v>EPA
United States
Environmental Protection
Agency
Chemical Expert Input and Review for
the Third Contaminant Candidate List
Office of Water (4607M) EPA 815-R-08-0009 February 2008 - Draft www.epa.gov/safewater
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EPA-OGWDW Chemical Expert Input and Review EPA 815-R-08-009
for CCL 3 February 2008 - DRAFT
Table of Contents
1.0 INTRODUCTION 1
2.0 BACKGROUND 1
3.0 PROJECT SUMMARY 3
4.0 CHEMICAL WORKSHOP 4
Table of Exhibits
Exhibit 1: Schematic of CCL 3 Classification Process 2
Exhibit 2: Meeting Agenda for Wednesday, March 21 - Thursday, March 22, 2007 4
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List of Acronyms and Abbreviations
< Less than or equal to
CCL Contaminant Candidate List
CCL 1 EPA's first contaminant candidate list
CCL 2 EPA's second Contaminant Candidate List
CCL 3 EPA's third Contaminant Candidate List
EPA United States Environmental Protection Agency
HRL Health reference level
LD50 Lethal dose 50; an estimate of a single dose that is expected to cause the
death of 50 percent of the exposed animals; it is derived from experimental
data.
LOAEL Lowest observed adverse effect level
NAS National Academy of Sciences
NDWAC National Drinking Water Advisory Council
NOAEL No observed adverse effect level
OGWDW Office of Ground Water and Drinking Water
RfD Reference Dose
SDWA Safe Drinking Water Act
IDS Training Data Set
US United States of America
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1.0 Introduction
As part of the process of establishing a chemical Contaminant Candidate List (CCL), the U.S.
Environmental Protection Agency (EPA) sought expert input on its approach to identifying and
prioritizing contaminants. On March 21 and 22, 2007, an expert panel convened in Washington,
D.C. at EPA Headquarters to provide input and review of the draft CCL3 chemical prioritization
process. A panel of 6 experts was selected based on their experience in the fields of public
health, toxicology, and epidemiology; and familiarity with the Safe Drinking Water Act
regulations and the CCL regulatory process. This document provides a summary of the
proceedings of the two-day workshop, organized and facilitated by Horsley & Witten, Inc. The
workshop agenda is included in section 4.0 of this report.
2.0 Background
The Safe Drinking Water Act (SDWA) includes a process that the EPA must follow to identify
new contaminants that may require regulation. According to the SDWA, EPA must periodically
release a CCL of unregulated contaminants that are known to or anticipated to occur in drinking
water at levels that may pose a risk to public health; and therefore, may require regulation. EPA
typically conducts an extensive research and data collection effort, and solicits comments from
experts and the general public (via the Federal Register), on unregulated contaminants to develop
a CCL. These contaminants are then further evaluated by EPA to determine whether they should
be regulated. When making this determination, the SDWA specifies three criteria to determine
whether a contaminant may require regulation:
• the contaminant may have an adverse effect on the health of persons;
• the contaminant is known to occur or there is a substantial likelihood that the contaminant
will occur in public water systems with a frequency and at levels of public health
concern; and
• in the sole judgment of the Administrator, regulation of such contaminant presents a
meaningful opportunity for health risk reduction for persons served by public water
systems.
The first CCL (CCL1), established in March of 1998, contained 60 contaminants (50 chemical
and 10 microbial) that were chosen based on expert opinion. EPA then made their regulatory
determinations on the CCL1 and ultimately decided not to regulate 9 contaminants, based on
their evaluation of "significant risk reduction" as described in the SDWA. The second CCL
(CCL2), established in February 2005, carried forward the remaining 51 contaminants from
CCL1 (9 microbiological contaminants and 42 chemical contaminants). During this time, EPA
provided an update on the Agency's work to improve future CCL review processes that is based,
in part, on recommendations from the National Research Council (NRC) and the National
Drinking Water Advisory Council (NOWAC).
NOW AC and the National Academies of Science (NAS) proposed a broader, more
comprehensive evaluation process than previously utilized by EPA to assist the Agency in
identifying contaminants for the CCL. They recommended that EPA develop and use a process
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EPA815-R-08-009
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for creating future CCLs. As a result, a broad universe of potential drinking water contaminants
were established, assessed, and reduced to a preliminary CCL (PCCL), using simple screening
criteria. The screening criteria indicate public health risk and the likelihood of occurrence in
drinking water. All of the contaminants on the PCCL would then be assessed in more detail
using a classification approach and tools, along with expert judgment, to evaluate the likelihood
that specific contaminants could occur in drinking water at levels and at frequencies that pose a
public health risk. The outcome of the detailed classification approach results in the draft CCL.
Exhibit 1 provides a flow chart below outlines this new process:
Exhibit 1: Schematic of CCL 3 Classification Process
STEP1
Identifying the
Universe
STEP 2
Screening
to a PCCL
STEP 3
Selecting the
CCL
[
1 Univ
1
1 PCCL L _ _ _
Evaluation ^_
Expert Review
1
Proposed CCL 1
i
i
i ,
i
Surveillance
And
Nomination
I
I
i
1
EPA developed the third CCL (CCLS) using the new procedures described above. During this
process, they identified 284 data sources for consideration in the CCLS process, including some
contaminants from the CCL2. Each universe (microbial and chemical) was narrowed down to a
PCCL using simple screening criteria, based on a contaminant's potential to occur in water
systems and to cause adverse human health effects.
EPA identified and evaluated 39 data sources with information on contaminant health effects and
occurrence. EPA identified a "CCL Universe of Chemicals" consisting of approximately 6,000
chemicals from these data sources. EPA used several data elements to represent a chemical's
potential to occur in drinking water and its potential to cause health effects on humans, including
measured concentrations in water, amount released to the environment, amount produced, and
persistence in water. The data elements also included measured toxicity values such as the
reference dose (RfD), carcinogenicity values, the lowest or no observed adverse effect levels
(LOAEL or NOAEL), lethal dose (LD50), and categorical cancer data. EPA developed criteria to
screen chemicals with health effects and occurrence data elements at levels of concern in order to
narrow the Chemical Universe to a PCCL of 532 chemicals.
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Using the NRC/NDWAC recommendations, EPA developed an approach for classifying
potential drinking water contaminants that uses decision support tools to aid in the development
of the draft CCL. EPA chose four attributes; Potency, Severity, Prevalence, and Magnitude, as
its key decision criteria in evaluating chemicals. The approach ensured that key decision criteria
were used and applied consistently among potential contaminants, when deciding whether or not
to list a contaminant on CCL. In order to evaluate, categorize, and prioritize the PCCL
contaminants in selecting the CCL, one must be able to interrelate the data that represent
measures of the attributes. This relative assessment using different data measures involved the
need to normalize the available data by developing scales for the various types of attribute data,
and scoring mechanisms (Attribute Scoring Protocols) for potential drinking water contaminants.
EPA developed, tested, and evaluated the results of several classification models to assess their
usefulness and identify which ones might provide the best decision support tools. Classification
models are often described as pattern recognition algorithms. These models develop statistical
relationships (to recognize patterns) among input variables (Attributes) of drinking water
contaminants to predict their classification (List-Not List). To evaluate the classification models,
EPA developed a data set, called the "training data set" (TDS), to train or teach the models to
mimic List-Not List decisions made by experts. The classification algorithm develops the
relationship, or rule, for the classification model based on the decisions made on the TDS. After
the attributes for the PCCL contaminants are scored, the classification model is then used to
classify PCCL contaminants into List-Not List categories and develop the draft CCL.
3.0 Project Summary
The goal of this project was to obtain expert input on the approach EPA is using to establish the
chemical CCL3. Specifically, the focus of this review was to provide comment on the draft list
of chemical contaminants, the screening process, and scoring protocols used to establish the list.
Horsley & Witten, Inc. was contracted by EPA to coordinate the expert review of the CCL3 for
chemical contaminants. A pool of potential experts recommended by their peers from national
drinking water organizations such as the American Public Health Association, Association of
State Drinking Water Administrators, National Science Foundation, and universities with strong
public health and medical programs were evaluated.
Horsely & Witten selected 6 experts to participate in the chemical review. Experts were selected
based on their experience in the fields of public health, toxicology, and epidemiology; their
familiarity with the Safe Drinking Water Act regulations and the CCL regulatory process; as well
as their level of interest. Horsely & Witten organized and facilitated a two-day chemical
workshop that was held in Washington, D.C. at EPA Headquarters (March 21- 22 2007), where
the experts served on panels to discuss their findings regarding the draft CCL3 chemical process.
The workshop agenda is included in this report under the workshop section.
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Experts received an organized packet of information prior to the workshop, which included the
workshop agenda and all CCL3 associated materials including documentation of the compilation
of the CCL Universe, screening process, scoring process, and contaminant dossiers. Experts
answered all questions posed by EPA and engaged in productive discussions regarding
contaminants and whether the draft CCL lists developed by EPA were acceptable, based on the
screening and scoring process. A detailed summary of the workshop is included in this
document.
4.0 Chemical Workshop
Exhibit 2: Meeting Agenda for Wednesday, March 21 -
Thursday, March 22, 2007
DAYl
Time
9:00 - 9:30 AM
9:30 - 10:00 AM
10:00-10:15 AM
Topic
Introductions
Welcome
Meeting Objectives, Procedures, and Logistics
Overview of the CCL 3 Approach
Speaker
Facilitator: Mark Nelson,
Horsley Witten, Inc.
Pamela Barr, Director, Standards
and Risk Management Division,
EPA Office of Ground Water
and Drinking Water (OGWDW)
Mark Nelson, Facilitator
Yvette Selby-Mohamadu, EPA
OGWDW
10:15 -10:30 AM: BREAK
10:30-11:15 AM
11:15 -12:30 AM
Overview of the CCL3 Chemical Universe to
Preliminary CCL (PCCL)
Overview of the CCL3 PCCL to the CCL
Yvette Selby-Mohamadu, EPA
OGWDW
Zeno Bain and Michael Messner,
EPA OGWDW
12:30- 1:30 PM: LUNCH
1:30-2:15 PM
2: 15- 4:45 PM
Including Break
4:45- 5:00 PM
EPA Internal Evaluation Review Process
Present and Discuss Charge Questions
Are there other factors that should be
considered, as part of post-Model processing, in
deciding on the Preliminary Draft CCL 3?
Are you in agreement with how EPA evaluated
uncertainty and types of data used for
occurrence (i.e., finished water, ambient water,
release, and production volume data) and health
effects (i.e., RfD or equivalent, cancer slope
factor, NOAEL, LOAEL, andLD50) in
constructing the Preliminary Draft CCL 3?
Wrap-Up
Joyce Donohue, OST, EPA
Experts
Mark Nelson
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DAY 2
Time
8:00-8:15 AM
8: 15 -11:30 AM
Including Break
Topic
Review of Previous Day & Agenda for Day 2
Discuss Charge Questions (continuation)
Does the Preliminary Draft CCL 3 chemical list
represent those contaminants that have the
highest potential to occur in public water
systems and cause adverse human health
effects?
Are there chemical contaminants on the
Preliminary Draft CCL 3 list that should not be
listed?
Are there chemical contaminants not on the
Preliminary Draft CCL 3 list that should be
listed?
Do you agree with EPA 's assumption that the
CCL is also a vehicle for identifying chemicals
that are regional or local problems and require
new or updated health advisories?
Speaker
EPA OGWDW
Experts
11:30- 12:30 PM: LUNCH
12:30- 4:30 PM
Including Break
4:30- 5:00 PM
Complete Discussion of Charge Questions
Wrap-Up
Experts
Facilitated by Mark Nelson
Mark Nelson
Introduction - Mark Nelson, Horsley & Witten, Facilitator
Expert Panel:
Caroline Baier-Anderson, Ph.D., University of Maryland & Environmental Defense
Shane Snyder, Ph.D., Southern Nevada Water Auth.
Ann Marie Gebhart, Ph.D., Underwriters Laboratories
John Gaston, P.E., CH2M HILL Consultants
Lloyd R Wilson, Ph.D., New York State Department of Health
Michael J Focazio, Ph.D., U.S. Geological Survey
Welcome - Pamela Barr, Director, EPA Standards and Risk Management Division
Ms. Barr discussed the background of the chemical CCL 3. The contaminants on the list are
known or anticipated to occur in drinking water and are most likely to cause public health
concerns. EPA agreed with the NAS recommendation on how the review process should be
transparent, reproducible, and comprehensive. Ms. Barr explained that the reviewers' goal for
this workshop is to review the draft list to see if they agree with EPA's conclusions regarding the
contaminants.
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Ms. Barr reminded the group that the list, and the other workbook materials they received are
internal agency deliberative documents and asked the reviewers not to cite or distribute the
information. She explained that EPA is looking for individual expertise, not information from
the viewpoint of reviewer's organizations. Ms. Barr stated that EPA planned to publish the draft
list in the Federal Register in February 2008, and the final list is expected to be completed in
August of 2009.
Overview of the CCL 3 Approach - Yvette Selby-Mohamadu, EPA Office of Ground
Water and Drinking Water
Ms. Selby-Mohamadu provided an overview of EPA's approach to the CCL 3 process. She
stated that the approach is focused on finding a balance between health effects and occurrence.
The first three steps of the process are data-driven, so there remains the possibility that
contaminants lacking toxicity and/or occurrence data may get overlooked. The surveillance and
nominations process is a significant component to the process to catch emerging contaminants
and/or contaminants that may have lacked data in the data sources used in the first three steps.
Ms. Selby-Mohamadu specified that the focus of this workshop is on the selection of a CCL 3
based on the model output.
Overview of the CCL 3 - Chemical Universe to Preliminary CCL 3 (PCCL 3) - Yvette
Selby-Mohamadu, EPA Office of Ground Water and Drinking Water
Ms. Selby-Mohamadu described EPA's process of selecting the PCCL 3 from the CCL 3
chemical universe. The first step was building a universe of data sources to be used to define the
universe of chemicals. Each data source was reviewed for the following:
• Relevance (does this data source contain demonstrated or potential health effects or
occurrence or surrogate information?);
• Completeness (does this data source have the minimum requirements - contact name,
description of the data elements, and how the data were obtained, and how the data were
obtained?);
• Redundancy (does this data source contain identical information as other more
comprehensive sources?); and
• Retrievability (is the data in this source formatted for automated retrieval?).
Once the CCL 3 chemical data source universe was built, the CCL 3 universe of chemicals was
determined, based on the quality and quantity of health effects and occurrence data within these
data sources. In total, approximately 6,000 chemicals were chosen for the chemical universe.
The chemicals within the CCL 3 universe were then categorized by toxicity and occurrence. The
health effects and occurrence categories were used to develop a screen separating chemicals that
would pass to the PCCL from those that would remain in the universe. After completion of the
data screening, approximately nine percent of the CCL universe made it into the draft PCCL.
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Overview of the CCL 3 - PCCL 3 to CCL 3 - Zeno Bain and Michael Messner, EPA Office
of Ground Water and Drinking Water, Joyce Donahue, EPA Office of Science and
Technology
Mr. Bain and Dr. Messner presented EPA's process of selecting a draft CCL 3 from the PCCL.
Each of the contaminants within the PCCL was analyzed based on four attributes: Prevalence,
Magnitude, Potency and Severity. Prevalence and Magnitude are measures of Occurrence, and
Potency and Severity are both measures of Health Effects. When a measure of magnitude (e.g.,
concentration, pounds released) was not available, Persistence-Mobility was used as a surrogate.
Once the attributes were assigned, a TDS of contaminants was selected to train or teach
classification models to mimic expert list/no list decisions. The TDS has two components for
each chemical: Contaminant Attribute Scores and a List/No List Decision (formed through
consensus). The models that performed well with the TDS were ANN, Linear, and QUEST.
These three models were used to evaluate the remainder of the PCCL contaminants, and their
predictions were averaged to provide a final decision and ranking for each contaminant. Dr.
Joyce Donahue described how the model results were then evaluated by a team of evaluators
composed of individuals from multiple EPA offices and multiple disciplines. Each PCCL
contaminant was assigned a numeric score of confidence, which was taken into account when
selecting the draft CCL 3. Also, supplemental data relevant to drinking water was obtained and
utilized as part of the post-model process. The draft CCL 3 included the following:
• Contaminants with a Health Reference Level (HRL)/Concentration ratio of < 10 from
contaminants with finished, ambient or modeled water data;
• Contaminants with List (L) or L? model outcomes, release data, and medium certainty;
• Nominated contaminants that meet the listing criteria after evaluation of submitted data;
and
• Contaminants with L or L? Model projections and low certainty were not selected for
the draft CCL, but are recognized as possible candidates for research.
In total, 95 chemicals were chosen for the draft CCL 3.
Discussion of Questions:
Question #1: Are there other factors that should be considered, as part of post-model
processing, in deciding on the Preliminary Draft CCL 3?
Experts Summary Answer to Question #1:
The panel agreed that the professional judgment of the EPA team developing the CCL should be
an additional tool used to analyze and process the results from the screening models. However,
it is important to keep in mind that professional judgment must be defendable and transparent. A
number of examples of professional judgment were discussed and the panel recommended that
EPA consider them in finalizing the CCL. They were:
• A recognition that the production volumes of some chemicals may increase in the future
and any information on potential production increases should be used to determine if a
future production value would alter the listing determination for a particular compound;
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• A recognition that changing technologies or processes may need to be considered in the
final review of a compound. An example given was the potential for future disinfection
processes that may create new compounds and/or increase the concentrations of known
byproducts;
• A recommendation that blood and body burden data should be considered in the final
evaluation of a compound, such as the blood testing data showing 100% occurrence in
samples for Perfluorooctanesulfonic acid (PFOS); In addition, the body burden data
should be considered earlier in the process (similar to release data) for the next round.
• Toxic Release Inventory release data, as well as the physical properties of each chemical,
especially gases, should be analyzed to determine if model results would change if
surface water release information was used instead of total release data;
• The reference doses based on use of an oral response dose calculated from inhalation data
without appropriate physiologically based kinetic modeling should be used with caution.
It was recommended that the uncertainty tags for this information could be increased,
and;
• Finished and ambient water quality data should be sorted into ground water and surface
water categories and these separate groups should be analyzed to determine if this sorting
significantly impacts the final list results. If so, this sorting process should be considered
in updating the modeling protocols in developing CCL 4.
Question #2: Are you in agreement with how EPA evaluated uncertainty and types of data
used for occurrence (i.e., finished water, ambient water, release, and production volume
data) and health effects (i.e., RfD or equivalent, cancer slope factor, NOAEL, and LDso) in
constructing preliminary Draft CCL 3?
Experts Summary Answer to Question #2:
The panel was comfortable with the overall approach to calculating and applying the uncertainty
tags as part of the post-model processing. Two issues were identified during the discussion of
the uncertainty process:
• There was a recommendation to more clearly explain the rationale for selecting
nominated chemicals so their inclusion on the CCL could be better understood, and;
The panel expressed caution on the use of the release data results, especially for compounds
where there is no data on their actual presence in drinking water or ambient water. It was
suggested that a paragraph be included in the final CCL to express this sense of caution and
describe how release data were analyzed. Also, occurrence data (e.g., the Information Collection
Rule (61 FR 24354) should be looked at more closely to identify whether chemicals could be
moved out of the release category.
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Question #3: Does the Preliminary Draft CCL 3 chemical list represent those
contaminants that have the highest potential to occur in public water systems and cause
adverse human health effects?
Experts Summary Answer to Question #3:
Given the limitations in existing databases and interpretations, the panel agreed that the
Preliminary Draft CCL 3 chemical list represents those unregulated contaminants that have the
highest potential to occur in public water systems and to have adverse health effects. This
opinion of the panel was based on the information provided to them by EPA and is a result of
their review of the CCL development process as explained by EPA staff during the two-day
workshop. The panel also agreed that EPA efforts to update data and research will be critical to
the success of future CCLs.
The panel all recognized the level of effort and detail that went into the development of the
modeling process used to create the draft list and complimented EPA on their efforts in putting it
together.
Question #4: Are there chemical contaminants on the Preliminary Draft CCL 3 list that
should not be listed?
Experts Summary Answer to Question #4:
The panel then reviewed the full CCL based on the four uncertainty groups used by EPA to
develop the final list. These are:
• 33 chemicals in the high certainty bin, those with finished water data and an
HRL/concentration ratio of < 10;
• 25 pesticide chemicals in the medium certainty bin, those with modeled surface and/or
ground water data that yielded a HRL/concentration ratio of < 10;
• 28 chemicals in the medium certainty bin, those with release data that gave modeled L or
L? rankings; and
• 7 chemicals in the low certainty bin that were nominated with supplied new information.
The panel agreed with the selection of the 33 high certainty compounds and the 25 medium
certainty pesticide compounds. There was greater discussion and review of the 28 compounds
included based on release data, and the 7 nominated compounds. A concern was expressed that
chemicals selected based only on release data are included even though there is no information
as to whether or not they are present in drinking water. It was recommended that the final CCL
include information highlighting these chemicals and state that there is no data available to
determine if they are present in drinking water. Further it was recommended that chemicals in
the list should also be tagged to represent those needing health effects data or research on
analytical methods.
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No chemicals were recommended for removal from the list. The panel did recommend that the
data for the compound HFCC-22 be evaluated to see if using data on release to surface water
versus total release data would change its ranking and, therefore, inclusion on the list. This was
recommended because the compound is a gas, and looking at the release to surface water data
may indicate there is less likelihood it would occur in water.
Question #5: Are there chemical contaminants not on the Preliminary Draft CCL 3 list
that should be listed?
Experts Summary Answer to Question #5:
The panel requested that EPA further review the decision to not list PFOS, as this compound has
been found in 100 % of tested blood samples and may be considered to have a higher occurrence
and toxicity then PFOA, which is listed.
Haloacetic acids 6-9 were identified by the panel as a group of chemicals that did not make it
onto the CCL list, and potentially should be added. EPA responded that these chemicals recently
came through the nomination process and that their data are being evaluated now.
Question #6: Do you agree with EPA's assumption that the CCL is also a vehicle for
identifying chemicals that are regional or local problems and require new or updated
health advisories?
Experts Summary Answer to Question #6:
The review panel agreed that the CCL was a useful tool for identifying chemicals that may
require a health advisory to support management of local or regional problems. They also
thought that the screening process used to develop the CCL from the PCCL may be used, along
with other information, to determine if a health advisory is needed for a chemical that did not get
selected for the CCL.
Other Comments:
• The panel recommended that EPA consider a strong outreach process as the final CCL is
published to highlight the significant modeling and decision making processes used in its
development. As part of the outreach effort, the panel suggested that EPA create an
interactive web-based chemical database for public use.
• The panel suggested that the relationships between the CCL and the Unregulated
Contaminant Monitoring Regulation lists be explained in the draft documents to clarify
confusion in how the lists are developed and used.
• The panel recommended that current data gaps (i.e., chemicals that were made a lower
priority based on lack of occurrence or toxicity data) be publicized as research needs.
However, if the CCL was made transparent enough so that the public could easily
identify these research needs, a formal need to publish data gaps may not be required.
Although this was not the charge for this expert panel, there was interest in determining
how to fill the data gaps and what generates momentum to fill them.
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• For the workshop itself, and for future outreach efforts, it would be helpful to have an
introductory chart that went through all the steps from the universe to the CCL, and how
chemicals were weeded out, in order to understand the process better.
4.1 Materials Provided
In addition to the chemicals listed on the Preliminary Draft CCL 3, EPA provided drafts of the
support documents developed for the Draft CCL 3. Comments provided by reviewers have been
incorporated in to the documents that are now included in the docket. The following documents
and their appendixes were included in the Expert Review Workshop notebooks provided to each
reviewer:
• Assessment of Data Sources
• Nominations for the CCL 3
• Screening the CCL 3 Chemical Universe
• Classification Process to Select the Chemical CCL 3
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