[Federal Register Volume 69, Number 64 (Friday, April 2, 2004)]
[Notices]
[Pages 17406-17415]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-7416]


-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

[FRL-7641-5]


Drinking Water Contaminant Candidate List 2; Notice

AGENCY: Environmental Protection Agency.

ACTION: Notice.

-----------------------------------------------------------------------

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 [email protected]. For 
general information contact the EPA Safe Drinking Water Hotline at 
(800) 426-4791 or e-mail: [email protected]. 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 [email protected], 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
------------------------------------------------------------------------
                  List                             Description
------------------------------------------------------------------------
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]
BILLING CODE 6560-50-P