[Federal Register: April 2, 2004 (Volume 69, Number 64)]
[Notices]
[Page 17406-17415]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr02ap04-53]
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ENVIRONMENTAL PROTECTION AGENCY
[FRL-7641-5]
Drinking Water Contaminant Candidate List 2; Notice
AGENCY: Environmental Protection Agency.
ACTION: Notice.
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SUMMARY: The Safe Drinking Water Act (SDWA), as amended in 1996,
requires the Environmental Protection Agency (EPA) to publish a list of
contaminants which, at the time of publication, are not subject to any
proposed or promulgated national primary drinking water regulations,
that are known or anticipated to occur in public water systems, and
which may require regulations under SDWA (section 1412(b)(1)). SDWA, as
amended, specifies that EPA must publish the first list of drinking
water contaminants no later than 18 months after the date of enactment,
i.e., by February 1998 (henceforth referred to as the 1998 Contaminant
Candidate List or the 1998 CCL), and every five years thereafter.
Today's notice announces EPA's preliminary decision to carry over the
remaining 51 contaminants on the 1998 CCL as the draft CCL 2, provides
information on EPA's efforts to expand and strengthen the underlying
CCL listing process to be used for future CCL listings, and requests
comment on CCL-related activities to improve the drinking water
contaminant listing process. Today's draft CCL includes 42 chemicals or
chemical groups and nine microbiological contaminants. The
[[Page 17407]]
Agency's approach to the draft CCL 2 is to continue using the remaining
contaminants on the 1998 CCL for prioritizing research and making
regulatory determinations while working with the National Drinking
Water Advisory Council (NDWAC) and stakeholders to complete a review of
the National Research Council (NRC) recommendations for developing a
more comprehensive and transparent CCL listing process. The EPA seeks
comment on the range of CCL issues and activities addressed in this
notice.
DATES: The Agency requests comment on today's notice. Comments must be
received or postmarked by midnight June 1, 2004.
ADDRESSES: Comments may be submitted electronically, by mail, or
through hand delivery/courier. Follow the detailed instructions as
provided in section I.C of the Supplementary Information section. The
official public docket for this action is located at EPA West Building,
Room B102, 1301 Constitution Avenue, NW., Washington, DC.
FOR FURTHER INFORMATION CONTACT: For questions about this notice
contact Dan Olson at (202) 564-5239 or e-mail olson.daniel@epa.gov. For
general information contact the EPA Safe Drinking Water Hotline at
(800) 426-4791 or e-mail: hotline-sdwa@epa.gov. The Safe Drinking Water
Hotline is open Monday through Friday, excluding legal holidays, from 9
a.m. to 5:30 p.m.
SUPPLEMENTARY INFORMATION:
I. General Information
A. Does This Notice Impose Any Requirements on My Public Water System?
Neither this draft CCL 2 nor the final CCL 2, when published,
imposes any requirements on anyone. Instead, it notifies interested
parties of the availability of EPA's Draft CCL 2 and seeks comment on
this draft list as well as EPA's efforts to improve the contaminant
selection process for future CCLs. Contaminants on the list may become
the subject of future regulations. At that time, the public would be
provided additional opportunities to comment as part of the rule making
process.
B. How Can I Get Copies of Related Information?
1. Docket. EPA has established an official public docket for this
action under Docket ID No. OW-2003-0028. The official public docket is
a collection of materials that is available for public viewing at the
Water Docket in the EPA Docket Center, (EPA/DC) EPA West, Room B102,
1301 Constitution Avenue, NW., Washington, DC. The EPA Docket Center
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Public
Reading Room is (202) 566-1744, and the telephone number for the Water
Docket is (202) 566-2426. For access to docket material, please call
(202) 566-2426 to schedule an appointment.
2. Electronic access. You may access this Federal Register document
electronically through the EPA Internet under the Federal Register
listings at http://www.epa.gov/fedrgstr/.
An electronic version of the public docket is available through
EPA's electronic public docket and comment system, EPA Dockets. You may
use EPA Dockets at http://www.epa.gov/edocket/ to submit or view public
comments, access the index listing of the contents of the official
public docket, and to access those documents in the public docket that
are available electronically. Once in the system, select ``search,''
then key in the appropriate docket identification number.
Certain types of information will not be placed in the EPA Dockets.
Information claimed as confidential business information (CBI) and
other information whose disclosure is restricted by statute, which is
not included in the official public docket, will not be available for
public viewing in EPA's electronic public docket. EPA's policy is that
copyrighted material will not be placed in EPA's electronic public
docket but will be available only in printed, paper form in the
official public docket. Although not all docket materials may be
available electronically, you may still access any of the publicly
available docket materials through the docket facility identified in
section I.B.1.
For public commenters, it is important to note that EPA's policy is
that public comments, whether submitted electronically or in paper,
will be made available for public viewing in EPA's electronic public
docket as EPA receives them and without change, unless the comment
contains copyrighted material, CBI, or other information whose
disclosure is restricted by statute. When EPA identifies a comment
containing copyrighted material, EPA will provide a reference to that
material in the version of the comment that is placed in EPA's
electronic public docket. The entire printed comment, including the
copyrighted material, will be available in the public docket.
Public comments submitted on computer disks that are mailed or
delivered to the docket will be transferred to EPA's electronic public
docket. Public comments that are mailed or delivered to the Docket will
be scanned and placed in EPA's electronic public docket. Where
practical, physical objects will be photographed, and the photograph
will be placed in EPA's electronic public docket along with a brief
description written by the docket staff.
C. How and To Whom Do I Submit Comments?
You may submit comments electronically, by mail, or through hand
delivery/courier. To ensure proper receipt by EPA, identify the
appropriate docket identification number in the subject line on the
first page of your comment. Please ensure that your comments are
submitted within the specified comment period. Comments received after
the close of the comment period will be marked ``late.'' The EPA is not
required to consider these late comments.
1. Electronically. If you submit an electronic comment as
prescribed below, EPA recommends that you include your name, mailing
address, and an e-mail address or other contact information in the body
of your comment. Also include this contact information on the outside
of any disk or CD ROM you submit, and in any cover letter accompanying
the disk or CD ROM. This ensures that you can be identified as the
submitter of the comment and allows EPA to contact you in case EPA
cannot read your comment due to technical difficulties or needs further
information on the substance of your comment. EPA's policy is that EPA
will not edit your comment, and any identifying or contact information
provided in the body of a comment will be included as part of the
comment that is placed in the official public docket, and made
available in EPA's electronic public docket. If EPA cannot read your
comment due to technical difficulties and cannot contact you for
clarification, EPA may not be able to consider your comment.
a. EPA Dockets. Your use of EPA's electronic public docket to
submit comments to EPA electronically is EPA's preferred method for
receiving comments. Go directly to EPA Dockets at http://www.epa.gov/edocket
, and follow the online instructions for submitting comments.
Once in the system, select ``search,'' and then key in Docket ID No.
OW-2003-0028. The system is an ``anonymous access'' system, which means
EPA will not know your identity, e-mail address, or
[[Page 17408]]
other contact information unless you provide it in the body of your
comment.
b. E-mail. Comments may be sent by electronic mail (e-mail) to
OW-Docket@epa.gov, Attention Docket ID No. OW-2003-0028. In contrast to
EPA's electronic public docket, EPA's e-mail system is not an
``anonymous access'' system. If you send an e-mail comment directly to
the Docket without going through EPA's electronic public docket, EPA's
e-mail system automatically captures your e-mail address. E-mail
addresses that are automatically captured by EPA's e-mail system are
included as part of the comment that is placed in the official public
docket, and made available in EPA's electronic public docket.
c. Disk or CD ROM. You may submit comments on a disk or CD ROM that
you mail to the mailing address identified in section I.C.2. These
electronic submissions will be accepted in WordPerfect or ASCII file
format. Avoid the use of special characters and any form of encryption.
2. By mail. Send an original and three copies of your comments to:
Water Docket, Environmental Protection Agency, Mail Code: 4101T, 1200
Pennsylvania Ave., NW., Washington DC, 20460, Attention Docket ID
number OW-2003-0028.
3. By hand delivery or courier. Deliver your comments to: Water
Docket, Environmental Protection Agency, EPA West Building, Room B102,
1301 Constitution Avenue, NW., Washington, DC, Attention Docket ID
number OW-2003-0028. Such deliveries are only accepted during the
Docket's normal hours of operation as identified in section I.B.1.
D. What Should I Consider as I Prepare My Comments for EPA?
You may find the following suggestions helpful for preparing your
comments:
1. Explain your views as clearly as possible.
2. Describe any assumptions that you used.
3. Provide any technical information and/or data you used that
support your views.
4. If you estimate potential burden or costs, explain how you
arrived at your estimate.
5. Provide specific examples to illustrate your concerns.
6. Offer alternatives.
7. Make sure to submit your comments by the comment period deadline
identified.
8. To ensure proper receipt by EPA, identify the appropriate docket
identification number in the subject line on the first page of your
response. It would also be helpful if you provided the name, date, and
Federal Register citation related to your comments.
II. Background and Summary of Today's Notice
This section summarizes the purpose of today's notice and provides
a brief background on the CCL requirements and prior activities related
to the CCL.
A. What Is the Purpose of Today's Action?
The drinking water CCL is the primary source of priority
contaminants for evaluation by EPA's drinking water program.
Contaminants on the CCL are currently not subject to any proposed or
promulgated national primary drinking water regulation, but are known
or anticipated to occur in public water systems, and may require
regulation under SDWA. The EPA conducts research on health, analytical
methods, treatment technologies and effectiveness, and contaminant
occurrence for priority drinking water contaminants on the CCL. The
Agency also develops drinking water guidance and health advisories, and
makes regulatory determinations for priority contaminants on the CCL.
Today's Federal Register notice explains why EPA is carrying over
the remaining 51 contaminants on the 1998 CCL as the draft CCL 2 and
provides background information on the list. Additionally, this notice
describes efforts to improve on the CCL selection process, the NRC
recommendations to EPA on developing future CCLs, and related issues
being evaluated by EPA and NDWAC to implement the NRC recommendations.
(The NDWAC provides independent advice, consultations, and
recommendations to EPA on matters related to the activities, function,
and policies of the Agency under the SDWA, as amended. See section V
for further discussion on NDWAC.) The EPA requests comment on the draft
CCL 2 and on the process for developing future CCLs.
B. The Background of the CCL
The SDWA is the core statute addressing drinking water at the
Federal level. Under SDWA, EPA sets public health goals and enforceable
standards for drinking water quality. In 1996, Congress amended SDWA to
emphasize sound science and risk-based priority-setting. Congress also
changed the way drinking water regulatory priorities are set by
establishing the CCL requirements. The 1996 SDWA amendments require EPA
to (1) publish every five years a list of currently unregulated
contaminants in drinking water that may pose risks, and (2) make
determinations on whether or not to regulate at least five contaminants
on a five year cycle, or three and a half years after each CCL (SDWA
section 1412(b)(1)).
Following the 1996 SDWA Amendments, EPA sought NDWAC's
recommendations on the process that should be used to identify
contaminants for inclusion on the CCL. For chemical contaminants, the
Agency developed screening and evaluation criteria based on
recommendations from NDWAC and identified 262 potential chemical
contaminants. For microbiological contaminants, NDWAC recommended that
the Agency seek external expertise to identify and select potential
waterborne pathogens. As a result, the Agency convened a workshop of
microbiologists and public health experts, developed screening and
evaluation criteria based on workshop recommendations, and evaluated an
initial list of 25 potential microbiological contaminants.
The 1998 CCL process benefitted from considerable input from the
scientific community and the public through stakeholder meetings and
the public comments received on the draft CCL published in 1997. The
EPA published the final CCL containing 50 chemical and 10
microbiological contaminants in March of 1998 (63 FR 10273). A detailed
discussion of how EPA developed the 1998 CCL is presented in section
III of this notice.
After publication of the final 1998 CCL, EPA began collecting
occurrence data and conducting research on the CCL contaminants. Data
collection efforts include assessing the occurrence of contaminants in
public water systems through the Unregulated Contaminant Monitoring
Regulation (64 FR 50556), as well as evaluating occurrence data from
national surveys and considering State-level contaminant occurrence
information. Research efforts focused on obtaining the information
needed to characterize the adverse health effects of contaminants,
drinking water treatment options, and the development of analytical
methods to detect contaminants in drinking water.
As noted above, the 1996 SDWA also directs EPA to select at least
five contaminants from the CCL every five years to determine if
regulating the contaminants with a national primary drinking water
regulation would present a meaningful opportunity for health risk
reduction (SDWA section 1412 (b)(1)). In order to make regulatory
determinations on contaminants, EPA must have sufficient data to
evaluate
[[Page 17409]]
when and where contaminants occur, human exposure, and the risk to
public health.
On July 18, 2003, EPA announced its final determinations for a
subset of contaminants on the 1998 CCL (68 FR 42898), which concluded
that sufficient data and information were available to make the
determination that a regulation was not appropriate for the following
nine contaminants: Acanthamoeba, aldrin, dieldrin, hexachlorobutadiene,
manganese, metribuzin, naphthalene, sodium, and sulfate.
III. Developing Today's Draft Drinking Water Contaminant Candidate List
This section provides the approach EPA used to develop the draft
CCL 2, explains the rationale to support the approach, and presents the
draft CCL 2.
A. Approach and Rationale for the Draft CCL 2
The EPA's approach for the draft CCL 2 is to continue to use
contaminants identified on the 1998 CCL to set drinking water research
priorities and make regulatory determinations. The EPA believes that it
is appropriate for the draft CCL 2 to be based on the 1998 CCL because
(1) in developing the 1998 CCL, the Agency used peer-reviewed data and
information to evaluate contaminants; (2) EPA relied on significant
input from experts and stakeholders to develop a high quality process
for selecting the contaminants on the CCL; (3) the Agency has invested
in research and data collection activities related to the CCL, and is
preparing to make regulatory determinations in the 2006 time-frame
using the data collected from these activities; and (4) continued
reliance on high priority contaminants remaining from the 1998 CCL
allows the Agency to focus resources on completing ongoing work on an
expanded process for classifying drinking water contaminants based on
recent recommendations of the National Research Council (NRC, 2001). A
more detailed discussion of this approach follows.
1. Organizing and Extracting Data
a. Evaluating available chemical contaminant listings. The EPA
reviewed contaminants from seven well-known lists, as well as
contaminants recommended by stakeholders, to develop the 1998 CCL
(Table III-1). These lists contained chemicals that could be of
potential concern in drinking water. In addition, EPA evaluated a
number of other contaminants identified by stakeholders during the
December 2-3, 1996, stakeholder meeting for potential inclusion on the
CCL. In the process of creating the final list, EPA removed from
consideration 23 contaminants suspected of being endocrine disruptors
and 35 pesticides, because both groups of chemicals were the focus of
additional data collection efforts under other programs in the Agency.
The EPA intends to consider both groups of chemicals as part of the
next CCL screening and evaluation process.
Table III.--I Initial Chemical Lists Considered for Development of the
1998 CCL
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List Description
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1991 Drinking water priority list 56 contaminants.
(DWPL, EPA, 1991).
Health advisories (HAs)................ 108 contaminants, (included all
contaminants with HAs or HAs
under development).
EPA's Integrated Risk Information 48 contaminants, based on a
System database. risk-based screen developed by
EPA for the 1994 DWPL.
Contaminants identified by public water 22 ``non-target'' contaminants
systems. identified by public water
systems for the 1994 DWPL.
Agency for Toxic Substances and Disease Top 50 contaminants from the
Registry's list of contaminants found 1995 list of 275 prioritized
at Comprehensive Environmental hazardous substances.
Response, Compensation and Liability
Act sites.
Stakeholder summary list............... 59 contaminants proposed as
candidates by participants in
a December 2-3, 1997
stakeholder meeting.
Toxic Release Inventory (TRI) list..... 51 contaminants that met the
criteria for assessing the
potential to occur in public
water; derived from an
original 1994 TRI list of 343
chemicals.
------------------------------------------------------------------------
b. Screening chemical contaminants. In 1997, EPA developed
screening criteria to evaluate the potential occurrence and health
effects of chemical contaminants gathered from the lists based on the
recommendation of experts in the drinking water field, including NDWAC.
These screening criteria focused on the following two questions:
1. Is a given contaminant found in water at levels of health
concern?
2. If no data exists on contaminant occurrence, is the contaminant
likely to be found in water based on surrogates for occurrence?
An affirmative answer to either question moved the contaminant to
the health effects phase of the evaluation. Contaminants met the
criteria if the available data indicated occurrence in a drinking water
system serving a population of 100,000 or more, occurrence in two or
more States, or occurrence in 10 or more small public water systems at
levels that would trigger concern for human health. If a contaminant
did not have specific occurrence data, EPA assessed the potential for a
contaminant to occur in drinking water based on surrogates for
occurrence. Surrogates for occurrence included: TRI release estimates,
production amounts from industry data, and physical-chemical
properties. A contaminant was considered to have the potential to occur
if, using the TRI, the release to surface water was in excess of
400,000 pounds per year and the physical-chemical properties indicated
persistence and mobility of the contaminant. A contaminant was also
considered to have the potential to occur if the production volume
exceeded 10 billion pounds per year, and physical-chemical properties
indicated persistence and mobility of the contaminant.
If a pollutant met the occurrence screening criteria, EPA then
screened it for potential health effects. The health effects phase of
the evaluation had one major criterion: Was there evidence, or was
there suggestion, that the contaminant causes adverse human health
effects? This criterion was met if a contaminant had one or more of the
following elements: (1) Listed by California Proposition 65, (2)
addressed by an EPA Health Advisory, (3)
[[Page 17410]]
considered a likely (based on animal data) or known (based on human
data) carcinogen by EPA or the International Agency for Research on
Cancer, (4) evaluated by more than one human epidemiological study
(indicating adverse effects), (5) received an oral value in EPA's
Integrated Risk Information System, (6) regulated in drinking water by
another industrial country, (7) identified as a member of a chemical
family of known toxicity, or (8) characterized by a structural activity
relationship indicating toxicity. If a contaminant had none of these
elements, then EPA did not include it in the 1998 CCL.
A contaminant that met both the occurrence screening criteria and
received an affirmative response to any of the above health effects
screening elements resulted in that contaminant's inclusion into the
draft 1998 CCL.
c. Selecting microbiological contaminants. In May of 1997, at the
recommendation of NDWAC, EPA convened a workshop on microbiology and
public health to develop a list of pathogens for possible inclusion in
the 1998 CCL (62 FR 52193). Participants included experts from
academia, the drinking water industry, EPA, and other Federal agencies.
The EPA prepared and distributed a list of 25 microorganisms (6
protozoa, 8 viruses, 7 bacteria, and 4 algal toxins) for initial
consideration by workshop members. Microorganisms were included on this
initial list if they were identified in disease outbreak data, if
published literature documented the occurrence of known or suspected
pathogens in water, or if other information suggested the possibility
of a public health risk. The workshop participants established
screening criteria for deciding whether an organism should appear on
the CCL. These criteria were (1) public health significance, (2) known
waterborne transmission, (3) occurrence in source water, (4)
effectiveness of current water treatment, and (5) adequacy of
analytical methods.
All of the microorganisms included on the initial EPA list, as well
as other organisms that arose during the discussions, were evaluated
against these criteria. The results of the deliberations of the
microbiology workshop were adopted by NDWAC and subsequently utilized
by the Agency to select 13 microbiological contaminants placed on the
draft 1998 CCL.
2. Input From Stakeholders, Experts, and the Public
The EPA relied on significant input from experts and stakeholders
to develop a high quality process for selecting the contaminants on the
1998 CCL. The Agency sought stakeholder input from a number of sources
and at several different junctures in the CCL development process.
First, EPA convened a day-long meeting of over 50 experts, including
representatives from industry, academia, consultants, and other
government agencies to review a draft of the strategy for developing
the CCL. The EPA also convened NDWAC to review the strategy and make
recommendations on the development of the CCL. Experts on the NDWAC met
numerous times to discuss the CCL process and data on potential
contaminants.
As mentioned in the prior section, EPA also relied on the advice of
nationally recognized experts in the field of microbiology, during a
separate meeting, to classify microbiological contaminants. These
experts identified and selected the microbiological contaminants for
initial consideration.
Additionally, EPA consulted with the Agency's Science Advisory
Board which is a public advisory group that provides extramural
scientific information and advice to EPA.
The draft CCL containing 58 chemical and 13 microbiological
contaminants was published on October 6, 1997 (62 FR 52193). The EPA
requested comment on the approach used to develop the CCL, and on
whether specific contaminants should be on the list. The EPA received
71 comments from many segments of the drinking water community
including trade associations, environmental groups, industries,
chemical manufacturers, State and local health regulatory agencies,
water utilities, and private citizens. Commenters provided data and
information on specific contaminants and included suggestions on the
process for future CCL development. Based on these comments, EPA
removed 10 chemical and 4 microbiological contaminants, and added 2
chemical and 1 microbiological contaminant to the final list. The final
1998 CCL contained 50 chemical and 10 microbiological contaminants and
was published on March 2, 1998 (63 FR 10273).
3. Research and Data Collection for Contaminants on the 1998 CCL
The EPA has made data collection and research on the CCL
contaminants a priority and continues to collect information and
conduct research in the areas of health effects, analytical methods,
treatment, and occurrence. As noted previously, the Agency is preparing
to make regulatory determinations in the 2006 time-frame using the data
collected from these activities.
a. Research on health effects, treatment, and analytical methods.
The Drinking Water Research Program's Multi-Year Plan identifies over
50 projects for contaminants on the CCL. These projects are scheduled
for completion in the next two years and span three research areas:
health effects, treatment, and analytical methods. The results of these
activities will provide the information needed to characterize
potential health impacts, assess the ability to detect selected
contaminants in drinking water, and verify treatment capability and
cost.
b. Data collection on occurrence. To assess whether the CCL
contaminants are occurring in drinking water systems, EPA identified
occurrence priorities and determined whether analytical methods were
available to monitor for priority CCL contaminants. Because SDWA
requires EPA to limit monitoring requirements to 30 contaminants in any
5-year cycle, only a subset of the CCL contaminants were monitored in
the first round of data collection. Data will be available for use from
the first five-year cycle of monitoring in mid-2004. The second cycle
of data collection is expected to begin in 2006 and will be completed
in mid-2010, after EPA proposes and promulgates a new list of
contaminants for monitoring. Research is also underway to develop
methods for contaminants currently without adequate analytical methods,
or where the current analytical method detection limit was above the
known adverse health effect level of concentration. Completion of these
methods will allow EPA to make regulatory determinations in the future.
Because data from ongoing research and data collection activities
will become available in the next few years, EPA believes that it is
appropriate to maintain current focus on gathering this information in
preparation for making regulatory determinations in 2006.
4. Development of an Improved Classification Process for Future CCLs
Continued focus on many of the priority contaminants from the 1998
CCL allows the Agency to target resources to complete its ongoing work
on an expanded process for classifying drinking water contaminants, so
that contaminants identified in many more sources can be effectively
screened.
After the 1998 CCL was published, the Agency asked the National
Research Council, the operating arm of the National Academy of
Sciences, to review the 1998 CCL selection process and provide
recommendations on how
[[Page 17411]]
the process could be improved. These recommendations were developed
over several years and provided to the Agency in late 2001 (see section
IV). On balance, the NRC found the 1998 CCL to be an important first
step and noteworthy effort to identify and select unregulated chemical
and microbiological drinking water contaminants. As with any new
initiative, the NRC identified a number of opportunities to strengthen
and expand the analytical process upon which the 1998 CCL was based.
The NRC recommendations focused on developing a larger initial list
(universe) and on identifying new approaches for screening larger
numbers of potential CCL contaminants. While the NRC recommendations
greatly expand the universe of contaminants and suggest a change in the
manner in which contaminants are selected for the CCL, they are based
on the same fundamental principles used in developing the 1998 CCL--a
focus on health impacts and occurrence. The NRC approach addresses the
expansion of the universe of contaminants and recommends a process that
combines expert judgement with the use of computerized data sources and
classification processes to screen contaminants (see section IV.C for
more information). The use of automated classification processes would
allow EPA to evaluate many more contaminants than experts alone can
evaluate in the absence of these processes. The much broader and more
complex approach recommended by the NRC may enable EPA to gather
information from sources that were not used to develop the 1998 CCL,
and thus strengthen the Agency's ability to identify emerging
contaminants.
The EPA agrees that an approach that combines expert judgement with
automated classification processes should be explored. The Agency is
continuing to assess and refine the approach recommended by the NRC.
The Agency believes that the CCL proposed today is sound, and should
continue to be the source of contaminants for making additional
regulatory determinations in the near term. This, however, should not
be interpreted to mean that EPA is restricted to the contaminants on
this CCL for making regulatory determinations. The EPA may add
contaminants to this list and make regulatory determinations for any
unregulated contaminant not on today's CCL, as necessary, to address an
urgent threat to public health.
B. The Draft CCL 2
Table III-2 lists the contaminants on the draft CCL 2. These
contaminants are identified by name and, where available, the Chemical
Abstracts Service Registry Number (CASRN). The draft CCL 2 consists of
nine microbiological contaminants and 42 chemical contaminants or
contaminant groups.
Table III-2.--Draft Drinking Water CCL 2
------------------------------------------------------------------------
Microbiological contaminant candidates
-------------------------------------------------------------------------
Adenoviruses
Aeromonas hydrophila
Caliciviruses
Coxsackieviruses
Cyanobacteria (blue-green algae), other freshwater algae, and their
toxins
Echoviruses
Helicobacter pylori
Microsporidia (Enterocytozoon and Septata)
Mycobacterium avium intracellulare (MAC)
------------------------------------------------------------------------
Chemical contaminant candidates CASRN
------------------------------------------------------------------------
1,1,2,2-tetrachloroethane.................................. 79-34-5
1,2,4-trimethylbenzene..................................... 95-63-6
1,1-dichloroethane......................................... 75-34-3
1,1-dichloropropene........................................ 563-58-6
1,2-diphenylhydrazine...................................... 122-66-7
1,3-dichloropropane........................................ 142-28-9
1,3-dichloropropene........................................ 542-75-6
2,4,6-trichlorophenol...................................... 88-06-2
2,2-dichloropropane........................................ 594-20-7
2,4-dichlorophenol......................................... 120-83-2
2,4-dinitrophenol.......................................... 51-28-5
2,4-dinitrotoluene......................................... 121-14-2
2,6-dinitrotoluene......................................... 606-20-2
2-methyl-Phenol (o-cresol)................................. 95-48-7
Acetochlor................................................. 34256-82-1
Alachlor ESA & other acetanilide pesticide degradation N/A
products..................................................
Aluminum................................................... 7429-90-5
Boron...................................................... 7440-42-8
Bromobenzene............................................... 108-86-1
DCPA mono-acid degradate................................... 887-54-7
DCPA di-acid degradate..................................... 2136-79-0
DDE........................................................ 72-55-9
Diazinon................................................... 333-41-5
Disulfoton................................................. 298-04-4
Diuron..................................................... 330-54-1
EPTC (s-ethyl-dipropylthiocarbamate)....................... 759-94-4
Fonofos.................................................... 944-22-9
p-Isopropyltoluene (p-cymene).............................. 99-87-6
Linuron.................................................... 330-55-2
Methyl bromide............................................. 74-83-9
Methyl-t-butyl ether (MTBE)................................ 1634-04-4
Metolachlor................................................ 51218-45-2
Molinate................................................... 2212-67-1
Nitrobenzene............................................... 98-95-3
Organotins................................................. N/A
Perchlorate................................................ 14797-73-0
Prometon................................................... 1610-18-0
RDX........................................................ 121-82-4
Terbacil................................................... 5902-51-2
Terbufos................................................... 13071-79-9
Triazines and degradation products of triazines \1\........
Vanadium................................................... 7440-62-2
------------------------------------------------------------------------
\1\ Including, but not limited to Cyanazine 21725-46-2 and atrazine-
desethyl 6190-65-4.
IV. The National Research Council's Recommended Approach for Developing
Future CCLs
This section summarizes the NRC recommendations to EPA for
developing future CCLs and discusses other issues related to
contaminant selection and prioritization.
The EPA sought the advice of the NRC in response to comments
received during the development of the 1998 CCL, which indicated a need
for a broader, more systematic approach for selecting contaminants.
The Agency asked the NRC to address three key topics related to
drinking water contaminant selection and prioritization:
1. What approach should be used to develop future CCLs?
2. How best should EPA assess emerging drinking water contaminants
and related databases to support future CCL efforts?
3. What approach should EPA use to set priorities for contaminants
on the CCL?
The NRC's findings and recommendations on these topics were
published in the following three NRC reports: Setting Priorities for
Drinking Water Contaminants (NRC, 1999a), Identifying Future Drinking
Water Contaminants (NRC, 1999b), and Classifying Drinking Water
Contaminants for Regulatory Consideration (NRC, 2001). The discussion
in today's notice focuses on the 2001 report, which synthesizes key
findings from the prior reports.
In its report entitled Classifying Drinking Water Contaminants for
Regulatory Consideration, the NRC recommended that EPA use a two-step
process for generating future CCLs. The first step in the process is to
select contaminants from a broad universe of chemical, microbiological,
and other types of potential drinking water contaminants for inclusion
on a preliminary CCL (PCCL), based on a screening assessment of human
health impacts, occurrence data, and expert judgement (NRC, 2001). The
second step in the process is to use a classification algorithm (a
formula or set of steps for solving a particular problem), in
conjunction with expert judgement, to select from the PCCL contaminants
to be included on the CCL. The NRC believes that this process of
selecting
[[Page 17412]]
contaminants for future CCLs will result in a more systematic,
transparent, and comprehensive approach to classifying drinking water
contaminants.
A. Screening the Universe of Contaminants
The NRC suggests that the universe of potential drinking water
contaminants could contain tens of thousands contaminants and
recommends that EPA consider a range of contaminants including
naturally occurring substances, emerging waterborne pathogens, chemical
agents, byproducts, degradates of chemical agents, radionuclides, and
biological toxins as part of the universe. The NRC's approach to
assembling the universe is to begin with data sources that are
currently available and to work with the public, the drinking water
industry, and the scientific community to develop a strategy for
assessing contaminants that are not found in existing databases or
lists (NRC, 2001). This approach could greatly expand on the number of
contaminants to be reviewed and the number of databases and lists to be
searched.
B. Compiling the PCCL
The NRC further suggested that EPA develop a well-conceived set of
screening criteria that can be applied rapidly and routinely, in
conjunction with expert judgement, to screen the universe of potential
drinking water contaminants to a much smaller PCCL.
To compile the PCCL, the NRC recommends an approach that relies on
health effects and occurrence information. The NRC suggests a screening
process that selects contaminants from a hierarchy of information based
on the following criteria related to both health effects and
occurrence:
1. Contaminants that are demonstrated to cause adverse health
effects and are demonstrated to occur in drinking water.
2. Contaminants that have the potential to cause adverse health
effects and are demonstrated to occur in drinking water.
3. Contaminants that are demonstrated to cause adverse health
effects and that have the potential to occur in drinking water.
4. Contaminants that have the potential to cause adverse health
effects and that have the potential to occur in drinking water.
The NRC advises EPA to acquire input from the public and other
``stakeholders'' on the PCCL. This approach will assist EPA in making
any policy judgements about the PCCL and will encourage transparency in
the process.
C. Contaminant Selection From the PCCL to the CCL
The second step is the selection of drinking water contaminants on
the PCCL for inclusion on the CCL.
The NRC evaluated a number of screening and assessment processes
and recommended that EPA consider the prototype classification method,
combined with expert judgement, as an effective approach for selecting
contaminants. Prototype classification uses computer-based
computational tools to weigh selected contaminant characteristics (also
called attributes) against the characteristics of drinking water
contaminants that are known to occur in drinking water and are
recognized as having negative health impacts. These attributes could
include various measures of toxicity, occurrence, and surrogates for
these measures where primary data do not exist. A prototype
classification algorithm would need to be ``trained'' to recognize
features of contaminants that should be on the CCL by inputting key
information about contaminants that we know should and should not be on
the CCL.
For demonstration purposes, the NRC used a prototype classification
approach known as a ``neural network.'' Neural networks are being used
in investment analysis to predict foreign exchange rates, credit
worthiness, and signature analysis. The approach relies on expert
judgement to determine which attributes should be used to characterize
the contaminants and the relative importance of the attributes. The
neural network then uses mathematical formulas to evaluate attributes
of contaminants against those of known contaminants and makes a
prediction based on the importance placed on the contaminants'
attributes.
In addition to suggesting a sample prototype classification method,
the NRC also identified possible attributes for use in comparing the
characteristics of potential contaminants. They suggested the following
attributes: potency, severity, prevalence, magnitude, and persistence-
mobility. The NRC considered these attributes because of their
applicability to both chemicals and microbes, and noted that, after
additional analysis and advice, EPA might well determine that other
attributes were more appropriate for developing the CCL.
D. Virulence Factor Activity Relationships for Assessing Emerging
Waterborne Pathogens
The NRC also addressed the issue of how best to examine emerging
waterborne pathogens, opportunistic microorganisms, and other newly
identified microorganisms in Classifying Drinking Water Contaminants
for Regulatory Consideration (NRC, 2001). The panel recognized several
difficulties in classifying microbiological drinking water
contaminants. These include difficulties in characterizing
microbiological contamination of drinking water, identifying the
organism responsible for outbreaks, and developing databases for
emerging pathogens. The NRC recommended that EPA explore virulence
factor activity relationships (VFARs) to address this problem. The VFAR
principle can be described as comparing the gene structure of newly
identified waterborne pathogens to pathogens with known genetic
structures which have been associated with human disease.
Virulence factors are defined broadly by the NRC as the ability of
a pathogen to persist in the environment, gain entry into a host (e.g.,
humans), reproduce, and cause disease or other health problems either
because of its architecture or because of its biochemical compounds. A
number of virulence factors are known, including the ability of a
microbe to move within a host under its own power, the ability of
mechanisms to protect the microbe against the body's defenses (e.g.,
anti-phagocytosis mechanisms), the ability of a microbe to adhere or
attach to the surface of a host cell, and the ability of microbes to
produce toxins that injure host cells.
Genetic information in the form of gene sequences has been stored
in several computerized ``libraries'' or ``gene banks'' for the use of
the research community. The NRC described several of these gene banks
and provides a list of microorganisms whose genomes have already been
studied. The NRC noted that the genetic information of additional
microbes are being added to gene banks at a rapid pace (NRC, 2001).
The NRC also recommended that EPA explore the use of gene chip
technology (also referred to as biochips, deoxyribonucleic acid (DNA)
chips, DNA microarrays, and gene arrays) to assist in classifying
drinking water contaminants. Gene chips are devices not much larger
than postage stamps. Thousands of tiny cells are typically placed on a
glass wafer. Each holds deoxyribonucleic acid, or DNA, from a different
human or microbiological
[[Page 17413]]
gene. The array of cells on a gene chip makes it possible to carry out
a large number of genetic tests on a sample at one time. At the moment,
the devices are used in pharmaceutical laboratories to investigate
which genes are involved in various normal and disease processes and to
speed up the process of finding new drugs.
The NRC believed that this approach has major and far reaching
potential and indicated that, in the near future, microarrays could be
developed that are labeled with genes for a variety of virulence
factors and could be used to assay drinking water samples for the
presence of genetic virulence factors of concern.
The NRC recognized that use of the VFAR approach to identify
potential waterborne pathogens would require a multi-year commitment
and significant cooperation and collaboration by EPA and other
participating organizations before the technology can be used to
develop the CCL.
V. Implementation of the National Research Council Recommendations
The NRC recommendations provided a possible framework for
evaluating a larger number of contaminants and making decisions about
contaminants for which data are limited through the use of innovative
technologies and expert advice. In making these recommendations, the
NRC stressed that more work is needed in the area of research and
encouraged EPA to explore different approaches for effective
implementation.
The EPA has requested the assistance of NDWAC to evaluate and
provide advice on the NRC's recommended classification process. This
section describes the role played by NDWAC in assisting EPA's
evaluation and implementation of the NRC recommendations and the
development of the classification approach.
A. The National Drinking Water Advisory Council Background and Charge
As previously noted, the 1974 SDWA established NDWAC to provide
independent advice, consultations, and recommendations to EPA on
matters related to the activities, functions, and policies of the
Agency under SDWA. To assist in this process, the NDWAC forms work
groups of experts to perform assessments of specific drinking water
issues. The work groups prepare reports and recommendations that the
NDWAC considers when making its recommendations to EPA. The NDWAC CCL
Work Group began its deliberations in September 2002. The Work Group is
comprised of 21 recognized technical and public health experts
representing an array of backgrounds and perspectives.
The NDWAC CCL Work Group is charged with discussing, evaluating,
and providing advice to the Agency on methodologies, activities, and
analysis needed to implement the NRC recommendations on an expanded
approach for the CCL listing process. The EPA is working with the NDWAC
CCL Work Group to explore issues related to a contaminant
classification approach including (1) collecting and organizing the
data, (2) screening the contaminants in the universe to compile the
PCCL, (3) classifying contaminants from the PCCL to the CCL, and (4)
developing the VFAR concept and classifying microorganisms. The NDWAC
CCL Work Group is currently discussing and evaluating the issues
related to implementing the NRC recommendations. EPA is assisting the
NDWAC CCL Work Group by conducting analyses and investigations that
inform the Work Group discussions. The NDWAC CCL Work Group expects to
present its recommendations to the NDWAC in 2004.
The NDWAC CCL Work Group and EPA have made great progress in
evaluating the NRC recommendations. The EPA recognizes that the
recommended approach would require a significant, sustained effort to
screen many more data sources for potential CCL contaminants and to
adapt computer programs for environmental contaminant selection. The
efforts to date have provided substantial information about the scope
of the effort and the challenges ahead.
B. Ongoing Analysis of the Classification Approach
1. Organizing and Extracting Data
The NRC recommended that EPA begin by considering a broad universe
of chemical, microbiological, and other types of potential drinking
water contaminants and contaminant groups. The NRC projects that the
scope of the universe could be on the order of tens of thousands of
contaminants, which represent a dramatically larger set of substances
to be initially considered in terms of types and numbers of
contaminants than that used for the creation of the 1998 CCL (262
contaminants from 8 data sources). Considering that there is no
comprehensive list of potential drinking water contaminants, and
limited data on health effects, occurrence, and other related data for
many of the potential contaminants, EPA is challenged with defining the
universe of potential drinking water contaminants, determining how it
will identify data sources, and identifying what approach it will use
for extracting information.
Based on the NRC recommendations, EPA is considering two guiding
principles for construction of the CCL universe: (1) The universe
should include those contaminants that have demonstrated or potential
occurrence in drinking water, and (2) the universe should include those
contaminants that have demonstrated or potential adverse health
effects. These inclusionary principles apply to selection of
contaminants to be included in the CCL universe. The proposed process
involves the identification of information and data sources and the
development of a means of extracting data to be merged into a CCL
universe data set.
The NDWAC CCL Work Group and EPA have identified a number of data
sources as potentially useful resources. The data sources vary widely
in their intended use (e.g., research, survey, and compliance
monitoring); type of data (e.g., concentrations, health effects,
chemical information, microbiological occurrence, environmental fate,
and genetic sequences); data format; availability; and possible
applicability to the universe of contaminants. The data sources include
the following:
Databases recommended by the NRC (NRC 1999a, 1999b,
and 2001)
Databases required by SDWA 1412(b)
Chemical structure databases (e.g., molecular
structure information used for predictive toxicology)
Chemical property databases (e.g., chemical boiling
point and solubility)
Bibliographic databases (i.e., references to
published literature)
Subscription/commercial databases
Genomic sequence databases
International databases
Other sources of information recommended by NDWAC
and other organizations
In addition to data availability and extraction issues, EPA must
also address data quality concerns. The Agency is required under SDWA
to use the best available peer-reviewed science and data collected by
accepted methods or best available methods. While the standards of
quality depend on the use to which the data is put, and screening level
analyses require less rigorous standards than some other uses (e.g.,
rule development), the data used to define the CCL universe of
contaminants must nonetheless be accurately characterized and its
quality
[[Page 17414]]
clearly understood. To satisfy these quality assurance objectives, EPA
is in the process of developing a Quality Assurance Project Plan to
cover all phases of the CCL process, from defining the universe of
contaminants to making regulatory determinations.
2. Compiling the PCCL
The NRC recommended that EPA develop a set of screening criteria
that could be applied rapidly and routinely, in conjunction with expert
judgement, to screen the universe of potential drinking water
contaminants for inclusion on the PCCL. The NRC considered this a
significant challenge, but did not deliberate extensively on the
criteria to be used for this screening. Thus, this screening step has
become an area of significant analysis by EPA and the NDWAC CCL Work
Group. Work to develop a process and criteria for screening is ongoing,
as is the analysis of methods that would enable the screening of
contaminants with little or no primary data or information.
In addition to exploring screening criteria, EPA is evaluating how
expert judgement could be used to quickly reduce a broad universe to a
manageable set of contaminants for the PCCL. While the NRC reports only
provided a conceptual recommendation for screening the universe to a
PCCL, the NRC indicated that the process should not involve an
extensive analysis of data. The NRC suggested that EPA develop coarse
screening criteria that can eliminate chemicals with low production
volume and low potential for adverse health effects, unless expert
judgement of health effects would place a chemical on the PCCL.
As previously described, EPA is coordinating efforts with the NDWAC
CCL Work Group to develop a list of occurrence databases to be used in
the analysis and will evaluate available human exposure or potential
human exposure databases such as production and use databases,
environmental release databases, and environmental media and biological
tissues monitoring databases. The toxicological or health effects
databases being evaluated include health assessment databases and
waterborne disease outbreak databases as well as other information.
For health effects screening, EPA is focusing on contaminants that
may be potent at levels near those found in drinking water and
substances with irreversible or life threatening health effects. The
NDWAC CCL Work Group is considering a number of options for processing
data and information in order to examine the relationship between
adverse health effects and occurrence in drinking water to make
decisions on movement to the PCCL.
3. Classifying Contaminants From the PCCL to the CCL
The challenge of classifying a potentially large number of
contaminants for movement from the PCCL to the CCL raises the question
of what kind of process or method is best suited for performing this
task. The NRC panel recommended the use of a prototype classification
approach combined with expert judgement. The EPA has asked NDWAC for
advice in this area and is exploring several alternative models
including: artificial neural networks, classification and regression
trees, logistic regression (a specific form of a generalized linear
model), and multivariate adaptive regression splines. Work is ongoing
to identify and test models and conduct trial classifications using a
subset of the contaminants that will be in the universe.
Use of the prototype classification approach necessitates assigning
a score to each attribute for a given contaminant. Attributes are
descriptive properties which allow different types of contaminants to
be compared in a consistent manner. The NRC recommended the following
attributes: potency (i.e., the amount of a contaminant that is needed
to cause illness); severity (i.e., the seriousness of the health
effect); prevalence (i.e., how common does or would a contaminant occur
in water); magnitude (i.e., the concentration or expected concentration
of a contaminant relative to a level that causes a perceived health
effect); and persistence-mobility (i.e., a surrogate for occurrence
when occurrence information is unavailable). The EPA and NDWAC CCL Work
Group are examining the five attributes recommended by the NRC, as well
as exploring other possible attributes.
The EPA and NDWAC CCL Work Group are also exploring how attributes
(e.g., potency) for a given contaminant might be scored using differing
data elements (e.g., the reference dose (RfD), the no observable
adverse effect level (NOAEL), and the lowest observable adverse effect
level (LOAEL)), so that the score for an attribute would reflect the
degree of the health effect or occurrence relative to other
contaminants.
The NDWAC CCL Work Group and EPA have undertaken significant
analysis with regard to the severity attribute. For example, the
following range of scores was used by the NRC to represent the severity
of a given contaminant for health effects as follows:
0. No effect
1. Changes in organ weights with minimal clinical significance
2. Biochemical changes with minimal clinical significance
3. Pathology of minimal clinical significance
4. Cellular changes that could lead to disease; minimal functional
change
5. Significant functional changes that are reversible
6. Irreversible changes, treatable disease
7. Single organ system pathology and function loss
8. Multiple organ system pathology and function loss
9. Disease likely leading to death
10. Death
The EPA and NDWAC CCL Work Group are exploring ways that the
severity scale provided by the NRC might be modified so that effects in
the middle of the scale (e.g., 4-8) would be more easily differentiated
and to allow for appropriate scoring of reproductive and developmental
effects. The EPA and NDWAC CCL Work Group are also examining possible
approaches to scoring chemicals that lack information on a critical
effect for severity.
Similarly, EPA is engaged in substantial technical analysis with
the NDWAC CCL Work Group of a possible scoring methodology for the
attribute potency. The NRC suggested that potency could be measured in
terms of the RfD, the NOAEL, the LOAEL, or by other measures.
Additional issues and challenges the NDWAC CCL Work Group is
considering include:
1. Which data elements are best suited to estimate the score for an
attribute? For example, for the attribute potency, values exist for
RfDs, NOAELs, and LOAELs.
2. In what order should data for a given contaminant be considered
given the quality, confidence, and certainty of data sources? For
example, should EPA score a contaminant using an RfD over an oral LOAEL
if both are available?
3. If no RfD or LOAEL is available, then which value should be used
to score a contaminant?
4. Should EPA review all types of data elements even when an RfD
exists?
5. How should contaminants be scored when data from different
sources suggest conflicting scores?
6. When should surrogates be used in place of the preferred data
elements? For example, using production and release data to estimate
the potential for occurrence may be a better approximation than limited
sampling in one location.
[[Page 17415]]
7. How should surrogates be expressed and scored?
8. For the health effects attributes, which populations should be
targeted in scoring (e.g., adults, children, or sensitive
subpopulations)? Is it possible to make that distinction given the data
that are available?
9. Should an assessment of certainty and confidence be incorporated
into the scoring process to reflect the quality of the data?
10. How should scoring for occurrence data elements be addressed?
11. How should subjectivity of severity scoring process be
addressed? For example, some disorders are treatable depending upon
when treatment is initiated. How should treatability be accounted for
without subjectively referring to a person's ability to obtain medical
treatment?
12. What data quality guidelines would be appropriate for
classifying contaminants from a PCCL to the CCL? Would different
guidelines for screening contaminants be appropriate from a CCL
universe to a PCCL?
13. Which models or other approaches would be best suited for
classification given the scoring approach?
4. The Virulence Factor Activity Relationship Concept and Classifying
Microorganisms
The VFAR process offers a possible alternative to identifying and
characterizing microbiological contaminants that lack information. As
previously discussed, the VFAR concept can be described as comparing
the gene structure of newly identified waterborne pathogens to
pathogens with known genetic structures that have been associated with
human disease. The NRC recommends the use of the VFAR approach for
assessing emerging waterborne pathogens, opportunistic microorganisms,
and other newly identified microorganisms. While this approach may
offer significant improvements for the future, it may not be
sufficiently developed in time for the next CCL (i.e., the 2008 CCL).
Some of the challenges to overcome include the ability of
microbiological genes to exhibit considerable adaptability by
frequently gaining or losing genetic elements. The presence of multiple
genetic elements, together with the relative frequency of chromosomal
recombinations, results in highly dynamic genes that make
predictability difficult.
Researchers have mapped about 100 entire genomes of bacteria and
viruses, and the number of mapped genomes, especially of pathogens, is
growing rapidly. Researchers store the information in several
computerized libraries, or gene banks. Sophisticated computer software
programs can sort and match genetic information in these libraries,
which can allow researchers to predict the ability of a microbe to
produce virulence factors, and compare a microbe to known pathogens.
Some waterborne pathogens have similar toxins, surface proteins, and
mechanisms of infection, and some of the genes for these factors have
been identified.
The NDWAC CCL Work Group and EPA are exploring a means of using
gene banks for drinking water applications. For example, EPA searched
for genetic sequences associated with virulence using the National
Center for Biotechnology Information's GenBank database. The database
contains a large list of such sequences, most of which are associated
with pathogens or microbes used in laboratory studies. Initial findings
indicate that some relevant sequence data are available, however, the
data were in a form that proved difficult to use for this purpose.
The EPA is also coordinating efforts with the NDWAC CCL Work Group
to evaluate an approach based on bioinformatics to extract relevant
information from databases and literature sources on known waterborne
pathogen gene sequences. The information could provide the gene
sequences needed to demonstrate the potential use of gene chip
technology in performing VFAR analysis.
The EPA is also exploring alternative approaches to screen microbes
for the next CCL, given the uncertainty surrounding the time frame for
a fully developed VFAR approach. For example, EPA is exploring an
approach that would construct a microbiological universe, define
microbiological attributes, and score the attributes.
The EPA believes that the NRC recommendations hold substantial
promise and is exploring ways to take the recommendations beyond the
conceptual framework to development and implementation. Additionally,
EPA is working with the NDWAC CCL Work Group to define the dimensions
of the microbiological universe as part of a step-wise process for
defining the CCL. The EPA welcomes comments on these and other relevant
microbiological issues to assist the Agency in addressing the NRC
recommendations.
VI. Request for Comment
The EPA seeks comments on the range of CCL issues and activities
addressed in this notice. EPA is also requesting comment on its
decision to carry over the remaining contaminants on the 1998 CCL as
the draft CCL 2. The Agency is asking for public comments on the
following questions related to the process for developing the 2008 CCL:
1. Which data sources should the Agency use to assemble the
universe of potential CCL contaminants?
2. Should the Agency adopt the general framework of moving from a
broad universe of potential candidates to a PCCL and finely to a CCL?
3. If so, what criteria should be used for inclusion of a
contaminant on the PCCL, and in selecting contaminants from the PCCL to
the CCL?
4. How should EPA address contaminants that lack data on toxicity,
occurrence, and exposure?
In addition, the Agency welcomes comments on other aspects of the
approach recommended by the NRC.
The EPA expects that public comments on these and other relevant
issues will assist the Agency in addressing remaining questions posed
by the NRC and the NDWAC and welcomes comments from the public. The
Agency recognizes that, while the draft CCL 2 has not been compiled
using the new approach recommended by the NRC, many of the underlying
principles and objectives remain the same. Information and comments
submitted on this notice will be considered in determining the final
CCL 2 list, as well as in the development of future CCLs and in the
Agency's efforts to set drinking water priorities in the future.
VII. References
NRC. 1999a. Setting Priorities for Drinking Water Contaminants.
National Academy Press, Washington, DC http://www.nap.edu/catalog/6294.html
.
NRC. 1999b. Identifying Future Drinking Water Contaminants. National
Academy Press, Washington, DC http://www.nap.edu/catalog/9595.html.
NRC. 2001. Classifying Drinking Water Contaminants for Regulatory
Considerations. National Academy Press, Washington, DC http://books.nap.edu/books/0309074088/html/index.html
.
EPA. 1991. Priority List of Substances Which May Require Regulation
Under the Safe Drinking Water Act. Notice. Federal Register Vol 56,
No. 9, p. 1470. January 14, 1991.
EPA. 1997a. EPA Drinking Water Microbiology and Public Health
Workshop. Washington, DC, EPA, Office of Ground Water and Drinking
Water, May 20-21, 1997.
Dated: March 16, 2004.
Benjamin H. Grumbles,
Acting Assistant Administrator, Office of Water.
[FR Doc. 04-7416 Filed 4-1-04; 8:45 am]
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