EPA-815-Z-98-001
Monday
March 2, 1998
Part II!
Environmental
Protection Agency
Announcement of the Drinking Water
Contaminant Candidate List; Notice
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Federal Register/Vol. 63, No. 40/Monday, March 2, 1998/Notices
ENVIRONMENTAL PROTECTION
AGENCY
[W-97-11; FRL-5972-5]
Announcement of the Drinking Water
Contaminant Candidate List
AGENCY: U.S. Environmental Protection
Agency (EPA).
ACTION: Notice.
SUMMARY: The Safe Drinking Water Act
(SOWA), 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 regulation (NPDWR), that are
known or anticipated to occur in public
water systems and which may require
regulations under the SDWA [section
1412(b)(l)J. The SDWA. as amended,
specifies that EPA must publish the first
list of contaminants (Drinking Water
Contaminant Candidate List, or CCL)
not later than 18 months after the date
of enactment, i.e., by February 1998,
and every five years thereafter. The
SDWA, as amended, also specifies that
the CCL must be published after
consultation with the scientific
community, and after notice and
opportunity for public comment.
A draft CCL was published in the
October 6, 1997 edition of the Federal
Register (62 FR 52193) in order to seek
comment from the public. Seventy-one
comments were received. The
comments have been reviewed and
considered in creating the final CCL
presented in today's notice. The CCL is
divided among contaminants which are
Identified as priorities for drinking
water research, those which need
additional occurrence data, and
contaminants which are priorities for
consideration for the development of
future drinking water regulations and
guidance. The CCL includes 50
chemical and 10 microbiological
contaminants/contaminant groups.
The full record for this notice has
been established under docket number
W-97-11, and includes supporting
documentation as well as all comments
received In response to the October 6.
1997 notice. The full record is available
for inspection from 9:00 a.m. to 4:00
p.m., Monday through Friday, excluding
legal holidays at the Office of Water
Docket, East Tower Basement, USEPA
Headquarters, 401 M Street, S.W.,
Washington, D.C. For access to the
docket, please call 202-260-3027 to
schedule an appointment.
FOR FURTHER INFORMATION CONTACT: For
general information, please contact the
EPA Safe Drinking Water Hotline. The
toll-free number is 800-426-4791. The
Hotline operates from 9:00 a.m. to 5:30
p.m., Monday through Friday, excluding
legal holidays. For specific information
on the Contaminant Candidate List and
the contaminant identification process,
please contact Ms. Evelyn Washington,
at the U.S. Environmental Protection
Agency, Office of Ground Water and
Drinking Water, Mailcode 4607,
Washington, D.C. 20460, phone: 202-
260-3029, fax: 202-260-3762, email:
washington.evelyn@epamail.epa.gov.
EPA Regional Offices
I. JFK Federal Bldg., Room 2203, Boston,
MA 02203. Phone: 617-565-3602,
Jerry Healey
II. 290 Broadway, Room 2432, New
York, NY 10007-1866. Phone: 212-
637-3880, Walter Andrews
III. 841 Chestnut Street, Philadelphia,
PA 19107. Phone: 215-566-5775,
Jeff Hass
IV. 61 Forsyth Street, SW, Atlanta GA
30303. Phone: 404-562-9480,
Janine Morris
V. 77 West Jackson Blvd., Chicago, IL
60604-3507. Phone: 312-886-4239,
Kim Harris
VI. 1445 Ross Avenue, Dallas, TX
75202. Phone: 214-665-7150, Larry
Wright
VII. 726 Minnesota Ave., Kansas City,
KS 66101. Phone:913-551-7410,
Stan Calow
VIII. One Denver Place, 999 18th Street,
suite 500, Denver, CO 80202.
Phone: 303-312-6627, Rod Glebe
IX. 75 Hawthorne Street, San Francisco,
CA 94105. Phone: 415-744-1884,
Bruce Macler
X. 1200 Sixth Avenue, Seattle, WA
98101. Phone: 206-553-1893, Larry
Worley
SUPPLEMENTARY INFORMATION:
Abbreviations Used in This Notice
AMA—American Medical Association
AWWARF—American Water Works
Association Research Foundation
CAA—Clean Air Act
CASRN—Chemical Abstract Services
Registry Number
CCL—Contaminant Candidate List
CERCLA—Comprehensive
Environmental Response,
Comprehensive and Liability Act
CPVC—Chlorinated Polyvinyl Chloride
DBPR—Microbiological and
Disinfection Byproducts Regulations
DWEL—Drinking Water Equivalent
Level
DWPL—Drinking Water Priority List
EDSTAC—Endocrine Disrupter
Screening and Testing Advisory
Committee
EPA—Environmental Protection Agency
ESWTR—Enhanced Surface Water
Treatment Rule
FIFRA—Federal Insecticide, Fungicide,
and Rodenticide Act
FQPA—Food Quality Protection Act
FR—Federal Register
GWDR—Ground Water
GW—Ground Water Disinfection Rule
IRIS—Integrated Risk Information
System
MCL—Maximum Contaminant Level
MCLG—Maximum Contaminant Level
Goal
MTBE—Methyl-t-butyl Ether
NAS—National Academy of Sciences
NAWQA—National Water Quality
Assessment Program
NOW AC—National Drinking Water
Advisory Council
NOAEL—No-Observed-Adverse-Effect-
Level
NPDWR—National Primary Drinking
Water Regulations
NPL—National Priority List
NSF—National Sanitation Foundation
OPP—EPA's Office of Pesticide
Programs
OPPTS—EPA's Office of Pollution
Prevention and Toxic Substances
PGWDW—Pesticides in Ground Water
Database
PVC—Polyvinyl Chloride
RfD—Reference Dose
SAB—EPA's Science Advisory Board
SAP—Science Advisory Panel
SDWA—Safe Drinking Water Act
SWTR—Surface Water Treatment Rule
TTHM—total trihalomethane
TSCA—Toxic Substances Control Act
UCMR—Unregulated Contaminant
Monitoring Regulations
WHO—World Health Organization
Table of Contents
I. Background
II. Drinking Water Contaminant Candidate
List
Table 1. Drinking Water Contaminant
Candidate List
m. Changes Made to Create the Final
Contaminant Candidate List Based on
Comments Received on the Draft
A. Acetochlor, Metolachor, and Alachlor
ESA
B. Acetone and Cumene
C. Aldicarbs and Nickel
D. Aluminum
E. Dimethoate
F. DTBB
G. Methyl Bromide
H. Microorganisms
I. MTBE
J. Organotins
K. Perchlorate
L. Rhodamine WT
M. Sodium
N. Triazines
O. Zinc
IV. Continuing Work in Preparation for
Future CCLs
A. Pesticides Deferred
B. Endocrine Disrupters
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C. Development of the Contaminant
Selection Process
V. Data, Research Needs and Next Steps
Table 2. Next Steps for the CCL
VI. Other Requirements
VII. References
I. Background
The Safe Drinking Water Act (SDWA),
as amended in 1996, requires the
Environmental Protection Agency (EPA)
to publish a list of contaminants that are
known or anticipated to occur in public
water systems, and which may require
regulation under the SDWA [section
1412(b)(l)]. The SDWA, as amended,
also specifies that EPA must publish
this list of contaminants (Drinking
Water Contaminant Candidate List, or
CCL) not later than 18 months after the
date of enactment (i.e., by February
1998), and publish a new CCL every five
years thereafter. The SDWA requires
that the list of contaminants include
those which, at the time of publication,
are not subject to any proposed or
promulgated national primary drinking
water regulation (NPDWR). The list
must be published after consultation
with the scientific community,
including the Science Advisory Board,
after notice and opportunity for public
comment, and after consideration of the
occurrence database established under
section 1445(g). The unregulated
contaminants considered for the list
must include, but not be limited to,
substances referred to in section 101(14)
of the Comprehensive Environmental
Response, Compensation, and Liability
Act of 1980 (CERCLA), and substances
registered under the Federal Insecticide,
Fungicide, and Rodenticide Act
(FIFRA).
Today's notice is being published
pursuant to the requirements in section
1412(b)(l). The contaminants included
are not subject to any proposed or
promulgated national primary drinking
water regulation, are known or
anticipated to occur in public water
systems, and may require regulation
under the SDWA. During the
development of the CCL, the Agency
consulted with stakeholders, including
the National Drinking Water Advisory
Council's (NOWAC) Working Group on
Occurrence & Contaminant Selection,
which includes microbiologists,
toxicologists. public health scientists,
and engineers, and consulted with other
members of the scientific community
including the Science Advisory Board
(SAB). A draft CCL was published in the
October 6, 1997 edition of the Federal
Register (62 FR 52193) to seek comment
from the public.
Seventy-one comments were received
in response to the notice on the draft
CCL; 66 comments were received by the
due date, and an additional 5 comments
were received later. The majority were
supportive of the CCL process and the
development of this first CCL, and
provided suggestions on specific
contaminants that should be included
on, or excluded from, the CCL. The
comments, data, and information
provided were taken into consideration
in preparing the final CCL presented in
today's notice. Modifications to the CCL
presented in today's notice were also
reviewed by the National Drinking
Water Advisory Council (NOWAC), and
the NDWAC Working Group on
Occurrence & Contaminant Selection.
The Agency believes the CCL
presented in today's notice is a first step
toward improving risk assessment,
strengthening science and data, and
achieving better decision-making and
future priority setting. The CCL is
designed to be responsive to each of the
requirements noted above of the SDWA,
as amended, and is consistent with the
goals of the Drinking Water Redirection
Strategy. The CCL is the result of a
concerted effort of screening a larger set
of contaminants to a subset of those of
most concern.
This final CCL will be the primary
source of priority contaminants for the
Agency's drinking water program. The
list is divided among priorities for
drinking water research, priorities for
additional occurrence data collection,
and those contaminants which are
priorities for consideration for Agency
determinations of whether or not to
regulate specific contaminants by
August 2001.
The SDWA does not preclude the
Agency from taking action on a
contaminant not included on the CCL.
The EPA can decide to monitor, develop
guidance, or conduct research, for a
contaminant not included on the CCL.
The Agency can also develop
regulations to address an urgent threat
to public health under SDWA [section
1412(b)(l)(D)]. The Agency is also not
precluded from modifying the CCL prior
to the due date of the next CCL, which
is February 2003.
II. Drinking Water Contaminant
Candidate List
The following table includes the
contaminants, microbiological and
chemical, presented as the Drinking
Water Contaminant Candidate List. The
chemical contaminants in the table are
identified by name and Chemical
Abstracts Service Registry Number
(CASRN). The CCL includes 50
chemical and 10 microbiological
contaminants/contaminant groups.
TABLE 1.—DRINKING WATER CONTAMINANT CANDIDATE LIST
Microbiological contaminants
Acanthamoeba (guidance expected for contact lens wearers)
Adenoviruses
Aeromonas hydrophila
Calicivi ruses
Coxsackieviruses
Cyanobacteria (blue-green algae), other freshwater algae, and their toxins
Echoviruses
Helicobacter pylori
Microsporidia (Enterocytozoon & Septata)
Mycobacterium avium intracellulare (MAC)
Chemical contaminants
1 .3-DichloroDrooene
CASRN
79-34-5
95-63-6
75-34-3
563-58-6
122-66-7
142-28-9
542-75-6
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Chemical contaminants
CASRN
2,4,6-lrichlorophonol 88-06-2
2,2-dlchloropropane 594-20-7
2.4-dtehlorophenol 120-83-2
2,4-dinitrophonol 51-28-5
2,4-dtnitrotoluene 121-14-2
2,6-dinitrotoluene 606-20-2
2-mothyl-PhQnol (o-cresol) 95-48-7
Acolochlor 34256-82-1
Alachlor ESA & other acetanilide pesticide degradation products N/A
AWrin 309-00-2
Aluminum 7429-90-5
Boron 7440-42-8
Bromobonzeno 108-86-1
DCPA mono-acid degradate 887-54-7
DCPA di-acid degradate 2136-79-0
DDE , 72-55-9
Dlazinon 333-41-5
Dioldrin 60-57-1
Disulfoton 298-04-4
Diuron 330-54-1
EPTC (s-ethyl-dlpropylthlocarbamate) 759-94-4
Fonofos 944-22-9
Hexachlorobutadlene 87-68-3
p-Isopropyltoluene (p-cymene) gg-ay-e
Unuron 330-55-2
Manganese 7439-96-5
Mothyl bromide 74-83-9
Mothyl-t-butyl ether (MTBE) ".."". 1634-04-4
Motolachlor 51218-45-2
Motribuzin 21087-64-9
Molinate 2212-67-1
Naphthalene 91-20-3
Nitrobenzene 1. 98-95-3
Organotins N/A
Porchlorate \ N/A
Prometon 1610-18-0
RD* • 121-82-4
Sodium 7440-23-5
Sulfate 14808-79-8
Torbacll 5902-51-2
Torbufos 13071-79-9
Trlazlnes & degradation products of triazines (including, but not limited to Cyanazine 21725-46-2, and atrazine-desethyl 6190-
OO""^T I*
Vanadium 7440-62-2
III. Changes Made to Create the Final
Contaminant Candidate List Based on
Comments Received on the Draft
The criteria which EPA used to select
the contaminants for the CCL are
described in detail in the October 6,
1997 notice (62 FR 52193) on the draft
CCL. In general, the criteria for
including a contaminant on the CCL
consisted of determinations of whether
the occurrence, or anticipated
occurrence, of a contaminant was likely
at levels of concern to human health.
The October notice solicited input from
the public and specifically requested
comments on (1) the approach EPA used
to create the list and suggestions on the
process for future lists; (2) contaminants
on the Hst; (3) data needs categories; and
(4) whether to include perchlorate on
the CCL.
EPA received 71 comments, 66 by the
deadline and 5 additional late
comments. The majority of comments
were supportive of the CCL process, and
the development of this first CCL.
Comments were received from a number
of segments of the stakeholder
community, including equipment
manufacturers, consultants, chemical
manufacturers, trade associations,
environmental groups, state 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, as well as
feedback on the data and research needs
indicated for the contaminants on the
CCL. Roughly 60 issues were raised by
the comments, both contaminant-
specific and related to the development
of a process for identifying
contaminants for future CCLs. The
comments, data, and information
provided were taken into consideration
in preparing the final CCL presented in
today's notice. Proposed changes to the
CCL were also reviewed by the NDWAC
Working Group on Occurrence &
Contaminant Selection, and the
NDWAC full-Council.
A number of comments indicated that
many did not understand the function
of the CCL. The CCL is not the list of
contaminants for which the Agency has
made a determination to regulate. The
CCL is a list of priority contaminants
(not otherwise addressed) for drinking
water program activities which include
those for: (1) drinking water research,
(2) monitoring, (3) guidance
development, as well as those for (4)
selection and regulatory determination
by the year 2001. The next steps likely
to occur with regard to any given
contaminant are discussed in more
detail in Section V in today's notice.
Despite the support expressed for the
development of this first CCL,
commenters advised that more robust
criteria are needed for future CCL
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10ZT7
development and for contaminant
selection. The Agency agrees with these
commenters and will continue to work
to develop a contaminant identification
process for chemical and
microbiological contaminants to be used
to develop future CCLs. Section IV.C. of
today's notice provides additional
information on how the Agency plans to
develop these processes.
The following is a summary of the
significant public comments received
that led to changes to the CCL. The
remainder of this section responds to
the more significant comments, and
indicates how the CCL was changed in
response to these comments. A
complete report of responses to all
comments received on the notice of the
draft CCL can be found in the docket.
A. Acetochlor, Metolachor, and
AlachlorESA
A number of commenters supported
the inclusion of acetochlor, metolachor,
and alachlor ESA (the sulfonic acid
degradate of alachlor) on the CCL, while
others indicated that they should not be
included. Three commenters indicated
that acetochlor should have low priority
for regulation, and that the Agency
should consider deleting it from the
CCL. The commenters argued that under
the Acetochlor Registration Project, the
EPA has established very conservative
triggers for its potential cancellation of
use as a pesticide. The commenters
went on to indicate that in 175 :
community water systems monitored
since March 1995, acetochlor detections
have occurred in only 20% of samples,
that no system had an average mean
concentration exceeding 2 ppb, which is
one of the triggers, and that additional
monitoring data will indicate that
concentrations found in public water
systems are far below 140 ppb.
One commenter argued that
metolachlor should not be included on
the CCL. That although it is detected in
water, it is rarely above the lifetime
health advisory level of 70 ppb, and the
detections in most cases are associated
with point sources. The commenter
stated that data collected under the
Unregulated Contaminant Monitoring
Regulations is available on a state-by-
state basis, and the results reported from
3 States also indicate no detections
above the lifetime health advisory level
of 70 ppb. Another commenter
suggested that alachlor ESA should not
be included on the CCL, as it, too,
should have a low priority for regulation
based on concentrations in water not
exceeding 6370 ppb.
Other commenters argued that
metolachor, acetochlor, and alachlor
ESA should be kept on the CCL since
States reported finding these
contaminants in water. One commenter
added that the metolachor ESA and
metolachor OA degradation products
should be included on the CCL also,
since all have been found in ground
water.
One commenter also pointed out that
metolachlor, acetochlor, and alachlor do
not have a common mode of action, and
thus cannot be grouped together to
develop a single standard to address all
acetanilide pesticides.
EPA Response
The Agency disagrees with the
commenters who believe it is
inappropriate to include acetochlor,
metolachor, and alachlor ESA on the
CCL. By including these contaminants
on the CCL, the Agency has not yet
made a determination with respect to
regulating any of them. In light of the
reported occurrences of these
contaminants in water, the drinking
water program needs to determine what
action is appropriate to ensure the
protection of public health even if the
action may be only the development of
guidance for States and public water
systems. The Office of Water will
evaluate further the available toxicity
and occurrence information for these
pesticides in order to determine
appropriate concentration values
adequate to protect against risks
associated with exposure through
drinking water. With respect to
metolachlor specifically, the Agency
believes it is appropriate to include it on
the CCL. The data collected under the
Unregulated Contaminant Monitoring
Regulations is being collected from all
States and will be compiled and
evaluated as additional information is
collected and evaluated for all
contaminants on the CCL.
The Agency agrees that it is
appropriate to include other acetanilide
pesticide degradation products in
addition to alachlor ESA, since they,
too, have been found in ground water.
However, at this time, the Agency has
not yet determined which are the most
important to include; therefore, EPA has
decided to include alachlor ESA & other
acetanilide pesticide degradation
products as a group of contaminants on
the CCL. The determination of which
degradation products are of most
concern will be determined as we learn
more about these contaminants as a
class. The Agency also agrees with the
commenter that because alachlor,
acetochlor, and metolachlor do not have
a common mode of action, they are not
at this time appropriate contaminants to
be grouped together to develop a single
approach addressing all acetanilide
pesticides. Contrary to earlier
statements, acetanilide pesticides are
not likely candidates for development of
"total standards" in the foreseeable
future. However, the Agency is
interested in the development of "total
standards," or standards that address
classes of compounds, where
appropriate, and as the state of the
science improves.
B. Acetone and Cumene
Two commenters remarked that
outdated oral reference doses (RfD) from
the Integrated Risk Information System
(IRIS) for acetone and cumene were
used in developing the draft CCL and
that analyses should be done with
current information. The Chemical
Manufacturers Association's Acetone
Panel submitted comments about
acetone and recommended that it
should not be included on the final
CCL. The reason given, in addition to
the outdated RfD, was that outdated
information concerning levels of
acetone detected in the environment,
including data from old National
Priority List (NPL) sites had been used
in the Agency's evaluation and that this
did not provide a reliable basis for
estimating likely levels of acetone in
drinking water or sources of drinking
water. The Panel believes more relevant
information shows that acetone is
unlikely to be present in drinking water
or sources of drinking water at levels of
concern.
The Chemical Manufacturers
Association's Cumene Panel submitted
comments about cumene and
recommended that it should not be
included on the final CCL. The reason
given, in addition to the outdated RfD,
was that concentrations of cumene
detected in the environment were not at
levels of concern, and it is rarely
detected in drinking water or sources of
drinking water.
EPA Response
The Agency agrees with the
commenters that the current IRIS values
should be used in the evaluations for
developing the CCL. The updated value
for acetone has not been posted on the
IRIS database; however, the Agency has
acknowledged the new value of 0.9 mg/
kg/day previously in a notice
concerning section 313 of the
Emergency Planning and Community
Right-to-Know Act (60 FR 31644). The
updated value for cumene has been
posted on the IRIS database, and is 0.1
mg/kg/day.
The occurrence data from the U.S.
Geological Survey's National Water
Quality Assessment Program (NAWQA)
indicates that acetone was detected at a
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frequency of greater than 10% of the
samples collected; however, the
concentrations found did not exceed
their reporting level of 0.2 pg/1. When
the current IRIS values are used for
acetone and cumene, and compared to
the available occurrence data, neither
meets the criteria set forth for
identifying contaminants for the CCL,
and therefore, acetone and cumene have
been removed from the CCL.
C. Aldlcarbs and Nickel
EPA received a number of comments
encouraging the inclusion of aldicarbs
and nickel on the CCL, while a few
commented that it was inappropriate to
include these contaminants, despite the
Agency's existing statutory obligation
with regard to these contaminants.
EPA Response
In the case of aldicarbs (aldicarb,
aldicarb sulfoxide, aldicarb sulfone) and
nickel, the Agency has determined that
it is inappropriate to include these
contaminants on the CCL. The 1996
Amendments to SDWA explicitly
reenacted the requirements for
regulation of these contaminants
(section 1412 (b)(2)). In response to an
administrative petition from the
manufacturer Rhone-Poulenc, the
Agency issued an administrative stay of
the effective date of the maximum
contaminant levels (MCLs) for aldicarbs,
and they never became effective.
NPDWRs for nickel were promulgated
on July 17, 1992, but the MCL was later
vacated and remanded in response to a
lawsuit from the Nickel Development
Institute and other industry parties.
The Agency intends to complete
regulatory action for both aldicarbs and
nickel. The time-frame of completing
action for these contaminants is likely to
be the same time-frame required by
SDWA for regulatory determinations for
contaminants on the CCL. When
considering the nature and type of work
necessary to complete action on these
contaminants, the effort for aldicarbs is
anticipated to be less extensive than that
required for nickel; thus, regulations for
aldicarbs are likely to be completed
prior to regulations for nickel.
D. Aluminum
EPA received four comments
recommending that aluminum not be
included on the CCL. One commenter
stated that regulations would be
premature at this time, due to the need
for additional information on the risk of
adverse effects and occurrence in
drinking water. Other commenters
argued that there was no scientific
health basis for the inclusion of
aluminum on the CCL, and that the
World Health Organization (WHO)
stated in 1995 that there is an
inadequate basis for revising existing
guidelines for aluminum below the 200
p.g/1 standard used to control taste and
odor effects. The commenters also
explained that the source of aluminum
in drinking water is primarily linked to
the use of alum as a flocculent in water
treatment, and the implications of
regulating aluminum at lower levels
could cause deleterious effects on water
quality.
An additional commenter felt that
aluminum should be included on the
CCL based on new literature on the
relationship of aluminum to
Alzheimer's Disease, elderly mental
impairment, and childhood learning
disabilities. The commenter disagreed
with the need for additional data on the
health impacts of aluminum. The
commenter contends that much more is
actually known today about how
aluminum causes neurological injury
than is known for lead, and that there
is as much data on the health effects of
aluminum as was ever available for
lead.
EPA Response
The Agency disagrees with the
commenters who indicated that
aluminum should not be on the CCL.
The Agency believes it is appropriate to
include aluminum on the CCL because
of the new developments and research
on aluminum epidemiology indicating a
potential link between aluminum and
adverse neurological effects. It is clear
that additional studies are needed to
characterize the risk of this contaminant
from exposure through drinking water.
Due to aluminum's widespread
occurrence and the recent studies
indicating some association with
Alzheimer's like symptoms and other
potential neurotoxic effects, the Agency
believes aluminum warrants further
investigation. It is also EPA's opinion
that additional data are needed to
determine an adequate no-observed-
adverse-effect-level (NOAEL) for
potential chronic neurotoxicity. The
inclusion of a contaminant on the CCL
does not necessarily mean that the
contaminant will be regulated.
Contaminants on the CCL include those
priorities for which the Agency must
make a determination of whether or not
to regulate by the year 2001, and
priority contaminants for which the
Agency will gather additional data and
conduct research. At this time, the EPA
has included aluminum among the
contaminants for which additional
research is needed.
E. Dimethoate
One commenter suggested that
dimethoate be deleted from the CCL.
The major reasons given were that
dimethoate did not meet the occurrence
criteria, because data used in the
Agency's analysis from the Pesticides in
Ground Water Database (PGWDB) report
were recorded erroneously, and that the
IRIS values lack critical evaluation and
therefore should not be considered in
evaluating whether a contaminant
should be included on the CCL.
EPA Response
The Agency agrees with the
commenter on the point raised about the
occurrence data, but not on the point
raised about the use of IRIS values.
Based on the faulty occurrence data,
dimethoate has therefore been removed
from the CCL.
In general, the RfD is an estimate
(with uncertainty spanning perhaps an
order of magnitude) of a daily exposure
to the human population (including
sensitive subgroups) that is likely to be
without an appreciable risk of
deleterious effects during a lifetime. The
health assessment information and RfD
values on a chemical substance are
included in IRIS only after a
comprehensive review of chronic
toxicity data by U.S. EPA health
scientists from several program offices
and the Office of Research and
Development. The Agency believes it is
entirely appropriate to use RfD values
reported to IRIS in the absence of
drinking water health advisory values in
the derivation of health levels of
concern for determining if a
contaminant should be included on the
CCL.
However, according to EPA's Office of
Pesticide Programs (OPP), the office that
prepared the PGWDB report, and the
Georgia Department of Natural
Resources, the data reported for the
State of Georgia are incorrect. The
laboratory analysis sheets from the
Georgia Ground Water Management
Laboratory Program indicate dimethoate
was not detected in any samples in the
State. By eliminating the occurrence
data from the PGWDB report for the
State of Georgia and replacing it with
this new information, which the Agency
feels is appropriate, dimethoate no
longer meets the criteria for inclusion
on the CCL, and has therefore been
removed.
F. DTBB
DTBB, also known as 2,6-di-tert-butyl-
p-benzoquinone, is a contaminant that
appears to be associated with sewage
contamination of ground water, and is
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102T9
considered by some to be a good
indicator of such contamination. DTBB
was determined not to meet the criteria
for the CCL per se, but was included on
the draft list nevertheless, because of the
persistent nature of the contaminant,
and its potential to serve as an indicator.
One commenter stated that coliforms
and nitrate already serve the purpose as
indicators of contamination, and that it
was pointless to include DTBB on the
CCL, since it, in fact, did not meet the
criteria.
EPA Response
The Agency agrees with the
commenter and has removed DTBB
from the CCL. DTBB does not meet
criteria set forth for identifying
contaminants for the CCL, and since
there are currently acceptable indicators
of sewage contamination in the use of
total coliforms, its inclusion is
unnecessary.
G. Methyl Bromide
Several commenters supported the
inclusion of methyl bromide on the
CCL. The principal reason cited by
commenters was the widespread use of
methyl bromide as a fumigant and its
likely occurrence in drinking water
sources. One commenter indicated that
although the frequency of detection in
samples was less than 0.1% in ambient
water monitoring conducted by the U.S.
Geological Survey, methyl bromide
should be considered for inclusion
because the environmental significance
may warrant it.
EPA Response
Methyl bromide, which is also known
as bromomethane, was included on the
draft CCL based on input from
stakeholders that it was found in
drinking water. In response to the
comments, EPA has reevaluated the
available information on methyl
bromide occurrence. Contrary to
assertions of likely widespread
occurrence in source water due to its
use as a fumigant, the U.S. Geological
Survey ambient water monitoring
indicates it occurs at less than 0.1%
frequency, at very low concentrations
(less than 0.2 ng/1). However,
unregulated contaminant monitoring
data collected from States indicates
methyl bromide occurred in 0.8% of the
public water systems. One explanation
for this apparent anomaly could be that
the finished water occurrence comes not
from its use as a fumigant, but that
methyl bromide is associated with the
disinfection processes used for drinking
water treatment. Nevertheless, methyl
bromide met the criteria for inclusion
on the CCL; the concentrations reported
(maximum 29 (ig/1) in the unregulated
contaminants database exceeded the
health level of 0.8 |ig/l.
Methyl bromide is a gas produced by
both manmade and natural sources.
Methyl bromide is primarily used for
soil fumigation (87%), but its other
agricultural uses include: commodity
and quarantine treatment (8%), and
structural fumigation (5%). When used
as a soil fumigant, methyl bromide is
injected into the soil at a depth of 12 to
24 inches. About 50 to 95% of the
methyl bromide injected in the soil
eventually enters the atmosphere. About
80 to 95% of the amount used for
commodity treatments, and well over
90% used for structural fumigation
eventually enters the atmosphere. A
significant quantity of methyl bromide
used for agricultural purposes is known
to escape to the atmosphere due to its
volatile nature. Therefore, the U.S.
Geological Survey data indicating less
than 0.1% frequency of occurrence is
consistent with what would be expected
to present in ground water due to
methyl bromide's use as a fumigant.
Methyl bromide is also considered a
Class I ozone depleting substance, and
as such, its use is being phased out
around the world by the Montreal
Protocol, and in the U.S., by the Clean
Air Act (CAA). The Montreal Protocol is
an international treaty developed to
protect the earth from the detrimental
effects of ozone depletion, and to
control the production and trade of
ozone depleting substances on a global
basis. Title VI of the CAA, as amended
in 1990, requires that certain ozone
depleting substances be phased out in
the U.S. within seven years. Under the
CAA, the EPA has prohibited the
production and importation of methyl
bromide starting January 1, 2001. As a
result, given methyl bromide's lack of
persistence, occurrence in source waters
will likely decrease even more.
If methyl bromide is a disinfection '
byproduct, EPA has a number of rules
and activities currently in place and
under development to address it. In
1979, EPA issued an NPDWR
establishing an MCL for the total
trihalomethanes (TTHMs) disinfection
byproducts. The Agency is also in the
process of updating the disinfection
byproducts regulation. In 1994, EPA
proposed a revised standard for TTHMs
and a new standard for haloacetic acids.
The TTHMs were regulated not only to
control trihalomethanes, but also to
protect against other similar byproducts.
Because of structural similarity, steps to
reduce formation ofTTHMs would also
reduce formation of methyl bromide.
The treatment technique of enhanced
coagulation, included in the 1994
proposed DBPR, will remove
disinfection byproduct precursors, thus
reducing the levels of disinfection
byproducts in finished waters. Although
methyl bromide is not a TTHM, for
which an MCL is explicitly established,
the Agency believes it would be
effectively controlled under the DBPR.
However, it is not clear whether methyl
bromide is being formed due to
disinfection.
Because it cannot be determined
whether methyl bromide is being
formed due to disinfection, and its use
as a fumigant cannot be completely
dismissed as source of drinking water
contamination, the Agency has decided
to retain methyl bromide on the CCL. At
the January 7, 1998 meeting, the
NDWAC Working Group on Occurrence
& Contaminant Selection concurred
with the EPA recommendation to delete
methyl bromide because it was being
addressed in ongoing rulemakings for
disinfection byproducts. However, at
the February 2, 1998 meeting, the full
NDWAC recommended the Agency
retain methyl bromide on the CCL after
receiving comment that because it is a
mono-halogenated compound, it was
not specifically regulated with the
TTHM family which are tri-halogenated
compounds, and that it may not turn out
to be a disinfection byproduct. At the
meeting, EPA was insufficiently lucid in
explaining the connection between the
TTHM byproducts and the control of
similar byproducts. Nonetheless, after
further consideration of the NDWAC
recommendation, and given the
uncertainties about the source, EPA has
concluded that methyl bromide should
remain on the CCL.
Since methyl bromide is a gas, most
health studies have used the inhalation
route of exposure, and the effects of oral
exposure have received limited
attention. In 1989, EPA classified
methyl bromide as a Group D
carcinogen (not classifiable) due to
inadequate bioassay data. At the time of
the IRIS assessment, also in 1989, a
chronic oral study was not available,
therefore an additional uncertainty
factor of 10 (total uncertainty of 1,000)
was applied to the RfD calculation.
However, since the IRIS assessment, a 2-
year rat feeding study showed no
evidence of carcinogenicity, and a
National Toxicology Program inhalation
study, conducted in 1992, found no
evidence of carcinogenicity. The Agency
will also explore the potential sources of
drinking water contamination, and the
expected impact of the prohibited
production and importation of methyl
bromide which begins in January 1,
2001. Methyl bromide is listed on the
Research Priorities portion of the CCL to
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allow the Agency time to better
determine the drinking water risk due to
this contaminant.
H. Microorganisms
Many commenters stated that the
rationale for the inclusion of
microorganisms appeared to be
Inconsistent. They suggested that other
microorganisms would have been
included had the criteria been used
consistently. It was not the intention of
EPA, nor the participants of the EPA
Drinking Water Microbiology and Public
Health Workshop, to develop a
comprehensive list of all possible agents
of waterborne disease. The intent was to
list what were considered the most
important agents (or potential agents) of
waterborne disease. The Agency
recognizes that the Workshop
participants could have established
different lists of reasonable criteria for
selecting pathogens, and believes that
the ultimate decisions represent the best
(albeit sometimes subjective) judgment
of the panel. Nevertheless, the Agency
believes that the process for developing
the current CCL for microorganisms by
this group of nationally recognized
experts in the field of microbiology was
reasonable and credible.
EPA believes that regulations that are
currently in effect [Surface Water
Treatment Rule (SWTR), Total Coliform
Rule (TCR)) or are now under
development (e.g., Groundwnter
Disinfection Rule (GWDR), Enhanced
Surface Water Treatment Rule (ESWTR),
and Disinfection Byproducts
Regulations (DPBR)] will address a
number of the microorganisms that
commenters have suggested. Generally,
if a microorganism has not caused, or
not expected to cause, a waterborne
outbreak in the U.S., or if the organism
is known to be susceptible to
disinfection or filtration required by
current or upcoming regulations, the
organism has not been included on the
CCL,
Protozoa
Several commenters supported the
draft CCL, which included Toxoplasma
gondil, Cyclospora cayetanensis, and
two mlcrosporidia—Enterocytozoon and
Septata. One commenter suggested the
addition of Entamoeba hlstofytica to the
CCL, primarily because of its virulence.
One commenter suggested that EPA add
Isospora belli to the final CCL.
EPA Response
After further consideration, EPA has
decided to remove Toxoplasma and
Cyclospora from the final CCL.
Toxoplasma gondli is about the same
size as Giardia, and Cyclospora
cayetanensis is larger than
Cryptosporidium. The Agency believes
that the upcoming M/DBPR to control
Giardia and Cryptosporidium will also
control these larger organisms.
Microsporidia remains on the CCL for
the reasons indicated in the preamble to
the draft CCL, including the
ineffectiveness of chlorination and
filtration.
The Agency recognizes that
Entamoeba histolytica can be virulent.
Even though the commenter cites an
article stating that dogs and perhaps
pigs may be reservoirs for E. histolytica
(Benenson 1995), animals are probably
not major host reservoirs, in contrast to
the situation for Giardia and
Cryptosporidium. Thus, if sewage
treatment practices are adequate, the
potential for source water
contamination is probably low, as
suggested by the fact that the organism
has not caused a significant waterborne
disease outbreak since the early 1950s
(the one reported exception in the U.S.
was a small outbreak in 1984 associated
with untreated well water). Importantly,
the cyst is large (10-15nm). It is slightly
larger than a Giardia cyst, and much
larger than microsporidia spores that
infect humans (l-5nm) to which the
commenter compares E. histolytica.
Thus, EPA believes that regulations that
control for Giardia and Cryptosporidium
should also control E. histolytica. For
these reasons, E. histolytica was not
included on the final CCL. The Agency
has also decided not to include Isospora
belli for the reasons given in the
preamble of the draft CCL, especially for
the fact that its oocysts are 30x12(im,
larger than Giardia cysts, and any rule
to control Giardia and Cryptosporidium
should also control this organism.
Viruses
The draft CCL included the following
viruses: caliciviruses, adenoviruses,
coxsackieviruses, echoviruses, and the
hepatitis A virus. Several commenters
suggested that EPA add rotaviruses,
hepatitis E virus, and bacteriophage to
the final CCL.
EPA Response
The final CCL remains the same as the
draft, except that die hepatitis A virus
has been removed. Hepatitis A was
removed because it is being addressed
by current regulations, or regulations
under development. As a matter of
policy, all viruses are regulated as a
class under EPA's SWTR and are going
to be regulated as a class under the
GWDR, and the Agency does not believe
that additional research is needed to
demonstrate the efficacy of disinfection
for this organism. In contrast, the
Agency believes that additional research
is needed on the impact of treatment for
the other viruses that remain on the
CCL.
EPA did not include rotaviruses on
the final CCL, primarily because they
are vulnerable to disinfection and
should always be associated with fecal
contamination. Thus, the Agency
believes that EPA's SWTR, plus the
upcoming GWDR, should adequately
control these viruses.
EPA excluded the hepatitis E virus
from the final CCL because the Agency
does not regard the virus as a significant
public health threat in the U.S. and
believes that current sewage treatment
practices are sufficient to eliminate
significant risk of waterborne
transmission. EPA recognizes that
hepatitis E is a major problem in some
developing countries, especially for
pregnant women. However, there is no
evidence that the organism is a problem
in the U.S. Rare cases have occurred in
the U.S., usually among travelers
returning from an area where the
disease is endemic (Mast and
Krawczynski 1996). Structurally, the
organism is a small, single-stranded
RNA virus similar to the caliciviruses,
coxsackieviruses, and echoviruses, all of
which remain on the CCL, because of
evidence of outbreaks and occurrence in
finished waters.
Bacteriophage were excluded from the
CCL because they are not pathogenic to
humans. However, EPA recognizes that
they may be useful as an indicator of
fecal contamination. EPA has decided
not to include indicators of fecal
contamination or of pathogens on the
final CCL. However, the Agency will
consider indicators in the context of
regulations to control pathogens on the
CCL. For example, the Agency is
considering two bacteriophage—the
somatic coliphage and the male-specific
coliphage—as an indicator of fecal
contamination under the Groundwater
Disinfection Rule.
Bacteria
The draft CCL included the following
bacteria: Helicobacter pylori, Legionella,
Mycobacterium avium complex, and
Aeromonas hydrophila. Commenters
urged EPA to include additional
bacteria, including Pseudomonas
aeruginosa, Shigella, Salmonella,
Vibrio, Arcobacter, Campylobacter,
Yersinia, and E. coli O157:H7, and that
if these enteric bacterial pathogens were
not included on the CCL, then H. pylori
and A. hydrophila should not be
included either, because both are
sensitive to disinfection also.
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EPA Response
The final CCL does not include the
enteric bacterial pathogens that
commenters suggested EPA add
(Shigella, Salmonella, Vibrio,
Arcobacter, Campylobacter, Yersinia,
and E. coli O157:H7). The Agency's
reasons for excluding these organisms
are that they are all sensitive to
disinfection and are all associated with
fecal contamination. Thus, EPA regards
total coliforms as an adequate indicator
for these organisms. Moreover, the
SWTR requires all surface water systems
to disinfect, and the forthcoming GWDR
is likely to require systems that have
wells vulnerable to fecal contamination
to disinfect or provide other corrective
action. The Agency regards these
regulatory tools as sufficient to control
for the above pathogens.
With regard to P. aeruginosa, the
preamble to the draft CCL indicated that
the participants of the EPA Drinking
Water Microbiology and Public Health
Workshop could not agree on whether
to include this organism on the draft
CCL. There was controversy among
participants about its public health
significance and its potential health risk
via the waterborne route. Therefore,
participants recommended that EPA
conduct a complete literature search on
the topic before deciding whether to
include this organism on the final list.
The Agency has not yet completed this
search. Because of this lack of
information, EPA has decided to defer a
decision on P. aeruginosa and not
include it on the CCL. However, should
the literature search suggest that
regulatory action may be necessary, EPA
will increase the priority of research in
this area, if appropriate.
With regard to Helicobacter, following
the meeting of the panel, an article was
published indicating that Helicobacter
is sensitive to chlorine Qohnson, Rice
and Reasoner 1997). However, EPA
decided not to remove Helicobacter
from the CCL because of the large
number of people in the U.S. affected by
peptic ulcers (about 20 million people)
and gastritis, the poor survival rate of
individuals with gastric cancer, and
ignorance about the mode of
transmission of the organism.
Helicobacter pylori has been implicated
in the cause of these three diseases. The
Agency believes that, in spite of the
recent disinfection data, it would be
improper to remove Helicobacter from
the CCL for these reasons.
With'regard to Aeromonas
hydrophila, EPA recognizes that this
organism is sensitive to disinfection in
source and finished waters. However,
unlike the fecal pathogens listed above,
A. hydrophila may enter the distribution
system either as a result of inadequate
treatment or a break in the water
distribution system, and grow as part of
the biofilm on the pipes or in the
sediment, which may protect it from
disinfectants. In addition, A. hydrophila
is not necessarily associated with fecal
contamination. Thus, the total coliforms
rule may not be adequate as an indicator
for this organism. Moreover, systems
which are not required to disinfect (or
take other corrective action) under the
forthcoming Groundwater Disinfection
Rule because they are considered not
vulnerable to fecal contamination, may
still be vulnerable to A. hydrophila. For
these reasons, EPA does not believe that
this organism can be treated in the same
manner as E coliO157:H7 and other
fecal bacteria listed by the commenter.
Thus, the final CCL includes A.
hydrophila.
EPA removed Legionella in ground
water from the final CCL. It was
removed because: (1) the Agency
intends to address the control of this
organism under the Groundwater
Disinfection Rule, and (2) the Agency
does not believe that high priority
research is needed in this area to
regulate this organism.
Algae and Their Toxins
Several commenters strongly urged
EPA to add algae, especially the blue-
green algae, plus their toxins (e.g.,
mycotoxin) to the CCL. One commenter
suggested that Pfiesteria piscicida be
included on the final CCL, as well.
EPA Response
In the preamble to the draft CCL, EPA
stated that certain species of blue-green
algae produce toxins that could be
harmful if ingested at high enough
concentrations, but that algal control
was best handled through good
watershed management practices. The
Agency continues to regard this strategy
as reasonable. However, the Agency has
decided to add the algae and their
toxins to the final CCL because: (1)
pathogenic algae and their toxins are not
necessarily associated with fecal
contamination and thus may not be
effectively controlled by the SWTR or
ESWTR, and (2) some data suggest that
current treatment techniques may be
particularly inadequate in controlling
algal toxins. Placement of this group of
contaminants on the CCL will make
them a priority for research to determine
what triggers toxic algal growth in
source water and the effectiveness of
water treatment practices.
EPA is aware that Pfiesteria piscicida
has been implicated in adverse health
effects in humans. Apparently at least
13 researchers who worked with dilute
toxic cultures of this organism and 10
fishermen sustained mild to serious
health effects by water contact or by
inhaling toxic aerosols. Symptoms
include skin rashes, reddening of the
eyes, severe headaches, blurred vision,
nausea/vomiting, breathing difficulties,
kidney and liver problems, short-term
memory loss, confusion, and other
problems. The organism has a
complicated life cycle, with about 24
stages. Pfiesteria's habitat is estuarine or
brackish water. Current data indicate
that, like most other dinoflagellates, the
organism grows poorly in fresh water
and does not elaborate toxins in this
milieu, thus, there is no evidence that
Pfiesteria occurs or could occur in
drinking water. Moreover, the size
ranges from 5-450 Jim, with the
dormant cyst stages 7-60 urn in
diameter. Thus filtration that is effective
for removing Cryptosporidium (4-6 |0.m)
should be effective for removing
Pfiesteria. For these reasons, EPA
believes that Pfiesteria does not
represent a health threat in drinking
water systems, and thus did not include
Pfiesteria on the final CCL.
/. MTBE
A number of commenters agreed with
the inclusion of methyl-t-butyl ether
(MTBE) on the CCL, and some indicated
that MTBE should be included among
the contaminants for which
determinations will be made by 2001.
Another commenter suggested it should
not be included on the CCL but should
be included in the forthcoming
Unregulated Contaminant Monitoring
rulemaking, due in 1999.
EPA Response
The Agency agrees that MTBE should
remain on the CCL. However, as with all
the contaminants on the list, EPA has
not made a determination with respect
to regulating MTBE. Although there are
serious limitations in the MTBE data,
there is some evidence to support a
concern for potential human hazard.
MTBE has been found in some drinking
water wells but it is uncertain whether
the concentrations are at levels of health
concern. Given the potential health
hazard and need for additional data,
MTBE meets the criteria for placement
on the CCL.
The inclusion of a contaminant on the
CCL does not mean that the
contaminant will be regulated. As noted
earlier, contaminants on the CCL
include those for which the Agency
must make a determination of whether
or not to regulate by 2001 pursuant to
the requirements of the SDWA, but it
also includes the Agency's research
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priorities, contaminants for which
monitoring is necessary to gather
additional data. MTBE will remain on
the CCL since the Agency needs
additional occurrence data.
At this time, the EPA has not
included MTBE among the
contaminants for which determinations
will be made by 2001. As stated earlier,
MTBE needs additional health and
occurrence data, and as such, it will be
one of the priority contaminants for
which the Agency will gather such data.
There are no data on the effects on
humans of drinking MTBE
contaminated water. Therefore, EPA is
continuing to evaluate the available
health information and is doing
additional research to seek more
definitive estimates of potential risks to
humans from drinking water. One of the
mechanisms for gathering occurrence
data is to include a contaminant in the
forthcoming Unregulated Contaminant
Monitoring rulemaking to be issued in
August 1999. The Agency is also not
precluded from using other means of
gathering occurrence data which may
include conducting special studies. The
data collection and evaluation efforts
will assist in determining what the
appropriate action should be with
respect to MTBE. Placing MTBE in this
category does not prevent the Agency
from selecting it to make a
determination of whether or not to
regulate by 2001; however, at this time,
it Is not likely that the necessary data
will be collected and evaluated in time
to make a determination by this date.
To facilitate data collection and
evaluation efforts for MTBE, an Agency-
wide task force has been formed and has
prepared a draft Oxygenates in Water
Research Strategy. The Strategy
identifies current, or soon to be started,
research in areas that include
environmental occurrence, source
characterization, transport and
transformation, exposure, toxicity, and
treatment. The Strategy will also
Identify key areas of research that are
still necessary to build a stronger, more
informed scientific database to support
health risk assessment and risk
management decisions with respect to
fuel oxygenates, including MTBE.
On October 7,1997, 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. The information
produced in this workshop is being
used to help revise the draft of the
Strategy, which will serve as a blueprint
to assist In coordinating efforts by
various organizations, public and
private, in addressing the issues related
to oxygenates in water. The Agency will
also publish the Strategy in the Federal
Register this Spring, to seek additional
public comment on the research
priorities identified.
J. Organotins
Four commenters argued that
organotins, specifically the mono- and
di-organotins, the only types used as
polyvinyl-chloride (PVC) heat
stabilizers, should not be included on
the CCL. The commenters maintained
that, due to evidence of low toxicity and
low migration (thus, low risk to
consumers), mono- and di-organotins,
especially mono- and di-methyltins,
should not be of concern to drinking
water, particularly in light of the
National Sanitation Foundation (NSF)
certification program for plumbing
materials. Other commenters indicated
that it was premature for the Agency to
regulate organotins, but thought it
prudent that the Agency keep informed
of the issue.
EPA Response
EPA disagrees with the commenters
who suggest that organotins should be
deleted from the CCL. It should be
emphasized that retaining organotins on
the CCL does not necessarily mean that
they will be regulated. The Agency
believes that organotins, including
mono- and di-organotins which are used
as heat stabilizers in PVC and
chlorinated polyvinyl-chloride (CPVC)
pipes, are of sufficient concern to
warrant further investigation. The
Agency is aware of the NSF certification
program, and has noted that many
States require the use of NSF-certified
material in the construction of new
buildings. The Agency agrees with the
NDWAC Working Group
recommendation that an assessment of
the toxicological data underlying the
action levels established by the NSF
needs to be made along with assessment
of other available information on
organotins, before these compounds can
be disregarded as of concern. The
Agency requested this information from
the NSF, and learned that due to
confidentiality agreement, NSF cannot
disclose this information, therefore we
have not yet been able to assess the
toxicological data.
There are numerous concerns about
the occurrence and toxicological
significance of various species of
organotins in drinking water. A recent
report indicates that unlike PVC
systems, new CPVC systems have the
potential to contaminate drinking water
with organotin compounds for a longer
period of time after installation (Forsyth
and Jay 1997). There has been a report
concerning tributyltin contamination of
drinking water from PVC pipes, and
tributyltin is of far more toxicological
significance than mono- and di-
organotins (Sadiki et al, 1996). There is
also concern about the recent reports of
teratogenic potential of dibutyltin (Ema
et al, 1996). The Canadian Government
is concerned about organotin
contamination of drinking water and
has launched a national survey.
In view of these concerns, the Agency
believes that organotins, including
mono- and diorganotins, should remain
on the CCL until the Agency can
perform its own in-depth evaluation of
the occurrence and toxicological data of
the contaminants of this class.
K. Perchlorate
The majority of comments on
perchlorate indicated support for its
inclusion on the CCL. Commenters
pointed out that the information on the
occurrence of perchlorate in drinking
water supplies was sufficient to raise
concern over the potential impact on
public health. A few commenters
expressed concern that perchlorate
should not be regulated or that there
was not sufficient information at present
to warrant its regulation, and that a
health advisory would be more
appropriate.
EPA Response
The Agency agrees with commenters
that sufficient information exists to raise
concern over the potential health effects
and occurrence of perchlorate in
drinking water supplies. Despite
significant data gaps regarding health
effects, occurrence, and treatment
technologies, perchlorate has been
found in a number of drinking water
supplies at levels of health concern, and
as a result is included on the final CCL.
The Agency understands that the
extent of actual or even potential
perchlorate contamination is unclear for
many parts of the country, and that for
some areas of the country perchlorate
contamination may not be an issue.
However, perchlorate has been detected
in a number of drinking water supplies
to date and warrants further evaluation.
Placement of perchlorate on the CCL
means that the Agency will make it a
priority to conduct further investigation
and evaluation of the health effects and
national occurrence of perchlorate in
drinking water supplies.
Perchlorate has been placed in the
categories of needing additional health
effects, treatment research, and
occurrence information. Several
toxicological and occurrence studies are
planned or are underway, which will
assist the Agency in filling these data
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10283
gaps on perchlorate. At this time, the
Agency has not made a determination to
issue a health advisory or to regulate
perchlorate. The additional data
obtained from these health effects and
occurrence studies will provide a sound
scientific basis for future EPA decisions
of whether to regulate perchlorate or
not, to prepare a health advisory or
guidance, or to include perchlorate in
the Unregulated Contaminant
Monitoring rulemaking. Placing
perchlorate in these categories does not
preclude the Agency from selecting it to
make a determination of whether or not
to regulate by 2001, but at this time it
is unlikely that perchlorate will be
included among those for which
determinations will be made by 2001.
L. Rhodamine WT
A few commenters argued that
Rhodamine WT be removed from the
CCL. The commenters stated that
Rhodamine WT has a very specialized
purpose. They also noted that it is
certified by the NSF and that the
certification is reviewed by EPA. They
also stated that data for including
Rhodamine WT were questionable, and
that the contaminant had no specific
health effect.
EPA Response
EPA agrees with the commenters and
has removed Rhodamine WT from the
CCL. Rhodamine WT was placed on the
draft CCL because it was detected in
ground water above the NSF Standard
60 concentration of 0.1|j.g/L for drinking
water. However, three concentrations
have been established under the NSF
Standard 60; 0.1|4.g/L for drinking water,
10)J.g/L for water entering a drinking
water plant (prior to treatment and
distribution), and 100 ng/L for ground
water not associated with drinking
water production. These concentration
values were developed under the
Agency's former Additives Program
which was subsequently privatized and
turned over to NSF in the 1980's.
The maximum concentration of
available occurrence data was 28 \ig/L
detected in ground water, and, as such,
should be compared to the
recommended value of 100 |j.g/L for
ground water, not the value for drinking
water. Given this comparison, the
maximum concentration of 28 |ig/l is
well below the recommended value for
ground water of 100 |J.g/L. When the
NSF guidance regarding the use of
Rhodamine WT as a fluorescent tracer
in water flow studies is followed the
Agency does not anticipate any adverse
health effects resulting from the use of
Rhodamine WT.
M. Sodium
Many commenters were opposed to
including sodium on the CCL, primarily
due to their contention that sodium in
drinking water is not a public health
concern because of its extremely low
level in drinking water, and its small
contribution to overall sodium intake.
'Commenters also noted that controlling
sodium in public water systems would
be cost-prohibitive and produce
marginal or nonexistent health benefits.
Commenters argued that food, which is
the major source of sodium, is allowed
to average 440 mg/day under a "salt-
restricted" medically-supervised diet,
and that controlling sodium content in
food would address salt-restriction more
directly. Commenters also strongly
disagreed with the use of EPA's DWEL
of 20 mg/1 as the public health criteria
for determining whether to include
sodium on the CCL. The commenters
mentioned a more up-to-date, 1996
report published by the American
Medical Association (AMA) showing a
lack of association between sodium and
blood-pressure, except for older
individuals with existing hypertension.
Other commenters argued for the
inclusion of sodium, citing studies
linking it to hypertension and the need
to maximize protection of salt-sensitive
individuals as a sensitive
subpopulation.
EPA Response
The issue of sodium posed a unique
challenge for the Agency priority setting
and contaminant candidate listing
process. Information from commenters
on each side made important points. On
the one hand, high levels of salt intake
can be associated with hypertension in
some individuals. On the other hand,
sodium levels in drinking water are
unlikely to be a significant contribution
to adverse health effects.
This low level of concern is
compounded by the legitimate
criticisms of EPA's 20 mg/1 guidance
level that was used in this process. EPA
believes this guidance level for sodium
needs updating, and is probably low. If
a health benchmark for drinking water
were established using current
information and current drinking water
health assessment procedures, it would
likely be higher. This revision could
establish a new level at which sodium
occurrence would not meet the criteria
for inclusion on the CCL as a drinking
water contaminant of concern. There
was insufficient time to complete a
reassessment of the sodium guidance in
advance of the CCL issuance.
Given the state of the data, EPA faced
a dilemma on whether or not to list '
sodium. A decision not to list would be
justified by the fact that much is known
about sodium and it does not appear to
be a drinking water risk comparable to
other priority contaminants. In fact, this
was the logic supporting the decision
not to include sodium on the previous
drinking water priority list in 1991.
However, a decision to list sodium
would afford EPA the opportunity to
address the confusion surrounding the
current guidance for sodium in drinking
water.
In the end, EPA decided to include
sodium on the CCL, primarily as a
vehicle to reexamine and correct the
current, outdated guidance. Therefore,
sodium is listed, not as a Regulatory
Determinations Priority, but as a
Research Priority to allow time to
evaluate and revise the Agency
guidance. When this is completed, EPA
will reevaluate whether sodium merits
retention on the CCL for any further
action.
N. Triazines
Many commenters applauded EPA's
intention to address triazines and their
metabolites as a group a "good first
step" to addressing these compounds. A
number of commenters indicated that
we should include other triazine
degradation products such as
deisopropyl atrazine and
diaminochlorotriazine (same as diamino
atrazine) because they too are common
degradation products of atrazine as well
as simazine, and are found at higher
concentrations than atrazine-desethyl.
Once commenter expressed concern that
additional information was being
considered and evaluated by the Agency
under the OPP Special Review program,
and that these reviews should be
completed before triazines are
considered for the CCL.
EPA Response
The Agency agrees with the points
raised by the commenters regarding the
triazine degradation products. As a
result, the EPA has decided to include
triazines and their degradation products
(including but not limited to: cyanazine
and atrazine-desethyl) on the CCL as a
group to include all potential risks from
this class of compounds. Stakeholders,
through the regulatory reassessment
process in developing the redirection
strategy, and through the development
of this draft CCL, have requested that
the Agency address triazine pesticides
as a group, which includes all parent
and degradate compounds, as opposed
to each triazine as an individual
contaminant.
The EPA has been studying the
mechanism of carcinogenicity of this
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group of analogues along with their
degradation products, and will continue
to study these chemicals as a group to
characterize their risk in drinking water.
The Agency regulated atrazine in 1991
and simazine in 1992. The Agency may
ultimately develop regulations for the
mixtures of triazines either through the
revision of existing regulations or the
development of new ones.
EPA disagrees with the notion that
triazines should be excluded from the
CCL until after the completion of the
Special Reviews. The triazines are
Included in the Priority Group 1 of
pesticide tolerances that will be
examined first under the Food Quality
Protection Act (FQPA) tolerance
reassessment (62 FR 42020). The work
being accomplished by OPP in their
review efforts will certainly be factored
into EPA's decisions regarding triazines,
as with all pesticides on the CCL.
O. Zinc
Two commenters were opposed to the
inclusion of zinc on the CCL. The
commenters argued that zinc did not
meet the criteria for inclusion on the
CCL, and is generally non-toxic to
animals and humans. They pointed out
that zinc is used in a wide variety of
products, and is also an essential
element. One commenter stated that the
Agency had not considered zinc's
beneficial qualities when deciding
whether it should be included on the
CCL, and that the WHO and EPA have
both stated that deficiency of zinc is
more of a concern than over-exposure.
The commenter further argued that the
history of the substitution from the 1988
DWPL was not considered, and that the
HA value used in the Agency's analysis
was from a "7-yr old draft" which was
not available for comment and therefore
the explanation behind the Agency's
HAL of 2,000 ug/1 was not available for
comment.
EPA Response
The EPA agrees with the commenter
on the point raised that zinc does not
meet the criteria for inclusion on the
CCL, and has removed zinc from the
CCL. The Agency has determined that
the number of public water systems
with zinc levels above 1,000 ng/1 is 4,
and none had occurrence levels above
2,000 ug/1, and, as a result, zinc doesn't
meet the criteria for inclusion on the
CCL. The criterion for a contaminant to
be included on the CCL was
"occurrence at the health level of
concern In 10 or more small public
water systems." The action of removing
zinc from the CCL was due to its lack
of occurrence in water systems at health
levels of concern, not due to its lack of
toxicity. It is known that daily exposure
to zinc of approximately 60 mg/1 (60,000
ug/1) or more can effect copper
metabolism, and result in deleterious
health effects.
IV. Continuing Work in Preparation for
Future CCLs
In the Federal Register notice on the
draft CCL, the Agency deferred action
on a number of pesticides, and
contaminants implicated as endocrine
disrupters, in anticipation of impending
resolution specific to these two groups
of contaminants. Action on these
contaminants continues to be deferred
and these contaminants will be
reconsidered when the next CCL is
developed. The Agency is also resuming
work on a contaminant identification
process to be used in the development
of future CCLs. Further discussion of
these three topics follows.
A. Pesticides Deferred
In developing the CCL, the SDWA
requires EPA to consider substances
registered as pesticides under FIFRA.
During the development of the CCL, the
Agency's Office of Ground Water and
Drinking Water sought assistance from
OPP in determining what pesticides
should be priorities for the drinking
water program. In response to the
request, OPP provided
recommendations for a number of
pesticides based on physical-chemical
properties, occurrence and extent of use,
using the Ground Water (GW) Risk
score. The GW-Risk score is a calculated
potential of pesticides to leach to
ground water. Pesticides with a GW-
Risk of 2.0 or greater were included for
initial consideration in developing the
draft CCL.
However, later during the data
evaluation and screening phase of the
CCL development, the decision was
made to defer pesticides identified by
the GW-Risk of 2.0 or greater for which
no additional information was available.
Inclusion on the CCL would be deferred
pending further evaluation of the
potential of these pesticides to occur at
levels of health concern. The Agency is
working to develop a tool to estimate
concentrations in ground and surface
waters based on physical-chemical
properties and pesticide use volumes,
and will then compare the estimated
concentrations with health advisory
levels or calculated health levels based
on reference doses or cancer potency.
It was anticipated that the tool to
estimate concentrations of pesticides in
ground and surface waters would be
completed and available in time to
reevaluate the inclusion of the
additional pesticides prior to
completing the CCL. However, the
Agency believes it is important to have
this tool peer-reviewed prior to its use,
which would increase the time
necessary for its development beyond
the time available. Therefore, EPA did
not attempt to complete this work before
finalizing the CCL in today's notice. As
a result, action on these pesticides
remains deferred until the next CCL.
On December 10, 1997, the Science
Advisory Panel (SAP) met to discuss
drinking water exposure assessment
issues with the OPP. The objective of
the meeting was to obtain SAP's
recommendation on the approaches and
models developed by OPP to determine
short-term and long-term potential
exposures from pesticides in drinking
water. The issues of monitoring
requirements, and assessing impacts of
exposure to mixtures were also part of
the discussion. The approaches and
models developed by OPP and the
forthcoming SAP's recommendations on
these issues are of particular importance
to the Office of Water in that the
outcome will be used in the drinking
water program as well.
B. Endocrine Disrupters
During the development of the draft
CCL, the Agency initially considered,
then later deferred, a number of
contaminants implicated or suspected
as substances which disrupt the
function of the endocrine system. As
stated in the notice of the draft CCL,
EPA issued an interim assessment in
February 1997, pending a more
extensive review expected to be issued
by the National Academy of Sciences
(NAS), determining that, while effects
have been found in laboratory animal
studies, a causal relationship between
exposure to a specific environmental
agent and an adverse health effect in
humans operating via endocrine
disruption has not been established,
with a few exceptions. Further research
is needed before such effects can be
demonstrated.
Under the SDWA, as amended, the
Agency is also required to establish a
program to screen endocrine disrupting
contaminants. Additional authority to
assess endocrine disrupters is also
provided through the recently enacted
FQPA. EPA's Office of Prevention,
Pesticides, and Toxic Substances
(OPPTS) has the Agency lead on
endocrine disrupter screening and
testing issues, and is actively engaged in
research and regulatory initiatives to
respond to the growing scientific and
public concern over endocrine
disrupters. Also, the Endocrine
Disrupter Screening and Testing
Advisory Committee (EDSTAC) has
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10285
been established to provide advice and
counsel to the Agency in implementing
a screening and testing strategy required
under the FQPA and SDWA. EDSTAC
will complete its recommendations for a
screening and testing strategy by March
1998. The recommendations will be
peer-reviewed jointly by the SAB and
the FIFRA SAP.
As a result, pending completion of the
EDSTAC's recommendations and the
additional review of endocrine
disrupters by the NAS, EPA has not
included contaminants for inclusion on
this first CCL based solely on the
possibility of endocrine disruption
(although several contaminants
implicated as endocrine disrupters were
considered for other reasons). As stated
in the notice on the draft CCL, the
Agency will continue to follow this
issue closely and reconsider this
category of potential contaminants in
the development of future CCLs.
C. Development of the Contaminant
Selection Process
This CCL is largely based on
knowledge acquired over the last few
years and other readily available
information, but an enhanced, more
robust approach to data collection and
evaluation will be developed for future
CCLs. The Agency will also resume
work on the contaminant identification
and the contaminant selection process.
The CCL, and the identification and
selection process will serve as the
cornerstones of the Agency's regulatory
development process. In addition to
developing the CCL, and the
identification and selection process, the
Agency intends to obtain resources in
order to acquire better data and
information, improve analytical
capability, and seek additional
stakeholder involvement.
The next steps for improving the
contaminant identification and selection
process include an American Water
Works Association Research Foundation
(AWWARF) project utilizing a series of
workshops in which established
decision-making tools would be
employed to develop a process to
identify emerging pathogens of concern
for consideration, regulation, and future
research. The work is expected to begin
in June/July 1998. A project with the
NAS will also be undertaken to solicit
input ori criteria for listing and selecting
chemical contaminants for future CCLs.
A panel is currently being formed and
work is expected to begin in summer of
1998. The development of the
identification and the selection process
will be completed in consultation with
the NDWAC and the Working Group on
Occurrence & Contaminant Selection,
and their future involvement is likely to
include reviewing products from
AWWARF and NAS in 1999. The CCL
is a critical input to shaping the future
direction of the drinking water program,
and improvements to the process will be
made with each successive cycle of
publishing the list.
V. Data, Research Needs and Next Steps
Table 2 divides the CCL into
categories to represent the next steps
and data needs for each contaminant.
Sufficient data are needed to conduct
analyses on extent of exposure and risk
to populations via drinking water in
order to determine appropriate Agency
action (development of health
advisories, or regulations, or no action)
for many of these contaminants. If
sufficient data are not available, they
must be obtained before such an
assessment can be made. The data and
information required will be gathered by
research or monitoring programs, and
are not likely to be available for analyses
to be completed prior to 2001. Thus, the
contaminants for which sufficient data
exist at the time of publishing the CCL
are likely to be those from which the
determinations will be made by 2001.
However, it should be noted that the
groupings in Table 2 are based on
current information, and some
movement of contaminants between
categories can be expected as more
information is evaluated and analyzed.
The Regulatory Determination Priorities
category in Table 2 will be used to select
5 or more contaminants for which the
Agency must determine, by August
2001, whether or not regulations should
be developed. To make these
determinations, further analysis of data
currently available, or data that will
become available within a short period,
is required to prepare supporting
documents addressing health criteria,
cost and benefit assessments, and
analyses of analytical methods,
occurrence, and treatment technology
and feasibility. For contaminants in the
category, there may also be some short-
term research needs, such as bench-
scale treatability studies, that must also
be completed. The next steps for the
Agency regarding the contaminants in
this category are to determine which
contaminants to address first, and
outline plans of action to work towards
making determinations for five or more
by August 2001.
The contaminants in the Research
Priorities category have significant data
gaps in areas of health, treatment, or
analytical methods. For these
contaminants, the research, or data
gathering, and subsequent analysis
needed are not expected to be complete
within the SVa years, by August 2001, in
order to make determinations of
whether regulation of these
contaminants is necessary. These are
EPA's priority contaminants for research
and data gathering. Some of these
research needs are currently being
addressed by EPA or other agencies
(e.g., Department of Defense for
perchlorate), while other needs are
newly identified.
The contaminants in the Occurrence
Priorities category have significant data
gaps in occurrence data. The
Unregulated Contaminant Monitoring
Regulations (UCMR) will be the primary
source for data for most contaminants
included in this category; however,
some contaminants may be more
appropriate for special studies or
surveys, or joint data gathering efforts
with other Agencies. Also, for some
contaminants, suitable analytical
methods must be developed prior to
obtaining the occurrence data necessary.
The next steps for the Agency are to
develop short- and long-term research
plans on health, treatment, and
methods, to develop the UCMR proposal
(expected August 1998) for gathering
occurrence data, and to plan for special
occurrence studies, where appropriate.
The Agency will also use its FIFRA and
Toxic Substances Control Act (TSCA)
authorities, as appropriate, to conduct
studies and obtain data necessary for
decision-making.
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Federal Register/Vol. 63, No. 40/Monday, March 2, 1998/Notices
TABLE 2.—NEXT STEPS FOR THE CCL
Regulatory determination
priorities
Research priorities
Health research
Treatment research
Analytical methods
research
Occurrence priorities
Acanthamoeba (guidance)
1,1,2,2-tetrachloroe thane
1,1-dichloroethane
1,2,4-trimethylbenzene
1,3-dtchIoropropene
2,2-dichloropropane
Atdrin
Boron
Bromobenzene
Dicldrin
HoxQchlorobuladiono
p-lsopropyltoluene
Manganese
Motolachlor
Motribuzln
Naphthalene
Organotins
Trfazines & degradation
products (incl., but not
llmitod to Cyanazine and
alrazine-desolhyl)
Sulfate
Vanadium
Aeromonas hydrophila
Cyanobacteria (Blue-green
algae), other freshwater
algae, and their toxins
Calicivi ruses
Helicobacter pylori
Microsporidia
Mycobacterium avium
intercellulare (MAC)
1,1-dichloropropene
1,3-dichloropropane
Aluminum
DCPA mono-acid & di-acid
degradates
Methyl bromide
MTBE
Perchlorate
Sodium (guidance)
Adenoviruses
Aeromonas hydrophila
Cyanobacteria (Blue-green
algae), other freshwater
algae, and their toxins
Calicivi ruses
Coxsackieviruses (ICR
data)
Echoviruses (ICR data)
Helicobacter pylori
Microsporidia
Mycobacterium avium
intracellulare (MAC)
Aluminum
MTBE
Perchlorate
Adenoviruses
Cyanobacteria (Blue-green
algae), other freshwater
algae, and their toxins
Caliciviruses
Helicobacter pylori
Microsporidia
1,2-diphenylhydrazine
2,4,6-trichlorophenol
2,4-dichlorophenol
2,4-dinitrophenol
2-methyl-Phenol
Acetochlor
Alachlor ESA
Fonofos
Perchlorate
RDX
Adenoviruses.*
Aeromonas hydrophila.
Cyanobacteria (Blue-green
algae), other freshwater
algae, and their toxins.*
Caliciviruses.*
Coxsackieviruses (ICR
data).
Echoviruses (ICR data).
Helicobacter pylori.*
Microsporidia.*
1,2-diphenylhydrazine.*
2,4,6-trichlorophenol.*
2,4-dichlorophenol.*
2,4-dinitrophenol.*
2,4-dinitrotoluene.
2,6-dinitrotoluene.
2-methyi-phenol.*
Alachlor ESA* and
Acetochlor.*
DCPA mono-acid & di-acid
degradates.
DDE.
Diazinon.
Disulfoton.
Diuron.
EPTC.
Fonofos.*
Linuron.
Molinate.
MTBE.
Nitrobenzene.
Perchlorate.*
Prometon.
RDX.*
Terbacil.
Terbufos.
The groupings in Table 2 are based on current information, and some movement of contaminants between categories can be expected as
information is evaluated i '
more
I and analyzed. 'Suitable analytical methods must be developed prior to obtaining occurrence data.
VI, Other Requirements
The CCL is a notice and not a
regulatory action; therefore, the
following statutes and executive orders
are not applicable at this time: the
Regulatory Flexibility Act. Small
Business Regulatory Enforcement
Fairness Act, Paperwork Reduction Act,
Unfunded Mandates Reform Act; and
Executive Order 12866. For any
contaminants selected for rule-making,
all necessary analysis will be conducted
in accordance with the rule-making
process.
Executive Order 13045. Protection of
Children from Environmental Health
Risks and Safety Risks, requires that
Federal Agencies identify and assess
health risks and safety risks that
disproportionately affect children, and
ensure that its policies, programs,
activities, and standards address
disproportionate health and safety risks
to children. The SDWA also requires the
Agency to select priorities for regulation
while considering risks to sensitive
subpopulations, such as infants and
children.
The impact on sensitive populations
will be addressed in the contaminant
selection process, and will be a
component of the Agency's
determination of whether or not to
regulate a given contaminant. In
preparation for addressing the issues of
sensitive subpopulations, the Agency is
sponsoring several activities to
determine water intake by age group, by
demographic distribution, and by innate
or developed sensitivity to potential
drinking water contaminants. The
Agency is also collaborating with the
Center for Disease Control and
Prevention on a study of six major cities
to determine the most sensitive
populations for drinking water
manifested during major outbreaks of
illness from incidents of water. Other
research also is underway to determine
the extent of vulnerable populations
including children and the
immunologically impaired.
VII. References
Benenson, A.S. 1995. Control of
Communicable Diseases Manual (16th
ed.). pp. 10-13. American Public Health
Assoc., Washington.
Ema, M., R. Kurosaka, H. Amano, and Y.
Ogawa. 1996. Comparative
Developmental Toxicity of Di-, Tri-and
Tetrabutyltin Compounds after
Administration during Late
Organogenesis in Rats. J. Appl. Toxicol.,
16(1), 71-76.
Forsyth, D.S., and B. Jay. 1997. Organotin
Leachate in Drinking Water from
Chlorinated Polyvinyl Chloride (CPVC)
Pipe. Appl. Organometallic Chem.,
11:551-558.
Johnson, C.H., E.W. Rice and D.J. Reasoner.
1997. Inactivation of Helicobacter pylori
by chlorination. Appl. Environ.
Microbiol. 63:4969-4970.
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10287
Mast, E.E., and K. Krawczynski. 1996.
Hepatitis E: An Overview. Annual Rev.
Med. 47:257-266.
Midgley, J.P., A.G. Matthew, C.M.T.
Greenwood, and A.G. Logan. 1996. Effect
of Reduced Dietary Sodium on Blood
Pressure. J. Amer. Med. Assoc., 275 (20):
1590-1597.
RDA. 1989. Recommended Dietary
Allowances, tenth edition. National
Research Council, National Academy
Press, Washington, D.C., 284 pp.
Sadiki, Abdel-Iiah, D. Williams, R. Carrier
and B. Thomas. 1996. Pilot study of the
Contamination of Drinking Water by
Organotin Compounds from PCV
Materials. Chemosphere, 32:2389-2398.
U.S. EPA. 1995. "Acetone; Toxic Chemical
Release Reporting; Community Right-to-
Know, Final Rule," 60 FR No. 116,
31643-31646, June 16.
U.S. EPA. 1996. "Drinking Water Program
Redirection Strategy," Office of Water.
EPA 810-R-96-003, June.
U.S. EPA. 1997. "Announcement of the Draft
Drinking Water Contaminant Candidate
List; Notice," 62 FR No. 193 52194-
52219, October 6.
U.S. EPA. 1998. "Response to Comment
Document." Office of Ground Water and
Drinking Water.
(Authority: 42 U.S.C. 300f-300j-25)
Dated: February 6, 1998.
Robert Perciasepe,
Assistant Administrator, Office Water,
Environmental Protection Agency.
[FR Doc. 98-5313 Filed 2-27-98; 8:45 am)
BILLING CODE 6560-50-P
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