REPORT ON THE PEER REVIEW OF THE HUDSON RIVER PCBs
HUMAN HEALTH RISK ASSESSMENT
Final Report
Prepared for:
U.S. Environmental Protection Agency, Region II
Emergency and Remedial Response Division
290 Broadway, 18th Floor
New York, NY 10007-1866
EPA Contract No. 68-W6-0022
Work Assignment No. 4-12
Prepared by:
Eastern Research Group, Inc.
110 Hartwell Avenue
Lexington, MA 02421
September 2000
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NOTE
This report was prepared by Eastern Research Group, Inc. (ERG), an EPA contractor, as a
general record of discussion for the peer review meeting. This report captures the main points of
scheduled presentations and highlights discussions among the reviewers. This report does not contain a
verbatim transcript of all issues discussed during the peer review. Additionally, the report does not
embellish, interpret, or enlarge upon matters that were incomplete or unclear. EPA will evaluate the
recommendations developed by the reviewers and determine what, if any, modifications are necessary to
the current risk assessment. Except as specifically noted, no statements in this report represent analyses
or positions of EPA or of ERG.
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TABLE OF CONTENTS
LIST OF ABBREVIATIONS ii
EXECUTIVE SUMMARY iii
1.0 INTRODUCTION 1-1
1.1 Background 1-1
1.2 Scope of the Peer Review 1-3
1.3 Report Organization 1-7
2.0 RESPONSES TO SPECIFIC QUESTIONS REGARDING THE HHRA 2-1
2.1 Responses to Question 1 2-2
2.2 Responses to Question 2 2-5
2.3 Responses to Question 3 2-7
2.4 Responses to Question 4 2-9
2.5 Responses to Questions 5 and 6 2-11
2.6 Responses to Question 7 2-16
3.0 RESPONSES TO GENERAL QUESTIONS REGARDING THE HHRA 3-1
4.0 REVIEWERS' OVERALL RECOMMENDATIONS 4-1
4.1 Summary of Specific Recommendations 4-1
4.2 Individual Reviewer Recommendations 4-4
5.0 REFERENCES 5-1
APPENDIX A List of Expert Peer Reviewers
APPENDIX B Charge to Expert Peer Reviewers
APPENDIX C Premeeting Comments, Alphabetized by Author
APPENDIX D List of Registered Observers of the Peer Review Meeting
APPENDIX E Agenda for the Peer Review Meeting
APPENDIX F Summaries of Observers' Comments
APPENDIX G Minutes from the March 2000 Briefing Meeting
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LIST OF ABBREVIATIONS
CSF
cancer slope factor
CTE
central tendency exposure
EPA
U.S. Environmental Protection Agency
ERG
Eastern Research Group, Inc.
GE
General Electric
HHRA
Human Health Risk Assessment
HI
hazard index
IRIS
Integrated Risk Information System
NYSDOH
New York State Department of Health
PCBs
poly chlorinated biphenyls
RfD
reference dose
RME
reasonable maximum exposure
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EXECUTIVE SUMMARY
Six independent peer reviewers critiqued the "Human Health Risk Assessment" (HHRA) and its
Responsiveness Summary, which were prepared as part of the U.S. Environmental Protection Agency's
(EPA's) reassessment of the Hudson River PCBs Superfund site. At the end of the peer review meeting
held in May 2000, all six reviewers indicated that the HHRA and its Responsiveness Summary were
"acceptable with revisions." Two reviewers indicated that major revisions were required, one indicated
the need for minor revisions, and three reviewers did not explicitly state the extent of the revisions
needed.
During the 1 '/2-day meeting, the peer reviewers answered nine charge questions that addressed
various aspects of the human health risk assessment. These questions asked reviewers to comment on the
technical merit of the approaches used in different phases of the risk assessment process, including
hazard identification/dose-response assessment, exposure assessment, uncertainty analysis, and risk
characterization. Reviewers also evaluated the overall clarity and transparency of the HHRA and its
Responsiveness Summary.
Reviewers agreed that the document was consistent with the basic guidelines and guidance set
forth for a Superfund human health risk assessment and commended EPA for its efforts. However, the
reviewers did identify some weaknesses that they felt lessened the scientific credibility of the risk
assessment. Five out of the six reviewers commented that the risk assessment needed to be expanded to
provide additional perspective on what the risk estimates mean in the context of the real world. The
reviewers encouraged EPA to expand discussions about the uncertainties associated with the toxicity
values used and how the consideration of newer toxicity data might change the results of the risk
assessment. The majority of the reviewers also indicated the need for an expanded quantitative
uncertainty analysis that would generate confidence intervals on the cancer risk estimates and hazard
indices. The reviewers also expressed concern that the HHRA focused on anglers and provided only
limited analysis of childhood and fetal exposures. Lastly, the group agreed that the HHRA needed to be
more transparent when describing and justifying the selection and evaluation of exposure pathways,
modeled exposure concentrations, and toxicity values.
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A more detailed summary of reviewer comments and recommendations is presented below, by
discussion topic. Unless otherwise stated, reviewers voiced general agreement with these summary
points.
Hazard Identification/Dose Response
Using the current toxicity values for PCBs from EPA's Integrated Risk Information
System (IRIS) is appropriate, but a new section should be added to Chapter 4 (Toxicity
Assessment) to provide a quantitative and/or qualitative discussion on the more recent
studies on both cancer and non-cancer endpoints to determine what effect these studies
might have on risk estimates (e.g., Will risk estimates go up, down, or stay the same?).
List all sources of uncertainty pertaining to the IRIS toxicity criteria used to calculate the
point estimates and qualitatively discuss the effect on risk (high, medium, low) and the
extent to which the toxicity data selected for use in the assessment would affect risk
estimates (Will the risk estimates go up, down, or stay the same?). For example, factors
to consider include the use of animal data, uncertainty factors, modifying factors, and
high-to-low dose extrapolation models.
Some reviewers strongly encouraged a quantitative evaluation of the uncertainty
associated with the toxicity data and recommended that this information be incorporated
within the overall uncertainty analysis of the Hazard Index (HI) and cancer risk
estimates. Other reviewers stated that qualitative discussion of the uncertainty associated
with the toxicity data is sufficient.
Exposure Assessment
Fish ingestion rates used in the point estimates are reasonable for adults.
Data from the New York State Department of Health's (NYSDOH's) recent survey
should be incorporated to verify whether the Connelly et al. (1992) study captures the
demographics of the exposed population.
Assuming that all fish consumed originate from the Upper Hudson River seems
unreasonable (too conservative).
Some reviewers commented that evaluating exposures on a location-by-location basis
would better characterize exposed subpopulations. Other reviewers felt this issue was
minor.
Justification for scenarios and/or pathways (e.g., soil-related pathways) that were not
quantified in the risk assessment should be added to Table 2-1.
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All aquatic species that may be consumed (e.g., turtles and eels) may not have been
evaluated, which could result in an underestimation of risks. A discussion of this issue
should be included in the uncertainty analysis.
Some reviewers would like information on the size of the exposed population included in
the HHRA.
Because the HHRA assumes that exposure begins in 1999, the text should emphasize
that the risks estimated in this assessment are incremental and overlay previous
exposures/risks.
Include a discussion of PCB clearance rates (i.e., half-life of PCBs in the human body)
and how these rates relate to exposure duration and the application of the reference dose
(RfD).
The averaging times used are appropriate except for the evaluation of effects to pregnant
and nursing women. EPA should evaluate the appropriate exposure duration averaging
for this group (i.e., this should be less than the 7 years used in the HHRA [e.g., 1-2
years]). The averaging time for fetuses (pregnant women) should include the range (days
to months) for peak exposures. In addition, some reviewers suggested that the exposure
duration be 7 years for both the central tendency exposure (CTE) and reasonable
maximum exposure (RME).
Modeling efforts used to calculate fish concentrations and validation of models are not
adequately discussed in the HHRA. The text needs to be expanded and clarified to
provide information on the uncertainty and temporal and spatial variations in the average
concentration in various species of fish.
Monte Carlo/Uncertainty Analysis
Include a table that defines variability and uncertainty (confidence intervals) for all input
parameters. For those parameters for which a distribution is defined, the rationale for the
selected distribution should be described.
The uncertainty analysis needs to be enhanced. CTE and RME cancer risk estimates and
HI values need to have confidence intervals.
Because the Monte Carlo presentation was difficult to follow and not always transparent,
additional clarification is warranted.
Risk Characterization
Qualitatively acknowledge that background exposures and the fact that the study
population has been pre-exposed are likely to increase the HI and cancer risk estimates.
Evaluating background and pre-exposures could be important in calculating remediation
goals and/or for risk management issues.
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Discuss the conservatism of the cancer slope factor (CSF) and potential non-
conservatism of the RfD for PCBs and its effect on the final risk estimates.
Provide an expanded interpretation of results, clearly explaining that the cancer risk
estimates are theoretical and upper-bound and that the true cancer risk is likely to be
lower and could even be zero.
General Recommendations
Evaluate exposures of pregnant women (and consequently the developing fetus) and
exposures via the ingestion of mother's milk in the HHRA.
Include a qualitative discussion on the applicability of the IRIS RfD value to pregnant
women and nursing neonates, considering the issues related to potential neuro
developmental effects of PCBs in children.
Discuss the potential interactive and cumulative effects that other chemicals, which also
may be present in the Upper Hudson River, may have on PCB toxicity.
Include all the information/data that will be necessary to calculate a range of fish
concentrations necessary for risk management objectives.
Throughout the HHRA, include the necessary and relevant information from other
supporting documents to make the risk characterization section more transparent (e.g.,
calculation of fish concentrations).
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1.0 INTRODUCTION
This report summarizes an independent peer review by six experts of the following documents the
U.S. Environmental Protection Agency (EPA) released as part of its reassessment of the Hudson River
PCBs Superfund site:
Human Health Risk Assessment (HHRA), Upper Hudson River (TAMS Consultants, Inc.,
Gradient Corporation, 1999).
Responsiveness Summary for Human Health Risk Assessment, Upper Hudson River (TAMS
Consultants, Inc., Gradient Corporation, 2000).
To facilitate their evaluations of these reports, the reviewers also were given copies of several
additional reports with relevant background information. Section 1.2.2 lists these additional references.
The reviewers attended two meetings, both of which were open to the public. The first meeting
took place in Saratoga Springs, New York, on March 22-23, 2000. This meeting included several
presentations and a tour of the Upper Hudson River to familiarize the reviewers with the site and its
environmental history. The second meeting took place in Saratoga Springs, New York, on May 30-31,
2000. This meeting was the forum in which the reviewers critiqued the above documents. Eastern
Research Group, Inc. (ERG), a contractor to EPA, organized the expert peer review and prepared this
summary report.
This introductory section provides background information on the Hudson River PCBs Superfund
site, the scope of the peer review of the HHRA, and the organization of this report.
1.1 Background
In 1983, EPA classified approximately 200 miles of the Hudson River in the state of New
Yorkfrom Hudson Falls to New York Cityas a Superfund site, because of elevated concentrations of
PCBs in the river's sediments. The sediments are believed to have been contaminated by discharges of
PCBs over approximately 30 years from two General Electric (GE) capacitor manufacturing plants, one in
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Hudson Falls and the other in Fort Edward. After an initial assessment, EPA issued an "interim No Action
decision" in 1984 for the contaminated sediments of the Hudson River PCBs site.
Since 1990, EPA has been reassessing its earlier decision to determine whether a different course
of action is needed for the contaminated sediments in the Hudson River. EPA is conducting this
reassessment in three phases: compiling and analyzing existing data for the site (Phase 1), collecting
additional data and using models to evaluate human health and ecological risks (Phase 2), and studying the
feasibility of remedial alternatives (Phase 3). EPA has documented its findings from Phase 2 of the
reassessment in a series of reports, four of which have already been peer reviewed by independent
scientists.
As part of Phase 2, EPA's contractors developed a baseline human health risk assessment
(HHRA) for the Upper Hudson River. The HHRA quantitatively evaluated both cancer risks and non-
cancer health hazards from exposure to PCBs in the Upper Hudson River, which extends from Hudson
Falls, New York, to the Federal Dam at Troy, New York. The HHRA evaluated only those potential
health risks associated with exposures to PCBs. The objective of the Phase 2 risk assessment was to
update the findings from Phase 1 in light of the following new information: (1) additional PCB data
collected in water, sediment, fish and other biota; (2) PCB concentration estimates in environmental media
based on extensive modeling efforts; (3) an extensive review of fish ingestion surveys; and (4) an
extensive review of the cancer toxicity of PCBs. Another goal of the Phase 2 HHRA was to estimate
risk to the average exposed individual as well as to the reasonably maximally exposed individual. Upon its
completion, the HHRA was released for public comment. To address comments received during the
public comment period, EPA released a Responsiveness Summary, which included EPA's response to
comments as well as revisions to the risk assessment. EPA also conducted an ecological risk assessment
as part of Phase 2, separate from the HHRA.
To ensure that the assumptions, methods, and conclusions of the HHRA and its Responsiveness
Summary are based on sound scientific principles, EPA decided, as per policy, to obtain an expert peer
review of the documents. The remainder of this report describes the scope and findings of this
independent peer review.
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1.2 Scope of the Peer Review
ERG managed every aspect of the peer review, including selecting reviewers (see Section 1.2.1),
briefing the reviewers on the site (see Section 1.2.2), and organizing the peer review meeting (see Section
1.2.3). The following subsections describe what each of these tasks entailed.
1.2.1 Selecting the Reviewers
To organize a comprehensive peer review, ERG selected six independent peer reviewers who
have demonstrated expertise in one or more of the following technical fields:1
Exposure assessment
Risk assessment
Statistics
PCB toxicology
Uncertainty analysis
Appendix A lists the six reviewers ERG selected for the peer review meeting, and Appendix C
includes brief bios that summarize most of the reviewers' areas of expertise. Recognizing that few
individuals specialize in every technical area listed above, ERG ensured that the collective expertise of the
selected peer reviewers sufficiently covers the five technical areas (i.e., at least one reviewer has
expertise in exposure assessment, at least one reviewer has experience in risk assessment, etc.).
To ensure the peer review's independence, ERG only considered individuals who could provide
an objective and fair critique of EPA's work. As a result, ERG did not consider in the reviewer selection
process individuals who were associated in any way with preparing the HHRA or individuals associated
with GE or any other specifically identified stakeholder.
^RG initially selected seven peer reviewers. Dr. Arnold Schecter was eliminated as a reviewer prior to the
peer review meeting due to the disclosure of a potential conflict of interest.
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1.2.2 Briefing the Reviewers
Given the large volume of site-specific information in the HHRA and the fact that none of the
reviewers had extensive experience with the Hudson River PCBs site, ERG organized a 2-day meeting
prior to the actual peer review to provide the reviewers with background information on the HHRA and to
tour the Upper Hudson River. The purpose of the meeting was strictly to familiarize the reviewers with
the site; the reviewers did not provide technical comments on EPA's reports during this briefing. A copy
of the minutes from this briefing can be found in Appendix G.
For additional background information on the site and its history, ERG provided the following other
documents to the reviewers. Reviewers were also pointed to additional Reassessment RI/FS documents
available on EPA's Web site (www.epa.gov/hudson).
Human Health Risk Assessment Scope of Work, July 1998.
Responsiveness Summary For Human Health Risk Assessment Scope of Work, April 1999.
Executive Summary for the Human Health Risk Assessment, Mid-Hudson River. December
1999.
Executive Summary for the Baseline Ecological Risk Assessment. August 1999.
Executive Summary for the Baseline Ecological Risk Assessment for Future Risks in the Lower
Hudson River. December 1999.
Executive Summary for the Revised Baseline Modeling Report. January 2000.
Suggested charge questions from the public for the HHRA. February and March, 2000.
To focus the reviewers' evaluations of the HHRA, ERG worked with EPA to develop written
guidelines for the technical review. These guidelines (the "charge") were presented during the briefing
meeting and asked the reviewers to address at least the following topics: the reasonableness of the
approaches used in the dose-response assessment, exposure assessment, and uncertainty analysis, and the
overall technical soundness, transparency, and clarity of the HHRA. A copy of this charge, which
includes many additional topics and questions, is included in this report as Appendix B.
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In the weeks following the briefing, ERG requested that the reviewers prepare their initial
evaluations of the HHRA and its Responsiveness Summary. ERG compiled these premeeting comments,
distributed them to the reviewers, and made copies available to observers during the peer review meeting.
These initial comments are included in this report, without modification, as Appendix C. It should be noted
that the premeeting comments are preliminary in nature and some reviewers' technical findings might
have changed based on discussions during the meeting. As a result, the premeeting comments should not
be considered the reviewers' final opinions.
The peer reviewers were asked to base their premeeting comments on the written materials
distributed by ERG mainly the HHRA and its Responsiveness Summaryeven though they received
many additional documents as background information. Though not required for this review, some
reviewers might also have researched site-specific reports they obtained from other sources.
1.2.3 The Peer Review Meeting
The six peer reviewers and at least 30 observers attended the peer review meeting, which was
held at the Holiday Inn in Saratoga Springs, New York, on May 30-31, 2000. Appendix D lists the
observers who confirmed their attendance at the meeting registration desk. The schedule of the peer
review meeting generally followed the agenda, presented here as Appendix E. As the agenda indicates,
the meeting began with introductory comments both by the designated facilitator and by the designated
chair of the peer review meeting. (These and other introductory comments are summarized below.) For
the remainder of the meeting, the reviewers provided many comments, observations, and
recommendations when answering the questions in the charge. The agenda included two time slots for
observer comments, which are summarized in Appendix F of this report. An ERG writer attended the
meeting and prepared this summary report.
On the first day of the meeting, Jan Connery of ERG, the designated facilitator of the peer
review, welcomed the six reviewers and the observers to the 1 '/2-day meeting. The peer reviewers then
introduced themselves, noted their affiliations, identified their areas of expertise, and stated that they had
no conflicts of interest in conducting the peer review, after which selected representatives from EPA and
EPA's contractors introduced themselves and identified their roles in the site reassessment.
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Following the introductions, Ms. Connery stated the purpose of the peer review meeting, identified
the documents under review, and described the steps in the peer review process preceding the meeting
(the March 2000 briefing and the compilation of pre-meeting comments). Ms. Connery reviewed the
agenda, at which time she explained the procedure that observers should follow to make comments and
pointed the group to the charge questions that the reviewers would be discussing. Ms. Connery explained
how Holly Hattemer-Freypeer reviewer and the technical chair of the meetingwould summarize
premeeting comments and then proceed with question-specific discussions. Lastly, Ms. Connery reminded
the reviewers that, at the end of the meeting, each reviewer would be requested to provide individual
recommendations.
Ms. Alison Hess, EPA's project manager for the Hudson River PCB reassessment, then
provided introductory remarks. She acknowledged several points identified in the reviewers' premeeting
comments on the HHRA that required clarification. EPA provided the reviewers with a table that
summarized these points. Ms. Hess and David Merrill, Gradient Corporation (EPA's contractor), then
briefly reviewed the technical issues presented in the summary table, providing clarification or additional
information. The presentation paralleled the issues raised in the charge questions. Specifically, EPA (1)
pointed to HHRA and Responsiveness Summary coverage of the newer PCB toxicity studies and its
assessment of child and prenatal exposures; (2) reviewed its approach to assessing fish intake rates; (3)
justified exposure duration selection; (4) provided additional perspective on the modeled fish
concentrations; (5) clarified Monte Carlo analysis methodologies, including justification for not performing
a two-dimensional analysis; and (6) provided the rationale for limiting the HHRA to the assessment of
potential cancer risks and non-cancer health hazards associated with PCBs in the river sediments (and
associated biota).
Following the introductory presentations, Ms. Hattemer-Frey began the technical discussions of
the peer review meeting. At the outset, she set the ground rules for the discussions. Specifically, she
explained that the reviewers were to discuss technical issues among themselves and were to consult with
EPA only for necessary clarifications. Ms. Hattemer-Frey emphasized that the reviewers' primary
purpose was to critically review the HHRA and make recommendations that would improve its technical
merit. She noted that the meeting would not focus on reaching a consensus on any issue.
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Ms. Hattemer-Frey worked with the peer reviewers to discuss and answer the questions in the
charge. Ms. Hattemer-Frey noted that common themes identified in the premeeting comments (i.e., issues
presented by more than two reviewers or strong comments made by at least one reviewer) would serve
as discussion points for the meeting. The remainder of this report summarizes the peer reviewers'
discussions and documents their major findings and recommendations.
1.3 Report Organization
The structure of this report reflects the order of questions in the charge to the reviewers: Section
2 of this report summarizes the reviewers' discussions on specific questions regarding the technical merit
of the primary components of the HHRA (i.e., hazard identification/dose-response, exposure assessment,
Monte Carlo analysis/uncertainty analysis, and risk characterization). Section 3 summarizes the
discussions on general questions posed to the peer reviewers; and Section 4 highlights the discussions that
led to the reviewers' final recommendations. Section 5 lists all references cited in the text. In these
sections, the reviewers' initials are used to attribute technical comments and findings to the persons who
made them.
As mentioned earlier, the appendices to this report include a list of the peer reviewers (Appendix
A), the charge to the reviewers (Appendix B), the premeeting comments organized by the authors
(Appendix C), a list of the observers who confirmed their attendance at the meeting registration desk
(Appendix D), the meeting agenda (Appendix E), summaries of the observers' comments (Appendix F),
and minutes from the March 2000 informational briefing for the reviewers (Appendix G).
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2.0 RESPONSES TO SPECIFIC QUESTIONS REGARDING THE HHRA
Peer reviewer discussions opened with responses to the seven specific charge questions related to
hazard identification/dose response, exposure assessment, uncertainty, and risk characterization issues.
The key points communicated during these discussions are summarized below and detailed in the
sections that follow.
Question 1 (Hazard Identification/Dose-Response). The reviewers agreed that the use of
current IRIS toxicity values for PCBs was appropriate, but strongly recommended that
the HHRA include expanded discussions on the uncertainties and the level of
conservatism of the CSF and RfD. Also, reviewers recommended that expanded
discussions be included on the impact the newer toxicity data (published since the
development of the IRIS values) may have on the risk assessment. Mixed opinions were
voiced as to whether the toxicity data should be incorporated into the quantitative
uncertainty analysis.
Question 2 (Fish Consumption Rates). The reviewers found the consumption rates used
in the HHRA to be reasonable for adults, but expressed concern regarding EPA's
reliance solely on the Connelly et al. (1992) data. They recommended that the Connelly
data be compared to the 1996 NYSDOH data to verify the assumptions made in the
HHRA regarding the representativeness of the study population (e.g., demographics).
Question 3 (Deriving Exposure Durations). The reviewers indicated that exposure
durations used in the HHRA were appropriate, but several reviewers stressed the
importance of clearly stating that the HHRA is a prospective study and evaluates
incremental risks only. Some reviewers noted the need to understand and include
information on PCB clearance rates and how they may apply to exposure duration.
Question 4 (Averaging Times). The reviewers agreed that the averaging times are
appropriate, but that shorter averaging times should be considered for the evaluation of
pregnant women (i.e., in utero exposures), nursing* infants, and young children.
Questions 5 and 6 (Monte Carlo Analysis/Uncertainty Analysis). Everyone agreed that
the uncertainty analysis in the HHRA needed to be expanded. Most reviewers
recommended that confidence intervals (error bars) be placed on all input parameters,
and ultimately on CTE and RME risk and HI estimates. The reviewers commented that
the Monte Carlo analysis, as presented in the HHRA, requires more explanation and
clarification.
Question 7 (Risk Characterization). The overriding message from reviewers was the need
for an expanded risk characterization section. Several reviewers emphasized the need to
provide more information to enable the decision-makers to put the risk numbers into
meaningful perspective and to provide sufficient information to proceed with the
feasibility study.
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Note: The reviewers' initials used to attribute comments are as follows: HHF (Ms. Holly Hattemer-Frey),
OH (Dr. Owen Hoffman), PS (Dr. Pamela Shubat), LS (Dr. Lee Schull), HS (Dr. Harlee Strauss), and
RW (Dr. Robert Willes).
2.1 Responses to Question 1
The first charge question pertains to the appropriateness of using the toxicity values for PCBs
currently provided in the Integrated Risk Information System (IRIS) and the adequacy of the discussions
of newer toxicity studies published since the development of these toxicity values:
Consistent with its risk assessment guidance, USEPA considered scientific literature on PCB
toxicity, both as to cancer and non-cancer health effects, published since the 1993 and 1994
development of the non-cancer reference doses (RfDs) for Aroclor 1016 and Aroclor 1254,
respectively, and since the 1996 reassessment of the cancer slope factors (CSFs). Based on the
weight of evidence of PCB toxicity and due to the Agency's ongoing reassessment of the RfDs,
USEPA used the most current RfDs and CSFs provided in the Integrated Risk Information
System (IRIS), which is the Agency's database of consensus toxicity values. The new toxicity
studies published since the development of the RfDs and CSFs in IRIS were addressed in the
context of uncertainty associated with the use of the IRIS values (see, HHRA, pp. 76-77 and
Appendix C). Please comment on the reasonableness of this approach for the Upper Hudson
River.
The six peer reviewers agreed that using currently available IRIS values was appropriate for
evaluating cancer and non-cancer effects in light of existing EPA risk assessment policy, including
EPA's goal for consistency across Superfund risk assessments. However, the reviewers also agreed that
newer PCB toxicity data need more in-depth discussion in the HHRA, especially given the magnitude of
the decisions that need to be made regarding contamination in the Upper Hudson River. The reviewers
recommended including a new section in Chapter 4 (Section 4.5) that discusses the most recent toxicity
data. Furthermore, the group agreed that the HHRA needed to include additional discussion on the
conservativeness of the CSF and the possible non-conservatism of the RfD. The reviewers indicated that
such discussions seemed to fit best into the Risk Characterization section. Several reviewers noted that
expanded discussion of these points would provide added perspective when interpreting the findings of
the quantitative risk assessment. Mixed views were presented regarding the need to incorporate
uncertainties in the toxicity data into the quantitative uncertainty analysis.
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A summaiy of peer reviewer comments related to Question 1 follows, presenting the various
points of view on how including expanded discussions on PCB toxicity would improve the risk
assessment and to what extent the uncertainty analysis (specific to toxicity data) needs to be enhanced.
Using existing values. All reviewers agreed that EPA's use of currently available IRIS toxicity
values in the HHRA was reasonable. Two of the reviewers emphasized that few other choices are
available in the context of a Superfund risk assessment and were therefore supportive of using
IRIS data (HS,PS). One reviewer pointed out that the use of IRIS values is adequate for screening
assessments, but when the HI exceeds 1 or cancer risk estimates exceed 10"6, then a closer look at
other data is necessary (OH).
Expanding the text to discuss the level of conservatism associated with the CSF and RfD. To put
cancer risk estimates into a real world context, one reviewer recommended that both the
uncertainties and conservativeness of the CSF be described to a greater extent in the HHRA
(RW). Two other reviewers agreed that the CSF is very conservative, but noted that, on the other
hand, the RfD may not be all that conservative and is probably set close to the levels at which
adverse effects might be expected, based on data in various published studies (e.g., Jacobson and
Jacobson, 1996; Winneke et al. 1998; Rogan and Gladen, 1991; and Brouwer, 1999) (HS,PS).
(See also Question 7)
Expanding the text to include more discussion on the newer PCB toxicity data. Several reviewers
commented that using the newer toxicity data would strengthen the scientific credibility of the
risk assessment. While it may not make a substantial difference in the risk assessment
conclusions, several reviewers agreed that the magnitude of the difference should be estimated
and discussed in the risk assessment, especially in light of the high profile nature of the Hudson
River site (LS,OH,PS,RW). That is, would use of the newer data result in toxicity values going
up, going down, or staying the same? It was recommended that the Kimbrough (1999) data be
used to develop a CSF that could provide additional perspective (LS,HHF). Another reviewer
questioned whether the same should be done for non-cancer endpoints using the Dutch studies
(PS).
One reviewer suggested that Chapter 4 in the HHRA include a new section that would present
the range of available toxicity data (PS). For example, she suggested including data compiled by
Tilson (1990, 1998).
Documenting uncertainties associated with the toxicity data. There were differing opinions
regarding the need for, or the feasibility of, including a quantitative uncertainty analysis of the
toxicity values. The group generally felt that, at a minimum, some sort of semi-
quantitative/qualitative discussion was needed to clearly identify the sources of uncertainty
pertaining to the toxicity criteria. One reviewer stated that discussions in the HHRA need to be
expanded to address the uncertainty associated with the use of the IRIS values (LS). For
example, this reviewer suggested that decision-makers need more information to understand the
significance of the HI of 150 estimated for child exposures.
One reviewer felt strongly that the limits on the uncertainty of the selected toxicity values need
to be quantified, noting that this was one of his greatest concerns regarding the risk assessment
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(OH). This reviewer thought that the HHRA should characterize how the uncertainty in the risk
estimates is influenced by the various input parameters, including the toxicity values. If the limits
of credibility cannot be quantified, then this reviewer feels the assessment is not scientifically
defensible even if it is adequate from a policy perspective. This reviewer emphasized the
importance of quantifying and understanding the limits of credibility on the risk estimates and
encouraged the use of non-classical statistics (e.g., Bayesian methods) to do so. He noted that
this type of analysis was performed when addressing PCBs at Oak Ridge National Laboratory
(i.e., confidence intervals were put on the CSFs and RfDs). This reviewer also noted that the
relative effects of the identified uncertainties needs to be discussed. That is, would the effect be
high, medium, or low? Also, to what extent would these uncertainties affect risk estimates? Will
the risk estimates go up, down, or stay the same?
Other reviewers agreed in principle (RW,LS,HHF). One reviewer noted that this issue has
historically been glossed over and encouraged a quantitative analysis if possible, commenting
that this could appropriately set the stage for future risk assessments, especially for PCB issues
(LS). Given the state of the art nature of this type of analysis, this reviewer thought that the
HHRA should either include a quantitative uncertainty analysis on the toxicity values or justify
why such and analysis cannot be done (LS). Another reviewer recommended that, at minimum,
EPA perform a comprehensive review of the PCB toxicity data to identify studies that might help
reduce uncertainties (PS).
Another reviewer pointed to the fact that the biggest uncertainty in toxicity data sets probably
relates to whether the right experiments have been conducted or whether the right endpoints have
been captured; she emphasized that these uncertainties cannot be quantified (HS). She cautioned
the group about being too quantitative, so that we do not suggest that we know more than we do.
This reviewer recommended expanding the toxicological profile included in the HHRA to
include more discussion on the derivation of the CSF and non-cancer effects, particularly
neurotoxic and immunotoxic effects. She indicated that this type of qualitative discussion on the
uncertainties was all that was necessary.
Should toxicity data be incorporated into the quantitative uncertainty analysis in the Hudson
River HHRA? One reviewer commented that the time has come for assessors to develop
distributions for the toxicity criteria for use in a quantitative uncertainty analysis/baseline risk
assessment; this would enable the generation of risk estimates for some percentile (LS). On the
basis of scientific merit and the fact that the PCB assessment for the Hudson River will set the
standard for other sites, it makes sense to develop toxicity criteria using this approach (LS,OH),
although one of the reviewers noted that it may not make a big difference on the outcome and the
decisions to be made (LS).
One reviewer reiterated that the limits of credibility should be quantified for the risk estimates,
recognizing, in response to an earlier statement, that all the toxicity studies that he thought
should have been done might not have been done (OH). He emphasized the importance of clearly
stating what is known and not known. Because it is likely that the toxicity criteria will be the
driving variable in the uncertainty analysis, this same reviewer stressed that this variable must be
included in the quantitative uncertainty analysis. Otherwise, it could mislead decision-makers.
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Another reviewer emphasized the importance of attempting to quantitatively describe the
following: (1) that the CSF represents an upper bound and therefore implies a "low" degree of
certainty, and (2) that the RfD will show a greater confidence (although it will be difficult to set
a distribution) (RW).
One reviewer (OH) briefly discussed how distributions are generated, pointing to (1) classical
statistics where analysts study data and grind them through some fitting routine to identify a
particular distribution, and (2) Bayesian methods that generate subjective distributions that come
from professional analysis of the state of the knowledge. The Bayesian approach, according to
this reviewer, is more appropriate for the uncertainty analysis of the risk estimates; it provides
the interval that contains the "true but unknown risk" for the defined population. This reviewer
also commented that Monte Carlo procedures are useful because they are robust in propagating
distributions, but cautioned that such procedures can be misused when simulating stochastic
processes. He encouraged EPA to consider his premeeting comments regarding this issue.
2.2 Responses to Question 2
The second question asked the reviewers whether the fish consumption rates used in the HHRA
are reasonable:
Since 1976, the New York State Department of Health has issued fish consumption advisories
that recommend "eat none" for fish caught in the Upper Hudson River. To generate a fish
ingestion rate for anglers consuming fish from the Upper Hudson River under baseline conditions
(i.e., in the absence of the fish consumption advisories), USEPA used data on flowing water
bodies in New York State (1991 New York Angler survey, Connelly et al., 1992) to derive a fish
ingestion rate distribution. The 50th and 90th percentiles were used for the fish ingestion rates for
the central tendency (average) and RME individuals (i.e., 4.0 and 31.9 grams per day, equivalent
to approximately 6 and 51 half-pound meals per year, respectively) (see HHRA, pp. 24 and 37).
Please comment on whether this approach provides reasonable estimates of fish consumption for
the central tendency and RME individuals for use in the point estimate calculations.
The six peer reviewers agreed that the central tendency and RME ingestion rates used in the risk
assessment were reasonable values for adults. Several reviewers commented that the Connelly et al.
(1992) study may not be adequate to describe the demographics of the study population and
recommended that EPA incorporate the most recent NYSDOH survey to verify if the Connelly study
captures the demographics of the exposed population. Specific reviewer comments are summarized
below.
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Adequacy of intake rates. The fixed intake rates of 6 (CTE) and 5 l(RME) half-pound meals
seemed reasonable and sufficient as voiced by one reviewer (OH). Nobody disagreed, but it was
noted that these rates were reasonable for adults only (PS,HHF).
Childhood and fetal exposures. Several reviewers commented that the HHRA did not adequately
address child and in utero exposures (PS, HS, HHF). Although the Monte Carlo analysis
considered child exposures, it did not appear to look at different ingestion rates for children (PS).
Reviewers noted that body burdens (in milligrams per kilogram per day) would be greater in
children and the fetus (LS,PS). By looking only at anglers and not their offspring, the HHRA
excludes a potentially important subpopulation. The reviewers strongly recommended that this
subpopulation be considered as part of the baseline HHRA (see also Question 4).
Reliance solely on Connelly (1992) data to define the angler population. All of the reviewers
questioned whether using the Connelly data accurately captures the demographics of the current
group of anglers on the Upper Hudson River. One reviewer strongly encouraged EPA to include
data from the 1996 NYSDOH study, which presents data on the angler population in this area,
including information on various subpopulations (PS).
Several reviewers pointed to Pam Shubat's written comments as clearly expressing pertinent
concerns related to this issue and encouraged EPA to review these comments carefully
(OH,LS,RW). One reviewer added that Dr. Shubat's comments coupled with GE's comments in
the Responsiveness Summary raise some important concerns about the Connelly data (LS). The
group recognized that the conclusions of the HHRA may not change, but, as written, the
scientific data supporting its conclusions are not completely defensible.
Using nonzero data from the Connelly study. While the exclusion of nonzero data from the
Connelly data was raised as an issue in the written premeeting comments, one reviewer
commented that this is not problematic (HS). Because of the way in which the data are being
used in the HHRA (i.e., looking only at the exposed population, not at the average consumption
across the population), the decision to exclude nonzero data is reasonable.
Evaluating subreach exposures. Two reviewers (OH, HHF) encouraged EPA to consider
evaluating exposures on a reach-by-reach or location-by-location basis. One reviewer pointed out
that some subsets of the populations may be harvesting fish from distinct reaches of the Upper
Hudson River; they are not randomly catching fish from the entire 40-mile stretch (OH). A
location-by-location analysis, according to this reviewer, also would be more consistent with
potential remediation considerations. This reviewer cautioned that "crude" estimates should not
be considered acceptable just because the HI was high (OH). The other reviewer thought an
evaluation of various subreaches of the Upper Hudson River was covered to some extent in the
Monte Carlo analysis but that the findings were buried in the text and graphical presentation of
the analysis and, therefore, not easily discernable (HHF). This reviewer noted that analysis on a
location-by-location basis would make the HHRA more realistic and technically sound, but she
also acknowledged that risk estimates would not likely change significantly. Another reviewer
commented that no information was provided suggesting that the various reaches would be
largely different (LS).
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Calculation offish tissue concentrations. Two reviewers (PS, HHF) indicated that the derivation
of the fish concentrations is not completely transparent in the HHRA. These reviewers
acknowledged that supporting documentation for the modeling is presented in other documents,
but strongly recommended that the description of the modeling efforts be expanded and clarified
in the HHRA.
Identification of species harvested. One reviewer commented that the fish species identified in
the Connelly study are not necessarily the same as those found and harvested in the Hudson
River (PS). She noted that the NYSDOH study identifies the study area as a bass (smallmouth
and largemouth bass) and blue gill (pan fish) fishery for shore anglers; this is not reflected in the
HHRA.
Possibility of commercial fishery. One reviewer (OH) questioned whether it was plausible that
commercial fisheries may exist under baseline conditions (i.e., with no institutional controls in
place). If so, why limit the targeted group to only anglers? Another reviewer (PS) informed the
group that in the absence of a specific advisory on the Hudson River, statewide advisories for all
fresh water fish would still apply.
Consumption of other species. Two reviewers (OH,HS) commented that it was not clear whether
EPA considered other wildlife species (e.g., eels and turtles), noting that the PCB accumulation
in turtles is considerably higher than in fish. One of these reviewers, therefore, recommended
that EPA consider the extent to which other biota might contribute to risk (OH). One other
reviewer suggested that EPA should, at minimum, state in the HHRA that not all wildlife species
that may be consumed from the Hudson River (and that may accumulate PCBs) have been
evaluated (PS).
Developing a conceptual site model. In light of the types of comments being made regarding the
sometimes unclear descriptions of the exposure scenarios evaluated by EPA, two reviewers
(HHF,LS) recommended that the HHRA include a conceptual site model that maps out all the
key issues and concerns, either in tabular or diagram format. For issues not addressed in the
HHRA, it was recommended that the rationale for exclusion be presented. This would improve
the transparency/clarity of the document. While the text of the HHRA explains why certain
scenarios and exposures were and were not considered, these discussions are not always clear
enough and sometimes not comprehensive enough. Others agreed. One reviewer noted, however,
that creating a conceptual model would be less critical if Table 2-1 in the HHRA were expanded
(see also General Questions, Section 3.0).
2.3 Responses to Question 3
The third charge question pertains to the adequacy of the site-specific exposure durations for the
fish ingestion pathway:
Superfund risk assessments often assume 30-year exposure duration, based on national data for
residence duration. However, because an angler could move from one residence to another and
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still continue to fish the 40 mile-long Upper Hudson River, USEPA developed a site-specific
exposure duration distribution based on the minimum of residence duration and fishing duration.
The residence duration was based on population mobility data from the U.S. Bureau of Census
(1990) for the five counties that border the Upper Hudson. The fishing duration was developed
from the 1991 New York Angler survey (Connelly et al., 1992). The 50th and 95th percentiles of
the distribution were used for the central tendency (average) and RME exposure durations (i.e.,
12 and 40 years, respectively). Please comment on the adequacy of this approach in deriving site-
specific exposure durations for the fish ingestion pathway (see, HHRA, pp. 23 and 49-57).
Everyone agreed that exposure duration rates are appropriate and changing them would not have
a significant effect on risk. Several thought that the HHRA should include a qualitative discussion on
PCB clearance rates and how they relate to exposure duration and the application of the RfD. Also,
several reviewers recommended that the HHRA clearly recognize that this is strictly a prospective
assessment and predicted risks do not account for previous exposure-related risks.
Incremental risks. While the reviewers agreed with the HHRA's assumption that exposure begins
in 1999, they also agreed that the text should clearly acknowledge that the current and future
risks estimated in HHRA are incremental and layered on to pre-existing risks.
One reviewer reminded the group that the risk assessment is prospective, not retrospective (LS).
He noted that the HHRA appropriately defines risk under baseline conditions, but does not
address past exposures where the above-described factors might affect exposure doses. For
clarity, EPA should clearly state up front in the HHRA, the purpose of the baseline risk
assessment (specifically, what it is and what it is not) (see also Question 7).
Exposure duration and PCB half-life. Several opinions were voiced on the significance of
residence duration on the interpretation of exposures. One reviewer commented that if neonates
are to be studied, it is important to look at the total uptake of PCBs over time because, in any
given year, the mother's breast milk concentrations will be determined by her life PCB-exposure
history (OH). He therefore encouraged that PCB clearance rates be considered when examining
the adequacy of the residence time assumption in the HHRA. Another reviewer (RW)
commented that for each exposure that is occurring, an equilibrium is assumed. Therefore,
changing the residence duration from 12 to 40 years does not affect how one interprets exposure
relative to the RfD. One reviewer agreed that this is how it is currently assessed, but is not
necessarily the best way (OH). Another reviewer commented that the practical reason for
choosing these duration times is related to declining PCB concentrations in the fish; the shorter
the averaging time, the higher the exposure (PS). Another reviewer (OH) argued that the
exposure rate (mg/day/weight) will be determined by the length of residence. Another reviewer
stated that if you stay within the dose metric of average daily dose, then you are looking at
shorter averaging times (HS). It was pointed out that the average daily dose is more practical, but
the cumulative dose may provide more accurate information.
One reviewer (OH) commented that all of the considerations listed above are important for a
greater understanding of how close the dose is to the threshold for effects. Another reviewer (PS)
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reemphasized the importance of a comprehensive presentation of the toxicologic data, in this
case to enable a better understanding of whether people are arriving at steady state and whether
site-specific conditions are consistent with conditions in the various toxicity studies. It was
therefore recommended (OH,RW) that the HHRA include a qualitative explanation that will
make readers aware of PCB clearance rates. One reviewer emphasized that an individual could
have a predetermined PCB body burden, which is dependent on the residence time of PCB
congeners in the human body, noting that animal studies may not be relevant (OH). Two other
reviewers (HS,RW) took this opportunity to stress the importance of communicating congener
issues (e.g., uncertainties).
2.4 Responses to Question 4
The fourth charge question also relates to the exposure assessment and asked the reviewers
whether the averaging times used to estimate exposure point concentrations are appropriate to address
non-cancer health hazards to both the CTE and RME individuals:
PCB concentrations in Upper Hudson River fish generally have declined in past decades and the
decline is expected to continue into the future. Therefore, to evaluate non-cancer effects for the
RME individual, USEPA used exposure point concentration in each medium (water, sediment,
and fish) based on the average of the concentrations forecast over the next 7 years (1999 to
2006), which gives the highest chronic dose considered in the HHRA. For the central tendency
exposure point concentrations, USEPA used the average of the concentrations forecast over 12
years (1999 to 2011), which is the 50th percentile of the residence duration developed from the
population mobility data (U.S. Bureau of Census, 1990). In addition, for completeness, USEPA
averaged the exposure concentration over 40 years (1999 to 2039) to evaluate non-cancer hazards
for the same time period over which cancer risk was calculated. Please comment on whether this
approach adequately addresses non-cancer health hazards to the CTE and RME individuals (see
HHRA, pp. 67-68).
The group agreed that the averaging times are generally appropriate, but that shorter averaging
times should be considered for evaluating doses to females and children. Specific comments are
summarized below.
Transparency of the fish concentration estimates. One reviewer reiterated that information on the
modeling efforts used to estimate fish concentrations, including validation information, is not
presented sufficiently in the HHRA (LS).
Use of a 7-year averaging time for the CTE and RME. Two reviewers stated that the 7-year
averaging time is appropriate for the RME, but they were inclined to use 7 years for the CTE as
well (HS,RW).
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Considerations for evaluating effects to children and developing fetuses. Several reviewers
recommended that shorter averaging times be considered when evaluating effects to fetuses and
children (HS,OH,HHF,PS). Especially because the HI for PCBs is so high (>100), one reviewer
(OH) encouraged EPA to look at the subchronic exposures that may affect such subpopulations.
In this case, exposure durations as short as 1 year should be considered.
The reviewers discussed special considerations related to breast milk and in utero exposures.
One reviewer questioned whether the 7-year averaging time was suitable for breast milk
exposure, concerned that this approach may underestimate exposures in cases where higher
exposures occur over a shorter period of time (RW). Another reviewer commented that the
driving factor for breast milk exposures is maternal body burden and the equilibrium level,
therefore she felt that in utero exposures would likely be more a concern from this perspective
(PS). A third reviewer noted that the underlying assumption is that the mother is at steady state
and the pharmacokinetics are available to determine body burdens in the fetus and nursing infant
(LS). It was also noted that toxicity criteria are not available for this subpopulation, but the group
agreed existing criteria could be used; it was emphasized that justification for the approach used
and all assumptions be clearly stated in the risk assessment (PS,HHF).
The group agreed on the following general guidelines for evaluating effects to pregnant and
lactating women:
Evaluate exposures of pregnant women (and consequently the developing fetus) and
nursing children. EPA should evaluate the appropriate exposure duration averaging for
this group. That is, this should be less than the 7 years used in the HHRA (e.g., 2 years).
Discuss qualitatively the applicability of the IRIS RfD to pregnant women and nursing
neonates, considering the issues related to potential neuro developmental effects of PCBs
in children.
As recommended by one reviewer in her premeeting comments (HS), use a margin of
exposure approach to evaluate the potential effects of PCBs on children; include in
utero, breast milk, and direct consumption exposures. Also, the dose should be
calculated using a short averaging time and high end concentrations of PCBs in fish
because the critical window of development is likely to be short. Note that this method of
calculating dose only applies to in utero exposure. (This approach assumes that transient
elevations in blood PCBs due to recent PCB-contaminated fish ingestion is important
with respect to toxicity, although the maternal body burden is probably the major
determinant to in utero exposure if averaged throughout gestation). Breast milk
exposures should be based on long-term averages because PCB concentrations in breast
milk reflect the mother's body burden of PCBs. In addition, it may be appropriate to
consider the in utero exposure separately as well as in combination, as most (but not all)
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of the neuro developmental effects associated with PCBs in the cohort studies cited
below appeared to be associated with in utero exposures:
Jacobson and Jacobson, 1996.
Rogan and Gladen, 1991.
Winneke et al., 1998.
Communicating the degree of conservatism in the analysis. To aid in risk management decisions,
one reviewer felt that the averaging times are reasonable, but thought that the HHRA should
clearly state that these numbers are not overly conservative (RW).
Should background exposures be considered? One reviewer questioned whether and how
background exposures should be taken into account. The group recognized that this is beyond the
scope of the risk assessment, since the assessment focuses on incremental risks. One reviewer
(OH) emphasized, however, that background levels may be relevant when assessing threshold
effects. Another reviewer (RW) noted that background exposures to PCBs are likely associated
with an HI of less than one and are therefore not a big issue. However, this same reviewer added
that if PCB congeners are acting like dioxins/furans (on a toxicity equivalence basis),
background exposures might be "significant" (e.g., HI ranging from 0.1 to 10). It was stressed
that, at minimum, these issues be brought to the attention of the risk manager (see also Question
7).
2.5 Responses to Questions 5 and 6
The fifth and sixth charge questions asked the reviewers to comment on the adequacy of the
Monte Carlo/uncertainty analysis. Regarding the adequacy of the Connelly data, see also the summary of
Question 2 discussions (Section 2.2).
Question 5
USEPA policy states that probabilistic analysis techniques such as Monte Carlo analysis, given
adequate supporting data and credible assumptions, can be viable statistical tools for analyzing
variability and uncertainty in risk assessments (USEPA, 1997). Consistent with this policy,
USEPA used a tiered approach to progress from a deterministic (i.e., point estimate) analysis to
an enhanced one-dimensional Monte Carlo analysis of the fish ingestion pathway (see HHRA,
Chapter 3, pp. 33-59). Please discuss whether this Monte Carlo analysis makes appropriate use of
the available data, uses credible assumptions, and adequately addresses variability and
uncertainty associated with the fish ingestion pathway (e.g., defining the angler population, PCB
exposure concentrations, ingestion rates, exposure durations, cooking losses) qualitatively or
quantitatively, as appropriate, in the analysis (see HHRA, pp. 72-74).
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Question 6
For the Monte Carlo analysis, USEPA evaluated a number of angler surveys, but excluded local
angler surveys, such as the 1996 and 1991-1992 Hudson Angler surveys (NYSDOH, 1999;
Barclay, 1993), due to the fish consumption advisories. The 1991 New York Angler survey
(Connelly et al., 1992) was used as the base case and other surveys were used to address
sensitivity/uncertainty in fish ingestion rates (see HHRA, pp. 37-46). Please comment on the
adequacy of USEPA's evaluation and use of existing angler surveys in the Monte Carlo analysis
of the fish ingestion pathway.
Per the reviewers' request, at the outset of discussions pertaining to the HHRA analysis of
variability and uncertainty, EPA provided further clarification as to why a one-dimensional sensitivity
analysis was performed instead of a two-dimensional Monte Carlo analysis, and why Monte Carlo
procedures were not used in the uncertainty analysis. EPA indicated that it chose to perform a sensitivity
analysis rather than a two-dimensional Monte Carlo analysis and quantitative analysis on uncertainty
because probability distribution data (on variability and uncertainty) were not robust enough.
In response, one reviewer recommended, at minimum, that the reasoning behind the analysis be
more explicitly stated in the HHRA (LS). The reviewers generally agreed, however, that the uncertainty
analysis in the HHRA needs to be enhanced. Most reviewers recommended that confidence intervals
(error bars) be placed on all input parameters, and ultimately on CTE and RME cancer risk and HI
estimates. It was recommended that the HHRA include a table that defines variability and uncertainty
(confidence intervals) and distribution (when available) for all input parameters. Regarding the Monte
Carlo analysis presented in the HHRA, several reviewers commented that it was at times difficult to
follow and therefore requires more explanation and clarification.
Specific topics discussed by reviewers are summarized below.
Interindividual variability analysis. One reviewer stressed that the Monte Carlo analysis in the
HHRA has nothing to do with uncertainty: it is only an expression of interindividual variability
of exposure for a defined subgroup of the population (i.e., licensed anglers fishing the reach of
the river under study) (OH). This reviewer noted that it did not make sense to perform thousands
of simulations when evaluating data from a single angler study with only 221 respondents. This
reviewer questioned whether this type of analysis of interindividual variability is truly necessary
when exposures to the study population are clearly of regulatory concern. He thought that
looking at interindividual variability is only critical when assessing the total population exposed,
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not just a targeted analysis of anglers. It was noted that in such a case, it would be important to
look at the size of the total population.
Placing confidence intervals on the CTE and RME risk estimates. Most of the reviewers
indicated the need to understand whether the uncertainty at the central tendency or RME causes
EPA to understate or overstate risk and commented that this type of analysis is lacking in the
HHRA. At minimum, confidence or credibility intervals need to be placed on the CTE and RME
risk estimates (HHF,OH,LS,RW). This involves understanding the uncertainty on each of the
input parameters. One reviewer stated that addressing each of the parameters as subjective
probability distributions would have been more appropriate in the Monte Carlo analysis, rather
than the sensitivity analysis that was performed (OH). This reviewer stated that instead of using
Monte Carlo to simulate interindividual variability, it may be preferable to pick defined
reference representative individuals for the high-end, mid-point, and low-end of the distribution
and do Monte Carlo to estimate uncertainty at each of these points (OH).
Two reviewers discussed evaluating the effect of having a high degree of variability (OH,HS).
One reviewer stated that in such a case we simply explain why that variability exists and
condition the assessment on the CTE or RME. A brief discussion followed as to why the
percentiles presented in the HHRA sensitivity analysis were not complete enough. One reviewer
stated that the analysis was neither complete nor completely interpretable (OH). To enable a
better interpretation, he would like to have seen the following included: a presentation of
parameters that expressed stochastic variability, the uncertainties on the mean fish
concentrations, the uncertainty associated with fishing at other locations, and the uncertainty of
the toxicity values.
In closing these discussions, the group agreed that uncertainty needs to be better understood to
enable an informed decision regarding the extent to which remedial actions, including the
existing fishing advisory, are needed. Therefore, the uncertainty analysis in the HHRA needs to
be enhanced.
Use of Bayesian methods. Reiterating points made during Question 1 discussions, one reviewer
(OH) strongly encouraged the application of Bayesian methods in the uncertainty analysis.
Another reviewer (RW) commented that he has successfully used Bayesian methods to generate
error bars to see where significant shifts in output are indicated and to identify factors that
contribute greatest to these shifts in output. He noted that this type of analysis becomes more
important in the next phase of the assessment (selecting remedial alternatives). That is, what
parameters might be most sensitive to the remediation efforts. He noted, for example, that the
HHRA does not provide information on which parameters are the most critical for "Scenario A"
versus "Scenario B." While perhaps not critical to the baseline risk assessment conclusions, this
reviewer was concerned whether this information would be available for the remedial alternative
selection step.
These same two reviewers emphasized that data will clearly not be available for all input
parameters, but that enough information is available to make some assumptions and initiate a
quantitative analysis. This type of quantitative analysis will identify parameters that drive risk
estimates and will help identify parameters for which more data may be needed.
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Input parameter summary table. One reviewer (LS) commented, and all other reviewers agreed,
that a critical first step in evaluating uncertainty is to clearly identify the uncertainty and
variability for all input parameters, and where possible define distributions. The group
recommended that this information be presented within the HHRA in tabular form, possibly
following the example provide in Table 2-1 on the following page. One reviewer commented that
clearly presenting this information is critical to helping the decision-maker understand why
different approaches were taken and how decisions were made in the risk assessment process.
For example, why was only a point estimate used and not the probability on a distribution, or
how is a particular parameter likely to affect the risk estimate (LS,RW)? One reviewer noted,
however, that this is only one step in the process and emphasized that it only looks at one
variable at a time (OH). For example, in the case of the HI of 150 for the child, we do not know
how the output is being affected by compounding conservative assumptions made in the risk
assessment. This reviewer reemphasized that in absence of distribution data, expert judgment can
and should be used to quantify the uncertainty. Others (PS) felt less comfortable in advising or
directing the risk assessor on how to apply this type of judgment.
One reviewer suggested introducing/describing uncertainty and variability information in
individual sections (i.e., in the toxicity and exposure assessment sections) and then carried
forward into the uncertainty analysis (PS).
Comments specific to the HHRA Monte Carlo analysis. The meeting chair summarized reviewer
premeeting comments on the Monte Carlo analysis as follows:
Fish concentrations were not allowed to vary in the analysis.
The fraction of fish consumed from the Hudson River was assumed to be 100% and not
allowed to vary.
Assuming 0% cooking loss is too conservative.
Possible changes in fish consumption rates over the exposure period were not evaluated
The possibility of consumption of a single species was not evaluated.
The reviewers discussed these issues and others during the meeting. An overview of this
discussion follows.
General comments. Several reviewers expressed some confusion regarding the
assumptions used and decisions made in the Monte Carlo analysis. In general, the
reviewers recommended that the presentation in the HHRA be revised to clarify the
approach, both in terms of why and how the analysis was developed. For example, some
factors may be kept fixed with justification, but the risk assessment document needs to
clearly explain why (LS).
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Table 2-1
Sample Uncertainty Table
Parameters Used for Fish Ingestion Pathway
Risk Endpoint: Reasonable Maximum Exposure Hazard Index
Parameter
Units
Point
Estimate
Uncertainty
Rationale
Fish ingestion
kg/day
0.032
fixed
Defined value for
RME
Fish ingestion
kg/day
0.032
0.015-0.054
(uniform
distribution)
Range of plausible
values for the RME
Cooking loss
0
0.1-0.4
(uniform
distribution)
Plausible range from
review of literature
PCB concentration
mg/kg
0.3
0.5-5.0
(lognormal)
Modeled uncertainty
from...
Bioaccumulation
(sediment/fish)
1.0
1.0-10.0
(log uniform)
Uncertainty in
bioaccumulation from
sediment to fish
Fraction of fish
caught in Upper
Hudson River
-
1.0
fixed
Defined as part of
review
Etc.
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Fish concentrations were held constant in the analysis. Reviewers (PS,HS) expressed
concern that the uncertainties in the fish concentration were not clearly described in the
HHRA. It was recommended that points relevant to describing the variation in fish
concentrations be carried over from the modeling reports to provide greater transparency
in the HHRA (HS). Another reviewer (OH) commented that, while not likely a driver in
the uncertainty of the assessment, he would like to see the standard error on the mean
fish concentrations; it is of particular interest in seeing how PCB concentrations decrease
over time and also to understand inter-species differences.
Cooking loss. Although EPA indicated as a point of clarification that error bars were
generated with the elements of uncertainty studied in the HHRA (e.g., cooking loss, fish
ingestion), one reviewer (OH) did not feel this was easily discernable in the HHRA.
Another reviewer (HS) pointed out that cooking loss is fixed in the point estimate, not in
the Monte Carlo analysis.
Fish ingestion rates. One reviewer expressed concern that the presentation of fish
ingestion rate in the HHRA might be misleading and suggest a false sense of certainty
(PS). This reviewer noted that in the analysis the meal size is fixed and assumed and
frequency of consumption was the variable studied. While she agreed that the choice in
meal size is reasonable, she wondered if treating these two parameters separately would
provide a more informed account of health risks.
2.6 Responses to Question 7
The last specific question asked the reviewers to comment on the adequacy of the risk
characterization in estimating the relative cancer risks and non-cancer hazards:
The risk characterization section of the HHRA (Chapter 5, pp. 67-80) summarizes cancer risks
and non-cancer hazards to individuals who may be exposed to PCBs in the Upper Hudson River.
Please comment on whether the risk characterization adequately estimates the relative cancer
risks and non-cancer hazards for each pathway and exposed population. Have major uncertainties
been identified and adequately considered? Have the exposure assumptions been described
sufficiently?
The group agreed that the risk characterization section should be expanded and clarified to
address several issues. First, the conservatism of the CSFs and the possible non-conservatism of the RfDs
should be discussed. Second, to assist decision-makers, the group encouraged EPA to include more
information to enable a more extensive interpretation of the risk estimates. Third, the group
recommended that the risk characterization section include a brief qualitative discussion on background
exposures and the fact that the population may have been pre-exposed to PCBs. Lastly, several reviewers
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stressed that enough information needs to be included to enable the back calculation of risk-based
remedial goals in the next phase of the assessment.
Many of the points raised during previous discussions were reiterated and discussed in the
context of risk characterization during the Question 7 discussions. Highlights of these discussions are
presented below.
General Comments. One reviewer (LS) commented that the Risk Characterization section was
the most disappointing section in the HHRA. It fails to answer a key question: "What do we
make of all of this?" More perspective needs to be provided to support risk management
decisions and to better inform the public of what risk estimates mean. This section should
explain that the HHRA is a theoretical upper bound prospective study that is designed to ensure
that risks are not underestimated; however, an explanation is needed of what the risk estimates
mean in the context of the real world. He recommended that Chapter 5 be expanded, especially
the uncertainty discussions. Others agreed.
One reviewer stated that he felt strongly that the Risk Characterization section include "full
disclosure" of everything that should be taken into account in understanding and interpreting the
risk assessment findings (OH).
Evaluation of background and pre-1999 exposures. The reviewers agreed that the issue of
background and past exposures needs to be acknowledged in the HHRA, noting that this
evaluation could be important in making risk management decisions and calculating remediation
goals. Most reviewers agreed that this could be addressed qualitatively. One reviewer suggested,
at a minimum, including a statement that indicates that other sources of PCBs exist (although
risks associated with Hudson River exposures likely override background) and that past
exposures may have occurred (RW). This, he noted, would help clarify within the HHRA that
this is an incremental risk assessment. Another reviewer (OH) reiterated that, wherever feasible,
"confounding" factors should be handled quantitatively. Two reviewers emphasized that
background concentrations of PCBs will have an influence on remedial decisions, especially
during the feasibility study (HHF,RW).
Conservatism of the cancer slope factor. One reviewer (RW) reiterated the importance of
recognizing extreme conservatism of the PCB cancer slope factor. In the case of PCBs, where no
compelling evidence exists that liver tumors observed in animal studies are predictive of human
liver cancer, he strongly recommended enhancing existing text to emphasize the conservatism of
the slope factor and to provide additional perspective on interpreting cancer risk estimates. For
example, he noted that applying the current slope factor to current PCB background levels would
predict liver cancer incidence between 30 and 45 percent. The total liver cancer incidence from
all causes reported in the United States is only between 1 and 5 per 100,000. Several other
reviewers agreed that this type of reality check is helpful, but recognized that regulators are
looking at individual risk not population risk. Furthermore, another reviewer (HS) stressed that it
is not the intent of the risk assessment to predict liver cancer or cancer at any other site; the CSF
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has been developed for regulatory purposes. Another reviewer (LS) replied that it is often
interpreted in that way and that is why added perspective needs to be provided in the HHRA.
One reviewer (RW) commented on the importance of considering or explaining how the new
cancer guidelines might influence the interpretation of cancer risk estimates, noting that the CSF
does not take into account mechanism of action, weight of evidence, etc. EPA indicated that it
did address the 1996 cancer reassessment and the new cancer guidelines in the HHRA. Another
reviewer (OH) expressed his concern about the credibility of the regulatory approach in
estimating cancer "risks" and strongly agreed that information on animal data, mechanism of
action, and relevance to humans is needed to be put theoretical risk numbers into perspective
("When are risks real versus artifacts of the regulatory process?").
Lastly, another reviewer cautioned the need to err on the side of conservatism given uncertainties
in the mechanism of action (PS). PCBs may not be a liver carcinogen in humans but could still be
a promoter. Therefore, she noted that more than the potential for liver cancer should be
examined. She, therefore, advised that "reality checks" be carefully presented with a thoughtful
review of the state of the science regarding PCB carcinogenicity.
Individual versus population risk'The, peer reviewers voiced slightly differing opinions as to
whether the size of the exposed population should be factored into the risk analysis. One
reviewer (OH) commented, for example, that if a 10"4 cancer risk is estimated and the exposed
population is less than 10,000, then no observable adverse effects are likely; he questioned
whether the regulatory process is really increasing quality of life by reducing a number that is
near zero to a number that is even closer to zero. In light of this, this reviewer reiterated the need
for such reality checks when interpreting risk numbers. He therefore indicated that it was
important to give the population size some weight in interpreting the risk numbers. Another
reviewer (HHF) commented, even if the population size in the above example is less than 10,000,
that does not mean that the risk is zero. A third reviewer (LS) added, however, that knowing the
size of the population might help the decision-maker in deciding what to do with the 10"4 risk
estimate.
As stated earlier, another reviewer (PS) reminded the group that risks are not regulated based on
the size of the population exposed; instead, regulators identify an "acceptable risk" in the
population, not an "acceptable number" in the population that can get cancer. The first reviewer
argued, "from a scientific point of view," all different perspectives should be taken into account,
not just the regulatory perspective. Another reviewer reemphasized that EPA regulates based on
individual risk and that this type of discussion moves away from reviewing the technical merit of
the HHRA (HS).
Including confidence intervals on point estimates. In light of the issues raised above, the group
reemphasized the need to place confidence intervals around the point estimates to provide some
added perspective. This is needed to help the risk manager and others understand what the
theoretical upper bound estimates mean (HHF, OH, HS, LS, RW). In addition, reviewers pointed
to language in EPA's cancer guidelines that indicates that the true risk is likely lower, and may
even be zero (HHF,PS).
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Multiple chemical exposures. One reviewer raised the issue of potential risks from exposure to
other contaminants, questioning whether PCB exposures in the Upper Hudson River are expected
to dominate cancer risk and non-cancer hazards (OH). Another reviewer questioned whether the
data for other contaminants are available and recommended, at a minimum, that any such data be
discussed qualitatively in the HHRA to show the potential for other or additive effects (HHF).
Risk-based cleanup goals. While it was recognized that the HHRA does accomplish the objective
of identifying the need for remedial actions for sediment, many of the issues raised during this
peer review (e.g., mixtures, bioaccumulation modeling, etc.) will become even more important
when back-calculations are performed to establish cleanup goals (LS). It was questioned whether
this type of information belongs in the baseline risk assessment. One reviewer indicated that she
felt that a baseline risk assessment has the obligation to provide all the information needed to
calculate risk-based cleanup levels (HHF). Another reviewer noted that the parameter table
recommended by the group (see previous discussions) will be helpful in comparing remedial
options (RW). In light of these discussions, two reviewers stated that they felt even more
adamant about the need to include the following: a quantitative analysis of uncertainties,
population size information, and information on possible co-contaminants (OH,LS).
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3.0 RESPONSES TO GENERAL QUESTIONS REGARDING THE HHRA
After discussing the seven specific questions in the charge, the reviewers discussed two general
questions. These questions generally pertained to how well the HHRA and the Responsiveness Summary
met overall risk assessment goals in terms of overall clarity, transparency, and adequacy in characterizing
risks to exposed populations, including children. Reviewers were also asked to comment on any strengths
and weaknesses in the HHRA not covered in the specific charge questions.
Specifically, the general charge questions asked the reviewers:
A goal for risk assessments is that they be clear, consistent, reasonable and transparent and
adequately characterize cancer risks and non-cancer hazards to the exposed population, including
children (USEPA, 1995). Based on your review, how adequate are the HHRA and
Responsiveness Summary when measured against these criteria?
Please provide any other comments or concerns, both strengths and weaknesses, with the HHRA
not covered by the charge questions, above.
The peer reviewers raised a variety of issues, as summarized below.
Flood plain soils and farming exposures. Soil contamination resulting from flooding is
mentioned in the HHRA as a potential exposure pathway but is not quantified. One reviewer
noted that this could be a significant pathway (e.g., dairy farm on river's edge) (RW). EPA
pointed out that the HHRA and its Responsiveness Summary include a discussion of farms; this
pathway was not evaluated quantitatively because the reassessment focused on river sediments
and only limited data are available for characterizing PCBs in soils adjacent to the river. Several
reviewers commented that direct and indirect exposures to soil need more explicit attention in the
HHRA (RW, OH, HHF, LS). No discussion of the soil pathway is included in Table 2-1 in the
HHRA.
Table 2-1. At minimum, the reviewers recommended that Table 2-1 be expanded and clarified.
Specifically, it should be more comprehensive and include all pathways considered and indicate
which pathways were evaluated quantitatively, qualitatively, or not at all (and why).
Selection offish species assessed in the HHRA. Two reviewers reiterated that the HHRA was not
transparent in its discussion regarding fish tissues levels and how species and size were selected
(HHF,PS) (see also Question 2). After speaking with a fisheries contact, one reviewer (PS) found
the analyses in the HHRA to be generally satisfactory, but felt clarification was needed. The
HHRA does not and should list all species present and caught in the Upper Hudson River.
Predominant species and sizes fished in this reach of the river should be clearly identified. In
addition, more explicit information is needed on the following: Are EPA's modeled
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concentrations skin on fillet data? Are the sizes chosen for risk analysis comparable to sizes that
anglers keep? What is the effect of "crunching?" Are data available that address the age of the
fish consumed and the relationship to PCB concentrations?
Consideration of child and in utero exposures. As identified during exposure assessment
discussions (see Questions 2 and 4), the importance of characterizing risks to fetuses, infants, and
children was reemphasized (HS).
Transparency of decision criteria. Two reviewers expressed concern that the HHRA did not
always clearly explain and justify why various decisions were made (e.g., exposure assessment
and Monte Carlo analysis) (PS, HHF). Although EPA noted that Phase 1 and scope of work
documents associated with the PCB reassessment contain more detailed information on how
decisions were made, several reviewers stressed the need to restate some of this information in
the HHRA, especially issues critical to the risk estimates (e.g., fish concentrations). Again, the
reviewers emphasized that expanding and clarifying how and why things were done will improve
the scientific reasonableness and transparency of the HHRA. Also, it will ultimately aid in risk
management decisions (HHF,OH,HS,LS,PS,RW).
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4.0 REVIEWERS' OVERALL RECOMMENDATIONS
The peer reviewers were asked to provide an overall recommendation, based on their review of
the HHRA and the peer review meeting discussions. Specifically, reviewers were asked to select one of
the following recommendations and explain why:
The HHRA is
Acceptable as is.
Acceptable with minor revision (as indicated).
Acceptable with major revision (as outlined).
Not acceptable (under any circumstance).
Prior to presenting individual recommendations, the peer reviewers held open discussions and
worked together to prepare conclusion statements and recommendations. The outcome of this effort is
presented in Section 4.1. The individual reviewers' final statements are presented in Section 4.2.
4.1 Summary of Specific Recommendations
This section presents a summary of reviewer comments and recommendations. These comments
were compiled by the peer reviewers throughout the course of the 1 '/2-day meeting and discussed in the
final session to ensure that key points were adequately captured. The presentation is organized by charge
question.
Question 1 (Hazard Identification/Dose Response)
1) The reviewers agree that it is appropriate to use IRIS values, but recommend adding a new
section to Chapter 4 (Section 4.5). This section needs to quantitatively and/or qualitatively
discuss the more recent studies on both cancer and non-cancer endpoints to determine what effect
these studies might have on risk estimates (Will risk estimates go up, down, or stay the same?).
2) Section 5.3.2: List all sources of uncertainty pertaining to the toxicity criteria used to calculate
the point estimates (i.e., IRIS data) and qualitatively discuss the effect on risk (high, medium,
low) and the extent to which the toxicity data selected for use in the assessment would affect risk
estimates (Will the risk estimates go up, down, or stay the same?). Uncertainties include the use
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of animal data, uncertainty factors, modifying factors, and the high-to-low dose extrapolation
model.
3) Should toxicity data be incorporated into the quantitative uncertainty analysis? Some reviewers
strongly encouraged a quantitative evaluation of the uncertainty associated with the toxicity data
and that this information be incorporated within the overall uncertainty analysis of HI and risk.
Other reviewers believe that qualitative discussion of the uncertainty associated with the toxicity
data is sufficient.
Question 2 (Exposure Assessment)
1) Fish ingestion rates used in the point estimates are reasonable for adults.
2) Reviewers recommend that EPA incorporate the most recent NYSDOH survey to verify if the
Connelly et al. (1992) study captures the demographics of the exposed population (see Pam
Shubat's premeeting comments for more details).
3) Risk assessment text is not transparent in describing how fish concentrations were derived. The
text needs to be expanded and clarified. The text needs to include information on the uncertainty
and variability in the average concentration in fish identified by species, location, and variations
in time.
4) Assuming that individuals consume fish only from the Upper Hudson River seems unreasonable
(too conservative).
5) Some reviewers believed that evaluating exposures on a location-by-location basis would better
characterize exposed subpopulations. Other reviewers felt this issue was minor.
6) Justification for any scenarios and/or pathways (e.g., soil-related pathways) that were not
quantified in the risk assessment should be added to Table 2-1.
7) All aquatic species that may be consumed (e.g., turtles and eels) may not have been evaluated,
which could result in an underestimation of risks. A discussion of this issue in the uncertainty
analysis would be desired.
8) Reviewers would like information on the size of the exposed population.
Question 3 (Exposure Assessment)
1) The HHRA assumes that exposure begins in 1999. The text should emphasize that the risks
estimated in this assessment are incremental and overlay previous exposures/risks.
2) Recommend including discussion of PCB clearance rates (i.e., half-life of PCB in the human
body) and how they relate to exposure duration and the application of the RfD.
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Question 4 (Exposure Assessment)
1) The averaging times used are appropriate except for evaluating effects to pregnant and nursing
women (see recommended guidelines presented in Section 2.4)
2) Modeling efforts used to calculate fish concentrations and validation of models are not
adequately discussed in the HHRA (see point 3 under Question 2).
3) For noncancer effects and some receptors, an exposure duration of <7 years may be appropriate
(e.g., child exposure of 1 year). In addition, some reviewers suggested that the exposure duration
for the CTE and RME scenarios both be 7 years.
Questions 5 and 6 (Uncertainty Analysis)
1) Include a table that defines variability and uncertainty (confidence intervals) for all input
parameters. For those parameters for which a distribution is defined, the rationale for the
distribution should be described (see Table 2-1 presented earlier in this report).
2) The uncertainty analysis needs to be enhanced. CTE and RME risk estimates and HI values need
to have confidence intervals.
3) The Monte Carlo presentation was difficult to follow and not transparent. Additional
clarification is warranted.
Question 7 (Risk Characterization)
1) Qualitatively acknowledge that background exposures and the fact that this population has been
pre-exposed is likely to increase the HI and cancer risk estimates. Evaluating background and
pre-exposures could be important in calculating remediation goals and/or for risk management
issues.
2) Expand/clarify Chapter 5
Discuss the conservatism of CSFs and the potential non-conservatism of RfDs and their
effects on the final risk estimates.
Provide a better interpretation of results, especially a discussion of the fact that the
cancer risk estimates are theoretical and upper-bound. The true cancer risk is likely to be
lower and could even be zero.
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General Questions 1 and 2
1) Discuss the potential interactive and cumulative effects that other chemicals, which may also be
present in the Upper Hudson River, may have on PCB toxicity.
2) The baseline HHRA should include all information/data necessary to calculate a range of fish
concentrations necessary for risk management objectives.
3) The HHRA should bring in the necessary and relevant information from other supporting
documents to make the risk characterization section transparent (e.g., calculation of fish
concentrations).
4.2 Individual Reviewer Recommendations
In summary, all six reviewers found the HHRA to be acceptable, but with minor to major
revisions recommended and they commended EPA on the quality and extent of the effort that went into
the HHRA. A summary of the peer reviewers' final statements on the HHRA, in the order they were
given, follows:
Dr. Owen Hoffman. As a record of disclosing an issue of regulatory concern, Dr. Hoffman stated
that the HHRA is acceptable as written. However, he stated major revision is needed to make the
HHRA more scientifically sound and defensible. Dr. Hoffman indicated that the limits of
credibility of the risk estimates should be defined to take the HHRA to its needed next level.
Dr. Robert Willes. Dr. Willes stated that he found the document to be acceptable with major
revision. He stated that the types of revisions discussed throughout the workshop are critical to
making the HHRA more usefiil and applicable to the feasibility study. He noted that the
document is acceptable as written from a regulatory point of view.
Dr. Harlee Strauss. Dr. Strauss also stated that the HHRA was acceptable with revisions. Dr.
Strauss indicated that the recommendations communicated by the peer reviewers will strengthen
the report, but will not change the regulatory conclusion. Dr. Strauss reiterated that reviewers'
analyses and discussions have disclosed that the HHRA is too conservative in some respect, but
possibly not conservative enough on other fronts. Dr. Strauss noted that she does not believe that,
in the end, conclusions will change from a regulatory perspective.
Dr. Pamela Shubat. Dr. Shubat stated that the HHRA was acceptable with minor revision. Dr.
Shubat commented that the primary deficiency from her point of view was the failure to
adequately assess risks associated with fetal, childhood, and maternal exposures. Dr. Shubat
indicated that she does not feel as strongly about the need for the HHRA to "push the envelope."
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Dr. Lee Shull. Dr. Shull indicated that the HRHA was acceptable with "minor to major"
revision. Especially in light of the close scrutiny that the Hudson River reassessment has
received and will continue to receive, Dr. Shull stated that he felt strongly about taking the
science of risk assessment to a higher level. He encouraged EPA to satisfy the special needs of
this site and take evolving science into account when revising the risk assessment. He agreed that
some of the recommended changes discussed during this peer review workshop will not change
the bottom line but again emphasized that the changes will improve the utility of the document
and make it as "right" as it can be.
Ms. Holly Hattemer-Frey. Ms. Hattemer-Frey accepted the document with "revisions " needed.
She stated that she feels strongly that the HHRA needs to be more transparent and complete if it
is expected to support the calculation of remediation goals. Dr. Hattemer-Frey indicated that with
the implementation of the peer reviewer recommendations, a revised HHRA should be able to
serve that purpose. She noted that implementing recommended changes such as further
evaluating child and in utero exposures and expanding the uncertainty analysis, will afford easier
and justifiable back-calculations of acceptable risk levels.
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5.0 REFERENCES
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New York.
Brouwer, A. et. al. 1999. Characterization of potential endocrine-related health effects at low-dose levels
of exposure to PCBs. Environmental Health Perspectives Volume 107 (Supplement 4):639-649
Cogliano, V.J. 1998. Assessing the cancer risk from environmental PCBs. Environmental Health
Perspectives 106(6):317-323.
Connelly, N.A., B.A. Knuth, and C.A. Bosogni. 1992. Effects of the Health Advisory Changes on Fishing
Habits and Fish Consumption in New York Sport Fisheries. Human Dimension Research Unit,
Department of Natural Resources, New York State, College of Agriculture and Life Sciences, Fernow
Hall, Cornell University, Ithaca, New York. Report for the New York Sea Grant Institute Project No.
R/FHD-2-PD, September 1992.
Jacobson, J.L. and S.W. Jacobson. 1996. Intellectual impairment in children exposed to poly chlorinated
biphenyls inutero. New England J. of Med. Sep 12;335(ll):783-9.
Kimbrough, R.D. et al. 1999. Mortality in male and female capacitor workers exposed to polychlorinated
biphenyls. J Occup Environ Med. Mar;41(3): 161-71.
New York State Department of Health (NYSDOH). 1999. Health Consultation: 1996 Survey of Hudson
River Anglers, Hudson Falls to Tappan Zee Bridge at Tarrytown, New York. February 1999.
Rogan, W.J. and B.C. Gladen. 1991. PCBs, DDE, and child development at 18 and 24 months. Ann
Epidemiol. 1991 Aug;l(5):407-13.
TAMS Consultants, Inc., Gradient Corporation, 1999. Phase 2 Report - Review Copy. Further Site
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TAMS Consultants, Inc., Gradient Corporation, 2000. Hudson River PCBs Reassessment RI/FS.
Responsiveness Summary for Volume 2F - Human Health Risk Assessment. Book 1 of 1 Upper Hudson
Risk Assessment. March 2000.
Tilson, H.A., J.L. Jacobsen, and W.J. Rogan. 1990. Polychlorinated biphenyls and the developing nervous
system: cross-species comparisons. Neurotoxicology and Teratology 12:239-248.
Tilson, H.A. and P.R. Kodavanti. 1998.The neurotoxicity of polychlorinated biphenyls. Neurotoxicology.
1998 Aug-Oct; 19(4-5):517-25.
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U.S. Bureau of Census. 1990. County-to-County Migration Flow Files ~ 1990 Census of Population and
Housing : In-Migration (CD90-MIG-01). Special Project 312. U.S. Department of Commerce Bureau of
the Census.
U.S. Environmental Protection Agency (USEPA). 1995. "USEPA Risk Characterization Program."
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Washington, DC.
U.S. Environmental Protection Agency (USEPA). 1997. "Policy for Use of Probabilistic Analysis in Risk
Assessment at the U.S. Environmental Protection Agency." Office of Research and Development,
Washington, DC. USEPA/630/R-97/001.
Winneke, G. et al. 1998. Developmental neurotoxicity of poly chlorinated biphenyls (PCBS): cognitive and
psychomotor functions in 7-month old children. Toxicol Lett. 1998 Dec 28;102-103:423-8.
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