
L
Y
S
I
S
Characterization
of
Exposure
Characterization
of
Ecological
Effects
RISK CHARACTERIZATION
Data Acquis
on, Verification and Monitoring
Discussion Between the
Risk Assessor and Risk Manager
(Results)
I
Risk Management
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
1.2 Focus of Risk Ecological Assessment
Text box 1-2 summarizes the
associated steps and the pert-inent
decision points and; Exhibit 1-2
outlines the eight-step ecolo-gical
risk assessment process for
superfund. Table 1-1 shows these
decision points in relation to
corresponding deliverables.
National Priority List (NPL)
sites in Region 10 vary in size from a
few acres to square miles, vary in
number and type of sources of
contamination, and vary in presence
of ecological receptors or in potential
for exposure to human populations.
The risk assessment process and
the report produced will not be
exactly the same for all sites, rather
the process will be modified as
needed for any site. Best
professional judgement (BPJ) of the
project manager, risk assessor, and
reviewers will always be used to determine the level of effort to be devoted to risk assessment and
to specific aspects of the risk assessment.
Text Box 1- 2 Ecological Risk Assessment
Steps and Decision Points
> Preliminary Problem Formulation and Ecological
Effects Evaluation.
> Preliminary Exposure Estimates and Risk Calculation
(DECISION POINT #1).
> Problem Formulation: Selection of Assessment
Endpoints and Development of Testable Hypothesis
(DECISION POINT #2).
> Development of Conceptual Model, Selection of
Measurement Endpoints and Study Design
(DECISION POINT #3).
> Site Assessments: Confirmation of Ecological
Sampling and Analysis Plan & Verification of
Exposure Pathways
(DECISION POINT #4).
> Field Investigations: Site Investigation Consistent
with Work plan.
> Risk Characterization.
> Risk Management (DECISION POINT # 5).
Ideally, the risk assessment process will be iterative, with results of early steps (scoping,
calculation of preliminary remediation goals, and screening steps) used to focus subsequent work
on information needed by decision-makers and on important chemicals, pathways, and issues.
For example, the RPM and risk assessor may find that not as much precision is needed in the
baseline risk assessment for a site where remedial action is clearly triggered, based on criteria in
the National Contingency Plan (NCP) (EPA 1990d) and the Role of the Baseline Risk Assessment
memo (EPA 1991e), although detailed analysis might go into setting remediation goals for such
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
a site. For a site where preliminary calculations show risks near the upper boundary of the risk
range, more effort and precise information for the baseline risk assessment might be needed to
support risk management decisions. Some NPL sites will be managed as multiple operable units,
or as projects of several phases, including early or interim actions, rather than with a single RI/FS.
Appropriate modifications of the risk assessment process to meet the needs of decision-makers
will be important for these sites (see Exhibit 1-3). Instead of a single "baseline" risk assessment,
the risk assessment deliverables might include one or more focused risk assessments, addressing
a single source area or medium. The focused risk assessment would be used to justify a specific
action. This type of approach is discussed in the guidance for CERCLA Municipal Landfills, on
pages 3-39 and 3-40:
...it may be possible to streamline or limit the scope of the baseline risk assessment
in order to initiate remedial action on the most obvious landfill problems...
Ultimately, it will be necessary to demonstrate that the final remedy, once
implemented, will address all pathways and contaminants of concern, not just those
that triggered the need for remedial action (EPA 1991 a).
Sites where early action or operable unit actions are taken based on focused risk
assessment or other criteria will later require a comprehensive risk assessment, considering all
sources, pathways, and contaminants, to justify final actions or "no further action" decisions. At
a partially remediated site, the risk assessment should evaluate the site in its present physical
condition. The RPM and risk assessor should decide how to factor ongoing actions into the risk
assessment.
1.3 Scheduling of Deliverables
The organization of this regional risk assessment guidance is consistent with the Region
10 Policy, Conduct of Remedial Investigations and Feasibility Studies (EPA 10, 1990). This
regional risk assessment guidance identifies certain items as risk assessment interim deliverables
which should be submitted in advance of the baseline risk assessment. Risk assessment interim
deliverables can be included as parts of the Site Characterization, Work Plan, and Preliminary
Data Analysis documents (see Text box 1-3), or may be submitted as separate technical memos,
according to the needs of the particular project. The EPA RPM will determine the specific
schedule of deliverables for a site. The information from interim deliverables will ultimately be
incorporated in the baseline risk assessment, elsewhere in the RI/FS, or as appendices to these
documents.
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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The intent of
requesting early submittal
of interim deliverables for
review is to facilitate the
progress of the risk asse-
ssment, to encourage dis-
cussion, and to clarify
reasoning in decisions
affecting risk assessment
and ultimately risk mana-
gement. Hence, the inte-
rim deliverables reques-
ted by region 10 relate to
decision points in the risk
assessment process (e.g.,
Which contaminants
potentially pose significant
concerns? What
exposure pathways are
involved?). Deliverables
are discussed here in the
sequence in which they
will be subm-itted, as
outlined in Text box 1-2.
Further discu-ssion of
scheduling of risk
assessment deliverables
is pro-vided in sections
1.1, 2.1, 3.1, 3.2 and 4.1.
Headquarters' guidance
(EPA 1991f) also addre-sses
party (PRP) will conduct the
Text Box 1- 3 Integration of Risk Assessment
Deliverables in RI/FS Process
Phase I. RI/FS Project Planning
Scoping
Conceptual Site Model (2.2)
Preliminary Remediation Goals (2.3)
RI/FS Work Plan
Outline of the Risk Assessment
Phase II. Preliminary Data Analysis / Site Characterization Summary
Evaluation of Site Contaminants and Natural
Background (3.2)
Risk-Based Screening of Contaminants (3.3)
Conceptual Site Model/Exposure Pathways (4.2.3)
Problem Formulation (4.2)
Ecological Endpoints Selection (4.2.4 & 4.3.1)
Phase III. Remedial Investigation and Feasibility Study Reports
Remedial Investigation Report
Baseline Risk Assessment (4.0)
Feasibility Study
Risk Evaluation of Remedial Alternatives (9.1)
Note: Bold items are risk assessment deliverables.
Parenthetical references indicate relevant sections of
this guidance document.
scheduling of deliverables for sites at which a potentially responsible
RI/FS but the EPA will conduct the risk assessment.
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
EXHIBIT 1-2
Eight-step Ecological Risk Assessment Process for Superfund
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E.E
o
O
STEP 1: PRELIMINARY
• Site Visit
• Problem Formujation
• Toxicity Evaluation
STEP 2: PRELIMINARY
• Exposure Estimate
• Risk Calculation
Risk Assessor and
Risk Manager
Agreement
o
.33
"o
O
1
Q
STEP 3: PROBLEM FORMULATION
Toxicity Evaluation
Assessment
End points
Conceptual Model
Exposure Pathways
Questions/Hypotheses |
STEP 4: STUDY DESIGN AND DQO PROCESS
• Lines of Evidence
• Measurement Endpoints
Work Plan and Sampling Analysis Plan
STEP 5: VERIFICATION OF FIELD
SAMPLING PLAN
STEP 6: SITE INVESTIGATION AND
DATA ANALYSIS
STEP 7: RISK CHARACTERIZATION
STEP 8: RISK MANAGEMENT
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Table 1-1 Decisions Points and Corresponding Deliverables
Section which concludes
with Decision Points
Decision to be Made
Deliverables
Preliminary Phase
Determine whether or not a
significant ecological threat
may exist.
Screening level risk calculations
Table of COPCs
Map of sample locations
Other relevant site maps
Problem Formulation
Agree on objective(s),
testable hypotheses and
selection of both assessment
and corresponding
measurement endpoints
Objective(s)
Testable Hypotheses
Suspected ecological effects of
COPCs
Endpoints table
Problem Formulation
(with Conceptual Site Model)
Agree on exposure
pathways, development of
conceptual site model, the risk
assessment Work plan,
sampling and analysis plan
(SAP), a site investigation and
methods of data analysis.
Conceptual Site Model
Draft Work Plan
Site Assessment
Agree on any changes,
resulting from information
from the field study, in the
Work Plan or SAP.
final Work plan and/or SAP
Risk Management
Determine and initiate
remedial actions for the site
and develop the Record of
Decision (ROD).
Baseline Ecological Risk
Assessment with: Remedial
Action Objectives (RAOs)
and Risk Characterization
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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EXHIBIT I-3
Ecological Risk Assessment in the RI/FS Process
[iF
FROM:
I • Preliminary Assessment
• Site Inspection
!• NPL Listing
Remedy Selection
Record of Decision
Remedial Design
Remedial Action
Remedial Investigation
WP
and
SAP Investigation
Establish Development
Remedial and Analysis
Objectives of Alternatives
SCREENING
ECOLOGICAL RISK
ASSESSMENT
PROBLEM
FORMULATION AND
STUDY DESIGN
ANALYSIS OF
EXPOSURE and EFFECTS
RISK CHARACTERIZATION
WP: Work Plan
SAP: Sampling and Analysis Plan
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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Text Box 2-1 Risk Assessment
Interim Deliverables During
RI/FS Project Planning
Conceptual Site Model (2.2)
Preliminary Remediation Goals (2.3)
2.0 RI/FS PROJECT PLANNING
The risk assessment information
considered in the RI/FS project planning is often
included in primary documents, such as a
scoping document and work plans (see Exhibit
1-3). The interim deliverables specified in Text
box 2-1 should be submitted for review in
advance of the larger documents, and the
information later incorporated into these larger documents (i.e., the baseline risk assessment). The
specific schedule is up to the discretion of the RPM. However, since both the finalized
Conceptual Site Model and the Preliminary Remediation Goals will impact the progress of the risk
assessment, these deliverables will correspond to decision points in the risk assessment process
and should be submitted in a timely fashion. For sites where the potentially responsible party
(PRP) will be conducting the RI/FS while an EPA contractor will be doing the risk assessment, it
will probably be necessary to submit separate risk assessment deliverables. For example, the risk
assessor will need the list of expected contaminants, submitted by the PRP, in order to prepare
preliminary remediation goals (PRGs). In turn, the exposure pathways from the conceptual site
model will have to be presented in time for the PRP to consider risk assessment data needs in
preparing the RI/FS work plan. (See also the directive on risk assessment for PRP sites (EPA
1991f)).
2.1 Steps 1 & 2: The Preliminary Phase
The components addressed within these two initial
steps are listed in Text box 2-2. These components
include site visit, preliminary problem formulation, toxicity
evaluation, exposure estimation and risk calculation. The
preliminary ecological risk assessment efforts involve the
first two steps (steps 1 & 2) of the ecological risk
assessment process. These first two steps are often
referred to as screening steps as it is during these steps
that the media, exposure pathways, receptors and
contaminants on which the risk assessment will focus are
selected and others are determined of lesser or no risk.
Text Box 2-2 Steps Involved in
Preliminary Ecological Risk
Assessment (Steps 1 & 2)
• Site Visit
• Preliminary Problem Formulation
• Toxicity Evaluation
• Exposure Estimation
• Risk Calculation
(See U. S. EPA 1996a for Details)
10
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
See Steps 1 and 2 of the EPA headquarters Ecological Risk Assessment for Superfund: Process
for Designing and Conducting Ecological Risk Assessments (EPA 1996a), for a full description of
these components. Ecological risk assessment is an iterative process which mandates
increasingly specific levels of investigations as data are acquired. The preliminary process must
be thorough in its scope, but not overly detailed. Overly detailed screening can encourage limited
areas of focus; and this step should provide a complete picture of all potential ecological concerns
present at the site. If available information indicates the need for further investigations, such
should be conducted within the following ecological risk assessment process.
2.2 Conceptual Site Model
The Site Characterization Document, or another document used during the scoping stage,
should present and discuss a conceptual site model for both current and potential future site use.
This should be in the form of a flow chart showing site characteristics, including contaminant
sources, release mechanisms, transport routes, receptors, and other information as appropriate.
Iterations of this model will be carried through the work plan and baseline risk assessment report.
As stated on page 2-9 of the Guidance for Conducting Remedial Investigations and Feasibility
Studies (RI/FS guidance) (EPA 1988b):
The conceptual site model should include known and suspected sources of
contamination, types of contaminants and affected media, known and potential
routes of migration, and known or potential human and environmental receptors.
This effort, in addition to assisting in identifying locations where sampling is
necessary, will also assist in the identification of potential remedial technologies.
A generic conceptual site model diagram taken from the RI/FS guidance is presented as figure
2-1. This may be used as a starting point, although other effective formats, graphical or pictorial,
are possible, for example figures 2-2. The generic model should be modified to include as much
site specific information as possible. Text accompanying the diagram should sufficiently address
specific sources and receptors at the site.
The development of the conceptual site model will provide a basis for preliminary
identification of exposure scenarios to be evaluated in the baseline risk assessment. If possible,
human and ecological components of the conceptual site model should be shown in a single
diagram. This will allow both the risk assessor and the risk manager to put potential ecological
11
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
threats in perspective as well as to avoid redundancy in evaluating the different components
connected with the ecological threat (e.g., contaminant uptake by fish which may become prey
items for Bald Eagles). Ecological exposure scenarios are discussed in the Wildlife Exposure
Factors Handbook (EPA 1993a).
A written presentation of ecological exposure scenarios and pathways that will be
evaluated in the risk assessment should be prepared during RI/FS planning. The exposure
scenarios and pathways will be used in developing the work plans so that risk assessment data
needs are addressed. Selection of exposure pathways will rely heavily on the conceptual site
model.
Presentation of selected exposure pathways may simply be notes or text accompanying
the conceptual site model, and should include reasoning for including and excluding various
pathways. Discussion of exposure scenarios may, when appropriate, be accompanied by site
maps showing locations of sources and receptors, or can refer to maps in the scoping report or
work plan.
Identification of exposure scenarios and pathways at this stage in the process may be
detailed, or may be more general, depending on the amount of information about the site available
from the scoping process. Scenarios and pathways may be modified as more information is
collected during the Rl. Due to the increased complexity of the ecosystem and the interaction of
organisms, the ecological exposure pathways and scenarios present may be more complex than
the human health exposure pathways. Hence, to clearly communicate the potential ecological
exposure pathways present at the site without excessive detail regarding the various components
of ecosystem interactions that may occur at the site, it may be helpful to discuss the different
components of the ecosystem that will become the backbone of the conceptual site model and
ecological assessment endpoints. The final version of the exposure scenarios and pathways
presentation will appear again in the exposure assessment section of the baseline risk
assessment.
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Figure 2-2 Schematic Conceptual Site Model
2.3 Preliminary Remediation Goals
Preliminary remediation goals (PRGs) are
categorized in two ways: (1) ecological and human
health endpoints, and (2) risk-based (e.g. RBCs)
and regulatory (e.g. ARARs). The latter separation
is not always distinct (e.g., some regulatory levels,
such as AWQC, may be established from risk-based
analyses). Regardless of the source of a potential
ARAR, it should be accompanied by a description
noting whether it is based on ecological or human
health protection and whether it is a regulatory value
and/or a risk-based value. It is important that as
Text Box 2- 3 Steps in the
Development of PRGs
List expected contaminants
Identify potential ARARs
- determine applicable sources
- calculate "risk at ARAR"
Identify RBCs
- assemble toxicity Information
- compile/calculate RBCs
Present information in a table
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much information available for both ecological and human heath threats be presented in this
context.
Steps involved in developing PRGs are presented in Text box 2-3. Values for a limited
number of contaminants, which take into account the additional transport pathway of migration of
contaminants in soil to groundwater, may be found in the So/7 Screening Guidance (EPA 1994b).
Ecological risk information may be found in a variety of reference materials, such as those listed
in Text box 3-3, so it is essential to clearly cite sources. Other references for ecological values
may be found in section 10. The Regional Policy on Conduct ofRI/FS (EPA 10 1990) emphasizes
that preliminary remedial action objectives be developed at the initial scoping group meeting.
The primary function of the completed PRG table will be to anticipate the range of risk-
based concentrations that may become goals for site clean up action. Early consideration of
these numbers allows planning and evaluation of remedial alternatives to begin before the
remedial investigation report and baseline risk assessment are complete. It is expected that the
PRG table will also be referred to by managers and technical personnel at various stages of the
RI/FS process, for various purposes. An important use is evaluation of adequacy of analytical
methods to provide data for risk assessment: method detection/quantitation limits can be
compared to risk-based concentrations. Also, as Rl data become available, actual concentrations
of contaminants in site media can be compared to risk-based concentrations to identify
contaminants of concern for sampling in subsequent phases. The risk-based concentrations will
also be used in screening contaminants for the baseline risk assessment.
2.3.1 List Expected Contaminants
The first step in developing PRGs is to assemble a list of potential site-related
contaminants. Based on the site history, and on analytical results from Site Investigation,
Preliminary Assessment, or other sampling efforts prior to the Rl, a list of chemicals expected or
known to be present can be compiled. Resource materials identifying contaminants expected to
be associated with specific industries or sources can be consulted. (Resources include Appendix
II of the Data Useability Guidance (EPA 1990b) and guidance for specific categories of sources.)
A written discussion of site information used to obtain the list of contaminants should be provided
and the discussion should be part of the scoping document or conceptual site model, or may
accompany the table of PRGs. The list may be long for sites with multiple source areas.
Chemicals may be added to or deleted from the list as additional information becomes available
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during the Rl.
2.3.2 Identify Potential ARARs
Chemical-specific standards for soil, water, and air, as specified in federal or state
regulations that may become ARARs, are identified for each potential contaminant. (ARAR
guidance is provided in EPA 1988a). In the interest of limiting effort during scoping, the RPM may
determine that identification of the obvious federal standards, Maximum Contaminant Levels and
Maximum Contaminants Level Goals (MCLs and MCLGs) for water and Ambient Water Quality
Criteria (AWQC) for surface water, is sufficient at this stage. Note that ARARs under the
Washington State Model Toxics Control Act (MTCA) (WDOE 1991) include some concentrations
defined in the regulation, and some concentrations calculated using toxicity information. If toxicity
information is not available for contaminant(s) in question, therefore, a quantitative structure
activity relationship (QSAR) type of approach may be used. The use of QSAR approach to
estimate toxicity to aquatic organisms is described by EPA's Office of Toxic Substances (EPA
1988f).
*
2.3.3 Identify Risk-based Concentrations
Ecological risk-based screening values are available for many contaminants. Ecotox
threshold values are listed in a recent EcoUpdate (EPA 1996c), but when using these values, care
should be taken to insure that they are adequately conservative for site-specific conditions. Also,
screening values may be found in the literature as well as many of the resources listed in Text box
3-3. (See also sections 3.3 and 4.2.)
Note that risk-based concentrations provided in Attachment 1 do not protect for ecological
effects, migration of contaminants to groundwater or inhalation exposure pathways. Soil characteristics,
geological and meteorological conditions at the site, as well as chemical and physical properties of
contaminants affect their fate and transport. These factors, along with site use, determine the relative
importance of various routes of release, receptors of concern and exposure pathways (release to air,
migration to groundwater, incidental ingestion, dermal contact) in determining risk-based goals for soil.
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2.3.4 Present PRG Information in a Table
The risk assessor should gather information,
perform necessary calculations and present
information, separated by media (soil, groundwater,
surface water, and sediment) in tabular form in
accordance with guidance provided in Text-box 2-4.
Up-front agreement with the RPM on which risk-
based PRGs will be used for comparison and risk
characterization purposes in the risk assessment is
essential in order to avoid unnecessary backtracking
at later stages of the risk assessment. Although
ARARs are not part of the baseline risk assessment,
it is often useful for some of the management-
related purposes noted below, to present these
numbers together with the risk-based concentrations.
Text Box 2- 4 Guidelines on
Presenting PRG Values in
Tabular Format
Contaminant exposure point
concentrations,
Regulatory PRG(s) (ARARs) for
each pathway of concern,
Risk at ARAR(s) (ecological
risk-based), and
Risk-based PRG(s) (RBCs) for
each pathway of concern.
2.4 Consideration of Risk Assessment Data Needs in the Work Plan
Sampling and analysis activities undertaken during
the remedial investigation should provide adequate data
to evaluate all potential and appropriate exposure
pathways, and chosen ecological endpoints for the risk
assessment. The sampling plan should be designed
keeping in mind how the data will be used, and how it will
affect the risk assessment. Therefore, the risk assessors
must be involved in the development of data quality
objectives related to the risk assessment. Development
of data quality objectives (DQO) is not limited to concerns
for the precision, accuracy, representativeness,
completeness and comparability of the data. Text-box 2-5
outlines other issues that are related to Data quality
objectives. Specific risk assessment aspects of data
quality objectives are discussed in the subsections below.
Text-Box 2- 5 Other Issues
Related to DQO Determination
Types of laboratory analysis
used,
Sensitivity of the analytical
technique,
Detection limits,
Confidence limits, and
The resulting data quality
(ATSDR, 1994).
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2.4.1 Use of Sampling Data for the Risk Assessment
The work plan should show that the data needed to evaluate each exposure pathway
identified for the site will be collected. In the section of the work plan that discusses the risk
assessment, the association of each pathway with specific samples should be spelled out. The
information provided should answer the following types of questions: Will groundwater
concentrations be averaged over time for risk assessment? If so, how many rounds of data will
be collected? Are ecological receptors chosen for evaluation/monitoring found in adequate
numbers at the site? Will soil samples be averaged or composited to describe an area? Will
exposures to soil be considered using samples taken at the surface, at depth, or both? Were
locations for soil samples selected using a random, systematic, or other designs? Are sampling
plans adequate to distinguish site contamination from natural background?
For pathways and receptors that will be evaluated using estimates of potential release
and/or models of fate and transport, specific models chosen for the site assessment should be
identified in the work plan. The Framework for Ecological Risk Assessment (EPA 1992a) and
other EPA documents provide guidance on selection of models. Physical data needed for
model(s), such as meteorological data or soil data, should be identified, and appropriate methods
to be used in data collection should be included in the sampling plan.
2.4.2 Analytes and Detection Limits
Selection of analytical methods involves consideration of many site-specific factors,
including site history and contaminants. The RPM, chemist and risk assessor should evaluate the
advantages of available methods. Appendix III of the Data Useability Guidance (EPA 1990b)
compiles information on various analytical methods and detection limits, listed by chemicals.
Information gathered during the scoping process, particularly RBCs and PRGs for expected site
contaminants, should be consulted when choosing methods. For samples that will be used to
establish exposure point concentrations for risk assessment, results are more useful if detection
limits meet risk-based concentrations. The adequacy of detection limits should be evaluated in
the work plan by presenting a table listing expected contaminants and comparing the method
detection or quantitation limit for each compound with the appropriate risk-based goal for that
chemical in that medium. This does not mean that every sample must be analyzed with the
method achieving the lowest possible detection limits. For example, at locations where
concentrations are known or expected to be high, the most sensitive method may not be
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necessary.
3.0 Preliminary Data Analysis
Extensive discussion on evaluation of data for use in risk assessment is provided in the
Data Useability Guidance (EPA 1990b). Judgement regarding the needs of a particular project
should be used in interpreting this guidance. At many Superfund sites, several chemicals are
detected in site media. The ecological threats posed by these contaminants vary in degree and
distribution. Some contaminants, often referred to as the "drivers" will pose greater and/or more
threats than others, and will steer the direction of the risk assessment. Elimination from the
baseline risk assessment of common laboratory contaminants, natural background elements, and
chemicals that pose minimal risk should be conducted in a systematic manner, as presented in
sections 3.2 and 3.3 below, or using other acceptable rationale approved by EPA Region 10. It
is suggested that this step be carried out in advance of the baseline risk assessment.
3.1 Scheduling of Risk Assessment Deliverables During Preliminary Data Analysis
Section 3 describes the content of deliverables, listed in Text box 3-1, that will be submitted
after Rl sampling results are available but before the RI/FS and baseline risk assessment are
submitted. All of the information called for in section 3 can be compiled and submitted to the RPM
in one package, along with other data reports, if convenient.
The timing and length of these deliverables will vary depending on the needs of the site.
If additional sampling events will be planned based on results of early rounds, timely reporting of
risk-based screening and revised exposure scenarios will be important. These should be
submitted as soon as possible after data are available. Risk-based screening can also be used
to identify unusually high risks, for which the RPM might want to consider early action.
Documentation of the logic used in reducing the number of contaminants to be carried through the
baseline risk assessment must be included in the final risk assessment. This can be accomplished
by including a copy of the risk-based screening and other deliverables from the preliminary data
analysis as an appendix to the baseline risk assessment.
For some projects the preliminary data analysis deliverables may be omitted entirely. This
may occur when previously agreed-upon schedules do not allow for additional rounds of document
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Text Box 3-1 Risk Assessment Interim Deliverables
During Preliminary Data Analysis
• Evaluation of Site Contaminants and Natural
Background (3. 2)
Risk-based Screening of Contaminants (3.3 )
Revised Conceptual Site Model/Exposure Pathways
(4.2.3) & (4.2.5)
Revisions to Work Plan (4.3)
Problem Formulation (4.2)
Ecological Endpoints Selection (4.2.4) & (4.3.1)
review. Also, some of the
interim deliverables called for
below may not be necessary if
no additional sampling is antici-
pated, and if the conceptual
site model and identification of
exp-osure scenarios and
pathways in the work plan are
acceptable and do not require
revision. In these cases, the
information called for in section
3 below will be submitted as
part of the baseline risk
assessment. The Region 10
risk assessment staff does not ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^™
recommend skipping the "Risk-
based Screening" and "Revised Conceptual Site Model/Exposure Pathways" interim steps. The
potential problem is that if risk-based screening and specific exposure and toxicity information is
not submitted and approved, gaps will be carried through the baseline risk assessment. For PRP-
lead sites, the specifics of the schedule may be different. Rl sampling results should be provided
as a deliverable to the risk assessor before the risk assessment data analysis tasks can proceed.
3.2 Evaluation of Site Related Contaminants and Natural Background
Differentiation of background concentrations from site- related contaminants are necessary
for the identification of COPCs and also for the characterization of nature and extent of
contamination in the ecological risk assessment. To determine the type of risk posed by site
contaminants, it is necessary to compare contaminant levels to background concentrations.
Comparison with natural background levels should only be used for inorganic chemicals, because
organic chemicals found at most Superfund sites do not occur naturally (even though they may
be ubiquitous). The presence of organic chemicals in background samples may be an indication
that samples were collected in an area influenced by the site. Unless a strong case can be made
for the naturally occurring organics, these chemicals should not be excluded from evaluation in
the ecological risk assessment.
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3.2.1 Site Related Contaminants
Chemicals reliably associated with site activities based on historical information whose data
are of sufficient quality should be retained and evaluated in the risk assessment. However, certain
organic chemicals (for example, acetone, toluene, methylene chloride, 2-butanone and the
phthalate esters) are commonly used in the laboratory which may be introduced into the sample
due to cross contamination that are not from the site, should be excluded from the risk
assessment (See RAGS Part A, HHEM, Chapter 5 for details).
3.2.2 Natural Background
Determining whether detected concentrations of inorganics represent natural background
in a medium is a site-specific issue. Appropriate number and locations of background samples
are determined by the RPM and geologists. Interpreting site data compared to background data
should be discussed among project managers and scientists and addressed in the Rl report. If
it is unclear at the time the preliminary data analysis is conducted whether inorganics are natural
or anthropogenic in origin, they should be carried through the baseline risk assessment, with
further consideration of the issue of background in the FS. Although natural background elements
may be excluded from the baseline risk assessment, at some sites the risk from natural
background elements may be included in the baseline risk assessment, presented separately from
the site-related risks, at the option of the RPM. Further discussion regarding the application of
background concentrations to ecological risk assessments may be found in Appendix C and in
other relevant documents listed in sections 9 and 10.
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Figure 3 -1. Selection of Contaminants of Potential Concern
(COPCs)
SUSPECTED CONTAMINANTS
Data Useability Review
- Analytical Methods
- Detection Limits
- Detection Frequency
- Quality Control
QA REVIEW OF SITE CONCENTRATIONS
Contaminants
Detected
No Detection
Comparison to Background
- Inorganics
- Radionuclides
- Organics
Address
Implications in
Risk
Characterization
SITE CONCENTRATIONS
VS.
BACKGROUND CONCENTRATIONS
Site Concentration >
Background Concentration
Site Concentration < Background Concentration
Comparison to Reference Values
- EPA Ambient Water quality Criteria
- Sediment Quality Guidelines
- IAEA Criteria
Address
Implications in
Risk
Characterization
SITE CONCENTRATIONS
VS
RISK-BASED CONCENTRATIONS (RBCs)
Site Concentration > RBCs
Site Concentration < Risk -Based Concentration
CONTAMINANTS OF POTENTIAL CONCERN
Address
Implications in
Risk
Characterization
PROBLEM FORMULATION
Adapted from INEL, 1994
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3.2.3 Identification of Contaminants of Concern (COPCs)
The screening of contaminants should compare the maximum concentration of each
contaminant detected at the site to a risk-based concentration calculated using a conservative
target risk, based on values derived from toxicity studies and exposure scenarios. Figure 3-1 is
provided to illustrate the selection process. At this stage the list of contaminants which was
initiated in the screening stage of the risk assessment, must be finalized utilizing all available data.
Some factors to consider when establishing this list include: environmental concentrations in all
media, frequency of occurrence, background levels, bioavailability, physical/chemical properties,
potential for bioaccumulation or bioconcentration, potency and organism-experienced effects (EPA
1989b). Once the above information has been gathered, the type of analysis to be performed
should be determined. The risk assessor may also re-evaluate each contaminant eliminated, to
insure that cumulative hazard is not overlooked. Basic steps of this process are outlined in Text
box 3-2.
3.3 Ecological Risk-based Screening
Ecological screening process includes the identification of contaminants of potential
concern. Text box 3-2 outlines the ecological screening process. Unlike the human health risk
assessments for which the receptor is implicit to the process, in ecological risk assessment the
receptor(s) are not preselected. Hence, the ecological screening process involves the initial
identification of both contaminants and receptors. The risk assessment is focused on those
contaminants that may pose significant threats to the ecosystem. Therefore, the risk-based
screening will indicate whether or not any potential threats to ecological components exist at the
site. Contaminants found at concentrations not indicative of significant threat to the ecosystem
should be eliminated and no longer evaluated in the ecological risk assessment, but should be
retained for risk characterization. The uncertainty section of the risk characterization phase should
analyze the uncertainty about the predicted risk(s) [or lack of] from such contaminants.
The first phase of the screening revolves around potential exposure pathways and
transport mechanisms identified earlier in the Rl. All potential pathways identified should be
discussed: incomplete pathways should be documented as such; pathways which may exist, but
are not yet confirmed, should be listed as such, with specific detail regarding the unconfirmed
points on the pathway; and, complete pathways should be listed, detailing each step of the
pathway and how it was confirmed. The second stage of the screening level relies on
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comparisons and
calculations. Site
concentrations must
be measured and
toxicity values for
corresponding
contaminants
determined. Ecolo-
gical toxicity values
may be found in the
literature as well as
many of the refer-
ences listed in Text
box 3-3. For the
many contaminants
for which ecological
risk-based concen-
trations are not av-
ailable, toxicity re-
ference values must
be determined and
subsequent hazard
calculations execu-
ted. See section
1.3 (Step 1) [Scree-
ning-Level Ecolog-ical Effects Evalu-ation] of EPA head-quarters' Ecological Risk Assessment for
Superfund: Process for Designing and Conducting Ecological Risk Assessments (EPA 1996a) for
preferred ecotoxicological screening values.
The risk-based concentrations and toxicity reference values will then be used for
comparison with site concentrations. The risk-based numbers calculated for the screening
process should be conservative and will be modified during the subsequent steps as more site-
specific and less uncertain parameter data become available. Section 4.7.1.3 outlines toxicity
calculations to be used in risk-based screening of site-related contaminants. Also, see Step 2
(Screening-Level Exposure Estimates and Risk Calculation) of EPA headquarters Ecological Risk
Text Box 3-2 Ecological Risk-based Screening
CONTAMINANTS
List maximum concentration of each chemical in each medium.
Compare to risk-based concentration
Eliminate chemicals if
concentration exceeds screening concentration for given
medium
OR
HQ<1 and all relevant Hls<1.
Carry remaining chemicals through baseline risk assessment.
RECEPTORS
List all potential ecological receptors and receptor groups.
Determine if complete exposure pathways exist for each source
medium of concern.
Eliminate receptors/receptor groups if all relevant exposure
pathways for each medium of concern are incomplete.
Carry remaining receptors through baseline risk assessment.
NOTE: Under the summary presented in risk characterization all
contaminants and receptors must be presented along with rationale for
eliminations made during screening.
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Assessment for Superfund: Process for Designing and Conducting Ecological Risk Assessments
(EPA 1996a).
A table presenting site-related contaminants, site contaminant concentrations and toxicity
values, accompanied by a site map indicating sampling sites, should be included in the screening
stage interim deliverable to the RPM.
At the conclusion of the screening stage of the risk assessment, the results should be
submitted to the remedial project manager. The results submitted must include a list of all
contaminants present at the site. A table should be provided, giving the following information for
each contaminant in all corresponding media. Table 3-1 is presented as an example. A site map
indicating sampling sites and
location should accompany the
table. Additional site maps
showing the spatial distribution of
particular contaminants of concern
at the site should be provided only
if they further elucidate site
conditions.
Background data may be
employed in the screening process
to determine which site-related
contaminants, particularly inorg-
anics, exist on site at concen-
trations elevated above
surrounding natural background
levels. Plann-ing for background
sampling should occur early in the
Rl. The collection and use of soil
background data for ecological risk
assessments is discussed in
Appendix C; other relevant
references are also listed in
Appendix C.
Text Box 3- 3 Ecological Toxicity and Exposure
References
USFWS Contaminant Hazard Reviews (e.g. Zinc
Hazards to Fish, Wildlife, and Invertebrates: Asynoptic
Review. Fish and Wildlife Service, US Department of
the Interior. Biological Report 10; Contaminant
Hazard Reviews Report 26: April 1993. )
AWQC values (e.g., Ambient Water Quality Criteria
for lead EPA 440/5-84-027, 1985)
NOAA Screening Guidelines (NOAA Homepage)
AQUIRE database (EPA Ecotoxicology Data System)
Wildlife Exposure Factors Handbook (EPA 1993a)
Current ECO Updates (EPA 1996c)
Summary of Guidelines for Contaminated Sediments
(WDOE, Publication #95-308)
Screening Benchmarks for Ecological Risk
Assessment (Oak Ridge National Laboratory)
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Table 3-1
Sample Summary Table for Contaminants of Concern
(after initial risk-based screening)
Contaminants
Maximum
Detected
Levels
(PPb)
Risk-
Based
Cones
(PPb)
Frequency of
Samples
Exceeding
Screening Criteria
Background
Values
(PPb)
Frequency of
Samples
Exceeding
Background
Inorganics
Arsenic
Chromium
Lead
Nickel
4.73
3050
18.1
453
0.038
180
NA
730
41/57
4/57
1/57
0/57
3.4
4
5
5
4/57
7/57
4/57
16/57
Organics
1,1,2,2-
Tetrachloroethane
Chloro methane
Bis(2-
ethylhexyl)phthalate
Trichloroethene
Chloroform
Dibromo-
chloromethane
0.2
7.5
170
7
0.5
0.5
0.052
1.4
4.8
1.6
0.15
0.13
1/101
8/95
11/101
9/101
7/101
1/101
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Pesticides/PCBs
Aldrin
Aroclor 1254
Dieldrin
DDT
0.08
1.18
0.01
0.4
0
0.01
0
0.2
3/82
3/101
2/101
1/101
NA
NA
NA
NA
NA
NA
NA
NA
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The contaminant portion of the screening process is somewhat prescriptive; the screening
process for receptors, although somewhat complex, is not so established. Receptor screening
should simply identify potential receptors and/or receptor groups on site. The first step is to
catalog the plants and wildlife on the site. The second, is to determine which of these organisms
may be exposed to the contaminants, via any exposure pathway(s), at the site.
Screening may be organized by species or functional groups or even by specific
populations. It should be well documented, allowing for tracking of those organisms determined
not to be potential receptors as well as those which are. Assistance from local plant and wildlife
experts may help to identify less common receptors. The end result of this process should be a
compilation of potential receptors, species or groups and justification for each determination
provided. This compilation of potential receptors, species or groups should assist in the
development of the conceptual model for the site.
At the conclusion of the ecological risk-based screening, an interim deliverable should be
submitted to the remedial project manager (RPM). The deliverable should list all contaminants of
concern present at the site, site concentrations of these contaminants, the toxicity and/or
background data used in the screening, the source of this data and the number of site
concentration exceedances above the chosen screening value. For contaminants found to be
elevated only in certain areas (hot spots), a map identifying these areas should be provided. Also,
a list of potential receptors and identified (complete) exposure pathways should be provided.
Relevant concentration-based distributional maps which illustrate fate and transport and/or
exposure pathways for selected contaminants should also be included.
4.0 BASELINE ECOLOGICAL RISK ASSESSMENT
4.1 Introduction
The methodology recommended for use in developing the baseline ecological risk
assessment is described in the Risk Assessment Guidance For Superfund, Volume II,
Environmental Evaluation Manual (EPA 1989c). Additional guidance for ecological risk
assessment can be found in the following EPA publications: Framework for Ecological Risk
Assessments (EPA 1992a), Ecological Risk Assessment for Superfund: Process for Designing and
Conducting Ecological Risk Assessments (EPA 1996a) and the Proposed Guidelines for
Ecological Risk Assessment (EPA 1996b).
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4.1.1 Chapter Objective
This chapter covers all aspects of step 3 in the eight-step process outlined in the EPA
headquarters Superfund ecological risk assessment guidance (EPA 1996a). While the baseline
ecological risk assessment report is the final deliverable for the risk assessment, a set of interim
deliverables may be crucial in conducting an effective ecological risk assessment. Such interim
deliverables can help to insure that all parties involved in the risk assessment are in agreement
at certain critical decision points, and thus prevent backtracking to these points at later times when
it becomes clear that differences of opinion exist.
4.1.2 Roles of Parties Involved in the Ecological Risk Assessment
Decisions regarding the risk assessment for a given site should be made by the remedial
project manager (RPM) for that site. The RPM will also serve as the liaison between the contractor
performing the risk assessment and the EPA risk assessment staff. Prior to the decision-making,
the RPM may establish a Biological Technical Assistance Group (BTAG) for consultation. In
Region 10, a BTAG is an ad hoc group comprised of members invited to serve by the RPM;
Region 10 BTAGs are specific to given sites or projects. A BTAG usually consists of EPA staff
specializing in environmental sciences, ecology and ecotoxicology as well as individuals
representing the trustees such as the U.S. Fish and Wildlife Service (USFWS), the National
Oceanic and Atmospheric Administration (NOAA) and related state agencies (e.g.,WDOE). These
members function in an advisory and review capacity to assist the RPM with the risk assessment
process. The RPM may consult with specific EPA staff members as well as the BTAG team, if
one has been established. Communication between the contractor and/or risk assessor with the
BTAG is essential in the ecological risk assessment process. This open line of communication
will help generate agreement and consistency among all parties involved.
4.2 Step 3: Problem Formulation
Problem formulation at Step 3 should involve the following activities:
• Refining preliminary list of COPCs;
• Further characterization of ecological effects;
T(See EPA 1996a, for details).
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• Review and refinement of contaminant fate/transport, exposure pathways and
ecosystems potentially at risk;
• Selection of assessment endpoints; and
• Refinement of Conceptual Site Model and development of testable hypotheses or
questions that the site investigation will address.
4.2.1 Refining Preliminary List of COPCs
Because of the conservative nature of the screening phase, some of the Initial list of
contaminants identified or suspected to be site related in Steps 1 and 2 should be re-evaluated
to eliminate those that pose negligible ecological risk. The risk assessor at this stage should
review the assumptions used in the screening phase and compare them to literature values. For
example, if 100 percent bioavailability was used in the screening phase and literature values
report only 65 percent, then the change in percent bioavailability should affect the HQ. Those
contaminants with HQs below 1 should be considered for elimination from the risk assessment
(the risk assessor should discuss this with the risk manager before reaching any conclusion).
4.2.2 Further Characterization of Ecological Effects
Literature search used in the screening phase should be expanded to obtain additional
information needed for the baseline risk assessment. Procedures for further characterization of
ecological effects are outline in the EPA Headquarters guidance (EPA 1996a).
4.2.3 Review and Refinement of Contaminant Fate/Transport, Exposure Pathways and
Ecosystems Potentially at Risk
These activities involve compiling additional data on:
• Environmental fate/transport of contaminants;
• Ecological setting at the site (habitat and potential receptors);
• Magnitude and Extent of Contamination (spatial and temporal scales).
Procedures for review and refinement of contaminant fate/transport, exposure pathways and
ecosystems potentially at risk are outline in the EPA Headquarters guidance (EPA 1996a).
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4.2.4 Selection of Assessment Endpoints
Selection of assessment endpoints for the baseline risk ecological assessment must be
based on the ecosystems, communities and species observed at the site. This selection should
take into consideration the following:
• Concentration of contaminant present in media of concern
• Toxicity mechanisms of contaminants to potential receptors at the site
• Susceptibility of receptors to contaminants at the site
• Existence of complete exposure pathways to potential receptors
4.2.5 Refinement of Conceptual Site Model and Development of Testable Hypotheses
Refinement of the conceptual site model will help to identify additional data requirements
which may influence the model. The conceptual model should provide a functional framework for
evaluating potential exposures of ecological receptors using or inhabiting the site.
Ecological receptors are those organisms that may be currently exposed to contaminants
at the site or may be exposed in the future. Those species that occupy a niche considered
fundamental to the function of the larger ecosystem should be documented clearly as such within
the risk assessment report. Site-specific ecological receptors of concern can be selected for a site
according to the following hierarchy of considerations. First, the receptor should be exposed,
directly or indirectly to the contaminants, as the assumption is usually made that an organism not
exposed to a given contaminant is not at risk from that contaminant. Second, changes in the
community structure, as marked by standard indices, when linked to exposure, may indicate
changes in potential receptors. Third, if a prey organism serves as a source of exposure to
predators (based on body burden and sample model), the predators may also be potential
receptors on the food chain.
Although individual changes may sometimes be considered significant when threatened
or endangered species are among the receptors, ecological risk assessments focus on effects to
the overall ecosystem at the site (e.g., such as population changes). Impact on critical species
on the food chain structure can affect the entire ecosystem. While organisms higher in trophic
levels often attract the most attention, effects of contaminants on lower trophic levels (e.g.,
decomposers, detritus feeders) must also be considered. For example, a contaminant may be
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toxic to microorganisms at very low concentrations, and if microbial or invertebrate populations are
disrupted, decomposition of dead plant and animal matter may not occur. This in turn, may reduce
the mineralization process needed to sustain the plant community. Eutrophication may also result
from similar mechanisms in the aquatic system, causing the depletion of oxygen that is vital for
aquatic life forms.
A complete exposure pathway includes a source, a mechanism of contaminant release,
retention and/or transport influences, a biotic exposure point, and an exposure pathway at the
ecological exposure point. Only complete pathways are expected to produce a significant
exposure to the receptors. All exposure pathways documented in the risk assessment should be
accompanied by a related description of the aforementioned properties. These pathways will help
to determine appropriate measurements for evaluation of chosen assessment endpoints.
4.2.6 Literature Search
Literature must be the pri-
mary source of data at some point
before finalizing the risk asses-
sment. Therefore, the search should
be conducted as soon as the
problem formulation phase is
completed. In fact, it should be
started during the screening phase
of the risk assess-ment. Inadequate
literature searches can result in
unnecessary toxicity testing as well
as delays in the over-all process due
to a lack of data. Literature search
may provide ecolo-gical effects data
for particular conta-minants and
species. Possible sources of
ecological risk-based values such as LD50s, LC50s, NOAELs and LOAELs are listed on Text box
4-1. Data obtained from the search can be compared to site-specific data, to fully characterize
associated risks from a site (EPA 1989b). At the conclusion of the literature search, data gaps
may be identified, therefore, it should be decided at this point whether toxicity tests and field
Text Box 4-1 Potential Sources of
Ecological Effects &Toxicity Data
primary literature
Registry of Toxic Effects of Chemical Substances
Hazardous Substances Database
Radiotoxicological Benchmarks for Wildlife at Rocky Flats
Agency for Toxic Substances and Diseases Registry
Phytotox Database
Aquatic Information Retrieval (AQUIRE)
Chemical Evaluation Search and Retrieval System
Fish and Wildlife Service Contaminant Hazard Reviews
Oak Ridge National Laboratory Screening Values
Washington State DOE Sediment Screening Values
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studies are needed. 4.3 Step 4: Selection of Study Design & Data Quality Objectives
Text Box 4-2 Components of the Work plan &
Sampling and Analysis Plan
The Work plan (WP): Assessment endpoints, exposure
pathways, questions (testable Hypotheses), define the
relationship between measurement endpoints and
assessment endpoints, and uncertainty analysis.
The Sampling and Analysis Plan (SAP): Data needs,
study design that is scientifically feasible, study methods
and sampling techniques, data reduction and quality
assurance.
The problem formulation
step (step 3) concludes with the
development of the conceptual
model which includes assessment
end-points, exposure pathways
and questions to be addressed in
the risk assessment (see Section
3.6.2 of EPA 1996a, and Text-box
4-2, for more details). Step 4 of the
ecological risk assessment estab-
lishes what the measurement end-
points should be, followed by the
study design and what type of data
will be need to address the risk question (hypotheses). The product of this step (Step 4 ) is the
Work plan (WP) and sampling and analysis plan (SAP) for the risk assessment. Any additions or
changes necessary for conducting the specialized tasks indicated in the Work plan should be
determined.
4.3.1 Selection of Measurement Endpoints
A good measurement endpoint will have a clear relationship to an assessment endpoint
and should be predictive of the assessment endpoint. Measurement endpoints must be
"measurable" using practical and economic means; and they must be appropriate to all relevant
considerations including the scale of the site, the exposure pathway of concern, and the time scale
of concern (EPA 1989e). More details regarding characteristics of good endpoints can be found
in Chapter 2 of Ecological Assessment of Hazardous Waste Sites (EPA 1989e). Text box 4-3 lists
potential measurement endpoints. Notice that the list of assessment endpoints is essentially a
subset of the list of measurement endpoints, which includes more specific qualities such as
characteristics of "individuals".
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4.3.2 The Relationship Between Measurement Endpoints and Assessment Endpoints
Text Box 4-3 Suggested Measurement Endpoints
Community
Number of species
Species evenness/dominance
Species diversity
Pollution indices
Community quality indices
Community type
Ecosystem
Biomass
Productivity
Nutrient Dynamics
The relationship
between measurement
and assessment endpoints
can be complex.
Assessment endpoints can
sometimes also serve as
measure-ment endpoints.
Endpoints are identifiable
environ-mental
characteristics designed to
help assess ecological
integrity in an objective
and straight-forward
fashion. Endpoints should
be determined by careful
examination of the
ecological components
being evaluated and the
overall implication to the ecosystem in question. Endpoints are discreet components of the
complex interdependent relations of an ecosystem. These endpoints may come from various
levels of the system. For example, an assessment endpoint may be a functional group (raptors)
or a particular species (coho salmon). Regardless of the level the assessment endpoints occupy
in the ecosystem, the measurement endpoints will fall at or below that level (i.e., they will be at
least or more concrete and able to be evaluated more directly).
An assessment endpoint, as defined by G. Suter III in Chapter 2 of Ecological Assessment
of Hazardous Waste Sites (EPA 1989e), is "a formal expression of an actual environmental value
to be protected. It is an environmental characteristic, which, if found to be significantly affected,
would indicate a need for remediation." While the highest assessment to be made in the overall
ecological aspects of the RI/FS process is an evaluation of the ecological integrity of the site, the
assessment endpoints are usually the highest level values at the site which can be assessed
objectively.
Individual
Death
Growth
Fecundity
Overt symptomology
Biomarkers
Tissue Concentrations
Behaviors
Population
Occurrence
Abundance
Age/size class structure
Yield/Production
Frequency of gross morbidity
Frequency of mass mortality
SOURCE: EPA1989e
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Text Box 4- 4 Characteristics of Good
(a) Assessment and (b) Measurement Endpoints
(a) Assessment Endpoints
• biological relevance
• measurable or predictable
• susceptible to the hazard
• logically related to decision
• social relevance
SOURCE: adapted from EPA 1989e
(b) Measurement Endpoints
• correspond to or predictive of
assessment endpoints
• readily measured
• appropriate to scale of site
• appropriate to exposure pathway
• appropriate temporal dynamics
• low natural variability
• diagnostic
• broadly applicable
• standard
• existing data series available
Measurement endpoints are "quantitative expressions of observed or measured effects of
a hazard; and, these measurable environmental characteristics are related to the valued
characteristics chosen as assessment endpoints (EPA 1989e)." Measurement endpoints are
those criteria which have been selected to serve as indicators of assessment endpoints.
It is imperative that all assessment endpoints have appropriate corresponding
measurement endpoint(s) to facilitate accurate evaluation. Conversely, each measurement
endpoint should be directly related to an assessment endpoint. It is not reasonable to collect data
under the guise of "measurement endpoints" when the data collected are unrelated to assessment
needs. Such data will not aid in the risk characterization or remediation processes. Text box 4-4
presents characteristics of good assessment and measurement endpoints. Table 4-1 presents a
sample summary (examples) of assessment and measurement endpoints.
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Table 4-1 Samole Summarv of Er
Assessment Endpoints
Population flux of American
peregrine falcon in Kitsap
County, WA (biological
relevance: control of rodent
population).
Coho salmon populations in
the Duwamish River basin
(societal relevance: food
source).
Measurement Endpoints
Peregrine falcon egg-shell
thinning.
Seasonal peregrine falcon
reproductive fecundity
Reproduction rates in coho
salmon
Visible lesions on the coho
salmon
idooints
Alternate Measurement
Endpoints
Level of DDT in tissue of
field mice
Number of peregrine falcon
nests
Sediment available for
spawning
Dissolved oxygen levels in
stream
4.3.3 Lines of Evidence
The conclusion of a risk assessment may be authenticated by using lines of evidence to
interprete risk estimates. Lines of evidence may be derived from several sources or by different
techniques relevant to adverse effect on the assessment endpoints, such as quotient estimates,
modeling results, field experiments and observations. Some of the factors that should be
evaluated by a risk assessor in a risk assessment to establish lines of evidence should include:
• The relevance of evidence to assessment endpoints
• The relevance of evidence to the conceptual model
• The sufficiency and data quality and study design used in the key studies
• The strength of the cause and effect relationships
• The relative uncertainties associated with the lines of evidence and their direction
For additional guidance on the application of lines of evidence in ecological risk assessments,
see (EPA 1996a and EPA1996b)
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5.0 Step 5: Site Assessments (Verification of Field and Sampling Plan)
The site assessment is the confirmatory step on the magnitude of exposures of receptors
to contaminants at the site. The site-sampling and measurements required for this step are both
diverse and specific; a number of different skills will be needed. These skills and the
corresponding measurements should have been determined at the decision point following the
problem formulation.
5.1 Sampling and Analysis Plan: Quantification of Release, Migration and Fate of
Contaminants
Sampling design should be clearly laid out in the Work plan as influenced by the decisions
made and the associated deliverables at the problem formulation step. Sampling should be based
on sound judgement taking into consideration all the variables and relevant data needs about the
site. Direct sampling of media is not the only method available, but it is useful and will help to
identify the current migration of contaminants as well as the transport mechanisms. These data
will also help to predict future migration patterns of the contaminants from the site. Also, any
sampling for background data and the areas involved should be included in the Sampling and
Analysis Plan.
5.2 Verification of Exposure Pathways: Characterization of Receptors
Characterization of receptors should be limited to site receptors, and may further be limited
to those which are directly associated with the measurement and assessment endpoints.
Information to be collected in this step includes: species' feeding habits, life histories, habitat
preference, and other attributes related to sensitivity to the contaminants at the site (EPA 1989b).
This information should be available in published literature, but some field observations may also
be essential. All pertinent data should be assembled here to insure proper assessment of the
potential effects of contaminants on given receptors to minimize uncertainty.
5.3 Estimation of Exposure Point Concentrations
This step will depend on which receptors are associated with the measurement (and
assessment) endpoints. Media which are the potential sources of exposure of receptors to site
contaminants should be sampled and analyzed to determine the levels of contamination. To
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establish the exposure point concentrations, more data will be needed to facilitate the estimation
of intake rates for the exposed group of receptors. This information may include: properties of
the contaminant, ecological effects, the nature of the receptors and the physical and chemical
properties of the media (EPA 1989b). Table 5-1 contains the intake parameters for deer mouse
and Table 5-2 shows sample intake calculations. In the case of bioaccumulation of contaminants,
biota samples from at least two trophic levels should be collected from the site and evaluated to
determine the site-specific bioconcentration and bioaccumulation rates.
Table 5-1 Sample Intake Calculations for the Deer Mouse
DEER MOUSE PARAMETERS
Soil Concentration Lead =
Body Weight =
Bioconcentration Factor(invertebrates) =
Percent Invertebrate in Diet =
Food Intake/Day =
Concentration of Pb in Seed =
Percent Seed in Diet =
Daily lntakeplant =
Concentration of Pb in Leaf =
Percent of leaf in Diet =
150 mg/kg
20g (.02 kg) deer mouse
0.65
38%
.007 kg/day dry wt.
8.6 mg/kg (Hypothetical) dry wt.
40% dry wt.
2 mg/kg-BW-day dry wt.
16.3 mg/kg dry wt.
14% dry wt.
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Chemical of
Concern
Lead
Concentration
(soil; mg/kg)
150
Daily Intake
Soil
(mg/kg-day)
6.4
Daily Intake
Invertebrate
(mg/kg-day)
18.3
Daily Intake
Plant
(mg/kg-day)
2.0
Daily
Intake
Total
(mg/kg-
day)
26.7
Table 5-2 Sample intake Calculations for the Deer Mouse
Where:
Daily Intake Soil
= (Concentrationsoil x soil ingestion rate)/body weight
= (150 mg/kg x 0.0006 kg/day)/0.02 kg body weight
= 4.5 mg Pb/kg-BW-day
Daily Intake Invertebrates = (ConcentrationsoM x bioconcentration factorinvertebrate x
% invertebrates in diet x food/day)body weight
= (150 mg Pb/kg x 0.65 x 0.38 x 0.007 kg/day)/0.02
= 12.97 mg Pb/kg-BW-day
Note: Bioconcentration factor for invertebrates are
estimated from literature.
Daily Intake Plants
= (((Concentrationseed x % seed in diet) + (concentration,eaf x
% leaf in diet)) x food/day/body weight
(((8.6 mg Pb/kg x 0.40) + (16.3 x 0.14)) x 0.007)/0.02
2.00 mg Pb/kg-BW-day
Note: Concentration of seed and leaf tissue measured at site
are hypothetical.
Daily Intake Total = Daily intakesoil + daily intakeinvertebrate + daily intakeplant
= (4.5+ 12.97 + 2.0)mg/kg-day
= 19.47mg Pb/kg-BW-day
Note: All concentrations are on dry wt. Basis.
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5.4 Toxicity Tests
Toxicity tests are used to measure the degree of response by exposed organisms to a
specified concentration of chemicals or other agents compared to an unexposed control. Toxicity
tests should only be conducted for measurements which are directly pertinent to the objective(s)
of the study from the perspectives provided by the assessment and measurement endpoints. If
not, toxicity testing can prolong (and increase the cost of) the risk assessment, while clouding the
true aims of the risk assessment and providing virtually no helpful information. Text box 5-1 lists
possible toxicity tests for different media.
Text Box 5-1 Possible Toxicity Tests and Bioassays
Aquatic
Microtox®
Fathead minnow
Rainbow trout
Sheephead minnow
Daphnia magna
Fetal Embryo Assay (FETAX)
Root Elongation/Seed Germination
Terrestrial (Soil Contact Tests)—
Earthworm Bioassay
Seed Germination
Plant Uptake (For Food Chain Transfer
Potential)
Microtox® (solid phase)
So;7 Elutriate Tests
Microtox®
Daphnia magna
Root Elongation
Sediment Elutriate Tests
Ceriodaphnia dubia
Daphnia magna
Bulk Sediment Tests
Hyalella azteca
Sand dollar assay
Bivalves (pacific oysters)
Rhepoxinius
Sea cucumber
Sea urchin reproductive assay
5.5 Toxicity Bioassays
Toxicity bioassays are used to measure the relative potency of chemicals and other agents
by comparing the effects on living organisms with the effects on a standard preparations on similar
organisms. Toxicity bioassays can be performed for each matrix (water, sediment, and soil). Text
box 5-1 lists possible bioassays for different media. The screening level bioassay will yield
qualitative information, essentially identifying whether the matrix "passes" (the organism being
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tested does not exhibit adverse effects) or "fails" (the organism exhibits adverse effects) (WDOE
1994). If the matrix "fails" the bioassay, it must be carried through the risk assessment and more
analyses must be conducted to evaluate which contaminants are contained within the matrix. If
the matrix "passes" the bioassay, it may not require further analysis, but should be retained for risk
characterization and uncertainty analysis. However, before making such a determination, the
nature of the potential contaminant(s) must be evaluated using information from the literature or
other laboratory methods such as chemical tests. For example, a particular contaminant may be
suspected to exist at levels of concern in a given medium. A screening bioassay may be
administered on that medium using an organism likely to be effected by the contaminants and the
medium may "pass" this bioassay test. A chemical analysis revealing the presence of no
significant amount of the contaminants in that medium could then be used in conjunction with the
bioassay to conclude that the medium in question does not pose significant threat to the
ecosystem. Hence, the bioassay for each medium of concern can serve 1) to indicate the
presence of a potential stressor in the media and 2) to validate chemical analyses corresponding
to each medium.
6.0 Step 6: Analysis Phase (Field / Site Investigations and Data Analysis)
Exhibit 6-1 illustrates the components of the analysis phase (Step 6). The analysis phase of
the ecological risk assessment is designed to bring all issues related to the study design, sample
collection, data quality objectives and data reduction together. However, in some cases,
modifications are warranted to the original study design. Therefore, if any unforeseen events
require a change in the WP or SAP, all changes must be agreed upon at the decision point. The
result of the analysis phase are used to characterize ecological risk in Step 7 (as illustrated on
Exhibit 7-1).
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EXHIBIT 6-1
Analysis Phase
PROBLEM FORMULATION
ANALYSIS
FNSK CHARACTERIZATION
PROBLEM FORMULATION
Characterization of Exposure | Characterization of Ecological Effects
I
Stressor
Characterization:
Distribution or
Pattern of Change
^r -^*
Ecosystem
Characterization:
Biotic
Abiotic
^^r -^*
Evaluation
of Relevant
Effects Data
Exposure
Analysis
I
Exposure
Profile
Ecological
Response
Analysis
Stressor-Response
Profile
D
a
Si
I
sc!
o'
3
V
ication and Monitoring
RISK CHARACTERIZATION
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6.1 Field Studies
A well-conducted field study can provide a valuable link between site contaminants and the
potential ecological effects. The field study will help to determine the conditions of the organisms
within the site. Several "endpoints" are considered evidence of an adverse toxic effects. Such
evidence includes:
• reduction in species population,
• absence of species known to inhabit the area,
• presence of plant or animal species associated with "stressed habitats,"
• changes in community balance or trophic structure, and
• frequency of lesions, tumors or other pathological conditions in individuals.
Literature sources are an expedient means of referencing pertinent toxicity information.
However, often they do not contain species-specific data needed. Although field studies involve
additional time and cost, but they may provide site-specific and species-specific data needed.
6.2 Analysis of Ecological Exposures and Effects
This step provides a link between exposure to contaminants and observed effects on
receptors at the site. It focuses on dose-response relationships. Some of this information may
be found in the literature, some can be determined from laboratory toxicity tests and some will
need to be measured in the field. Regardless of the source of the data, there will be some degree
of uncertainty associated with it; it is important that as data are collected, the uncertainty
associated with it be clearly understood and documented. This will be extremely useful in the risk
characterization phase. For additional detail, see EPA headquarters guidance (EPA 1996a).
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EXHIBIT 7-1
Risk Characterization
PROBLEM FORMULATION
ANALYSIS
>NSK CHARACTERIZATION
ANALYSIS
Ri
sk Estimation
Integration
Risk Description
il/
y
Uncertainty
Analysis
Ecological
Risk
Summary
I
Interpretation
of
Ecological
Significance
I
Discussion Between the
Risk Assessor and Risk Manager
(Results)
I
Risk Management
D
a
0)
>
o
JD
c
55'
o
D)
0)
a.
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7.0 Step 7: Risk Characterization
Exhibit 7-1 illustrates the components of the risk characterization phase (Step 7). Risk
characterization is the final step in the risk assessment process. All calculations and data from
exposure and ecological effects assessments can be related to the objective(s) of the risk
assessment through the conceptual model and the assessment and measurement endpoints.
The ecological effects and exposure assessments should have been guided by the measurement
endpoints, thereby providing a link to the assessment endpoints. All relevant information should
be presented in this section of the risk assessment. Both current and potential future adverse
effects must be addressed. The predicted adverse effects should then be discussed in the
context of the conceptual site model, the uncertainty encountered and the ecological significance
implied.
A recent memorandum (EPA 1995a) issued by the EPA Administrator articulates the
importance of good risk characterization, emphasizing "transparency, clarity, consistency and
reasonableness." All analyses, conclusions, resulting decisions and criteria employed to arrive at
such decisions must be made obvious and be clearly presented.
Basic assumptions and scientific policies should be consistent and grounded in science, with
care taken to avoid overly conservative approaches. Sources of uncertainty must be clearly
presented and explained. The memorandum outlines three guiding principles to direct risk
characterization:
1 The risk characterization integrates the information from the hazard identification,
dose-response, and exposure assessments, using a combination of qualitative
information, quantitative information, and information regarding uncertainties.
2 The risk characterization includes a discussion of uncertainty and variability.
3 Well-balanced risk characterizations present risk conclusions and information
regarding the strengths and limitations of the assessment for other risk assessors,
EPA decision-makers, and the public (EPA 1995a).
Risk characterization guidance, expanding on the aforementioned memorandum, and more
specifically directed towards ecological risk assessments, is currently being developed within
upcoming Guidelines for Ecological Risk Assessment, by EPA's Risk Assessment Forum.
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Risk characterization should answer the following basic question: Are ecological receptors at
the site expected to be exposed to site contaminants at levels capable of causing harm to the
overall ecosystem, or to particular valued species within that ecosystem, now or in the future? An
analysis of data gathered during the risk assessment process will enable the risk assessor to
determine risk estimate(s) related to the conceptual site model and the chosen assessment
endpoints. Subsequent discussion regarding uncertainty and ecological significance will help to
put risk estimates into a perspective allowing for sound remedial decisions. Discussion of risk
estimates should identify the strengths and limitations of the risk conclusions in such a way as to
provide a "complete, informative and useful" set of information for decision makers (EPA 1995a).
7.1 Risk Estimation and Uncertainty Analysis
Data analysis focuses on the first phase of risk characterization, risk estimation. The ground
work for data analysis is laid long before the risk characterization stage during the development
of the conceptual site model and in the choice of assessment and measurement endpoints.
These steps guide the data analysis by focussing efforts on preselected representative
component(s) of the ecosystem. Such components should account for sensitive subpopulations
and specific individuals, as appropriate, as well as the overall health of the site's ecosystem. In
what ways these components are indicative of the overall health of the site should be summarized
in the ecological significance portion of the risk description.
7.1.1 Risk Estimation
Risk estimates should integrate exposure and toxicity information in a way that supplies a
measurement of adverse risks. Such a measurement may be a qualitative description, such as
"high," "medium," or "low" or it may be a quantitative value or set of values such as a quotient or
range. The type of data evaluation employed in the screening stages of the risk assessment may
or may not be appropriate for the final risk estimation. For contaminants which were "screened
out" of the more in-depth data gathering event of the risk assessment, the conservative screening
estimate may be discussed in the risk characterization phase. For those contaminants "screened
in" to subsequent stages of the risk assessment, additional data to supplement screening level
information should be used to help characterize the risk.
If a hazard quotient is to be used to estimate risks at the site, refined data from the site-
specific exposure and toxicity investigations associated with steps 4-6 should be used to calculate
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the hazard quotient. The dose in equation 7-1 may be modified from a simple exposure point
concentration to a site- and receptor-specific intake value. The TRV may be modified from a
benchmark concentration to a receptor-specific toxicity value. A further modification may be the
construction of distributions of effects. In situations in which such data are available, a distribution
will help provide a better representation of the conditions present at the site than a single value.
Integration of field studies and computer-aided simulations, in addition to the conceptual site
model, into the risk estimate process will also help to provide a better understanding of the
potential risks present at the site. Such combination of methods may be used with a single value
quotient risk estimate, a distribution of estimated risk or even a more qualitative type of estimate.
To fully characterization the potential risks at a contaminated site, all data should be presented
clearly, and in the context of the associated endpoints embodied in the conceptual site. For
example, whether a point estimate of intake represents a maximally exposed receptor or an
average-exposed receptor must be clearly stated; or if a change was made to the conceptual
model, it should be clearly stated before related data are discussed. All extrapolations made to
apply toxicity data across species should be clearly stated. Essentially, the "lines of evidence"
leading to the risk estimates should be presented. Such an analysis is necessary for both
quantitative and qualitative risk estimations. Toxicity and exposure parameters, any professional
judgements and any inferences applied to the data, and sources should be described.
The time scale for effects predicted by risk estimation to occur should also be noted. It may
be presented as an absolute value (e.g. number of days or years); and it may also be presented
in the context of the life cycle of receptor(s) effected. Deforestation may take decades, while
depletion of microbial faunal communities may take days. Similarly, the time for a system to
potentially recover from the projected/observed effects is also relative.
7.1.2 Risk Description
Risk description provides information that will enable risk managers make decision on the
likelihood and the ecological significance of the estimated risks. For additional detail regarding
risk description, see EPA headquarters' Guidanace (EPA 540-R-97-006).
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7.1.2.1 Current A dverse Effects
Although data associated with the risk estimate(s) may be complicated, the information sought
is straightforward: are ecological receptors currently exposed to site contaminants at levels
capable of causing harm to the overall ecosystem or to particular valued species within that
ecosystem? As discussed above, a qualitative or quantitative risk estimate based on evaluation
of assessment endpoints in the context of the conceptual model should be presented. Any
assumptions, equations and/or professional judgements utilized should be clearly presented as
such. Any adverse effects predicted by the risk estimate(s) should be detailed with the types,
extent and severity of the effects (EPA 1989b).The time for such effects to occur, as well as the
time for such effects to be eradicated/mitigated, should be discussed.
7.1.2.2 Future Adverse Effects
As with the Current Adverse Effects section, this information too should be presented in a
straightforward fashion. The question is essentially the same: are ecological receptors at the site
expected to be exposed to site contaminants at levels capable of causing harm to the overall
ecosystem or to particular valued species within that ecosystem in the future? Again, a risk
estimate should be presented along with any relevant qualifications/clarification of the data.
Anticipated adverse effects should be described regarding types, extent and severity (EPA
1989b). A time line for effects and recovery should also be included.
7.1.3 Risk Calculation *
Ecological risk calculations primarily involve the hazard quotient (HQ), which is sometimes
referred to as the toxicity quotient (TQ). Equation 7-1 shows how to calculate the HQ.
;Risk calculations may be used during screening as well as later stages of the risk assessment process.
When used in the screening process such calculations must be based on conservative estimates (worst-case-
scenario). These results will not be used to set remedial or cleanup goals, rather they will assist the project
manager in making risk decisions about the site. In the screening phase, they are used to determine which
contaminants will be carried through the risk assessment.
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HQ = Dose/TRV
HQ = hazard quotient
Dose = level of contamination to which an organism is exposed expressed
in mg-contaminant/kg-body weight/day
TRV = toxicity reference value (an approved Risk-Based Concentrations or
a NOAEL-related value)
Equation 7-1 The Hazard Quotient
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(a) NOAEL = Acute or Subchronic LOAEL/10
(b) NOAEL = Chronic LOAEL/5
(c) NOAEL = LD50/50
(d) NOAEL = NOAELdifferentfamily.sameorder/2
(e) NOAEL = NOAELdifferentorde,sameclass/2
(f) NOAEL = NOAELrelatednon.protectedspecies/2
SOURCES:Calabrese & Baldwin, 1993; EPA, 1986b; Newell etal., 1987
(for non-protected species)
(for non-protected species)
(for protected species)
SOURCES:Calabrese & Baldwin, 1993; EPA, 1986b; Newell etal., 1987
Equation 7- 2 Extrapolating to NOAEL from (a) acute/subchronic LOAEL; (b) chronic LOAEL;
(c) LD50; NOAEL of related (d) family, (e) order, or (f) nonprotected species.
During the risk calculations, if no risk-based concentration values are available, the no-
observed-adverse-effect-level (NOAEL) should be used as the toxicity reference value (TRV). To
extrapolate to the NOAEL from a related value, equations 7-2 (a-f) may be applied. When no
related values are available, screening level bioassays may be appropriate. A lack of data cannot
be used to justify the elimination of a contaminant from the risk assessment; a screening level
qualification of "insufficient evidence available" should be noted and the contaminant should be
further examined during the risk assessment process.
In cases where related contaminants are found at the same site, and a cumulative effect is
suspected or known, the HI should be calculated. In the absence of any knowledge of interactive
effects, the HI is simply the summation of all HQ's corresponding to the particular contaminants
for all pathways for each media as shown in equation 7-3. Hazard Quotient (HQ) values greater
than or equal to one indicate a likelihood of risk. Contaminants with an HQ 1 should continue
to be evaluated throughout the following stages of the ecological risk assessment.
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HI = Hazard index
ZJHQ = The summation of all hazard quotients of related effects and
mode of action of contaminants of concern
Equation 7- 3: The Hazard Index
Contaminants with an HQ < 1 should be retained only for consideration in the uncertainty
analysis and risk characterization of the ecological risk assessment. Exceptions to the latter
include (1) single contaminants with HQ < 1 which contribute to one or more HI 1; and (2)
contaminants with the potential to bioaccumulate. Contaminants which may bioaccumulate
include, but are not limited to, PCBs, PAHs, cadmium and mercury. Enough information about
the nature and extent of contamination must be provided to enable the project manager (with
guidance from Regional BTAG) to decide which contaminants should be carried through the
ecological risk assessment. The hazard index (HI) is evaluated on the same principle as the HQ.
An HI of greater than or equal to one indicates a need for concern. An HI of less than one
indicates that contributing contaminants may be set aside for risk characterization and uncertainty
analysis. Best professional judgement must be employed in a hazard-quotient-based screening
process.
7.1.4 Uncertainty Analysis
Invariably, uncertainty will be associated with a quantitative risk assessment. Uncertainty is
introduced at many points along the progression of the risk assessment and its extent varies
greatly. Uncertainty is present in the values obtained, the model chosen and the scenarios
chosen. Regardless of origin or extent, uncertainty must be documented. One of the most
common criticisms of ecological risk assessments is inadequate discussion of associated
uncertainties (EPA 1992b). Masking or omission of uncertainty does not lend a higher credibility
to the data presented, it simply hampers the subsequent decisions by preventing an informed
evaluation of the data. Sources of uncertainty include natural variability, measurement error,
sampling error, human error, extrapolation mandated by an incomplete knowledge base and
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incorrect assumptions and oversimplification. Each contributor to the uncertainty of a value or
decision must be documented in the risk assessment at the point where the data are introduced;
and all uncertainty associated with data presented in the risk characterization should be
summarized here.
A sensitivity analysis of parameters may help to identify which ones have the most significant
impact upon the risk estimate. Further, those uncertainty factors with the highest potential for
reduction may be discerned. If data uncertainty, including that attributable to scientific
assumptions, professional judgement, and possible error are tracked during the preceding stages
of the risk assessment, the risk characterization will be simpler to assemble.
Uncertainty analysis is used to quantify some of the uncertainty associated with the prediction
of a risk assessment by describing the uncertainty of the inputs to the risk assessment. The
uncertainty described may be due to variability, due to an input that varies over time or by the
individual selected, or the uncertainty may be due to lack of knowledge of the correct value for a
model input value. This second source may be reduced by further study.
A popular tool for uncertainty analysis is the Monte Carlo uncertainty analysis technique. With
this technique, some of the uncertainties in the risk assessment are described by distributions and
then carried through the assessment to yield a probability distribution as the risk assessment
prediction. Refer to EPA policy paper on Monte Carlo analysis (EPA 1997). This technique is
discussed further in the next.
7.1.5 Interpretation of Uncertainty
Overall, there are three important considerations related to uncertainty which must be
presented in the risk assessment report. Foremost, the risks must be identified; second, they must
be quantified to the extent possible; third, they must be explained (or qualified). Regardless of
any uncertainty analysis method used, these three steps must be adhered to for all relevant
values, calculations and assumptions presented within the risk assessment. Such data should
have been presented throughout the risk assessment as it arose. In this section, key uncertainties
may be reiterated. Most importantly, how the uncertainties impact risk assessment results should
be discussed. Figure 7-1 shows an example of results from a Monte Carlo uncertainty analysis.
It examines the uncertainty in the exposure model prediction, due to uncertainty in the model
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inputs. The chart shows the range of possible values; a cumulative chart derived from this output
would show that about 80% of the values predict a hazard quotient below one.
-
Hazard Quotient Belted Kingfisher
Frequency Chart 5,012 Trials Shown
0
I
L
Illl Ilinid. _ .
^ 2.5 5 7.5 10
1
650
487
-n
3
191 -D
™
162 $
0
Figure 7-1 Frequency Chart of the
Hazard Quotient for the Belted Kingfisher.
The Monte Carlo method has the benefits of better describing some of the risk assessment
uncertainties verses a qualitative description. It also forces a closer look at all of the model input
parameters in order to assign distributions. However, this technique has the disadvantages of
added effort in its application and the possibility of being misapplied or possibly misrepresenting
the risk assessment uncertainties.
The use of Monte Carlo uncertainty analysis is encouraged in appropriate cases. Because
of the potential to complicate the risk assessment, before a Monte Carlo uncertainty analysis is
conducted, the contractor must present, through the RPM, its proposed use of Monte Carlo to the
ERA reviewer for approval. Documentation of the proposed use and its projected advantages
should be provided. Some of the requirements for its usage include:
• A description of all assumptions to be used in the application of the method;
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• A full description of distributions used in the analysis and the basis for each, including
possible alternatives;
• A sensitivity analysis describing important model parameters;
• A description of the uncertainties that are not described by the Monte Carlo analysis; Is
it variability and/or uncertainty that is being described?
• A computer disk of the risk model and assumptions made in the uncertainty analysis.
The Monte Carlo analysis is not necessarily appropriate for all situations; however, if it appears
to offer a better analysis of data for a given site, the above information should be provided to the
RPM and a discussion initiated to facilitate a timely and informed decision.
7. 2 Interpretation of Ecological Significance
Once calculations are made, and accompanying uncertainty presented and analyzed,
conclusions must summarized. What do the numerical results imply? What ecological risks are
present at the site. Utilizing the conceptual site model and the endpoint analysis strategy, can a
clear relationship of cause and effect be shown for between given contaminants and specific
effects on the ecosystem? What are the implications of the various uncertainties? These are the
types of focusing questions which should be answered in this final section of the risk assessment.
If site risks are to be compared to background risks, a discussion of the outcome of this
comparison, qualitative or quantitative, should be articulated here also.
7.2.1 Conclusion with Evaluation of Ecological Significance
Ecological Significance encompasses changes in both structure and function of an
ecosystem; and a discussion of these changes is the concluding portion of the risk description.
Risk estimates should have been determined during data analysis, a discussion of the lines of
evidence leading to these estimates should have been initiated during data analysis and continued
into the uncertainty assessment. Remaining is an interpretation of the ecological significance of
the estimates. Such an interpretation should follow naturally from the conceptual site model and
the assessment endpoints chosen to evaluate the site.
This section should begin with a brief recapitulation of the conceptual site model and any
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modifications made to it in the course of the subsequent stages of the risk assessment. The
hypotheses chosen to evaluate this model should be described, applying the assessment
endpoints for evaluation. For select key hypotheses and endpoints which were rejected, a brief
explanation in support of this decision should be offered. Any critical assumptions or gaps of
information should be identified, as should any points for which a consensus was never reached.
(Such instances should be rare, but may, upon occasion, occur. In such cases, the risk manager
will direct how to proceed on the risk assessment, and this may be noted in the risk
characterization.) Inevitably, professional judgement will be used to assess ecological
significance; such instances should be noted as such.
The ecological significance of risks presented should include an evaluation of intensity of
effects, scale, both spatial and temporal, of effects and potential for recovery of the ecosystem
(EPA 1989b). Measures for evaluating the ecological significance of the risks presented at a site
should have been developed in the problem formulation and conceptual site model design steps
of the ecological risk assessment. An evaluation of assessment endpoints, accounting for
intensity, scale and recovery should be the center of the ecological significance discussion. What
a "recovered" ecosystem implies should be somewhat implicit in the values represented by the
chosen endpoints. A more detailed picture can be drawn from these.
The information provided in this section will be used to guide prioritization of the site
remediation. Clarity and completeness are essential. The analysis presented here must be
connected to the assessment endpoints selected for the risk assessment. This will insure that
individuals reading the assessment understand both its purpose and its results, thereby providing
a clear perspective of the ecological impacts experienced by or projected for the site.
8.0 Step 8: Risk Management
Risk management is a process that ensues when the baseline risk assessment is complete.
Risk management decisions are the responsibility of the project manager (risk manager), not the
risk assessor. However, the project manager utilizes the risk assessment in conjunction with
available remedial options to select a preferred remedy for a site. It is imperative that the project
manager understand the risk assessment, including uncertainties and other limitations. This
understanding is crucial to the project managers ability to select the best remedial action for a site.
For instance, a risk assessment based on field study data which includes species of concern can
be appropriately weighted higher in the risk management decision in comparison to a risk
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assessment built around a literature search and/or toxicity studies on surrogate species. It is
essential that all uncertainty linked to all risk assessment data be clearly documented.
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9.0 RISK ASSESSMENT TASKS FOR THE FS
9.1 Risk Evaluation of Remedial Alternatives
Depending on the results of the risk assessment, these alternatives may be based on
ecological concerns, human health concerns, or a combination of the two. Parts B and C of the
Risk Assessment Guidance for Superfund, HHEM provide guidance on calculation of human
health risk-based remediation goals and risk evaluation of remedial alternatives. However,
because these processes involve the integration of risk assessment with management and
feasibility concerns, specific deliverables and level of effort will be determined according to the
needs of each site.
9.2 Scheduling of Risk Assessment Deliverables for the FS
Risk assessment tasks for the FS must be integrated in the FS process. The risk assessor
will need to provide risk-based concentrations, as developed during scoping or modified based
on the baseline risk assessment, to engineers working on remedial alternatives. Engineers will
need to provide estimates of time to complete remediation, of expected treatment residuals, and
of potential for releases during remedial activities to the risk assessor, for evaluations of long-term
and short-term risks. These pieces of information may be called for as separate deliverables at
the discretion of the RPM. This would probably be necessary for PRP-lead sites.
At some sites, incineration of hazardous materials is considered as a remedial alternative. In
such cases, there are risk assessment related tasks which must be performed. A list of guidance
documents, addressing both screening level evaluations and baseline risk assessment activities,
is provided in section 10 of this document. Region 10 has also recently developed a screening
level conceptual model and accompanying computer spreadsheet for screening level risk
assessment of human indirect exposure to air emissions sources, including hazardous waste
incinerators. For more information about this model, contact the Region 10 Risk Evaluation
branch in the Office of Environmental Assessment.
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10.0 Ecological Risk Assessment Resources
10.1 General Guidance
Framework for Ecological Risk Assessment. 1992. EPA/630/R-92/001
A Review of Ecological Assessment Case Studies from a Risk Assessment Perspective. 1992.
EPA/630/R-92/005.
Risk Assessment Guidance for Superfund, Volume II, Environmental Evaluation Manual. 1989.
Office of Solid Waste and Emergency Response. EPA 540/1-89/001A.
Ecological Assessment of Hazardous Waste Sites: A Field and Laboratory Reference. 1989.
EPA/600/3-89-013.
Guidance for Data Useability in Risk Assessment. 1992. Office of Emergency and Remedial
Response, Office of Solid Waste and Emergency Response, Directive No. 9285.7-09A and B.
The following recent publications contain information of interest for ecological risk assessment.
Copies may be obtained from the addresses indicated.
• Ecological Risk: A Primer for Risk Managers (EPA/734-R95-001). January 1995. Office
of Prevention, Pesticides & Toxic Substances; US EPA; (H7507C) Crystal Mall II (CM-2);
1921 Jefferson Davis Hwy; Arlington, VA 22202.
• Summary of Guidelines for Contaminated Sediments (WDOE, Publication # 95-308).
March 1995. Washington Department of Ecology; Publication; Distribution Office; P. O.
Box 47600; Olympia, WA 98504-7600; (360) 407-7472
• Protocol for the Derivation of Canadian Sediment Quality Guidelines for the Protection of
Aquatic Life (Canadian Council of Ministers of the Environment, Report CCME EPC-98E).
March 1995. Guidelines Division; Evaluation and Interpretation Branch; Environment
Canada; Ottawa, Ontario, K1A OH3; CANADA
• U.S. Environmental Protection Agency (EPA). 1994. Ecological Risk Assessment for
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Superfund: Process for Designing and Conducting Ecological Risk Assessments, review
draft. Edison, NJ: Environmental Response Team.
• U.S. Environmental Protection Agency (EPA). 1995. Draft Proposed Guidelines for
Ecological Risk Assessment. Risk Assessment Forum, Washington, D.C., EPA/630/R-
95/002.
• U.S. Environmental Protection Agency (EPA). [Soon to be released.] Superfund Mine
Waste Reference Document. (This document will have an ecological risk assessment
chapter geared towards mining sites, but also an appendix covering the general ecological
risk assessment process.)
10.2 Screening Values
Batts, D. And J. Cubbage. 1995. Summary of Guidelines for Contaminated Freshwater
Sediments. Washington State Department of Ecology. NOTE: This reference has good
screening values, but site-specific data may be more appropriate, as conditions vary.
Screening Benchmarks for Ecological Risk Assessment. Environmental Sciences and Health
Sciences Research Divisions Oak Ridge National Laboratory, Oak Ridge, Tennessee. NOTE:
These are "benchmark" values and are useful if other information is lacking; the basis for each
value should be critically evaluated before it is used.
US EPA. January 1996. Ecotox Thresholds. ECO Update 3(2). Intermittent Bulletin of Office of
Emergency and Remedial Response. NOTE: These values may not be appropriate in all
situations; particular attention should be given to applicability to site conditions.
10.3 Uncertainty References
Frey, H.C., Quantitative Analysis of Uncertainty and Variability in Environmental Policy Making,
American Association for the Advancement of Science, Washington. DC. 1992.
Burmaster, D.E. and Anderson, P.O., "Principles of Good Practice for the Use of Monte Carlo
Techniques in Human Health and Ecological Risk Assessments." Risk Analysis, Vol 14, pp.
477-481, 1994.
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Macintosh, D.L., Suter, G.W., and Hoffman, P.O., "Use of Probabilistic Exposure Models in
Ecological Risk Assessments of Contaminated Sites," Risk Analysis, Vol 14. pp. 405-419,
1994.
US EPA. May 15, 1997. Policy for use of Probabilistic analysis in risk assessments: Guiding
principles for Monte Carlo Analysis. EPA/630/R-97/001.
10.4 Where to Obtain Documents
• IRIS User Support (513-569-7254). This resource can provide information about how to
access IRIS on-line through vendors. IRIS is also available on PC-compatible diskettes
from NTIS.
• National Technical Information Service, Springfield, VA (703-487-4650). NTIS distributes
many government publications including EPA documents.
• National Risk Management Research Laboratory (formerly, CERI), Cincinnati, Ohio (513-
569-7562). Depending on availability, NRMRL can provide free single copies of ORD
guidance documents, primarily those identified with EPA/600, and some other documents.
• Superfund Docket (703) 603-8917. Limited source for guidance identified as "OSWER
Directive # XXXXX."
• Region 10 EPA Library (206-553-1289). The library will loan EPA publications (and
ATSDR Toxicity Profiles) to the public.
• Safe Drinking Water Hotline (800-426-4791). This hotline is staffed from 9 am to 5:30 pm
EST.
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11.0 REFERENCES
Calabrese, E. J., and L. A. Baldwin. 1993. Uncertainty factors for ecological risk assessment. In:
E.J. Calabrese and L. A. Baldwin (eds.), Performing ecological risk assessment. Lewis
Publishers, Boca Raton, Florida, Chapter 4.
Newell, A. J., D. W. Johnson and L. K. Allen. 1987. Niagara River Biota Contamination Project:
Fish Flesh Criteria for Piscivorous Wildlife. Technical Report 87-3, division of Fish and Wildlife,
Bureau of Environmental Protection, New York State Department of Environmental
conservation.
US Environmental Protection Agency(EPA) 1997. Policy for use of Probabilistic analysis in risk
assessments: Guiding principles for Monte Carlo Analysis. EPA/630/R-97/001.
U.S. Environmental Protection Agency (EPA). 1996a. Ecological Risk Assessment for Superfund:
Process for Designing and Conducting Ecological Risk Assessments, review draft. Edison,
NJ: Environmental Response Team.
U.S. Environmental Protection Agency (EPA). 1996b Proposed Guidelines for Ecological Risk
Assessment, Risk Assessment Forum, Washington, D.C . E PA/630 R-95/002B.
U.S. Environmental Protection Agency (EPA). 1996c. Ecotox. ECO Update, Intermittent Bulletin,
Volume 3, Number 2. Washington, DC: Office of Emergency and Remedial Response,
Hazardous Site Evaluation Division; Publ. 9345.0-12FSI.
U.S. Environmental Protection Agency (EPA). 1995a. Risk Characterization Memorandum.
Washington, DC: EPA Administrator; March 1995.
U.S. Environmental Protection Agency (EPA). 1995b. Exposure Factors Handbook, Internal
Review Draft. Washington, D.C.: NCEA; Publ. NCEA-W005.
U.S. Environmental Protection Agency (EPA). 1995c. Health Effects Assessment Summary
Tables (HEAST). Office of Solid Waste and Emergency Response, Office of Emergency and
Remedial Response 9200.6-303. NTIS No. PB91-921100.
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U.S. Environmental Protection Agency (EPA). 1995d. Integrated Risk Information System (IRIS).
On-line database.
U.S. Environmental Protection Agency (EPA). 1994a. Ecological Risk Assessment for Superfund:
Process for Designing and Conducting Ecological Risk Assessments, review draft. Edison,
NJ: Environmental Response Team.
U.S. Environmental Protection Agency (EPA). 1994b. So/7 Screening Guidance. Office of Solid
Waste and Emergency Response; EPA/540/R-94/101.
U.S. Environmental Protection Agency (EPA). 1994c. A Review of Ecological Assessment Case
Studies from a Risk Assessment Perspective, Volume II. Washington, DC: Risk Assessment
Forum; EPA/630/R-94/003.
U.S. Environmental Protection Agency (EPA). 1993a. Wildlife Exposure Factors Handbook,
Volumes I and II. Washington, DC: Office of Research and Development; EPA/600/R-
93/187A&B.
U.S. Environmental Protection Agency (EPA). 1993b. A Review of Ecological Assessment Case
Studies from a Risk Assessment Perspective, Volume I. Washington, DC: Risk Assessment
Forum; EPA/630/R-93/005.
U.S. Environmental Protection Agency (EPA). 1992a. Framework for Ecological Risk
Assessment. Washington, DC: Risk Assessment Forum; EPA/630/R-92/001.
U.S. Environmental Protection Agency (EPA). 1992b. Peer Review Workshop Report on a
Framework for Ecological Risk Assessment. Washington, DC: Risk Assessment Forum;
EPA/625/3-91/022.
U.S. Environmental Protection Agency (EPA). 1991a. Conducting Remedial
Investigations/Feasibility Studies for CERCLA Municipal Landfill Sites. Office of Emergency
and Remedial Response. OSWER Directive No. 9355.3-11.
U.S. Environmental Protection Agency (EPA). 1991b. Interim Guidance for Dermal Exposure
Assessment. Office of Research and Development, Office of Health and Environmental
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Assessment. OHEA-E-367.
U.S. Environmental Protection Agency (EPA). 1991c. Risk Assessment Guidance for Superfund,
Volume I, Human Health Evaluation Manual, Part B, Development of Risk-based Remediation
Goals. Office of Solid Waste and Emergency Response. OSWER Directive No. 9285.7-01 B.
U.S. Environmental Protection Agency (EPA). 1991d. Risk Assessment Guidance for Superfund,
Volume I, Human Health Evaluation Manual, Part C, Risk Evaluation of Remedial Alternatives.
Office of Solid Waste and Emergency Response. OSWER Directive No. 9285.7-01C.
U.S. Environmental Protection Agency (EPA). 1991e. Role of the Baseline Risk Assessment in
Superfund Remedy Selection Decisions. Office of Solid Waste and Emergency Response.
OSWER Directive No. 9355.0-30.
U.S. Environmental Protection Agency (EPA). 1991f. Supplemental Guidance on Performing Risk
Assessments in Remedial Investigations/Feasibility Studies Conducted by Potentially
Responsible Parties. Office of Solid Waste and Emergency Response. OSWER Directive No.
9835.15a.
U.S. Environmental Protection Agency (EPA). 1991g. The Role of BTAGs in Ecological
Assessment. ECO Update, Intermittent Bulletin, Volume 1, Number 1. Washington, DC:
Office of Emergency and Remedial Response, Hazardous Site Evaluation Division; Publ.
934.0.05I.
U.S. Environmental Protection Agency (EPA). 1991 h. Risk Assessment Guidance for Superfund,
Human Health Evaluation Manual, Supplemental Guidance: Standard Default Exposure
Factors. Office of Emergency and Remedial Response, Office of Solid Waste and Emergency
Response, Directive No. 9285.6-03.
U.S. Environmental Protection Agency (EPA). 1990a. Air Pathway Analysis Procedures for
Superfund Applications. Office of Air Quality Planning and Standards. EPA/450/1-
89/001,002,003,004.
U.S. Environmental Protection Agency (EPA). 1990b. Guidance for Data Useability in Risk
Assessment. Office of Emergency and Remedial Response. EPA/540/G-90/008.
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U.S. Environmental Protection Agency (EPA). 1990c. Methodology for Assessing Health Risks
Associated with Indirect Exposure to Combustor Emissions. EPA 600/6-90/003.
U.S. Environmental Protection Agency (EPA). 1990d. National Oil and Hazardous Substances
Pollution Contingency Plan; Final Rule. Federal Register, Vol. 55, No. 46, pages 8665-8865.
U.S. Environmental Protection Agency (EPA). 1989a. Development of a Risk Assessment
Methodology for Land Application and Distribution and Marketing of Municipal Sludge. EPA
600/6-89/001.
U.S. Environmental Protection Agency (EPA). 1989b. Ecological Assessment of Superfund Sites:
An Overview. ECO Update, Intermittent Bulletin, Volume 1, Number 2. Washington, DC:
Office of Emergency and Remedial Responses, Hazardous Site Evaluation Division; Publ.
9345.0.0-5I.
U.S. Environmental Protection Agency (EPA). 1989c. Risk Assessment Guidance for Superfund:
Volume 2 - Environmental Evaluation Manual, Interim Final. Washington, DC: Office of Solid
Waste and Emergency Response; EPA/540/1-89/001A.
U.S. Environmental Protection Agency (EPA). 1989d. Risk Assessment Guidance for Superfund,
Volume I, Human Health Evaluation Manual, Part A, Baseline Risk Assessment. Office of
Solid Waste and Emergency Response. OSWER Directive No. 9285.7-01 A. EPA 540/1-
89/002.
U.S. Environmental Protection Agency (EPA). 1989e. Ecological Assessment of Hazardous
Waste Sites: A Field and Laboratory Reference. Corvallis, OR: Office of Research and
Development, Environmental Research Laboratory; EPA/600/3-89/013.
U.S. Environmental Protection Agency (EPA). 1988a. CERCLA Compliance with Other Laws
Manual, Interim Final, Volumes, I and II. Office of Emergency and Remedial Response.
OSWER Directive No. 9234.1-01 and 9234.1-02. EPA/540/6-89-009.
U.S. Environmental Protection Agency (EPA). 1988b. Guidance for Conducting Remedial
Investigations and Feasibility Studies Under CERCLA. Office of Emergency and Remedial
Response. OSWER Directive No. 9355.3-01.
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U.S. Environmental Protection Agency (EPA). 1988c. Estimating Exposures to 2,3,7,8-TCDD.
Office of Health and Environmental Assessment. EPA 600/6-88/005A.
U.S. Environmental Protection Agency (EPA). 1988e. Superfund Exposure Assessment Manual.
Office of Remedial Response. EPA 540/1-88/001.
U.S. Environmental Protection Agency (EPA). 1988f. Estimating Toxicity of Industrial Chemicals
to Aquatic Organisms Using Structure Activity Relationships. Office of Toxic Substances;
EPA/560/688/001.
U.S. Environmental Protection Agency (EPA). 1986a. Risk Assessment Guidelines of 1986.
Office of Health and Environmental Assessment. EPA/600/8-87-045. (Also published in the
Federal Register, September 24, 1986, 55 FR 33992-34054.)
U.S. Environmental Protection Agency (EPA). 1986b Standard Evaluation Procedure, Ecological
Risk Assessment. EPA/600/8-87-045. Hazard Evaluation Division. EPA 540/9-86/167. D. J.
Urban and N. J. Cook, Office of Pesticide Programs, U.S. Environmental Protection Agency,
Washington, D.C.
U.S. Environmental Protection Agency, Region III (EPA III). 1994. Interim Ecological Risk
Assessment Guidelines. Philadelphia, PA: Hazardous Waste Management Division,
Superfund Program Branch; Publ. 19107-4431.
U.S. Environmental Protection Agency, Region IV (EPA IV). 1995a. Data Collection and
Evaluation, Supplemental Guidance to RAGS: Region 4 Bulletins: Human Health Risk
Assessment. Atlanta: Waste Management Division; Bulletin 1.
U.S. Environmental Protection Agency, Region IV (EPA IV). 1995b. Toxicity Assessment,
Supplemental Guidance to RAGS: Region 4 Bulletins: Human Health Risk Assessment.
Atlanta: Waste Management Division; Bulletin 2.
U.S. Environmental Protection Agency, Region IV (EPA IV). 1995c. Exposure Assessment,
Supplemental Guidance to RAGS: Region 4 Bulletins: Human Health Risk Assessment.
Atlanta: Waste Management Division; Bulletin 3.
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U.S. Environmental Protection Agency, Region IV (EPA IV). 1995d. Risk Characterization,
Supplemental Guidance to RAGS: Region 4 Bulletins: Human Health Risk Assessment.
Atlanta: Waste Management Division; Bulletin 4.
U.S. Environmental Protection Agency, Region X (EPA X). 1990. Region 10 Policy, Conduct of
Remedial Investigations and Feasibility Studies. Region 10 Hazardous Waste Division.
Van Horn, R.L, N.L. Hampton, T.A. Bensen and C.S. Staley (INEL). 1994. Guidance Manual for
Conducting Screening Level Ecological Risk Assessment of the INEL, draft. Idaho Falls, ID:
Idaho National Engineering Laboratories.
Washington State Department of Ecology. 1991. Model Toxics Control Act Cleanup Regulation.
Chapter 173-340 WAC.
65
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Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Appendix A
(Determination of background Levels for Soils)
This document is being reviewed
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Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Appendix B
(l)Region 10 Guidelines for determining the bioavailability of inorganic
contaminants in soil for human health and ecological risk assessments
For evaluations of the soil and dust ingestion pathway in human and animal
exposure assessments, it may be appropriate to adjust the percentage of uptake of
some inorganic contaminants. Physical and chemical properties of metals such as
solubility and speciation, may affect bioavailability. Metals in the environment do not
occur in pure form, instead they form compounds with other chemical elements, like
carbon, phosphorus, silicon and sulfur. Also, characteristics of the soil matrix may
decrease the bioavailability of these contaminants into the body from 100 percent.
Additionally, biological and behavioral features of the receptor such as conditions in the
stomach, lungs and intestines (in human or animal), may also decrease the uptake from
100 percent. However, there is no evidence to suggest that in all circumstances the
bioavailability of inorganic soil contaminants will always be less than 100 percent.
This Region 10 risk assessment guidance provides default options for specific
inorganic contaminants in soil. If non-default options are desired, further guidance is
provided regarding the acceptable approaches.
I. Guidelines for specific inorganic contaminants in soil:
A. Arsenic
1. If contamination is associated with the application of
pesticides/herbicides, wood treatment processes and/or fossil fuel
combustion, assume 100% bioavailability.
2. If the site is a smelter site and its appears likely that the arsenic
exists primarily as finely-grained oxides from smelter stack
emissions, assume 80% relative bioavailability. This value is
supported by a conservative interpretation of the scientific
literature (EPA, 1992).
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Supplemental Ecological Risk Assessment Guidance for Superfund
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3. If the site is primarily impacted by mineralogical activities such as
mining, milling, tailings and other activities and no associated
smelting activities, assume 60% relative bioavailability.
This value is the lower 95% confidence limit derived from the
Region 10 oral dosing study of immature swine. Swine were
dosed with residential soils collected from a smelter-impacted site
at Ruston, Tacoma in Washington state. This study has been
scientifically peer reviewed and the complete report is available
(EPA 910/R-96-002). Based on results from several scientific,
peer reviewed reports it is reasonable to assume that the lower
confidence limit of results based on smelter wastes (i.e. 60%) is
unlikely to be less than the mean of a study based on site-specific
mining wastes. However, 60% relative bioavailability is likely to
be within the 95% confidence limits of the mean of results from a
study based on mining wastes, if such a site-specific study
existed.
B. Lead
1. If the assessment is for childhood exposures, use the default
bioavailability parameter incorporated in the Integrated Exposure
Uptake Biokinetic (IEUBK) Model for Children (version 0.99d), or
the most current model version.
2. If the assessment is for adult exposures, use the default
bioavailability parameter incorporated in the USEPA
"Recommendations of the Technical Review Workgroup for Lead
for an Interim Approach to Assessing Risks Associated with Adult
Exposures to Lead in Soil" (December 1996), or the most current
version.
3. If alternate bioavailability values are proposed (based either on in
vivo studies, blood lead studies or other studies) for use in the
IEUBK model or the Adult model, the proposed values should be
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submitted to the Technical Review Workgroup (TRW) for Lead for
review and/or should be compared to current guidance regarding
use the IEUBK, blood lead studies and other studies. Review by
the TRW is intended to assure national consistency in lead
exposure and risk assessment.
II. Guidelines for inorganic contaminants in soil
If non-default options for arsenic or lead are desired, or bioavailability for other
inorganic contaminants is being considered in the risk assessment, the
following guidance is provided regarding acceptable approaches.
A. Based on the toxicological data available and the basis for the cancer
slope factor or Reference Dose, determine whether bioavailability data
should represented as "absolute" or "relative". Consultation with the
regional toxicology staff should be sought when making this
determination.
The choice of appropriate bioavailability factors should be discussed with
the regional toxicology staff during the planning and scoping phases of
the baseline risk assessment. This will assure that the proper
environmental samples are collected and that the site manager is briefed
regarding the significance of bioavailability at the site under
consideration, and the uncertainties associated with the various types of
data discussed below.
B. If in vivo data on the extent of uptake of a specific inorganic contaminant
from site-derived wastes are available, these data should be qualitatively
or quantitatively utilized in the exposure assessment. Quantitative use of
the data should be dependent on the scientific merit of the study, the
degree of confidence that site-specific exposure parameters have been
appropriately addressed in the study design and that the results of the
study are applicable to the exposure assessment under consideration.
When in vivo data are not adequate for quantitative use, the data may be
used in the risk assessment report's discussion regarding uncertainties
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of the exposure assessment, to design further in vivo studies and/or to
design other types of laboratory studies.
C. If site-specific in vivo data on bioavailability are lacking but mineral
speciation or petrological data are available, and those data indicate that
the site-derived wastes are sufficiently similar to materials used in an
appropriate in vivo study (see above), then the "absolute" or "relative"
bioavailability, whichever is appropriate, may be used from the in vivo
study. The cons-traints on the use of the in vivo data are the same as
stated in #2, above.
D. If mineralogical or petrological data are not available from site-derived
wastes, if available data are inadequate, if site samples are not
sufficiently similar to samples utilized in an in vivo study, or if the in vivo
data are inapp-ropriate for the site under consideration then 100 percent
bioavailability should be assumed in the exposure assessment. (See
above for specific defaults for arsenic and lead.)
Glossary:
Absolute-bioavailability. This is the situation where the absorbed fraction of a
specific compound in a particular medium is identical to the
bioavailable form. For example, if sodium arsenate was 80
percent absorbed from drinking water and arsenic sulfide
was 40 percent absorbed from the same water, then the
absolute bioavailability of these compunds would be 80
percent and 40 percent, respectively .
Relative-bioavailability. This is the situation where the absorption of a particular
compound in a particular medium is compared to some other reference point.
For example, in the case above, if sodium arsenate in drinking water was the
reference point, then the relative bioavailability of arsenic sulfide in drinking
water would be 80 divided by 40, which would be equal to 0.50 or 50 percent.
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Supplemental Ecological Risk Assessment Guidance for Superfund
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References:
USEPA. 1996. Bioavailability of arsenic and lead in environmental substrates I. Results
of an oral dosing study of immature swine. February 1996, EPA 910/R-96-002.
USEPA. 1994. Guidance Manual for the Integrated Exposure Uptake Biokinetic Model
for Lead in Children (IEUBK). EPA/540/R-93/083. Office of Emergency and
Remedial response, Washington, D. C.
USEPA. 1992.< Baseline Risk Assessment Ruston/ North Tacoma Operable Unit
Commencement Bay Nearshore/Tideflats Superfund Site, Tacoma, Washington.
ll.Oakridge Toxicological Screening Benchmark Values
(To download this document, please visit the Oak Ridge National Laboratory Homepage at:
http://www.ornl.gov/
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
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Appendix C
"The Tool Box"
Region 10 Risk Report Technical Issues
(Guidelines for Screening Radionuclides for Eco-effects)
See Radiotoxicological Benchmarks for Wildlife at the Rocky Flats
Environmental Te - Programs and Capabilities Database No. 607-024.
RADIOTOXICOLOGICAL BENCHMARKS FOR WILDLIFE AT THE
ROCKY FLATS ENVIRONMENTAL TECHNOLOGY (RFET) SITE....
-http://www.anl.gov/LabDB/Current/Ext/H607-text.024.html
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Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Appendix D
Region 10 Risk Report, Special Release Case Study Summaries
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Office of Environmental Assessment June 1997
Release Number 1
Region 10
Risk Report
focus: ecorisk
1200 Sixth Avenue
Seattle, WA 98101
(206)553-8209
An intermittent publication of the US EPA Region 10 Risk Evaluation Unit, this report is
intended as a technical case study illustration to supplement the regional Superfund risk
assessment guidance (Jan 96) and can be nested in Appendix C of that document.
(Insert Soil Background Issue Paper)
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Office of Environmental Assessment June 1997
Release Number 2
Region 10
Risk Report
focus: ecorisk
1200 Sixth Avenue
Seattle, WA 98101
Special Release: Case Study <**) SSS-KO*
An intermittent publication of the US EPA Region 10 Risk Evaluation Unit, this report is
intended as a technical case study illustration to supplement the regional Superfund risk
assessment guidance (Jan 96) and can be nested in Appendix IV of that document.
(Insert Soil Background Case Study Excerpts from Region 10 Sites)
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Office of Environmental Assessment June 1997
Release Number 3
Region 10
Risk Report
focus: ecorisk
1200 Sixth Avenue
Seattle, WA 98101
Special Release: Case Study <**) SSS-KO*
An intermittent publication of the US EPA Region 10 Risk Evaluation Unit, this report is
intended as a technical case study illustration to supplement the regional Superfund risk
assessment guidance (Jan 96) and can be nested in Appendix D of that document.
(Insert Ecological Risk Assessment Case Study)
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EPA Region 10
Supplemental Ecological Risk Assessment Guidance for Superfund
June 1997
Attachments
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