```

[Federal Register Volume 79, Number 202 (Monday, October 20, 2014)]
[Proposed Rules]
[Pages 62715-62750]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-24582]

[[Page 62715]]

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

[[Page 62716]]

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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 (202) 566-1744, and the telephone number for the Water 
Docket is (202) 566-2426.

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: bain.zeno@epa.gov. 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
------------------------------------------------------------------------
           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.

[[Page 62717]]

 
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)

[[Page 62718]]

    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.
---------------------------------------------------------------------------

    \6\ The health advisories for CCL 2 can be found at http://water.epa.gov/drink/standards/hascience.cfm.
---------------------------------------------------------------------------

    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

[[Page 62719]]

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:
---------------------------------------------------------------------------

    \7\ More information about the DWS can be found at 
water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/.
---------------------------------------------------------------------------

    (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.
---------------------------------------------------------------------------

    \8\ http://water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/.
---------------------------------------------------------------------------

    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

[[Page 62720]]

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).
---------------------------------------------------------------------------

    \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).

[[Page 62721]]

[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

[[Page 62722]]

(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.

[[Page 62723]]

 
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

[[Page 62724]]

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.

[[Page 62725]]

                                  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.

[[Page 62726]]

 
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

[[Page 62727]]

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.
------------------------------------------------------------------------

[[Page 62728]]

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 adolescent (2 yrs to 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

[[Page 62730]]

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

[[Page 62731]]

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).

[[Page 62732]]

    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 
communities. For more detailed information on the NAWQA program design 
and implementation, please refer to Leahy and Thompson (1994), Hamilton 
et al. (2004), and NRC (2002).
    The NAWQA program has been designed in ten-year cycles to enable 
national coverage that can be used for trends and causal assessments. 
In the Cycle 1 monitoring period, which was conducted from 1991 through 
2001, NAWQA collected data from over 6,400 surface water and 7,000 
ground water sampling points. Cycle 2 monitoring covers the period from 
2002 through 2012, with various design changes from Cycle 1 (see 
Hamilton et al., 2004).
    EPA, with the cooperation of USGS, performed a summary analysis of 
all Cycle 1 water monitoring data for the CCL 3 and Regulatory 
Determination process. The surface water data consisted of stream 
samples; all surface water data were included in the EPA summary 
analysis. For ground water, all well data were used and data from 
springs and drainage systems were excluded.

[[Page 62733]]

    For RD 3, EPA used and evaluated many USGS NAWQA reports to review 
causal or spatial factors that USGS may have presented in their 
interpretations. In particular, EPA evaluated many reports from the 
Pesticide National Synthesis Programs (e.g., Gilliom et al., 2007) and 
the VOC National Synthesis (e.g., Delzer and Ivahnenko, 2003). While 
there is overlap in the data used in the USGS reports and the EPA 
analysis, the USGS reports can provide unique observations related to 
their synthesis of additional data.
    For RD 3, EPA also supplemented these data with information from 
recent special USGS reports that also used additional data from other 
programs, particularly reports that focused on contaminant occurrence 
in source waters for PWSs, such as: Organic Compounds in Source Water 
of Selected Community Water Systems (Hopple et al., 2009 and Kingsbury 
et al., 2008), and Water Quality in Public-Supply Wells (Toccalino et 
al., 2010).
(6) Storage and Retrieval (STORET) Data System
    EPA's STORET database contains raw biological, chemical, and 
physical data from surface and ground water sampling conducted by 
Federal, State and local agencies, Indian Tribes, volunteer groups, 
academics, and others. A wide variety of data relating to water quality 
from all 50 States as well as multiple territories and jurisdictions of 
the United States are represented in this data system. These are 
primarily ambient water data, but in some cases they include finished 
drinking water data. STORET data have quality limitations. There are 
few restrictions on submission of data based on analytical methods, 
quality assurance (QA) practices, etc. For more general STORET data 
information, please refer to: http://www.epa.gov/storet/index.html. EPA 
reviewed STORET ground water data from wells and surface water data 
from lakes, rivers/streams, and reservoirs.
c. Supplemental Production, Use and Release Data
    The agency reviews various sources of information to assess if 
there are changes or trends in a contaminant's production, use, and 
release that may affect its presence in the environment and potential 
occurrence in drinking water. The cancellation of a pesticide or a 
clear increase in production and use of a contaminant are trends that 
can inform the regulatory determination process. 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). Several sources are described in more detail below.
(1) Chemical Update System/Inventory Update Rule (CUS IUR)
    The IUR regulation requires manufacturers and importers of certain 
chemical substances, included on the Toxic Substances Control Act 
(TSCA) Chemical Substance Inventory, to report site and manufacturing 
information and the amount of chemicals produced or imported in amounts 
of 25,000 pounds or more at a single site. Additional information on 
domestic processing and use must be reported for chemicals produced or 
imported in amounts of 300,000 pounds or more at a single site. Prior 
to the 2003 TSCA Amendments (i.e., reporting from 2002 or earlier), 
information was collected for only organic chemicals that were produced 
or imported in amounts of 10,000 pounds or more, and was limited to 
more basic manufacturing information such as production volume. Because 
of changes in reporting rules, contaminants may have reports for some 
years but not others (USEPA, 2010a).
(2) Toxic Release Inventory (TRI)
    EPA established the Toxics Release Inventory (TRI) in 1987 in 
response to Section 313 of the Emergency Planning and Community Right-
to-Know Act (EPCRA). EPCRA Section 313 requires facilities to report to 
both EPA and the States annual information on toxic chemical releases 
from facilities that meet reporting criteria. The TRI database details 
not only the types and quantities of toxic chemicals released to the 
air, water, and land by facilities, but also provides information on 
the quantities of chemicals sent to other facilities for further 
management (USEPA, 2002c, 2003b). Currently, for most chemicals the 
reporting thresholds are 25,000 pounds for manufacturing and processing 
and 10,000 pounds for use. Both the number and type of facilities 
required to report has increased over time.
    Although TRI can provide a general idea of release trends, it has 
limitations because of the reporting changes over time. Finally, TRI 
data are meant to reflect ``releases'' and should not be used to 
estimate general public exposure to a chemical (USEPA, 2002c).
(3) Pesticide Usage Estimates
    For the regulatory determinations process, the agency reviews 
various sources of information about pesticide usage. SDWA directs EPA 
to consider pesticides in the CCL process. Pesticide use and 
manufacturing information is considered confidential business 
information and therefore, accurate measures of production and use are 
not publically available. As a result, the agency reviews various 
estimates of use as supplemental information in the deliberative 
process.
    Occasionally, EPA presents estimations of annual U.S. usage of 
individual pesticides in its pesticide reregistration documents (e.g., 
Reregistration Eligibility Decisions or (REDs), Interim Reregistration 
Eligibility Decisions (IREDs), Tolerance Reassessment Progress and Risk 
Management Decisions (TREDs)). EPA also periodically issues Pesticides 
Industry Sales and Usage reports. The reports provide contemporary and 
historical information on U.S. pesticide production, imports, exports, 
usage, and sales, particularly with respect to dollar values and 
quantities of active ingredient. The most recent report presents data 
from the years 2000 and 2001 (USEPA, 2004).
    The National Center for Food and Agricultural Policy (NCFAP), a 
private non-profit institution, has also produced national pesticide 
use estimates based on USDA State-level statistics and surveys for 
commercial agriculture usage patterns and State-level crop acreage. The 
database contains estimates of pounds applied and acres treated in each 
State for 220 active (pesticide) ingredients and 87 crops. The majority 
of the chemicals monitored are herbicides, but the database also 
follows significant numbers of fungicides and insecticides (NCFAP, 
2000).
    The USGS produced usage estimates and maps for over 200 pesticides 
used in United States crop production, providing spatial insight to the 
regional use of many pesticides (USGS, 2007). These pesticide use 
estimates were generated by the USGS through State-level estimates of 
pesticide usage rates for individual crops that were compiled by the 
CropLife Foundation and the Crop Protection Research Institute, 
combined with county-level data on harvested crop acreage obtained from 
the 2002 Census of Agriculture.

IV. Contaminant-Specific Discussions for the RD 3 Preliminary 
Regulatory Determinations

A. Summary of the Preliminary Regulatory Determination

    Based on EPA's evaluation of the three SDWA criteria (discussed in 
section II.B.1), the agency is making

[[Page 62734]]

preliminary determinations to regulate one contaminant and to not 
regulate four contaminants. Table 7 summarizes the primary health and 
occurrence information used to make these preliminary regulatory 
determinations. 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 7--Summary of the Health and Occurrence Information and the Preliminary Determinations for the Five Contaminants Considered for Regulatory Determinations 3
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                   Occurrence findings from primary data sources
                                                                      ------------------------------------------------------------------------------------------------------
                                                            Health                                         Population served by                                                  Preliminary
               No.                   RD 3 contaminants     reference      Primary    PWSs with at least 1  PWSs with at least 1  PWSs with at least 1  Population served by     determination
                                                          level (HRL)    database      detection >=\1/2\     detection >=\1/2\      detection >=HRL    PWSs with at least 1
                                                                                              HRL                   HRL                                   detection >=HRL
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1................................  Dimethoate..........  15.4 [mu]g/L            UCMR0% (0 of 4138)......  0% (0 of 229M)......  0% (0 of 4138)......  0% (0 of 229M)......  Do not regulate.
2................................  1,3-Dinitrobenzene..  0.7 [mu]g/L             UCMR0% (0 of 4137)......  0% (0 of 229M)......  0% (0 of 4137)......  0% (0 of 229M)......  Do not regulate.
3................................  Strontium...........  1,500 [mu]g/         NIRS   14.3% (141 of 989)..  16.6% (246K of 1.5M)  7.0% (69 of 989)....  10.7% (158.5K of      Regulate.
                                                                   L                                                                                    1.5M).
4................................  Terbufos............  0.35 [mu]g/L            UCMR0% (0 of 295).......  0% (0 of 41M).......  0% (0 of 295).......  0% (0 of 41M).......  Do not regulate.
5................................  Terbufos Sulfone....  0.35 [mu]g/L            UCMR0.02% (1 of 4138)...  0.01% (44.6K of       0.02% (1 of 4138)...  0.01% (44.6K of       Do not regulate.
                                                                                                            229M).                                      229M).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

B. Contaminant Profiles

    This section provides further information on the background, 
health, and occurrence data that the agency uses to evaluate each of 
the five candidate contaminants considered for regulatory 
determinations. For each candidate, the agency evaluates the available 
human and toxicological data, derives a health reference level, and 
evaluates the potential and/or likely occurrence and exposed population 
for the contaminant in public water systems. The agency also considers 
whether information is available on sensitive populations. The agency 
uses the findings from these evaluations to determine whether the three 
SDWA statutory criteria are satisfied. The agency also prepares a 
regulatory support document (USEPA, 2014b) that provides more details 
on the background, health, and occurrence information/analyses used to 
evaluate and make preliminary determinations for these five 
contaminants.
1. Dimethoate
a. Background
    Dimethoate is an organophosphate pesticide, commonly used as an 
insecticide on field crops (e.g., wheat, alfalfa, corn, and cotton), 
orchard crops, vegetable crops, and in forestry. Synonyms for 
dimethoate include dimethogen, dimeton, dimevur, and cygon (HSDB, 2009; 
USEPA, 2007b). EPA has estimated that the total annual average domestic 
use of dimethoate is approximately 1.8 million pounds (USEPA, 2007b). 
EPA's most recent Pesticide Industry Sales and Usage reports indicate 
that the amount of dimethoate active ingredient (a.i.) used in the 
United States was between 1 and 2 million pounds in 1999 and 2001, and 
less than 1 million pounds in 2005 and 2007 (USEPA, 2004: USEPA, 
2011f). TRI data from the years 1997 to 2010 show that annual releases 
to various sources range from tens of pounds to tens of thousands of 
pounds, with the larger releases occurring only occasionally and in no 
clear pattern (USEPA, 2012a). For example, reported on-site air 
emissions were in the range of tens of pounds for 1997-2005 but 
increased to the range of thousands of pounds in 2006-2010. The only 
reported non-zero release by underground injection was in 2004 and was 
over 28,000 pounds. Reported on-site releases to surface water and land 
were low or non-existent in most years, but peaked suddenly at nearly 
20,000 pounds in 1998 (land) and over 2,000 pounds in 2004 (surface 
water). Dimethoate is considered highly mobile and relatively non-
persistent in the environment (USEPA, 2007b).
b. Statutory Criterion #1 (Adverse Health Effects)
    Dimethoate meets the SDWA statutory criterion #1 for regulatory 
determinations; it may have an adverse effect on the health of persons. 
Dimethoate belongs to a group of pesticides called organophosphates, 
which share a common MOA. Organophosphates affect the proper function 
of the nervous system by inhibiting cholinesterase (ChE), an important 
enzyme involved in neurotransmission. Inhibition of ChE in the brain, 
plasma, and red blood cells is the most sensitive endpoint described in 
numerous studies with adult and juvenile animals, following oral, 
dermal, or inhalation exposures of dimethoate or its primary toxic 
metabolite omethoate (USEPA, 2007b). As discussed in the 2007 OPP 
assessment, the U.S. EPA's Cancer Assessment Review Committee (CARC) 
classified dimethoate as a Group C carcinogen (a possible human 
carcinogen) in 1991, with concurrence from the FIFRA Scientific 
Advisory Panel (SAP) on the agency's classification in 1992 (USEPA, 
2007b).
    The 2007 OPP assessment established a chronic oral RfD for 
dimethoate of 0.0022 mg/kg/day based on a 2-year feeding study in rats 
with inhibition of brain ChE as the critical effect (USEPA, 2007b). The 
RfD was derived using the BMD method and based on the lower 95% 
confidence limit (BMDL) of 0.22 mg/kg/day, with application of a 
composite UF of 100 (i.e., intraspecies and interspecies variability). 
EPA calculated a non-cancer HRL of 15.4 [mu]g/L for dimethoate using 
the RfD of 0.0022 mg/kg/day for a 70 kg adult ingesting 2 L of drinking 
water per day and an RSC of 20%. The chronic RfD and subsequent HRL of 
15.4 [mu]g/L for dimethoate are considered to be protective of any 
potential cancer risk or acute ChE effects (USEPA, 1990a, 2007b). The 
OPP RED (USEPA, 2007b) presents more detailed information

[[Page 62735]]

about the potential health effects for dimethoate.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public 
Health Concern)
    Dimethoate does not meet the SDWA statutory criterion #2 for 
regulatory determinations; it does not occur with a frequency and at 
levels of public health concern in public water systems based on EPA's 
evaluation of the following occurrence information.
    The primary data for dimethoate are recent (2008-2010) nationally-
representative drinking water monitoring data, generated through EPA's 
UCMR 2. Dimethoate was not detected in any of the 32,013 UCMR 2 samples 
collected by 4,138 PWSs (serving ~ 230 million people) at levels 
greater than the \1/2\ HRL (7.7 [mu]g/L), the HRL (15.4 [mu]g/L), or 
the MRL (0.7 [mu]g/L) (USEPA, 2014d).
    The State of California reported results from testing more than 
20,000 finished drinking water samples from over 2,000 PWSs and 
dimethoate was detected in two samples from two different PWSs. The 
detected concentrations (1 [mu]g/L and 2 [mu]g/L) were less than the 
\1/2\ HRL (7.7 [mu]g/L) and the HRL (15.4 [mu]g/L) (see USEPA, 2014b). 
The USDA PDP monitored for dimethoate in finished water from 2001 to 
2009 and had only two detections in 3,555 samples; both detected 
concentrations were less than the \1/2\ HRL and the HRL (USDA, 2012). 
The USGS PMP monitored for dimethoate in finished water in 1999 and had 
no detections greater than \1/2\ the HRL or the HRL in any of the 221 
samples (Blomquist et al., 2001).
    Dimethoate occurrence data for ambient water are consistent with 
those for finished drinking water. The USGS PMP also monitored for 
dimethoate in ambient water in 1999 and had no detections greater than 
the \1/2\ HRL (7.7 [mu]g/L) or the HRL (15.4 [mu]g/L) in any of the 317 
samples (Blomquist et al., 2001). Ambient water data from a two-phase 
USGS study conducted between 2002 and 2005 by Hopple et al. (2009) and 
Kingsbury et al. (2008) reported no detections in the 221 Phase 1 
groundwater samples. Only two detections were reported from 146 Phase 1 
surface water samples at nine PWSs. The highest concentration detected 
was 0.009 [mu]g/L, which is less than the \1/2\ HRL and the HRL. In 
Phase 2, there were no detections of dimethoate from 48 raw and 
finished water groundwater samples (Hopple et al., 2009; Kingsbury et 
al., 2008). Ambient water data in STORET included no measured results 
above 0.44 [mu]g/L in 5,299 samples from 798 sites (USEPA, 2012b). 
Ambient water data reported by the California Department of Pesticide 
Regulation included no measured results above 2.4 [mu]g/L (USEPA, 
2007b).
d. Statutory Criterion #3 (Meaningful Opportunity)
    EPA finds that dimethoate does not meet the SDWA statutory 
criterion #3 for regulatory determinations; regulation of dimethoate 
does not present a meaningful opportunity health risk reduction for 
persons served by PWSs based on the estimated exposed population, 
including sensitive populations. The estimated population exposed to 
dimethoate at levels of public health concern is 0%; it was not found 
to occur at levels above the HRL (or the \1/2\ HRL) in 4,138 PWSs and 
32,013 samples from the UCMR 2 monitoring. In addition, other 
supplementary sources of finished water and ambient water data indicate 
that the occurrence of dimethoate in PWSs is likely to be low to non-
existent. As a result, the agency finds that an NPDWR for dimethoate 
does not present a meaningful opportunity for health risk reduction.
    EPA also evaluated whether health information is available 
regarding the potential health effects on children and other sensitive 
populations. The database for dimethoate includes a 3-generation 
reproductive study in mice, developmental (teratology) studies in rats 
and rabbits, and a neurodevelopmental toxicity study (USEPA, 1990a, 
2007b). The critical effect of ChE inhibition is a more sensitive 
endpoint compared to the reproductive and developmental endpoints 
(USEPA, 2007b); therefore no sensitive populations were identified or 
characterized. The OPP RED (USEPA, 2007b) presents more detailed 
information about the potential health effects and sensitive 
populations for dimethoate.
e. Preliminary Regulatory Determination
    The agency is making a preliminary determination to not regulate 
dimethoate with an NPDWR after evaluating health, occurrence, and other 
related information against the three SDWA statutory criteria. While 
data suggests that dimethoate may have an adverse effect on human 
health, the occurrence data indicate that dimethoate is not occurring 
or not likely to occur in PWSs with a frequency and at levels of public 
health concern. Therefore, the agency finds that an NPDWR would not 
present a meaningful opportunity to reduce health risk for persons 
served by PWSs. The Regulatory Determinations 3 Support Document 
(USEPA, 2014d) and the Occurrence Data from the Second Unregulated 
Contaminant Monitoring Regulation (UCMR 2) (USEPA, 2014a) present 
additional information and/or analyses supporting the agency's 
evaluation of dimethoate.
2. 1,3-Dinitrobenzene
a. Background
    1,3-Dinitrobenzene is a nitro aromatic compound that is used as an 
industrial chemical and formed as a by-product in the manufacture of 
munitions as well as in the production of other substances (HSDB, 
2009). There are no known natural sources of 1,3-dinitrobenzene. Annual 
production and importation of 1,3-dinitrobenzene in the United States 
was last reported by CUS-IUR in 1986 to be between 10-50 million pounds 
(USEPA, 2010b). TRI data indicate 19,858 pounds were released to the 
environment by industry in 2008 and 10,595 pounds in 2010 (USEPA, 
2012a). 1,3-dinitrobenzene appears to be moderately persistent in 
environmental media and moderately mobile in soil and water, though in 
soils with high clay content it will be less mobile (USEPA, 2014b).
b. Statutory Criterion #1 (Adverse Health Effects)
    1,3-dinitrobenzene meets the SDWA statutory criterion #1 for 
regulatory determinations; it may cause adverse effect on the health of 
persons. 1,3-dinitrobenzene has demonstrated adverse health effects in 
many rodent and occupational studies. Occupational studies indicate 
that methemoglobinemia, hemolytic anemia, and cyanosis are seen in 
workers who experience an acute reaction to 1,3-dinitrobenzene (Hajjar 
et al., 1992). The EPA IRIS assessment (USEPA, 1990b) of the 
carcinogenicity of 1,3-dinitrobenzene currently lists it as Group D 
(not classifiable as to human carcinogenicity).
    The primary adverse biological effects from exposure to 1,3-
dinitrobenzene are on red blood cells, spleen, and testes. The RfD for 
1,3-dinitrobenzene is 0.0001 mg/kg/day (Cody et al., 1981). The RfD was 
derived from a NOAEL of 0.4 mg/kg/day in a subchronic oral study in 
rats where increased spleen weight was identified as the critical 
effect (Cody et al., 1981). A composite UF of 3,000 (intraspecies 
variability, interspecies variability, subchronic to chronic duration, 
and lack of chronic, developmental, and multigenerational reproductive 
toxicity studies) was

[[Page 62736]]

applied to the NOAEL to obtain the RfD. EPA calculated a non-cancer HRL 
of 0.7 [mu]g/L for 1,3-dinitrobenzene using the RfD of 0.0001 mg/kg/day 
for a 70 kg adult ingesting 2 L of drinking water per day and an RSC of 
20%.
    The current EPA oral RfD value is supported by a more recent 1,3-
dinitrobenzene assessment that was conducted by ATSDR, in which an oral 
intermediate duration minimal risk level of 0.0005 mg/kg/day for 
splenic hemosiderosis in male rats was established using a LOAEL of 
0.54 mg/kg/day (Linder et al., 1986; dose adjusted for a 7-day/week 
exposure) and a composite UF of 1,000 (intraspecies variability and 
interspecies variability, LOAEL to NOAEL). Based on EPA assumptions and 
a composite UF of 3,000 (intraspecies variability, interspecies 
variability, LOAEL to NOAEL and subchronic to chronic duration) applied 
to the LOAEL of 0.54 mg/kg/day, the resultant HRL value of 1 [mu]g/L 
supports the HRL value of 0.7 [mu]g/L derived from the IRIS RfD (ATSDR, 
1995). The IRIS assessment (USEPA, 1990b) presents more detailed 
information about the potential health effects for 1,3-dinitrobenzene.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public 
Health Concern)
    1,3-dinitrobenzene does not meet the SDWA statutory criterion #2 
for regulatory determinations; it does not occur with a frequency and 
at levels of public health concern in public water systems based on 
EPA's evaluation of the following occurrence information.
    The primary data for 1,3-dinitrobenzene are recent (2008-2010) 
nationally-representative drinking water monitoring data generated 
through EPA's UCMR 2 (USEPA, 2014d). UCMR 2 is the only dataset with 
finished water data for this contaminant. UCMR 2 collected 32,017 
samples from 4,137 PWSs and 1,3-dinitrobenzene was not detected above 
the MRL (0.8 [mu]g/L), which is only slightly higher than the HRL (0.7 
[mu]g/L).
    Findings from the available ambient water data for 1,3-
dinitrobenzene are consistent with the results in finished water. 
Ambient water data in STORET included no measured results above 0.33 
[mu]g/L in 143 samples from 70 sites (USEPA, 2012b). It should be noted 
that some occurrence above the HRL may have gone undetected since 
reporting levels are not documented.
d. Statutory Criterion #3 (Meaningful Opportunity)
    EPA finds that 1,3-dinitrobenzene does not meet the SDWA statutory 
criterion for regulatory determinations; regulation of 1,3-
dinitrobenzene does not present a meaningful opportunity for health 
risk reduction for persons served by PWSs based on the estimated 
exposed population, including sensitive populations. The estimated 
population exposed to 1,3-dinitrobenzene at or above the MRL is 0%; it 
was not found to occur in finished drinking water at levels > MRL (0.8 
[mu]g/L), which is only slightly higher than the HRL (0.7 [mu]g/L), in 
32,017 samples and 4,137 PWSs from the UCMR 2 monitoring. As a result, 
the agency finds that an NPDWR for 1,3-dinitrobenzene does not present 
a meaningful opportunity for health risk reduction.
    EPA also evaluated whether information is available regarding the 
potential health effects on children and other sensitive populations. 
Individuals with a genetic predisposition to methemoglobinemia 
(estimated prevalence in the general population = 1% or 1 per 100) and/
or hemosiderosis, neonates, and those co-exposed to other hemolytic 
agents, could be more sensitive to exposure to 1,3-dinitrobenzene 
(ATSDR, 1995; Jaffe and Hultquist, 1989). Males having sperm production 
complications could also have increased sensitivity to 1,3-
dinitrobenzene exposure (Hajjar et al., 1992). There is currently no 
multigenerational animal study available for 1,3-dinitrobenzene, and no 
data available from studies of 1,3-dinitrobenzene developmental 
toxicity (Hajjar et al., 1992). However, the RfD incorporated a UF for 
this database deficiency. The IRIS assessment (USEPA, 1990b) presents 
more detailed information about the potential health effects and 
sensitive populations for 1,3-dinitrobenzene.
e. Preliminary Regulatory Determination for 1,3-dinitrobenzene
    The agency is making a preliminary determination to not regulate 
1,3-dinitrobenzene with an NPDWR after evaluating health, occurrence, 
and other related information against the three SDWA statutory 
criteria. While data suggest that 1,3-dinitrobenzene may have an 
adverse effect on human health, the occurrence data indicate that 1,3-
dinitrobenzene is not occurring or not likely to occur in PWSs with a 
frequency and at levels of public health concern. Therefore, the agency 
has determined that an NPDWR for 1,3-dinitrobenzene would not present a 
meaningful opportunity to reduce health risk for persons served by 
PWSs. The Regulatory Determinations 3 Support Document (USEPA, 2014b) 
and the Occurrence Data from the Second Unregulated Contaminant 
Monitoring Regulation (UCMR 2) (USEPA, 2014d) present additional 
information and analyses supporting the agency's evaluation of 1,3-
dinitrobenzene.
3. Strontium
a. Background
    Strontium is a naturally occurring element (atomic number 38) and a 
member of the alkaline earth metals (ANL, 2007). There are several 
radioactive strontium isotopes formed by nuclear fission of uranium or 
plutonium. The best known is \90\Sr, a legacy from above ground testing 
of the atomic bomb (half-life 29 years). Since drinking water 
contamination by radioactive isotopes, including beta particle 
emitters, is covered under the existing radionuclides rule, this FR 
notice deals primarily with the stable \88\Sr isotope which represents 
83% of total environmental strontium (ATSDR, 2004).
    Strontium mineral mining ceased in the United States in 1959. The 
United States imports both strontium minerals for refining and refined 
strontium containing compounds (USGS, 2009). Imports of strontium 
minerals and compounds were approximately 31,000 to 38,500 metric tons 
from 1994 to 2001 and have declined since 2001 (ATSDR, 2004; USGS, 
2009). In the United States, total consumption of strontium minerals 
and compounds was 16,700 metric tons of strontium content in 2004 and 
approximately 7,750 metric tons in 2008 (USGS, 2009).
    Historically, the most important commercial use of strontium has 
been in the faceplate glass of cathode-ray tube televisions to block x-
ray emissions (ATSDR, 2004). Conversely, flat panel televisions 
incorporating LCD or Plasma displays are not capable of emitting x-
radiation; therefore, they do not require strontium (FDA, 2011). As 
flat panel technology has become widespread in the United States in the 
last decade, demand for strontium for this application has fallen 
(USGS, 2009). In 2008, approximately 30% of commercial strontium 
consumption was in pyrotechnics and signals (as strontium nitrate and 
other compounds), 30% in ferrite ceramic magnets (as strontium 
ferrite), 10% in master alloys (as strontium metal), 10% in pigments 
and fillers (as strontium chromate), 10% in electrolytic production of 
zinc (as strontium carbonate), and 10% in other applications such as 
fluorescent lights (strontium phosphate), toothpaste (strontium 
chloride), and medicines (strontium chloride and strontium peroxide). 
The feed material for most

[[Page 62737]]

applications is strontium carbonate (ATSDR, 2004; HSDB, 2010; USGS, 
2009). Strontium can exist in oxidation states 0 and +2; under normal 
environmental conditions it is found in the +2 oxidation state in 
various ionic or salt forms. Strontium is considered to have moderate 
or moderate-to-low mobility in soils. The mobility of strontium in 
water can increase with increased salt concentrations due to a decrease 
in sorption to sediments (USEPA, 20104b). The Regulatory Determination 
3 Support Document (USEPA, 2014b) for this notice presents more 
detailed background information on strontium.
b. Statutory Criterion #1 (Adverse Health Effects)
    Strontium meets the SDWA statutory criterion #1 for regulatory 
determinations; it may have an adverse effect on the health of persons. 
The primary target of strontium exposure is the bone. The chemical 
similarity of strontium to calcium allows it to exchange imperfectly 
for calcium in a variety of biological processes; the most important of 
these is the substitution of calcium in bone, affecting skeletal 
development. Due to the MOA for strontium toxicity, strontium uptake 
into bone is affected by the intake of nutrients related to bone 
formation, such as calcium, phosphorous, and vitamin D (Clarke, 2008; 
Grynpas and Marie, 1990; Marie et al., 1985). The decreased 
calcification in bones results in increased width of the epiphyseal 
cartilage, changes in the pattern of calcification, abnormally long 
metaphyses, reduction in bone mineralization, and active osteoclasts in 
young rats (Marie and Hott, 1986; Matsumoto, 1976; Neufeld and Boskey, 
1994; Storey, 1961). Due to this effect on growing bones, infants, 
children, and adolescents are of particular concern as a sensitive 
population.
    A study based on decreased bone calcification rate in male weanling 
rats (i.e., comparable to the sensitive time period in humans), which 
administered strontium chloride in drinking water for nine weeks (Marie 
et al., 1985), was identified by EPA as the critical study for RfD 
determination. The RfD was established by using the BMD method and 
based on the lower 95% confidence limit (BMDL) of 328 mg/kg/day for a 
one standard deviation decrease in bone calcification compared to 
control. Using a composite UF of 1000 (10 for intraspecies variability, 
10 for interspecies variability, and 10 for database uncertainties) the 
RfD for strontium is calculated to be 0.3 mg/kg/day. This RfD is 
supported by additional studies reporting bone effects on weanling rats 
at similar dose levels (Grynpas and Marie, 1990; Storey, 1961). EPA 
calculated a non-cancer HRL of 1500 [micro]g/L for strontium using the 
RfD of 0.3 mg/kg/day, a default RSC of 20% and age-specific exposure 
factors (i.e., drinking water intake expressed as liters per kg of body 
weight) for the sensitive population of birth through 18 years to 
reflect the most active period of bone growth and development (see 
section IV.B.10.d.3).
    EPA released an IRIS assessment for strontium in 1992 and developed 
an RfD of 0.6 mg/kg/day based on the Storey, 1961 study. The IRIS 
assessment was completed before the 1998 changes to the IRIS program 
wherein the agency develops and peer reviews a detailed Toxicological 
Review before posting an IRIS summary. The point of departure for the 
1992 IRIS RfD of 0.6 mg/kg/day is a NOAEL of 190 mg Sr/kg-day with a 
composite UF of 300 (10 for interspecies variability, 3 for 
intraspecies variability, and 10 for database uncertainties). This 
would yield an HRL of 3000 [micro]g/L, using the same age-specific 
exposure adjustment factors described above. If the age-specific 
exposure adjustment factors were not used, the HRL would be 2000 
[micro]g/L based on the OW assessment, or 4000 [micro]g/L based on the 
IRIS assessment. As noted in section III.C.1.c, EPA evaluates the 
existing data and performs a literature search for studies published 
after the available health assessment is completed to determine if new 
information suggests a different outcome. In cases where the review 
suggests that a change the existing RfD or cancer assessment is needed, 
the EPA Office of Water prepares and independently peer-reviews an OW 
Assessment of the data. In the case of strontium and because newer 
information provided additional support for the 1985 Marie et al. 
study, EPA chose to use the BMDL of 328 mg/kg/day from Marie et al., 
(over the 1961 Storey study) for the following reasons: (a) Marie et 
al., (1985) reported the doses rather than estimated the doses; (b) the 
study duration was longer (63 days for Marie as compared to 20 days for 
Storey); (c) the monitoring of the bone effects for Marie et al., 
(1985) was more quantitative than the photomicrographs evaluated by 
Storey (1961); (d) dosing was provided via drinking water, the medium 
of interest (rather than a weakly soluble SrCO3 in the diet); (e) Marie 
et al., (1985) reported the strain of rats and the age of the animals, 
at the time that dosing was initiated and completed; (f) the data were 
amenable to dose-response modeling to identify the BMD and BMDL; and 
(g) the dietary calcium provided in the Storey study was three times 
higher than that in the Marie study, making those rats less at risk due 
to the calcium and strontium competition for uptake, as verified by a 
comparison of serum data from the two studies. The OW assessment uses a 
10x uncertainty factor for intraspecies variability, rather than the 3x 
factor used in the 1992 IRIS assessment because it is not clear if the 
window of vulnerability was adequately captured, since the weanling 
rats were exposed only for 28-63 days, a period that did not include 
exposure during gestation, lactation, and through young adulthood. EPA 
requests comment on its revised RfD calculation and on its proposal to 
use the OW assessment in lieu of the RfD from the 1992 IRIS assessment.
    There is inadequate information to assess the carcinogenic 
potential of strontium due to the lack of adequate studies of chronic 
duration. The Health Effects Support Document (USEPA, 2014c) for this 
determination presents more detailed analysis of the health effects of 
strontium.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public 
Health Concern?)
    Strontium meets the SDWA statutory criterion #2 for regulatory 
determinations; it does occur with a frequency and at levels of public 
health concern in public water systems based on EPA's evaluation of the 
following occurrence information.
    EPA used the National Inorganics and Radionuclides Survey (NIRS) 
(USEPA, 2008b) as the primary data source to evaluate the occurrence of 
strontium in PWSs. It provides contaminant occurrence data from 989 
CWSs served by ground water sources. Each of these randomly selected 
PWSs was sampled a single time between 1984 and 1986. Of the 989 
systems in NIRS, 980 (99%) had detectable levels of strontium ranging 
from 1.53 to 43,550 [micro]g/L. The mean concentration was 603 
[micro]g/L. Approximately 7.0% (69 of 989) of the NIRS PWSs detected 
strontium at a level greater than the HRL (1500 [micro]g/L) and 14.3% 
(141 of 989) detected strontium at a level greater than \1/2\ HRL (750 
[micro]g/L). Extrapolated by the total number of ground water CWSs 
found nationally, this represents 2,798 and 5,718 groundwater CWSs that 
could have strontium at a level greater than the HRL and the \1/2\ HRL, 
respectively. These figures are summarized in Table 8 (USEPA, 2014b).

[[Page 62738]]

                               Table 8--Estimates of Population Exposed to Strontium, Observed and Extrapolated From NIRS
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              National Inorganics and Radionuclides Survey    Extrapolation of NIRS data to groundwater
                                                                                 (NIRS)                                  systems nationwide
                          Threshold                          -------------------------------------------------------------------------------------------
                                                                     Systems               Population              Systems               Population
--------------------------------------------------------------------------------------------------------------------------------------------------------
Systems with Detectable Concentrations......................                 99.1%                  99.9%                  99.1%                  99.9%
                                                                      (980 of 989)     (1.481M of 1.482M)       (39.7K of 40.1K)       (93.0M of 93.1M)
Systems detecting strontium above one half the HRL (>750                     14.3%                  16.6%                  14.3%                  16.6%
 [micro]g/L)................................................          (141 of 989)         (246K of 1.5M)        (5.7K of 40.1K)       (15.4M of 93.1M)
Systems detecting strontium above the HRL (>1500 [micro]g/L)                  7.0%                  10.7%                   7.0%                  10.7%
                                                                       (69 of 989)         (159K of 1.5M)        (2.8K of 40.1K)       (10.0M of 93.1M)
--------------------------------------------------------------------------------------------------------------------------------------------------------

    As a point of reference to the earlier IRIS assessment, if EPA used 
the HRL derived from this assessment of 3000 [micro]g/L, 30/989 systems 
(3%) would have finished water samples that exceed the HRL using the 
NIRS data, compared to 69/989 (7%) using the HRL of 1500 [micro]g/L 
derived from the more recent OW assessment.
    Finished water data, analyzed between 1998 and 2005, from Ohio and 
Illinois are also consistent with the NIRS data. The State of Illinois 
reported results from testing 21 drinking water samples from 19 PWSs 
and strontium was detected in all 21 samples (100%) from all 19 systems 
(100%). Approximately 23.8% (5 of 21) of samples from five systems 
(26.3%) had strontium at levels greater than the \1/2\ HRL (750 
[micro]g/L) and approximately 23.8% (5 of 21) of samples from five 
systems (26.3%) had strontium at levels greater than the HRL (1500 
[micro]g/L) (USEPA, 2012b). The State of Ohio reported results from 
testing 77 samples from 32 PWSs and strontium was detected in 75 
samples (97.4%) from 30 different systems (93.8%). Approximately 27.3% 
(21 of 77) of samples from 10 systems (31.3%) had strontium at levels 
greater than the \1/2\ HRL and approximately 23.4% (18 of 77) of 
samples from seven systems (21.9%) had strontium at levels greater than 
the HRL (USEPA, 2014b).
    Although there are limited surface water data available for 
strontium, the available data are consistent and demonstrate high 
occurrence in surface waters. Ambient water data for strontium are also 
consistent with high occurrence in finished water, which is expected 
since it is a naturally occurring element. The NAWQA Quality of Public 
Supply Wells (Toccalino et al., 2010) study collected water samples 
from source (untreated) groundwater public supply wells in 41 states. 
Each well was sampled once from 1993-2007 and 100% of samples (503 of 
503) had a strontium detection. Of the detections, 25.1% (126 of 503) 
were above the \1/2\ HRL (750 [micro]g/L) and 12.1% (61 of 503) were 
above the HRL (1500 [micro]g/L). Additional occurrence information on 
strontium can be found in the Regulatory Determinations 3 Support 
Document (USEPA, 2014b).
d. Statutory Criterion #3 (Meaningful Opportunity?)
    EPA makes a preliminary finding that strontium meets the SDWA 
statutory criterion #3 for regulatory determinations; regulation of 
strontium in drinking water presents a meaningful opportunity for 
health risk reduction based on the estimated exposed population, 
potential impacts on sensitive populations and estimated exposure from 
other sources (e.g., food).
    1. National Population Exposed: In the NIRS dataset 989 ground 
water systems were sampled serving a population of 1.48 million. The 
NIRS data indicates that the population exposed to strontium at a level 
greater than the HRL (1500 [micro]g/L) is 158,557 (11%) and the \1/2\ 
HRL (750 [micro]g/L) is 245,870 (17%) (USEPA, 2012b). EPA also 
performed national extrapolations generated by multiplying the NIRS 
findings of system/population percentages and the national system/
population inventory numbers for PWSs developed from EPA's Safe 
Drinking Water Information System, the CWSS, and UCMR. Out of the 93.1 
million people served by 40,106 ground water CWSs in the nation, the 
national extrapolation indicates that 10.0 million may be exposed to 
concentrations greater than the HRL (1500 ug/L) and 15.4 million may be 
exposed to concentrations greater than the \1/2\ HRL (750 ug/L). The 
system and population estimates are summarized in Table 8.
    Strontium occurs naturally and is abundant in the environment. Its 
occurrence in water at concentrations >HRL may be a reflection of the 
geologic and geochemical setting of the source waters for PWSs. The 
NIRS drinking water data showed that strontium was detected in one or 
more systems sampled in all 48 continuous states, Alaska and Puerto 
Rico (Hawaii was not included in NIRS). The occurrence data (e.g., 
NIRS) show that PWSs with strontium at concentrations greater than the 
HRL and the \1/2\ HRL occur in 26 states and 34 states, respectively 
(USEPA, 2014b).
    2. Exposure from media other than water: EPA has determined that 
there is a meaningful opportunity to regulate strontium in drinking 
water to reduce the public's overall exposure after evaluating the 
available exposure data from media other than water. Although strontium 
is known to occur in food, air, and soil, data on levels in those media 
are limited as are estimates of intake from those sources. Therefore, 
EPA used the default 20% RSC to calculate the HRL. This section 
provides a summary of the available exposure data.
    An FDA Total Diet Study by Pennington and Jones (1987) collected 
234 individual foods in 1984 from three cities in one region of the 
country and indicated dietary intakes of 493 [micro]g/day for young 
children (6 to 11 months), 928 to 1,388 [micro]g/day for 14 to 16 year 
old adolescents, and 979-1,489 [micro]g/day for adults. The FDA Total 
Diet Study foods are prepared with distilled water and do not reflect 
any contributions from the cooking water during preparation of foods 
that absorb water such as rice and pasta. Thus, the strontium in many 
foods will be impacted by the strontium levels in the local water 
supply. Using the mean of the detected water concentrations from the 
NIRS dataset (603 [micro]g/L), the estimated water intake for young 
children (90th percentile water intake of 1L/day) is 603 [micro]g/day 
and 1,206 [micro]g/day for adults (90th percentile water intake of 2L/
day). The estimated strontium intakes from air and soil are very low 
compared with those from food and drinking water. The estimated air 
exposure for children is 0.1 [micro]g/day and for adults is 0.3 
[micro]g/day (Dzubay and Stevens, 1975). The estimated exposure from 
soil is 24 [micro]g/day for children and 12 [micro]g/day for

[[Page 62739]]

adults (Shacklette and Boerngen, 1984). No data were identified on 
consumer products, such as toothpaste that contain strontium as an 
ingredient or impurity.
    3. Sensitive populations: Children are expected to be a sensitive 
population, since they are actively growing and strontium can 
substitute for calcium in growing bone. This means that changes in bone 
structure and homeostasis may have more severe and/or a long-term 
impact than similar changes in adults. These effects would be expected 
to have the greatest impact during periods of rapid growth in the 
developing fetus, during childhood and adolescence, particularly if 
their calcium intake is insufficient (Abrams et al., 2000; Lee et al., 
1996; Matkovic et al., 2005; Storey, 1961). The estimated populations 
of pregnant women (and thus fetuses) and of children (L) are expected 
to be protective of the sensitive population, assuming that 80% of 
exposure comes from other sources such as air, soil and food.
    The toxic effects of strontium result from strontium ions 
substituting for calcium ions, therefore calcium deficiency would be 
expected to result in increased risk among sensitive populations. In 
this respect, it is important to note that recent NHANES data indicate 
that about 50% of females, nine years and older, fail to receive 
adequate calcium from diet and supplements on a daily basis (IOM, 
2010). Groups with higher risks of becoming calcium deficient include: 
Adolescent girls, postmenopausal women, amenorrheic women, female 
athletes, vegans, and individuals with lactose intolerance or cow's 
milk allergies (IOM, 2010; NIH, 2011a).
    The major route of elimination of strontium is via the kidneys, 
therefore individuals with impaired renal function are another 
sensitive population. This population may potentially have impaired 
strontium clearance, as has been shown in renal failure patients. There 
are approximately 20 million people (10%) above the age of 20 with 
chronic kidney disease (CDC, 2010) and 548,000 people with kidney end-
stage renal disease (USRDS, 2010), who may be at an increased risk. 
People with disorders affecting the normal equilibrium between the 
breakdown of old bone and the formation of new bone (such as Paget's 
disease) might also be sensitive to strontium exposure (D'Haese et al., 
1999, 2000; Schrooten et al., 1998, 2003; Tothill et al., 1983). 
According to the National Institute of Arthritis and Musculoskeletal 
and Skin Diseases, there are approximately 1 million people (1.2 people 
per 100 men and women age 45 to 74) diagnosed with Paget's disease of 
the bone (NIH, 2011b). The Health Effects Support Document (USEPA, 
2014c) for strontium presents more detailed information about the 
potential health effects and sensitive populations. Because the RfD 
includes an uncertainty factor of 10 for intraspecies variability, the 
RfD is also expected to be protective of these sensitive populations.
d. Preliminary Regulatory Determination
    At this time, the agency is making a preliminary determination to 
regulate strontium with an NPDWR after evaluating the available health, 
occurrence, and other related information against the three SDWA 
statutory criteria. Specifically, it is EPA's preliminary determination 
that (a) strontium may have an adverse effect on the health of persons, 
(b) it is known to occur or there is substantial likelihood that 
strontium will occur in public water systems with a frequency and at 
levels of public health concern, (c) regulation of strontium with an 
NPDWR presents a meaningful opportunity to reduce health risks for 
persons served by PWSs.
    It is important to note that the agency included strontium in UCMR 
3. As of January 2014, a preliminary analysis (USEPA, 2014e) of the 
first nine months of the UCMR 3 monitoring data indicate that 4.9% (70 
of 1,423) of systems, 3.8% (175 of 4,547) of entry points, and 3.9% 
(274 of 7,061) of samples have detects of strontium at levels greater 
than the HRL of 1500 [micro]g/L. While EPA believes the occurrence data 
from NIRS (in concert with the supplemental information discussed 
earlier) are sufficient to make the regulatory determination, the 
agency believes the additional monitoring results from UCMR 3 will 
assist EPA in making the final regulatory determination for strontium 
and in developing the proposed NPDWR. As noted in section III.A.3, this 
regulatory determination process is distinct from the more detailed 
analyses needed to develop a national primary drinking water 
regulation. To inform the agency, the EPA plans to conduct more 
extensive field testing of treatment technologies to assess the 
effectiveness of strontium removal in PWSs prior to promulgating a 
national primary drinking water regulation. Thus a decision to regulate 
is the beginning of the agency's regulatory development process, not 
the end. As the agency collects additional information about drinking 
water and other sources of exposure (and performs more detailed 
analyses), this information will inform the agency's opinion as to 
whether strontium should be regulated. The agency asks the public to 
submit any data or information that may be useful in evaluating 
drinking water and other sources of exposure (e.g., food, food prepared 
in drinking water, air, soil, etc.).
4 and 5. Terbufos and Terbufos Sulfone
a. Background
    Terbufos is a phosphorodithioate pesticide (i.e., an 
organophosphate) used as an insecticide-nematicide to control a variety 
of insect pests, primarily used on corn and sugar beets (USEPA, 2006c). 
Terbufos sulfone is a degradate of terbufos. EPA's most recent 
Pesticide Industry Sales and Usage report states that between 5 and 7 
million pounds of terbufos active ingredient were used in 1999 and 
between 3 and 5 million pounds of active ingredient were used in 2001 
(USEPA, 2004). There are no industrial release data available for 
terbufos from TRI. As a pesticide degradate, terbufos sulfone is 
neither produced nor used commercially. Total toxic residues of 
terbufos and degradates are highly mobile and persistent in the 
environment, with terbufos sulfone being more mobile and substantially 
more persistent than terbufos (USEPA, 2006c).
b. Statutory Criterion #1 (Adverse Health Effects?)
    Terbufos and its degradate, terbufos sulfone, meet the SDWA 
statutory criterion #1 for regulatory determinations; they may cause an 
adverse effect on the health of persons. Terbufos and terbufos sulfone 
belong to a group of pesticides called organophosphates, which share a 
common mechanism of toxicity. Organophosphates affect the proper 
function of the nervous system by inhibiting ChE, an essential enzyme 
in neurotransmission. There has been no evidence that terbufos is 
carcinogenic in animal studies (Rapp, 1974; Silverman

[[Page 62740]]

et al., 1986) and it is classified as a class D carcinogen (inadequate 
evidence of carcinogenicity) (USEPA, 1988). Overall, health effects 
information for the terbufos sulfone degradate is lacking; there are no 
long-term studies or cancer classification for terbufos sulfone.
    The 2006 OPP RED assessment (USEPA, 2006c) established an oral RfD 
for terbufos of 0.00005 mg/kg/day, derived from the NOAEL of 0.005 mg/
kg/day for ChE inhibition in the 28-day and 1-year dog studies by 
Shellenberger (1984) and Shellenberger and Billups (1986). A composite 
UF of 100 (interspecies and intraspecies variability) was applied to 
the NOAEL to obtain the RfD. EPA calculated a non-cancer HRL of 0.35 
[micro]g/L for terbufos using the RfD of 0.00005 mg/kg/day for a 70 kg 
adult ingesting 2 L of drinking water per day and an RSC of 20%. The 
agency has not developed an RfD for terbufos sulfone because subchronic 
and chronic studies are not available. However, Bailey (1988) conducted 
a 14-day study of both terbufos and its sulfone degradate in dogs. The 
NOAEL based on ChE activity for terbufos sulfone was greater than the 
LOAEL of 2.5 mg/kg/day for the same endpoint following 14-day dosing 
with the parent compound terbufos. This suggests that the terbufos 
sulfone degradate is less toxic than its parent, and that the use of 
the terbufos HRL of 0.35 [micro]g/L for the degradate, terbufos 
sulfone, is acceptable. The OPP RED (USEPA, 2006c) presents more 
detailed information about the health effects for terbufos and terbufos 
sulfone.
c. Statutory Criterion #2 (Occurrence at frequency and levels of public 
health concern?)
    Terbufos and terbufos sulfone do not meet the SDWA statutory 
criterion #2 for regulatory determinations; they do not occur with a 
frequency and at levels of public health concern in public water 
systems based on EPA's evaluation of the following occurrence 
information.
    The primary data for terbufos sulfone are nationally-representative 
finished water monitoring data generated through EPA's UCMR 2 (2008-
2010) (USEPA, 2014d). UCMR 2 collected 32,012 finished water samples 
from 4,138 PWSs (serving ~ 230 million people) and terbufos sulfone was 
detected in only one sample, at a concentration of 0.42 [micro]g/L. The 
MRL was 0.4 [micro]g/L, which is slightly higher than the HRL (0.35 
[micro]g/L) (USEPA, 2012d). The primary data for terbufos are from the 
UCMR 1 screening survey (2001-2003) (USEPA, 2008c). The UCMR 1 
screening survey collected 2,301 finished water samples from 295 PWSs. 
Terbufos was not detected at levels at or above the MRL (0.5 [micro]g/
L), which is slightly higher than the HRL (0.35 [micro]g/L) (USEPA, 
2008c). Finished water data for terbufos and terbufos sulfone from 
California, Iowa, USDA, and USGS are also consistent with the UCMR 1 
and UCMR 2 data. The State of California reported no detections of 
terbufos in 191 samples from 23 PWSs (see USEPA, 2014b). The State of 
Iowa reported no detections of terbufos sulfone from 13 wells (see 
USEPA, 2014b). The USDA PDP monitored for terbufos (2,597 samples) and 
terbufos sulfone (2,923 samples) in finished water from 2001 to 2009 
and reported no detections at or above method reporting levels ranging 
from 0.005 [micro]g/L to 0.1 [micro]g/L (USDA, 2012: USEPA, 2014b). The 
USGS PMP monitored for terbufos in finished water in 1999 and reported 
no detections, at or above their method reporting level of 0.013 
[micro]g/L (Blomquist et al., 2001).
    Terbufos and (very limited) terbufos sulfone occurrence data for 
ambient water from EPA, STORET, and several USGS programs or studies 
are consistent with those for finished water. The USGS NAWQA Program 
(1992-2001) reported no groundwater detections above the \1/2\ HRL 
(0.175 [micro]g/L) or the HRL (0.35 [micro]g/L) for terbufos in 20,960 
samples at 7,118 sites. NAWQA reported surface water detections for 
terbufos in 28 of 14,480 samples (0.19%) at 20 of 1,907 sites (1.05%). 
Of the 28 surface water detections for terbufos, only four samples 
(0.03%) at four sites (0.21%) were above the \1/2\ HRL and only one 
sample (0.01%) at one site (0.05%) was above the HRL (Gilliom et al., 
2007). The NAWQA Carbonate Aquifer Study (1993-2005; Lindsey et al., 
2008) and the NAWQA Domestic Well Water Quality Study (1991-2004; 
DeSimone, 2009) reported no detections for terbufos above the \1/2\ HRL 
or the HRL in 1,027 and 2,539 samples, respectively. The NAWQA National 
Synthesis Program (1992-2001) reported no groundwater detections for 
terbufos above the \1/2\ HRL or the HRL and one surface water detection 
(0.56 [micro]g/L), from agricultural sites, above the HRL (Gilliom et 
al., 2007).
    Ambient water data from a two phase USGS study conducted between 
2002 and 2005 by Hopple et al. (2009) and Kingsbury et al. (2008) 
reported no terbufos detections in the 221 Phase 1 groundwater samples 
nor the 146 Phase 1 surface water samples. In Phase 2, there were no 
detections of terbufos from 48 raw and 48 finished groundwater samples. 
Ambient water data from a USGS study conducted between 1993 and 2007 by 
Toccalino et al. (2010) reported no terbufos detections in 898 
groundwater samples.
    Terbufos ambient data reported in EPA's OPP RED for Terbufos 
(USEPA, 2006c) document included 20 detections in 4,563 groundwater 
samples from 13 States. The detections ranged from 0.01 to 20 [micro]g/
L, a range that extends both above and below the \1/2\ HRL (0.175 
[micro]g/L) and the HRL (0.35 [micro]g/L). The USGS PMP monitored for 
terbufos in ambient water in 1999 and reported no detections (Blomquist 
et al., 2001).
    Terbufos ambient data are reported in STORET from 17 States (USEPA, 
2012b). No groundwater detections were reported in 699 samples at 441 
sites. STORET reported surface water detections in 457 of 5,826 samples 
(7.84%) at 138 of 625 sites (22.1%). Of the 457 surface water 
detections, only 23 samples (0.39%) at 14 sites (2.24%) were above the 
\1/2\ HRL and only two samples (0.03%) at two sites (0.32%) were above 
the HRL.
d. Statutory Criterion #3 (Meaningful Opportunity?)
    Terbufos and terbufos sulfone do not meet the SDWA statutory 
criterion #3 for regulatory determinations; regulation of terbufos and 
terbufos sulfone do not present a meaningful opportunity for health 
risk reduction based on the estimated population exposed, including 
sensitive populations. The estimated population exposed to terbufos at 
or above the MRL is 0%; the compound was not found to occur in finished 
water at levels greater than or equal to the MRL (0.4 [mu]g/L), which 
is slightly higher than the HRL (0.35 [mu]g/L), in 2,301 samples from 
295 PWSs in UCMR 1 (USEPA, 2008c). The estimated population exposed to 
terbufos sulfone at a level of public health concern (based on the HRL 
for terbufos) is 44,600 (0.02% of the population served by PWSs); there 
was only one detection greater than the HRL in 4,138 PWSs (1 of 32,012 
samples in UCMR 2) (USEPA, 2014d). As a result, the agency finds that 
an NPDWR does not present a meaningful opportunity for health risk 
reduction.
    EPA also evaluated whether health information is available 
regarding the potential health effects on children and other sensitive 
populations. Developmental studies with terbufos in rats and rabbits 
did not find any developmental effects (USEPA, 2003c). There are no 
data on reproductive and developmental effects for terbufos sulfone. No 
sensitive populations were identified or characterized. The OPP RED 
(USEPA, 2006c) presents more

[[Page 62741]]

detailed information about the potential health effects and sensitive 
populations for terbufos and terbufos sulfone.
e. Preliminary Regulatory Determination
    The agency is making preliminary determinations to not regulate 
terbufos and terbufos sulfone with NPDWRs after evaluating health, 
occurrence, and other related information against the three SDWA 
statutory criteria. While the data suggests that terbufos and terbufos 
sulfone may have adverse effects on human health, the occurrence data 
indicate there is no substantial likelihood that terbufos or terbufos 
sulfone will occur in PWSs with a frequency and at levels of public 
health concern. Therefore, the agency finds that NPDWRs for terbufos 
and terbufos sulfone would not present meaningful opportunities to 
reduce health risk for persons served by PWSs. The Regulatory 
Determinations 3 Support Document (USEPA, 2014b) presents additional 
information and/or analyses supporting the agency's evaluation of 
terbufos and terbufos sulfone.

V. What is the Status of the Agency's Evaluation of Chlorate and 
Nitrosamines?

    The agency will review the existing MDBP regulations as part of the 
SY3. Because chlorate and nitrosamines are 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.

A. Chlorate

    The following sections provide the background, health and 
occurrence information/data that the agency has collected to date for 
chlorate. If the public has any additional health and occurrence 
information that may be useful as the agency evaluates chlorate in the 
context of the existing MDBP rules, please provide this information to 
the docket.
1. Background
    The chlorate anion (ClO3-) forms a variety of 
salts (e.g., sodium chlorate, calcium chlorate, potassium chlorate, and 
magnesium chlorate) collectively known as chlorates, which are powerful 
oxidizers. Chlorate compounds (especially sodium chlorate) are used as 
herbicides and to generate chlorine dioxide (ClO2) as a 
bleaching agent (USEPA, 2006a). Disinfection practices are the most 
important source of chlorate in drinking water; this includes formation 
as a DBP from use of chlorine dioxide and its presence in hypochlorite 
disinfectants as an impurity (USEPA, 2006a).
    Chlorate can be formed during decomposition of hypochlorite 
(ClO-) solutions, which are used as a disinfectant and/or 
oxidant in water treatment. Hypochlorite solutions that are more aged 
are generally less effective and require higher doses to achieve the 
treatment (disinfection) objectives, which can result in more chlorate 
to be introduced into the chlorinated water. In addition to being a DBP 
(along with chlorite) formed from the use of chlorine dioxide as a 
disinfectant, chlorate ion may also be present as an impurity in the 
chlorine dioxide (Gates et al., 2009; USEPA, 2006a). Chlorate can also 
form by the reaction of chlorite with free chlorine applied as a 
residual disinfectant in the distribution system (Gallagher et al., 
1994). In addition, chlorite can be oxidized by a strong oxidant (such 
as ozone) to produce chlorate in the water (von Gunten, 2003). Chlorate 
salts readily dissolve in water and are highly mobile because of the 
absence. In the absence of redox reactions, the chlorate ion would be 
expected to partition predominantly into water and to be highly mobile 
in water. However, under most environmental conditions chlorate is 
subject to redox reactions, which are expected to reduce the 
concentration of chlorate in the water column (USEPA, 2006a).
2. Health Effects Information
    Acute ingestion of high levels of sodium chlorate has resulted in 
acute kidney failure and hemolysis among other effects based on 
numerous case reports of individuals accidently ingesting high levels 
of chlorate compounds (USEPA, 2006b; WHO, 2005). A population-based 
case-control study of chlorate as a DBP at concentrations >200 [mu]g/L 
identified significantly increased odds ratios for obstructive urinary 
defects, cleft palate, and spina bifida (Righi et al., 2012). The 
median chlorate exposure for the study population was 280 [mu]g/L. In a 
case-control study of the same population in Italy, Aggazzotti et al. 
(2004) found no association between preterm births and exposure to 
chlorate.
    The animal studies provide clear and consistent evidence that 
subchronic and chronic exposure to chlorate results in effects on blood 
and thyroid. Subchronic studies in rats have reported decreased 
hemoglobin, hematocrit, and red blood cell (RBC) counts (Abdel-Rahman 
et al., 1984; Barrett, 1987; McCauley et al., 1995) and thyroid colloid 
depletion, follicular cell hypertrophy and hyperplasia (Hooth et al., 
2001).
    A chronic study based on increased thyroid gland follicular cell 
hypertrophy in male rats (NTP, 2005a) was identified as the critical 
study for establishing an RfD of 0.03 mg/kg/day (USEPA, 2006b). The RfD 
was derived by using the BMD method and based on the lower 95% 
confidence limit (BMDL) of 28 mg/L as sodium chlorate (22 mg/L as 
chlorate), corresponding to 0.9 mg/kg/day (USEPA, 2006b), with a 
composite UF of 30 for intraspecies (i.e., sensitive populations) and 
interspecies variability (i.e., thyroid hormone differences between 
humans and rats). EPA calculated a non-cancer HRL of 210 [mu]g/L for 
chlorate using the RfD of 0.03 mg/kg/day for a 70 kg adult ingesting 2 
L of drinking water per day and an RSC of 20%.
    A cancer risk assessment was not conducted for chlorate because 
sodium chlorate is classified as not likely to be carcinogenic to 
humans at doses that do not alter thyroid hormone homeostasis under the 
USEPA (2005b) Cancer Guidelines. The RfD is protective against acute 
alterations in thyroid homeostasis and therefore considered to also be 
protective of tumorigenicity as well as other chronic and subchronic 
adverse health effects discussed in the literature (Hooth et al., 2001; 
Khan et al., 2005; NTP, 2005a).
    EPA also evaluated whether health information is available 
regarding sensitive populations. According to the OPP RED, there was no 
pre- or postnatal sensitivity or susceptibility observed in the 
submitted developmental studies in rats and rabbits or the 2-generation 
reproduction study in rats. However, there is a concern for developing 
offspring because of the effects of inorganic chlorate on thyroid 
function in rats (USEPA, 2006a). Chlorate is one of a number or 
inorganic ions that may interfere with iodine uptake by the thyroid, 
but chlorate is not highly potent in this respect (Van Sande et al., 
2003).
    Chlorate may also cause hemolysis, thus persons with low red blood 
cell counts such as those with anemia may be particularly sensitive to 
sodium chlorate. Data from the 1994 National Health Interview Survey 
(O'Day et al.,

[[Page 62742]]

1998) indicate that there were about 5 million people in the U.S. who 
suffered from some form of anemia. About 3 to 5% of the population may 
have an inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency, 
with males more sensitive than females (Luzzatto and Mehta, 1989), and 
about 1% may have a form of hereditary methemoglobinemia (Jaffe and 
Hultquist, 1989). Each one of these conditions is a contributor to low 
red blood cell counts within the population. Individuals co-exposed to 
other ions that decrease iodine uptake by the thyroid or have low RBC 
counts may be more sensitive to chlorate exposure.
3. Occurrence Data and Information
a. Drinking Water
    The 1997-1998 DBP ICR is currently the best available data source 
for characterizing the national occurrence baseline for chlorate. The 
DBP ICR, which included monitoring data for 296 water systems serving 
100,000 people or more (representing a total population of 130 
million), required water systems that use hypochlorite solutions or 
chlorine dioxide for disinfection to monitor for chlorate (USEPA, 
1996). Subsequently, 82 water systems serving approximately 40 million 
people monitored and reported chlorate occurrence under the DBP ICR 
(using an MRL of 20 [mu]g/L). Table 9 presents the number and 
percentage of samples and systems (along with the population served) 
that measured chlorate at levels exceeding the specified threshold 
concentrations (i.e., HRL and \1/2\ HRL). These samples were associated 
with 41.5% (34 of 82) of the ICR systems using hypochlorite solutions 
or chlorine dioxide for disinfection and 11.5% (34 of 296) of all of 
the ICR systems. EPA assumes there was no occurrence of chlorate among 
the ICR systems that were not required to monitor for it, since they 
use disinfection techniques not expected to produce chlorate. 
Approximately 51.1% (878 of 1,719) of ICR samples from the finished 
water or distribution system of the systems required to monitor had 
chlorate at levels greater than the \1/2\ HRL (105 [mu]g/L) and 19.3% 
(332 of 1,719) had chlorate at levels greater than the HRL (210 [mu]g/
L). The samples greater than the \1/2\ HRL were associated with 73.2% 
(60 of 82) of the ICR systems using hypochlorite solutions or chlorine 
dioxide for disinfection and 20.3% (60 of 296) of all ICR systems 
(including those that were not required to monitor for chlorate). The 
samples greater than the HRL were associated with 41.5% (34 of 82) of 
the ICR systems using hypochlorite solutions or chlorine dioxide for 
disinfection and 11.5% (34 of 296) of all ICR systems (including those 
that were not required to monitor for chlorate) (McGuire et al., 2002).
    Since the DBP ICR was completed in 1998, these data likely 
underestimate current (2012) chlorate occurrence among the systems 
serving 100,000 people or more for the following two reasons: (1) Some 
of these systems may have changed the disinfectant type from chlorine 
gas to chlorine dioxide for compliance with the existing Stage 1 or 
Stage 2 DBP rules; and/or (2) some systems may have switched from 
chlorine gas to hypochlorite solution due to a security concern (i.e., 
a concern of safety of transportation and storage for chlorine gas). 
Disinfection surveys conducted by the AWWA Disinfection Systems 
Committee in 1998 and 2007 have confirmed that chlorine dioxide and 
hypochlorite use has increased (AWWA Disinfection Systems Committee, 
2008a, 2008b; Connell et al., 2000a, 2000b).

                                            Table 9--Summary of Chlorate Monitoring Results Under the DBP ICR
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Of DBP ICR PWSs that monitored for chlorate,   Of all DBP ICR PWSs, PWSs with at least one
                                                              samples and PWSs with at least one detection       detection > threshold and estimated
                                                                              > threshold *                             population served **
                                                             -------------------------------------------------------------------------------------------
                     Chlorate threshold                                                                      Number (percentage)
                                                               Number (percentage)    Number (percentage)    of DBP ICR PWSs with   Population served by
                                                                of DBP ICR samples    of DBP ICR PWSs with       at least one       DBP ICR PWSs with at
                                                                 with detection >         at least one      detection > threshold  least one detection >
                                                                    threshold        detection > threshold           \*\               threshold \**\
--------------------------------------------------------------------------------------------------------------------------------------------------------
HRL (210 [mu]g/L)...........................................          332 of 1,719               34 of 82              34 of 296    11.8 of 130 million
                                                                           (19.3%)                (41.5%)                (11.5%)                 (9.1%)
\1/2\ HRL (105 [mu]g/L).....................................          878 of 1,719               60 of 82              60 of 296    31.7 of 130 million
                                                                           (51.1%)                (73.2%)                (20.3%)                (24.4%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\*\ 82 PWSs that used hypochlorite or chlorine dioxide were required to monitor for chlorate during the DBP ICR monitoring period, based on their
  potential to form chlorate. Number and percentage of samples and PWSs are based on those 82 PWSs that monitored for chlorate.
\**\ The number and percentage of PWSs and population served > threshold is based on all 296 systems. EPA assumes that the 214 systems not required to
  monitor do not have chlorate concentrations above the thresholds.

    Finished water data for chlorate from California collected between 
2001 and 2007 show lower occurrence compared to the DBP ICR. The State 
of California reported results from testing more than 1,200 drinking 
water samples from 45 PWSs and chlorate was detected in 945 samples 
(78.4%) from 24 different systems (53.3%) (Ranalli, B., 2013). 
Approximately 41.6% (501 of 1,205) of samples from 17 systems (37.8%) 
had chlorate at levels greater than the \1/2\ HRL (105 [mu]g/L) and 
approximately 12.4% (149 of 1,205) of samples from 10 systems (22.2%) 
had chlorate at levels greater than the HRL (210 [mu]g/L) (Ranalli, B., 
2013).
    It is important to note that the agency included chlorate in the 
UCMR 3, which is currently in process. UCMR 3 will provide a national 
dataset of chlorate occurrence in drinking water and will update the 
occurrence data provided by the DBP ICR.
    Ambient water data for chlorate are limited, but chlorate could be 
present in areas where it is used as an herbicide or discharged from 
paper plants where it is used as a bleaching agent. Since chlorate is a 
DBP, higher concentrations are expected in finished water than in 
ambient water.
b. Exposure from media other than water
    There is very little quantitative information available on the 
occurrence of chlorate in food, air, and soil or other products 
resulting in residential exposures. Without reliable estimates of 
intakes, it is not possible to estimate the contribution of drinking 
water to total exposure. However, based on modeling results, the agency 
estimated that the chlorate intake from food (as a result of sodium 
chlorate use as a pesticide) for the overall population is 
approximately 3 [mu]g/kg-day, with somewhat higher intakes for children 
under five years old

[[Page 62743]]

of approximately 5 to 8 [mu]g/kg-day (USEPA, 2006a). Additional food 
exposure from use of sanitizing solutions in food preparation plants 
(e.g., equipment and contact surfaces) and processing (e.g., bleaching 
agent) may also be a source of exposure (21 CFR section 178.1010). 
Intake for adults from dietary supplements containing chlorate may 
range from 0.001 to 0.29 [mu]g/kg-day.

B. Nitrosamines Group (6 Nitrosamines)

    The following sections provide the background, health and 
occurrence information/data that the agency has collected to date for 
nitrosamines. If you have any additional health and occurrence 
information that may be useful as the agency evaluates nitrosamines in 
the context of the regulatory review of existing MDBP rules, please 
provide this information to the docket.
1. Background
    Nitrosamines are a class of nitrogen-containing organic compounds 
that share a common nitrosamino functional group (HSDB, 2010). EPA 
included five nitrosamine compounds on the CCL 3: N-
nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodi-
n-propylamine (NDPA), N-nitrosopyrrolidine (NPYR), and N-
nitrosodiphenylamine (NDPhA). EPA monitored six nitrosamines under UCMR 
2 using EPA Analytical Method 521, four of which are CCL 3 compounds 
(i.e., NDMA, NDEA, NDPA, NPYR), and two non-CCL 3 nitrosamines [i.e., 
N-nitrosomethylethylamine (NMEA) and N-nitrosodi-n-butylamine (NDBA)]. 
The fifth CCL 3 nitrosamine compound, NDPhA, was not monitored under 
UCMR 2 due to lack of a reliable analytical method. Although other 
nitrosamines (e.g., N-nitrosomorpholine, N-nitrosopiperidine) have been 
identified in finished water (Mitch et al., 2009), they were also not 
included in UCMR 2 for similar analytical reasons. The nitrosamines 
from the UCMR 2 thus comprise the list of six nitrosamines that moved 
forward to the data evaluation phase of regulatory determination and 
are the focus of the information that follows below.
    All six nitrosamines may be produced in small quantities for 
research purposes, but only one (NDEA) is currently produced 
commercially in the United States. NDEA is used as an additive in 
gasoline and in lubricants, as an antioxidant, and as a stabilizer in 
plastics, though no data are available about quantities used (HSDB, 
2010). NDMA was once used in the production of rocket fuel, as a 
solvent, and as a rubber accelerator. It was also used or proposed for 
use as an antioxidant, an additive for lubricants, and a softener for 
copolymers (ATSDR, 1989). There are no production data on any of the 
nitrosamine compounds from EPA's Inventory Update Reporting (IUR) 
program.
    NDMA can be formed as an unintended byproduct of manufacturing 
processes that involve the use of nitrite or nitrate and amines, 
including tanneries, fish processing plants, foundries, and pesticide, 
dye, rubber or tire manufacturing plants (ATSDR, 1989). Nitrosamines 
have been found in tobacco products, cured meats, ham, bacon, beer, 
whiskey, fish, cheese, soybean oil, toiletries, household cleaners, 
pesticides, rubber baby bottle nipples and pacifiers (ATSDR, 1989; 
Drabik-Markiewicz et al., 2009; Fine et al., 1977; NTP, 2011; 
P[eacute]rez et al., 2008; Yurchenko and M[ouml]lder, 2007).
    NDMA is commonly present in municipal sewage sludge (ATSDR, 1989). 
NPYR has also been detected in municipal sewage sludge (HSDB, 2010). 
ATSDR (1989) cites several studies indicating that nitrosamine 
formation in sewage sludge appears to be the result of biological and 
chemical transformation of alkylamines in the presence of nitrite. In 
addition, nitrosamines may form in air, soil, water, sewage, food, 
animal systems and other media where precursors (e.g., amines and 
nitrite) are present (HSDB, 2010). NDMA can be produced endogenously in 
humans from the interaction of nitrates and nitrites with amines in the 
stomach (Mirvish 1975, 1992; Tricker et al., 1994).
    As described in the following occurrence section, nitrosamines in 
finished water are commonly considered as DBPs because most of the 
literature indicates that the main source of nitrosamines in finished 
water is associated with water treatment, particularly from 
disinfection with chloramines. NDMA is the predominant species of 
nitrosamines found in finished water; other nitrosamines are detected 
less frequently. Based on their physical and chemical properties, the 
nitrosamines appear to be moderately to very mobile in the environment 
(the exception being NDBA, which is of low mobility). The nitrosamines 
are subject to a variety of removal mechanisms when present in soil and 
water, including volatilization (particularly NDMA), photodegradation, 
and microbial degradation, although the rates and extent of 
biodegradation are highly variable (HSDB, 2010).
2. Health Effects Information
    As the more thoroughly studied nitrosamine compared to the other 
nitrosamine compounds, NDMA provides epidemiological case-control and 
other evidence that human nitrosamine exposure is associated with an 
increased risk of several types of cancer, including cancer of the 
stomach, esophagus, oral cavity, and pharynx (La Vecchia et al., 1995; 
Larsson et al., 2006; Loh et al., 2011; Straif et al., 2000). In 
accordance with the most recent Guidelines for Carcinogen Risk 
Assessment (USEPA, 2005b), EPA has categorized the six nitrosamine 
compounds as likely to be carcinogenic to humans based on sufficient 
evidence of carcinogenicity in animal studies with multiple tumor types 
(predominately liver and esophageal) in multiple animal species (e.g., 
rats, mice, and hamsters) (Clapp et al., 1968, 1971; Druckrey et al., 
1967; Lijinsky, 1987a, 1987b; Peto et al., 1991a, 1991b). All of the 
six nitrosamines have been determined to cause cancer through a 
mutagenic MOA because of DNA adduct formation leading to errors in DNA 
replication, altered cell proliferation and ultimately tumors (Diaz 
Gomez et al., 1986; Goto et al., 1999; Jarabek et al., 2009; Souliotis 
et al., 1998). The mutagenic MOA is supported by positive findings from 
mutagenicity and genotoxicity in vitro and in vivo studies (Gollapudi 
et al., 1998; Kushida et al., 2000; Martelli et al., 1988, Robbiano et 
al., 1996, Tinwell et al., 1994).
    With a mutagenic MOA, Age Dependent Adjustment Factors (ADAFs) are 
used to account for the potential increased cancer risk due to early-
life exposure for infants and children (USEPA, 2005c). The age-adjusted 
unit risk is determined by summing up each of the time-weighted unit 
risks for the three ADAF developmental groups. The age-adjusted unit 
risks include a ten-fold adjustment for birth to 
         Nitrosamines            establishing a   factor (mg/kg/  risk ([mu]g/L)-       L)        \3\ HRL (ng/L)
                                  slope factor        day)-1             1
----------------------------------------------------------------------------------------------------------------
NDBA..........................  Liver and                    0.4      3.0 x 10-5        3 x 10-2              30
                                 esophageal
                                 tumors in rats
                                 (Druckrey et
                                 al., 1967).
NDEA..........................  Liver and                     30      2.3 x 10-3        4 x 10-4             0.4
                                 esophageal
                                 tumors in rats
                                 (Peto et al.,
                                 1991a,b).
NDMA..........................  Liver tumors in               21      1.6 x 10-3        6 x 10-4             0.6
                                 rats (Peto et
                                 al., 1991a,b).
NDPA..........................  Liver and                      2      1.5 x 10-4        7 x 10-3               7
                                 esophageal
                                 tumors in rats
                                 (Druckrey et
                                 al., 1967).
NMEA..........................  Liver tumors in                4      3.0 x 10-4        3 x 10-3               3
                                 rats (Druckrey
                                 et al., 1967).
NPYR..........................  Liver tumors in                7      5.3 x 10-4        2 x 10-3               2
                                 rats (Peto et
                                 al., 1984).
----------------------------------------------------------------------------------------------------------------
\1\ Based on the recommendations of the U.S EPA's 2005 Supplemental Guidance for Assessing Susceptibility from
  Early-Life Exposure to Carcinogens, the Unit Risk applicable to exposures beginning in early-life was adjusted
  with ADAFs and age-specific drinking water intakes resulting in a lifetime value of unit risk for exposure to
  1 [mu]g/L of a contaminant. The calculation for Age-Adjusted Unit Risk = [sum](CSF x ADAF x DWI/BWR x CW x F).
  The risk calculations for each individual nitrosamine can be found in the HESDs.
\2\ The cancer HRL is determined by dividing the population risk level, one-in a million (10-6), by the age-
  adjusted unit risk.
\3\ The nitrosamine HRL values are converted to ng/L units by multiplying the [mu]g/L values by 1000.

    As shown in table 10, the available data indicate a range of cancer 
risk values for the individual nitrosamines. Moreover, when multiple 
nitrosamines from this group are present in finished water together, 
their individual cancer risks are additive (Berger et al., 1987).
    EPA also evaluated whether health information is available 
regarding sensitive populations. The fetus, newborns, and infants may 
be potentially sensitive to the carcinogenic effects of nitrosamines 
due to the mutagenic MOA and evidence of transplacental carcinogenicity 
(Althoff et al., 1977; Donovan and Smith, 2008). Studies have found 
that younger rats were more susceptible to the development of liver 
tumors compared to rats exposed later in life to nitrosamines (Gray et 
al., 1991; Peto et al., 1984; Vesselinovitch et al., 1984). EPA's 
Supplemental Guidance for Assessing Susceptibility from Early-Life 
Exposure to Carcinogens (USEPA, 2005c) indicates that potential 
increased cancer risk due to early-life exposure should be taken into 
account for such compounds when there is the potential for greater 
susceptibility for structural changes to DNA leading to tumors when the 
exposures occur in infancy or childhood. Thus, the Supplemental 
Guidance (USEPA, 2005c) recommends using CSF estimates from chronic 
studies with ADAFs when chemical-specific data that quantify the 
potential increased risk are lacking. All of the HRLs are based on 
lifetime exposure and include application of ADAFs, which adjust for 
the increased risk from early life exposure (see section III.C.1).
    In addition, habitual consumers of alcoholic beverages may be more 
susceptible to carcinogenic effects of nitrosamines because alcohol 
increases the metabolism of nitrosamines via a metabolic pathway that 
leads to the formation of mutagenic DNA adducts. Co-exposure to ethanol 
has been shown to exacerbate the cancer effects of nitrosamines in 
animal studies (Anderson et al., 1993; Kamataki et al., 2002; McCoy et 
al., 1986). There are approximately five million people in the U.S. who 
suffer from alcoholism (O'Day et al., 1998) that may have an increased 
risk if co-exposed to nitrosamines (Amelizad et al., 1989; Verna et 
al., 1996).
3. Occurrence Data and Information
    The data collected under UCMR 2 (USEPA, 2014d) are currently the 
best available data for characterizing the national occurrence 
baselines for the six nitrosamines. Under UCMR 2, PWSs were required to 
collect a sample at each entry point to the distribution system as well 
as at the maximum residence time locations within the distribution 
system associated with each entry point, and to report the disinfectant 
type in use at these locations at the time that the samples were being 
taken. The agency was unable to measure at the HRL for some of the 
nitrosamines. Therefore, Table 11 presents all of the monitoring 
results for each of the six nitrosamines relative to the MRLs.

                                           Table 11--Summary of UCMR 2 Monitoring Results for Six Nitrosamines
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                 Percentages (number) of
                                                                             Percentages (number) of   Percentages (number) of  actual UCMR 2 population
             Nitrosamines considered under RD 3                    MRL       samples with detection      UCMR 2 PWSs with at    served with at least one
                                                                                                         least one detection           detection*
--------------------------------------------------------------------------------------------------------------------------------------------------------
Nitrosamine Group...........................................  2 to 7 ng/L                     10.6%                     28.6%                    46.43%
                                                                                  (1,907 of 18,053)            (343 of 1,198)       (73 of 157 million)
NDBA........................................................       4 ng/L                     0.05%                      0.4%                     1.07%
                                                                                      (9 of 18,043)              (5 of 1,198)      (1.7 of 157 million)
NDEA........................................................       5 ng/L                      0.3%                      2.2%                     7.14%
                                                                                     (46 of 18,038)             (26 of 1,198)     (11.2 of 157 million)
NDMA........................................................       2 ng/L                     10.2%                     27.0%                    41.54%
                                                                                  (1,841 of 18,040)            (324 of 1,198)     (65.3 of 157 million)
NDPA........................................................       7 ng/L                        0%                        0%                        0%
                                                                                      (0 of 18,049)              (0 of 1,198)        (0 of 157 million)
NMEA........................................................       3 ng/L                     0.02%                       0.3                    0.003%
                                                                                      (3 of 18,043)              (3 of 1,198)    (0.004 of 157 million)
NPYR........................................................       2 ng/L                      0.2%                      1.8%                     4.73%
                                                                                     (41 of 18,043)             (21 of 1,198)      (7.4 of 157 million)
--------------------------------------------------------------------------------------------------------------------------------------------------------
* The population-served values have been adjusted to include both the population served directly by a system and also the estimated attributable
  proportion of the population served by other systems that purchase water from the system. These adjustments are described in the UCMR 2 support
  document.

[[Page 62745]]

    Finished water data for the nitrosamines from California (Ranalli, 
B., 2013) are consistent with the UCMR 2 data. The State of California 
reported NDMA detections in 23.8% (24 of 101) of PWSs and NDEA 
detections in 7.1% (1 of 14) of PWSs. There were no NPYR, NDPA, NMEA, 
or NDBA detections reported. Reporting levels are not known. For 
California data on NDMA and NDEA, the minimum reported detections were 
1 ng/L and 30 ng/L, respectively. NDBA, NDPA, NMEA, and NPYR had no 
detections and thus no minimum reported value in the dataset (Ranalli, 
B., 2013). While ambient water data for the nitrosamines are limited, 
because they are DBPs, it is expected that in general there would be 
higher concentrations in finished water than in ambient water.

V. What about the remaining CCL 3 contaminants?

    For the remaining CCL 3 contaminants, the agency lacked adequate 
health and/or occurrence information needed to address the three SDWA 
statutory criteria to make a regulatory determination. Table 2 and 
Table 4 of this notice provide information about the data or 
information gap(s) that prevented the contaminant from moving forward 
for this regulatory determination effort. The agency continues to 
conduct research, collect information or find other avenues to fill the 
data and information gaps identified in Table 2 and 4. One mechanism 
the agency plans to continue to use to fill occurrence gaps for several 
of these contaminants is the UCMR.

VI. EPA's Next Steps

    EPA intends to carefully evaluate and respond to the public 
comments received on the five preliminary determinations and issue its 
final regulatory determinations in 2015. If the agency makes a final 
determination to regulate any of the contaminants, EPA will begin the 
process to propose an NPDWR within 24 months and promulgate a final 
NPDWR within 18 months following the proposal.

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    Dated: October 3, 2014.
Gina A. McCarthy,
Administrator.

Appendix: HRL Derivation With Age-Related Exposure Factors

        Derivation of the Health Reference Level (HRL) for Strontium Using Age-Specific Exposure Factors
----------------------------------------------------------------------------------------------------------------
                                                                 Age-specific fractions
              Age range                  DWI/BWR  (L/kg/day)     of a 19-year exposure    Time-weighted DWI/BWR
                                                                        duration                (L/kg/day)
----------------------------------------------------------------------------------------------------------------
Birth to BWRs =..............................................         0.040 L/kg/day *
----------------------------------------------------------------------------------------------------------------
Reference Dose =.......................................................................            0.3 mg/kg/day
----------------------------------------------------------------------------------------------------------------
RSC =..................................................................................                      20%
----------------------------------------------------------------------------------------------------------------
\+\HRL = (0.3 mg/kg/day / 0.040 L/kg/day) x .20 =......................................               1.500 mg/L
----------------------------------------------------------------------------------------------------------------
Final child specific HRL:..............................................................             1500 [mu]g/L
----------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------
* Rounded; # includes 18th year; DWI/BWR = drinking water intake to body weight ratio; HRL= health reference
  level; RSC = relative source contribution.
\+\ HRL = (RfD/[sum](DWI/BWR x F)) x RSC.

[[Page 62750]]

    The age-specific data on drinking water intakes in units of L/kg/
day from birth through age 3 are from Table 3-19 in the EPA Exposures 
Factors Handbook (USEPA, 2011e) and from Table 3-38 for ages 3 to 12)/19 years = 
0.00439; 6 to 19 years = 0.26316). The time-weighted DWI/
BWR values are the product of the age-specific DWI/BWR multiplied by 
the age-specific fraction of a 19 year exposure. The time-weighted DWI/
BWRs are summed to obtain the normalized value.
[FR Doc. 2014-24582 Filed 10-17-14; 8:45 am]
BILLING CODE 6560-50-P
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