[Federal Register Volume 79, Number 202 (Monday, October 20, 2014)]
[Proposed Rules]
[Pages 62715-62750]
[FR Doc No: 2014-24582]

Vol. 79

Monday,

No. 202

October 20, 2014

Part II

Environmental Protection Agency

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40 CFR Part 141

Announcement of Preliminary Regulatory Determinations for Contaminants
on the Third Drinking Water Contaminant Candidate List; Proposed Rule

Federal Register / Vol. 79 , No. 202 / Monday, October 20, 2014 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 141

[EPA-HQ-OW-2012-0155; FRL-9917-87-OW]

Announcement of Preliminary Regulatory Determinations for
Contaminants on the Third Drinking Water Contaminant Candidate List

AGENCY: Environmental Protection Agency (EPA).

ACTION: Request for public comment.

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SUMMARY: The Safe Drinking Water Act (SDWA), as amended in 1996,
requires the Environmental Protection Agency (EPA) to make regulatory
determinations every five years on at least five unregulated
contaminants. A regulatory determination is a decision about whether or
not to begin the process to propose and promulgate a national primary
drinking water regulation (NPDWR) for an unregulated contaminant. These
unregulated contaminants are chosen from the Contaminant Candidate List
(CCL), which SDWA requires the agency to publish every five years. EPA
published the third CCL (CCL 3) in the Federal Register on October 8,
2009. This notice presents the preliminary regulatory determinations
and supporting rationale for 5 of the 116 contaminants listed on CCL 3.
The agency is making preliminary determinations to regulate one
contaminant (i.e., strontium) and to not regulate four contaminants
(i.e., 1,3-dinitrobenzene, dimethoate, terbufos and terbufos sulfone).
EPA seeks comment on these preliminary determinations.

DATES: Comments must be received on or before December 19, 2014, 60
days after publication in the Federal Register.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2012-0155, by one of the following methods:
     www.regulations.gov: Follow the online instructions for
submitting comments.
     Mail: Water Docket, Environmental Protection Agency,
Mailcode: [28221T], 1200 Pennsylvania Ave. NW., Washington, DC 20460.
     Hand Delivery: EPA Docket Center, [EPA/DC] EPA West, Room
3334, 1301 Constitution Ave. NW., Washington, DC. Such deliveries are
only accepted during the Docket's normal hours of operation, and
special arrangements should be made for deliveries of boxed
information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2012-
0155. EPA's policy is that all comments received will be included in
the public docket without change and may be made available online at
www.regulations.gov, including any personal information provided,
unless the comment includes information claimed to be Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. Do not submit information that you consider to
be CBI or otherwise protected through www.regulations.gov. The
www.regulations.gov Web site is an ``anonymous access'' system, which
means EPA will not know your identity or contact information unless you
provide it in the body of your comment. If you send an email comment
directly to EPA without going through www.regulations.gov your email
address will be automatically captured and included as part of the
comment that is placed in the public docket and made available on the
Internet. If you submit an electronic comment, EPA recommends that you
include your name and other contact information in the body of your
comment and with any disk or CD-ROM you submit. 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. Electronic
files should avoid the use of special characters, any form of
encryption, and be free of any defects or viruses. For additional
information about EPA's public docket visit the EPA Docket Center
homepage at http://www.epa.gov/epahome/dockets.htm. For additional
instructions on submitting comments, go to Section I.B of the
SUPPLEMENTARY INFORMATION section of this document.
    Docket: All documents in the docket are listed in the
www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in www.regulations.gov or in hard copy at the Water Docket, EPA/DC, EPA
West, Room 3334, 1301 Constitution Ave. NW., Washington, DC. The 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<PHONE_NUMBER>, and the telephone number for the Water
Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: Zeno Bain, Standards and Risk
Management Division, Office of Ground Water and Drinking Water, Office
of Water (Mailcode 4607M), Environmental Protection Agency, 1200
Pennsylvania Ave. NW., Washington, DC 20460; telephone number: (202)
564-5970; email address<EMAIL_ADDRESS>For general information,
contact the Safe Drinking Water Hotline, telephone number: (800) 426-
4791. The Safe Drinking Water Hotline is open Monday through Friday,
excluding legal holidays, from 10 a.m. to 4 p.m. Eastern time.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this action apply to me?

    Neither these preliminary regulatory determinations nor the final
regulatory determinations, when published, impose any requirements on
anyone. Instead, this action notifies interested parties of EPA's
preliminary regulatory determinations for five unregulated contaminants
for comment.

B. Tips for Preparing Your Comments

    When submitting comments, remember to:
     Identify the rulemaking by docket number and other
identifying information (subject heading, Federal Register date and
page number).
     Explain why you agree or disagree and suggest
alternatives.
     Describe any assumptions and provide any technical
information and/or data that you used.
     Provide specific examples to illustrate your concerns, and
suggest alternatives.
     Explain your views as clearly as possible.
     Make sure to submit your comments by the comment period
deadline identified.

                   Abbreviations Used in This Document
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           Abbreviation                            Meaning
------------------------------------------------------------------------
[mu]g/L...........................  Micrograms per liter.
ADAF..............................  Age Dependent Adjustment Factor.
AM................................  Assessment Monitoring.
AMWA..............................  Association of Metropolitan Water
                                     Agencies.
ATSDR.............................  Agency For Toxic Substances And
                                     Disease Registry.
AWWA..............................  American Water Works Association.
BATs..............................  Best Available Technologies.

BMD...............................  Benchmark Dose.
BMDL..............................  Benchmark Dose (95% Lower Confidence
                                     Bound).
BW................................  Body Weight.
CARC..............................  Cancer Assessment Peer Review
                                     Committee.
CAS...............................  Chemical Abstracts Service.
CASRN.............................  Chemical Abstract Service Registry
                                     Number.
CBI...............................  Confidential Business Information.
CCL...............................  Contaminant Candidate List.
CCL 1.............................  First Contaminant Candidate List.
CCL 2.............................  Second Contaminant Candidate List.
CCL 3.............................  Third Contaminant Candidate List.
CCR...............................  Consumer Confidence Report.
CFR...............................  Code of Federal Regulations.
ChE...............................  Cholinesterase.
CMR...............................  Chemical Monitoring Reform.
CSF...............................  Cancer Slope Factor.
CUSIUR............................  Chemical Update System/Inventory
                                     Update Rule.
cVOC..............................  Carcinogenic Volatile Organic
                                     Compounds.
CW................................  Concentration in Water.
CWS...............................  Community Water System.
CWSS..............................  Community Water System Survey.
DBP...............................  Disinfection Byproduct.
DBP ICR...........................  Disinfection Byproduct Information
                                     Collection Rule.
DDE...............................  1,1-Dichloro-2,2-bis(p-
                                     chlorophenyl)ethylene.
DSMRT.............................  Distribution System Maximum
                                     Residence Time.
DWI...............................  Drinking Water Intake.
DWS...............................  Drinking Water Strategy.
EFSA..............................  European Food Safety Authority.
ELCD..............................  Electrolytic Conductivity Detection.
EPA...............................  Environmental Protection Agency.
EPCRA.............................  Emergency Planning And Community
                                     Right-To-Know Act.
EPTC..............................  S-Ethyl propylthiocarbamate.
EPTDS.............................  Entry Point to the Distribution
                                     System.
ESA...............................  Ethanesulfonic Acid.
EWG...............................  Environmental Working Group.
F.................................  Fraction of a 70 year lifetime
                                     applicable to the age period.
FFQ...............................  Food Frequency Questionnaire.
FIFRA.............................  Federal Insecticide, Fungicide, And
                                     Rodenticide Act.
FR................................  Federal Register.
GAC...............................  Granular Activated Carbon.
GAO...............................  Government Accountability Office.
GC................................  Gas Chromatography.
GW................................  Ground Water.
HA................................  Health Advisory.
HRL...............................  Health Reference Level.
ICR...............................  Information Collection Rule.
IOC...............................  Inorganic Compound.
IREDs.............................  Interim Eligibility Decisions.
IRIS..............................  Integrated Risk Information System.
Kg................................  Kilogram.
LOAEL.............................  Lowest Observed Adverse Effect
                                     Level.
MCLG..............................  Maximum Contaminant Level Goal.
MDL...............................  Method Detection Limit.
mg/L..............................  Milligrams per liter.
mg/kg/day.........................  Milligrams per kilogram per day.
MDBP..............................  Microbial Disinfection Byproduct.
MOA...............................  Mode of Action.
MRL...............................  Minimum Reporting Limit.
MS................................  Mass Spectrometry.
MTBE..............................  Methyl Tertiary Butyl Ether.
NAS...............................  National Academy of Sciences.
NAWQA.............................  National Water Quality Assessment.
NCFAP.............................  National Center for Food and
                                     Agricultural Policy.
NCI...............................  National Cancer Institute.
NCOD..............................  National Drinking Water Contaminant
                                     Occurrence Database.
NDBA..............................  N-Nitroso-di-n-butylamine.
NDEA..............................  N-Nitrosodiethylamine.
NDMA..............................  N-Nitrosodimethylamine.
NDPA..............................  N-Nitroso-di-n-propylamine.
NDPhA.............................  N-Nitrosodiphenylamine.
NDWAC.............................  National Drinking Water Advisory
                                     Council.
NIRS..............................  National Inorganics And
                                     Radionuclides Survey.
NMEA..............................  N-Nitrosomethylethylamine.
NOAEL.............................  No Observed Adverse Effect Level.
NPDES.............................  National Pollutant Discharge
                                     Elimination System.
NPDWR.............................  National Primary Drinking Water
                                     Regulation.
NPYR..............................  N-Nitrosopyrrolidine.
NRC...............................  National Research Council.
NREC..............................  National Reconnaissance of Emerging
                                     Contaminants.
NTP...............................  National Toxicology Program.
OA................................  Oxanilic Acid.
OPP...............................  Office of Pesticides Program.
OW................................  Office of Water.
PCCL..............................  Preliminary Contaminant Candidate
                                     List.
PCE...............................  Tetrachloroethylene.
PDP...............................  Pesticide Data Program.
PFOA..............................  Perfluorooctanoic Acid.
PFOS..............................  Perfluorooctanesulfonic Acid.
PHA...............................  Provisional Health Advisory.
PID...............................  Photoionization Detection.
PMP...............................  Pesticide Monitoring Program.
PWS...............................  Public Water System.
QA................................  Quality Assurance.
RD 1..............................  Regulatory Determinations 1.
RD 2..............................  Regulatory Determinations 2.
RD 3..............................  Regulatory Determinations 3.
RED...............................  Reregistration Eligibility Decision.
RfD...............................  Reference Dose.
RL................................  Reporting Limit.
RSC...............................  Relative Source Contribution.
SAP...............................  Scientific Advisory Panel.
SDWA..............................  Safe Drinking Water Act.
SEPW..............................  U.S. Senate Committee on Environment
                                     and Public Works.
SS................................  Screening Survey.
SSCTs.............................  Small System Compliance
                                     Technologies.
STORET............................  Storage And Retrieval (STORET) Data
                                     System.
SW................................  Surface Water.
SY................................  Six Year Review.
SY3...............................  Six Year Review 3.
TCE...............................  Trichloroethylene.
TPTH..............................  Triphenyltin Hydroxide.
TRED..............................  Tolerance Reassessment Progress And
                                     Risk Management Decision.
TRI...............................  Toxic Release Inventory.
TT................................  Treatment Technique.
UCM...............................  Unregulated Contaminant Monitoring.
UCMR 1............................  First Unregulated Contaminant
                                     Monitoring Regulation.
UCMR 2............................  Second Unregulated Contaminant
                                     Monitoring Regulation.
UCMR 3............................  Third Unregulated Contaminant
                                     Monitoring Regulation.
UF................................  Uncertainty Factor.
USDA..............................  United States Department of
                                     Agriculture.
USGS..............................  United States Geological Survey.
VOC...............................  Volatile Organic Compound.
WHO...............................  World Health Organization.
------------------------------------------------------------------------

Table of Contents

I. General Information
    A. Does this action apply to me?
    B. Tips for Preparing Your Comments
II. Purpose and Background
    A. What is the purpose of this action?
    B. Background on the CCL and Regulatory Determinations
    1. Statutory Requirements for CCL and Regulatory Determinations
    2. The First Contaminant Candidate List (CCL 1) and Regulatory
Determinations (RD 1)

    3. The Second Contaminant Candidate List (CCL 2) and Regulatory
Determinations (RD 2)
    4. The Third Contaminant Candidate List (CCL 3) and Regulatory
Determinations (RD 3)
    5. The Drinking Water Strategy
    6. Outreach for RD 3 (Stakeholder Meeting and Expert Review)
III. Approach and Overall Outcome for RD 3
    A. Summary of the Approach and Overall Outcome for RD 3
    1. Phase 1 (Data Availability Phase)
    2. Phase 2 (Data Evaluation Phase)
    3. Phase 3 (Regulatory Determination Assessment Phase)
    B. Supporting Documentation for EPA's Preliminary Determinations
    C. Analyses Used To Support the Preliminary Regulatory
Determinations
    1. Evaluation of Adverse Health Effects
    2. Evaluation of Contaminant Occurrence and Exposure
IV. Contaminant-Specific Discussions for the RD 3 Preliminary
Regulatory Determinations
    A. Summary of the Preliminary Regulatory Determination
    B. Contaminant Profiles
    1. Dimethoate
    2. 1,3-Dinitrobenzene
    3. Strontium
    4-5. Terbufos and Terbufos Sulfone
V. What is the status of the agency's evaluation of chlorate and the
nitrosamines?
VI. What about the remaining CCL 3 contaminants?
VII. EPA's Next Steps
VIII. References
    Appendix: HRL Derivation with Age-Related Exposure Factors

II. Purpose and Background

    This section briefly summarizes the purpose of this action, the
statutory requirements, and previous activities related to the CCL and
regulatory determinations.

A. What is the purpose of this action?

    The purpose of this action is to present and request comment on
EPA's preliminary regulatory determinations for five unregulated
contaminants. The five contaminants include: Dimethoate, 1,3-
dinitrobenzene, strontium, terbufos, and terbufos sulfone. The agency
is making preliminary determinations to regulate one contaminant
(strontium) and to not regulate the remaining four contaminants
(dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone). EPA
seeks comment on these preliminary determinations. The agency is also
presenting and requesting comment on the process used for this round of
regulatory determinations (i.e., RD 3), the supporting information, and
the rationale used to make these preliminary decisions.

B. Background on the CCL and Regulatory Determinations

    1. Statutory Requirements for CCL and Regulatory Determinations.
Section 1412(b)(1)(B)(i) of the 1996 Safe Drinking Water Act Amendments
(SDWA) requires EPA to publish the CCL every five years. The CCL is a
list of contaminants which are not subject to any proposed or
promulgated national primary drinking water regulations (NPDWRs), are
known or anticipated to occur in public water systems (PWSs), and may
require regulation under SDWA. SDWA section 1412(b)(1)(B)(ii) directs
EPA to determine whether to regulate at least five contaminants from
the CCL every five years. For EPA to make a determination to regulate a
contaminant, SDWA requires the Administrator to determine that:
    (a) The contaminant may have an adverse effect on the health of
persons;
    (b) the contaminant is known to occur or there is substantial
likelihood that the contaminant will occur in public water systems with
a frequency and at levels of public health concern; and
    (c) in the sole judgment of the Administrator, regulation of such
contaminant presents a meaningful opportunity for health risk reduction
for persons served by public water systems.
    If EPA determines that these three statutory criteria are met and
makes a final determination to regulate a contaminant, the agency has
24 months to publish a proposed Maximum Contaminant Level Goal \1\
(MCLG) and NPDWR.\2\ After the proposal, the agency has 18 months to
publish and promulgate a final MCLG and NPDWR (SDWA section
1412(b)(1)(E)).\3\
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    \1\ The MCLG is the ``maximum level of a contaminant in drinking
water at which no known or anticipated adverse effect on the health
of persons would occur, and which allows an adequate margin of
safety. Maximum contaminant level goals are non-enforceable health
goals.'' (40 CFR 141.2; 42 U.S.C. 300g-1)
    \2\ An NPDWR is a legally enforceable standard that applies to
public water systems. An NPDWR sets a legal limit (called a maximum
contaminant level or MCL) or specifies a certain treatment technique
(TT) for public water systems for a specific contaminant or group of
contaminants. The MCL is the highest level of a contaminant that is
allowed in drinking water and is set as close to the MCLG as
feasible using the best available treatment technology and taking
cost into consideration.
    \3\ The statute authorizes a nine month extension of this
promulgation date.
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    2. The First Contaminant Candidate List (CCL 1) and Regulatory
Determinations (RD 1). EPA published the final CCL 1, which contained
60 chemical and microbiological contaminants, in the Federal Register
(FR) on March 2, 1998 (63 FR 10273; USEPA, 1998). The agency made and
published the final regulatory determinations for 9 of the 60 CCL 1
contaminants in the FR on July 18, 2003. The agency determined that
NPDWRs were not necessary for any of these nine contaminants:
Acanthamoeba, aldrin, dieldrin, hexachlorobutadiene, manganese,
metribuzin, naphthalene, sodium, and sulfate (68 FR 42898; USEPA,
2003a). The agency posted information about Acanthamoeba \4\ on the EPA
Web site and issued health advisories \5\ for manganese, sodium, and
sulfate.
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    \4\ Consumer information about Acanthamoeba for people who wear
contact lenses can be found at http://water.epa.gov/action/advisories/acanthamoeba/index.cfm.
    \5\ The health advisories for CCL 1 can be found at http://water.epa.gov/drink/standards/hascience.cfm.
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    3. The Second Contaminant Candidate List (CCL 2) and Regulatory
Determinations (RD 2). The agency published the final CCL 2 in the FR
on February 24, 2005, (70 FR 9071; USEPA, 2005a) and carried forward
the 51 remaining chemical and microbial contaminants listed on CCL 1.
The agency made and published the final regulatory determinations for
11 of the 51 CCL 2 contaminants in the FR on July 30, 2008. The agency
determined that NPDWRs were not necessary for any of these 11
contaminants: boron, the dacthal mono- and di-acid degradates, 1,1-
dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), 1,3-dichloropropene
(Telone), 2,4-dinitrotoluene, 2,6-dinitrotoluene, s-ethyl
propylthiocarbamate (EPTC), fonofos, terbacil, and 1,1,2,2-
tetrachloroethane (73 FR 44251; USEPA, 2008a). The agency issued new or
updated health advisories \6\ for boron, dacthal degradates, 2,4-
dinitrotoluene, 2,6-dinitrotoluene and 1,1,2,2-tetrachloroethane.
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    \6\ The health advisories for CCL 2 can be found at http://water.epa.gov/drink/standards/hascience.cfm.
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    4. The Third Contaminant Candidate List (CCL 3) and Regulatory
Determinations (RD 3). The agency published the final CCL 3, which
listed 116 contaminants, in the FR on October 8, 2009 (74 FR 51850;
USEPA, 2009a). In developing CCL 3, EPA improved and built upon the
process that was used for CCL 1 and CCL 2. The new CCL 3 process was
based on substantial expert input and recommendations from the National
Academy of Science's (NAS) National Research Council (NRC) and the
National Drinking Water Advisory Council (NDWAC) as well as input from
the public. Based on these consultations and input, EPA developed a
multi-step process to select candidates for the final

CCL 3, which included the following key steps:
    (a) Identification of a broad universe of ~7,500 potential drinking
water contaminants (the CCL 3 Universe);
    (b) screening the CCL 3 Universe to a preliminary CCL (PCCL) of
~600 contaminants based on the potential to occur in PWSs and the
potential for public health concern; and
    (c) evaluation of the PCCL contaminants based on a more detailed
review of the occurrence and health effects data to identify a final
list of 116 CCL 3 contaminants.
    The development of the CCL, regulatory determinations, and any
subsequent rulemaking should be viewed as a progression where each
process builds upon the previous process, including the collection of
data and analyses conducted. The agency's improvements in developing
CCL 3 provide an excellent foundation for RD 3 by enhancing EPA's
ability to identify contaminants of concern for drinking water.
    While this notice focuses on the preliminary regulatory
determinations for 5 of the 116 CCL 3 contaminants, it is important to
note that the agency made and published a final determination to
regulate one CCL 3 contaminant, perchlorate, on February 11, 2011 (76
FR 7762; USEPA, 2011a). Additional information about CCL 3 and the
perchlorate final determination can be found in the October 8, 2009 (74
FR 51850; USEPA, 2009a) and February 11, 2011 (76 FR 7762; USEPA,
2011a) Federal Register notices, respectively. Sections III and IV in
this notice provide more detailed information about the approach and
outcome used for RD 3 and the contaminant-specific regulatory
determinations.
    5. The Drinking Water Strategy. In March 2010, EPA announced the
agency's new Drinking Water Strategy (DWS),\7\ which is aimed at
finding ways to strengthen the protection of public health from
contaminants in drinking water. The new vision is intended to
streamline decision-making, expand protection under existing laws, and
promote cost-effective new technologies to meet the needs of rural,
urban, and other water-stressed communities. The four principles
underlying the DWS are:
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    \7\ More information about the DWS can be found at
water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/.
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    (a) Address contaminants as groups rather than one at a time so
that enhancement of drinking water protection can be achieved cost-
effectively.
    (b) Foster development of new drinking water technologies to
address health risks posed by a broad array of contaminants.
    (c) Use the authority of multiple statutes to help protect drinking
water.
    (d) Partner with States to develop shared access to all PWSs
monitoring data.
    The first principle (i.e., addressing contaminants as groups) has a
direct bearing on RD 3 and how to designate the contaminants for
analysis, determination and subsequent regulation; that is, should they
be considered individually or as a group. Although the agency has
previously regulated contaminants as groups (e.g., total
trihalomethanes, total haloacetic acids, gross alpha radionuclides,
gross beta and photon emitters, etc.), all of the determinations for RD
1 and RD 2 were made on individual contaminants. As part of the DWS,
the agency identified several factors to evaluate which contaminants
might effectively be regulated as a group and considered these factors
in evaluating contaminant groups for RD 3. All the factors do not have
to be met, but the more factors that are met, the more suitable it may
be to regulate the contaminants as a group. These factors include
whether the contaminants in the group:
    (a) Have a similar health endpoint,
    (b) can be measured by the same analytical methods,
    (c) can be treated using the same technology or treatment technique
approach and/or
    (d) have been shown to occur individually (and possibly co-occur if
data are available).
    EPA conducted extensive national outreach to solicit input from
stakeholders on the DWS and how best to address groups of contaminants.
Stakeholders generally agreed that while public health protection is of
paramount importance, the grouping factors previously listed were some
of the other important factors to consider in evaluating which
contaminants would work best in a group regulation. Several CCL 3
contaminants (as well as non-CCL 3 contaminants) belong to contaminant
groups that underwent consideration for regulation during the RD 3
process.
    In February 2011,\8\ the agency decided to address carcinogenic
volatile organic compounds (cVOCs) as a group in a separate and
concurrent regulatory process (which the agency expects to release in
late 2014). Some of the cVOCs being considered include unregulated
cVOCs listed on CCL 3 (e.g., 1,2,3-trichloropropane). While the cVOC
group is being evaluated in a separate regulatory process, the same
factors used to group cVOCs (i.e., similar health endpoint, measured by
the same analytical method, similar treatment technique approach, etc.)
were used to evaluate groups of contaminants for RD 3 as well (e.g.,
nitrosamines, chloroacetanilides, etc.). Although EPA evaluated the
nitrosamines and chloroacetanilides groups as part of the RD 3 process,
in the end, EPA decided not to make any preliminary determinations for
these groups under RD 3.
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    \8\ http://water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/.
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    The SDWA requires EPA to review each existing NPDWR at least once
every six years and revise them, if appropriate. The purpose of the
review, called the Six Year Review (SY), is to identify those NPDWRs
for which current health effects assessments, changes in technology,
and/or other factors provide a health or technical basis to support a
regulatory revision that will maintain or provide for greater
protection of the health of persons. In contrast, the RD process is
intended to address currently unregulated contaminants. The agency will
review the existing Microbial Disinfection Byproduct (MDBP) regulations
as part of the third Six Year Review (SY3). Because chlorate and
nitrosamines are disinfection byproducts (DBPs) that can be introduced
or formed in public water systems partly because of disinfection
practices, the agency believes it is important to evaluate these
unregulated DBPs in the context of the review of the existing DBP
regulations. DBPs need to be evaluated collectively, because the
potential exists that the chemical disinfection used to control a
specific DBP could affect the concentrations of other DBPs. Therefore,
the agency is not making a regulatory determination for chlorate and
nitrosamines at this time. The agency expects to complete the review of
these DBPs by the end of 2015.
    6. Outreach for RD 3 (Stakeholder Meetings and Expert Review).
    EPA sought external advice and expert input for RD 3 by convening
two public stakeholder meetings and conducting an Expert Review panel.
On March 3, 2011, EPA held an Environmental Justice (EJ) Stakeholder
meeting in Washington, DC to solicit input on RD 3 and environmental
justice issues. Approximately 90 stakeholders participated (either by
phone or in person) including representatives of children's advocacy
groups, environmental organizations, community action groups, the
drinking water industry, and State drinking water and public health
programs. Stakeholders did not identify any EJ

issues specific to RD 3. On June 16, 2011, EPA held another public
Stakeholder Meeting in Washington, DC, to disseminate information on
the progress of RD 3 and solicit input from stakeholders, the public,
and other interested groups. Forty-six participants attended including
representatives from States, environmental and public health
organizations, drinking water systems, chemical manufacturers, local
governments, and academia. EPA presented and discussed: (a) The
approach used to narrow the contaminants listed on CCL 3 and identify
potential candidates for RD 3 (with a focus on those occurring at
levels of health concern in drinking water) and (b) the background,
health, and occurrence information for a ``short list'' of 32 \9\
contaminants being evaluated as potential RD 3 candidates. Stakeholders
asked questions and provided comments about the approach as well as the
health and occurrence information presented on several contaminants.
One stakeholder provided additional health information on the
chloroacetanilides and submitted a letter requesting that EPA regulate
these compounds with an NPDWR (USEPA, 2011b). A summary of the June 16,
2011, meeting is provided in the docket for this action (USEPA, 2011c).
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    \9\ Subsequent to the June 2011 stakeholder meeting and before
the October 2011 Expert Review, EPA identified two additional
contaminants for the shortlist, bringing the total to 34. In
response to the Expert Review comments, an additional contaminant
was added to the short list, bringing the final total to 35 CCL 3
contaminants.
---------------------------------------------------------------------------

    In May 2011, the Government Accountability Office (GAO) released a
report entitled, ``EPA Should Improve Implementation of Requirements on
Whether to Regulate Additional Contaminants'' (GAO, 2011). Specifically
for regulatory determinations, GAO recommended that the agency develop
criteria to identify contaminants of greatest public health concern and
be more transparent, clear, and consistent by developing policies/
guidance to interpret the SDWA criteria and make determinations (i.e.,
include thresholds for positive findings, factors for determining
adequacy of occurrence/health data to make determinations, an approach
for evaluating health effects on sensitive subpopulations, a process
for presenting key information in documents, etc). In response to
questions regarding the GAO report at a July 2011 U.S. Senate Committee
on Environment and Public Works (SEPW) hearing,\10\ EPA committed to
consulting with an independent panel of scientists on the RD 3 process
to determine how SDWA criteria 1 and 2 are evaluated,\11\ how the best
available science is used to make decisions, how the contaminants of
greatest public health risk are assessed, and how vulnerable
populations (especially children) are considered. EPA also committed to
making the process used for regulatory determinations publicly
available and to review the process every five years as EPA conducts
the regulatory determination cycle.
---------------------------------------------------------------------------

    \10\ The U.S. Senate Committee on Environment and Public Works
full committee hearing, entitled ``Oversight Hearing on the
Environmental Protection Agency's Implementation of the Safe
Drinking Water Act's Unregulated Drinking Water Contaminants
Program'' can be found at (http://www.epw.senate.gov/public/index.cfm?FuseAction=Hearings.Hearing&Hearing_ID=fc5a8756-802a-23ad-454a-b9eeb7bf1c36).
    \11\ Under the statute, SDWA criterion 3 of Section
1412(b)(1)(A) is solely the Administrator's decision.
---------------------------------------------------------------------------

    To implement the commitment, EPA convened a panel of experts in
October 2011 to provide an independent review of the approach used for
RD 3, which EPA described in a draft of the document entitled,
``Protocol for the Regulatory Determinations 3'' (USEPA, 2014a). The
Expert Review panel included seven experts representing one or more of
the following areas of expertise: health effects evaluation, drinking
water occurrence/exposure information evaluation, State drinking water
perspective, PWS perspective, and/or some familiarity with the RD 3
process (including the Contaminant Candidate List). The review involved
a three-week paper review of the October 2011 Draft RD 3 Protocol
document and an in-person meeting held in Washington DC, on October 26
and 27, 2011. Panel members were encouraged to provide comments as
individuals based upon their expertise and background, not as
representatives of any respective organizational affiliation. The
information and input provided by the expert reviewers assisted the
agency in revising and clarifying the approach used for the RD 3
process. A summary of the October 26-27, 2011, meeting and the expert
reviewers' comments (USEPA, 2011d), as well as the protocol document
(USEPA, 2014a), are provided in the docket for this action.

III. Approach and Overall Outcome for RD 3

    This section describes (a) the approach EPA uses to identify and
evaluate contaminants for the agency's third round of Regulatory
Determinations (RD 3) along with the overall outcome of applying this
approach, (b) the supporting RD 3 documentation, and (c) the technical
analyses and sources of health and occurrence information.

A. Summary of the Approach and Overall Outcome for RD 3

    The three phases of the RD 3 Process are (1) the Data Availability
Phase, (2) the Data Evaluation Phase, and (3) the Regulatory
Determination Assessment Phase. Figure 1 provides a brief overview of
the process EPA uses to identify which CCL 3 contaminants are
candidates for regulatory determinations and the SDWA statutory
criteria considered in making the regulatory determinations. For more
detailed information on the three phases of the RD 3 process please
refer to the ``Protocol for the Regulatory Determinations 3'' (USEPA,
2014a).

[GRAPHIC] [TIFF OMITTED] TP20OC14.000

1. Phase 1 (Data Availability Phase)
    In Phase 1, the Data Availability Phase, the agency identifies
contaminants that may have sufficient health and occurrence data to
proceed to Phase 2 and be listed on a ``short list'' for further
evaluation. With regard to sufficient health effects data used to
identify potential adverse health effect(s), the agency considers
whether a peer-reviewed health risk assessment is available or in
process from one of the following sources: (a) The agency's Integrated
Risk Information System (IRIS); (b) the agency's Office of Water (OW);
(c) the agency's Office of Pesticide Programs (OPP); (d) the National
Academy of Sciences (NAS); (e) the Agency for Toxic Substances and
Disease Registry (ATSDR); and/or (f) the World Health Organization
(WHO). For a non-EPA health assessment (i.e., NAS, ATSDR, WHO) to be
utilized for regulatory determinations, the health assessment must use
comparable methods, standards, and guidelines to an EPA health
assessment. If a health assessment is not available from one of these
sources, then the contaminant is not considered for RD 3.
    In regard to sufficient occurrence data, the agency considers the
availability of nationally representative finished water data and
whether other finished water data are available that indicate known
and/or likely occurrence in PWSs. Occurrence data from the following
sources, administered or overseen by EPA, is considered nationally
representative: (a) The Second Unregulated Contaminant Monitoring
Regulation (UCMR 2); (b) the First Unregulated Contaminant Monitoring
Regulation (UCMR 1) Assessment Monitoring; (c) the Unregulated
Contaminant Monitoring (UCM) program; and/or (d) the National
Inorganics and Radionuclides Survey (NIRS).
    If nationally representative data are not available, EPA identifies
and evaluates other finished water data, which may include other
national assessments as well as regional, State, and more localized
finished water assessments. These other national finished water data
include assessments that are geographically distributed across the
nation but not intended to be statistically representative of the
nation. These other finished water data include the following sources
for consideration in the regulatory determination process: (a) Finished
water assessments for Federal agencies (e.g., EPA and the United States
Geological Survey (USGS)); \12\ (b) state-level finished water
monitoring data; (c) research performed by institutions and
universities (e.g., scientific literature); and/or (d) other
supplemental finished water monitoring surveys (e.g., Pesticide
Monitoring Program (PMP), National Reconnaissance of Emerging
Contaminants (NREC), and other targeted surveys or localized State/
Federal monitoring surveys).
---------------------------------------------------------------------------

    \12\ These may be assessments that are geographically
distributed across the nation but not intended to be statistically
representative of the nation. Examples include EPA's Disinfection By
Product Information Collection Request and various USGS water
quality surveys.
---------------------------------------------------------------------------

    EPA prefers to have nationally representative data available when
making regulatory determinations but may also use these other sources
of finished water occurrence data to evaluate the contaminant and
determine if there is ``substantial likelihood that the contaminant
will occur in PWSs with a frequency and at levels of public health
concern.'' If there is sufficient occurrence in these other finished
water data sources, EPA uses this information to address the
occurrence-related aspects of the statutory criteria when deciding to
regulate a contaminant. However, it is difficult to determine that a
contaminant is not occurring or not likely to occur based on these
other sources of finished water data because the data are limited in
scope and the contaminant could be occurring in other parts of the
country that were not monitored.
    EPA also considers the availability of analytical methods for
monitoring, and whether the contaminant is part of a contaminant group
based on factors defined by the Drinking Water Strategy

(DWS) (see section II.B.5). After conducting the health and occurrence
data availability assessments, the agency identifies those contaminants
and contaminant groups that meet the following Phase 1 data
availability criteria:
    (a) A peer-reviewed health assessment is available or in process,
and
    (b) A widely available analytical method for monitoring is
available, and
    (c) Either nationally representative finished water occurrence data
are available, or other finished water occurrence data shows occurrence
at levels >\1/2\ CCL 3 health reference level (HRL).\13\
---------------------------------------------------------------------------

    \13\ See section III.C for a discussion about how EPA derives an
HRL. EPA developed the CCL 3 HRLs using the most recent health data
available during the CCL 3 process. EPA uses \1/2\ CCL 3 HRL as a
conservative value to identify contaminants with potential
occurrence of concern during Phase 1 of the RD process. The CCL 3
HRLs for the 116 contaminants can be found at (http://water.epa.gov/scitech/drinkingwater/dws/ccl/upload/Final-CCL-3-Contaminant-Information-Sheets.pdf). After updating, completing and peer-
reviewing health assessments as necessary, the final HRL used for RD
3 may be different than the CCL 3 HRL.
---------------------------------------------------------------------------

    If a contaminant meets these three criteria, it is placed on a
``short list'' and proceeds to Phase 2. EPA also evaluated whether the
contaminant could be considered as part of a group using the DWS
factors discussed earlier in section II.B.5. After evaluating the 116
CCL 3 contaminants in Phase 1, the agency identified 35 CCL 3
contaminants and two non-CCL 3 contaminants (listed in Table 1) to
evaluate further in Phase 2. The non-CCL 3 contaminants were included
because they are part of a larger group (nitrosamines) that also
includes a number of CCL 3 contaminants.

                            Table 1--Contaminants Proceeding From Phase 1 to Phase 2
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
1, 1, 1, 2-Tetrachloroethane 1 3............  Metolachlor oxanilic acid (OA).1 3
1, 2, 3-Trichloropropane 1 3................  Molinate.\1\
1, 3-Dinitrobenzene \1\.....................  Molybdenum.\1\
1, 4-Dioxane \2\............................  Nitrobenzene.1 3
Acephate \2\................................  N-Nitroso-di-n-butylamine (NDBA).1 3 5
Acetochlor 1 3..............................  N-Nitrosodiethylamine (NDEA).1 3
Acetochlor ethanesulfonic acid (ESA) 1 3....  N-Nitrosodimethylamine (NDMA).1 3
Acetochlor oxanilic acid (OA) 1 3...........  N-Nitroso-di-n-propylamine (NDPA).1 3
Alachlor ethanesulfonic acid (ESA) 1 3......  N-Nitrosodiphenylamine (NDPhA).\3\
Alachlor oxanilic acid (OA) 1 3.............  N-Nitrosomethylethylamine (NMEA).1 3 5
Chlorate \2\................................  N-Nitrosopyrrolidine (NPYR).1 3
Cobalt \1\..................................  Perfluorooctanesulfonic acid (PFOS).\2\
Dimethoate \1\..............................  Perfluorooctanoic acid (PFOA).\2\
Disulfoton \4\..............................  RDX.\1\
Diuron \4\..................................  Strontium.\1\
Methyl bromide (Bromomethane) \1\...........  Terbufos.2 3
Methyl tert-butyl ether \1\.................  Terbufos sulfone.1 3
Metolachlor 1 3.............................  Vanadium.\1\
Metolachlor ethanesulfonic acid (ESA) 1 3...  ..................................................................
----------------------------------------------------------------------------------------------------------------
\1\ Has nationally representative finished water data and available or in process health assessment.
\2\ Has other finished water data (occurrence at levels >\1/2\ CCL 3 HRL) and available or in process health
  assessment.
\3\ Component of a contaminant group and will be further evaluated in Phase 2.
\4\ One exception to the criterion of having available nationally representative drinking water data applies to
  contaminants monitored in the UCMR 1 Screening Survey (SS). As noted in section 5, the UCMR 1 SS is a
  statistically defined, national sample of 300 PWSs. Because this survey only includes 300 systems, the agency
  identified and compiled additional supplemental data to compliment the UCMR 1 SS data for these contaminants
  that proceed to Phase 2 for further evaluation.
\5\ A non-CCL 3 contaminant that is part of the nitrosamine group.

    The remaining 81 CCL 3 contaminants (listed in Table 2) did not
meet either or both of the Phase 1 data availability criteria above and
were not considered further for RD 3.

                          Table 2--Contaminants Not Proceeding From Phase 1 to Phase 2
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
Has nationally representative finished water data but no health assessment
----------------------------------------------------------------------------------------------------------------
1,1-Dichloroethane...........................  Halon 1011 (Bromochloromethane).
3-Hydroxycarbofuran..........................  n-Propylbenzene.
Chloromethane (Methyl chloride)..............  sec-Butylbenzene.
Germanium....................................  Tellurium.
----------------------------------------------------------------------------------------------------------------
Has available or in process health assessment and other finished drinking water data but no occurrence at levels
 \1/2\ CCL 3 HRL
----------------------------------------------------------------------------------------------------------------
1-Butanol....................................  Formaldehyde.
Acrolein.....................................  Methamidophos.
alpha-Hexachlorocyclohexane..................  Oxydemeton-methyl.
Bensulide....................................  Oxyfluorfen.
Benzyl chloride..............................  Permethrin.
Captan.......................................  Profenofos.

Dicrotophos..................................  Tebuconazole.
Ethoprop.....................................  Tribufos.
Ethylene glycol..............................  Vinclozolin.
Ethylene thiourea (Maneb)....................  Ziram.
Fenamiphos...................................  .................................................................
----------------------------------------------------------------------------------------------------------------
Has other finished drinking water data but no health assessment
----------------------------------------------------------------------------------------------------------------
17-alpha-Estradiol...........................  Estriol.
Acetaldehyde.................................  Estrone.
Aniline......................................  Ethinyl Estradiol (17-alpha-ethynyl estradiol).
Butylated hydroxyanisole.....................  HCFC-22.
Cyanotoxins (Anatoxin-a, Cylindrospermopsin,   Hexane.
 Microcystin-LR).
Equilenin....................................  Mestranol.
Equilin......................................  Norethindrone (19-Norethisterone).
Erythromycin.................................  Naegleria fowleri.*
Estradiol (17-beta-Estradiol)................  .................................................................
----------------------------------------------------------------------------------------------------------------
Does not have nationally representative or other finished water data
----------------------------------------------------------------------------------------------------------------
1,3-Butadiene................................  Quinoline.
2-Methoxyethanol.............................  Tebufenozide.
2-Propen-1-ol................................  Thiodicarb.
4,4'-Methylenedianiline......................  Thiophanate-methyl.
Acetamide....................................  Toluene diisocyanate.
Clethodim....................................  Triethylamine.
Cumene hydroperoxide.........................  Triphenyltin hydroxide (TPTH).
Dimethipin...................................  Urethane.
Ethylene oxide...............................  Campylobacter jejuni.
Hydrazine....................................  Escherichia coli (0157).
Methanol.....................................  Helicobacter pylori.
Nitroglycerin................................  Hepatitis A virus.
N-Methyl-2-pyrrolidone.......................  Salmonella enteric.
o-Toluidine..................................  Shigella sonnei.
Oxirane, methyl-.............................  .................................................................
----------------------------------------------------------------------------------------------------------------
Does not have a widely available analytical method for occurrence monitoring
----------------------------------------------------------------------------------------------------------------
Adenovirus...................................  Legionella pneumophila.
Caliciviruses................................  Mycobacterium avium.
Enterovirus..................................  .................................................................
----------------------------------------------------------------------------------------------------------------
Not within scope of this RD 3 since regulatory determination made in February 2011
----------------------------------------------------------------------------------------------------------------
Perchlorate..................................  .................................................................
----------------------------------------------------------------------------------------------------------------
* Does not have a widely available analytical method for occurrence monitoring.

2. Phase 2 (Data Evaluation Phase)
    Contaminants that meet the minimum health and occurrence data
availability requirements in Phase 1 are advanced to the Phase 2
evaluation. In addition to health and occurrence information data
assessed in Phase 1, the agency collects additional health and
occurrence data and more thoroughly evaluates this information to
identify a list of contaminants that should proceed to Phase 3. The
agency uses the following steps to develop this list: (a) Derive a
draft HRL \14\ (See section III.C) for each contaminant, (b) compare
all occurrence data against the draft HRL (along with the analytical
method minimum reporting limit (MRL)), (c) identify contaminants that
occur at levels and frequencies of public health concern, and (d)
identify contaminants that have no or low occurrence at levels of
public health concern.
---------------------------------------------------------------------------

    \14\ HRLs are not final determinations about the level of a
contaminant in drinking water that is necessary to protect any
particular population and are derived prior to development of a
complete exposure assessment. HRLs are risk derived concentrations
against which to evaluate the occurrence data to determine if
contaminants occur at levels of potential public health concern.
---------------------------------------------------------------------------

    Using the available health effects assessments, the agency derives
a draft HRL and then evaluates this HRL value (along with the
analytical method MRL), against the concentration values compiled for
the nationally representative or other finished water occurrence
information identified in Phase 1. The agency also gathers additional
occurrence data and information on monitoring in ambient or source
water (relative to the draft HRL and the analytical method MRL),
production, use, release to the environment, and persistence and
mobility. In Phase 2, the agency specifically focuses its efforts to
identify those contaminants or contaminant groups that are occurring or
have substantial likelihood to occur at levels and frequencies of
public health concern. To identify such contaminants, the agency
considers the following information:
    (a) How many samples (# and %) have detections > draft HRL and \1/
2\ draft HRL in the nationally representative and other finished water
occurrence data?
    (b) How many systems (# and %) have detections > draft HRL and \1/
2\ draft HRL in the nationally representative and other finished water
occurrence data? and
    (c) Is the contaminant associated with a contaminant group that is
of public

health concern and is being considered as part of the DWS? \15\
---------------------------------------------------------------------------

    \15\ Carcinogenic Volatile Organic Compounds (including 1,2,3-
trichloropropane) are being evaluated in a separate regulatory
effort.
---------------------------------------------------------------------------

    (d) Are there uncertainties or limitations with the data and/or
analyses, such as the age of the dataset, limitation of the detection
limit (i.e., MRL > draft HRL) and/or representativeness of the data
(e.g., limited to a specific region) that may cause misestimation of
occurrence in finished water at levels and frequency of public health
concern?
    After identifying contaminants that are occurring at levels and
frequencies of public health concern to proceed to Phase 3, the agency
evaluates the remaining contaminants on the ``short list'' to determine
which contaminants have no or low occurrence at levels of health
concern that could also proceed to Phase 3 by considering the following
factors:
    (a) Does the contaminant have nationally representative finished
water data showing no or low # or % of detections > draft HRL? \16\
---------------------------------------------------------------------------

    \16\ Note that the non-national data tend to be limited in scope
and EPA does not use these data alone to support a determination
that the contaminant is not or is not substantially likely to
``occur in PWSs with a frequency and at levels of public health
concern,'' which would therefore be a decision ``not to regulate''
(i.e., negative determination).
---------------------------------------------------------------------------

    (b) If a contaminant has other finished water data in addition to
nationally representative finished water data, does it support no or
low potential for occurrence in drinking water?
    (c) Does additional occurrence information of known quality support
low or no occurrence or potential for occurrence in drinking water? For
example, is the occurrence in ambient/source water at levels below the
draft HRL? Are releases to the environment or use/production decreasing
over time?
    (d) There are no critical information/data gaps after evaluating
the available health or occurrence data; and
    (e) The contaminant is not included or evaluated with a group of
contaminants based on the factors defined by the DWS.
    After evaluating these factors and whether a contaminant appears to
have sufficient data to evaluate the statutory criteria for regulatory
determination, the agency determines if the contaminant should proceed
to Phase 3. After evaluating the ``short list'' contaminants (listed in
Table 1), the agency identified 10 CCL 3 contaminants and 2 non-CCL 3
contaminants (listed in Table 3) that were within one of the following
Phase 2 data evaluation categories to proceed to Phase 3:
    (a) A contaminant or part of a contaminant group occurring or
likely to occur at levels and frequencies of public health concern, or
    (b) A contaminant not occurring or likely to occur at levels and
frequencies of public health concern and no data gaps.

                            Table 3--Contaminants Proceeding From Phase 2 to Phase 3
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
Chlorate 1 3.................................  N-Nitrosodiethylamine (NDEA).\1\
Dimethoate \2\...............................  N-Nitrosomethylethylamine (NMEA).1 4
1,3-Dinitrobenzene \2\.......................  N-Nitrosopyrrolidine (NPYR).\1\
N-Nitroso-di-n-butylamine (NDBA) 1 4.........  Strontium.1 3
N-Nitrosodimethylamine (NDMA) \1\............  Terbufos.\2\
N-Nitroso-di-n-propylamine (NDPA) \1\........  Terbufos Sulfone.\2\
----------------------------------------------------------------------------------------------------------------
\1\ A contaminant or part of a contaminant group occurring or likely to occur at levels and frequencies of
  public health concern.
\2\ A contaminant not occurring or likely to occur at levels and frequencies of public health concern and no
  data gaps.
\3\ The UCMR 3 includes sampling at both the entry point to the distribution system (EPTDS) and distribution
  system maximum residence time (DSMRT) for this contaminant (77 FR 26071, May 2, 2012). For some contaminants,
  including disinfection byproducts and inorganics, occurrence values may differ between the EPTDS and the DSMRT
  due to dynamics within the distribution system such as contaminant degradation, formation, accumulation and
  release.
\4\ A non-CCL 3 contaminant that is part of the nitrosamine group.

    Note that the agency does not have a threshold or a bright line for
occurrence in drinking water that triggers whether a contaminant is of
public health concern. There are a number of factors to consider in
developing thresholds, some of which include the health effect(s), the
potency of the contaminant, the level at which the contaminant is found
in drinking water, how frequently the contaminant is found, the
geographic distribution (national, regional, or local occurrence),
other possible sources of exposure, and potential impacts on sensitive
populations or lifestages, etc. Given the many possible combinations of
factors and the constantly evolving science, EPA believes it is better
to analyze each contaminant and characterize and present the best
available information that helps identify whether the occurrence of a
contaminant is of public health concern. In the end, the determination
of whether there is a meaningful opportunity for health risk reduction
by regulation of a contaminant in drinking water is a highly
contaminant-specific one that takes into consideration a large number
of factors.
    The remaining 25 CCL 3 contaminants (listed in Table 4) did not
proceed to Phase 3 and were not considered for RD 3 because of one or
more of the following critical health, occurrence, and/or other data
gaps:
    (a) An updated health assessment is needed, but was not completed
by fall 2011;
    (b) A health assessment is in process, but was not completed by
fall 2011;
    (c) Critical health effects gap (e.g., lack of data to support
quantification for the oral route of exposure);
    (d) Lacked nationally representative occurrence data;
    (e) Insufficient other finished water occurrence data to
demonstrate occurrence at levels and frequencies of public health
concern (although it may have some levels of public health concern);
    (f) Individual contaminants that were part of a group but lacked a
widely available analytical method for occurrence monitoring; and
    (g) Critical occurrence data gap (e.g., inconsistent results and/or
trends in occurrence data, significant uncertainty in occurrence
analyses and/or data).
    Table 4 identifies the health, occurrence, and/or other data gaps
that prevented the following 25 contaminants from moving forward for RD
3. The agency continues to conduct research, collect information or
find other avenues to fill the data and information gaps identified in
Table 4.

                                  Table 4--Data and Rationale Summary of the 25 Contaminants Not Proceeding to Phase 3
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Occurrence data
           No.                    Contaminant           Health data available          available                            Rationale
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................  1,4-Dioxane................  Yes....................  No \1\.................  Occurrence data gaps (no nationally
                                                                                representative finished water data or
                                                                                sufficient other finished water data).
2.......................  Acephate...................  Yes....................  No.....................  Occurrence data gaps (no nationally
                                                                                representative finished water data or
                                                                                sufficient other finished water data).
3.......................  Acetochlor.................  No.....................  Yes....................  Health data gap (no health assessment for the
                                                                                degradates) and no detections in nationally
                                                                                representative finished water data.
4.......................  Acetochlor ethanesulfonic    No.....................  Yes....................  Health data gap (no health assessment for the
                           acid (ESA).                                                                    ESA degradate) and no or low detections based
                                                                                on nationally representative finished water
                                                                                data.
5.......................  Acetochlor oxanilic acid     No.....................  Yes....................  Health data gap (no health assessment for the
                           (OA).                                                                          OA degradate) and no or low detections based
                                                                                on nationally representative finished water
                                                                                data.
6.......................  Alachlor ethanesulfonic      No.....................  Yes....................  Health data gap (no health assessment for the
                           acid (ESA).                                                                    ESA degradate) and no or low detections based
                                                                                on nationally representative finished water
                                                                                data.
7.......................  Alachlor oxanilic acid (OA)  No.....................  Yes....................  Health data gap (no health assessment for the
                                                                                OA degradate) and no or low detections based
                                                                                on nationally representative finished water
                                                                                data.
8.......................  Cobalt.....................  No.....................  Yes \2\................  Health data gap (health assessment not updated
                                                                                by fall 2011) and no detections in nationally
                                                                                representative or other finished water data at
                                                                                levels of public health concern.
9.......................  Disulfoton.................  Yes....................  No.....................  Occurrence data gap (no nationally
                                                                                representative finished water data and no
                                                                                detections in other finished water data).
10......................  Diuron.....................  Yes....................  No.....................  Occurrence data gap (no nationally
                                                                                representative finished water data and no
                                                                                detections in other finished water data).
11......................  Methyl Bromide.............  No.....................  Yes \1\................  Health data gap (health assessment not updated
                                                                                by fall 2011).
12......................  Methyl tert-butyl ether....  No.....................  Yes....................  Health data gap (IRIS health assessment not
                                                                                completed by fall 2011) and no or low
                                                                                detections based on nationally representative
                                                                                finished water data.
13......................  Metolachlor................  No.....................  Yes....................  Health data gap (no health assessment for
                                                                                degradates) and few detections in nationally
                                                                                representative finished water data.
14......................  Metolachlor ethanesulfonic   No.....................  Yes....................  Health data gap (no health assessment for ESA
                           acid (ESA).                                                                    degradate) and no or low detections based on
                                                                                nationally representative finished water data.
15......................  Metolachlor oxanilic acid    No.....................  Yes....................  Health data gap (no health assessment for OA
                           (OA).                                                                          degradate) and no or low detections based on
                                                                                nationally representative finished water data.
16......................  Molinate...................  No.....................  Yes....................  Health data gap (OPP health assessment not
                                                                                completed by fall 2011 due to cancellation of
                                                                                molinate) and no detections in nationally
                                                                                representative or other finished water data at
                                                                                levels of public health concern.
17......................  Molybdenum.................  No.....................  Yes....................  Health data gap (health assessment not updated
                                                                                by fall 2011) and no detections in nationally
                                                                                representative or other finished water data at
                                                                                levels of public health concern.
18......................  N-Nitrosodiphenylamine       Yes....................  No.....................  Health data gap (health assessment not updated
                           (NDPhA).                                                                       by fall 2011) and occurrence data gaps (no EPA
                                                                                approved analytical method for monitoring).
19......................  Perfluorooctanesulfonic      No.....................  No \1\.................  Health data gap (health assessment not
                           acid (PFOS).                                                                   completed by fall 2011) and occurrence data
                                                                                gaps (limited other finished water data
                                                                                available).
20......................  Perfluorooctanoic acid       No.....................  No \1\.................  Health data gap (health assessment not
                           (PFOA).                                                                        completed by fall 2011) and occurrence data
                                                                                gaps (limited other finished water data
                                                                                available).
21......................  RDX........................  No.....................  Yes....................  Health data gap (IRIS health assessment not
                                                                                updated by fall 2011) and no detections in
                                                                                nationally representative or other finished
                                                                                water data at levels of public health concern.
22......................  Vanadium...................  No.....................  Yes \2\................  Health data gap (health assessment not updated
                                                                                by fall 2011) and no to low detections in
                                                                                nationally representative finished water data
                                                                                at levels of public health concern.
23......................  1,1,1,2-Tetrachloroethane..  .......................  .......................  Will be evaluated and considered for the
                                                                                Carcinogenic Volatile Organic Compounds
                                                                                (cVOCs) group rule addressed in a separate
                                                                                process.
24......................  1,2,3-Trichloropropane.....  .......................  (\1\)..................  Will be evaluated and considered for the
                                                                                Carcinogenic Volatile Organic Compounds
                                                                                (cVOCs) group rule addressed in a separate
                                                                                process.

25......................  Nitrobenzene...............  .......................  .......................  Will be evaluated and considered for the
                                                                                Carcinogenic Volatile Organic Compounds
                                                                                (cVOCs) group rule addressed in a separate
                                                                                process.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ The UCMR 3 includes sampling at the EPTDS for this contaminant (77 FR 26071, May 2, 2012).
\2\ The UCMR 3 includes sampling at both the EPTDS and DSMRT for this contaminant (77 FR 26071, May 2, 2012). For some contaminants, including
  disinfection byproducts and inorganics, occurrence values may differ between the EPTDS and the DSMRT due to dynamics within the distribution system
  such as contaminant degradation, formation, accumulation and release.

3. Phase 3 (Regulatory Determination Assessment Phase)
    Phase 3, the Regulatory Determination Assessments Phase, involves a
complete evaluation of the statutory criteria for each contaminant or
group of contaminants that proceed from Phase 2 and have sufficient
information and data for making a regulatory determination. In this
phase, the agency evaluates the following statutory criteria:
    (a) Statutory Criterion #1--The contaminant may have an adverse
effect on the health of persons. To evaluate statutory criterion #1,
EPA completes any health assessment that needs to be updated and
externally peer-reviewed, and derives a final HRL. The derivation of
the final HRL, further described in the section III.C.1, Evaluation of
Adverse Health Effects, takes into account many of the key elements
that are considered when evaluating criterion #1, which includes the
mode of action, the critical health effect(s), the dose-response for
critical health effect(s), impacts on sensitive populations(s) or
lifestages, the RfD, and/or the cancer slope factor. HRLs are not final
determinations about the level of a contaminant in drinking water that
must not be exceeded to protect any particular population and are
derived prior to the development of a complete exposure assessment.
HRLs are risk derived concentrations against which to evaluate the
occurrence data to determine if contaminants may occur at levels of
potential public health concern. With this information, EPA determines
whether the contaminant ``may have an adverse effect.'' While CCL 3
contaminants are generally expected to meet statutory criterion #1
because their adverse health effects were analyzed as part of the
determination to list them on the CCL, the availability of a final HRL
is derived as part of the first statutory criterion and is necessary to
evaluate the second statutory criterion.
    (b) Statutory Criterion #2--The contaminant is known to occur or
there is a substantial likelihood that the contaminant will occur in
public water systems with a frequency and at levels of public health
concern. EPA compares the occurrence data for each contaminant to the
final peer-reviewed HRL to determine if the contaminant occurs at a
frequency and levels of public health concern. The types of occurrence
data used at this stage are described in section III.C.2, Evaluation of
Contaminant Occurrence and Exposure. The agency considers the following
factors when identifying contaminants or contaminant groups that are
occurring at frequencies and levels of public health concern:
     How many samples (# and %) have detections > final HRL in
the nationally representative and other finished water occurrence data?
     How many systems (# and %) have detections > final HRL in
the nationally representative and other finished water occurrence data?
     Is the contaminant associated with a contaminant group
that is of public health concern and is being considered as part of the
DWS?
     Is the geographic distribution of the contaminant
occurrence national, regional, or localized?
     In addition to the number of systems, what type of systems
does the contaminant occur in? Does the contaminant occur in large or
small systems? Does the contaminant occur in surface or ground water
systems?
     Are there significant uncertainties or limitations with
the data and/or analyses, such as the age of the dataset, limitation of
the detection limit (i.e., MRL > final HRL) and/or representativeness
of the data (e.g., limited in scope to a specific region)?
    Additional, less important factors that the agency considers when
identifying contaminants or contaminant groups that are of public
health concern also include:
     How many samples (# and %) have detections >\1/2\ final
HRL \17\ in the nationally representative and other finished water
occurrence data?
---------------------------------------------------------------------------

    \17\ Note that the \1/2\ HRL threshold is based on a
recommendation from the NDWAC working grouping that provided
recommendations on the first regulatory determinations effort.
(USEPA, 2000b)
---------------------------------------------------------------------------

     How many systems (# and %) have detections >\1/2\ final
HRL in the nationally representative and other finished water
occurrence data?
     How many samples (# and %) have detections > final HRL and
\1/2\ final HRL in the ambient/source water occurrence data?
     How many monitoring sites (# and %) have detections >
final HRL and \1/2\ final HRL in the ambient/source water occurrence
data?
     Are production and use trends for the contaminant
increasing or decreasing?
     How many pounds are discharged annually to surface water
and/or released to the environment?
     Do the environmental fate and transport parameters
indicate that the contaminant would persist and/or be mobile in water?
     Are there other uncertainties or limitations with the data
and/or analyses for these additional factors that should be considered?
     Is the contaminant introduced by water treatment processes
(e.g., disinfection byproducts)?
    If a contaminant is known to occur or substantially likely to occur
at a frequency and level of health concern in public water systems
based on the factors listed above, then the agency answers ``yes'' to
the second statutory criterion.
    (c) Statutory Criterion #3--In the sole judgment of the
Administrator, regulation of the contaminant presents a meaningful
opportunity for health risk reduction for persons served by public
water systems. EPA evaluates the population exposed at the health level
of concern along with several other factors to determine if regulation
presents a meaningful opportunity for health risk reduction. EPA
considers the following factors in evaluating statutory criterion #3:
     Based on the occurrence information for statutory
criterion #2 (and the potential number of systems impacted), what is
the national population exposed or served by

systems with levels [gteqt] HRL and \1/2\ HRL (provide actual and
estimated # and %)?
     What is the nature of the health effect(s) identified in
statutory criterion #1 and are there sensitive populations that may be
impacted (either qualitative or quantitative \18\)?
---------------------------------------------------------------------------

    \18\ If appropriate and if available, the agency quantitatively
takes into account exposure data applicable to sensitive populations
or lifestages when deriving HRLs for regulatory determinations. When
data is not available on sensitive populations, the derivation of
the RfD typically includes an uncertainty factor to account for the
weakness in the database. See section III.C.1. Sensitive populations
are also qualitatively considered by providing national prevalence
estimates for a particular sensitive population if available.
---------------------------------------------------------------------------

     For non-carcinogens, are there other sources of exposure
that should be considered (i.e., what is the relative source
contribution)?
     What is the geographic distribution of occurrence (e.g.,
local, regional, national)?
     Are there any uncertainties and/or limitations in the
health and occurrence information or analyses that should be
considered?
     What other factors or other pieces of information should
be considered that may have direct bearing on any decision to regulate
the contaminant (e.g., treatment, analytical methods,\19\ etc.)?
---------------------------------------------------------------------------

    \19\ If the agency decides to regulate a contaminant, SDWA
requires that EPA issue a proposed regulation within two years of
the final determination (with the possibility of a 9 month
extension). As part of the proposal, the agency must list the best
available technologies (BATs), small system compliance technologies
(SSCTs), and approved analytical methods if it proposes an
enforceable MCL. Alternatively, if EPA proposes a treatment
technique (TT) instead of an MCL, the agency must identify the TT.
EPA must also prepare a health risk reduction and cost analysis.
This analysis includes an extensive evaluation of the treatment
costs and monitoring costs at both system level and aggregated at
the national level. To date, treatment information and approved
analytical methods have not been a significant factor in regulatory
determinations but are important considerations for regulation
development.
---------------------------------------------------------------------------

    After evaluating these factors, if the Administrator determines
that there is a meaningful opportunity to reduce risk by regulating the
contaminant in drinking water, then the agency answers ``yes'' to the
third statutory criterion.
    If the agency answers ``yes'' to all three statutory criteria in
Phase 3 for a particular contaminant, then the agency makes a
``positive'' preliminary determination and requests public comment.
    If after the public comment period, the agency answers ``yes'' to
all three statutory criteria, the agency then makes a ``positive''
final determination that regulation is necessary and proceeds to
develop an MCLG and NPDWR. The agency has 24 months to publish a
proposed MCLG and NPDWR and an additional 18 months to publish a final
MCLG and promulgate a final NPDWR. It should be noted that this
regulatory determination process is distinct from the more detailed
analyses needed to develop a national primary drinking water
regulation. Thus, a decision to regulate is the beginning of the
agency's regulatory development process, not the end.
    If a contaminant has sufficient information and the agency answers
``no'' to any of the three statutory criteria, based on the available
data, then the agency considers making a ``negative'' determination
that an NPDWR is not necessary for that contaminant at that time. The
agency may decide to develop a Health Advisory (HA), which provides
non-regulatory concentration values for drinking water contaminants at
which adverse health effects are not anticipated to occur over specific
exposure durations (one-day, ten-days, several years, and a lifetime).
HAs serve as informal technical guidance to assist Federal, State, and
local officials, and managers of public or community water systems
(CWSs) in protecting public health when emergency spills or
contamination situations occur.
    While a negative determination is considered a final agency action
for this round of regulatory determinations, the contaminant is
reconsidered for inclusion on the next CCL. If new health or occurrence
information becomes available on contaminants with negative regulatory
determinations, the agency considers whether the contaminant(s) should
be listed on the next CCL and further evaluated in the next regulatory
determinations process.
    Of the twelve contaminants that proceeded to Phase 3, the agency is
not making preliminary regulatory determinations for seven contaminants
at this time. The seven contaminants include chlorate and the six
nitrosamines (i.e., NDBA, NDMA, NDPA, NDEA, NPYR, and NMEA). As
discussed in section V, chlorate and the six nitrosamines are DBPs and
the agency plans to consider these contaminants as part of the
regulatory review of existing MDBP regulations. DBPs need to be
evaluated collectively, because the potential exists that the control
of one DBP could affect the concentrations of other DBPs or the
necessary treatment. After evaluating the five remaining CCL 3
contaminants in Table 3 (i.e., dimethoate, 1,3-dinitrobenzene,
strontium, terbufos, and terbufos sulfone) against the three SDWA
criteria and considering the factors listed for each, the agency is
making preliminary regulatory determinations for these five CCL 3
contaminants. Table 5 provides a summary of the five contaminants
evaluated for Phase 3 and the preliminary regulatory determination
outcome. The agency seeks comment on the preliminary determination to
regulate one contaminant (i.e., strontium) and to not regulate the
remaining four contaminants (i.e., dimethoate, 1,3-dinitrobenzene,
terbufos, and terbufos sulfone). Section IV.B of this notice provides a
more detailed summary of the information and the rationale used by the
agency to reach its preliminary decisions for these five contaminants.

      Table 5--Contaminants Evaluated in Phase 3 and the Regulatory
                          Determination Outcome
------------------------------------------------------------------------
                                                       Preliminary
         No.              RD 3 contaminants       determination outcome
------------------------------------------------------------------------
          1           Dimethoate..............  Do not regulate.
          2           1,3-Dinitrobenzene......  Do not regulate.
          3           Strontium...............  Regulate.
          4           Terbufos................  Do not regulate.
          5           Terbufos Sulfone........  Do not regulate.
------------------------------------------------------------------------

B. Supporting Documentation for EPA's Preliminary Determinations

    For this action, EPA prepared several support documents that are
available for review and comment in the EPA Water Docket. These support
documents include:
     The comprehensive regulatory support document entitled,
``Regulatory Determination 3 Support Document'' (USEPA, 2014b),
summarizes the information and data on the physical and chemical
properties, uses and environmental release, environmental fate,
potential health effects, occurrence and exposure estimates, the
preliminary determinations, and the agency's rationale for these
determinations.
     A separate health effects support document for strontium,
entitled ``Health Effects Support Document for Strontium'' (USEPA,
2014c), that addresses exposure from drinking water and other media,
toxicokinetics, hazard identification, and dose-response assessment,
and provides an overall characterization of the risk from drinking
water containing strontium. For the contaminants with negative
determinations, the agency refers the reader to the IRIS or OPP
assessments for more detailed information regarding health effects
(USEPA, 1990a, 1990b, 2003c). These documents serve as the basis for
the health information provided in the regulatory support documents.
     A comprehensive technical occurrence support document for
UCMR 2 entitled, ``Occurrence Data from the Second Unregulated
Contaminant Monitoring Rule (UCMR 2)'' (USEPA, 2014d). This occurrence
support document includes more detailed information about UCMR 2, how
EPA assessed the data quality, completeness, and representativeness,
and how the data were used to generate estimates of drinking water
contaminant occurrence in support of these regulatory determinations.
     A comprehensive protocol document, entitled ``Protocol for
the Regulatory Determination 3'' (USEPA, 2014a). This protocol document
describes the approach implemented by the agency to evaluate 116 CCL 3
contaminants in a three phase process and select the contaminants for
preliminary determinations for RD 3. The protocol underwent expert
review and the comments received were addressed by the agency.

C. Analyses Used To Support the Preliminary Regulatory Determinations

    Sections III.C.1 and 2 of this action outline the health effects
and occurrence/exposure evaluation process EPA used to support these
preliminary determinations.
1. Evaluation of Adverse Health Effects
    Section 1412(b)(1)(A)(i) of SDWA requires EPA to determine whether
each candidate contaminant may have an adverse effect on public health.
This section describes the overall process the agency uses to evaluate
health effects, hazard and dose-response information, and the approach
for deriving the health reference level (HRL) for the contaminants
under consideration for regulatory determinations. HRLs are not final
determinations about the level of a contaminant in drinking water that
must not be exceeded to protect any particular population. HRLs are
derived prior to the development of a complete exposure assessment.
HRLs are risk derived concentrations against which to evaluate the
occurrence data to determine if contaminants occur at levels of
potential public health concern. More specific information about the
potential for adverse health effects for each contaminant is presented
in section IV.B of this action.
    In evaluating contaminants for regulatory determination, Section
1412 (b)(1)(C) of SDWA also requires the agency to consider among other
factors of public health concern, the effect of such contaminants upon
subgroups that comprise a meaningful portion of the general population
``such as infants, children, pregnant women, the elderly, individuals
with a history of serious illness, or other subpopulations'' that are
identifiable as being at greater risk of adverse health effects
compared to the general population. If appropriate and if available,
the agency quantitatively takes into account data from sensitive
populations and lifestages when deriving HRLs for regulatory
determinations.
    There are two general approaches to the derivation of an HRL. One
approach is used for chemicals that cause cancer and exhibit a linear
response to dose and the other applies to non-carcinogens and
carcinogens evaluated using a non-linear approach. The derivation of
HRLs for carcinogens and non-carcinogens are described below.
a. Derivation of an HRL for Carcinogens
    For those contaminants that are considered to be likely or probable
human carcinogens by a mutagenic or unknown mode of action (MOA), the
agency calculates a toxicity value that defines the relationship
between dose and response (i.e., the cancer slope factor or CSF).
(1) MOA: Unknown
    In cases where the data on the mode of action are lacking, EPA
typically uses a default low dose linear extrapolation to calculate a
CSF. The unit risk is the estimated upper-bound excess lifetime cancer
risk from a continuous exposure to a chemical at a concentration of
0.001 mg/L in drinking water. The exposure estimate assumes an adult
body weight of 70 kg and the 90th percentile adult drinking water
intake of 2 L/day.

Unit Risk ([micro]g/L)-\1\ = CSF x [(DWI x CW)/BW]

Where:
CSF = Cancer Slope Factor (mg/kg/day)-\1\
DWI = Drinking Water Intake for an adult, assumed to be 2 L/day
(90th percentile)
CW = Unit risk concentration in drinking water of 0.001 mg/L (1
[micro]g/L)
BW = Body Weight for an adult, assumed to be 70 kilograms (kg)

The cancer HRL is the concentration of a contaminant in drinking water
corresponding to an excess estimated lifetime cancer risk of one-in-a-
million (1 x 10-\6\), calculated as follows:

HRL ([micro]g/L) = Risk Level of 10-\6\ / Unit Risk
([micro]g/L)-\1\

As noted above, HRLs are not final determinations about the level of a
contaminant in drinking water that must not be exceeded to protect any
particular population. Rather, HRLs are risk derived concentrations
against which to evaluate the occurrence data during the RD process to
determine if contaminants occur at levels of potential public health
concern.
(2) MOA: Mutagenic
    If the chemical has a mutagenic mode of action, low dose linear
extrapolation is used to calculate the CSF as described in the
preceding paragraph. The U.S. EPA's 2005 Guidelines for Carcinogen Risk
Assessment (USEPA, 2005b) requires that the potential increased cancer
risk due to early-life exposure be taken into account for chemicals
with a mutagenic mode of action. When chemical-specific data to
quantify the increased risk are lacking, Age Dependent Adjustment
Factors (ADAFs) are applied to estimate age-adjusted unit risks. The
age-adjusted unit risk is determined by using the sum of the unit risks
for each of the three ADAF developmental groups (birth to <2 yrs; 2 yrs
to <16 yrs; 16 yrs to 70 yrs). The age-adjusted unit risks include a
ten-fold adjustment for early life (birth to <2 yrs) exposures, a
three-fold adjustment for childhood/adolescent (2 yrs to <16 yrs)
exposures, and no additional adjustment for exposures later in life (16
yrs to 70 yrs), in conjunction with age-

specific drinking water intake values derived from the U.S. EPA's 2011
Exposure Factors Handbook (USEPA, 2011e), and the fraction of a 70 year
lifetime applicable to each age period. The increase in risk during
early life results from active tissue growth resulting in limited time
for repair of DNA replication errors. The age-adjusted unit risk is the
upper-bound excess lifetime cancer risk estimated to result from
continuous postnatal exposure to a chemical at a concentration of 0.001
mg/L in drinking water.

Age-Adjusted Unit Risk ([micro]g/L) -\1\ = [sum](CSF x ADAF
x DWI/BWR x CW x F)

Where:
CSF = Cancer Slope Factor (mg/kg/day) -\1\
ADAF = The Age Dependent Adjustment Factor for the age group birth
to two-years (ADAF = 10), two years to sixteen years (ADAF = 3), and
sixteen to seventy years (ADAF = 1)
DWI/BWR = Drinking Water Intake Body Weight Ratio (DWI/BWR)
expressed as liters per kg body weight for the age-specific group
(90th percentile, consumers only) \20\
---------------------------------------------------------------------------

    \20\ The drinking water intake values were derived from the data
in the U.S. EPA's Exposure Factors Handbook (USEPA, 2011e). The
procedure used for the data normalization is described in the OW
Policy paper for determining lifetime cancer risks involving early
life exposures (USEPA, 2012c).
---------------------------------------------------------------------------

CW = Unit risk concentration in drinking water of 0.001 mg/L (1
[micro]g/L)
F = The fraction of a 70 year lifetime applicable to the age period:
2/70 for birth to two years, 14/70 for two years to sixteen years
and 54/70 for sixteen years to seventy years

    The cancer HRL is the concentration of a contaminant in drinking
water corresponding to an excess estimated lifetime cancer risk of one-
in-a-million (1 x 10-\6\), calculated as follows:

HRL ([micro]g/L) = Risk Level of 10-\6\ / Age-Adjusted Unit
Risk ([micro]g/L) -\1\
    The six nitrosamines discussed in section V had data available to
classify them as known or likely human carcinogens with a mutagenic
mode of action. Low-dose linear extrapolations and ADAFs were applied
to all four of the CCL 3 nitrosamines: NDMA, NDPA, NDEA and NYPR, as
well as the two non-CCL 3 nitrosamines, NMEA and NDBA. The five
contaminants for which the agency is making preliminary regulatory
determinations (dimethoate, 1,3-dinitrobenzene, strontium, terbufos and
terbufos sulfone) are non-carcinogens and were therefore evaluated
using the RfD approach (discussed in the following section).
b. Derivation of an HRL for Non-Carcinogens
    EPA generally calculates a reference dose (RfD) for those chemicals
considered to be non-carcinogenic or not likely to be carcinogenic to
humans. An RfD is an estimate of a daily oral exposure to the human
population (including sensitive populations or lifestages) that is
likely to be without an appreciable risk of deleterious effects during
a lifetime. The RfD can be derived from either a no-observed-adverse-
effect level (NOAEL), a lowest-observed-adverse-effect level (LOAEL),
or the 95% lower confidence bound on a benchmark dose (BMD), known as a
BMDL, with uncertainty factors applied to reflect limitations of the
data used. In addition, if the critical health endpoint has high
quality data associated with exposure for a specific developmental
group or period of sensitivity, age-specific drinking water intake to
body weight ratio values from the Exposure Factors Handbook (USEPA,
2011e) may be included in deriving an HRL from the RfD.
    The agency uses uncertainty factors (UFs) to address uncertainty
resulting from incompleteness of the toxicological database (e.g.,
lacking sensitive population data). The individual UFs (usually applied
as integers of one, three, or ten) are multiplied together and used to
derive the RfD from experimental data. Individual UFs are intended to
account for:
    (1) Variation in sensitivity among the members of the human
population (i.e., intraspecies variability);
    (2) uncertainty in extrapolating animal data to humans (i.e.,
interspecies variability);
    (3) uncertainty in extrapolating from data obtained in a study with
less-than-lifetime exposure to lifetime exposure (i.e., extrapolating
from subchronic to chronic exposure);
    (4) uncertainty in extrapolating from an LOAEL rather than from an
NOAEL; and/or
    (5) uncertainty associated with an incomplete database.
    For chlorate, dimethoate, 1,3-dinitrobenzene, strontium,\21\
terbufos, and terbufos sulfone, EPA derived the HRLs using the RfD
approach as follows:
---------------------------------------------------------------------------

    \21\ Because the critical health endpoint had dose-response data
associated with exposure during a specific period of sensitivity
(i.e., sensitive population), EPA used age-specific drinking water
intake to body weight ratio values (DWI/BWR) from the Exposure
Factors Handbook (USEPA, 2011e) to derive the HRL for strontium.

---------------------------------------------------------------------------
HRL (mg/L) = [(RfD x BW)/DWI] x RSC

Where:

RfD = Reference Dose (mg/kg-day)
BW = Body Weight for an adult, assumed to be 70 kilograms (kg); for
a child, assumed to be 10 kg
DWI = Drinking Water Intake for an adult, assumed to be 2 L/day
(90th percentile); for child, assumed to be 1L/day (90th percentile)
RSC = Relative Source Contribution, or the level of exposure
believed to result from drinking water when compared to other
sources (e.g., food, ambient air). In all cases, a 20% RSC is used
for HRL derivation because (1) HRLs are developed prior to a
complete exposure assessment and (2) 20% is the most conservative
RSC used in the derivation of an MCLG for drinking water.

c. Sources of Data/Information for Health Effects
    EPA uses the best available peer-reviewed data and analyses in
evaluating adverse health effects. Peer-reviewed health-risk
assessments are available for all chemicals considered for regulatory
determinations from the agency's Integrated Risk Information System
(IRIS) Program, \22\ the agency's Office of Pesticide Programs
(OPP),\23\ the National Academy of Sciences (NAS), the Agency for Toxic
Substances and Disease Registry (ATSDR),\24\ and/or the World Health
Organization (WHO).\25\ For a non-EPA health

assessment (i.e., NAS, ATSDR, WHO) to be considered for regulatory
determinations, the health assessment must use comparable methods,
standards, and guidelines to an EPA health assessment. Table 6
summarizes the sources of the health assessment data for each chemical
under consideration for RD 3.
---------------------------------------------------------------------------

    \22\ IRIS is an electronic EPA data base (www.epa.gov/iris/index.html) containing peer-reviewed information on human health
effects that may result from exposure to various chemicals in the
environment. These chemical files contain descriptive and
quantitative information on hazard identification and dose response,
RfDs for chronic noncarcinogenic health effects, as well as slope
factors and unit risks for carcinogenic effects.
    \23\ The OPP is required under the Federal Insecticide Fungicide
and Rodenticide Act (FIFRA) to periodically review the health
effects data on all registered pesticides and reregister them for
continued use. The results of the reregistration analysis are
published in the Reregistration Eligibility Decision (RED)
documents. Copies of the REDs are located at the following EPA Web
site (http://www.epa.gov/oppsrrd1/reregistration/status.htm).
    \24\ ATSDR establishes oral minimal risk levels for non-
neoplastic endpoints for acute (14 days or less), intermediate (15--
364 days), and chronic (365 days or more) exposure durations.
Minimal risk levels for oral chronic exposure are similar to EPA's
RfDs. However, ATSDR and EPA use different approaches when the
database is limited to subchronic studies and no adequate chronic
study is available. ATSDR derives an intermediate duration minimal
risk level that protects against exposures up to 10% of a lifetime,
and it does not incorporate an uncertainty factor to account for
using a less-than-lifetime study. ATSDR does not perform
quantitative cancer assessments or assign formal cancer
classifications or descriptors.
    \25\ WHO establishes a ``guideline value'', a drinking water
concentration that uses different default assumptions than EPA for
estimating water concentration from doses, including a 60 kg adult
body weight, daily water consumption of 2 L/day, and a data derived
or default RSC of 10%. WHO develops one guideline value that is
based either on cancer or non cancer.
---------------------------------------------------------------------------

    The agency performs a literature search for studies published after
the available health assessment is completed to determine if new
information suggests a different outcome. The agency collects and
evaluates any peer-reviewed publications identified through the
literature search for their impact on the RfD and/or cancer assessment.
In cases where the recent data indicate that a change to the existing
RfD or cancer assessment is needed, the EPA Office of Water prepares
and independently peer-reviews an ``OW Assessment'' of the data. EPA
updates all quantitative cancer assessments conducted under the
Guidelines for Carcinogen Risk Assessment (USEPA, 1986) using the
Guidelines for Carcinogen Risk Assessment (USEPA, 2005b), the
Supplemental Guidance for Assessing Susceptibility from Early-life
Exposures to Carcinogens (USEPA, 2005c), and the Exposure Factors
Handbook (USEPA, 2011e). These guidelines include considerations for
contaminants with a mutagenic mode of action and potential risks due to
early childhood exposure.

                            Table 6--Sources and Dates of EPA Health Risk Assessments
----------------------------------------------------------------------------------------------------------------
                                                                                OW Assessment
                        Chemical                            IRIS (date)       OPP RED (date)         (date)
----------------------------------------------------------------------------------------------------------------
Dimethoate.............................................  .................               2007  .................
1,3-Dinitrobenzene \1\.................................               1988  .................  .................
Strontium..............................................               1992  .................               2012
Terbufos...............................................  .................               2006  .................
Terbufos Sulfone \2\...................................  .................               2006  .................
----------------------------------------------------------------------------------------------------------------
\1\ The agency also reviewed a non-EPA source (ATSDR, 1995) for 1,3-dinitrobenzene to corroborate the IRIS
  assessment.
\2\ The OPP RED for the parent compound (terbufos) was used.

    As noted in section III.B, EPA prepared a technical Health Effects
Support Document for strontium (USEPA, 2014c). This document addresses
the exposure from drinking water and other media, toxicokinetics,
hazard identification, and dose-response assessment, and provides an
overall characterization of risk from drinking water. For the
contaminants with a preliminary negative determination (i.e., a
decision not to regulate), refer to the EPA health risk assessments
online from OPP or IRIS for additional health effect information.
2. Evaluation of Contaminant Occurrence and Exposure
    EPA uses data from many sources to evaluate occurrence and exposure
from drinking water contaminants. The following comprise the primary
sources of finished drinking water occurrence data discussed in this
Federal Register notice:
     the Unregulated Contaminant Monitoring Regulation (UCMR 1
and 2),
     the National Inorganic and Radionuclide Survey (NIRS), and
     Disinfection Byproducts Information Collection Rule (DBP
ICR).
    Several of the primary sources of finished water occurrence data
are designed to be statistically representative of the nation. These
data sources include UCMR 1, UCMR 2, and NIRS.\26\ The DBP ICR is
geographically distributed across the country and national in scope but
is not intended to be statistically representative of the nation.
---------------------------------------------------------------------------

    \26\ NIRS is designed to be statistically representative of
groundwater systems and does not include surface water systems.
---------------------------------------------------------------------------

    The agency also evaluates supplemental sources of information on
occurrence in drinking water, occurrence in ambient and source water,
and information on contaminant use and release to augment and
compliment these primary sources of drinking water occurrence data.
Section III.C.2.a. of this action provides a brief summary of the
primary sources of finished water occurrence data, and sections
III.C.2.b and II.C.2.c provide brief summary descriptions of some of
the supplemental sources of occurrence information and/or data. These
descriptions do not cover all the reports that EPA reviews and
evaluates. For individual contaminants EPA reviews additional published
reports and peer-reviewed studies that may provide the results of
monitoring efforts in limited geographic areas. A summary of the
occurrence data and the results or findings for each of the
contaminants considered for regulatory determination is presented in
section IV.B, the contaminant profiles section, and the data are
described in further detail in the support documents for the RD 3
process (see USEPA, 2014a, b, c and d).
a. Primary Sources of Finished Drinking Water Occurrence Data
    As previously mentioned, the primary national sources of the
drinking water occurrence data discussed in this Federal Register
notice are UCMR 1, UCMR 2, NIRS, and the DBP ICR. The following
sections provide a brief summary of these data sources. Table 7 in
section IV lists the primary data source/finding used to evaluate each
of the five contaminants considered for regulatory determinations. The
contaminant-specific discussions in section IV provide more detailed
information about the primary data source findings as well as any
supplemental occurrence information.
(1) The Unregulated Contaminant Monitoring Regulation (UCMR 1 and UCMR
2)
    The UCMR is currently EPA's primary vehicle for collecting
monitoring data on the occurrence of unregulated contaminants in PWSs.
The UCMR is designed to collect nationally representative occurrence
data and is developed in coordination with the CCL and Regulatory
Determination process and the National Drinking Water Contaminant
Occurrence Database (NCOD). The UCMR sampling is limited by statute to
30 contaminants during any five year cycle (SDWA section 1445(a)(2))
and the PWSs and State primacy agencies are required to report the data
to EPA. EPA published the list and requirements for the first
Unregulated Contaminant Monitoring Regulation cycle (i.e., UCMR 1) in
September 17, 1999 (64 FR 50556, September 17, 1999, USEPA, 1999; see
also 65 FR 11372, March 2, 2000, USEPA, 2000a; and 66 FR 2273, January
11, 2001, USEPA, 2001a), and the monitoring was conducted primarily
during 2001-2003. UCMR 2 was published on January 4, 2007 (72 FR 367;
USEPA, 2007a), with monitoring

conducted during 2008-2010. (The complete analytical monitoring lists
are available at: http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/.)
    The UCMR was designed as a three-tiered approach for monitoring
contaminants related to the availability of analytical methods and
related analytical laboratory capacity. Assessment Monitoring (AM), the
largest sampling tier, typically relies on analytical methods that are
in common use in drinking water laboratories. The Screening Survey
(SS), the second tier, uses newly developed analytical methods that may
not be as commonly used in drinking water laboratories. The SS has
involved a smaller number of PWSs because laboratory capacity is
expected to be limited. The third tier, Pre-Screen Testing was designed
to address contaminants with analytical methods that are in an early
stage of development and the analyses would be limited to a few special
laboratories. The expectation was that it would only involve the
limited number of systems determined to be most vulnerable to the
targeted contaminants. No Pre-Screen Testing was conducted during UCMR
1 or UCMR 2.
    EPA designed the AM sampling frame to ensure that sample results
would support a high level of confidence and a low margin of error (see
USEPA, 1999 and 2001b, for UCMR design details). AM is required for all
large PWSs, those serving more than 10,000 people (i.e., a census of
all large systems) and a national statistically representative sample
of 800 small PWSs, those serving 10,000 or fewer people (for a total
sample of approximately 4,000 systems). PWSs that purchase 100% of
their water were not required to participate.
    Each system conducts UCMR assessment monitoring for one year
(during the three-year monitoring period). The rules require quarterly
monitoring for surface water systems and twice-a-year, six-month
interval monitoring for ground water systems. At least one sampling
event must occur during a specified vulnerable period. Differing
sampling points within the PWS may be specified for each contaminant
related to the contaminants source(s).
    The objective of the UCMR sampling approach for small systems was
to collect contaminant occurrence data from a statistically selected,
nationally representative sample of small systems. The small system
sample was stratified and population-weighted, and included some other
sampling adjustments such as allocating a selection of at least two
systems from each State for spatial coverage. The UCMR AM program
includes systems from all 50 States, the District of Columbia, four
U.S. Territories, and Tribal lands in five EPA Regions. With
contaminant monitoring data from all large PWSs--a census of large
systems--and a statistical, nationally representative sample of small
PWSs, the UCMR AM program provides a robust dataset for evaluating
national drinking water contaminant occurrence.
    UCMR 1 AM was conducted by approximately 3,090 large systems and
797 small systems. Approximately 33,800 samples were collected for each
contaminant. In UCMR 2, sampling was conducted by over 3,300 large
systems and 800 small systems, and resulted in over 32,000 sample
results for each contaminant.
    As noted, in addition to AM, SS monitoring was required for
contaminants. For UCMR 1, the SS was conducted at 300 PWSs (120 large
and 180 small systems) selected at random from the pool of systems
required to conduct AM. Samples from the 300 PWSs from throughout the
nation provided approximately 2,300 analyses for each contaminant.
While the statistical design of the SS is national in scope, the
uncertainty in the results for contaminants that have low occurrence is
relatively high. Therefore, EPA looked for additional data to
supplement the SS data for regulatory determinations.
    For the UCMR 2 SS, EPA improved the design to include a census of
all systems serving more than 100,000 people (approximately 400 PWSs--
but the largest portion of the national population served by PWSs) and
a nationally representative, statistically selected sample of 320 PWSs
serving between 10,001 and 100,000 people, and 480 small PWSs serving
10,000 or fewer people (72 FR 367, January 4, 2007, USEPA, 2007a). With
approximately 1,200 systems participating in the SS, sufficient data
were generated to provide a confident national estimate of contaminant
occurrence and population exposure. In UCMR 2, the 1,200 PWSs provided
more than 11,000 to 18,000 analyses (depending on the sampling design
for the different contaminants).
    As previously noted, the details of the occurrence data and the
results or findings for each of the contaminants considered for
regulatory determination is presented in Section IV.B, the contaminant
profiles section, and is described in further detail in the support
documents for the RD 3 process (USEPA, 2014a and 2014b). The national
design, statistical sampling frame, any new analytical methods, and the
data analysis approach for the UCMR program has been peer-reviewed at
different stages of development (see, USEPA, 2001b, 2008c, 2014d, for
example.)
(2) National Inorganics and Radionuclides Survey (NIRS)
    EPA conducted the NIRS to provide a statistically representative
sample of the national occurrence of 36 selected inorganic compounds
(IOCs) and radionuclides in CWSs served by ground water. The sample was
stratified by system size and 989 ground water CWSs were selected at
random representing 49 States (all except Hawaii) as well as Puerto
Rico. The survey focused on ground water systems, in part because IOCs
tend to occur more frequently and at higher concentrations in ground
water than in surface water. Each of the selected CWSs was sampled at a
single time between 1984 and 1986.
    One limitation of the NIRS is a lack of occurrence data for surface
water systems. EPA also reviews additional finished water data from
State datasets and other sources, as well as data from ambient and
source surface waters, to augment the NIRS data. Information about NIRS
monitoring and data analysis is available in The Analysis of Occurrence
Data from the Unregulated Contaminant Monitoring (UCM) Program and
National Inorganics and Radionuclides Survey (NIRS) in Support of
Regulatory Determinations for the Second Drinking Water Contaminant
Candidate List (USEPA, 2008b).
(3) Disinfection Byproducts Information Collection Rule (DBP ICR)
    The DBP ICR (61 FR 24353, May 14, 1996 (USEPA, 1996)) required PWSs
serving at least 100,000 people to monitor and collect data on DBPs
from July 1997 to December 1998. The DBP ICR data were collected from
296 water systems that provided extensive information on the occurrence
of DBPs and on water treatment methods. The DBP ICR data were collected
as part of a national project to support development of national
disinfection by-products and microbial drinking water standards. EPA
used the data to identify national and regional patterns and overall
water quality, not to reach system-by-system or treatment plant-by-
treatment plant conclusions. Additional details on the data collection
process for the DBP ICR, along with an independent analysis of the
data, can be found in a report sponsored by the Microbial/Disinfection
Products Council (McGuire et al., 2002).

    The DBP ICR provided a census of the largest systems that serve the
largest proportion of the population served by PWSs at that time. It
has previously been vetted for use in regulatory development, and EPA
determined it can be used in the regulatory determination process.
b. Supplemental Sources of Finished Drinking and Ambient Water
Occurrence Data
    The agency evaluates several sources of supplemental information
related to contaminant occurrence in finished water and ambient and
source waters to augment the primary drinking water occurrence data.
Some of these sources were part of other agency information gathering
efforts or submitted to the agency in public comment or suggested by
stakeholders during previous CCL and Regulatory Determination efforts.
These supplemental data are useful to evaluate the likelihood of
contaminant occurrence in drinking water and/or to more fully
characterize a contaminant's presence in the environment and
potentially in source water, and to evaluate any possible trends or
spatial patterns that may need further review. The descriptions that
follow do not cover all the reports that EPA used. For individual
contaminants EPA reviewed additional published reports and peer-
reviewed studies that may have provided the results of monitoring
efforts in limited geographic areas. A more detailed discussion of the
supplemental sources of information/data that EPA evaluated and the
occurrence data for each contaminant can be found in the comprehensive
regulatory determination support documents (USEPA, 2014a and 2014b).
(1) Individual States' Data
    To support the second Six-Year Review of regulated contaminants
(see USEPA, 2009b), EPA issued an ICR to collect compliance monitoring
data from PWSs for the time period covering 1998-2005. After issuing
the ICR, EPA received monitoring data from 45 States plus Region 8 and
Region 9 Tribes. Six States and Region 9 Tribes also provided
monitoring data for unregulated contaminants along with their
compliance monitoring data. EPA further collected additional
unregulated contaminant data from two additional States that provide
monitoring data through their Web sites. EPA reviews these datasets
during the RD 3 process. These datasets vary from State to State in the
contaminants included, the number of samples, and the completeness of
monitoring. They are reviewed and used to augment the national data and
assess if they provide supportive observations or any unique occurrence
results that might warrant further review.
(2) Community Water System Survey (CWSS)
    EPA periodically conducts the CWSS to collect data on the financial
and operating characteristics from a nationally representative sample
of CWSs. As part of the CWSS, all systems serving more than 500,000
people receive the survey. In the 2000 and 2006 CWSS, these very large
systems were asked questions about the occurrence and concentration of
unregulated contaminants in their raw and finished water. The 2000 CWSS
(USEPA, 2002a, 2002b) requested data from 83 very large CWSs and the
2006 CWSS (USEPA, 2009c, 2009d) requested data from 94 very large CWSs.
Not all systems answered every question or provided complete
information on the unregulated contaminants. Because reported results
are incomplete, they are illustrative, not representative, and are only
used as supplemental information.
(3) United States Department of Agriculture (USDA) Pesticide Data
Program (PDP)
    Since 1991, the USDA PDP has gathered data on pesticide residues in
food. In 2001 the program expanded to include sampling of pesticide
residues in treated drinking water, and in 2004 some sampling of raw
water was incorporated as well (USDA, 2004). The CWSs selected for
sampling tend to be small and medium-sized water surface water systems
(serving under 50,000 people) located in regions of heavy agriculture.
The sampling frame is designed to monitor in regions of interest for at
least two years to reflect the seasonal and climatic variability during
growing seasons. PDP works with EPA and the American Water Works
Association (AWWA) to identify specific water treatment facilities
where monitoring data are collected. The number of sites and samples
have varied among different sampling periods. EPA reviewed the PDP data
on the occurrence of select contaminants in untreated and treated water
(USDA, 2004).
(4) United States Geological Survey (USGS) Pilot Monitoring Program
(PMP)
    In 1999, USGS and EPA conducted the PMP to provide information on
pesticide concentrations in small drinking water supply reservoirs in
areas with high pesticide use (Blomquist et al., 2001). The study was
undertaken, in part, to test and refine the sampling approach for
pesticides in such reservoirs and related drinking water sources.
Sampling sites represent a variety of geographic regions, as well as
different cropping patterns. Twelve water supply reservoirs considered
vulnerable to pesticide contamination were included in the study.
Samples were collected quarterly throughout the year and at weekly or
biweekly intervals following the primary pesticide-application periods.
Water samples were collected from the raw water intake and from the
finished drinking water prior to entering the distribution system. At
some sites, samples were also collected at the reservoir outflow.
(5) United States Geological Survey (USGS) National Water Quality
Assessment (NAWQA)
    The USGS instituted the National Water Quality Assessment (NAWQA)
program in 1991 to examine ambient water quality status and trends in
the United States. The NAWQA program is designed to apply nationally
consistent methods to provide a consistent basis for comparisons over
time nationally and among significant watersheds and aquifers across
the country. These occurrence assessments serve to facilitate
interpretation of natural and anthropogenic factors affecting national
water quality. The NAWQA program monitors the occurrence of chemicals
such as pesticides, nutrients, VOCs, trace elements, and radionuclides,
and the condition of aquatic habitats and fish, insects, and algal