[Federal Register Volume 85, Number 47 (Tuesday, March 10, 2020)]
[Proposed Rules]
[Pages 14098-14142]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-04145]
[[Page 14097]]
Vol. 85
Tuesday,
No. 47
March 10, 2020
Part IV
Environmental Protection Agency
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40 CFR Part 141
Announcement of Preliminary Regulatory Determinations for Contaminants
on the Fourth Drinking Water Contaminant Candidate List; Proposed Rule
Federal Register / Vol. 85, No. 47 / Tuesday, March 10, 2020 /
Proposed Rules
[[Page 14098]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 141
[EPA-HQ-OW-2019-0583; FRL-10005-88-OW]
Announcement of Preliminary Regulatory Determinations for
Contaminants on the Fourth 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. A
preliminary regulatory determination lays out and takes comment on
EPA's view about whether certain unregulated contaminants meet three
statutory criteria. After EPA considers public comment, EPA makes a
final determination. The unregulated contaminants included in a
regulatory determination are chosen from the Contaminant Candidate List
(CCL), which the SDWA requires the EPA to publish every five years. The
EPA published the fourth CCL (CCL 4) in the Federal Register on
November 17, 2016. This document presents the preliminary regulatory
determinations and supporting rationale for the following eight of the
109 contaminants listed on CCL 4: Perfluorooctanesulfonic acid (PFOS),
perfluorooctanoic acid (PFOA), 1,1-dichloroethane, acetochlor, methyl
bromide (bromomethane), metolachlor, nitrobenzene, and Royal Demolition
eXplosive (RDX). The Agency is making preliminary determinations to
regulate two contaminants (i.e., PFOS and PFOA) and to not regulate six
contaminants (i.e., 1,1-dichloroethane, acetochlor, methyl bromide,
metolachlor, nitrobenzene, and RDX). The EPA seeks comment on these
preliminary determinations. The EPA is also presenting an update on
three other CCL 4 contaminants (strontium, 1,4-dioxane, and 1,2,3-
trichloropropane).
DATES: Comments must be received on or before May 11, 2020.
ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OW-2019-0583, by any of the following methods:
Federal eRulemaking Portal: https://www.regulations.gov/
(our preferred method). Follow the online instructions for submitting
comments.
Mail: Water Docket, Environmental Protection Agency, Mail
Code: [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: All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to https://www.regulations.gov/, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the ``Written Comments''
heading of the SUPPLEMENTARY INFORMATION section of this document.
FOR FURTHER INFORMATION CONTACT: Richard Weisman, Standards and Risk
Management Division, Office of Ground Water and Drinking Water, MC:
4607M, Environmental Protection Agency, 1200 Pennsylvania Ave. NW;
telephone number: (202) 564-2822; email address:
[email protected].
SUPPLEMENTARY INFORMATION:
I. General Information
A. Written Comments
Submit your comments, identified by Docket ID No. EPA-HQ-OW-2019-
0583, at https://www.regulations.gov (our preferred method), or the
other methods identified in the ADDRESSES section. Once submitted,
comments cannot be edited or removed from the docket. The EPA may
publish any comment received to its public docket. Do not submit
electronically any information you consider to be Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Multimedia submissions (audio, video, etc.) must be
accompanied by a written comment. The written comment is considered the
official comment and should include discussion of all points you wish
to make. The EPA will generally not consider comments or comment
contents located outside of the primary submission (i.e., on the web,
cloud, or other file sharing system). For additional submission
methods, the full EPA public comment policy, information about CBI or
multimedia submissions, and general guidance on making effective
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
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.
B. 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 the EPA's
preliminary regulatory determinations for eight unregulated
contaminants for comment.
Abbreviations Used in This Document
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Abbreviation Meaning
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ADAF................................ Age Dependent Adjustment Factor
ADONA............................... 4,8-dioxa-3H-perfluorononanoic
acid
ALT................................. Alanine Aminotransferase
AM.................................. Assessment Monitoring
AOP................................. Advanced Oxidative Process
ASDWA............................... Association of State Drinking
Water Administrators
ATSDR............................... Agency for Toxic Substances and
Disease Registry
AWIA................................ America's Water Infrastructure Act
BAT................................. Best Available Technology
BMD................................. Benchmark Dose
BMDL................................ Benchmark Dose Level
BMDS................................ Benchmark Dose Software
BMR................................. Benchmark Response
BW.................................. Body Weight
CAR................................. Constitutive Androstane Receptor
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
CCL 4............................... Fourth Contaminant Candidate List
CDPHE............................... Colorado Department of Public
Health and Environment
CDR................................. Chemical Data Reporting
CIIT................................ Chemical Industry Institute of
Toxicology
CNS................................. Central Nervous System
cPAD................................ Chronic Population Adjusted Dose
CRL................................. Cancer Risk Level
CSF................................. Cancer Slope Factor
[[Page 14099]]
CWS................................. Community Water System
CWSS................................ Community Water System Survey
D/DBP............................... Disinfectants/Disinfection
Byproducts
DBP................................. Disinfection Byproduct
DDE................................. 1,1-Dichloro-2,2-bis(p-
chlorophenyl)ethylene
DWI................................. Drinking Water Intake
EPA................................. Environmental Protection Agency
EPCRA............................... Emergency Planning and Community
Right-To-Know Act
EPTC................................ S-Ethyl dipropylthiocarbamate
ESA................................. Ethanesulfonic Acid
FtOH 6:2............................ 6:2 Fluorotelomer Alcohol
FtOH 8:2............................ 8:2 Fluorotelomer Alcohol
FtS 6:2............................. 6:2 Fluorotelomer Sulfonic Acid
FtS 8:2............................. 8:2 Fluorotelomer Sulfonic Acid
FQPA................................ Food Quality Protection Act
FR.................................. Federal Register
HA.................................. Health Advisory
HDL................................. High-Density Lipoprotein
HED................................. Human Equivalent Dose
HERO................................ Health and Environmental Research
Online
HESD................................ Health Effects Support Document
HFPO................................ Hexafluoropropylene Oxide
HHRA................................ Human Health Risk Assessment
HRL................................. Health Reference Level
IARC................................ International Agency for Research
on Cancer
ICR................................. Information Collection Rule
IOC................................. Inorganic Compound
IRED................................ Interim Reregistration Eligibility
Decision
IRIS................................ Integrated Risk Information System
IUR................................. Inventory Update Reporting
KH.................................. Henry's Law Constant
Koc................................. Organic Carbon Partitioning
Coefficients
LOAEL............................... Lowest Observed Adverse Effect
Level
log Kow............................. Octanol-Water Partitioning
Coefficient
MCL................................. Maximum Contaminant Level
MCLG................................ Maximum Contaminant Level Goal
metHB............................... Methemoglobin
MOA................................. Mode of Action
MRL................................. Minimum Reporting Level
NAM................................. New Approach Method
NAS................................. National Academy of Sciences
NAWQA............................... National Water Quality Assessment
NCDEQ............................... North Carolina Department of
Environmental Quality
NCFAP............................... National Center for Food and
Agricultural Policy
NCI................................. National Cancer Institute
NDEA................................ N-Nitrosodiethylamine
NDMA................................ N-Nitrosodimethylamine
NDPA................................ N-Nitroso-di-n-propylamine
NDPhA............................... N-Nitrosodiphenylamine
NDWAC............................... National Drinking Water Advisory
Council
NEtFOSAA............................ 2-(N-
Ethylperfluorooctanesulfonamido)
acetic acid
NHDES............................... New Hampshire Department of
Environmental Services
NIEHS............................... National Institute of
Environmental Health Sciences
NIRS................................ National Inorganics and
Radionuclides Survey
NMeFOSAA............................ 2-(N-
Methylperfluorooctanesulfonamido)
Acetic Acid
NOAEL............................... No Observed Adverse Effect Level
NPDWR............................... National Primary Drinking Water
Regulation
NPYR................................ N-Nitrosopyrrolidine
NRC................................. National Research Council
NTP................................. National Toxicology Program
NWIS................................ National Water Information System
OA.................................. Oxanilic Acid
OPP................................. Office of Pesticides Program
ORD................................. Office of Research and Development
OTC................................. Ornithine Carbamoyl Transferase
OW.................................. Office of Water
PCCL................................ Preliminary Contaminant Candidate
List
PDP................................. Pesticide Data Program
PFAA................................ Perfluorinated Alkyl Acids
PFAS................................ Per- and Polyfluoroalkyl
Substances
PFBA................................ Perfluorobutanoic Acid
PFBS................................ Perfluorobutanesulfonic Acid
PFDA................................ Perfluorodecanoic Acid
PFDS................................ Perfluorodecanesulfonic Acid
PFHpA............................... Perfluoroheptanoic Acid
PFHpS............................... Perfluoroheptanesulfonic Acid
PFHxA............................... Perfluorohexanoic Acid
PFHxS............................... Perfluorohexanesulfonic Acid
PFNA................................ Perfluorononanoic Acid
PFNS................................ Perfluorononanesulfonic Acid
PFOA................................ Perfluorooctanoic Acid
PFOS................................ Perfluorooctanesulfonic Acid
PFOSA............................... Perfluorooctanesulfonamide
PFPeA............................... Perfluoropentanoic Acid
PFPeS............................... Perfluoropentanesulfonic Acid
PFTeDA.............................. Perfluorotetradecanoic Acid
PFUnA............................... Perfluoroundecanoic Acid
PMP................................. Pesticide Monitoring Program
POD................................. Point of Departure
PPRTV............................... Provisional Peer-Reviewed Toxicity
Value
PST................................. Pre-Screen Testing
PWS................................. Public Water System
QA.................................. Quality Assurance
RD 1................................ Regulatory Determination 1
RD 2................................ Regulatory Determination 2
RD 3................................ Regulatory Determination 3
RD 4................................ Regulatory Determination 4
RDX................................. Royal Demolition eXplosive
RED................................. Reregistration Eligibility
Decision
RfD................................. Reference Dose
RSC................................. Relative Source Contribution
SD.................................. Standard Deviation
SDWA................................ Safe Drinking Water Act
SS.................................. Screening Survey
SSCT................................ Small System Compliance Technology
STORET.............................. Storage and Retrieval Data System
TOF................................. Total Organic Fluorine
TOP................................. Total Organic Precursor
TPTH................................ Triphenyltin Hydroxide
TRED................................ Tolerance Reassessment Progress
and Risk Management Decision
TRI................................. Toxic Release Inventory
TSCA................................ Toxic Substances Control Act
TT.................................. Treatment Technique
UCM................................. Unregulated Contaminant Monitoring
UCMR................................ Unregulated Contaminant Monitoring
Rule
UCMR 1.............................. First Unregulated Contaminant
Monitoring Rule
UCMR 2.............................. Second Unregulated Contaminant
Monitoring Rule
UCMR 3.............................. Third Unregulated Contaminant
Monitoring Rule
UF.................................. Uncertainty Factor
UNEP................................ United Nations Environmental
Programme
USDA................................ United States Department of
Agriculture
USGS................................ United States Geological Survey
VOC................................. Volatile Organic Compound
WHO................................. World Health Organization
WQP................................. Water Quality Portal
WQX................................. Water Quality Exchange
5:3 acid............................ 2H,2H,3H,3H-Perfluorooctanoic acid
6:2 diPAP........................... Bis[2-(perfluorohexyl)ethyl]
phosphate
6:2 monoPAP......................... Mono[2-(perfluorohexyl)ethyl]
phosphate
6:2/8:2 diPAP....................... 6:2/8:2 Fluorotelomer phosphate
diester
8:2 diPAP........................... Bis[2-(perfluorooctyl)ethyl]
phosphate
8:2 monoPAP......................... Mono[2-(perfluorooctyl)ethyl]
phosphate
------------------------------------------------------------------------
Table of Contents
I. General Information
A. Written Comments
B. Does this action apply to me?
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
Determination (RD 1)
3. The Second Contaminant Candidate List (CCL 2) and Regulatory
Determination (RD 2)
4. The Third Contaminant Candidate List (CCL 3) and Regulatory
Determination (RD 3)
5. The Fourth Contaminant Candidate List (CCL 4) and Regulatory
Determination (RD 4)
III. Approach and Overall Outcomes for RD 4
A. Summary of the Approach and Overall Outcomes for RD 4
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 Determination
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 4 Preliminary
Determination
A. Summary of the Preliminary Regulatory Determination
B. Contaminant Profiles
1. PFOA and PFOS
2. 1,1-Dichloroethane
3. Acetochlor
4. Methyl Bromide (Bromomethane)
5. Metolachlor
6. Nitrobenzene
7. RDX
V. Status of the Agency's Evaluation of Strontium, 1,4-Dioxane, and
1,2,3-Trichloropropane
A. Strontium
B. 1,4-Dioxane
C. 1,2,3-Trichloropropane
VI. EPA's Request for Comments and Next Steps
VII. References
[[Page 14100]]
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 request comment on the
Environmental Protection Agency's (EPA's) preliminary regulatory
determinations for the following eight unregulated contaminants:
Perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA),
1,1-dichloroethane, acetochlor, methyl bromide (bromomethane),
metolachlor, nitrobenzene, and RDX. The Agency is making preliminary
determinations to regulate two contaminants (PFOS and PFOA) and to not
regulate the remaining six contaminants (1,1-dichloroethane,
acetochlor, methyl bromide, metolachlor, nitrobenzene, and RDX). As
described in Section III.A.3, if the EPA finalizes these preliminary
regulatory determinations, it would represent the beginning of the
Agency's regulatory development process, not the end. As required by
SDWA, the EPA seeks comment on these preliminary determinations and is
asking for information and comment on other per- and polyfluoroalkyl
substances (PFAS) and potential regulatory approaches. The Agency is
also requesting comment on the process and analyses used for this round
of regulatory determinations (i.e., RD 4), the supporting information,
additional studies or sources of information the Agency should
consider, and the rationale used to make these preliminary decisions.
The EPA is also presenting an update on strontium (from the third
regulatory determination) and two other CCL 4 contaminants for which
the Agency is not making preliminary determinations today (1,4-dioxane
and 1,2,3-trichloropropane).
It should be noted that the analyses associated with a regulatory
determination process are distinct from the analyses needed to develop
a National Primary Drinking Water Regulation (NPDWR). Thus, a decision
to regulate is the beginning of the Agency's regulatory development
process, not the end. For example, the EPA may find at a later point in
the regulatory development process, and based on additional or new
information, that a contaminant does not meet the three statutory
criteria for finalizing a NPDWR.
B. Background on the CCL and Regulatory Determinations
1. Statutory Requirements for CCL and Regulatory Determinations
Section 1412(b)(1)(B)(i) of the SDWA requires the EPA to publish
the CCL every five years after public notice and an opportunity to
comment. The CCL is a list of contaminants which are not subject to any
proposed or promulgated NPDWRs but are known or anticipated to occur in
public water systems (PWSs) and may require regulation under the SDWA.
SDWA section 1412(b)(1)(B)(ii) directs the EPA to determine, after
public notice and an opportunity to comment, whether to regulate at
least five contaminants from the CCL every five years. Under Section
1412(b)(1)(A) of SDWA, the EPA makes a determination to regulate a
contaminant in drinking water if the Administrator determines 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 the EPA determines that these three statutory criteria are met
and makes a final determination to regulate a contaminant (i.e., a
positive determination), the Agency must publish a proposed Maximum
Contaminant Level Goal (MCLG) \1\ and NPDWR \2\ within 24 months. After
the proposal, the Agency must publish a final MCLG and promulgate a
final NPDWR (SDWA section 1412(b)(1)(E)) within 18 months.\3\
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\1\ An 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. MCLGs 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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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
CCLs 3 and 4 provided a foundation for RD 4 by enhancing the EPA's
ability to identify contaminants of concern for drinking water.
Sections III and IV in this document provide more detailed information
about the approach and outcomes for RD 4 and the contaminant-specific
regulatory determinations.
2. The First Contaminant Candidate List (CCL 1) and Regulatory
Determination (RD 1)
The 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 published the final
regulatory determinations for nine of the 60 CCL 1 contaminants in the
FR on July 18, 2003. The Agency determined that NPDWRs were not
necessary for 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's website and issued health
advisories \5\ (HAs) 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\ Health advisories provide information on contaminants that
can cause human health effects and are known or anticipated to occur
in drinking water. The EPA's health advisories are non-enforceable
and provide technical guidance to states agencies and other public
health officials on health effects, analytical methodologies, and
treatment technologies associated with drinking water contamination.
Health advisories 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
Determination (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
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 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 dipropylthiocarbamate (EPTC), fonofos,
terbacil, and 1,1,2,2-
[[Page 14101]]
tetrachloroethane (73 FR 44251; USEPA, 2008a). The Agency issued new or
updated health advisories for boron, dacthal degradates, 2,4-
dinitrotoluene, 2,6-dinitrotoluene, and 1,1,2,2-tetrachloroethane.
4. The Third Contaminant Candidate List (CCL 3) and Regulatory
Determination (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, the EPA improved and built upon the process that
was used for CCL 1 and CCL 2. The 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, the EPA developed a
multi-step process to select candidates for the final CCL 3, which
included the following key steps:
(a) Identification of a broad universe of ~7,500 potential drinking
water contaminants (the CCL 3 Universe);
(b) screening the CCL 3 Universe to a preliminary CCL (PCCL) of
~600 contaminants based on the potential to occur in PWSs and the
potential for public health concern; and
(c) evaluation of the PCCL contaminants based on a more detailed
review of the occurrence and health effects data to identify a list of
116 CCL 3 contaminants.
The Agency published its preliminary regulatory determinations for
contaminants listed on the CCL 3 in the FR on October 20, 2014 (79 FR
62715; USEPA, 2014a). In that document, the EPA made preliminary
determinations for 5 of the 116 contaminants listed on the CCL 3
including a preliminary positive determination for strontium and
preliminary negative determinations for dimethoate, 1,3-dinitrobenzene,
terbufos, and terbufos sulfone. On January 4, 2016 (81 FR 13; USEPA,
2016a), the EPA finalized the negative determinations for dimethoate,
1,3-dinitrobenzene, terbufos, and terbufos sulfone. The EPA announced a
delay in issuing a final regulatory determination on strontium in order
to consider additional data. Additional discussion on strontium is
provided in Section V of this document.
The EPA also published an off-cycle final determination to regulate
one CCL 3 contaminant, perchlorate, on February 11, 2011 (76 FR 7762;
USEPA, 2011a) during the RD 3 cycle (bringing the total number of final
determinations to five). Additional information about the perchlorate
determination can be found in that document.
5. The Fourth Contaminant Candidate List (CCL 4) and Regulatory
Determination (RD 4)
The final CCL 4 was published on November 17, 2016 (81 FR 81099;
USEPA, 2016b) and is the latest CCL published by EPA. The final CCL 4
consists of 97 chemicals or chemical groups and 12 microbiological
contaminants. Most CCL 4 contaminants were carried over from CCL 3
(which, as described above, was developed according to a rigorous
process with input from multiple stakeholders over the course of
multiple years). The EPA added two contaminants (manganese and
nonylphenol) to the CCL 4 list based on nominations. The EPA removed
from the list those CCL 3 contaminants that had been subject to recent
preliminary and/or final regulatory determinations (perchlorate,
dimethoate, 1,3-dinitrobenzene, terbufos, terbufos sulfone, and
strontium) and three pesticides with cancelled registrations
(disulfoton, fenamiphos, and molinate).
III. Approach and Overall Outcomes for RD 4
This section describes (a) the approach the EPA used to identify
and evaluate contaminants for the Agency's fourth round of Regulatory
Determination (RD 4) along with the overall outcome of applying this
approach, (b) the supporting RD 4 documentation, and (c) the technical
analyses and sources of health and occurrence information.
A. Summary of the Approach and Overall Outcomes for RD 4
The approach taken under RD 4 is similar to that used in previous
rounds of Regulatory Determination and formalized in a written Protocol
under Regulatory Determination 3. The Regulatory Determination 4
Protocol, found in Appendix E of the Regulatory Determination 4 Support
Document (USEPA, 2019a), like the Regulatory Determination 3 protocol,
specifies a three-phase process. The three phases are: (1) The Data
Availability Phase, (2) the Data Evaluation Phase, and (3) the
Regulatory Determination Assessment Phase. Figure 1 provides an
overview of the process the EPA uses to identify which CCL 4
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 4 process
please refer to the Regulatory Determination 4 Protocol (Appendix E to
USEPA, 2019a).
SDWA 1412 (b)(1)(C) requires that the Administrator prioritize
selection of contaminants that present the greatest public health
concern. The Administrator, in making such selections, shall take into
consideration, 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 due to exposure to contaminants in drinking
water than the general population. Because the RD 4 process includes
consideration of human health effects, the Agency's Policy on
Evaluating Health Risks to Children (USEPA, 1995a) to consistently and
comprehensively address children's unique vulnerabilities, recently
reaffirmed by Administrator Wheeler (USEPA, 2018a), applies to this
action. We have explicitly considered children's health in the RD 4
process by reviewing all the available children's exposure and health
effects information.
[[Page 14102]]
[GRAPHIC] [TIFF OMITTED] TP10MR20.012
1. Phase 1 (Data Availability Phase)
In Phase 1, the Data Availability Phase, the Agency identifies
contaminants that have sufficient health and occurrence data to proceed
to Phase 2 and be listed on a ``short list'' for further evaluation.
SDWA 1412(b)(1)(B)(ii)(II) requires that the EPA consider the best
available public health information in making the regulatory
determination.
To identify contaminant health effects data that are sufficient to
make a regulatory determination regarding potential adverse health
effect(s), the Agency considers whether an EPA health assessment or an
externally peer-reviewed health assessment from another Agency is
available, from which a health reference level (HRL) \6\ sufficient to
inform a regulatory determination can be derived. (See Section III.C.1
of this document for information about how HRLs are derived.)
Consistent with SDWA 1412.b.(3)(A)(i), EPA used health assessments to
derive an HRL that the Agency has concluded are the best available peer
reviewed science finalized before March 1, 2019. EPA establishes a
cutoff date where it no longer considers new health-based information
in order to allow for timely determinations and reviews. The EPA did
not use draft health assessments to derive HRLs. Sources of health
assessments may include: (a) EPA's Office of Water (OW) health
assessments: Health Advisory (HA) Documents and Health Effects Support
Documents (HESDs); (b) EPA's Office of Research and Development (ORD)
Integrated Risk Information System (IRIS) assessments; (c) EPA's ORD
Provisional Peer-Reviewed Toxicity Values (PPRTVs); (d) EPA's Office of
Pesticide Programs (OPP) health assessments: Reregistration Eligibility
Decisions (REDs), Interim Reregistration Eligibility Decisions (IREDs),
Tolerance Reassessment Progress and Risk Management Decisions (TREDs),
and Health Effects Division Human Health Risk Assessments (HED HHRAs);
(e) U.S. Department of Health and Human Services' Agency for Toxic
Substances and Disease Registry (ATSDR) Toxicological Profiles; (f)
Health Canada Guidelines for Drinking Water; (g) the World Health
Organization (WHO) Drinking Water Guidelines; and (h) publicly
available state assessments that have been externally peer-reviewed and
provide new science not considered in the other RD 4 assessment sources
listed above. To support a regulatory determination, the EPA evaluates
whether a health assessment used methods, standards, and guidelines
comparable to those of current EPA guidelines and guidance documents.
If a suitable health assessment is not available for a contaminant, the
[[Page 14103]]
contaminant will not proceed to Phase 2. The EPA is aware of draft
health assessments that have not yet been finalized for contaminants on
which the EPA is making a preliminary determination today. Once
finalized, the EPA will consider these new sources of information in
future regulatory decision making.
---------------------------------------------------------------------------
\6\ An HRL is a health-based concentration against which the
Agency evaluates occurrence data when making decisions about
preliminary regulatory determinations. An HRL is not a final
determination on establishing a protective level of a contaminant in
drinking water for a particular population; it is derived prior to
development of a complete health and exposure assessment and can be
considered a screening value.
---------------------------------------------------------------------------
To identify contaminant occurrence data that are sufficient to make
a regulatory determination regarding the frequency and level of
occurrence in PWSs, the Agency considers nationally representative
finished water data (samples are collected after the water undergoes
treatment). The following sources, administered or overseen by the EPA,
include finished water occurrence data that are considered nationally
representative: (a) The Third Unregulated Contaminant Monitoring Rule
(UCMR 3); (b) the Second Unregulated Contaminant Monitoring Rule (UCMR
2); (c) the First Unregulated Contaminant Monitoring Rule (UCMR 1); (d)
the Unregulated Contaminant Monitoring (UCM) program; and (e) the
National Inorganics and Radionuclides Survey (NIRS).\7\
---------------------------------------------------------------------------
\7\ Specific types of UCMR monitoring (e.g., assessment
monitoring and sometimes the screening survey) are considered
nationally representative. These are described further in Section
III.C.2.a.1 of this document.
---------------------------------------------------------------------------
If nationally representative data are not available, the EPA
identifies and evaluates other finished water data, which may include
other national assessments, regional data, state, and more localized
finished water assessments. These other finished water data may 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: (a) Finished water assessments for
Federal agencies (e.g., EPA and the United States Geological Survey
(USGS)); \8\ (b) state-level finished water monitoring data; (c)
research performed by institutions, universities, and government
scientists (information published in the scientific literature); and/or
(d) other supplemental finished water monitoring surveys (e.g.,
Pesticide Monitoring Program (PMP), and other targeted surveys or
localized state/federal monitoring surveys).
---------------------------------------------------------------------------
\8\ These may be assessments that are geographically distributed
across the nation but not intended to be statistically
representative of the nation. Examples include the EPA's 1996
Monitoring Requirements for Public Drinking Water Supplies, also
known as the Information Collection Rule (USEPA, 1996), and various
USGS water quality surveys.
---------------------------------------------------------------------------
The EPA prefers to have nationally representative data when making
regulatory determinations but may also use other sources of finished
water data to address the occurrence-related aspects of the statutory
criteria when deciding to regulate a contaminant. In Phase 1, the
Agency does this by assessing whether the non-nationally-representative
finished water occurrence data show at least one detection in finished
water at levels >\1/2\ the HRL \9\ for the critical endpoint. If a
contaminant has nationally representative or non-nationally
representative finished water occurrence data showing at least one
detection >\1/2\ HRL, the contaminant passes the Occurrence Data
Availability Assessment and proceeds to the next phase of analysis.
However, it is difficult to determine that a contaminant is not
occurring or not likely to occur based on sources of non-nationally
representative finished water occurrence data because the data are
limited in scope and the contaminant could be occurring in other parts
of the country that were not monitored.
---------------------------------------------------------------------------
\9\ Note that the \1/2\ HRL threshold is based on a
recommendation from the NDWAC working group that provided
recommendations on the first regulatory determination effort (USEPA,
2000).
---------------------------------------------------------------------------
In certain limited cases, a contaminant's occurrence data may have
been gathered using a specialized or experimental method that is not in
general use. If a widely available analytical method does not exist,
the contaminant will not be a viable candidate for regulation with a
Maximum Contaminant Level (MCL). With that in mind, in the Analytical
Methods Availability Assessment, the EPA determines for each
contaminant whether a widely available analytical method for monitoring
exists. (A widely available analytical method is a method employing
technology that is commonly in use at numerous drinking water
laboratories.) If a widely available analytical method exists, the
contaminant passes the Analytical Methods Availability Assessment. If a
widely available analytical method does not exist, the EPA may advance
the contaminant to Phase 2 if the Agency determines that indicator or
surrogate monitoring, or use of a treatment technique (TT), could allow
for effective regulation and there is compelling evidence of
occurrence.
In addition to considering contaminants individually, the EPA also
may consider issuing a regulatory determination for groups of
contaminants. The EPA has regulated certain contaminants in drinking
water collectively.
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) An EPA health assessment or an externally peer-reviewed health
assessment from another Agency that conforms with the current EPA
guidelines is available, from which an HRL can be derived;
(b) Either nationally representative finished water occurrence data
are available, or other finished water occurrence data show occurrence
at levels >\1/2\ the HRL; and
(c) A widely available analytical method for monitoring is
available.
If a contaminant or group meets these three criteria, it is placed
on a ``short list'' and proceeds to Phase 2. After evaluating the 109
CCL 4 contaminants and two additional contaminants (4-androstene-3,17-
dione and testosterone) \10\ in Phase 1, the Agency identified 25 CCL 4
contaminants to evaluate further in Phase 2 (contaminants listed in
Table 1).
---------------------------------------------------------------------------
\10\ Contaminants monitored under UCMR 3 but not included in CCL
3 or CCL 4.
Table 1--Contaminants Proceeding From Phase 1 to Phase 2
------------------------------------------------------------------------
-------------------------------------------------------------------------
1,1,1,2-Tetrachloroethane.
1,1-Dichloroethane.
1,2,3-Trichloropropane.
1,4-Dioxane.
Acephate.
Acetochlor.
alpha-Hexachlorocyclohexane.
Aniline.
Chlorate.
Cobalt.
Cyanotoxins.
Legionella pneumophila.
Manganese.
Methyl bromide (Bromomethane).
Metolachlor.
Molybdenum.
Nitrobenzene.
N-Nitrosodiethylamine (NDEA).
N-Nitrosodimethylamine (NDMA).
N-Nitroso-di-n-propylamine (NDPA).
N-Nitrosopyrrolidine (NPYR).
Perfluorooctanesulfonic acid (PFOS).
Perfluorooctanoic acid (PFOA).
RDX.
Vanadium.
------------------------------------------------------------------------
The remaining 84 CCL 4 contaminants and two additional contaminants
(4-androstene-3,17-dione and testosterone) (listed in Table 2) did not
meet one or more of the Phase 1 data availability criteria above and
were not considered further for RD 4.
[[Page 14104]]
Table 2--Contaminants Not Proceeding From Phase 1 to Phase 2
------------------------------------------------------------------------
-------------------------------------------------------------------------
Has nationally representative finished water data but no health
assessment
1,3-Butadiene.
3-Hydroxycarbofuran.
4-Androstene-3,17-dione.
Acetochlor ethanesulfonic acid (ESA).
Acetochlor oxanilic acid (OA).
Alachlor ESA.
Alachlor OA.
Chloromethane (Methyl chloride).
Equilin.
Estradiol (17-beta estradiol).
Estriol.
Estrone.
Ethinyl Estradiol (17-alpha ethynyl estradiol).
Germanium.
Halon 1011 (bromochloromethane).
HCFC-22.
Methyl tert-butyl ether.
Metolachlor ESA.
Metolachlor OA.
n-Propylbenzene.
sec-Butylbenzene.
Tellurium.
Testosterone.
Has available or in process health assessment and other finished
drinking water data but no occurrence at levels \1/2\ HRL
1-Butanol.
Acrolein.
Bensulide.
Benzyl chloride.
Captan.
Dicrotophos.
Diuron.
Ethoprop.
Ethylene glycol.
Ethylene thiourea (Maneb 12427382).
Formaldehyde.
Methamidophos.
Methanol.
N-Nitrosodiphenylamine (NDPhA) *.
Oxydemeton-methyl.
Oxyfluorfen.
Permethrin.
Profenofos.
Tebuconazole.
Tribufos.
Vinclozolin.
Ziram.
Has other finished drinking water data but no health assessment
17alpha-estradiol.
Acetaldehyde.
Adenovirus *.
Butylated hydroxyanisole.
Caliciviruses *.
Enterovirus *.
Equilenin.
Erythromycin.
Hexane.
Mestranol.
Mycobacterium avium *.
Naegleria fowleri *.
Nonylphenol.
Norethindrone (19-Norethisterone).
Does not have nationally representative or other finished water data
2-Methoxyethanol.
2-Propen-1-ol.
4,4'-Methylenedianiline.
Acetamide.
Campylobacter jejuni.
Clethodim.
Cumene hydroperoxide.
Dimethipin.
Escherichia coli (O157).
Ethylene oxide.
Helicobacter pylori.
Hepatitis A virus.
Hydrazine.
Nitroglycerin.
N-Methyl-2-pyrrolidone.
o-Toluidine.
Oxirane, methyl-.
Quinoline.
Salmonella enterica.
Shigella sonnei.
Tebufenozide.
Thiodicarb.
Thiophanate-methyl.
Toluene diisocyanate.
Triethylamine.
Triphenyltin hydroxide (TPTH).
Urethane.
------------------------------------------------------------------------
\*\ Does not have a widely available analytical method for occurrence
monitoring.
2. Phase 2 (Data Evaluation Phase)
In Phase 2, the Agency collects additional data on occurrence
(including finished water data; ambient water data; data on use,
production, and release; and information on environmental fate and
transport), and more thoroughly evaluates this information (based on
factors below) to identify contaminants that should proceed to Phase 3.
In Phase 2, the Agency 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. As noted in Section III.A, SDWA 1412.b.1.C requires
that the Administrator select contaminants that present the greatest
public health concern. To identify such contaminants, the Agency
considers the following information:
(a) How many samples (number and percentage) have detections > HRL
and \1/2\ HRL in the nationally representative and other finished water
occurrence data?
(b) How many systems (number and percentage) have detections > HRL
and \1/2\ HRL in the nationally representative and other finished water
occurrence data?
(c) Are there uncertainties or limitations with the data and/or
analyses, such as the age of the dataset, the detection limit level
(i.e., minimum reporting level [MRL\11\] > 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?
---------------------------------------------------------------------------
\11\ The MRL is the minimum concentration that is required to be
reported quantitatively in a study. The MRL is set at a value that
takes into account typical laboratory capabilities to reliably and
cost-effectively detect and quantify a compound.
---------------------------------------------------------------------------
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 should proceed to Phase 3 for a potential negative
determination. Because the primary goal of RD 4 is to focus on
contaminants of public health concern, potential negative
determinations are a lower priority than potential positive
determinations. The Agency considers the following information in
selecting contaminants of no or low potential for public health concern
to proceed to Phase 3:
(a) Does the contaminant have nationally representative finished
water data showing no or low number or percent of detections > HRL?
(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? \12\
---------------------------------------------------------------------------
\12\ Note that other finished water data (i.e., non-nationally-
representative occurrence data) tend to be limited in scope and the
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).
---------------------------------------------------------------------------
(c) Does additional occurrence information of high quality support
the conclusion that there is low or no occurrence or potential for
occurrence in drinking water? For example, is the occurrence in
ambient/source water at levels below the HRL? How are releases to the
environment or use/production changing over time?
(d) Are critical gaps in health and occurrence information/data
minimal?
After evaluating the ``short list'' contaminants (listed in Table
1), the Agency identified 10 CCL 4 contaminants to proceed to Phase 3
(listed in Table 3). The contaminants are within one of the following
Phase 2 data evaluation categories:
(a) A contaminant or part of a contaminant group occurring or
likely to
[[Page 14105]]
occur at levels and frequencies of public health concern, or
(b) A contaminant not occurring or not likely to occur at levels
and frequencies of public health concern and no data gaps.
Table 3--Contaminants Proceed- ing From Phase 2 to Phase 3
------------------------------------------------------------------------
-------------------------------------------------------------------------
1,1-Dichloroethane.
1,4-Dioxane.
1,2,3-Trichloropropane.
Acetochlor.
Methyl Bromide.
Metolachlor.
Nitrobenzene.
PFOA.
PFOS.
RDX.
------------------------------------------------------------------------
Note that the Agency does not have a threshold for occurrence in
drinking water that triggers whether a contaminant is of public health
concern. A determination of public health concern requires a
consideration of a number of factors, some of which include the health
effect(s), the potency of the contaminant, the level at which the
contaminant is found in drinking water, the frequency at which 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. Given the many possible
combinations of factors, a simple threshold is not viable. In the end,
a 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 decision that takes into consideration
multiple factors.
The remaining 15 CCL 4 contaminants (listed in Table 4) did not
proceed to Phase 3 and were not considered for RD 4 because of one or
more of the following critical health, occurrence, and/or other data
gaps:
(a) An updated health assessment completed by March 1, 2019 was not
identified;
(b) Critical health effects gap (e.g., lack of data to support
quantification for the oral route of exposure);
(c) Lack of nationally representative finished water occurrence
data and lack of sufficient other data to demonstrate occurrence at
levels and frequencies of public health concern; and
(d) Critical occurrence data limitation or gap (e.g., inconsistent
results and/or trends in occurrence data requiring further research;
significant uncertainty in occurrence analyses and/or data).
Table 4 identifies the health, occurrence, and/or other data gaps
that prevented the following 15 contaminants from moving forward for RD
4. The Agency continues to conduct research and collect information to
fill the data and information gaps identified in Table 4.
Table 4--Data and Rationale Summary of the 15 Contaminants in Phase 2 Not Proceeding to Phase 3
--------------------------------------------------------------------------------------------------------------------------------------------------------
Occurrence data
Number Contaminant Health data available available Rationale
--------------------------------------------------------------------------------------------------------------------------------------------------------
1................... 1,1,1,2-Tetrachloroethane...................... Yes...................... Yes...................... Health data gap (a review
of the current literature
is needed to decide if an
update to the 1987 IRIS
health assessment is
warranted).
2................... Acephate....................................... Yes...................... No....................... Occurrence data gaps (no
nationally representative
finished water data or
sufficient other finished
water data).
3................... alpha-Hexachlorocyclohexane.................... Yes...................... No....................... Occurrence data gaps (no
nationally representative
finished water data or
sufficient other finished
water data).
4................... Aniline........................................ Yes...................... No....................... Occurrence data gaps (no
nationally representative
finished water data or
sufficient other finished
water data).
5................... Chlorate....................................... ......................... ......................... Will be evaluated and
considered as part of the
review of the existing
Disinfectants/Disinfection
Byproducts (D/DBP)
rules.13 14
6................... Cobalt......................................... Yes...................... Yes...................... Health data gap (updated
health assessment needed
to consider new subchronic
and developmental
studies).
7................... Cyanotoxins.................................... Yes...................... No....................... Health advisories available
for some specific
cyanotoxins (microcystins
and cylindrospermopsin);
occurrence data gaps
(insufficient nationally
representative finished
water data or other
finished water data).
Certain cyanotoxins are
being monitored under UCMR
4 but final UCMR 4 data
will not be complete in
time for preliminary
determination.
8................... Legionella pneumophila......................... Yes...................... No....................... MCLG available; occurrence
data gaps (no nationally
representative finished
water data or sufficient
other finished water
data). Will be evaluated
and considered as part of
the review of the existing
SWTR.\14\
9................... Manganese...................................... No....................... No....................... Health and occurrence data
gaps (updated health
assessment \15\ not
completed by RD 4 cutoff
date). Manganese is being
monitored for under UCMR 4
but final UCMR 4 data will
not be complete in time
for preliminary
determination.
10.................. Molybdenum..................................... No....................... Yes...................... Health data gap (updated
assessment needed to
consider multiple new
studies).
11.................. N-Nitrosodiethylamine (NDEA)................... ......................... ......................... Will be evaluated and
considered as part of the
review of the existing D/
DBP rules.\13\
12.................. N-Nitrosodimethylamine (NDMA).................. ......................... ......................... Will be evaluated and
considered as part of the
review of the existing D/
DBP rules.\13\
13.................. N-Nitroso-di-n-propylamine (NDPA).............. ......................... ......................... Will be evaluated and
considered as part of the
review of the existing D/
DBP rules.\13\
14.................. N-Nitrosopyrrolidine (NPYR).................... ......................... ......................... Will be evaluated and
considered as part of the
review of the existing D/
DBP rules.\13\
[[Page 14106]]
15.................. Vanadium....................................... Yes...................... Yes...................... Health data gap; undergoing
assessment by EPA IRIS:
https://www.epa.gov/sites/production/files/2019-04/documents/iris_program_outlook_apr2019.pdf.
--------------------------------------------------------------------------------------------------------------------------------------------------------
3. Phase 3 (Regulatory Determination Assessment Phase)
---------------------------------------------------------------------------
\13\ Under RD 3 (79 FR 62716), the EPA noted that disinfection
byproducts (DBPs) need to be evaluated collectively, because the
potential exists that the treatment used to control a specific DBP
could affect the concentrations of other DBPs and potentially
microorganisms.
\14\ Under the Six-Year Review 3 (82 FR 3518, USEPA, 2016c), the
Agency completed a detailed review of 76 NPDWRs and determined that
eight NPDWRs were candidates for regulatory revision. The eight
NPDWRs are included in the Stage 1 and the Stage 2 Disinfectants and
Disinfection Byproducts Rules, the Surface Water Treatment Rule
(SWTR), the Interim Enhanced Surface Water Treatment Rule, and the
Long Term 1 Enhanced Surface Water Treatment Rule.
\15\ Health Canada finalized their Manganese Guideline for
Canadian Drinking Water Quality in June 2019. The Guideline
summarizes new health effects information published since the EPA's
manganese health assessment in 2004 (https://www.canada.ca/content/dam/hc-sc/documents/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-guideline-technical-document-manganese/pub-manganese-0212-2019-eng.pdf).
---------------------------------------------------------------------------
Phase 3, the Regulatory Determination Assessment 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 (SDWA
1412(b)(1)(A)):
(a) Statutory Criterion #1--The contaminant may have an adverse
effect on the health of persons. To evaluate criterion #1, the EPA
evaluates whether a contaminant has an EPA health assessment, or an
externally peer-reviewed health assessment from another Agency that is
publicly available and conforms with current the EPA guidelines, from
which an HRL can be derived. The HRL derived in or from the health
assessment takes into account the MOA, the critical health effect(s),
the dose-response relationship for critical health effect(s), and
impacts on sensitive population(s) or lifestages. HRLs are preliminary
health-based concentrations against which occurrence data is evaluated
to determine if contaminants may occur at levels of potential public
health concern. HRLs are not final determinations on establishing a
protective level of a contaminant in drinking water for any particular
population. HRLs are derived prior to the development of a complete
health and exposure assessment and can be considered screening-level
values.
If an acceptable health assessment that demonstrates adverse health
effects is available, the Agency answers ``yes'' to the first statutory
criterion. Otherwise, the Agency answers ``no'' to the first statutory
criterion. (In practice, it is expected that any contaminant that
reaches Phase 3 would receive a ``yes'' to the first 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. The EPA compares the occurrence data for each contaminant to
the 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 may consider the following factors
when identifying contaminants or contaminant groups that are occurring
at frequencies and levels of public health concern:
How many samples (number and percentage) have detections >
HRL in the nationally representative and other finished water
occurrence data?
How many systems (number and percentage) have detections >
HRL in the nationally representative and other finished water
occurrence data?
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 groundwater
systems?
Are there significant uncertainties or limitations with
the data and/or analyses, such as the age of the dataset, the detection
limit level (i.e., MRL > 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 occurring at
frequencies and levels of public health concern also include:
How many samples (number and percentage) have detections >
\1/2\ HRL in the nationally representative and other finished water
occurrence data?
How many systems (number and percentage) have detections >
\1/2\ HRL in the nationally representative and other finished water
occurrence data?
How many samples (number and percentage) have detections >
HRL and \1/2\ HRL in the ambient/source water occurrence data?
How many monitoring sites (number and percentage) have
detections > HRL and \1/2\ 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?
Is the contaminant introduced by water treatment processes
that provide public health benefits such that it is relevant to risk-
balancing considerations?
Are there additional uncertainties or limitations with the
data and/or analyses that should be considered?
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 consideration of 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. The EPA evaluates the population exposed at the health
level of concern along with several other
[[Page 14107]]
factors to determine if regulation presents a meaningful opportunity
for health risk reduction. Among other things, the EPA may consider the
following factors in evaluating statutory criterion #3:
What is the nature of the health effect(s) identified in
statutory criterion #1?
Are there sensitive populations that may be affected
(evaluated either qualitatively or quantitatively \16\)?
---------------------------------------------------------------------------
\16\ If appropriate and available, the Agency quantitatively
takes into account exposure data applicable to sensitive populations
or lifestages when deriving HRLs for regulatory determinations. When
data are not available on sensitive populations, the derivation of
the RfD typically includes an uncertainty factor to account for the
weakness in the database. Additionally, the EPA will use exposure
factors relevant to the sensitive population in deriving the HRL.
See section III.C.1. Sensitive populations are also qualitatively
considered by providing national prevalence estimates for a
particular sensitive population, if available.
---------------------------------------------------------------------------
Based on the occurrence information for statutory
criterion #2, including the number of systems potentially affected,
what is the national population exposed or served by systems with
levels > HRL and \1/2\ HRL?
For non-carcinogens, are there other sources of exposure
that should be considered (i.e., what is the relative source
contribution (RSC) from drinking water)?
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?
Are there any limiting considerations related to
technology (e.g., lack of available treatment or analytical methods
\17\)?
---------------------------------------------------------------------------
\17\ If the Agency decides to regulate a contaminant, the SDWA
requires that the EPA issue a proposed regulation within two years
of the final determination. As part of the proposal, the Agency must
list best available technologies (BATs), small system compliance
technologies (SSCTs), and approved analytical methods if it proposes
an enforceable MCL. Alternatively, if the EPA proposes a TT instead
of an MCL, the Agency must identify the TT. The 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 a system level and aggregated at the national
level. To date, treatment information and approved analytical
methods have not been significant factors in regulatory
determinations but are important considerations for regulation
development.
---------------------------------------------------------------------------
If the Administrator, in his or her sole judgement, 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. Additionally, after identifying compounds
occurring at frequencies and levels of public health concern, if any,
the Agency may initiate a systematic literature review to identify new
studies that may influence the derivation of a Reference Dose (RfD)
and/or Cancer Slope Factor (CSF). The list of potentially relevant
health effect studies that could affect the derivation of an RfD or CSF
identified through the systematic review process would then be placed
in the docket at the time of the Preliminary Determination for public
comment (discussed further in Section IV of this document).
If, after considering input provided during the public comment
period, the Agency again 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.\18\ It should be noted that the analyses associated with a
regulatory determination process are distinct from the more detailed
analyses needed to develop an NPDWR. Thus, a decision to regulate is
the beginning of the Agency's regulatory development process, not the
end. For example, the EPA may find at a later point in the regulatory
development process, and based on additional or new information, that
the contaminant no longer meets the three statutory criteria and may,
as a result, withdraw the determination to regulate.
---------------------------------------------------------------------------
\18\ The statute authorizes a nine-month extension of this
promulgation date.
---------------------------------------------------------------------------
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. A final
determination not to regulate a contaminant is, by statute, a final
Agency action and is subject to judicial review. If a negative
determination or no determination is made for a contaminant, the Agency
may decide to develop a 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 (e.g.,
one-day, ten-days, several years, and a lifetime). The EPA's HAs are
non-enforceable and non-regulatory and provide technical information to
states agencies and other public health officials on health effects,
analytical methodologies, and treatment technologies associated with
drinking water contamination.
While a negative determination is considered a final Agency action
under SDWA for a round of regulatory determinations, the contaminant
may be relisted on a future CCL based on newly available health and/or
occurrence information.
At this time, the Agency is not making preliminary regulatory
determinations for two of the ten contaminants that proceeded to Phase
3. After evaluating the remaining CCL 4 contaminants in Table 3 against
the three SDWA criteria and considering the factors listed for each,
the Agency is making a preliminary regulatory determination for these
eight CCL 4 contaminants. Table 5 provides a summary of the 10
contaminants evaluated for Phase 3 and the preliminary regulatory
determination outcome for each. The Agency seeks comment on the
preliminary determination to regulate two contaminants (PFOS and PFOA)
and to not regulate six contaminants (1,1-dichloroethane, acetochlor,
methyl bromide, metolachlor, nitrobenzene, and RDX). Section IV.B of
this document provides a more detailed summary of the information and
the rationale used by the Agency to reach its preliminary decisions for
these contaminants. Section V of this document provides more
information about 1,4-dioxane and 1,2,3-trichloropropane, the two Phase
3 contaminants for which the EPA is not making a preliminary regulatory
determination at this time.
Table 5--Contaminants Evaluated in Phase 3 and the Regulatory
Determination Outcome
------------------------------------------------------------------------
Preliminary
Number RD 3 contaminants determination outcome
------------------------------------------------------------------------
1................... 1,1-Dichloroethane...... Do Not Regulate.
2................... 1,4-Dioxane............. No Determination.
3................... 1,2,3-Trichloropropane.. No Determination.
4................... Acetochlor.............. Do Not Regulate.
5................... Methyl Bromide.......... Do Not Regulate.
6................... Metolachlor............. Do Not Regulate.
7................... Nitrobenzene............ Do Not Regulate.
8................... PFOA.................... Regulate.
9................... PFOS.................... Regulate.
10.................. RDX..................... Do Not Regulate.
------------------------------------------------------------------------
B. Supporting Documentation for EPA's Preliminary Determination
For this action, the EPA prepared several supporting documents that
are available for review and comment in the EPA Water Docket. These
support documents include:
[[Page 14108]]
The comprehensive regulatory support document, Regulatory
Determination 4 Support Document (USEPA, 2019a), summarizes the
information and data on the physical and chemical properties, uses and
environmental release, environmental fate, potential health effects,
occurrence and exposure estimates, analytical methods, treatment
technologies, and preliminary determinations. Additionally, Appendix E
of the Regulatory Determinations 4 Support Document describes the
approach implemented by the Agency to evaluate the CCL 4 contaminants
in a three-phase process and select the contaminants for preliminary
determinations for RD 4.
A comprehensive technical occurrence support document for
UCMR 3, Occurrence Data from the Third Unregulated Contaminant
Monitoring Rule (UCMR 3) (USEPA, 2019b). This occurrence support
document includes more detailed information about UCMR 3, how the 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.
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 the EPA used to support
these preliminary determinations.
1. Evaluation of Adverse Health Effects
This section describes the approach for deriving the HRL for the
contaminants under consideration for regulatory determinations. HRLs
are health-based drinking water concentrations against which the EPA
evaluates occurrence data to determine if contaminants occur at levels
of potential public health concern. HRLs are not final determinations
on establishing a protective level of a contaminant in drinking water
for any particular population and are derived prior to the development
of a complete health and exposure assessment. More specific information
about the potential for adverse health effects for each contaminant is
presented in section IV.B of this action.
a. Derivation of an HRL
There are two general approaches to the derivation of an HRL. One
general approach is used for chemicals with a threshold dose-response
(usually involving non-cancer endpoints, and occasionally cancer
endpoints). The second general approach is used for chemicals that
exhibit a linear, non-threshold response to dose (as is typical of
carcinogens). A variant of the second approach is used when a
carcinogen with a linear dose-response has a known mutagenic MOA
(USEPA, 2019a).
HRLs for contaminants with a threshold dose-response (typically
non-cancer endpoints) are calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP10MR20.013
HRLs for contaminants with a linear dose-response (typically cancer
endpoints) are calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP10MR20.014
HRLs for carcinogenic contaminants with a known mutagenic MOA are
calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP10MR20.015
Where:
HRL = Health Reference Level ([micro]g/L)
RfD = Reference Dose (mg/kg/day)
DWI = Drinking Water Intake (L)
BW = Body weight (kg)
CSF = Cancer Slope Factor (mg/kg/day)-1
CRL = Cancer risk level, assumed to be 1 in a million (1 x 10-6)
ADAF = The Age Dependent Adjustment Factor for the age group i (by
default, ADAF = 10 from birth to two years of age; ADAF = 3 from two
to sixteen years of age; ADAF = 1 from sixteen to seventy years of
age)
f = fraction of applicable period of exposure (by default, lifetime
of seventy years) represented by age group i
RSC = Relative Source Contribution, which is the portion
(percentage) of an individual's exposure attributed to drinking
water rather than other sources (e.g., food, ambient air). In
Regulatory Determination, a 20% RSC is used for HRL derivation
because (1) HRLs are developed prior to a complete exposure
assessment, and (2) 20% is the lowest and most conservative RSC used
in the derivation of an MCLG for drinking water.
b. Protection of Sensitive Subpopulations
In prioritizing the contaminants of greatest public health concern
for regulatory determination, Section 1412(b)(1)(C) of SDWA 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 due to exposure to
contaminants in drinking water compared to the general population.'' If
appropriate and if adequate data are available, the Agency will use
data from sensitive populations and lifestages quantitatively when
deriving HRLs for regulatory determinations in the following manner:
(a) For non-carcinogens, an HRL can be developed for a sensitive
population if data are available to associate exposure with the
critical health endpoint in a specific group or during a specific
period of sensitivity. Age-specific drinking water intake (DWI) to body
weight (BW) ratio values from the Exposure Factors Handbook (USEPA,
2011b) can be used to reflect the period of exposure more accurately.
The Agency can also apply specific uncertainty factors (UFs) when
deriving the RfD if toxicological data are lacking for a sensitive
population. Two common justifications for UFs that can be applied to
account for sensitive populations are: (1) Variation in sensitivity
among the members of the human population (i.e., intraspecies
variability) and (2) uncertainty associated with an incomplete
database.
(b) For HRLs developed for carcinogens with a mutagenic MOA, the
2005 Cancer Guidelines require consideration of increased risks due to
early-life exposure. When chemical-specific data to quantify the
increased risk are lacking, Age Dependent Adjustment Factors (ADAFs)
are applied, generally with a 10-fold adjustment for early life
exposures, a 3-fold adjustment for childhood/adolescent exposures, and
no additional adjustment for exposures later in life (as shown above).
Age-specific drinking-water-intake-to-body-weight ratio values are also
applied from the Exposure Factors Handbook (USEPA, 2011b). In cases
where the data on the MOA are lacking, the default low-dose linear
extrapolation approach without ADAFs is used.
While this action is not subject to Executive Order 13045:
Protection of Children from Environmental Health and Safety Risks, the
Agency's Policy on Evaluating Health Risks to Children (USEPA, 1995a),
recently reaffirmed by Administrator Wheeler (USEPA, 2018a), was still
applied for the RD 4 preliminary determination. The EPA's policy
(USEPA, 1995a) requires the EPA to consistently and comprehensively
address children's unique vulnerabilities. For example, if exposure to
a contaminant considered for RD 4 was associated with a developmental
[[Page 14109]]
effect, the EPA derived HRLs using the exposure factors for a bottle-
fed infant to be protective of children, assuming that the adverse
effect identified could occur during the window of time when the infant
is formula-fed (see metolachlor in Section IV.B as an example).
c. Sources of Data/Information for Health Effects
The EPA relies on health assessments produced by the Agency itself
and produced by other agencies. The criteria for accepting a health
assessment for RD 4 are described in Section III.A.1, above. Table 6
summarizes the sources of the health assessment data for each chemical
with a preliminary determination under RD 4. As noted in Section
III.A.3, in the case of potential positive determinations, the EPA
searches for and evaluates additional data and information from the
published literature to supplement the health assessment (Note that the
two Phase 3 contaminants that are not receiving a preliminary
determination are not discussed here. They are 1,4-dioxane and 1,2,3-
trichloropropane. See section V of this document for more on those two
contaminants.)
[GRAPHIC] [TIFF OMITTED] TP10MR20.016
2. Evaluation of Contaminant Occurrence and Exposure
The 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 document:
Unregulated Contaminant Monitoring Rules (UCMR 1, 2, and 3)
UCM Program Rounds 1 and 2, and
Data collected by states.
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 UCMR 3.
The Agency also evaluates supplemental sources of information on
occurrence in drinking water, occurrence in ambient and source water,
and information on contaminant production and release to augment and
complement 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 sources that the EPA reviews and
evaluates. For individual contaminants, the 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 Regulatory Determination 4 Support
Document (see USEPA, 2019a).
a. Primary Sources of Finished Drinking Water Occurrence Data
The following sections provide a brief summary of the finished
water occurrence data sources used in RD 4. Table 8 in section IV lists
the primary data source/finding used to evaluate each of the eight
contaminants considered for regulatory
[[Page 14110]]
determinations. Section V of this document provides more information
about 1,4-dioxane and 1,2,3-trichloropropane, the two Phase 3
contaminants for which the EPA is not making a preliminary regulatory
determination at this time. 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 Rules (UCMR 1, UCMR 2, and
UCMR 3)
The UCMR is the EPA's primary vehicle for collecting monitoring
data on the occurrence of unregulated contaminants in PWSs. SDWA
section 1412(b)(1)(B)(ii)(II) requires that the EPA include
consideration of the data produced by the UCMR program in making
regulatory determinations. The UCMR list is published every five years
and is designed to collect nationally representative occurrence data
that is developed in coordination with the CCL and Regulatory
Determination processes. The UCMR sampling is limited by statute to no
more than 30 contaminants every five years (SDWA section 1445(a)(2)).
PWSs and state primacy agencies are required to report the data to the
EPA. The EPA published the lists and requirements for the UCMR 1 on
September 17, 1999 (64 FR 50556, September 17, 1999, USEPA, 1999), and
the monitoring was conducted primarily during 2001-2003. UCMR 2 was
published on January 4, 2007 (72 FR 367; USEPA, 2007a), with monitoring
conducted primarily during 2008-2010. UCMR 3 was published on May 2,
2012 (77 FR 26071; USEPA, 2012a), with monitoring conducted primarily
during 2013-2015. (The complete analytical monitoring lists are
available at: http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/.) UCMR
4 was published on December 20, 2016 (81 FR 92666), with monitoring
conducted between 2018 and 2020 (final UCMR 4 data is not complete in
time for this RD 4 preliminary determination).
The UCMR program is designed as a three-tiered approach for
monitoring contaminants related to the availability and complexity of
analytical methods, laboratory capacity, sampling frequency, relevant
universe of PWSs, and other considerations (e.g., cost/burden).
Assessment Monitoring (AM) includes the largest number of PWSs and is
generally used when there is sufficient laboratory capacity. The
Screening Survey (SS) includes a smaller number of PWSs to conduct
monitoring and may be used, for example, when there are possible
laboratory capacity issues for the analytical methods required. Pre-
Screen Testing (PST) is generally used to collect monitoring
information for contaminants with analytical methods that are in an
early stage of development, and/or very limited laboratory
availability.
The 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 2001a, for UCMR design details). AM is
required for all large and very large PWSs, those serving between
10,001 and 100,000 people and serving more than 100,000 people,
respectively (i.e., a census of all large and very large systems) and a
national statistically representative sample of 800 small PWSs, those
serving 10,000 or fewer people.\19\ PWSs that purchase 100% of their
water were not required to participate in UCMR 1 and UCMR 2. However,
those systems were not excluded under UCMR 3. All systems that purchase
100% of their water and serve more than 10,000 people were subject to
UCMR 3. Systems that purchase 100% of their water and serve a retail
population of 10,000 or fewer customers were only required to monitor
if they were selected as part of the UCMR 3 nationally representative
sample of small systems.
---------------------------------------------------------------------------
\19\ Section 1445 of the Safe Drinking Water Act was recently
amended by Public Law 115-270, America's Water Infrastructure Act of
2018 (AWIA), and now specifies that, effective October 23, 2021,
subject to the availability of appropriations for such purpose and
appropriate laboratory capacity, the EPA must require all systems
serving between 3,300 and 10,000 persons to monitor and ensure that
only a representative sample of systems serving fewer than 3,300
persons are required to monitor.
---------------------------------------------------------------------------
Each system conducts UCMR assessment monitoring for 12-consecutive
months (during the three-year monitoring period). The rules typically
require quarterly monitoring for surface water systems and twice-a-
year, six-month interval monitoring for groundwater 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 design meets the data
quality objective for overall exposure estimates (99% confidence level
with 1% error tolerance, at 1% exposure), while providing
more precise occurrence estimates for categories of small systems). The
UCMR AM program includes systems from all 50 states, the District of
Columbia, all five U.S. territories, and tribal lands across all of the
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, the EPA looked for additional data to
supplement the SS data for regulatory determinations.
For the UCMR 2 SS, the 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).
For UCMR 3, all large and very large PWSs (serving between 10,001
and 100,000 people and serving more than 100,000 people, respectively),
plus a statistically representative national sample of 800 small PWSs
(serving
[[Page 14111]]
10,000 people or fewer), conducted AM. UCMR 3 SS monitoring was
conducted by all large systems serving more than 100,000 people, a
nationally representative sample of 320 large systems serving 10,001 to
100,000 people, and a nationally representative sample of 480 small
water systems serving 10,000 or fewer people. In contrast to
implementation of UCMR 1 and 2 monitoring, transient noncommunity water
systems that purchase all their finished water from another system were
not excluded from the requirements of UCMR 3 (this was applicable only
to PST). See USEPA (2012a) and USEPA (2019b) for more information on
the UCMR 3 study design and data analysis.
As previously noted, the details of the occurrence data and the
results or findings for each of the contaminants considered for
regulatory determination are presented in Section IV.B, the contaminant
profiles section, and are described in further detail in the Regulatory
Determination 4 Support Document (USEPA, 2019a). 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, 2008b, 2015a,
2019b).
(2) National Inorganics and Radionuclides Survey (NIRS)
The EPA conducted the NIRS to provide a statistically
representative sample of the national occurrence of 36 selected
inorganic compounds (IOCs) and 6 radionuclides in CWSs served by
groundwater. The sample was stratified by system size and 989
groundwater CWSs were selected at random representing 49 states (all
except Hawaii) as well as Puerto Rico. The survey focused on
groundwater systems, in part because IOCs tend to occur more frequently
and at higher concentrations in groundwater 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. 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, 2008c).
Another potential limitation of the NIRS is the age of the data.
Although the NIRS monitoring occurred nearly 35 years ago, results may
still provide insight into current conditions, as the presence of IOCs
in aquifers depends in large part on equilibrium with stable natural
sources in contiguous rock formations.
(3) Unregulated Contaminant Monitoring (UCM) Program Rounds 1 and 2
In 1987, the EPA initiated the UCM program to fulfill a 1986 SDWA
Amendment requirement to monitor for specified unregulated
contaminants. The UCM required PWSs serving more than 500 people to
conduct monitoring. The EPA implemented the UCM program in two phases
or rounds. The first round of UCM monitoring generally extended from
1988 to 1992 and is referred to as UCM Round 1 monitoring. The second
round of UCM monitoring generally extended from 1993 to 1997 and is
referred to as UCM Round 2 monitoring. Information about UCM 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, 2008c).
The UCM-State Round 1 dataset contains PWS monitoring results for
62 then-unregulated contaminants (some have since been regulated).
These data were collected by 40 states and primacy entities between
1988 and 1992. The Round 2 dataset contains PWS monitoring results for
48 then-unregulated contaminants. These data were collected by 35
states and primacy entities between 1993 and 1997. Since UCM Round 1
and Round 2 data represent different time periods and include
occurrence data from different states, the EPA developed separate
national cross-sections for each data set. The UCM Round 1 national
cross-section, consisting of data from 24 states, includes
approximately 3.3 million records from approximately 22,000 unique
PWSs. The UCM Round 2 national cross-section, consisting of data from
20 states, includes approximately 3.7 million records from slightly
more than 27,000 unique PWSs.
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 sources that the EPA used. For individual
contaminants, the 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 the EPA evaluated and the
occurrence data for each contaminant can be found in the Regulatory
Determination 4 Support Document (USEPA, 2019a).
(1) Individual States' Data
For RD 4, the Agency evaluated data for unregulated contaminants
from the second Six-Year Review of regulated contaminants (USEPA,
2009b), the third Six-Year Review of regulated contaminants (USEPA,
2016c), and individual state websites.
To support the second Six-Year Review of regulated contaminants
(USEPA, 2009b), the EPA issued an Information Collection Rule (ICR) to
collect compliance monitoring data from PWSs for the time period
covering 1998-2005. After issuing the ICR, the 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. The EPA
further collected additional unregulated contaminant data from two
additional States that provide monitoring data through their websites.
To support the third Six-Year Review of regulated contaminants
(USEPA, 2016c), the EPA issued an ICR to collect compliance monitoring
data from PWSs for 2006-2011. After issuing the ICR, 46 states and 8
other primacy agencies provided compliance monitoring data. Nine
states, three tribes, Washington, DC, and American Samoa also provided
monitoring data for unregulated contaminants along with their
compliance monitoring data.
The EPA supplemented these occurrence data for unregulated
contaminants by downloading additional and more recent publicly
available monitoring data from state websites. Drinking water
monitoring
[[Page 14112]]
data for select contaminants were available online from several states,
including California, Colorado, Michigan, New Hampshire, New Jersey,
and North Carolina. Very limited data were also available from
Pennsylvania and Washington. The available state data are varied in
terms of quantity and coverage. In many cases they represent targeted
monitoring.
These datasets vary from state to state in the contaminants
included, the number of samples, and the completeness of monitoring.
They were reviewed and used to augment the national data and assessed
if they provide supportive observations or any unique occurrence
results that might warrant further review.
(2) Community Water System Survey (CWSS)
The 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
concentrations 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. The PDP drinking water project
continued until 2013 (USDA, 2018). The CWSs selected for sampling
tended to be small and medium-sized surface water systems (serving
under 50,000 people) located in regions of heavy agriculture. The
sampling frame was designed to monitor in regions of interest for at
least two years to reflect the seasonal and climatic variability during
growing seasons. PDP worked with the EPA to identify specific water
treatment facilities where monitoring data were collected. The number
of sites and samples varied among different sampling periods. The EPA
reviewed the PDP data on the occurrence of select contaminants in
untreated and treated water (USDA, 2018).
(4) USGS Pilot Monitoring Program (PMP)
In 1999, USGS and the 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
finished drinking water taps prior to entering the distribution system.
At some sites, samples were also collected at the reservoir outflow.
(5) 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 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, volatile organic compounds (VOCs), trace elements,
radionuclides, hormones and pharmaceuticals, 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 (2012).
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 6,300
groundwater sampling points. Cycle 2 monitoring covers the period from
2002 through 2012, with various design changes from Cycle 1 (see
Hamilton et al., 2004). Sampling for Cycle 3 is currently underway
(2013-2023). Surface water monitoring will be conducted at 313 sites
while groundwater assessments will be designed to evaluate status and
trends at the principal aquifer and national scales. Refer to Rowe et
al. (2010; 2013) for more details.
The EPA performed a summary analysis of the Cycle 1, Cycle 2, and
available Cycle 3 water monitoring data for the Regulatory
Determination process. The surface water data consisted of river and
stream samples; for groundwater, all well data were used.
For RD 4, the EPA used and evaluated many USGS NAWQA reports to
review causal or spatial factors that USGS may have presented in their
interpretations. In particular, the 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 4, the 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 CWSs (Hopple et al., 2009 and Kingsbury et
al., 2008); water quality in public-supply wells (Toccalino et al.,
2010); water quality in domestic wells and principal aquifers
(DeSimone, 2009 and DeSimone et al., 2014); nationwide reconnaissance
of contaminants of emerging concern (Glassmeyer et al., 2017); water
quality in select CWSs (Grady and Casey, 2001); water quality in
carbonate aquifers (Lindsey et al., 2008); VOCs in domestic wells
(Moran et al., 2002 and Rowe et al., 2007); and VOCs in the nation's
groundwater (Zogorski et al., 2006).
(6) National Water Information System (NWIS)
For RD 4, the EPA evaluated contaminant monitoring results from the
non-NAWQA data in the National Water Information System (NWIS) (USGS,
2016). NWIS houses the NAWQA data (described above) and includes other
USGS data from unspecified projects. The non-NAWQA NWIS data were
analyzed separately from NAWQA data.
[[Page 14113]]
Although NWIS is comprised of primarily ambient water data, some
finished drinking water data are included as well. The non-NAWQA data
housed in NWIS generally involve fewer constituents per sample than the
NAWQA data. Unlike the NAQWA data, the non-NAWQA data are a
miscellaneous collection, so they are not as well-suited for making
temporal and geographic comparisons. Most NWIS data are available via
the Water Quality Portal (see below).
(7) Water Quality Exchange (WQX)/Water Quality Portal Data System
(Formerly STORET)
The EPA's Water Quality Exchange (WQX) is the data format and
mechanism for publishing monitoring data available through the Water
Quality Portal. WQX replaces the Storage and Retrieval Data System
(STORET) as the mechanism for data partners to submit water monitoring
data to the EPA. The Water Quality Portal is the mechanism for anyone,
including the public, to retrieve water monitoring data from the EPA
WQX/STORET, USDA STEWARDS, and USGS NWIS/BIODATA. The WQX database
contains raw biological, chemical, and physical data from surface and
groundwater sampling conducted by federal, state and local agencies,
Native American Tribes, volunteer groups, academics, and others. WQX
includes data from monitoring locations in all 50 states as well as
multiple territories and jurisdictions of the United States. Most data
are from ambient waters, but in some cases finished drinking water data
are included as well. Data owners are responsible for providing data of
documented quality, so that data users can choose to access only those
data collected and analyzed with data quality objectives that meet
their study needs. For more general WQX data information, please refer
to: https://www.epa.gov/waterdata/water-quality-data-wqx. To retrieve
the data, please refer to: https://www.waterqualitydata.us/portal/.
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. Several sources are
described below. A more detailed discussion of the supplemental sources
of information/data that the EPA evaluated and the occurrence data for
each contaminant can be found in the Regulatory Determination 4 Support
Document (USEPA, 2019a).
(1) Inventory Update Reporting (IUR) and Chemical Data Reporting (CDR)
Program
The IUR regulation required 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 was required to 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. In 2011 the Agency issued the CDR Rule, which replaced the IUR
Rule and established a somewhat modified program, including annual data
gathering and periodic reporting. CDR makes use of a two-tiered system
of reporting thresholds, with 25,000 pounds the threshold for some
contaminants and 2,500 pounds the threshold for others. Contaminants
may have reports for some years but not others (USEPA, 2008d; USEPA,
2016d).
(2) Toxics Release Inventory (TRI)
The 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
annual information on toxic chemical releases from facilities that meet
reporting criteria to both the EPA and the states. 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, 2003b; USEPA, 2019c). Currently, for most
chemicals, reporting of releases is required if 25,000 pounds or more
of the chemical are manufactured or processed at a facility, or if
10,000 pounds or more are used at the facility. For certain chemicals
the reporting threshold is as low as 0.1 grams, 10 pounds, or 100
pounds (40 CFR 372.28). Both the number and type of facilities required
to report has increased over time. Information from the TRI was
downloaded in 2017 (USEPA, 2017a).
Although TRI can provide a general idea of release trends, these
trends should be interpreted with caution since the list of chemicals
with reporting requirements has generally increased over time. In
addition, only those facilities that meet specific criteria are
required to report to the TRI program. Finally, data on releases cannot
be used as a direct measure of public exposure to a chemical in
drinking water (USEPA, 2019a).
(3) Pesticide Usage Estimates
For the regulatory determinations process, the Agency reviews
various sources of information about pesticide usage. Pesticide use and
manufacturing information is considered confidential business
information (CBI) and therefore, accurate measures of production and
use are not publicly available. As a result, the Agency reviews various
estimates of use as supplemental information in the deliberative
process.
For some pesticides, the EPA presents estimations of annual U.S.
usage of individual pesticides in its pesticide reregistration
documents (e.g., REDs, IREDs, TREDs). The 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 (USEPA, 2004a; USEPA, 2011c;
USEPA, 2017b).
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, 2018). These pesticide use
estimates were generated by the USGS using data from proprietary
surveys of farm operations, USDA Census of Agriculture, and other
[[Page 14114]]
sources. USGS used two methods to estimate pesticide usage, since
pesticide usage information was not available in some districts.
``EPest-High'' estimates were generated by projecting usage estimates
for such districts based on usage in neighboring districts. ``EPest-
Low'' estimates were generated by assuming no usage in such districts.
IV. Contaminant-Specific Discussions for the RD 4 Preliminary
Determination
A. Summary of the Preliminary Regulatory Determination
Based on the EPA's evaluation of the three SDWA criteria (discussed
in section II.B.1), the Agency is making preliminary determinations to
regulate two contaminants and to not regulate six contaminants. For
each of the eight contaminants discussed in this section of this
document, Table 7 summarizes information about the health assessment,
principle study, critical effects, and associated reference dose and/or
cancer slope factor used to derive an HRL. Following Table 7, Table 8
summarizes the primary occurrence information used to make these
preliminary regulatory determinations. Section IV.B of this document
provides a more detailed summary of the information and the rationale
used by the Agency to reach its preliminary decisions for these eight
contaminants. For more information about the two Phase 3 contaminants
that are not receiving a preliminary regulatory determination, see
section V.
Table 7--Health Effects Information for Contaminants Discussed in Section IV of This Document
--------------------------------------------------------------------------------------------------------------------------------------------------------
RfD for
noncancer Cancer slope
RD 4 contaminant Health assessment Principle study Critical effect effects, in mg/ factor, in (mg/ HRL, in [micro]g/L
kg/day kg/day) -1
--------------------------------------------------------------------------------------------------------------------------------------------------------
PFOS............................. EPA OW HESD, 2016.. Luebker et al. decreased neonatal rat 0.00002 n/a 0.07.
2005a and 2005b. body weight.
PFOA............................. EPA OW HESD, 2016.. Lau et al., 2006... reduced ossification 0.00002 \20\ 0.07 0.07.
in proximal phalanges
and accelerated
puberty in male pups,
in mice.
1,1-Dichloroethane............... EPA ORD PPRTV, 2006 Muralidhara et al., increased urinary 0.2 n/a 1,000.
2001. enzyme markers for
renal damage and
central nervous
system (CNS)
depression in rats.
Acetochlor....................... EPA OPP HHRA, 2018. ICI, Inc. 1988..... increased salivation, 0.02 n/a 100.
increased alanine
aminotransferase
(ALT), ornithine
carbamyl transferase
and triglyceride
levels; decreased
blood glucose; and
histopathological
changes in the
kidneys, liver and
testes of males, in
beagle dogs.
Methyl Bromide (Bromomethane).... EPA OPP HHRA, 2006. Mertens, 1997...... decreased body weight, 0.022 n/a 100.
decreased rate of
body weight gain, and
decreased food
consumption in rats.
Metolachlor...................... EPA OPP HHRA, 2018. Page, 1981......... decreased pup body 0.26 n/a 300.
weight in rats.
Nitrobenzene..................... EPA IRIS, 2009..... NTP, 1983.......... changes in absolute 0.002 n/a 10.
and relative organ
weights, splenic
congestion, and
increases in
reticulocyte count
and metHb
concentration in rats.
RDX.............................. EPA IRIS, 2018..... Crouse et al., 2006 convulsions in rats 0.004 0.08 30 (noncancer); 0.4
(noncancer); Lish (noncancer); lung and (cancer).
et al. 1984 liver tumors in mice
(cancer). (cancer).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 8--Occurrence Findings From Primary Data Sources
--------------------------------------------------------------------------------------------------------------------------------------------------------
Population served Population served
PWSs with at least by PWSs with at PWSs with at least by PWSs with at
RD 4 contaminant HRL, [micro]g/L Primary database 1 detection > \1/ least 1 detection 1 detection > HRL least 1 detection
2\ HRL > \1/2\ HRL > HRL
--------------------------------------------------------------------------------------------------------------------------------------------------------
PFOS............................ 0.07............. UCMR 3 AM.......... 95/4,920 (1.93%).. 10,427,193/241 M 46/4,920 (0.93%).. 3,789,831/241 M
(4.32%). (1.57%).
PFOA............................ 0.07............. UCMR 3 AM.......... 53/4,920 (1.07%).. 3,652,995/241 M 13/4,920 (0.26%).. 490,480/241 M
(1.51%). (0.20%).
1,1-Dichloroethane.............. 1,000............ UCMR 3 AM.......... 0/4,916 (0.00%)... 0/241 M (0.00%)... 0/4,916 (0.00%)... 0/241 M (0.00%).
Acetochlor...................... 100.............. UCMR 1 AM.......... 0/3,869 (0.00%)-- 0/226 M (0.00%)-- 0/3,869 (0.00%)-- 0/226 M (0.00%)--
UCMR 1. UCMR 1. UCMR 1. UCMR 1.
UCMR 2 SS.......... 0/1,198 (0.00%)-- 0/157 M (0.00%)-- 0/1,198 (0.00%)-- 0/157 M (0.00%)--
UCMR 2. UCMR 2. UCMR 2. UCMR 2.
Methyl Bromide (Bromomethane)... 100.............. UCMR 3 AM.......... 0/4,916 (0.00%)... 0/241 M (0.00%)... 0/4,916 (0.00%)... 0/241 M (0.00%).
Metolachlor..................... 300.............. UCMR 2 SS.......... 0/1,198 (0.00%)... 0/157 M (0.00%)... 0/1,198 (0.00%)... 0/157 M (0.00%).
Nitrobenzene.................... 10............... UCMR 1 AM.......... 2/3,861 (0.05%)... 255,358/226 M 2/3,861 (0.05%)... 255,358/226 M
(0.11%). (0.11%).
RDX............................. 30, 0.4.......... UCMR 2 AM.......... 0/4,139 (0.00%) > 0/229 M (0.00%) > 0/4,139 (0.00%) > 0/229 M (0.00%) >
15 [micro]g/L. 15 [micro]g/L. 30 [micro]g/L. 30 [micro]g/L.
[[Page 14115]]
3/4,139 (0.07%) > 96,033/229 M 3/4,139 (0.07%) > 96,033/229 M
0.2 [micro]g/L. (0.04%) > 0.2 0.4 [micro]g/L. (0.04%) > 0.4
[micro]g/L. [micro]g/L.
--------------------------------------------------------------------------------------------------------------------------------------------------------
B. Contaminant Profiles
---------------------------------------------------------------------------
\20\ Using the CSF, the calculated concentration in drinking
water with one-in-a-million risk for an increase in testicular
tumors at levels greater than background is 0.0005 mg/L.
The equivalent concentration derived from the RfD is lower than
the concentration of 0.0005 mg/L associated with a one-in-a-million
risk for testicular cancer indicating that a guideline derived from
the developmental endpoint will be protective for the cancer
endpoint. (USEPA, 2016g).
---------------------------------------------------------------------------
1. Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA)
a. Background
PFAS are a group of synthetic chemicals that have been in use since
the 1940s. PFAS are found in a wide array of consumer and industrial
products. PFAS manufacturing and processing facilities, facilities
using PFAS in production of other products, airports, and military
installations have been associated with PFAS releases into the air,
soil, and water (USEPA, 2016e; USEPA, 2016f).
PFOS and PFOA--two of the most widely-studied and longest-used
PFAS--are part of a subset of PFAS known as perfluorinated alkyl acids
(PFAA). These two compounds have been detected in up to 98% of serum
samples taken in biomonitoring studies that are representative of the
U.S. general population; however, since PFOA and PFOS have been
voluntarily phased out in the U.S., serum concentrations have been
declining (CDC, 2019). The National Health and Nutrition Examination
Survey (NHANES) data shows that 95th-percentile serum PFOS
concentrations have decreased from 75.7 [micro]g/L in the 1999-2000
cycle to 18.3 [micro]g/L in the 2015-2016 cycle (CDC, 2019; Jain, 2018;
Calafat et al., 2007; Calafat et al., 2019), a decrease of over 75
percent. In early 2000, the EPA worked with the 3M Company, which was
the only major manufacturer of PFOS in the United States at that time,
to support the company's voluntary phase-out and elimination of PFOS
production and use. Under the EPA's 2010/2015 PFOA Stewardship Program,
eight major chemical manufacturers and processors agreed to phase out
the use of PFOA and PFOA-related chemicals in their products and
emissions from their facilities. All companies met the PFOA Stewardship
Program goals by 2015. While companies participating in the PFOA
Stewardship program report that they no longer produce or use PFOA
domestically, PFOA may still be produced domestically or imported or
used by companies not participating in the PFOA Stewardship Program. In
addition, PFOA and PFOS can also be present in imported articles
(USEPA, 2017c). Due to the widespread use and persistence of PFAS in
the environment, most people have been exposed to PFAS, including PFOA
and PFOS (USEPA, 2016e; USEPA, 2016f).
Production of PFOA and PFOS is subject to CDR reporting. Production
volumes of PFOA and PFOS were claimed by reporting companies as
confidential for the most recent reporting cycles. The last time
production (including import) of PFOA exceeded the CDR reporting
threshold was during the 2016 reporting cycles (which includes
production information from 2012-2015) and it was phased out by
companies participating in the 2010/2015 PFOA Stewardship Program in
2013. Similarly, PFOS was phased out by 3M in 2002 and the most
recently reported data for PFOS are from the 2002 reporting cycle
(which includes production information from 2001 only) (USEPA, 2019a).
Absence of recent reporting may indicate that production (including
import) of PFOA and PFOS has halted or has been below the CDR reporting
thresholds. Although PFOA and PFOS are not produced domestically or
imported by the companies participating in the 2010/2015 PFOA
Stewardship Program, PFOA and PFOS may still be produced domestically
or imported below the CDR reporting thresholds (i.e., 2,500 pounds) by
companies not participating in the PFOA Stewardship Program.
b. Statutory Criterion #1 (Adverse Health Effects)
The EPA is preliminarily determining that PFOA and PFOS meet the
SDWA statutory criterion #1 for regulatory determinations: They may
have adverse effects on the health of persons. In 2016, the EPA
published health assessments (health effects support documents or
HESDs) for PFOA and PFOS based on the Agency's evaluation of the peer
reviewed science available at that time. This section presents a
summary of the adverse health effects discussed in the HESDs. For
specific details on the potential for adverse health effects and
approaches used to identify and evaluate information on hazard and
dose-response, please see USEPA (2016d), USEPA (2016e), USEPA (2016f),
and USEPA (2016g). The lifetime HA of 0.07 [micro]g/L is used as the
HRL for Regulatory Determination 4.
Human epidemiology data report associations between PFOA exposure
and high cholesterol, increased liver enzymes, decreased vaccination
response, thyroid disorders, pregnancy-induced hypertension and
preeclampsia, and cancer (testicular and kidney). The associations for
most epidemiology endpoints are mixed. Although mean serum values are
presented in the human studies, actual estimates of PFOA exposure
(i.e., doses/duration) are not currently available. Thus, the serum
level at which the effects were first manifest and whether the serum
had achieved steady state at the point the effect occurred cannot be
determined. It is likely that some of the human exposures that
contribute to serum PFOA values come from PFOA derivatives or
precursors that break down metabolically to PFOA. These compounds could
originate from PFOA in diet and materials used in the home, which
creates potential for confounding. In addition, most of the subjects of
the epidemiology studies have many PFASs and/or other contaminants in
their blood. Although the study designs adjust for other potential
toxicants as confounding factors, their presence constitutes a level of
uncertainty that is usually absent in the animal studies. Taken
together, the weight of evidence for human studies supports the
conclusion that PFOA exposure is a human health hazard. At this time,
EPA concludes that the human studies are adequate for use qualitatively
in the identification hazard and are supportive of the findings in
laboratory animals.
[[Page 14116]]
For PFOA, oral animal studies of short-term, subchronic, and
chronic duration are available in multiple species including monkeys,
rats and mice. These animal studies report developmental effects
(survival, body weight changes, reduced ossification, delays in eye
opening, altered puberty, and retarded mammary gland development),
liver toxicity (hypertrophy, necrosis, and effects on the metabolism
and deposition of dietary lipids), kidney toxicity (weight), immune
effects, and cancer (liver, testicular, and pancreatic) (USEPA, 2016e).
Overall, the animal toxicity studies available for PFOA demonstrate
that the developing fetus is particularly sensitive to PFOA-induced
toxicity. Human epidemiology data report associations between PFOA
exposure and high cholesterol, increased liver enzymes, decreased
vaccination response, thyroid disorders, pregnancy-induced hypertension
and preeclampsia, and cancer (testicular and kidney). Overall, the
developmental toxicity studies in animals available for PFOA
demonstrate that the developing rodent fetus and newborn rodent are
sensitive to PFOA-induced toxicity.
PFOA is known to be transmitted to the fetus via cord blood and to
the newborn, infant, and child via breast milk (USEPA, 2016f). Under
the EPA's Guidelines for Carcinogen Risk Assessment (USEPA, 2005b),
there is ``suggestive evidence of carcinogenic potential'' for PFOA.
Similarly, the International Agency for Research on Cancer (IARC)
classifies PFOA as ``possibly carcinogenic to humans'' (IARC, 2019a;
IARC, 2019b).
The EPA calculated several candidate RfDs for PFOA in the 2016 HESD
and selected the RfD of 0.00002 mg/kg/day based on reduced ossification
in proximal phalanges and accelerated puberty in male pups following
exposure during gestation and lactation in a developmental toxicity
study in mice (Lau et al., 2006) for the derivation of a lifetime HA.
The RfD for PFOA was calculated by applying uncertainty factors to
account for interspecies variability (3), intraspecies differences
(10), and use of a LOAEL (3). The Health Effects Support Document
(USEPA, 2016h) describes these uncertainties in Section 4.
Additionally, uncertainties and limitations (i.e., human
epidemiological data, immunological and mammary gland endpoints, and
exposure) are discussed in detail in Section 8 of the Health Advisory
(USEPA, 2016f) document. The lifetime HA of 0.07 [micro]g/L was
calculated using the 0.00002 mg/kg/day RfD for developmental effects, a
DWI to BW ratio for the 90th percentile \21\ for lactating women (0.054
L/kg/day) and a calculated 20% RSC (USEPA, 2016f). This RfD is
protective of effects other than those occurring during development
such as kidney and immune effects. Because of the potential for
increased susceptibility during the time period of pregnancy and
lactation observed in this study, the EPA used DWI and BW parameters
for lactating women in the calculation of a lifetime HA for this target
population during this potential critical time period. The EPA also
calculated a CSF of 0.07 (mg/kg/day)-\1\ based on testicular
tumors in rats. The resultant HA using this CSF is greater than the
lifetime HA based on noncancer effects, indicating that the HA derived
based on the developmental endpoint is protective for the cancer
endpoint (USEPA, 2016h).
---------------------------------------------------------------------------
\21\ Consumers only estimate of combined direct and indirect
community water ingestion; see Table 3-81 in USEPA, 2011b.
---------------------------------------------------------------------------
For PFOS, epidemiological studies have reported associations
between PFOS exposure and high serum cholesterol and reproductive and
developmental parameters. The strongest associations are related to
serum lipids with increased total serum cholesterol and high-density
lipoproteins (HDLs). As with PFOA, the associations for most
epidemiology endpoints are inconsistent. Although mean serum values are
presented in the human studies, actual estimates of PFOS exposure
(i.e., doses/duration) are not currently available. Thus, the serum
level at which the effects were first manifest and whether the serum
had achieved steady state at the point the effect occurred cannot be
determined (USEPA, 2016e) Human epidemiological studies suggest an
association between higher PFOS levels and decreases in female
fecundity and fertility, decreased birth weights in offspring and other
measures of postnatal growth (e.g., small for gestational age).
Short-term and chronic exposure studies in animals demonstrate
increases in liver weight consistently. Co-occurring effects in these
studies include decreased cholesterol, hepatic steatosis, lower body
weight, and liver histopathology. One and two generation toxicity
studies also show decreased pup survival and body weights.
Additionally, developmental neurotoxicity studies show increased motor
activity and decreased habituation and increased escape latency in the
water maze test following in utero and lactational exposure to PFOS.
Gestational and lactational exposures were also associated with higher
serum glucose levels and evidence of insulin resistance in adult
offspring. Limited evidence suggests immunological effects in mice.
Short-term and subchronic duration studies are available in multiple
animal species including monkeys, rats and mice. These studies also
found increased serum glucose levels and insulin resistance in adult
animals exposed during development, developmental effects (decreased
body weight and survival), reproductive effects (impacts on mating
behavior), liver toxicity (increased liver weight co-occurring with
decreased serum cholesterol, hepatic steatosis), developmental
neurotoxicity (impaired spatial learning and memory), suppressed
immunological responses, and cancer (thyroid and liver). Increased
incidence of hepatocellular adenomas in the male (12% at the high dose)
and female rats (8% at the high dose) and combined adenomas/carcinomas
in the females (10% at the high dose) were observed, but they did not
display a clear dose-related response; Thyroid tumors (adenomas and
carcinomas) were seen in males receiving 0, 0.5, 2, 5, or 20 ppm and in
females receiving 5 or 20 ppm in their diet. The tumor (adenomas +
carcinomas) prevalence for males was consistent across dose groups. In
males the incidence of thyroid tumors was significantly elevated only
in the high-dose, recovery group males exposed for 52 weeks (10/39) but
not in the animals receiving the same dose at 105 weeks. There were
very few follicular cell adenomas/carcinomas in the females (5 total)
with no dose-response. The most frequent thyroid tumor type in the
females was C-cell adenomas, but the highest incidence was that for the
controls and there was a lack of dose response among the exposed
groups. C-cell adenomas were not observed in males (Thomford 2002;
Butenhoff et al. 2012). Overall, the animal toxicity studies available
for PFOS demonstrate that the developing fetus and newborn rodent are
sensitive to PFOS induced toxicity. PFOS is known to be transmitted to
the fetus via cord blood and to the newborn, infant, and child via
breast milk (USEPA, 2016f). Applying the EPA Guidelines for Carcinogen
Risk Assessment (USEPA, 2005b), there is suggestive evidence of
carcinogenic potential for PFOS. However, the weight of evidence for
humans is too limited to support a quantitative cancer assessment given
that there was no evidence for dose-response from which to derive a
slope factor for the tumor types identified in animals.
[[Page 14117]]
The EPA calculated multiple candidate RfDs for PFOS in the HESD and
selected the RfD of 0.00002 mg/kg/day based on decreased neonatal rat
body weight from both the one- and two-generation studies by Luebker et
al. (2005a, 2005b) for the derivation of a lifetime HA. The RfD for
PFOS was calculated by applying uncertainty factors to account for
interspecies variability (3) and intraspecies differences (10). The
Health Effects Support Document (USEPA, 2016g) describes these
uncertainties in Section 4. Additionally, uncertainties and limitations
(i.e., human epidemiologic data, immunological and mammary gland
endpoints, and exposure) are discussed in detail in Section 8 of the
Health Advisory (USEPA, 2016e) document. The lifetime HA of 0.07
[micro]g/L was calculated using the 0.00002 mg/kg/day RfD for
developmental effects, a DWI to BW ratio for the 90th percentile \21\
for lactating women (0.054 L/kg/day) and a 20% RSC (USEPA, 2016e). The
lifetime HA of 0.07 [micro]g/L is used as the HRL for Regulatory
Determination 4.
The RfDs for both PFOA and PFOS are both based on developmental
effects and are numerically identical. Thus, when both chemicals co-
occur at the same time and location, the EPA recommended a conservative
and health-protective approach of 0.07 [micro]g/L for the PFOA/PFOS
total combined concentration (USEPA, 2016e).
The EPA has initiated a systematic literature review of peer-
reviewed scientific literature for PFOA and PFOS published since 2013
with the goal of identifying any new studies that may be relevant to
human health assessment. An annotated bibliography of identified
studies as well as the protocol used to identify the relevant
publications can be found in Appendix D of the Regulatory Determination
4 Support Document (USEPA, 2019a), available in the docket for this
document. Additional analyses of these new studies is needed to confirm
relevance, extract the data to assess the weight of evidence, and
identify critical studies in order to inform future decision making.
The EPA is seeking comment on any additional studies and information
that it should consider. Should the EPA make a final positive
regulatory determination for PFOA and PFOS, the Agency will undertake
the SDWA rulemaking process to establish a National Primary Drinking
Water Regulation for those contaminants. For that rulemaking effort, in
addition to using the best available science, the SDWA requires that
the Agency seek recommendations from the EPA Science Advisory Board,
and consider public comment on any proposed rule. Therefore, EPA
anticipates further scientific review of new science prior to
promulgation of any regulatory standard.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public
Health Concern)
The EPA is preliminarily determining that PFOA and PFOS meet the
SDWA statutory criterion #2 for regulatory determinations: they occur
with a frequency and at levels of public health concern at PWSs based
on the EPA's evaluation of the available occurrence information. The
EPA is seeking public comment on whether the data described below
support such a determination and whether additional data or studies
exist which EPA should consider when finalizing a determination.
EPA has made its preliminary determination based, in part, on the
UCMR 3 data (USEPA, 2019b). The EPA has determined in accordance with
SDWA 1412(b)(1)(B)(ii)(II) that the UCMR 3 data are the best available
occurrence information for the PFOA/PFOS regulatory determinations.
UCMR 3 monitoring occurred between 2013 and 2015and currently
represents the only nationally-representative finished water dataset
for PFOA and PFOS. Under UCMR 3, 36,972 samples from 4,920 PWSs were
analyzed for PFOA and PFOS. The MRL for PFOA was 0.02 [micro]g/L and
the MRL for PFOS was 0.04 [micro]g/L. A total of 1.37% of samples had
reported detections (greater than or equal to the MRL) of at least one
of the two compounds. To examine the occurrence of PFOS and PFOA in
aggregate, the EPA summed the concentrations detected in the same
sample to calculate a total PFOS/PFOA concentration.
The EPA notes that when these two chemicals co-occur at the same
time and location in a drinking water source, a conservative and
health-protective approach that EPA recommends would be to compare the
sum of the concentrations (USEPA, 2016g; USEPA, 2016h). The Regulatory
Determination 4 Support Document presents a sample-level summary of the
results for the individual contaminants (USEPA, 2019a). Concentrations
of PFOS or PFOA below their respective MRLs were set equal to 0
[micro]g/L when calculating the total PFOS/PFOA concentration for the
sample. The maximum summed concentration of PFOA and PFOS was 7.22
[micro]g/L and the median summed value was 0.05 [micro]g/L. Summed PFOA
and PFOS concentrations exceeded the HRL (0.07 [micro]g/L) at a minimum
of 1.3% of PWSs (63 PWSs \22\). Since UCMR 3 monitoring occurred,
certain sites where elevated levels of PFOA and PFOS were detected may
have installed treatment for PFOA and PFOS, may have chosen to blend
water from multiple sources, or may have otherwise remediated known
sources of contamination. Those 63 PWSs serve a total population of
approximately 5.6 million people and are located in 25 states, tribes,
or U.S. territories (USEPA, 2019b). The HRLs for PFOA and PFOS are
based on the 2016 drinking water Health Advisories and reflect
concentrations of PFOA and PFOS in drinking water at which adverse
health effects are not anticipated to occur over a lifetime (USEPA,
2016e; USEPA, 2016f).
---------------------------------------------------------------------------
\22\ Sum of PFOA + PFOS results rounded to 2 decimal places in
those cases where a laboratory reported more digits.
---------------------------------------------------------------------------
Consistent with the Agency's commitment in the PFAS Action Plan
(USEPA, 2019d) to present information about additional sampling for
PFAS in water systems, the EPA has supplemented its UCMR data with data
collected by states who have made their data publicly available at this
time. In some cases, EPA obtained the data directly from the state's
public website while, in others, these data were provided to EPA.
Specifically, the EPA evaluated publicly available monitoring data that
permitted summed PFOA and PFOS analyses from the state websites of New
Hampshire, Colorado, and Michigan. Additional finished drinking water
monitoring data was provided to the EPA by the New Jersey Department of
Environmental Protection. These data are summarized in Table 9 below.
The EPA notes that some of these data are from targeted sampling
efforts and thus may not be representative of occurrence in the state.
The EPA also notes that states which chose to make their occurrence
data publicly available and the state that chose to provide its data to
the EPA may not necessarily represent occurrence in other states. The
Regulatory Determination 4 Support Document presents a detailed
discussion of additional information from states on occurrence of these
contaminants in drinking water systems (USEPA, 2019a). The EPA is also
aware that some of these states may have updated data available and
that additional states have or intend to conduct monitoring of finished
drinking water, such as Illinois, Pennsylvania, and Vermont. The EPA
will consider any data submitted in response to this proposal to inform
future regulatory decision making. The EPA is also aware of additional
locations with drinking
[[Page 14118]]
water impacts (including private wells) from contaminated sites. These
include sites near production facilities, active and former military
bases, and other point sources.\23\
---------------------------------------------------------------------------
\23\ Examples include Chemours Washington Works Facility, West
Virginia (production facilities), Horsham Air National Guard
Station, Pennsylvania and former Wurtsmith Air Force Base, Michigan
(active and former military bases), and non-military firefighting
activities (other point sources).
\24\ Some of these data in these tables are from targeted
sampling efforts and therefore, would be expected to have higher
detection rates than a random sample.
---------------------------------------------------------------------------
For the following summed PFOA and PFOS analyses, monitoring data
sets from public water systems in New Hampshire and New Jersey
permitted combined analysis of PFOS and PFOA occurrence (i.e., with
paired PFOS and PFOA concentrations reported for each individual water
sample). In addition, Colorado and Michigan directly reported
monitoring results for combined PFOS and PFOA. All states data sets
summarized in Table 9 had at least one instance of summed PFOS and PFOA
concentrations greater than the HRL of 0.07 [micro]g/L. Additional
details can be found in the Regulatory Determination 4 Support Document
(USEPA, 2019a).
Table 9--Combined PFOS and PFOA Occurrence: Summary of State Monitoring Results \24\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Type of water
State (reference) Date range tested Notes on coverage Summary of results Survey type
--------------------------------------------------------------------------------------------------------------------------------------------------------
Colorado (CDPHE, 2018) 2013-2017......... Surface Water Data available from 28 The maximum summed Targeted.
(Finished Water) ``drinking water distribution concentration of PFOA
and Drinking zones'' (one or more per public and PFOS was 0.3
Water water system) in targeted [micro]g/L and the
Distribution sampling efforts at a known median summed value
Samples. contaminated aquifer region. was 0.09 [micro]g/L.
Data were collected by El Paso Summed PFOA and PFOS
County Public Health, local concentrations
water districts and utilities, exceeded the EPA HRL
and the Colorado Department of (0.07 [micro]g/L) at
Public Health and Environment 25% of distribution
(CDPHE). Results represent data zones (7 distribution
collected in a targeted region. zones).
Detection limits ranged from
0.002 [micro]g/L to 0.040
[micro]g/L.
Michigan (Michigan EGLE, 2019) 2018-2019......... Groundwater and Data available from 1,119 public The maximum summed Statewide.
Surface Water-- community water systems, concentration of PFOA
Raw and Finished downloaded in October 2019. and PFOS was 1.52
Water (Community Results are from the Michigan [micro]g/L and the
Water Supplies). Department of Environment, median summed value
Great Lakes and Energy (EGLE) was 0.004 [micro]g/L.
statewide sampling efforts for Summed PFOA and PFOS
PFAS of drinking water from concentrations
community water supplies. exceeded the EPA HRL
Results are presented for the (0.07 [micro]g/L) at
sum of PFOA and PFOS 0.09% of PWSs (1 PWS).
concentrations. Information on
detection limits was not
available.
New Hampshire (NHDES, 2017) 2013-2017......... Groundwater and Data available online from 295 The maximum summed Targeted.
Surface Water. PWSs providing results to NH, concentration of PFOA
including PWSs near and PFOS was 0.242
contaminated sites. Results [micro]g/L and the
represent all PFOA and PFOS median summed value
water quality data reported to was 0.006 [micro]g/L.
New Hampshire Department of Summed PFOA and PFOS
Environmental Services (NHDES) concentrations
through May 3, 2017. There is exceeded the EPA HRL
no discussion of (0.07 [micro]g/L) at
representativeness. Detection 1.01% of PWSs (3
limits ranged from 0.0005 PWSs).
[micro]g/L to 0.04 [micro]g/L.
New Jersey (NJDEP, 2019) 2019.............. Groundwater and Statewide sampling of finished The maximum summed Statewide.
Surface Water-- drinking water data between concentration of PFOA
Finished Water. January 1, 2019 and June 28, and PFOS was 1.09
2019. These represent the first [micro]g/L and the
two quarters of statewide median summed value
efforts to sample of finished was 0.01 [micro]g/L.
drinking water. Under this Summed PFOA and PFOS
sampling effort, 2,459 water concentrations
samples from 1,049 PWS were exceeded the EPA HRL
analyzed for PFOA and PFOS. (0.07 [micro]g/L) at
Detection limits ranged from 1.14% of PWSs (12
0.0016 [hyphen] 0.0046 (doesn't PWSs).
specify for which PFAS
compound).
--------------------------------------------------------------------------------------------------------------------------------------------------------
In addition to the monitoring data available from public water
systems, North Carolina has made data from 17 private wells associated
with the Chemours facility in Fayetteville available (NCDEQ, 2018). The
maximum combined PFOS and PFOA concentration was 0.0319 [mu]g/L, while
the median was 0.004 [mu]g/L. Summed PFOS and PFOA concentrations did
not exceed the EPA HRL (0.07 [mu]g/L) at any of the sampling sites.
Note that the EPA does not regulate private drinking water wells but
may evaluate data from private wells where the data may be indicative
of contaminants in aquifers that are used as sources for public water
system wells.
UCMR 3 data have also been used by researchers to evaluate co-
occurrence of PFAS in drinking water at PWSs. For example, Guelfo and
Adamson (2018) investigated PFAS data from UCMR 3 for occurrence and
co-contaminant mixtures, trends in PFAS detections relative to PWS
characteristics and potential release types, and temporal trends in
PFAS occurrence. The study identified that approximately 50% of samples
with PFAS detections contained [gteqt]2 PFASs, and 72% of detections
occurred in groundwater. Large PWSs (>10,000 customers) were 5.6 times
more likely than small PWSs (<=10,000 customers) to exhibit PFAS
detections; however, when detected, median total PFAS concentrations
were higher in small PWSs (0.12 [mu]g/L) than in large (0.053 [mu]g/L).
Hu et al. (2016) presented spatial analysis of PFAS concentrations
under UCMR 3 and found that the number of industrial sites
[[Page 14119]]
that manufacture or use these compounds, the number of military fire
training areas, and the number of wastewater treatment plants are all
significant predictors of PFAS detection frequencies and concentrations
in public water supplies. The authors found that for PFAS monitored
under UCMR 3, the detection frequency in drinking water sourced from
groundwater was more than twice that from surface water. Additionally,
PFOA and PFOS were more frequently detected in groundwater whereas UCMR
3 PFAS compounds with shorter chain lengths were detected more
frequently in surface waters. Hu et al. (2016) noted that this
observation could be due to the original mode of environmental release
(aerosol, application to soil, and aqueous discharge).
The state data (as presented above and discussed in the Regulatory
Determination 4 Support Document), while some are from targeted
sampling efforts and therefore, would be expected to have higher
detection rates than a random sample, show occurrence in multiple
geographic locations consistent with what was observed during UCMR 3
monitoring. Additionally, some state monitoring efforts show detections
above the EPA Health Advisory in water systems that were not required
to conduct monitoring in the UCMR 3. EPA believes that these data
support the Agency's preliminary determination that PFOA and PFOS occur
with a frequency and at levels of public health concern in drinking
water systems across the United States. Additional details of the EPA
analyses of UCMR 3 monitoring data for PFAS can be found in the
Regulatory Determination 4 Support Document (USEPA, 2019a). The EPA
requests comment on whether there are additional occurrence data sets
that it can use to supplement the analyses already performed and inform
its determination, including more recent data from specific data sets
mentioned above.
d. Statutory Criterion #3 (Meaningful Opportunity)
The EPA conducted extensive public outreach in the development of
the PFAS Action Plan, including gathering diverse perspectives through
the May 2018 National Leadership Summit, direct engagement with the
public in impacted communities in five states, engagement with tribal
partners, and roundtables conducted with community leaders near
impacted sites. In addition, the Agency reviewed approximately 120,000
comments in the public docket that was specifically established to
gather input for the Action Plan (USEPA, 2019d). Through these
engagements, the EPA heard significant concerns from the public on the
challenges these contaminants pose for communities nationwide and the
need for uniform, protective drinking water regulations across the
United States.
Based on the significant public interest in the potential risks
posed by PFOA and PFOS, and the information currently available to the
EPA, the Administrator has made the preliminary determination that
regulation of PFOA and PFOS presents a meaningful opportunity for
health risk reduction for persons served by PWSs. In determining that
regulation of PFOA and PFOS presents a meaningful opportunity for
health risk reduction for sensitive populations, the EPA was
particularly mindful that PFOA and PFOS are known to be transmitted to
the fetus via cord blood and to the newborn, infant, and child via
breast milk (USEPA, 2016f).
Data from recent state monitoring efforts validate the UCMR 3
monitoring results (USEPA, 2019b; NJ DEP, 2019). Sun et al. observed
similar temporal trends in their investigation in the Cape Fear
Watershed of North Carolina, where PFAS concentrations remained similar
between 2006 and 2013 (Sun et al., 2016). These observations suggest
that PFOA and PFOS can be persistent in the environment, lack
attenuation processes that would degrade these compounds over time and
may be subject to precursor transformations. The EPA believes PFOA and
PFOS occur at a frequency and at levels of public health concern. UCMR
3 indicates 1.3% of PWSs (63 PWSs) monitored reported combined PFOA/
PFOS above the HRL. These systems serve a total population of
approximately 5.6 million people. While this preliminary regulatory
determination is based, in part, on the UCMR occurrence data, it is
also based on additional factors discussed above.
State data (as described above and discussed in the Regulatory
Determination 4 Support Document) support the UCMR results, and the
Agency's determination that PFOA and PFOS occur with a frequency and at
levels of public health concern in finished drinking water across the
United States, with some results substantially elevated above the EPA's
HAs. These data have also identified PFAS contamination in other
locations, such as in small, previously unmonitored systems, beyond
where the UCMR 3 required water systems to conduct monitoring. Due to
the anthropogenic nature of PFOA and PFOS and their persistence in the
environment, multiple localized areas of contamination across the
country may be a significant contributor to drinking water
contamination. The state data sets summarized in Table 9 had at least
one instance of summed PFOS and PFOA concentrations greater than the
HRL of 0.07 [micro]g/L. While many detections are marginally above the
EPA HA levels, there are many instances where localized samples
substantially exceed the HA levels, sometimes by 2-3 orders of
magnitude (i.e., a maximum summed concentration as high as 1.52 [mu]g/
L). The EPA believes there is significant public health risk reduction
potential in the localized areas with these significantly elevated
concentrations. To assess communities with the highest exposures, the
ATSDR has begun to perform PFAS exposure assessments in communities
near current or former military bases with elevated concentrations of
PFAS detected in drinking water (ATSDR, 2019a).
Adverse effects observed following exposures to PFOA and PFOS are
the same or similar and include effects in humans on serum lipids,
birth weight, and serum antibodies. Some of the animal studies show
common effects on the liver, neonate development, and responses to
immunological challenges. Both compounds were also associated with
tumors in long-term animal studies (USEPA, 2016g; USEPA, 2016h). States
have taken action to reduce exposures (as further discussed below).
Some states have established regulatory or guidance levels in drinking
water for PFOA, PFOS, as well as other PFAS (ASDWA, 2019). Moving
forward with a national-level regulation for PFOA and PFOS may provide
additional national consistency and reduce regulatory uncertainty for
stakeholders across the country.
PFOA and PFOS are resistant to environmental degradation processes
such as hydrolysis, photolysis, and biodegradation and are thus highly
persistent in the environment (USEPA, 2019a). In addition, biotic and
abiotic processes can degrade PFAS precursors to form PFAAs such as
PFOA and PFOS over time and thus are also important contributors to the
presence and persistence of these chemicals in the environment (ITRC,
2018). Additionally, PFOA and PFOS are expected to have a high
likelihood of partitioning to water based on their ionic nature at
typical environmental pH and their organic carbon partitioning
coefficients (Koc). PFOA has a high likelihood of
partitioning to water based on its water solubility while the water
solubility of PFOS anion indicates a moderate likelihood of
partitioning to water.
[[Page 14120]]
Therefore, PFOA and PFOS have high mobility and persistence in soil and
groundwater and are expected to form larger plumes than less mobile and
persistent contaminants in the same hydrogeological setting (ITRC,
2018). In addition, long-range atmospheric transport of PFOA and PFOS
through industrial releases (e.g., stack emissions) can accumulate to
measurable levels in soils and surface waters away from their point of
release (Young et al., 2007; Wallington et al., 2006; Dreyer et al.,
2010). Although some manufacturing companies agreed to phase out
production of PFOA and PFOS in the United States, other sources could
still exist such as fire training and emergency response sites,
industrial sites, landfills, and wastewater treatment plant biosolids
as well as imported in products (USEPA, 2017c; ITRC, 2018). Drinking
water analytical methods are available to measure PFOA, PFOS, and other
PFAS in drinking water. The EPA has published validated methodology for
detecting a total of 29 unique PFAS in drinking water including EPA
Method 537.1 (18 PFAS) (USEPA, 2018b) and EPA Method 533 (25 PFAS) (14
PFAS can be detected by both methods). Therefore, new information about
the occurrence of PFAS in drinking water will become available as the
Agency further evaluates regulatory action for these contaminants.
Available treatment technologies for removing PFAS from drinking
water have been evaluated and reported in the literature (e.g.,
Dickenson and Higgins, 2016). The EPA's Drinking Water Treatability
Database (USEPA, 2019e) summarizes available technical literature on
the efficacy of treatment technologies for a range of priority drinking
water contaminants, including PFOA and PFOS. Conventional treatment
(comprised of the unit processes coagulation, flocculation,
clarification, and filtration) is not considered effective for the
removal of PFOA. Granular activated carbon (GAC), anion exchange
resins, reverse osmosis and nanofiltration are considered effective for
the removal of PFOA. However, there are limitations and uncertainties
pertaining to these removal processes for PFAS. For example, the
treatment efficacy of GAC and anion exchange resins is strongly
dependent upon the type of PFAS present and physio-chemical properties
of the solution matrix. When mixed PFAS are in the source water, short-
chain PFAS will break through the adsorber more quickly. When a system
makes treatment technology decisions, it is important to consider the
media reactivation and replacement frequency, the cost of reactivation
or disposal of spent media, and the potential for overshoot (i.e.,
higher concentrations of a contaminant in the effluent than the
influent, due to preferential adsorption of other contaminants) if a
treatment system is operated improperly (Crone et al., 2019; Speth,
2019). Reverse osmosis and nanofiltration are effective for removing a
wide range of PFAS. However, they have high capital and operations
costs (Crone et al., 2019; Speth, 2019). Additionally, membrane
fouling, corrosion control, and the disposal or treatment of
concentrate stream are issues that need to be addressed (Crone et al.,
2019; Speth, 2019). Additional literature and discussion on the
efficacy of these treatments can be found on the EPA's Drinking Water
Treatability Database (USEPA, 2019e).
Considering the population exposed to PFOA and PFOS including
sensitive populations and lifestages, such as children, the potential
adverse human health impacts of these contaminants at low
concentrations, the environmental persistence, the persistence in the
human body, the availability of both methods to measure and treatment
technologies to remove these contaminants, and significant public
concerns regarding PFOA and PFOS contamination, the Agency proposes the
finding that regulation of PFOA and PFOS presents a meaningful
opportunity for health risk reduction for infants, children, and
adults, including pregnant and nursing women, served by PWS. While SDWA
specifies that the determination of whether PFOA and PFOS present ``a
meaningful opportunity for health risk reduction for persons served by
public water systems'' is made ``in the sole judgement of the
Administrator,'' the EPA seeks public comment on the information and
analyses described above.
e. Preliminary Regulatory Determination for PFOA and PFOS
At this stage, the Agency is making a preliminary determination to
regulate PFOA and PFOS with an NPDWR after evaluating health,
occurrence, and other related information against the three SDWA
statutory criteria. The EPA has preliminarily determined that PFOA and
PFOS may have an adverse effect on human health; that PFOA and PFOS
occur in PWSs with a frequency and at levels of public health concern;
and that regulation of PFOA and PFOS presents a meaningful opportunity
for health risk reduction for persons served by PWSs. The Regulatory
Determination 4 Support Document (USEPA, 2019a) and the Occurrence Data
from the Third Unregulated Contaminant Monitoring Rule (UCMR 3) (USEPA,
2019b) present additional information and analyses supporting the
Agency's evaluation of PFOA and PFOS.
The agency solicits comment on all aspects of this preliminary
regulatory determination. In particular, the EPA requests comment on
whether there are any additional data the agency should consider in
making its final regulatory determination and whether EPA has
appropriately considered the data.
f. Considerations for Additional PFAS
As stated in the EPA's PFAS Action Plan (USEPA, 2019d): ``The
Agency recognizes that there is additional information that the EPA
should evaluate regarding PFAS other than PFOA and PFOS, including new
monitoring and occurrence data, recent health effects data, and
additional information to be solicited from the public, which will
inform the development of a national drinking water regulation for a
broader class of PFAS in the future.''
The EPA is aware that many states, tribes, and local communities
face challenges from PFAS other than PFOA and PFOS. For example, in
addition to PFOA and PFOS, the EPA worked with states and public water
systems to characterize the occurrence of four additional PFAS
(perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS),
perfluoroheptanoic acid (PFHpA), and PFBS)) in the nation's drinking
water served by public water systems under UCMR 3. The EPA found that
4.0% of PWSs reported results for which one or more of the six UCMR 3
PFAS were measured at or above their respective MRL. The 4.0% figure is
based on 198 PWSs reporting measurable PFAS results for one or more
sampling events from one or more of their sampling locations. Those 198
PWS serve an estimated total population of approximately 16 million.
With the voluntary phase-out of PFOA and PFOS, manufacturers are
shifting to alternative PFAS compounds (e.g., hexafluoropropylene oxide
(HFPO) dimer acid and HFPO dimer acid ammonium salt (GenX chemicals),
and perfluorobutanesulfonic acid (PFBS)). There is less publicly
available information on the occurrence and health effects of these
replacements than for PFOA and PFOS and other members of the carboxylic
acid and sulfonate PFAS families (Brendel et al., 2018).
The EPA plans to consider available human health toxicity and
occurrence
[[Page 14121]]
information for other PFAS as they become available. The EPA is working
on hazard assessments for the following PFAS: GenX chemicals; PFBS;
PFNA; perfluorobutanoic acid (PFBA); perfluorodecanoic acid (PFDA);
perfluorohexanoic acid (PFHxA); and PFHxS.
The following PFAS have literature available in the EPA's Health
and Environmental Research Online (HERO), which is a database of
scientific studies and other references used to develop the EPA's risk
assessments aimed at understanding the health and environmental effects
of pollutants and chemicals. While HERO uses a variety of reference
types, the majority are original research published in peer-reviewed
literature. For some PFAS, there are epidemiological and/or
experimental animal toxicity data available, which may be suitable to
inform the evaluation of potential human health effects. Other
references provide information on occurrence (both in humans and the
environment). Available references for the PFAS listed below can be
accessed at: https://hero.epa.gov/hero/index.cfm/litbrowser/public/#PFAS.
------------------------------------------------------------------------
Chemical name Acronym CAS No.
------------------------------------------------------------------------
Perfluorooctanoic acid....... PFOA..................... 335-67-1
Perfluorooctanesulfonic acid. PFOS..................... 1763-23-1
2H,2H,3H,3H-Perfluorooctanoic 5:3 acid................. 914637-49-3
acid.
6:2/8:2 Fluorotelomer 6:2/8:2 diPAP............ 943913-15-3
phosphate diester.
Bis[2-(perfluorohexyl)ethyl] 6:2 diPAP................ 57677-95-9
phosphate.
Mono[2-(perfluorohexyl)ethyl] 6:2 monoPAP.............. 57678-01-0
phosphate.
Bis[2-(perfluorooctyl)ethyl] 8:2 diPAP................ 678-41-1
phosphate.
Mono[2-(perfluorooctyl)ethyl] 8:2 monoPAP.............. 57678-03-2
phosphate.
4,8-dioxa-3H- ADONA.................... 919005-14-4
perfluorononanoic acid.
6:2 Fluorotelomer alcohol.... FtOH 6:2................. 647-42-7
8:2 Fluorotelomer alcohol.... FtOH 8:2................. 678-39-7
6:2 Fluorotelomer sulfonic FtS 6:2.................. 27619-97-2
acid.
8:2 Fluorotelomer sulfonic FtS 8:2.................. 39108-34-4
acid.
HFPO dimer acid.............. GenX chemicals........... 13252-13-6
HFPO dimer acid ammonium salt GenX chemicals........... 62037-80-3
2-(N- NEtFOSAA................. 2991-50-6
Ethylperfluorooctanesulfonam
ido) acetic acid.
2-(N- NMeFOSAA................. 2355-31-9
Methylperfluorooctanesulfona
mido) acetic acid.
Perfluorobutanoic acid....... PFBA..................... 375-22-4
Perfluorobutanesulfonic acid. PFBS..................... 375-73-5
Perfluorodecanoic acid....... PFDA..................... 335-76-2
Perfluorododecanoic acid..... PFDoA.................... 307-55-1
Perfluorodecanesulfonic acid. PFDS..................... 335-77-3
Perfluoroheptanoic acid...... PFHpA.................... 375-85-9
Perfluoroheptanesulfonic acid PFHpS.................... 375-92-8
Perfluorohexanoic acid....... PFHxA.................... 307-24-4
Perfluorohexanesulfonic acid. PFHxS.................... 355-46-4
Perfluorononanoic acid....... PFNA..................... 375-95-1
Perfluorononanesulfonic acid. PFNS..................... 68259-12-1
Perfluorooctanesulfonamide... PFOSA.................... 754-91-6
Perfluoropentanoic acid...... PFPeA.................... 2706-90-3
Perfluoropentanesulfonic acid PFPeS.................... 2706-91-4
Perfluorotetradecanoic acid.. PFTeDA................... 376-06-7
Perfluoroundecanoic acid..... PFUnA.................... 2058-94-8
------------------------------------------------------------------------
The EPA continues to work towards filling information gaps for
human health, toxicity and occurrence including through collaborations
with federal, state, tribal, and other stakeholders. The EPA is
generating PFAS toxicology data through new approaches such as high
throughput screening, computational toxicology tools, and chemical
informatics for chemical prioritization, screening, and risk
assessment. This research can inform a more complete understanding of
PFAS toxicity for the large set of PFAS chemicals without conventional
toxicity data and allow prioritization of actions to potentially
address groups of PFAS. For additional information on the new approach
methods for PFAS toxicity testing, please visit: https://www.epa.gov/chemical-research/pfas-chemical-lists-and-tiered-testing-methods-descriptions. To further understand occurrence in drinking water and
discussed in the EPA's PFAS Action Plan (USEPA, 2019d), the EPA will
propose a nationwide drinking water monitoring for PFAS under the next
UCMR monitoring cycle (UCMR 5) utilizing newer methods available to
detect more PFAS chemicals and at lower MRLs than previous possible for
the earlier UCMR monitoring. These monitoring results will improve
understanding of the frequency and concentration of PFAS occurrence in
the finished U.S. drinking water.
The EPA is also aware of ongoing toxicity work and guideline
development by other federal agencies, state governments, international
organizations, industry groups, and other stakeholders. For example,
the U.S. National Toxicology Program is conducting ongoing
toxicological studies for multiple PFAS compounds of varying length in
rats, including 28-day studies for 7 PFAS compounds (3 carboxylates and
4 sulfonates), and a 2-year chronic toxicity and carcinogenicity study
for PFOA that is currently undergoing peer-review. ATSDR developed a
draft toxicological profile that characterizes toxicologic and adverse
health effects information for PFOA, PFOS, and 10 other PFAS compounds
which include PFBA, PFHxA, PFHpA, PFNA, PFDA, PFUnA, PFDoA, PFBS,
PFHxS, and PFOSA (ATSDR, 2018). Some states, including California,
Michigan, Minnesota, New Hampshire, New Jersey, New York and Vermont,
are also developing health-based guidance or drinking water standards
for individual targeted PFAS or the sum for several targeted PFAS
[[Page 14122]]
(California OEHHA, 2019; Commonwealth of Massachusetts, 2019; MDH,
2019; Michigan Science Advisory Workgroup, 2019; NHDES, 2019; NJDOH,
2017; NYSDOH, 2018; VTDEC, 2019). PFAS that have been or are being
evaluated by at least one state include Hexafluoropropylene Oxide
(HFPO) Dimer Acid and its Ammonium Salt (GenX chemicals), PFBA, PFBS,
PFHpA, PFHxA, PFHxS, PFNA, PFOA, and PFOS. The EPA will evaluate all
available and reliable information to inform future decision making for
these PFAS contaminants. The EPA is also aware of PFAS monitoring
efforts by states and local communities to better understand PFAS
occurrence in drinking water, including both statewide drinking water
monitoring efforts and targeted sampling at locations that have
potentially been impacted by releases or locations where PFAS-
containing materials are known to have been used (Table 9). The EPA
will consider these other information sources to inform future
decisions for other PFAS.
g. Potential Regulatory Approaches
Since PFOA and PFOS raise complicated issues and since the issuance
of any NPDWR imposes costs on the public, the EPA is taking advantage
of this document by exploring and seeking comment on potential
regulatory constructs and monitoring requirements the Agency may
consider for PFAS chemicals including PFOA and PFOS if it were to
finalize positive regulatory determinations. As noted above in the EPA
PFAS Action Plan (USEPA, 2019d), the EPA is seeking information from
the public to ``inform the development of national drinking water
regulation for a broader class of PFAS in the future''. The EPA is
seeking feedback on potential regulatory approaches to address PFAS to
support the potential development of a PFOA and PFOS regulation
(pending final regulatory determinations) or in future PFAS regulatory
actions. The EPA is exploring how to best use the available information
when developing potential regulatory approaches for PFAS. Three
potential regulatory approach options described below include (1)
evaluate each additional PFAS on an individual basis; (2) evaluate
additional PFAS by different grouping approaches; and (3) evaluate PFAS
based on drinking water treatment techniques.
Evaluate Each Additional PFAS on an Individual Basis
This approach would focus on evaluating PFAS individually for
potential future regulatory actions using information completed prior
to a potential rule proposal. Examples of suitable information sources
the EPA could evaluate under future actions include current and
expected peer reviewed toxicity assessments, nationwide drinking water
monitoring data, state drinking water monitoring data, and monitoring
data from other Federal Agencies. This approach would be limited to
those individual PFAS for which sufficient health and occurrence
information is available or can be clearly and logically extrapolated.
The EPA is actively working to fill information gaps needed to support
this approach including developing toxicity assessments for PFBS, HFPO
dimer acid and HFPO dimer acid ammonium salt or GenX chemicals, PFBA,
PFHxA, PFNA, and PFHxS, and PFDA. The EPA plans to propose nationwide
drinking water monitoring for PFAS under the next UCMR monitoring cycle
(UCMR 5) utilizing newer methods available to measure more PFAS and at
lower minimum reporting levels than previous UCMR monitoring. The EPA
may also consider health assessments and occurrence data that are
currently being developed by other federal, state and international
agencies.
Evaluate Additional PFAS by Different Grouping Approaches
Since the 1940s, over 4000 PFAS have been manufactured and used in
a variety of industries across the world (Guelfo et al., 2018; OECD
2019). Evaluations of the retrospective reporting requirements of the
TSCA Inventory Notification Rule indicates 602 PFAS are currently
commercially active in the United States. The EPA recognizes the
challenges associated with evaluating each PFAS that may impact
drinking water on an individual basis. The EPA has regulated
contaminants as a group in drinking water, including, for example,
disinfection byproducts (i.e., haloacetic acids and total
trihalomethanes).
In their study of organohalogen flame retardants, the National
Academies of Sciences evaluated general approaches to forming chemical
classes at regulatory agencies and concluded that a ``science-based
class approach does not necessarily require one to evaluate a large
chemical group as a single entity for hazard assessment. That is, an
approach that divides a large group into smaller units (or subclasses)
to conduct the hazard assessment is still a class approach for purposes
of hazard or risk assessment'' (NASEM, 2019). An approach to exploring
PFAS by groups could, for example, include evaluating groups of PFAS to
account for similar physiochemical characteristics. The EPA's ORD and
the National Institute of Environmental Health Sciences' (NIEHS)
National Toxicology Program recently identified a subset of PFAS for
testing with the goals of supporting read-across within structure-based
subgroups and capturing the diversity of the broader PFAS class (Helman
et al., 2019; Patlewicz et al., 2019a, 2019b). The EPA is also
exploring new approaches such as high throughput and computational
approaches to explore different chemical categories of PFAS. The EPA
will continue research on methods for using these data to support risk
assessments using new approach methods such as read-across (i.e., an
effort to predict biological activity based on similarity in chemical
structure) and transcriptomics (i.e., a measure of changes in gene
expression in response to chemical exposure or other external
stressors), and to make inferences about the toxicity of PFAS mixtures
that commonly occur in real world exposures. Example classifications
that the EPA could consider in its group evaluation include common
adverse effects, chain length (e.g., long chain and short chain),
functional groups (e.g., sulfonates, acids), degradation products
(i.e., some PFAS degrade to shorter chain PFAS), co-occurrence, or
using a combination of physiochemical and fate characteristics (e.g.,
long chain perfluoroalkyl sulfonic acids).
Evaluate PFAS Based on Drinking Water Treatment Techniques
SDWA 1412(b)(7)(A) authorizes the EPA to promulgate a treatment
technique rule rather than an MCL if the Agency determines it is not
economically or technologically feasible to ascertain the level of the
contaminant. The EPA continues to develop reliable analytical methods
to monitor for PFAS including evaluating methodologies to measure total
PFAS. However, the EPA does not anticipate that reliable and validated
methods that accurately and precisely capture all PFAS or total PFAS
(and not other fluorinated, non-PFAS compounds) will be available for a
number of years. Therefore, the Agency is considering whether a
treatment technique regulatory approach may be appropriate.
The strength of the carbon-fluorine bond makes certain PFAS (such
as perfluoroalkyl acids) relatively stable compounds that are not
removed by conventional treatment such as coagulation/flocculation/
sedimentation. Technologies that have reported removal efficiencies of
greater than 90% for certain PFAS include granulated
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activated carbon, powdered activated carbon, anion exchange resins,
nanofiltration and reverse osmosis (Crone et al., 2019; Dickenson and
Higgins, 2016; Ross et al., 2018; USEPA, 2019e). Each of these
technologies has benefits and limitations that need to be considered if
they are to be used when treating PFAS contaminated drinking water,
such as cost and operational feasibility (Speth, 2019). For example,
nanofiltration and reverse osmosis are highly effective at removing
PFAS but are more costly options and generate large waste streams that
may require additional treatment. Anion exchange is effective at
removing long-chain PFAS constituents but may be less effective at
removing short-chain PFAS. Granular activated carbon has the advantage
of being a less costly treatment technology and has the ability to be
regenerated, however other organic matter present in the influent water
may interact and compete for adsorption sites with PFAS, potentially
making treatment less effective. In addition, unintended consequences
of PFAS treatment also need consideration given regional differences in
source water quality and treatment strategies in the United States.
Additional discussion on benefits and limitations associated with
drinking water treatment technologies for PFAS can be found in the
Regulatory Determination Support Document (USEPA, 2019a).
A treatment technique regulation would address multiple PFAS with
similar characteristics that may be removed by similar treatment
technologies including some for which validated drinking water methods
are currently available.
Monitoring Considerations
Should an MCL be established for PFOA, PFOS, and/or other PFAS
chemicals pursuant to section 1412 of the SDWA, PWSs could be required
to monitor for these contaminants. The EPA may seek to minimize the
monitoring burden on water systems while assuring public health
protection. Minimizing the monitoring burden to the maximum extent
feasible and allowed by statute could reduce costs for drinking water
systems that have other important risk-reduction resource demands. The
EPA is considering alternative approaches for this monitoring that
reduce monitoring frequency for systems that are reliably and
consistently below the MCL or do not detect the contaminant. This
framework provides primacy agencies with the flexibility to issue
monitoring waivers, with the EPA's approval, which take into account
regional and state specific characteristics and concerns. The
Standardized Monitoring Framework for regulated synthetic organic
chemicals under 40 CFR 141.24(h) provides a framework for determining
compliance with a potential future MCL. Under this approach, monitoring
frequency would be dependent on whether the contaminant has been
detected above a certain ``trigger level'' and/or detected above an
MCL, and whether a waiver from monitoring has been granted by the
Primacy Agency.
An alternative approach to the Standardized Monitoring Framework
could be to require monitoring at public water systems only when data
show the presence of PFAS in finished drinking water and those
designated by the Primacy Agency. Under this approach, monitoring would
be required for public water systems with PFAS monitoring data and/or
vulnerable systems designated by the state or Primacy Agency. For
example, monitoring could be required if a Primacy Agency is aware of
information indicating potential PFAS contamination of the public water
supply. Information that could be considered includes proximity to
facilities with historical or on-going use of fire-fighting foam and
proximity to facilities that use or manufacture PFAS.
2. 1,1-Dichloroethane
a. Background
1,1-Dichloroethane is a halogenated alkane. It is an industrial
chemical and is used as a solvent and a chemical intermediate. Annual
production and importation of 1,1-dichloroethane in the United States
was last reported by IUR in 2006 to be between 500,000 and 1 million
pounds. The data show that production of 1,1-dichloroethane in the
United States has declined since reporting began in 1986. Under CDR,
there were no reports of 1,1-dichloroethane production in 2012, 2013,
2014, or 2015 (USEPA, 2019a).
TRI data for 1,1-dichloroethane from the years 1994-2016 show that
an average of about 12,000 pounds per year of reported releases have
entered the environment from 2003 onward. The number of states with
releases of 1,1 dichloroethane has stayed steady at about five since
2004, while the number of states with surface water discharges has
averaged two since 1994; surface water discharges ranged from 0 to 235
pounds per year over the approximately 20-year period (USEPA, 2019a).
1,1-Dichloroethane is expected to have a high likelihood of
partitioning to water based on its Koc and water solubility.
The octanol-water partitioning coefficient (log Kow)
indicates that 1,1-dichloroethane is expected to have a moderate
likelihood of partitioning to water, while the Henry's Law Constant
(KH) indicates that this compound is expected to have a low
likelihood of partitioning to water. 1,1-Dichloroethane is expected to
have moderate to high persistence in certain waters based on
biodegradation half-lives (USEPA, 2019a).
b. Statutory Criterion #1 (Adverse Health Effects)
1,1-Dichloroethane may have an adverse effect on the health of
persons. Based on a 13-week gavage study in rats (Muralidhara et al.,
2001), the kidney was identified as a sensitive target for 1,1-
dichloroethane, and no-observed-adverse-effect level (NOAEL) and
lowest-observed-adverse-effect level (LOAEL) values of 1,000 and 2,000
mg/kg/day, respectively, were identified based on increased urinary
enzyme markers for renal damage and central nervous system (CNS)
depression (USEPA, 2006a).
The only available reproductive or developmental study with 1,1-
dichloroethane is an inhalation study where pregnant rats were exposed
on days 6 through 15 of gestation (Schwetz et al., 1974). No effects on
the fetuses were noted at 3,800 ppm. Delayed ossification of the
sternum without accompanying malformations was reported at a
concentration of 6,000 ppm.
A cancer assessment for 1,1-dichloroethane is available on IRIS
(USEPA, 1990a). That assessment classifies the chemical, according to
the EPA's 1986 Guidelines for Carcinogenic Risk Assessment (USEPA,
1986), as Group C, a possible human carcinogen. This classification is
based on no human data and limited evidence of carcinogenicity in two
animal species (rats and mice), as shown by increased incidences of
hemangiosarcomas and mammary gland adenocarcinomas in female rats and
hepatocellular carcinomas and benign uterine polyps in mice (NCI,
1978). The data were considered inadequate to support quantitative
assessment. The close structural relationship between 1,1-
dichloroethane and 1,2-dichloroethane, which is classified as a B2
probable human carcinogen and produces tumors at many of the same sites
where marginal tumor increases were observed for 1,1-dichloroethane,
supports the suggestion that the 1,1-isomer could possibly be
carcinogenic to humans. Mixed results in initiation/promotion studies
and genotoxicity assays are
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consistent with this classification. On the other hand, the animals
from the 1,1-dichloroethane National Cancer Institute (NCI, 1978) study
were housed with animals being exposed to 1,2-dichloroethane providing
opportunities for possible co-exposure impacting the 1,1-dichloroethane
results. The following groups of individuals may have an increased risk
from exposure to 1,1-dichloroethane (NIOSH, 1978; ATSDR, 2015):
Those with chronic respiratory disease
Those with liver diseases that impact hepatic microsomal
cytochrome P-450 functions
Individuals with impaired renal function and vulnerable to
kidney stones
Individuals with skin disorders vulnerable to irritation by
solvents like 1,1- dichloroethane
Those who consume alcohol or use pharmaceuticals (e.g.,
phenobarbital) that alter the activity of cytochrome P-450s
A provisional chronic RfD was derived from the 13-week gavage study
in rats based on a NOAEL of 1,000 mg/kg/day administered for five days/
week and adjusted to 714.3 mg/kg/day for continuous exposure (an
increase in urinary enzymes was the adverse impact on the kidney). The
chronic oral RfD of 0.2 mg/kg/day was derived by dividing the
normalized NOAEL of 714.3 mg/kg/day in male Sprague-Dawley rats by a
combined UF of 3,000. The combined UF includes factors of 10 for
interspecies extrapolation, 10 for extrapolation from a subchronic
study, 10 for human variability, and 3 for database deficiencies
(including lack of reproductive and developmental toxicity tests by the
oral route). This assessment noted several limitations in the critical
study and database as a whole. Specifically, that the reporting of the
results in the critical study were marginally adequate and that the
database lacks information on reproductive and developmental and
nervous system toxicity.
The EPA calculated an HRL for 1,1-dichloroethane of 1,000 [micro]g/
L, based on the EPA oral RfD of 0.2 mg/kg/day, using 2.5 L/day drinking
water ingestion, 80 kg body weight and a 20% RSC factor.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public
Health Concern)
The EPA proposes to find that 1,1-dichloroethane does not occur
with a frequency and at levels of public health concern in public water
systems based on the EPA's evaluation of the following occurrence
information.
The primary occurrence data for 1,1-dichloroethane are recent
(2013-2015) nationally-representative drinking water monitoring data
generated through the EPA's UCMR 3. Under UCMR 3, 36,848 samples were
collected from 4,916 PWSs and analyzed for 1,1-dichloroethane. The
contaminant was not detected in any of the samples at levels greater
than \1/2\ the HRL (500 [micro]g/L) or the HRL (1,000 [micro]g/L). 1,1-
Dichloroethane was detected in about 2.3% samples at or above the MRL
(0.03 [micro]g/L) (USEPA, 2019a; USEPA, 2019b).
Occurrence data for 1,1-dichloroethane in finished drinking water
are also available from UCM Rounds 1 and 2 (1988-1992 and 1993-1997).
None of those samples exceeded \1/2\ the HRL or the HRL. In the Round 1
cross-section states, 1,1 dichloroethane was detected at 233 PWSs
(1.14% of PWSs). Detected concentrations ranged from 0.01 [micro]g/L to
500 [micro]g/L. In the Round 2 cross-section states, 1,1 dichloroethane
was detected at 184 PWSs (0.74% of PWSs). Detected concentrations
ranged from 0.00126 [micro]g/L to 159 [micro]g/L (USEPA, 2008c; USEPA,
2019a).
Occurrence data for 1,1-dichloroethane in ambient water are
available from the NAWQA program. Those data show that 1,1-
dichloroethane was detected in between 2% and 4% of samples from
between 2% and 4% of sites. No detections were greater than the HRL.
The median concentrations based on detections were less than 0.06
[micro]g/L (WQP, 2018). Ambient water data for 1,1-dichloroethane
analysis are also available from the NWIS database. Those data show
that 1,1-dichloroethane was detected in approximately 5% of samples
(1,152 out of 24,560) and at approximately 5% of sites (620 out of
12,057). The median concentration of detections was 0.380 [micro]g/L
(USEPA, 2019a).
d. Statutory Criterion #3 (Meaningful Opportunity)
1,1-Dichloroethane does not present a meaningful opportunity for
health risk reduction through regulation for persons served by PWSs
based on the estimated exposed population, including sensitive
populations. UCMR 3 findings indicate that the estimated population
exposed to 1,1-dichloroethane at levels of public health concern is 0%.
As a result, the Agency finds that an NPDWR for 1,1-dichloroethane does
not present a meaningful opportunity for health risk reduction.
e. Preliminary Regulatory Determination for 1,1-dichloroethane
The Agency is making a preliminary determination to not regulate
1,1-dichloroethane with an NPDWR after evaluating health, occurrence,
and other related information against the three SDWA statutory
criteria. While data suggest that 1,1-dichloroethane may have an
adverse effect on human health, the occurrence data indicate that 1,1-
dichloroethane is not occurring or is 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 1,1-dichloroethane would not
present a meaningful opportunity to reduce health risk for persons
served by PWSs. The Regulatory Determination 4 Support Document (USEPA,
2019a) and the Occurrence Data from the Third Unregulated Contaminant
Monitoring Rule (UCMR 3) (USEPA, 2019b) present additional information
and analyses supporting the Agency's evaluation of 1,1-dichloroethane.
3. Acetochlor
a. Background
Acetochlor is a chloroacetanilide pesticide that is used as an
herbicide for pre-emergence control of weeds. It was first registered
by the EPA in 1994. It is registered for use on corn crops (field corn
and popcorn); corn fields treated with acetochlor may later be rotated
to grain sorghum (milo), soybeans, wheat, and tobacco. In March of
2006, the EPA released a Report of the Food Quality Protection Act
(FQPA) Tolerance Reassessment Progress and Risk Management Decision
(TRED) for Acetochlor (USEPA, 2006b). In 2010, the EPA approved the use
of acetochlor on cotton as a rotational crop (USEPA, 2010a). Synonyms
for acetochlor include 2-chloro-2'-methyl-6-ethyl-N-
ethoxymethylacetanilide (USEPA, 2019a).
According to the EPA Pesticide Industry Sales and Usage reports,
the amount of acetochlor active ingredient used in the United States
was between 31 and 36 million pounds in 1997; between 30 and 35 million
pounds in 1999, 2001 and 2003; between 26 and 31 million pounds in
2005; between 28 and 33 million pounds in 2007; between 23 and 33
million pounds in 2009; and between 28 and 38 million pounds in 2012
(USEPA, 2019a).
USGS pesticide use data show that there has been an increase in the
annual usage of acetochlor, from about 32 million pounds per year in
2010 to over 45 million pounds in 2016. This increase can largely be
attributed to the
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use of acetochlor on crops other than corn (USEPA, 2019a).
If released to soil, acetochlor is expected to have moderate to
high mobility (HSDB, 2012). Acetochlor is expected to have a high
likelihood of partitioning to water based on its KH. The
values for Koc indicate that acetochlor is expected to have
a moderate to high likelihood of partitioning to water. The water
solubility indicates that acetochlor is expected to have a moderate
likelihood of partitioning to water. Acetochlor is expected to have low
to moderate persistence based on aerobic and anaerobic biodegradation/
biotransformation half-lives (USEPA, 2019a).
b. Statutory Criterion #1 (Adverse Health Effects)
Acetochlor may have an adverse effect on the health of persons.
Subchronic and chronic oral studies have demonstrated adverse effects
on the liver, thyroid (secondary to the liver effects), nervous system,
kidney, lung, testes, and erythrocytes in rats and mice (USEPA, 2006c;
USEPA, 2018c). There was evidence of carcinogenicity in studies
conducted with acetochlor in rats and mice and a non-mutagenic mode of
action was demonstrated for nasal and thyroid tumors in rats (USEPA,
2006c). Cancer effects include nasal tumors and thyroid tumors in rats,
lung tumors and histocytic sarcomas in mice, and liver tumors in both
rats and mice (Ahmed and Seely, 1983; Ahmed et al., 1983; Amyes, 1989;
Hardisty, 1997a; Hardisty, 1997b; Hardisty, 1997c; Naylor and Ribelin,
1986; Ribelin, 1987; USEPA, 2004b; USEPA, 2006c; and Virgo and
Broadmeadow, 1988). No biologically sensitive human subpopulations have
been identified for acetochlor. Developmental and reproductive toxicity
studies do not indicate increased susceptibility to acetochlor exposure
at early life stages in test animals (USEPA, 2006c).
The study used to derive the oral RfD is a 1-year oral chronic
feeding study conducted in beagle dogs. This study describes a NOAEL of
2 mg/kg/day, and a LOAEL of 10 mg/kg/day, based on the critical effects
of increased salivation; increased levels of alanine aminotransferase
(ALT) and ornithine carbamoyl transferase (OTC); increased triglyceride
levels; decreased blood glucose levels; and alterations in the
histopathology of the testes, kidneys, and liver of male beagle dogs
(USEPA, 2018c; ICI, Inc., 1988). The UF applied was 100 (10 for
intraspecies variation and 10 for interspecies extrapolation). The EPA
OPP RfD for acetochlor of 0.02 mg/kg/day, based on the NOAEL of 2 mg/
kg/day from the 1-year oral chronic feeding study in beagle dogs, is
expected to be protective of both noncancer and cancer effects.
The EPA calculated an HRL of 100 [micro]g/L based on the EPA OPP
RfD for non-cancer effects for acetochlor of 0.02 mg/kg/day (USEPA,
2018c) using 2.5 L/day drinking water ingestion, 80 kg body weight, and
a 20% RSC factor.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public
Health Concern)
The EPA proposes to find that acetochlor does not occur with a
frequency and at levels of public health concern in public water
systems based on the EPA's evaluation of the following occurrence
information.
The primary data for acetochlor are from the UCMR 1 a.m. (2001-
2003) and UCMR 2 SS (2008-2010). Acetochlor was not detected at or
above the MRL of 2 [micro]g/L or above the HRL of 100 [micro]g/L in any
of the 33,778 UCMR 1 a.m. samples (USEPA, 2008b; USEPA, 2019a) or in
any of the 11,193 UCMR 2 SS samples (USEPA, 2015a; USEPA, 2019a).
To ascertain the impact of increased usage of acetochlor since the
end of UCMR 2, the EPA assessed ambient water and limited finished
water data collected after 2010. Sources of such data include the NAWQA
program and the NWIS database. Three cycles of NAWQA data show that
acetochlor was detected in between 13% and 23% of samples from between
3% and 10% of sites. While maximum values in NAWQA Cycle 2 (2002-2012)
and Cycle 3 (2013-2017) monitoring exceeded the HRL (215 [micro]g/L in
2004 and 137 [micro]g/L in 2013) (only one sample in each of those two
cycles exceeded the HRL), 90th percentile levels of acetochlor remained
below 1 [micro]g/L. More than 10,000 samples were collected in each
cycle. Non-NAWQA NWIS data (1991-2016), which included limited finished
water data in addition to the ambient water data, show no detected
concentrations greater than the HRL (USEPA, 2019a).
d. Statutory Criterion #3 (Meaningful Opportunity)
Acetochlor 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 acetochlor at levels of public health concern is
0% based on UCMR 1 finished water data gathered from 2001 to 2003 and
UCMR 2 finished water data gathered from 2008 to 2010. As a result, the
Agency finds that an NPDWR for acetochlor does not present a meaningful
opportunity for health risk reduction.
e. Preliminary Regulatory Determination for Acetochlor
The Agency is making a preliminary determination to not regulate
acetochlor with an NPDWR after evaluating health, occurrence, and other
related information against the three SDWA statutory criteria. While
data suggest that acetochlor may have an adverse effect on human
health, the occurrence data indicate that acetochlor is not occurring
or not likely to occur in PWSs with a frequency and at levels of public
health concern. The EPA also noted that the use of acetochlor has
increased since the nationally representative data collection from
finished water under UCMR 2 (i.e., 2008-2010). A review of ambient and
limited finished water monitoring data collected since 2010 in NAWQA
and NWIS show no 90th percentile values exceeding 1 [micro]g/L.
Therefore, the Agency has determined that an NPDWR for acetochlor
would not present a meaningful opportunity to reduce health risk for
persons served by PWSs. The Regulatory Determination 4 Support Document
(USEPA, 2019a), The Analysis of Occurrence Data from the First
Unregulated Contaminant Monitoring Regulation (UCMR 1) in Support of
Regulatory Determinations for the Second Drinking Water Contaminant
Candidate List (USEPA, 2008b), and the Occurrence Data from the Second
Unregulated Contaminant Monitoring Regulation (UCMR 2) (USEPA, 2015a)
present additional information and analyses supporting the Agency's
evaluation of acetochlor.
4. Methyl Bromide (Bromomethane)
a. Background
Methyl bromide is a halogenated alkane and occurs as a gas. Methyl
bromide has been used as a fumigant fungicide, applied to soil before
planting, to crops after harvest, to vehicles and buildings, and for
other specialized purposes.
Methyl bromide is an ozone-depleting chemical regulated under the
Montreal Protocol. Use of the chemical in the United States was phased
out in 2005, except for specific critical use exemptions and quarantine
and pre-shipment exemptions. Critical use exemptions have included
strawberry cultivation and production of dry cured pork. Additional
information on the methyl bromide phase-out and exemptions in the
United States can be found on the EPA's website: https://
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www.epa.gov/ods-phaseout/methyl-bromide.
In August of 2006, the EPA released a TRED for methyl bromide and a
RED for commodity uses (USEPA, 2006d). A RED for soil fumigant uses was
released in July 2008, and amended in May 2009 (USEPA, 2009e). In 2011,
the EPA issued a cancellation order for certain soil-related uses of
methyl bromide, but this order did not affect its use as a post-harvest
fumigant (76 FR 29238; USEPA, 2011d). Synonyms for methyl bromide
include bromomethane, monobromomethane, curafume, Meth-O-Gas, and Brom-
O-Sol (HSDB, 2019).
A report by the United Nations Environment Programme (UNEP, 2018)
indicates that critical use exemptions in the United States under the
Montreal Protocol declined steadily from 9,553 metric tons of methyl
bromide in 2005 to 235 metric tons in 2016 and stood at 0 in 2017 and
2018. A total 50 metric tons were ``on hand'' in the United States at
the end of 2016 (UNEP, 2018). Exempted quarantine and pre-shipment uses
continue. Production data for methyl bromide are available from the
EPA's IUR and CDR programs, and industrial release data are available
from the EPA's TRI database, as described below.
The most recent quantities of methyl bromide produced and imported
(in 2013, 2014, and 2015, as reported in CDR) are classified as CBI.
The last publicly available data for production of methyl bromide are
from 2006, under IUR, when production was in the range of 10 to <50
million pounds (USEPA, 2019a).
TRI data from 1988 to 2016 show a general long-term declining trend
in industrial releases of methyl bromide, from over one million pounds
per year in the 1990s to under 500,000 pounds most years since 2010.
Air emissions have tended to dominate releases, with the exception of
2015, when an anomalous large quantity (350,000 pounds) was reported
released by underground injection from a single facility. In 2016,
facilities in 11 states reported releases of any kind and facilities in
two states reported on-site surface water discharges (USEPA, 2019a).
According to the EPA's Pesticide Industry Sales and Usage reports,
the amount of methyl bromide active ingredient used in the United
States was between 38 and 45 million pounds in 1997; between 28 and 33
million pounds in 1999; between 20 and 25 million pounds in 2001;
between 13 and 17 million pounds in 2003; between 12 and 16 million
pounds in 2005; between 11 and 15 million pounds in 2007; between 5 and
9 million pounds in 2009; and between 2 and 6 million pounds in 2012
(USEPA, 2019a).
USGS pesticide use data show that there has been a decrease of
methyl bromide use through 2016 down to about 2 million pounds from a
high of about 78 million pounds in 1995 (USGS, 2018).
If released to dry or moist soil, methyl bromide is expected to be
volatile (HSDB, 2019); its KH indicates that methyl bromide
is expected to have a low likelihood of partitioning to water from air.
Methyl bromide is expected to have a high likelihood of partitioning to
water based on its Koc and water solubility. The log
Kow indicates that methyl bromide is expected to have a
moderate likelihood of partitioning to water. Methyl bromide is
predicted to have low persistence in soil based on experiments under
simulated conditions in reaction with aniline. Measured hydrolysis
half-lives indicate moderate persistence in water (USEPA, 2019a).
b. Statutory Criterion #1 (Adverse Health Effects)
Methyl bromide may have an adverse effect on the health of persons.
The limited number of studies investigating the oral toxicity of methyl
bromide indicate that the route of administration influences the toxic
effects observed (USEPA, 2006e). The forestomach of rats (forestomachs
are not present in humans) appears to be the most sensitive target of
methyl bromide when it is administered orally by gavage (ATSDR, 1992a).
Acute and subchronic oral gavage studies in rats identified stomach
lesions (Kaneda et al., 1998), hyperemia (excess blood) (Danse et al.,
1984), and ulceration (Boorman et al., 1986; Danse et al., 1984) of the
forestomach. However, forestomach effects were not observed in rats and
stomach effects were not observed in dogs that were chronically exposed
to methyl bromide in the diet, potentially because methyl bromide
degrades to other bromide compounds in the food (Mertens, 1997).
Decreases in food consumption, body weight, and body weight gain were
noted in the chronic rat study when methyl bromide was administered in
capsules (Mertens, 1997).
In a subchronic (13-week) rat study (Danse et al., 1984), a NOAEL
of 1.4 mg/kg/day (a time weighted average, \5/7\ days, of the 2 mg/kg/
day dose group) was selected in the EPA IRIS assessment based on severe
hyperplasia of the stratified squamous epithelium in the forestomach,
in the next highest dose group of 7.1 mg/kg/day (USEPA, 1989a). In
ATSDR's Toxicological Profile (ATSDR, 1992a), a lower dose of 0.4 mg/
kg/day is selected as the NOAEL because ``mild focal hyperemia'' was
observed at the 1.4 mg/kg/day dose level. It is worth noting that
authors of this study reported neoplastic changes in the forestomach.
However, the EPA and others (USEPA, 1985; Schatzow, 1984) re-evaluated
the histological results, concluding that the lesions were hyperplasia
and inflammation, not neoplasms. ATSDR notes that histological
diagnosis of epithelial carcinomas in the presence of marked
hyperplasia is difficult (Wester and Kroes 1988; ATSDR 1992a).
Additionally, the hyperplasia of the forestomach observed after 13
weeks of exposure to bromomethane regressed when exposure ended
(Boorman et al. 1986; ATSDR 1992a).
The EPA selected an OPP Human Health Risk Assessment from 2006 as
the basis for developing the HRL for methyl bromide (USEPA, 2006e). As
described in the OPP document, the study was of chronic duration (two
years) with four groups of male rats and four groups of female rats
treated orally via encapsulated methyl bromide. In the OPP assessment
(USEPA, 2006e), Mertens (1997) was identified as the critical study and
decreased body weight, decreased rate of body weight gain, and
decreased food consumption were the critical effects in rats orally
exposed to methyl bromide (USEPA, 2006e). The NOAEL was 2.2 mg/kg/day
and the LOAEL was 11.1 mg/kg/day. The RfD derived in the 2006 OPP Human
Health Assessment is 0.022 mg/kg/day, based on the point of departure
(POD) of 2.2 mg/kg/day (the NOAEL) and a combined uncertainty factor
(UF) of 100 for interspecies variability (10) and intraspecies
variability (10). No benchmark dose modeling was performed.
Neurological effects reported after inhalation exposures have not
been reported after oral exposures, indicating that route of exposure
may influence the most sensitive adverse health endpoint (USEPA, 1988).
Limited data are available regarding the developmental or
reproductive toxicity of methyl bromide, especially via the oral route
of exposure. ATSDR (1992a) found no information on developmental
effects in humans with methyl bromide exposure. An oral developmental
toxicity study of methyl bromide in rats (doses of 3, 10, or 30 mg/kg/
day) and rabbits (doses of 1, 3, or 10 mg/kg/day) found that there were
no treatment-related adverse effects in fetuses of the treated groups
of either species (Kaneda et al., 1998). ATSDR's 1992 Toxicological
Profile also did not
[[Page 14127]]
identify any LOAELs for rats or rabbits in this study. In rats exposed
to 30 mg/kg/day, there was an increase in fetuses having 25 presacral
vertebrae; however, ATSDR notes that there were no significant
differences in the number of litters with this variation and the effect
was not exposure-related (ATSDR, 1992a). No significant alterations in
resorptions or fetal deaths, number of live fetuses, sex ratio, or
fetal body weights were observed in rats and no alterations in the
occurrence of external, visceral, or skeletal malformations or
variations were observed in the rabbits. Some inhalation studies
reported no effects on development or reproduction, but other
inhalation studies show adverse developmental effects. For example,
Hardin et al. (1981) and Sikov et al. (1980) conducted studies in rats
and rabbits and found no developmental effects, even when maternal
toxicity was severe (ATSDR, 1992a). However, another inhalation study
of rabbits found increased incidence of gallbladder agenesis, fused
vertebrae, and decreased fetal body weights in offspring (Breslin et
al., 1990). Decreased pup weights were noted in a multigeneration study
in rats exposed to 30 ppm (Enloe et al., 1986). Reproductive effects
were noted in intermediate-duration inhalation studies in rats and mice
(Eustis et al., 1988; Kato et al., 1986), which indicated that the
testes may undergo degeneration and atrophy at high exposure levels.
In the OPP HHRA for methyl bromide (USEPA, 2006e), methyl bromide
is classified as ``not likely to be carcinogenic to humans''. In 2007,
the EPA published a PPRTV report which stated that there is
``inadequate information to assess the carcinogenic potential'' of
methyl bromide in humans (USEPA, 2007b). The PPRTV assessment agrees
with earlier National Toxicology Program (NTP) conclusions that the
available data indicate that methyl bromide can cause genotoxic and/or
mutagenic changes. The PPRTV assessment states that the results in
studies by Vogel and Nivard (1994) and Gansewendt et al. (1991) clearly
indicate methyl bromide is distributed throughout the body and is
capable of methylating DNA in vivo. However, the PPRTV assessment also
summarizes the results of several studies in mice and rats that have
not demonstrated evidence of methyl bromide-induced carcinogenic
changes (USEPA, 2007b; NTP, 1992; Reuzel et al. 1987; ATSDR, 1992a). In
2012, an epidemiology study was published that concluded there was a
significant monotonic exposure-dependent increase in stomach cancer
risk among 7,814 applicators of methyl bromide (Barry et al., 2012). In
OPP's Draft HHRA for Methyl Bromide, OPP reviews all the
epidemiological studies for methyl bromide, including the Barry et al.
(2012) Agricultural Health Study. OPP concludes that ``based on the
review of these studies, there is insufficient evidence to suggest a
clear associative or causal relationship between exposure to methyl
bromide and carcinogenic or non-carcinogenic health outcomes.''
According to ATSDR (1992a) and the EPA OPP assessment (USEPA,
2006e), no studies suggest that a specific subpopulation may be more
susceptible to methyl bromide, though there is little information about
susceptible lifestages or subpopulations when exposed via the oral
route. Because the critical effects of decreased body weight, decreased
rate of body weight gain, and decreased food consumption in this study
are not specific to a sensitive subpopulation or life stage, the target
population of the general adult population was selected in deriving the
HRL for regulatory determination. EPA's OPP assessment conducted
additional exposure assessments for lifestages that may increase
exposure to methyl bromide and concluded that no lifestages have
expected exposure greater than 10% of the chronic population-adjusted
dose (cPAD), including children.
The EPA calculated an HRL of 100 [micro]g/L (rounded from 140.8
[micro]g/L) based on an EPA OPP assessment cPAD of 0.022 mg/kg/day and
using 2.5 L/day drinking water ingestion, 80 kg body weight, and a 20%
RSC factor (USEPA, 2006d; USEPA, 2011b, Table 8-1 and 3-33).
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public
Health Concern)
The EPA proposes to find that methyl bromide does not occur with a
frequency and at levels of public health concern in PWSs based on the
EPA's evaluation of the following occurrence information.
The primary data for methyl bromide are from the UCMR 3 a.m., which
was collected from January 2013 to December 2015. A total of 36,848
samples for methyl bromide were collected from 4,916 systems. Of these
systems, 49 (1.0% of systems) reported at least one detection at or
above the MRL of 0.2 [micro]g/L. A total of 0.31% of samples had
concentrations greater than or equal to the MRL (0.2 [micro]g/L).
Reported methyl bromide concentrations range from 0.2 [micro]g/L to 6.9
[micro]g/L. There was no occurrence above the \1/2\ HRL or HRL
thresholds.
In all three NAWQA cycles, methyl bromide was detected in fewer
than 1% of samples from fewer than 2% of sites. No detections were
greater than the HRL in any of the three cycles. The median
concentration among detections were 0.5 [micro]g/L and 0.8 [micro]g/L
in Cycle 1 and Cycle 3, respectively. There were no detections in Cycle
2. The results of the non-NAWQA NWIS analysis show that methyl bromide
was detected in approximately 0.1% of samples at approximately 0.1% of
sites. The median concentration among detections was 0.6 [micro]g/L.
d. Statutory Criterion #3 (Meaningful Opportunity)
Methyl bromide does not present a meaningful opportunity for health
risk reduction for persons served by PWSs based on the estimated
exposed population, including sensitive populations. UCMR 3 findings
indicate that the estimated population exposed to methyl bromide at
levels of public health concern is 0%. As a result, the Agency finds
that an NPDWR for methyl bromide does not present a meaningful
opportunity for health risk reduction.
e. Preliminary Regulatory Determination for Methyl Bromide
The Agency is making a preliminary determination to not regulate
methyl bromide with an NPDWR after evaluating health, occurrence, and
other related information against the three SDWA statutory criteria.
While data suggest that methyl bromide may have an adverse effect on
human health, the occurrence data indicate that methyl bromide is not
occurring or not likely to occur in PWSs with a frequency and at levels
of public health concern. Furthermore, in accordance with U.S.
obligations under the Montreal Protocol, production and importation of
methyl bromide has steadily declined since 2005.
Therefore, the Agency has determined that an NPDWR for methyl
bromide would not present a meaningful opportunity to reduce health
risk for persons served by PWSs. The Regulatory Determination 4 Support
Document (USEPA, 2019a) and the Occurrence Data from the Third
Unregulated Contaminant Monitoring Rule (UCMR 3) (USEPA, 2019b) present
additional information and analyses supporting the Agency's evaluation
of methyl bromide.
5. Metolachlor
a. Background
Metolachlor is a chloroacetanilide pesticide that is used as an
herbicide for weed control. Initially registered in
[[Page 14128]]
1976 for use on turf, metolachlor has more recently been used on corn,
cotton, peanuts, pod crops, potatoes, safflower, sorghum, soybeans,
stone fruits, tree nuts, non-bearing citrus, non-bearing grapes,
cabbage, certain peppers, buffalograss, guymon bermudagrass for seed
production, nurseries, hedgerows/fencerows, and landscape plantings. In
April of 1995, the EPA released a RED for metolachlor (USEPA, 1995b)
and a TRED was released in June of 2002 (USEPA, 2002c). In 2012, the
EPA reinstated tolerances for metolachlor on popcorn to rectify an
omission of these tolerances in previous documentation (USEPA, 2012b).
The metolachlor molecule can exist in right- and left-handed versions
(enantiomers), labeled ``R-'' and ``S-''. (The chemical terms are
dextrorotatory and levorotatory: the factor refers to the direction the
compound in solution rotates polarized light.) The ``S-'' version is
more potent as a pesticide. When manufacturers found a way of producing
metolachlor that was predominantly the ``S-'' enantiomer in the late
1990s, they began marketing that as ``S-metolachlor,'' while the
racemic (roughly evenly balanced) mixture continues to be sold as
``metolachlor'' (Hartzler, 2004). Metolachlor and S-metolachlor are
under registration review (USEPA, 2014b). Synonyms for metolachlor
include dual and bicep (USEPA, 2019a).
Based on private market usage data, the EPA estimated that
approximately 9 million pounds of metolachlor active ingredient and 28
million pounds of S-metolachlor active ingredient were applied annually
between 1998 and 2012, both mostly on corn (USEPA, 2014b).
According to the EPA's Pesticide Industry Sales and Usage reports,
the amount of metolachlor active ingredient (the racemic mixture) used
in the United States was between 45 and 50 million pounds in 1987;
between 63 and 69 million pounds in 1997; between 26 and 30 million
pounds in 1999; between 15 and 22 million pounds in 2001; between 1 and
5 million pounds on 2009; and between 4 and 8 million pounds in 2012.
Furthermore, the amount of S-metolachlor active ingredient used was
between 16 and 19 million pounds in 1999; between 20 and 24 million
pounds in 2001; between 28 and 33 million pounds in 2003; between 27
and 32 million pounds in 2005; between 30 and 35 million pounds in
2007; between 24 and 34 million pounds in 2009; and between 34 and 44
million pounds in 2012 (USEPA, 2019a).
USGS pesticide use data show that there has been a mild increase in
metolachlor (racemic mixture) with a greater change in the amount of S-
metolachlor relative to metolachlor. Between 2010 and 2016, the
increase in metolachlor usage is about 3 million pounds, or about 30%,
and for S-metolachlor the increase is about 25 million pounds, or about
75% (USEPA, 2019a).
If released to soil, metolachlor is expected to have moderate to
high mobility. The EPA's RED document indicates that substantial
leaching and/or runoff of metolachlor from soil is expected to occur
(USEPA, 1995b). Metolachlor is expected to have a high likelihood of
partitioning to water based on its KH, while its log
Kow and water solubility indicate that metolachlor is
expected to have a moderate likelihood of partitioning to water. The
literature provides a wide range of values for Koc (USEPA,
2019a provides additional information). Metolachlor is expected to have
moderate to high persistence in soil and water under aerobic conditions
based on aerobic biodegradation half-lives and high persistence in soil
and water under anaerobic conditions based on anaerobic biodegradation
half-lives (USEPA, 2019a).
b. Statutory Criterion #1 (Adverse Health Effects)
Metolachlor may have an adverse effect on the health of persons.
The existing toxicological database includes studies evaluating both
metolachlor and S-metolachlor. When combined with the toxicology
database for metolachlor, the toxicology database for S-metolachlor is
considered complete for risk assessment purposes (USEPA, 2018d). In
subchronic (metolachlor and S-metolachlor) (USEPA, 1995b; USEPA, 2018d)
and chronic (metolachlor) (Hazelette, 1989; Tisdel, 1983; Page, 1981;
USEPA, 2018d) toxicity studies in dogs and rats, decreased body weight
was the most commonly observed effect. Chronic exposure to metolachlor
in rats also resulted in increased liver weight and microscopic liver
lesions in both sexes (USEPA, 2018d). No systemic toxicity was observed
in rabbits when metolachlor was administered dermally, though dermal
irritation was observed at lower doses (USEPA, 2018d). Portal of entry
effects (e.g., hyperplasia of the squamous epithelium and mucous cell)
occurred in the nasal cavity at lower doses in a 28-day inhalation
study in rats (USEPA, 2018d). Systemic toxicity effects were not
observed in this study. Immunotoxicity effects were not observed in
mice exposed to S-metolachlor (USEPA, 2018d).
While some prenatal developmental studies in the rat and rabbit
with both metolachlor and S-metolachlor revealed no evidence of a
qualitative or quantitative susceptibility in fetal animals, decreased
pup body weight was observed in a two-generation study (Page, 1981,
USEPA, 2018d). Though there was no evidence of maternal toxicity,
decreased pup body weight in the F1 and F2 litters was observed,
indicating developmental toxicity (Page, 1981; USEPA, 1990b).
Therefore, sensitive lifestages to consider include infants, as well as
pregnant women and their fetus, and lactating women.
Although treatment with metolachlor did not result in an increase
in treatment-related tumors in male rats or in mice (both sexes),
metolachlor caused an increase in liver tumors in female rats (USEPA,
2018d). There was no evidence of mutagenic or cytogenetic effects in
vivo or in vitro (USEPA, 2018d). In 1994 (USEPA, 1995b), the EPA
classified metolachlor as a Group C possible human carcinogen, in
accordance with the 1986 Guidelines for Carcinogen Risk Assessment
(USEPA, 1986). In 2017 (USEPA, 2018d), the EPA re-assessed the cancer
classification for metolachlor in accordance with the EPA's final
Guidelines for Carcinogen Risk Assessment (USEPA, 2005b), and
reclassified metolachlor/S-metolachlor as ``Not Likely to be
Carcinogenic to Humans'' at doses that do not induce cellular
proliferation in the liver. This classification was based on convincing
evidence of a constitutive androstane receptor (CAR)-mediated mitogenic
MOA for liver tumors in female rats that supports a nonlinear approach
when deriving a guideline that is protective for the tumor endpoint
(USEPA, 2018d).
A recent OPP HHRA identified a two-generation reproduction study in
rats as the critical study (USEPA, 2018d). OPP proposed an RfD for
metolachlor of 0.26 mg/kg/day, derived from a NOAEL of 26 mg/kg/day for
decreased pup body weight in the F1 and F2 litters. A combined UF of
100 was used based on interspecies extrapolation (10), intraspecies
variation (10), and an FQPA Safety Factor of 1.\24\ This RfD is
[[Page 14129]]
considered protective of carcinogenic effects as well as effects
observed in chronic toxicity studies (USEPA, 2018d). The decreased F1
and F2 litter pup body weights in the absence of maternal toxicity were
considered indicative of increased susceptibility to the pups.
Therefore, a rate of 0.15 L/kg/day was selected from the Exposure
Factors Handbook (USEPA, 2011b) to represent the consumers-only
estimate of DWI based on the combined direct and indirect community
water ingestion at the 90th percentile for bottle fed infants. This
estimate is more protective than the estimate for pregnant women (0.033
L/kg/day) or lactating women (0.054 L/kg/day). DWI and BW parameters
are further outlined in the Exposure Factors Handbook (USEPA, 2011b).
---------------------------------------------------------------------------
\24\ The EPA notes that for pesticide registrations under FIFRA,
EPA's Office of Pesticides derives acute or chronic population
adjusted doses (PADs) using an FQPA Safety Factor mandated by the
FQPA taking into consideration potential pre and/or postnatal
toxicity and completeness of the data with respect to exposure and
toxicity to infants and children. In the majority of instances, the
PAD and the RfD are the same. It is only in those few instances when
the FQPA Safety Factor is attributed to residual uncertainty with
regard to exposure or pre/postnatal toxicity that the RfD and PAD
differ. More recently, FQPA Safety Factors can account for
uncertainties in the overall completeness of the toxicity database,
extrapolation from subchronic to a chronic study duration, and LOAEL
to NOAEL extrapolation.
---------------------------------------------------------------------------
The EPA OW calculated an HRL for metolachlor of 300 [micro]g/L
(rounded from 0.347 mg/L). The HRL was derived from the oral RfD of
0.26 mg/kg/day for bottle fed infants ingesting 0.15 L/kg/day water,
with the application of a 20% RSC.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public
Health Concern)
The EPA proposes to find that metolachlor does not occur with a
frequency and at levels of public health concern in public water
systems based on the EPA's evaluation of the following occurrence
information.
The primary data for metolachlor are from the UCMR 2 SS. A total of
11,192 metolachlor samples were collected from 1,198 systems. Of these
systems, three (0.25%) had metolachlor detections and none of the
detections were greater than \1/2\ the HRL or the HRL of 300 [micro]g/L
(USEPA, 2015a; USEPA, 2019a).
Nationally representative finished water occurrence data for
metolachlor are also available from the UCM Round 2 data set. In the
Round 2 cross-section states, metolachlor was detected at 108 PWSs
(0.83% of PWSs). Detected concentrations ranged from 0.01 [micro]g/L to
13.8 [micro]g/L. There were no exceedances of \1/2\ the HRL or the HRL
of 300 [micro]g/L (USEPA, 2008c; USEPA, 2019a).
To ascertain the impact of increased usage of metolachlor since the
end of UCMR 2, the EPA assessed ambient water and limited finished
water data collected after 2010. Sources of such data include the NAWQA
program and the NWIS database. The EPA found no values in the NAWQA
data set that exceeded the HRL. The highest value in the NWIS data set
(376 [micro]g/L) exceeded the HRL, but the 99th percentile value (13.3
[micro]g/L) did not exceed the HRL\25\ (USEPA, 2019a).
---------------------------------------------------------------------------
\25\ Approximately 99.9% of the metolachlor samples in NWIS are
from ambient water. The highest finished water value in the NWIS
data set is 0.24 [micro]g/L, which is much lower than the HRL.
---------------------------------------------------------------------------
d. Statutory Criterion #3 (Meaningful Opportunity)
Metolachlor does not present a meaningful opportunity for health
risk reduction for persons served by PWSs based on the estimated
exposed population, including sensitive populations. UCMR 2 findings
indicate that the estimated population exposed to metolachlor at levels
of public health concern is 0%. As a result, the Agency finds that an
NPDWR for metolachlor does not present a meaningful opportunity for
health risk reduction.
e. Preliminary Regulatory Determination for Metolachlor
The Agency is making a preliminary determination to not regulate
metolachlor with an NPDWR after evaluating health, occurrence, and
other related information against the three SDWA statutory criteria.
While data suggest that metolachlor may have an adverse effect on human
health, the occurrence data indicate that metolachlor is not occurring
or not likely to occur in PWSs with a frequency and at levels of public
health concern. The EPA will continue to evaluate metolachlor as new
finished water data become available.
Therefore, the Agency has determined that an NPDWR for metolachlor
would not present a meaningful opportunity to reduce health risk for
persons served by PWSs. The Regulatory Determination 4 Support Document
(USEPA, 2019a) and the Occurrence Data from the Second Unregulated
Contaminant Monitoring Regulation (UCMR 2) (USEPA, 2015a) present
additional information and analyses supporting the Agency's evaluation
of metolachlor.
6. Nitrobenzene
a. Background
Nitrobenzene is a synthetic aromatic nitro compound and occurs as
an oily, flammable liquid. It is commonly used as a chemical
intermediate in the production of aniline and drugs such as
acetaminophen. Nitrobenzene is also used in the manufacturing of
paints, shoe polishes, floor polishes, metal polishes, aniline dyes,
and pesticides (USEPA, 2019a).
IUR data indicate that production of nitrobenzene in the United
States increased between 1986 and 1990 and stood at over 1 billion
pounds per year from 1990 to 2006. Data from the EPA's CDR program
indicate that production of nitrobenzene was in the range of 1-5
billion pounds per year in 2012, 2013, 2014, and 2015 (USEPA, 2019a).
TRI data for nitrobenzene show that total releases were in the
range of hundreds of thousands of pounds per year from 1988 through
2016. Underground injection dominated total reported releases,
fluctuating between approximately 191,000 pounds (in 2003) and over
860,000 pounds (in 1992). On-site air emissions were in the range of
tens of thousands of pounds annually. Since 1999, surface water
discharges of nitrobenzene have not exceeded 500 pounds per year
(USEPA, 2019a).
Nitrobenzene is expected to have a high likelihood of partitioning
to water based on its water solubility. Multiple values for
Koc indicate that nitrobenzene is expected to have a
moderate to high likelihood of partitioning to water, while the log
Kow and KH indicate that nitrobenzene is expected
to have a moderate likelihood of partitioning to water. Nitrobenzene is
expected to have moderate persistence in water based on its aerobic
biodegradation half-life (USEPA, 2019a).
b. Statutory Criterion #1 (Adverse Health Effects)
Nitrobenzene may have an adverse effect on the health of persons.
NTP (1983) conducted a 90-day oral gavage study of nitrobenzene in F344
rats and B6C3F1 mice. The rats were more sensitive to the effects of
nitrobenzene exposure than the mice, and changes in absolute and
relative organ weights, hematologic parameters, splenic congestion, and
histopathologic lesions in the spleen, testis, and brain were reported.
Based on statistically significant changes in absolute and relative
organ weights, splenic congestion, and increases in reticulocyte count
and methemoglobin (metHb) concentration, a LOAEL of 9.38 mg/kg/day was
identified for the subchronic oral effects of nitrobenzene in F344 male
rats (USEPA, 2009f). This was the lowest dose studied, so a NOAEL was
not identified. The mice were treated with higher doses and were
generally more resistant to nitrobenzene toxicity, the toxic endpoints
were similar in both species.
The testis, epididymis, and seminiferous tubules of the male
reproductive system are targets of nitrobenzene toxicity in rodents. In
male rats (F344/N and CD) and mice
[[Page 14130]]
(B6C3F1), nitrobenzene exposure via the oral and inhalation routes
results in histopathologic lesions of the testis and seminiferous
tubules, testicular atrophy, a large decrease in sperm count, and a
reduction of sperm motility and/or viability, which contribute to a
loss of fertility (NTP, 1983; Bond et al., 1981; Koida et al., 1995;
Matsuura et al., 1995; Kawashima et al., 1995). These data suggest that
nitrobenzene is a male-specific reproductive toxicant (USEPA, 2009f).
Under the Guidelines for Carcinogen Risk Assessment (USEPA, 2005b),
nitrobenzene is classified as ``likely to be carcinogenic to humans''
by any route of exposure (USEPA, 2009f). A two-year inhalation cancer
bioassay in rats and mice (Cattley et al., 1994; CIIT, 1993) reported
an increase in several tumor types in both species. However, the lack
of available data, including a physiologically based biokinetic or
model that might predict the impact of the intestinal metabolism on
serum levels of nitrobenzene and its metabolites following oral
exposures, precluded the EPA's IRIS program from deriving an oral CSF
(USEPA, 2009f). Additionally, a metabolite of nitrobenzene, aniline, is
classified as a probable human carcinogen (B2) (USEPA, 1988).
Nitrobenzene has been shown to be non-genotoxic in most studies and
was classified as, at most, weakly genotoxic in the 2009 USEPA IRIS
assessment (ATSDR, 1990; USEPA, 2009f).
Of the available animal studies with oral exposure to nitrobenzene,
the 90-day gavage study conducted by NTP (1983) is the most relevant
study for deriving an RfD for nitrobenzene. This study used the longest
exposure duration and multiple dose levels. Benchmark dose software
(BMDS) (version 1.4.1c; USEPA, 2007c) was applied to estimate candidate
PODs for deriving an RfD for nitrobenzene. Data for splenic congestion
and increases in reticulocyte count and metHb concentration were
modeled. The POD derived from the male rat increased metHb data with a
benchmark response (BMR) of 1 standard deviation (SD) was selected as
the basis of the RfD (see USEPA, 2009f for additional detail).
Therefore, the benchmark dose level (BMDL) used as the POD is a
BMDL1SD of 1.8 mg/kg/day.
In deriving the RfD, the EPA's IRIS program applied a composite UF
of 1,000 to account for interspecies extrapolation (10), intraspecies
variation (10), subchronic-to-chronic study extrapolation (3), and
database deficiency (3) (USEPA, 2009f). Thus, the RfD calculated in the
2009 IRIS assessment is 0.002 mg/kg/day. The overall confidence in the
RfD was medium because the critical effect is supported by the overall
database and is thought to be protective of reproductive and
immunological effects observed at higher doses; however, there are no
chronic or multigenerational reproductive/developmental oral studies
available for nitrobenzene. Because the critical effect in this study
(increased metHb in the adult rat) is not specific to a sensitive
subpopulation or lifestage, the general adult population was selected
in deriving the HRL for regulatory determination.
The EPA calculated an HRL for the noncancer effects of nitrobenzene
of 10 [micro]g/L (rounded from 12.8 [micro]g/L), based on the RfD of
0.002 mg/kg/day, using 2.5 L/day drinking water ingestion, 80 kg body
weight, and a 20% RSC factor.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public
Health Concern)
The EPA proposes to find that nitrobenzene does not occur with a
frequency and at levels of public health concern in public water
systems based on the EPA's evaluation of the following occurrence
information.
The primary data for nitrobenzene are nationally-representative
drinking water monitoring data generated through the EPA's UCMR 1
(USEPA, 2008b), collected from 2001 to 2003. UCMR 1 is the only dataset
with nationally-representative finished water data for this
contaminant. The EPA does not anticipate nitrobenzene occurrence
meaningfully changing from the UCMR 1 monitoring period given that
reported releases to surface water have generally decreased over time
and detections of nitrobenzene in ambient waters and Six-Year Review
monitoring data are at low levels. UCMR 1 collected 33,576 nitrobenzene
samples from 3,861 PWSs. The contaminant was detected in only a small
number of those samples (0.01%) above the HRL (10 [micro]g/L), which is
the same as the MRL (10 [micro]g/L). The detections occurred in two
large water systems (one surface water, the other groundwater); the
maximum detected concentration of nitrobenzene was 100 [micro]g/L.
Occurrence data for nitrobenzene in ambient water from the NAWQA
program show that nitrobenzene was not detected in any of the samples
collected under any of the three monitoring cycles. Non-NAWQA NWIS data
show that nitrobenzene was detected in approximately 1% of samples (60
out of 7,265) and at approximately 1% of sites (25 out of 2,747). The
median concentration among detections was 83.0 [micro]g/L.
d. Statutory Criterion #3 (Meaningful Opportunity)
Nitrobenzene does not present a meaningful opportunity for health
risk reduction for persons served by PWSs based on the estimated
exposed population. UCMR 1 data indicate that the estimated population
exposed to nitrobenzene above the HRL is 0.1%. As a result, the Agency
finds that an NPDWR for nitrobenzene does not present a meaningful
opportunity for health risk reduction.
e. Preliminary Regulatory Determination for Nitrobenzene
The Agency is making a determination to not regulate nitrobenzene
with an NPDWR after evaluating health, occurrence, and other related
information against the three SDWA statutory criteria. While data
suggest that nitrobenzene may have an adverse effect on human health,
the occurrence data indicate that nitrobenzene is not occurring or not
likely to occur in PWSs with a frequency and at levels of public health
concern, and regulation of such contaminant does not present a
meaningful opportunity for health risk reduction for persons served by
PWSs. Therefore, the Agency has determined that an NPDWR for
nitrobenzene would not present a meaningful opportunity to reduce
health risk for persons served by PWSs. The Regulatory Determination 4
Support Document (USEPA, 2019a) and the Occurrence Data from the First
Unregulated Contaminant Monitoring Regulation (UCMR 1) (USEPA, 2008b)
present additional information and analyses supporting the Agency's
evaluation of nitrobenzene.
7. RDX
a. Background
RDX is a nitrated triazine and is an explosive. The name RDX is an
abbreviation of ``Royal Demolition eXplosive.'' The formal chemical
name is hexahydro-1,3,5-trinitro-1,3,5-triazine (USEPA, 2019a). Annual
production and importation of RDX in the United States was last
reported by the EPA's CDR program in 2015 to be in the range of 1-10
million pounds. It appears to have held steady in that range from 2002
onward (USEPA, 2019a).
Studies have shown that this compound is mobile in soil and
therefore likely to leach into groundwater (ATSDR, 2012a). RDX is
expected to have a high likelihood of partitioning to water based on
its log Kow and KH. Multiple values for
Koc
[[Page 14131]]
indicate that RDX is expected to have a moderate to high likelihood of
partitioning to water, while its water solubility indicates that RDX is
expected to have a moderate likelihood of partitioning to water. RDX is
expected to have low to moderate persistence based on modeled
biodegradation rates (USEPA, 2019a).
b. Statutory Criterion #1 (Adverse Health Effects)
RDX may have adverse effects on the health of persons. Available
health effects assessments include an IRIS toxicological review (USEPA,
2018e), and older assessments including an ATSDR toxicological profile
(ATSDR, 2012a) and an OW assessment published in the 1992 Drinking
Water Health Advisory: Munitions (USEPA, 1992). The EPA IRIS assessment
(2018e) presents an RfD of 0.004 mg/kg/day based on convulsions as the
critical effect observed in a subchronic study in F-344 rats by Crouse
et al. (2006). The POD for the derivation was a BMDL0.05 of
1.3 mg/kg/day derived using a pharmacokinetic model that identified the
human equivalent dose (HED) based on arterial blood concentrations in
the rats as the dose metric. A 300-fold UF (3 for extrapolation from
animals to humans, 10 for interindividual differences in human
susceptibility, and 10 for uncertainty in the database) was applied in
determination of the RfD.
Additionally, the EPA IRIS assessment (USEPA, 2018e) classified
data from the Lish et al. (1984) chronic study in B6C3F1 as
providing suggestive evidence of carcinogenic potential following the
EPA (USEPA, 2005b) guidelines. The slope factor was derived from the
lung and liver tumors' dose-response in the Lish et al. (1984) study.
The POD for the slope factor was the BMDL10 allometrically
scaled to a HED yielding a slope factor of 0.08 per mg/kg/day.
In mice fed doses of 0 to 35 mg/kg/day for 24 months in the Lish et
al. (1984) study, there were dose-dependent increases in adenomas or
carcinomas of the lungs and liver in males and females (USEPA, 2018e).
The formulation used contained 3 to 10% HMX, another munition
ingredient. The EPA assessed the toxicity of HMX (USEPA, 1988). No
chronic-duration studies were available to evaluate the carcinogenicity
of HMX (USEPA, 1988). HMX is classified as Group D, or not classifiable
as to human carcinogenicity (USEPA, 1992; USEPA, 1988). In the Levine
et al. (1983) RDX dietary exposure study with Fischer 344 rats, a
statistically significant increase in the incidence of hepatocellular
carcinomas was observed in males but not in females (USEPA, 2018e).
Although evidence of carcinogenicity included dose-dependent increases
in two experimental animal species, two sexes, and two systems (liver
and lungs), evidence supporting carcinogenicity in addition to the
B6C3F1 mouse study was not robust; this factor contributed
to the suggestive evidence of carcinogenic potential classification.
The EPA considered both the Lish et al. (1984) and Levine et al. (1983)
studies to be suitable for dose-response analysis because they were
well conducted, using similar study designs with large numbers of
animals at multiple dose levels (USEPA, 2018e). The EPA (2018e)
concluded that insufficient information was available to evaluate male
reproductive toxicity from experimental animals exposed to RDX. In
addition, the EPA (2018e) concluded that inadequate information was
available to assess developmental effects from experimental animals
exposed to RDX. The EPA selected the 2018 EPA IRIS assessment to derive
two HRLs for RDX: The RfD-derived HRL (based on Crouse et al., 2006)
and the oral cancer slope factor-derived HRL (based on Lish et al.,
1984). The EPA has generally derived HRLs for ``possible'' or Group C
carcinogens using the RfD approach in past Regulatory Determinations.
However, for RDX, the EPA decided to show both an RfD-derived and oral-
cancer-slope-factor-derived HRL since the mode of action for liver
tumors is unknown and the 1 x 10-6 cancer risk level
provides a more health protective HRL to evaluate the occurrence
information.
The RfD-derived HRL for RDX was calculated using the RfD of 0.004
mg/kg/day based on a subchronic study in F-344 rats by Crouse et al.
(2006) with convulsions as the critical effect (USEPA, 2018e). The
point of departure for the RfD calculation was a human equivalent
BMDL0.05 of 1.3 mg/kg/day. The HED was derived using a
pharmacokinetic model based on arterial blood concentrations in the
rats as the dose metric. A 300-fold uncertainty factor (3 for
extrapolation from animals to humans, 10 for interindividual
differences in human susceptibility, and 10 for uncertainty in the
database) was applied in determination of the RfD. The EPA calculated a
RfD-derived HRL of 30 [micro]g/L (rounded from 25.6 [micro]g/L), for
the noncancer effects of RDX based on the RfD of 0.004 mg/kg/day, using
2.5 L/day drinking water ingestion, 80 kg body weight, and a 20% RSC
factor.
The oral-cancer-slope-factor-derived HRL for RDX was also based on
values presented in the 2018 EPA IRIS assessment. The slope factor is
derived from the dose-response for lung and liver tumors in the Lish et
al. (1984) study, with elimination of the data for the high dose group
due to high mortality. The point of departure for the slope factor of
0.08 (mg/kg/day)-1 was the BMDL10 which was
allometrically scaled to a HED. The EPA calculated an oral cancer slope
factor-derived HRL of 0.4 [micro]g/L for RDX based on the cancer slope
factor of 0.08 (mg/kg/day)-1, using 2.5 L/day drinking water
ingestion, 80 kg body weight, and a 1 in a million cancer risk level.
The EPA's (USEPA, 2018e) derivation of an oral slope factor for
cancer is in accordance with the Guidelines for Carcinogen Risk
Assessment (USEPA, 2005b) while RDX is classified as having
``suggestive evidence of carcinogenic potential.'' Specifically, the
guidelines state ``when the evidence includes a well-conducted study,
quantitative analyses may be useful for some purposes, for example,
providing a sense of the magnitude and uncertainty of potential risks,
ranking potential hazards, or setting research priorities'' (USEPA,
2005b). The EPA IRIS assessment concluded that the database for RDX
contains well-conducted carcinogenicity studies (Lish et al., 1984;
Levine et al., 1983) suitable for dose response and that the
quantitative analysis may be useful for providing a sense of the
magnitude and uncertainty of potential carcinogenic risk (USEPA,
2018e). Therefore, the EPA felt it was important to evaluate the
occurrence information against both the RfD-derived HRL and the oral
cancer slope factor-derived HRL.
c. Statutory Criterion #2 (Occurrence at Frequency and Levels of Public
Health Concern)
The EPA proposes to find that RDX does not occur with a frequency
and at levels of public health concern in public water systems based on
the EPA's evaluation of the following occurrence information.
The primary data for RDX are nationally-representative drinking
water monitoring data generated through the EPA's UCMR 2 a.m.,
collected from 2008 to 2010 (USEPA, 2015a). UCMR 2 is the only dataset
with nationally-representative finished water data for this
contaminant. Under UCMR 2, 32,150 RDX samples were collected from 4,139
PWSs. The contaminant was detected in only a small number of samples
(0.01%) at or above the MRL (1 [micro]g/L), which is about 2.5 times
higher than the oral cancer slope factor-derived HRL (0.4 [micro]g/L).
The detections occurred
[[Page 14132]]
in three large surface water systems; the maximum detected
concentration of RDX was 1.1 [micro]g/L and the median detected value
was 1.07 [micro]g/L.
Occurrence data for RDX in ambient water are not available from the
NAWQA program; however, non-NAWQA data are available from NWIS. The
NWIS data show that RDX was detected in approximately 46% of samples
(517 out of 1,115 samples) and at approximately 29% of sites (43 out of
147 sites). The median concentration based on detections was 26.0
[micro]g/L (the 99th percentile was 120 [micro]g/L and the maximum
value was 310 [micro]g/L). While the NWIS data show that ambient waters
contain detectable levels of RDX, the nationally-representative
drinking water monitoring data indicate that only a small number of
samples are at or above the MRL; Section III.a.3 notes that ambient
water data are a less important factor in making a regulatory
determination.
d. Statutory Criterion #3 (Meaningful Opportunity)
RDX does not present a meaningful opportunity for health risk
reduction for persons served by PWSs based on the estimated exposed
population, including sensitive populations. UCMR 2 findings indicate
that the estimated population exposed to RDX at or above the MRL is
0.04%. As a result, the Agency finds that an NPDWR for RDX does not
present a meaningful opportunity for health risk reduction. Based on
the small number of samples measured at or marginally above the MRL,
the EPA does not believe that there would be enough occurrence in the
narrow range between the HRL and the MRL to change our meaningful
opportunity determination.
e. Preliminary Regulatory Determination for RDX
The Agency is making a preliminary determination to not regulate
RDX with an NPDWR after evaluating health, occurrence, and other
related information against the three SDWA statutory criteria. While
data suggest that RDX may have an adverse effect on human health, the
occurrence data indicate that RDX 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 RDX would not
present a meaningful opportunity to reduce health risk for persons
served by PWSs. The Regulatory Determination 4 Support Document (USEPA,
2019a) and the Occurrence Data from the Second Unregulated Contaminant
Monitoring Regulation (UCMR 2) (USEPA, 2015a) present additional
information and analyses supporting the Agency's evaluation of RDX.
V. Status of the Agency's Evaluation of Strontium, 1,4-Dioxane, and
1,2,3-Trichloropropane
A. Strontium
Strontium is an alkaline earth metal. On October 20, 2014 the
Agency published its preliminary regulatory determination to regulate
strontium and requested public comment on the determination and
supporting technical information (USEPA, 2014a). Informed by the public
comments received, rather than making a final determination for
strontium in 2016, the EPA delayed the final determination to consider
additional data, and to decide whether there is a meaningful
opportunity for health risk reduction by regulating strontium in
drinking water (USEPA, 2016a). Specifically, the notification on the
delayed final determination mentioned that the EPA would evaluate
additional studies on strontium exposure and health studies related to
strontium exposure. Since 2016, the EPA has worked to identify and
evaluate published studies on health effects associated with strontium
exposure, sources of exposure to strontium, and treatment technologies
to remove strontium from drinking water. In this document, the EPA is
clarifying that it is continuing with its previous 2016 decision
(USEPA, 2016a) to delay a final determination for strontium in order to
further consider additional studies related to strontium exposure.
With the preliminary regulatory determination in 2014, the EPA
published a peer-reviewed HESD for strontium (USEPA, 2014c) and an HRL
of 1,500 [micro]g/L. That document 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.
The chemical similarity of strontium to calcium allows it to
exchange for calcium in a variety of biological processes, which could
result in detrimental health effects. The most important of these
processes is the substitution of calcium in bone, affecting skeletal
development. Because the mode of action for this adverse effect is
strontium uptake into bone, the toxicity of strontium depends on an
individual's stage of bone development and their intake of nutrients
related to bone formation, such as calcium, magnesium, phosphorous and
Vitamin D. Infants, children and adolescents with low dietary intakes
of bone forming nutrients are among the most vulnerable to exposures to
high levels of strontium during periods of bone growth (USEPA, 2014c).
Women who are pregnant or lactating may also be sensitive to strontium
due to their increased requirement for bone-forming nutrients and
increased rates of bone remodeling. Breast-fed infants (from exposure
to lactating mothers who have an increased water intake), formula-fed
infants (who will ingest a greater volume of contaminated water), and
the developing fetus (from exposure to pregnant women who have an
increased water intake) are other susceptible subpopulations. In these
populations and lifestages, susceptibility is enhanced by a combination
of high exposure and lifestage.
Toxicity studies indicate that strontium can decrease the
calcification of the cartilaginous portion of bone. The results of
animal studies show that the effects of strontium at doses from 400-500
mg Sr/kg/day include small changes in bone structure and inhibition of
calcification, consistent with early development of osteomalacia and/or
``strontium rickets.'' Decreased levels of osteoclasts and associated
decreases in bone resorption can also occur at these doses in animals.
Higher doses of strontium can result in more severe bone effects
including reduced growth, large areas of unmineralized bone, bone
softening (``strontium rickets'' in young animals, and osteomalacia in
adults), excess growth of epiphyseal cartilage, and abnormal deposition
of osteoid in the metaphyses (USEPA, 2014c). More recent information on
strontium toxicity is now available in the peer reviewed literature.
The EPA intends to do an updated literature search and systematic
review before finalizing the assessment.
The primary finished drinking water occurrence data for strontium
are recent (2013-2015) nationally-representative drinking water
monitoring data generated through the EPA's UCMR 3. Under the UCMR 3,
62,913 samples were analyzed for strontium; 2.8% of those samples were
found at concentrations greater than the HRL (potentially subject to
change following examination of health studies), and 99.8% of the
samples were found at concentrations greater than the MRL (0.3
[micro]g/L). In addition, approximately 5.8% of the PWSs had at least
one detection greater than the HRL, corresponding to 6.2% of the U.S.
population.
The EPA evaluated several treatment-related studies concerning
strontium's removal from drinking water. A full-
[[Page 14133]]
scale evaluation of strontium removal from groundwater sources at four
lime softening and four ion exchange softening plants in Ohio was
reported by Lytle et al. (2017). Raw waters contained between 13 and 28
mg/L, and 1.2 and 15 mg/L strontium at the ion exchange and lime
softening plants, respectively. Ion exchange effectively removed nearly
all of the strontium, although under typical operation, treated
strontium levels were dictated by the percentage of water that by-
passed the ion exchange vessels. The amount of strontium that was
removed by lime softening ranged between 49 and 94% on average (or to
final levels of between 0.2 and 3.6 mg/L) likely dependent on treatment
and water quality conditions.
O'Donnell et al. (2016) evaluated the effectiveness of conventional
treatment (i.e., coagulation/filtration) and lime-soda ash softening
treatment methods to remove strontium from drinking water. The results
indicated that coagulation/filtration was ineffective at removing
strontium (6-12% removal) and lime-soda ash softening was more
effective, with removal percentages as high as 78%. Additionally, the
authors noted that the removal of strontium using lime-soda ash
softening in all of the softening jar tests was directly associated
with substantial calcium removal, typically at higher rates compared to
the removal of strontium.
Najm (2016) reviewed available literature for the removal of
naturally occurring stable strontium or anthropogenically produced
radioactive strontium from drinking water. The main conclusion was that
precipitative softening (i.e., lime-soda ash softening) and cation-
exchange are the most feasible options. Additionally, the report
highlights that chemical precipitation is targeted for the removal of
calcium or magnesium and it is unknown if targeted removal of strontium
can be achieved. Likewise, partial removal of calcium is unavoidable
with cation exchange, even in a process targeted for strontium removal.
While the EPA determined in 2014 that strontium may have adverse
effects on the health of persons including children, the Agency
continues to consider additional data, consult existing assessments
(such as ATSDR's Toxicological Profile from 2004 and Health Canada's
Drinking Water Guideline from 2018), and evaluate whether there is a
meaningful opportunity for health risk reduction by regulating
strontium in drinking water. Additionally, the EPA understands that
strontium may co-occur with beneficial calcium in some drinking water
systems and treatment technologies that remove strontium may also
remove calcium. The agency is evaluating the effectiveness of treatment
technologies under different water conditions, including calcium
concentrations.
B. 1,4-Dioxane
The EPA is not making a preliminary determination for 1,4-dioxane
at this time as the Agency has not determined whether there is a
meaningful opportunity for public health risk reduction. As discussed
in Section II.B.1 of this document, the EPA considers three statutory
criteria mandated under SDWA Section 1412(b)(1)(A) in making a decision
to regulate a contaminant. The EPA summarizes the current status of its
evaluation of 1,4-dioxane below. The EPA will continue to evaluate 1,4-
dioxane in the context of all three statutory criteria prior to making
such a proposal as part of a future regulatory determination.
1,4-Dioxane is used as a solvent in cellulose formulations, resins,
oils, waxes, and other organic substances; also used in wood pulping,
textile processing, degreasing; in lacquers, paints, varnishes, and
stains; and in paint and varnish removers.
Health effects information for 1,4-dioxane are available from
several sources including EPA IRIS (USEPA, 2010b), ATSDR (2012b), and
WHO (2005). The EPA's IRIS assessment (USEPA, 2010b) shows critical
effects for both noncancer (liver, kidney, and nasal toxicity) and
cancer (hepatocellular adenoma and carcinoma) endpoints.
The EPA's IRIS identified an oral reference dose (RfD) for 1,4-
dioxane of 0.03 mg/kg/day based on the Kociba (1974) 2-year rat feeding
study in which hepatic and renal toxicity in male rats were identified
as critical effects (Kociba, 1974; USEPA, 2010b; USEPA, 2013). The
LOAEL of 94 mg/kg/day was based on hepatocellular degeneration and
necrosis as well as renal tubule epithelial cell degenerative changes
and necrosis in male Sherman rats, with a NOAEL of 9.6 mg/kg/day. A
composite UF of 300 was applied to the RfD to account for
pharmacokinetic and pharmacodynamic differences between rats and humans
(10); interindividual variability (10); and database deficiencies (3)
(USEPA, 2010b; USEPA, 2013).
In 2013, the EPA IRIS classified 1,4-dioxane as ``likely to be
carcinogenic to humans'' in accordance with the EPA's 2005 Guidelines
for Carcinogenic Risk Assessment, based on evidence of carcinogenicity
in two-year studies performed with three strains of rats, two strains
of mice, and guinea pigs. The MOA by which 1,4-dioxane induces tumors
in animal models is not conclusive, so a linear low dose extrapolation
was used to estimate human carcinogenic risk (USEPA, 2013).
For the HRL derivation, the EPA selected the oral cancer slope
factor of 0.10 (mg/kg/day)-1 for 1,4-dioxane derived by the
EPA IRIS for hepatocellular adenomas or carcinomas in female mice
(2013). The principal study selected for the derivation of an oral
cancer slope factor was Kano et al., 2009.\26\ The oral cancer slope
factor was derived using linear extrapolation from the point of
departure (POD) (i.e., the 95% lower confidence limit on the dose
associated with a benchmark response near the lower end of the observed
data) calculated by fitting a curve to the experimental dose-response
data using log-logistic benchmark dose modeling. The EPA (USEPA, 2013)
indicated that a multistage model did not provide an adequate fit
because of the steep rise in the dose-response curve from the low-dose
to the mid-dose followed by a plateau between the mid- and high-dose
groups for the hepatocellular adenoma or carcinoma incidence data in
the female mice (USEPA, 2013). The EPA performed a comparison of
benchmark dose (BMD) and benchmark dose limit (BMDL) estimates derived
for studies of rats and mice and found that female mice are more
sensitive to 1,4-dioxane induced liver carcinogenicity than other
species or types of tumors (USEPA, 2013). The EPA therefore derived an
oral cancer slope factor of 0.10 (mg/kg/day)-1 for 1,4-
dioxane using the BMDL HED for hepatocellular adenomas or carcinomas in
female mice with a benchmark response of 50% as the POD (USEPA, 2013).
The EPA calculated an HRL for 1,4-dioxane of 0.32 [micro]g/L based on
the cancer slope factor of 0.1 (mg/kg/day)-1, using 2.5 L/
day drinking water ingestion, 80 kg body weight, and a 1 in a million
cancer risk level. The EPA recently released a draft risk evaluation
for 1,4-dioxane (USEPA, 2019f) that includes an oral slope factor
different than that provided by IRIS (USEPA, 2010b). Additionally,
Health Canada released a guideline technical document for 1,4-dioxane
for public consultation in 2018 (Health Canada, 2018). The consultation
period ended November 9, 2018 and a final publication is pending.
[[Page 14134]]
Once completed, the EPA will consider whether either the newer EPA oral
slope factor or Canadian guideline technical document is appropriate to
inform a regulatory determination.
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\26\ Note that the study results for the two-year drinking water
study have been reported in multiple publications and/or
communications (Kano et al., 2009; Yamazaki et al., 1994; JBRC,
1998; and Yamazaki, 2006).
---------------------------------------------------------------------------
The primary occurrence data for 1,4-dioxane are recent (2013-2015)
nationally-representative drinking water monitoring data generated
through the EPA's UCMR 3. Under the UCMR 3, 36,810 samples were
analyzed for 1,4-dioxane; 3.4% of those samples were found at
concentrations greater than the HRL, and 11.4% of the samples were
found at concentrations greater than the MRL (0.07 [micro]g/L). In
addition, approximately 7.8% of the PWSs had at least one detection
greater than the HRL.
While the health effects data suggest that 1,4-dioxane may have an
adverse effect on human health and the occurrence data indicate that
1,4-dioxane is occurring in finished drinking water above the HRL, the
EPA continues to evaluate whether there is a meaningful opportunity to
reduce health risk for persons served by PWSs by establishing an NPDWR
for 1,4-dioxane. Based on UCMR 3 data, the EPA derived a national
estimate of less than two baseline cancer cases per year attributable
to 1,4-dioxane in drinking water. The EPA derived this estimate by
using the CSF from the IRIS assessment (USEPA, 2013), a national
extrapolation of UCMR 3 population-weighted mean exposure data, and the
assumption that all UCMR 3 non-detect samples were equivalent to the
MRL (0.07 [micro]g/L), which was intended to result in a high-end
estimate of the number of national cancer cases. However, while the
number of baseline cancer cases is relatively low, other adverse health
effects following exposure to 1,4-dioxane may also contribute to
potential risk to public health, and these analyses have not yet been
completed.
As the EPA evaluates whether there is a meaningful opportunity to
protect public health by establishing a national-level drinking water
regulation for 1,4-dioxane, the Agency recognizes that several states
have ongoing activities relevant to control of 1,4-dioxane in PWSs. For
example, New York State has a recommended MCL of 1.0 [micro]g/L,\27\
and California has a notification level of 1 [micro]g/L.\28\ Based on
UCMR 3 data, 38% of systems where system averages of 1,4-dioxane were
greater than the HRL are in California and New York.
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\27\ In December 2018, the New York State Departments of Health
and Environmental Conservation announced that the New York State
Drinking Water Quality Council has recommended that the Department
of Health ``adopt an MCL for 1,4-dioxane of 1.0 part per billion''
(i.e., 1.0 [micro]g/L). New York State approved Advanced Oxidative
Process (AOP) as an effective treatment technology for 1,4-dioxane.
\28\ The California drinking water notification level for 1,4-
dioxane is 1 [mu]g/L. The response level, the level at which the
source is removed from service, is 35 [mu]g/L. The notification
level is slightly greater than the de minimis (1 X 10E-6) level
commonly used for notification levels based on cancer risk,
reflecting difficulty in monitoring 1,4-dioxane at very low
concentrations.
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The Agency is not making a preliminary determination for 1,4-
dioxane at this time as the Agency has not determined whether there is
a meaningful opportunity for public health risk reduction. The Agency
intends to complete its new risk evaluation for 1,4-dioxane that is
currently in draft (USEPA, 2019f) and consider it and the Canadian
guideline technical document and other relevant new science prior to
making a regulatory determination. This evaluation may provide clarity
as to whether there is a meaningful opportunity for an NPDWR to reduce
public health risk. The Regulatory Determination 4 Support Document
(USEPA, 2019a) and the Occurrence Data from the Third Unregulated
Contaminant Monitoring Rule (UCMR 3) (USEPA, 2019b) present additional
information and analyses supporting the Agency's evaluation of 1,4-
dioxane.
C. 1,2,3-Trichloropropane
1,2,3-Trichloropropane is a man-made chemical used as an industrial
solvent, cleaning and degreasing agent, and synthesis intermediate. Due
to analytical method-based limitations, the EPA is not making a
preliminary determination on 1,2,3-trichloropropane at this time.
Health effects information for 1,2,3-trichloropropane is available
from EPA IRIS (USEPA, 2009g), EPA OW (USEPA, 1989b), ATSDR (1992b;
2011), and California OEHHA (2009). The most recent health assessment
is the EPA's IRIS assessment (USEPA, 2009g), which uses an NTP study
(NTP, 1993) to derive both an RfD of 0.004 mg/kg/day for noncancer
effects and a CSF of 30 (mg/kg/day)-1. The NTP (1993)
chronic duration oral bioassay gavage study of rats and mice shows
critical effects for both noncancer (increased liver weight) and cancer
endpoints (alimentary system squamous cell neoplasms, liver
hepatocellular adenomas or carcinomas, Harderian gland adenoma,
uterine/cervix adenomas or carcinomas) for oral exposure. 1,2,3-
Trichloropropane received a classification of ``likely to be
carcinogenic to humans'' based on statistically significant increases
in multiple tumors types in rats and mice.
The HRL for the cancer effects is based on the EPA IRIS cancer
slope factor for 1,2,3-trichloropropane of 30 (mg/kg/day)-1
(USEPA, 2009g). The oral cancer slope factor was calculated for adult
exposures and does not take into account presumed early-life
susceptibility to 1,2,3-trichloropropane exposure. As outlined in the
IRIS assessment, the evidence indicates that 1,2,3-trichloropropane
carcinogenicity occurs via a mutagenic MOA. The EPA provides guidance
on assessing early life carcinogen exposure (USEPA, 2005b; USEPA,
2005c), and children potentially exposed to mutagenic carcinogens can
be assumed to have the potential for increased early-life
susceptibility to carcinogens. Therefore, for mutagenic carcinogens,
the EPA recommends that risk assessors apply special adjustment factors
to a given cancer slope factor which are dependent on age (ADAFs).
Section 5.4.5 of the IRIS assessment for 1,2,3-trichloropropane
describes application of the ADAFs to the CSF. The EPA recommends the
application of these ADAFs when estimating cancer risks from early life
(<16 years of age) exposure to 1,2,3-trichloropropane (USEPA, 2009g).
Thus, the EPA calculated an HRL of 0.0004 [micro]g/L (0.4 ng/L) using
ADAFs and a cancer risk level of one cancer case per million people.
The primary occurrence data for 1,2,3-trichloropropane are
nationally-representative drinking water monitoring data generated
through the EPA's UCMR 3 (2013-2015). Under the UCMR 3, an MRL of 0.03
[micro]g/L was identified for the method used to analyze that
contaminant (EPA Method 524.3).\29\ For the 36,848 samples collected
during UCMR 3, 0.69% of the samples exceeded the MRL. Further, about
1.4% of PWSs had at least one detection over the MRL, corresponding to
2.5% of the population.
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\29\ Under UCMR 3, the MRL for an analyte, as determined by a
specified analytical method, is a reporting threshold set at a level
at which quantitation is achievable, with 95% confidence, by a
capable analyst/laboratory at least 75% of the time when using the
specified analytical method. This simultaneously accounts for both
precision and accuracy.
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While the UCMR 3 data indicated 1,2,3-trichloropropane occurrence
was relatively low at concentrations above the MRL, the MRL (0.03
[micro]g/L) is more than 75 times the HRL (0.0004 [micro]g/L) for
1,2,3-trichloropropane. This discrepancy allows for a broad range of
potential contaminant concentrations that could be in exceedance of the
HRL but below the MRL. Thus, the EPA needs additional lower-level
occurrence information prior to making a preliminary regulatory
determination
[[Page 14135]]
for 1,2,3-trichloropropane. The Regulatory Determination 4 Support
Document (USEPA, 2019a) and the Occurrence Data from the Third
Unregulated Contaminant Monitoring Rule (UCMR 3) (USEPA, 2019b) present
additional information and analyses supporting the Agency's evaluation
of 1,2,3-trichloropropane.
VI. EPA's Request for Comments and Next Steps
The EPA invites commenters to submit any relevant data or
information pertaining to the preliminary regulatory determinations
identified in this document, as well as other relevant comments. The
EPA will consider the public comments and/or any new, relevant data
submitted for the contaminants discussed in this document and in the
supporting rationale.
The data and information requested by the EPA include peer-reviewed
science and supporting studies conducted in accordance with sound and
objective scientific practices, and data collected by accepted methods
or best available methods (if the reliability of the method and the
nature of the review justifies use of the data).
Peer-reviewed data are studies/analyses that have been reviewed by
qualified individuals (or organizations) who are independent of those
who performed the work, but who are collectively equivalent in
technical expertise (i.e., peers) to those who performed the original
work. A peer review is an in-depth assessment of the assumptions,
calculations, extrapolations, alternate interpretations, methodology,
acceptance criteria, and conclusions pertaining to the specific major
scientific and/or technical work products and the documentation that
supports them (USEPA, 2015b).
Specifically, the EPA is requesting comment and/or information
related to the following aspects:
The health effects information considered by the Agency in
making the preliminary determinations described in this document. The
EPA requests commenters identify any additional peer reviewed studies
that could inform the final regulatory determination.
Drinking water occurrence information considered by the
Agency in making the preliminary determinations described in this
document. The EPA requests commenters identify any additional data and
studies upon the occurrence of these contaminants in drinking water.
The EPA requests comment on what additional information
the Agency should consider in developing a NPDWR for PFOA and PFOS
beyond the information described in this document. The EPA notes that
ongoing evaluations of PFOA and PFOS health effects include the
National Toxicology Program's Technical Report on the Toxicology and
Carcinogenesis Studies of PFOA, ATSDR toxicity assessments, as well as
state health assessments.
The EPA requests comment upon potential regulatory
constructs, grouping approaches, and potential monitoring requirements
described in Sections III.A.1. and IV.B.1.f of this document.
The EPA requests additional studies and data that
characterizes the occurrence of PFAS in drinking water. The Agency is
particularly interested in datasets that include:
[cir] Information on the sample data that includes: Location and
sample type (raw or treated water; groundwater or surface water
source);
[cir] Information on the measurement results that includes:
Specific analyte, analytical method used; measurement results; units
and qualifiers; detection limit values (for non-detects);
[cir] Sample collection dates for a given sample and analysis dates
for each analytical result;
[cir] Meta data that could include the organization that created
the dataset; contact information; the purpose of the data collection;
the size of the dataset; and indication of data quality (such as a
quality assurance project plan); and
[cir] An accompanying data dictionary and reference to Quality
Assurance processes for sample collection and analysis information.
The EPA requests peer reviewed health effects studies for
PFAS other than PFOA and PFOS that the Agency could consider in future
regulatory decision making.
Specific information about removal of PFOA, PFOS, and
other PFAS from drinking water under field conditions, including
information about effectiveness and costs of various treatment
approaches and effectiveness of PFAS removal in the presence of other
contaminants and constituents.
The EPA intends to carefully evaluate the public comments received
on the eight preliminary determinations and issue its final regulatory
determinations. If the Agency makes a final determination to regulate
any of the contaminants, the EPA intends to propose an NPDWR within 24
months and promulgate a final NPDWR within 18 months following the
proposal.\30\ In addition, the EPA will also consider information
provided about the three contaminants discussed in Section V to inform
potential future regulatory determinations.
---------------------------------------------------------------------------
\30\ The statute authorizes a nine-month extension of this
promulgation date.
---------------------------------------------------------------------------
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Dated: February 20, 2020.
Andrew R. Wheeler,
Administrator.
[FR Doc. 2020-04145 Filed 3-9-20; 8:45 am]
BILLING CODE 6560-50-P