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Proposed Rule2024-02247

Unregulated Contaminant Monitoring Rule; Methods Request and Webinar

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Published

February 8, 2024

Issuing agencies

Environmental Protection Agency

Abstract

The U.S. Environmental Protection Agency (EPA) is requesting public input on drinking water analytical methods for emerging contaminants in drinking water, particularly those listed on the agency's Fifth Contaminant Candidate List (CCL 5), that might support monitoring under the Unregulated Contaminant Monitoring Rule. This notice describes published drinking water analytical methods and EPA drinking water methods currently in development for the CCL and other emerging contaminants, with an expectation that some of these methods will support the sixth Unregulated Contaminant Monitoring Rule (UCMR 6) and/or other future cycles of the UCMR program. The agency is also announcing a virtual public meeting (via webinar) to discuss potential approaches to developing UCMR 6. The webinar will discuss the following: drinking water analytical methods and contaminants being considered, UCMR 6 sampling design, laboratory approval, and other potential aspects of the monitoring approach. The agenda will include time for brief remarks by participants who pre- register.

Full Text

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<title>Federal Register, Volume 89 Issue 27 (Thursday, February 8, 2024)</title>
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[Federal Register Volume 89, Number 27 (Thursday, February 8, 2024)]
[Proposed Rules]
[Pages 8584-8598]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2024-02247]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 141

[EPA-HQ-OW-2023-0469; FRL-10857-04-OW]

Unregulated Contaminant Monitoring Rule; Methods Request and
Webinar

AGENCY: Environmental Protection Agency (EPA).

ACTION: Request for public comment and notice of a public meeting.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is requesting
public input on drinking water analytical methods for emerging
contaminants in drinking water, particularly those listed on the
agency's Fifth Contaminant Candidate List (CCL 5), that might support
monitoring under the Unregulated Contaminant Monitoring Rule. This
notice describes published drinking water analytical methods and EPA
drinking water methods currently in development for the CCL and other
emerging contaminants, with an expectation that some of these methods
will support the sixth Unregulated Contaminant Monitoring Rule (UCMR 6)
and/or other future cycles of the UCMR program.
The agency is also announcing a virtual public meeting (via
webinar) to discuss potential approaches to developing UCMR 6. The
webinar will discuss the following: drinking water analytical methods
and contaminants being considered, UCMR 6 sampling design, laboratory
approval, and other potential aspects of the monitoring approach. The
agenda will include time for brief remarks by participants who pre-
register.

DATES: Comments must be received on or before April 8, 2024. Public
meeting: The EPA will host a webinar regarding UCMR 6 development on
April 17, 2024 and April 18, 2024. The same material will be presented
twice. Please refer to the SUPPLEMENTARY INFORMATION section for
additional information on the webinar.

ADDRESSES: The agency invites comments on analytical methods for
emerging contaminants in drinking water, particularly those listed on
CCL 5, to aid in the EPA's consideration of methods to support UCMR
monitoring. Comments should refer to Docket ID No. EPA-HQ-OW-2023-0469
and may be submitted by any of the following options:
<bullet> Federal eRulemaking Portal: <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>
(preferred). Follow the online instructions for submitting comments.
<bullet> Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Office of Ground Water and Drinking Water Docket, Mail Code
28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460.
<bullet> Hand Delivery or Courier: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operations are 8:30 a.m. to 4:30 p.m.,
Monday through Friday (except Federal Holidays).
Instructions: All material submitted must include the Docket ID for
this rulemaking. Comments received by the EPA (regardless of how they
are submitted) may be posted without change to <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal information provided. For
detailed instructions on sending comments, see the ``Public
Participation'' heading of the SUPPLEMENTARY INFORMATION section of
this document.
Registration information for the UCMR 6 ``pre-proposal'' webinar
can be found at <a href="https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials">https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials</a>. The webinars will begin at
11:00 a.m. eastern time and will conclude at 5:00 p.m. eastern time on
the scheduled dates. Refer to the ``Public Participation'' heading of
the SUPPLEMENTARY INFORMATION section below for additional information
if you would like to sign up to make remarks during the webinar.

FOR FURTHER INFORMATION CONTACT: Brenda Bowden, Standards and Risk
Management Division, Office of Ground Water and Drinking Water (MS
140), Environmental Protection Agency, 26 West Martin Luther King
Drive, Cincinnati, OH 45268; telephone number: (513) 569-7961; or email
address: <a href="/cdn-cgi/l/email-protection#66040911020308480414030802072603160748010910"><span class="__cf_email__" data-cfemail="03616c7467666d2d6171666d6762436673622d646c75">[email&#160;protected]</span></a>; or Will Adams, Standards and Risk
Management Division, Office of Ground Water and Drinking Water (MS
140), Environmental Protection Agency, 26 West Martin Luther King
Drive, Cincinnati, OH 45268; telephone number: (513) 569-7656; or email
address: <a href="/cdn-cgi/l/email-protection#127376737f613c657b7e7e7b737f527762733c757d64"><span class="__cf_email__" data-cfemail="a4c5c0c5c9d78ad3cdc8c8cdc5c9e4c1d4c58ac3cbd2">[email&#160;protected]</span></a>.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Public Participation
A. Written Comments on Drinking Water Analytical Methods for
Emerging Contaminants
B. Participation in UCMR 6 Pre-Proposal Webinar
II. General Information
A. Does this action apply to me?
B. How does the EPA establish health standards for emerging
contaminants in drinking water under the Safe Drinking Water Act?
C. Why is the EPA requesting analytical method information on
unregulated contaminants in drinking water?
D. What is the basis for this action?
III. Background
A. What is the status of the drinking water analytical methods
for contaminants on the CCL 5?
B. What drinking water analytical methods are being developed by
the EPA to address contaminants on CCL 5?
1. Draft EPA Method(s) for PFAS.
2. Draft EPA Method 562--Determination of selected pesticides in
drinking water by solid phase extraction and liquid chromatography/
tandem mass spectrometry (LC/MS/MS).
3. Draft EPA Method Purgeable Organics--Measurement of purgeable
organic compounds in water by capillary column gas chromatography/
mass spectrometry (GC/MS). This method is expected to support the
analysis of drinking water for 1,2,3-trichloropropane (TCP) and
other purgeable organic compounds. The target contaminants for this
method are shown in Exhibit 7.
4. Draft EPA Method Legionella--Legionella spp. and Legionella
pneumophila quantitative polymerase chain reaction (qPCR) detection.
5. Draft EPA Method Mycobacterium--Mycobacterium abscessus
culture

[[Page 8585]]

recovery with matrix-assisted laser desorption/ionization mass
spectrometry (MALDI-MS).
6. Draft EPA Method Mycobacterium qPCR- Mycobacterium avium and
Mycobacterium intracellulare quantitative polymerase chain reaction
(qPCR) detection.
C. What other drinking water analytical methods are being
considered by the EPA to address emerging contaminants?
1. Draft EPA Method EOF--Screening method for the determination
of extractable organic fluorine (EOF) in drinking water by anion
exchange solid phase extraction and combustion ion chromatography
(CIC).
2. Draft EPA Method Microplastics--Analysis of microplastics in
drinking water using spectroscopic instrumentation.
D. What information should the public provide when submitting
comments about drinking water analytical methods for CCL 5 and other
emerging contaminants?
IV. References

Abbreviations and Acronyms

[micro]m Micrometer
11Cl-PF3OUdS 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic Acid
4:2FTS 1H,1H, 2H, 2H-perfluorohexane Sulfonic Acid
6:2FTS 1H,1H, 2H, 2H-perfluorooctane Sulfonic Acid
8:2FTS 1H,1H, 2H, 2H-perfluorodecane Sulfonic Acid
9Cl-PF3ONS 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic Acid
ADONA 4,8-dioxa-3H-perfluorononanoic Acid
AOF Adsorbable Organic Fluorine
ASTM ASTM International
BCAA Bromochloroacetic Acid
BCIM Bromochloroiodomethane
BDCAA Bromodichloroacetic Acid
BDCNM Bromodichloronitromethane
BDIM Bromodiiodomethane
BFB 4-bromofluorobenzene
CASRN Chemical Abstracts Service Registry Number
CBI Confidential Business Information
CCL Contaminant Candidate List
CDIM Chlorodiiodomethane
CFR Code of Federal Regulations
CIC Combustion Ion Chromatography
Cq Quantification Cycle
CWS Community Water System
DBAN Dibromoacetonitrile
DBCAA Dibromochloroacetic Acid
DBCNM Dibromochloronitromethane
DBIM Dibromoiodomethane
DBP Disinfection Byproduct
DCAN Dichloroacetonitrile
DCIM Dichloroiodomethane
DI Deionized Water
DNA Deoxyribonucleic Acid
DTXSID Distributed Structure Searchable Toxicity Substance
Identifiers
EOF Extractable Organic Fluorine
EPA U.S. Environmental Protection Agency
FEM Forum on Environmental Measurement
FR Federal Register
FTIR Fourier Transform Infrared
GC Gas Chromatography
GC/MS Gas Chromatography/Mass Spectrometry
HFPO-DA Hexafluoropropylene Oxide Dimer Acid
ISO or ISO/TS International Organization for Standardization
LC-MS/MS or LC/MS/MS Liquid Chromatography/Tandem Mass Spectrometry
LDIR Laser Direct Infrared
Leg16S Legionella Species
Lp16S Legionella pneumophila
MALDI-MS Matrix-assisted Laser Desorption/Ionization Mass
Spectrometry
MBC Carbendazim
MIP Legionella pneumophila
mL Milliliter
mm Millimeter
MTBE Methyl Tert-butyl Ether
NAICS North American Industry Classification System
NCOD National Contaminant Occurrence Database
NDBA Nitrosodibutylamine
NDEA N-Nitrosodiethylamine
NDMA N-Nitrosodimethylamine
NDPA N-Nitrosodi-n-propylamine
NDPhA N-Nitrosodiphenylamine
NEtFOSAA N-ethyl Perfluorooctanesulfonamidoacetic Acid
NFDHA Nonafluoro-3,6-dioxaheptanoic Acid
ng/L Nanogram per Liter
NMeFOSAA N-methyl Perfluorooctanesulfonamidoacetic Acid
NPYR Nitrosopyrrolidine
NTM Nontuberculous Mycobacteria
NTNCWS Non-Transient Non-Community Water System
OGWDW Office of Ground Water and Drinking Water
PBI Proprietary Business Information
PFAS Per- and Polyfluoroalkyl Substances
PFBA Perfluorobutanoic Acid
PFBS Perfluorobutanesulfonic Acid
PFDA Perfluorodecanoic Acid
PFDoA Perfluorododecanoic Acid
PFEESA Perfluoro(2-ethoxyethane) Sulfonic Acid
PFHpA Perfluoroheptanoic Acid
PFHpS Perfluoroheptanesulfonic Acid
PFHxA Perfluorohexanoic Acid
PFHxS Perfluorohexanesulfonic Acid
PFMBA Perfluoro-4-methoxybutanoic acid
PFMPA Perfluoro-3-methoxypropanoic Acid
PFNA Perfluorononanoic Acid
PFOA Perfluorooctanoic Acid
PFOS Perfluorooctanesulfonic Acid
PFPeA Perfluoropentanoic Acid
PFPeS Perfluoropentanesulfonic Acid
PFTA Perfluorotetradecanoic Acid
PFTrDA Perfluorotridecanoic Acid
PFUnA Perfluoroundecanoic Acid
PTFE Polytetrafluoroethylene
PWS Public Water System
QC Quality Control
qPCR Quantitative Polymerase Chain Reaction
SDWA Safe Drinking Water Act
SM Standard Methods for the Examination of Water and Wastewater
SPE Solid Phase Extraction
SRMD Standards and Risk Management Division
TBAA Tribromoacetic Acid
TCEP Tris(2-chloroethyl) Phosphate
TCNM Chloropicrin (trichloronitromethane)
TCP Trichloropropane
TIM Iodoform (triiodomethane)
UCMR Unregulated Contaminant Monitoring Rule
VCSB Voluntary Consensus Standards Board

I. Public Participation

A. Written Comments on Drinking Water Analytical Methods for Emerging
Contaminants

Submit your comments on drinking water analytical methods for
emerging contaminants, particularly those listed in this Federal
Register notice, identified by Docket ID No. EPA-HQ-OW-2023-0469, at
<a href="https://www.regulations.gov">https://www.regulations.gov</a> (preferred), or using one of the other
options 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 any information to
the EPA via <a href="https://www.regulations.gov">https://www.regulations.gov</a> that you consider to be
Confidential Business Information (CBI), Proprietary Business
Information (PBI), 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 want
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). Please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a> for additional submission methods; the
full EPA public comment policy; information about CBI, PBI, or
multimedia submissions; and general guidance on making effective
comments.

B. Participation in UCMR 6 Pre-Proposal Webinar

All who want to attend the webinar, please refer to the SUMMARY
section for instructions on webinar registration. For those who want to
make remarks at the webinar, the EPA is scheduling speakers. To sign up
to speak, please use the online registration form available at <a href="https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials">https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials</a> or contact the EPA's support contractor, Cadmus,
at <a href="/cdn-cgi/l/email-protection#e8bdaba5babf8d8a8186899aa88b898c859d9b8f9a879d98c68b8785"><span class="__cf_email__" data-cfemail="81d4c2ccd3d6e4e3e8efe0f3c1e2e0e5ecf4f2e6f3eef4f1afe2eeec">[email&#160;protected]</span></a>. The last day to pre-register to speak
at the webinar is April

[[Page 8586]]

9, 2024. On April 16, (one day prior), the EPA will post an agenda that
will identify scheduled speakers at: <a href="https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials">https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials</a>. If
there is additional time for public speakers after scheduling those who
pre-registered, EPA will take requests during the webinar via the chat
box. The EPA will accommodate requests to speak (via pre-registration
and during the webinar) in the order received and as time permits.
The agency's current plan is to provide each speaker with ten
minutes. The EPA may adjust this time depending on the number of
organizations that register to speak. The agency asks that only one
person present on behalf of an organization. The EPA encourages
commenters to provide the agency with an advance copy of their remarks
by emailing them to <a href="/cdn-cgi/l/email-protection#a7f2e4eaf5f0c2c5cec9c6d5e7c4c6c3cad2d4c0d5c8d2d789c4c8ca"><span class="__cf_email__" data-cfemail="1c495f514e4b797e75727d6e5c7f7d7871696f7b6e73696c327f7371">[email&#160;protected]</span></a>. The EPA may ask and
answer clarifying questions during the webinar but will generally not
respond to the remarks made by speakers during the webinar.
Please note that any updates to the webinar plan will be posted to
<a href="https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials">https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials</a> and will be emailed to those who register
to participate. The EPA does not intend to publish another document in
the Federal Register announcing updates, if any. If you require the
services of an interpreter or special accommodations, please identify
your needs at least one week in advance as part of your registration.

II. General Information

A. Does this action apply to me?

This notice invites comments on drinking water analytical methods
and is directed to those interested in or involved with developing
analytical methods for unregulated contaminants in drinking water. It
may also be of particular interest to laboratories that conduct
chemical or microbiological testing for drinking water contaminants,
including testing in support of the UCMR program.
This notice also announces a webinar to discuss potential
approaches to developing UCMR 6. This notice does not impose any
requirements.

------------------------------------------------------------------------
Examples of potentially
Category regulated entities NAICS *
------------------------------------------------------------------------
State, local, & Tribal State, local, and Tribal 924110
governments. governments that analyze water
samples on behalf of PWSs
required to conduct such
analysis; State, local, and
Tribal governments that
directly operate Community
Water Systems (CWSs) and Non-
Transient Non-Community Water
Systems (NTNCWSs) required to
monitor.
Industry...................... Private operators of CWSs and 221310
NTNCWSs required to monitor.
Municipalities................ Municipal operators of CWSs and 924110
NTNCWSs required to monitor.
Laboratories.................. Laboratories conducting 541380
analysis.
------------------------------------------------------------------------
* NAICS = North American Industry Classification System

This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by this
action. This table includes the types of entities that the EPA is now
aware could potentially be affected by this action. Other types of
entities not listed could also be affected. To determine whether your
entity is affected by this action, you should carefully examine the
applicability criteria found in Title 40 in the Code of Federal
Regulations (CFR) at 40 CFR 141.2 and 141.3, and the applicability
criteria found in 40 CFR 141.40(a)(1) and (2). If you have questions
regarding the applicability of this action to a particular entity,
consult the person listed in the FOR FURTHER INFORMATION CONTACT
section.

B. How does the EPA establish health standards for emerging
contaminants in drinking water under the Safe Drinking Water Act?

Under the 1996 amendments to the Safe Drinking Water Act (SDWA),
Congress established a multi-step, risk-based approach for determining
which contaminants could become subject to drinking water standards.
The EPA is required to publish a Contaminant Candidate List (CCL) every
five years that identifies contaminants that are not subject to any
proposed or promulgated drinking water regulations, are known or
anticipated to occur in Public Water Systems (PWSs), and may require
future regulation under SDWA. The EPA must also determine whether or
not to regulate at least five contaminants from the CCL in a separate
process called Regulatory Determinations. Information on these
processes can be found at: <a href="https://www.epa.gov/ccl">https://www.epa.gov/ccl</a>.
Per SDWA, the EPA implements section 1445(a)(2), Monitoring Program
for Unregulated Contaminants. The EPA requires that PWSs monitor for a
new set of unregulated contaminants every five years to generate
occurrence data in support of the agency's CCL and Regulatory
Determination processes. The EPA must vary the frequency and schedule
for monitoring based on the number of people served, the source water,
and the contaminants likely to be found. The data collected through the
UCMR program are made available to the public through the National
Contaminant Occurrence Database (NCOD) for drinking water. UCMR results
can be viewed by the public via NCOD (<a href="https://www.epa.gov/sdwa/national-contaminant-occurrence-database-ncod">https://www.epa.gov/sdwa/national-contaminant-occurrence-database-ncod</a>) or via the UCMR web page
at: <a href="https://www.epa.gov/dwucmr">https://www.epa.gov/dwucmr</a>.

C. Why is the EPA requesting analytical method information on
unregulated contaminants in drinking water?

Analytical methods are essential to gathering occurrence data under
the UCMR program. Robust analytical methods with sufficient
sensitivity, accuracy, and precision are needed.

D. What is the basis for this action?

This notice provides the public with the EPA's assessment of
published drinking water analytical methods and methods in development
for emerging contaminants, particularly those focusing on the CCL 5.
The EPA is seeking public comments on method development to reach a
broader audience and provide an opportunity to improve public
participation. Separate public meetings on method development have not
been well attended in the past, and this Federal Register notice
enables those who cannot participate in the meeting to provide input.
This notice also announces webinars in April 2024 that will allow
for early engagement in the agency's development of UCMR 6.

[[Page 8587]]

III. Background

A. What is the status of the drinking water analytical methods for
contaminants on the CCL 5?

Exhibits 1-5 list the contaminants on the final CCL 5 in the
Federal Register published November 14, 2022 (87 FR 68060) (USEPA,
2022b). The current status of drinking water analytical methods from
the EPA and voluntary consensus standards bodies (VCSBs) such as, ASTM
International (ASTM), Standard Methods (SM), and International
Organization for Standardization (ISO), are included in this notice.
The ASTM, SM, and ISO methods listed in Exhibits 1-5 may or may not
contain the standards and quality control (QC) requirements deemed
necessary by the agency and may need to be adapted to support UCMR
monitoring. Exhibits 6-10 list methods in development by the EPA for
contaminants from CCL 5 that do not currently have drinking water
analytical methods. The EPA recognizes that there may be other entities
developing drinking water analytical methods and encourages commenters
to make the agency aware of them. Please submit comments to the EPA
following the process described in section III.D of this notice.

Exhibit 1--CCL 5 Chemical Contaminants/Groups and Associated Drinking Water Analytical Methods
----------------------------------------------------------------------------------------------------------------
Chemical name CASRN \1\ DTXSID \2\ Drinking water method(s) \3\
----------------------------------------------------------------------------------------------------------------
1,2,3-Trichloropropane...................... 96-18-4 DTXSID9021390 In Development, EPA 502.2, EPA
504.1, EPA 524.2, EPA 524.3,
EPA 524.4, EPA 551.1, ASTM
D5790-18, SM 6200 B, SM 6200
C.
1,4-Dioxane................................. 123-91-1 DTXSID4020533 EPA 522, EPA 541.
17-alpha ethynyl estradiol.................. 57-63-6 DTXSID5020576 EPA 539.
2,4-Dinitrophenol........................... 51-28-5 DTXSID0020523 EPA 528.
2-Aminotoluene.............................. 95-53-4 DTXSID1026164 EPA 530.
2-Hydroxyatrazine........................... 2163-68-0 DTXSID6037807 Research Needed.
6-Chloro-1,3,5-triazine-2,4-diamine......... 3397-62-4 DTXSID1037806 Research Needed.
Acephate.................................... 30560-19-1 DTXSID8023846 EPA 538.
Acrolein.................................... 107-02-8 DTXSID5020023 Research Needed.
alpha-Hexachlorocyclohexane................. 319-84-6 DTXSID2020684 EPA 508, EPA 508.1, EPA 525.2,
EPA 525.3.
Anthraquinone............................... 84-65-1 DTXSID3020095 Research Needed.
Bensulide................................... 741-58-2 DTXSID9032329 EPA 540, EPA 543.
Bisphenol A................................. 80-05-7 DTXSID7020182 SM 6810 B.
Boron....................................... 7440-42-8 DTXSID3023922 EPA 200.5, EPA 200.7, SM 3120
B, SM 4500-B B, SM 4500-B C.
Bromoxynil.................................. 1689-84-5 DTXSID3022162 In Development.
Carbaryl.................................... 63-25-2 DTXSID9020247 EPA 531.1, EPA 531.2, ASTM
D5315-04, SM 6610 B.
Carbendazim (MBC)........................... 10605-21-7 DTXSID4024729 In Development.
Chlordecone (Kepone)........................ 143-50-0 DTXSID1020770 EPA 527 *, In Development.
Chlorpyrifos................................ 2921-88-2 DTXSID4020458 EPA 525.2, EPA 525.3, EPA 527,
EPA 600/R-16/114.
Cobalt...................................... 7440-48-4 DTXSID1031040 EPA 200.7, EPA 200.8, EPA
200.9, ASTM D3558-15 A, ASTM
D3558-15 B, SM 3111 B, SM 3111
C, SM 3113 B, SM 3120 B.
Cyanotoxins \4\ \5\......................... Multiple Multiple See Exhibit 2.
Desethylatrazine............................ 6190-65-4 DTXSID5037494 EPA 523, EPA 536.
Desisopropyl atrazine....................... 1007-28-9 DTXSID0037495 EPA 523, EPA 536.
Desvenlafaxine.............................. 93413-62-8 DTXSID40869118 Research Needed.
Diazinon.................................... 333-41-5 DTXSID9020407 EPA 526.
Dicrotophos................................. 141-66-2 DTXSID9023914 EPA 538, EPA 600/R-16/114.
Dieldrin.................................... 60-57-1 DTXSID9020453 EPA 505, EPA 508, EPA 508.1,
EPA 525.2, EPA 525.3, ASTM
D5175-91.
Dimethoate.................................. 60-51-5 DTXSID7020479 EPA 527.
Disinfection byproducts (DBPs) \4\ \6\...... Multiple Multiple See Exhibit 3.
Diuron...................................... 330-54-1 DTXSID0020446 EPA 532.
Ethalfluralin............................... 55283-68-6 DTXSID8032386 Research Needed.
Ethoprop.................................... 13194-48-4 DTXSID4032611 EPA 507, EPA 525.2, EPA 525.3.
Fipronil.................................... 120068-37-3 DTXSID4034609 In Development.
Fluconazole................................. 86386-73-4 DTXSID3020627 Research Needed.
Flufenacet.................................. 142459-58-3 DTXSID2032552 In Development.
Fluometuron................................. 2164-17-2 DTXSID8020628 EPA 532.
Iprodione................................... 36734-19-7 DTXSID3024154 In Development.
Lithium..................................... 7439-93-2 DTXSID5036761 EPA 200.7, ASTM D1976-20, SM
3111 B, SM 3120 B, SM 3500-Li
B.
Malathion................................... 121-75-5 DTXSID4020791 EPA 527.
Manganese................................... 7439-96-5 DTXSID2024169 EPA 200.5, EPA 200.7, EPA
200.8, EPA 200.9, SM 3111 B,
SM 3111 C, SM 3113 B, SM 3120
B, SM 3500-Mn B.
Methomyl.................................... 16752-77-5 DTXSID1022267 EPA 531.1, EPA 531.2, EPA 540,
ASTM D5315-04, ASTM D7645-23,
SM 6610 B.
Methyl tert-butyl ether (MTBE).............. 1634-04-4 DTXSID3020833 EPA 524.2, EPA 524.3, EPA
524.4, ASTM D5790-18, SM 6200
B, SM 6200 C.
Methylmercury............................... 22967-92-6 DTXSID9024198 Research Needed.
Molybdenum.................................. 7439-98-7 DTXSID1024207 EPA 200.7, EPA 200.8, SM 3111
D, SM 3113 B, SM 3120 B.
Nonylphenol \7\............................. 25154-52-3 DTXSID3021857 EPA 559.
Norflurazon................................. 27314-13-2 DTXSID8024234 EPA 507, EPA 525.2, EPA 525.3,
EPA 527.*
Oxyfluorfen................................. 42874-03-3 DTXSID7024241 EPA 525.3.

[[Page 8588]]

Per- and polyfluoroalkyl substances (PFAS) Multiple Multiple See Exhibit 4.
\4\ \8\.
Permethrin.................................. 52645-53-1 DTXSID8022292 EPA 508, EPA 508.1, EPA 525.2,
EPA 525.3.
Phorate..................................... 298-02-2 DTXSID4032459 EPA 525.3, EPA 600/R-16/114.
Phosmet..................................... 732-11-6 DTXSID5024261 Research Needed.
Phostebupirim............................... 96182-53-5 DTXSID1032482 Research Needed.
Profenofos.................................. 41198-08-7 DTXSID3032464 EPA 525.3.
Propachlor.................................. 1918-16-7 DTXSID4024274 EPA 508, EPA 508.1, EPA 525.2,
EPA 525.3.
Propanil.................................... 709-98-8 DTXSID8022111 EPA 532.
Propargite.................................. 2312-35-8 DTXSID4024276 Research Needed.
Propazine................................... 139-40-2 DTXSID3021196 EPA 507, EPA 523, EPA 525.2,
EPA 525.3, EPA 527, EPA 536.
Propoxur.................................... 114-26-1 DTXSID7021948 EPA 531.1, EPA 531.2, ASTM
D5315-04, SM 6610 B.
Quinoline................................... 91-22-5 DTXSID1021798 EPA 530, EPA 538.
Tebuconazole................................ 107534-96-3 DTXSID9032113 EPA 525.3, EPA 540, EPA 543.
Terbufos.................................... 13071-79-9 DTXSID2022254 EPA 526.
Thiamethoxam................................ 153719-23-4 DTXSID2034962 In Development.
Tri-allate.................................. 2303-17-5 DTXSID5024344 Research Needed.
Tribufos.................................... 78-48-8 DTXSID1024174 EPA 525.3.
Tributyl phosphate.......................... 126-73-8 DTXSID3021986 Research Needed.
Trimethylbenzene (1,2,4-)................... 95-63-6 DTXSID6021402 EPA 502.2, EPA 524.2, EPA
524.3, EPA 524.4, ASTM D5790-
18, SM 6200 B, SM 6200 C.
Tris(2-chloroethyl) phosphate (TCEP)........ 115-96-8 DTXSID5021411 Research Needed.
Tungsten.................................... 7440-33-7 DTXSID8052481 Research Needed.
Vanadium.................................... 7440-62-2 DTXSID2040282 EPA 200.5, EPA 200.7, EPA
200.8, SM 3111 D, SM 3120 B,
SM 3500-V B.
----------------------------------------------------------------------------------------------------------------
\1\ Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts
Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic
compounds, polymers, elements, nuclear particles, etc.) in the open scientific literature. It contains up to
10 digits, separated by hyphens into three parts.
\2\ Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier
used in EPA's CompTox Chemicals database, where a substance can be any single chemical, mixture, or polymer.
\3\ Published methods are listed by EPA number or VCSB number. Methods in development by the EPA, or for which
research is still needed, are also identified.
\4\ EPA's approach to listing cyanotoxins, DBPs, and PFAS as groups on CCL 5 as opposed to listing them as
individual contaminants limits duplication of agency efforts, such as data gathering, analyses and
evaluations. Listing these three chemical groups on the CCL 5 does not necessarily mean that EPA will make
subsequent regulatory decisions for the entire group.
\5\ As defined in CCL 5, toxins naturally produced and released by some species of cyanobacteria (also known as
``blue-green algae''). The group of cyanotoxins includes, but is not limited to: anatoxin-a,
cylindrospermopsin, microcystins, and saxitoxin as shown in Exhibit 2.
\6\ This CCL 5 group includes 23 unregulated DBPs as shown in Exhibit 3.
\7\ The CCL 5 lists a general nonylphenol with a CASRN of 25154-52-3. EPA Method 559 analyzes nonylphenol with a
CASRN of 84852-15-3 and reports technical nonylphenol, comprised mostly of branched C9-alkyl phenols, and not
linear nonylphenol (CASRN 104-40-5) which is a laboratory generated chemical not typically found in the
environment.
\8\ The CCL 5 structural definition of per- and polyfluoroalkyl substances (PFAS) includes chemicals that
contain at least one of these three structures as shown in Exhibit 4 (except for PFOA and PFOS which are
already in the regulatory process):
1. R-(CF2)-CF(R')R'', where both the CF2 and CF moieties are saturated carbons, and none of the R groups can be
hydrogen.
2. R-CF2OCF2-R', where both the CF2 moieties are saturated carbons, and none of the R groups can be hydrogen.
3. CF3C(CF3)RR', where all the carbons are saturated, and none of the R groups can be hydrogen.
* EPA Method 527 indicates these specific contaminants may have potential complications.

The CCL 5 includes cyanotoxins as a group, including but not
limited to the contaminants in Exhibit 2. The EPA recognizes there are
other contaminants in this group such as, nodularin-R (which is not a
microcystin), as well as, derivatives and congeners of anatoxin-a,
cylindrospermopsin, and saxitoxin (e.g., homoanatoxin-a, deoxy-
cylindrospermopsin, and other paralytic shellfish poisons).

Exhibit 2--Unregulated Cyanotoxins Group on CCL 5 and Associated Drinking Water Analytical Methods
[See Exhibit 1 footnote 4]
----------------------------------------------------------------------------------------------------------------
Chemical name CASRN \1\ DTXSID \2\ Drinking water method(s) \3\
----------------------------------------------------------------------------------------------------------------
Anatoxin-a.................................. 64285-06-9 DTXSID50867064 EPA 545.
Cylindrospermopsin.......................... 143545-90-8 DTXSID2031083 EPA 545.
Saxitoxin................................... 35523-89-8 DTXSID3074313 Research Needed.
----------------------------------------------------------------------------------------------------------------
Microcystins
----------------------------------------------------------------------------------------------------------------
Microcystin LA.............................. 96180-79-9 DTXSID3031656 EPA 544.
Microcystin LR.............................. 101043-37-2 DTXSID3031654 EPA 544.
Microcystin LW.............................. 157622-02-1 DTXSID70891285 Research Needed.
Microcystin RR.............................. 111755-37-4 DTXSID40880085 EPA 544.

[[Page 8589]]

Microcystin YR.............................. 101064-48-6 DTXSID00880086 EPA 544.
----------------------------------------------------------------------------------------------------------------
\1\ Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts
Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic
compounds, polymers, elements, nuclear particles, etc.) in the open scientific literature. It contains up to
10 digits, separated by hyphens into three parts.
\2\ Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier
used in EPA's CompTox Chemicals database, where a substance can be any single chemical, mixture, or polymer.
\3\ Published methods are listed by EPA number or VCSB number. Methods in development by the EPA, or for which
research is still needed, are also identified.

Exhibit 3--Unregulated DBP Group on CCL 5 and Associated Drinking Water Analytical Methods
[See Exhibit 1 footnote 5]
----------------------------------------------------------------------------------------------------------------
Chemical name CASRN \1\ DTXSID \2\ Drinking water method(s) \3\
----------------------------------------------------------------------------------------------------------------
Haloacetic Acids
----------------------------------------------------------------------------------------------------------------
Bromochloroacetic acid (BCAA)............... 5589-96-8 DTXSID4024642 EPA 552.1, EPA 552.2, EPA
552.3, EPA 557, SM 6251 B.
Bromodichloroacetic acid (BDCAA)............ 71133-14-7 DTXSID4024644 EPA 552.2, EPA 552.3, EPA 557.
Dibromochloroacetic acid (DBCAA)............ 5278-95-5 DTXSID3031151 EPA 552.2, EPA 552.3, EPA 557.
Tribromoacetic acid (TBAA).................. 75-96-7 DTXSID6021668 EPA 552.2, EPA 552.3, EPA 557.
----------------------------------------------------------------------------------------------------------------
Haloacetonitriles
----------------------------------------------------------------------------------------------------------------
Dichloroacetonitrile (DCAN)................. 3018-12-0 DTXSID3021562 EPA 551.1.
Dibromoacetonitrile (DBAN).................. 3252-43-5 DTXSID3024940 EPA 551.1.
----------------------------------------------------------------------------------------------------------------
Halonitromethanes
----------------------------------------------------------------------------------------------------------------
Bromodichloronitromethane (BDCNM)........... 918-01-4 DTXSID4021509 Research Needed.
Chloropicrin (trichloronitromethane, TCNM).. 76-06-2 DTXSID0020315 EPA 551.1.
Dibromochloronitromethane (DBCNM)........... 1184-89-0 DTXSID00152114 Research Needed.
----------------------------------------------------------------------------------------------------------------
Iodinated Trihalomethanes
----------------------------------------------------------------------------------------------------------------
Bromochloroiodomethane (BCIM)............... 34970-00-8 DTXSID9021502 Research Needed.
Bromodiiodomethane (BDIM)................... 557-95-9 DTXSID70204235 Research Needed.
Chlorodiiodomethane (CDIM).................. 638-73-3 DTXSID20213251 Research Needed.
Dibromoiodomethane (DBIM)................... 593-94-2 DTXSID60208040 Research Needed.
Dichloroiodomethane (DCIM).................. 594-04-7 DTXSID7021570 Research Needed.
Iodoform (triiodomethane, TIM).............. 75-47-8 DTXSID4020743 Research Needed.
----------------------------------------------------------------------------------------------------------------
Nitrosamines
----------------------------------------------------------------------------------------------------------------
Nitrosodibutylamine (NDBA).................. 924-16-3 DTXSID2021026 EPA 521, SM 6450 B, SM 6450 C.
N-Nitrosodiethylamine (NDEA)................ 55-18-5 DTXSID2021028 EPA 521, SM 6450 B, SM 6450 C.
N-Nitrosodimethylamine (NDMA)............... 62-75-9 DTXSID7021029 EPA 521, SM 6450 B, SM 6450 C.
N-Nitrosodi-n-propylamine (NDPA)............ 621-64-7 DTXSID6021032 EPA 521, SM 6450 B, SM 6450 C.
N-Nitrosodiphenylamine (NDPhA).............. 86-30-6 DTXSID6021030 Research Needed.
Nitrosopyrrolidine (NPYR)................... 930-55-2 DTXSID8021062 EPA 521, SM 6450 B, SM 6450 C.
----------------------------------------------------------------------------------------------------------------
Others
----------------------------------------------------------------------------------------------------------------
Chlorate.................................... 14866-68-3 DTXSID3073137 EPA 300.1, ASTM D6581-18, SM
4110 D.
Formaldehyde................................ 50-00-0 DTXSID7020637 EPA 554, EPA 556.1, SM 6252 B.*
----------------------------------------------------------------------------------------------------------------
\1\ Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts
Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic
compounds, polymers, elements, nuclear particles, etc.) in the open scientific literature. It contains up to
10 digits, separated by hyphens into three parts.
\2\ Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier
used in EPA's CompTox Chemicals database, where a substance can be any single chemical, mixture, or polymer.
\3\ Published methods are listed by EPA number or VCSB number. Methods in development by the EPA, or for which
research is still needed, are also identified.
* SM 6252 B is in the 24th edition of SM titled as proposed.

The CCL 5 included PFAS as a group which includes thousands of PFAS
chemicals per the CCL 5 structural definition (USEPA, 2022b). Exhibit 4
lists the PFAS that EPA has available drinking water analytical
methods. The

[[Page 8590]]

EPA recognizes that the PFAS in Exhibit 4 only captures a subset of the
thousands of PFAS compounds encompassed in the CCL 5 structural
definition (USEPA, 2023).

Exhibit 4--Unregulated PFAS Group With Available Drinking Water Analytical Methods
[See Exhibit 1 footnote 7]
----------------------------------------------------------------------------------------------------------------
Chemical name \1\ CASRN \2\ DTXSID \3\ Drinking water method(s) \4\
----------------------------------------------------------------------------------------------------------------
11-chloroeicosafluoro-3-oxaundecane-1- 763051-92-9 DTXSID40892507 EPA 533, EPA 537.1.
sulfonic acid (11Cl-PF3OUdS).
9-chlorohexadecafluoro-3-oxanonane-1- 756426-58-1 DTXSID80892506 EPA 533, EPA 537.1.
sulfonic acid (9Cl-PF3ONS).
4,8-dioxa-3H-perfluorononanoic acid 919005-14-4 DTXSID40881350 EPA 533, EPA 537.1.
(ADONA).
Hexafluoropropylene oxide dimer acid 13252-13-6 DTXSID70880215 EPA 533, EPA 537.1.
(HFPO-DA).
Nonafluoro-3,6-dioxaheptanoic acid 151772-58-6 DTXSID30382063 EPA 533.
(NFDHA).
Perfluorobutanoic acid (PFBA)........ 375-22-4 DTXSID4059916 EPA 533.
Perfluorobutanesulfonic acid (PFBS).. 375-73-5 DTXSID5030030 EPA 533, EPA 537.1.
1H,1H, 2H, 2H-perfluorodecane 39108-34-4 DTXSID00192353 EPA 533.
sulfonic acid (8:2FTS).
Perfluorodecanoic acid (PFDA)........ 335-76-2 DTXSID3031860 EPA 533, EPA 537.1.
Perfluorododecanoic acid (PFDoA)..... 307-55-1 DTXSID8031861 EPA 533, EPA 537.1.
Perfluoro(2-ethoxyethane)sulfonic 113507-82-7 DTXSID50379814 EPA 533.
acid (PFEESA).
Perfluoroheptanesulfonic acid (PFHpS) 375-92-8 DTXSID8059920 EPA 533.
Perfluoroheptanoic acid (PFHpA)...... 375-85-9 DTXSID1037303 EPA 533, EPA 537.1.
1H,1H, 2H, 2H-perfluorohexane 757124-72-4 DTXSID30891564 EPA 533.
sulfonic acid (4:2FTS).
Perfluorohexanesulfonic acid (PFHxS). 355-46-4 DTXSID7040150 EPA 533, EPA 537.1.
Perfluorohexanoic acid (PFHxA)....... 307-24-4 DTXSID3031862 EPA 533, EPA 537.1.
Perfluoro-3-methoxypropanoic acid 377-73-1 DTXSID70191136 EPA 533.
(PFMPA).
Perfluoro-4-methoxybutanoic acid 863090-89-5 DTXSID60500450 EPA 533.
(PFMBA).
Perfluorononanoic acid (PFNA)........ 375-95-1 DTXSID8031863 EPA 533, EPA 537.1.
1H,1H, 2H, 2H-perfluorooctane 27619-97-2 DTXSID6067331 EPA 533.
sulfonic acid (6:2FTS).
Perfluorooctanesulfonic acid (PFOS).. 1763-23-1 DTXSID3031864 EPA 533, EPA 537.1.
Perfluorooctanoic acid (PFOA)........ 335-67-1 DTXSID8031865 EPA 533, EPA 537.1.
Perfluoropentanoic acid (PFPeA)...... 2706-90-3 DTXSID6062599 EPA 533.
Perfluoropentanesulfonic acid (PFPeS) 2706-91-4 DTXSID8062600 EPA 533.
Perfluoroundecanoic acid (PFUnA)..... 2058-94-8 DTXSID8047553 EPA 533, EPA 537.1.
N-ethyl 2991-50-6 DTXSID5062760 EPA 537.1.
perfluorooctanesulfonamidoacetic
acid (NEtFOSAA).
N-methyl 2355-31-9 DTXSID10624392 EPA 537.1.
perfluorooctanesulfonamidoacetic
acid (NMeFOSAA).
Perfluorotetradecanoic acid (PFTA)... 376-06-7 DTXSID3059921 EPA 537.1.
Perfluorotridecanoic acid (PFTrDA)... 72629-94-8 DTXSID90868151 EPA 537.1.
----------------------------------------------------------------------------------------------------------------
\1\ The CCL 5 structural definition of per- and polyfluoroalkyl substances (PFAS) includes chemicals that
contain at least one of these three structures as shown in Exhibit 4 (except for PFOA and PFOS which are
already in the regulatory process):
1. R-(CF2)-CF(R')R'', where both the CF2 and CF moieties are saturated carbons, and none of the R groups can be
hydrogen.
2. R-CF2OCF2-R', where both the CF2 moieties are saturated carbons, and none of the R groups can be hydrogen.
3. CF3C(CF3)RR', where all the carbons are saturated, and none of the R groups can be hydrogen.
\2\ Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts
Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic
compounds, polymers, elements, nuclear particles, etc.) in the open scientific literature. It contains up to
10 digits, separated by hyphens into three parts.
\3\ Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier
used in EPA's CompTox Chemicals database, where a substance can be any single chemical, mixture, or polymer.
\4\ Published methods are listed by EPA number or VCSB number. Methods in development by the EPA, or for which
research is still needed, are also identified.

Exhibit 5--Unregulated Microbial Contaminants on CCL 5 and Associated
Drinking Water Analytical Methods
------------------------------------------------------------------------
Type of Drinking water
Microorganism microorganism method(s) \1\
------------------------------------------------------------------------
Adenovirus...................... Virus............. Research Needed.
Caliciviruses................... Virus............. Research Needed.
Campylobacter jejuni............ Bacteria.......... Research Needed.
Escherichia coli (O157)......... Bacteria.......... Research Needed.
Enterovirus..................... Virus............. EPA 1615.
Helicobacter pylori............. Bacteria.......... Research Needed.
Legionella pneumophila.......... Bacteria.......... In Development,
ASTM D8429-21 *,
ISO 11731:2017,
ISO/TS
12869:2019.
Mycobacterium abscessus......... Bacteria.......... In Development.
Mycobacterium avium............. Bacteria.......... In Development.
Naegleria fowleri............... Protozoa.......... SM 9750.**
Pseudomonas aeruginosa.......... Bacteria.......... ASTM D5246-19, SM
9213 E, SM 9213
F, SM 9213 G.
Shigella sonnei................. Bacteria.......... Research Needed.
------------------------------------------------------------------------
\1\ Published methods are listed by EPA number or VCSB number. Methods
in development by the EPA, or for which research is still needed, are
also identified.
* Commonly known as Legiolert[supreg] test.
** SM 9750 is in the 24th edition of SM titled as proposed.

[[Page 8591]]

B. What drinking water analytical methods are being developed by the
EPA to address contaminants on CCL 5?

1. Draft EPA Method(s) for PFAS.
The agency continues to conduct research and monitor advances and
techniques that may improve our ability to measure PFAS. Preliminary
studies have been performed looking at potential method development for
PFAS contaminants that are not analyzed in EPA Methods 533 or 537.1.
The EPA Methods 533 and 537.1 both address a wide variety of PFAS.
These methods were developed focusing on the largest array of PFAS that
were commercially available at the time (as certified reference
standards) and that could be analyzed while routinely meeting all
method-specified quality control criteria (towards the goal of
generating accurate and precise results in drinking water sample
matrices). EPA is working to expand the method target analyte scope and
is soliciting comment and supporting performance data from stakeholders
that have conducted similar studies (e.g., incorporating PFAS with
carbon chains less than or equal to three carbons and/or improvements
in analytical processing times, such as employing direct injection
techniques that could simplify or eliminate the solid-phase extraction
step (USEPA, 2019b). EPA anticipates that such improvements would
enhance laboratory capability and capacity. EPA invites comments on
analytical improvements to Methods 533 and 537.1 or alternative
techniques that could prove to be effective at measuring PFAS in
drinking water.
2. Draft EPA Method 562--Determination of selected pesticides in
drinking water by solid phase extraction and liquid chromatography/
tandem mass spectrometry (LC/MS/MS).
The target contaminants for this method consist of the seven
pesticides and three degradates shown in Exhibit 6.

Exhibit 6--Target Contaminants in Draft EPA Method 562
----------------------------------------------------------------------------------------------------------------
Chemical name CASRN \1\ DTXSID \2\
----------------------------------------------------------------------------------------------------------------
Bromoxynil.................................................... 1689-84-5 DTXSID3022162.
Carbendazim (MBC)............................................. 10605-21-7 DTXSID4024729
Chlordecone (Kepone).......................................... 143-50-0 DTXSID1020770
Clothianidin.................................................. 210880-92-5 DTXSID2034465
Fipronil...................................................... 120068-37-3 DTXSID4034609
Fipronil sulfide.............................................. 120067-83-6 DTXSID50869644
Fipronil sulfone.............................................. 120068-36-2 DTXSID6074750
Flufenacet.................................................... 142459-58-3 DTXSID2032552
Iprodione..................................................... 36734-19-7 DTXSID3024154
Thiamethoxam.................................................. 153719-23-4 DTXSID2034962
----------------------------------------------------------------------------------------------------------------
\1\ Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts
Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic
compounds, polymers, elements, nuclear particles, etc.) in the open scientific literature. It contains up to
10 digits, separated by hyphens into three parts.
\2\ Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier
used in EPA's CompTox Chemicals database, where a substance can be any single chemical, mixture, or polymer.

The aqueous samples are preserved with ascorbic acid to mitigate
free chlorine disinfection and sodium bisulfate to inhibit microbial
growth. Extraction efficiency is monitored by adding surrogate
compounds to the aqueous samples prior to extraction. Chlordecone and
iprodione are known to degrade in the presence of methanol (Bichon et
al., 2015; Anisuzzaman et al., 2008); therefore, efforts to avoid the
use of methanol were prioritized. Preliminary holding time studies
support an aqueous holding time of 14 days and an extract holding time
of 28 days. Solid phase extraction (SPE) using divinylbenzene sorbent
is used to concentrate the contaminants from the aqueous sample.
Additional research may be performed which may allow use of other SPE
sorbents provided performance requirements are met. The samples are
fully loaded onto the SPE cartridge, followed by a deionized (DI) water
bottle wash then an acetone bottle wash to elute the target
contaminants. Following elution, nitrogen evaporation is used to reduce
the extract. The extract is brought to final volume with an acetone and
acetonitrile mixture. The target contaminants are separated using
reversed phase liquid chromatography and detected using LC/MS/MS using
both positive and negative electrospray ionization. Selected reaction
monitoring is used to detect a product ion to maximize selectivity.
Instrument variability is corrected using an internal standard.
The EPA invites comments to support development of this pesticide
method. The agency is particularly interested in comments about
additional SPE sorbents that provide contaminant recovery meeting the
drinking water program's data quality objectives.
3. Draft EPA Method Purgeable Organics--Measurement of purgeable
organic compounds in water by capillary column gas chromatography/mass
spectrometry (GC/MS).
This method is expected to support the analysis of drinking water
for 1,2,3-trichloropropane (TCP) and other purgeable organic compounds.
The target contaminants for this method are shown in Exhibit 7.

Exhibit 7--Target Contaminants in Draft EPA Method Purgeable Organics
----------------------------------------------------------------------------------------------------------------
Chemical name CASRN \1\ DTXSID \2\
----------------------------------------------------------------------------------------------------------------
1,2-dibromo-3-chloropropane................................... 96-12-8 DTXSID3020413
1,2-dibromoethane............................................. 106-93-4 DTXSID3020415
1,2,3-trichloropropane........................................ 96-18-4 DTXSID9021390
1,2,4-trimethylbenzene........................................ 95-63-6 DTXSID6021402

[[Page 8592]]

Methyl-tert-butyl Ether....................................... 1634-04-4 DTXSID3020833
----------------------------------------------------------------------------------------------------------------
\1\ Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts
Service (a division of the American Chemical Society) to every chemical substance (organic and inorganic
compounds, polymers, elements, nuclear particles, etc.) in the open scientific literature. It contains up to
10 digits, separated by hyphens into three parts.
\2\ Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier
used in EPA's CompTox Chemicals database, where a substance can be any single chemical, mixture, or polymer.

EPA Methods 524.2, 524.3, and 524.4 are used to analyze a variety
of organic compounds; however, this method in development is targeting
the selected contaminants in Exhibit 9 at quantifiable levels lower
than the EPA Methods 524.3 and 524.4 currently achieve (USEPA, 1995g;
USEPA, 2009a; USEPA, 2013a). In the draft method, headspace-free
samples are collected in amber glass vials with polytetrafluoroethylene
(PTFE)-faced septa. Samples are dechlorinated with ascorbic acid and
the pH is adjusted with maleic acid. A 5.0 milliliter (mL) or 25-mL
aliquot of the sample is transferred to a glass sparging vessel along
with appropriate amounts of internal standard and QC compounds. The
method contaminants are purged from the water using helium or nitrogen
and trapped on a sorbent material. The sample is then heated and
backflushed with gas chromatography (GC) carrier gas to transfer the
contaminants directly into the gas chromatographic inlet. The inlet is
operated in the split mode to achieve the desired desorb flow rates and
further reduce water transmission. Contaminants are transferred onto a
capillary GC column, which is temperature programmed to optimize the
separation of method contaminants. Compounds eluting from the GC are
directed into a mass spectrometer for detection and quantitation. The
method contaminants are identified by comparing the acquired mass
spectra and retention times to reference spectra and retention times.
The concentration of each contaminant is calculated using the internal
standard technique and response curves obtained via procedural
calibration.
The draft method may differ from EPA Methods 524.2, 524.3, and
524.4 due to removing the requirement for a 4-bromofluorobenzene (BFB)
tune as part of the GC/MS optimization and initial calibration, and
instead optimizing tuning to maximum ion transmission for the target
contaminants of interest. EPA Methods 524.2, 524.3, and 524.4 require a
BFB tune, and the draft method will allow optimizing tuning to maximum
ion transmission for the target analytes in Exhibit 7. By optimizing
conditions specifically for the target contaminants of interest, lower
quantitation limits may be achieved. Other changes, such as adjusting
the GC split ratio would also be optimized to focus on the specific set
of contaminants listed in Exhibit 7.
The EPA invites comments to support development of this method. The
agency is particularly interested in techniques to quantify 1,2,3-TCP
at low levels (~5 nanograms per liter (ng/L)).
4. Draft EPA Method Legionella--Legionella spp. and Legionella
pneumophila quantitative polymerase chain reaction (qPCR) detection.
The target contaminants for this method are shown in Exhibit 8.

Exhibit 8--Target Contaminants in Draft EPA Method Legionella
----------------------------------------------------------------------------------------------------------------
Microorganism Type of microorganism
----------------------------------------------------------------------------------------------------------------
Legionella species (Leg16S)................................ Bacteria.
Legionella pneumophila (MIP)............................... Bacteria.
Legionella pneumophila (Lp16S)............................. Bacteria.
----------------------------------------------------------------------------------------------------------------

For this method in development, one assay under consideration will
detect all Legionella species (there are ~53 recognized species). There
are two other assays under consideration for Legionella pneumophila
detection. For this method, a one-liter sample is collected in a high-
density polypropylene bottle containing sodium thiosulfate for
dechlorination. The sample is vacuumed filtered through a 0.45
micrometer ([micro]m) polycarbonate membrane. The captured microbial
deoxyribonucleic acid (DNA) is extracted from the membrane. The
extracted DNA is analyzed using three qPCR assays utilizing a qPCR
instrument.
This method will detect and quantify the targeted microbe of
interest. The method identifies the target bacteria using primer-probe
specific to the microbe of interest, and the resulting qPCR gene
product (DNA sequence) molecular weight is checked. The instrument will
generate an amplification curve if the targeted bacteria is present in
a sample. As the curve passes the 0.4 threshold, a quantification cycle
(Cq) value is determined. The targeted bacteria DNA (Cq value) is then
quantified using a standard curve generated from genomic DNA. The
method contains other QC samples, including, positive controls such as,
the standard curve and negative controls, such as, internal controls,
method blanks, extraction blanks, and non-template controls.
The EPA invites comments to support the development of a Legionella
spp. and Legionella pneumophila method. The agency is specifically
interested in information on environmental laboratory capabilities to
perform this method.
5. Draft EPA Method Mycobacterium--Mycobacterium abscessus culture
recovery with matrix-assisted laser desorption/ionization mass
spectrometry (MALDI-MS).
The target contaminants for this method are shown in Exhibit 9.

[[Page 8593]]

Exhibit 9--Target Contaminants in Draft EPA Method Mycobacterium
----------------------------------------------------------------------------------------------------------------
Microorganism Type of microorganism
----------------------------------------------------------------------------------------------------------------
Mycobacterium abscessus.................................... Bacteria.
Mycobacterium mucogenicum (potentially).................... Bacteria.
----------------------------------------------------------------------------------------------------------------

This method is in early development. A one-liter sample is
collected in a high-density polypropylene bottle containing sodium
thiosulfate for dechlorination. The sample is decontaminated for 30
minutes with 0.4% cetylpyridinium chloride solution. Then, 500 mL of
the decontaminated sample is vacuumed filtered through a 0.45 mm black,
mixed cellulose membrane. The membrane with the captured bacteria is
laid on top of Middlebrook 7H11 agar plate. The plate is incubated at
37 [deg]C for 7 days. The resulting colonies are chosen for matrix-
assisted laser desorption/ionization mass spectrometry (MALDI-MS)
identification.
The EPA invites comments to support development of this method. The
agency is particularly interested in the following: (1) suggestions for
preservation chemical to use; (2) input on detection limits using
MALDI-MS; (3) input on the sample volume needed; and (4) feedback
regarding any experience with this technique.
6. Draft EPA Method Mycobacterium qPCR--Mycobacterium avium and
Mycobacterium intracellulare quantitative polymerase chain reaction
(qPCR) detection.
The target contaminants for this method are shown in Exhibit 10.

Exhibit 10--Target Contaminants in Draft EPA Method Mycobacterium QPCR
----------------------------------------------------------------------------------------------------------------
Microorganism Type of microorganism
----------------------------------------------------------------------------------------------------------------
Mycobacterium avium........................................ Bacteria.
Mycobacterium intracellulare............................... Bacteria.
----------------------------------------------------------------------------------------------------------------

This method can distinguish between Mycobacterium avium and
Mycobacterium intracellulare species. For this method, a one-liter
sample is collected in a high-density polypropylene bottle containing
sodium thiosulfate for dechlorination. The sample is vacuum-filtered
through a 0.45 [micro]m polycarbonate membrane. The captured microbial
DNA is extracted from the membrane. The extracted DNA is analyzed using
two qPCR assays utilizing a qPCR instrument.
This method will detect and quantify the targeted microbe of
interest. The method identifies the target bacteria using primer-probe
specific to the microbe of interest, and the resulting qPCR gene
product (DNA sequence) molecular weight is checked. The instrument will
generate an amplification curve if the targeted bacteria is present in
a sample. As the curve passes the 0.4 threshold, a Cq value is
determined. The targeted bacteria DNA (Cq value) is then quantified
using a standard curve generated from genomic DNA. The method contains
other QC samples, including positive controls such as the standard
curve, and negative controls such as internal controls, method blanks,
extraction blanks, and non-template controls. This method requires the
collection of a 200 mL water sample.
The EPA invites comments to support development of this method. The
agency is particularly interested in information on environmental
laboratory capabilities to perform this method.

C. What other drinking water analytical methods are being considered by
the EPA to address emerging contaminants?

1. Draft EPA Method EOF--Screening method for the determination of
extractable organic fluorine (EOF) in drinking water by anion exchange
solid phase extraction and combustion ion chromatography (CIC).
The target contaminant for this method is Extractable Organic
Fluorine (EOF). Targeted PFAS drinking water methods currently only
capture a small subset of the many PFAS known to exist. ``Aggregate''
methods (sometimes referred to as a ``total PFAS'' method) are designed
to capture a larger portion of the PFAS than targeted methods are able
to detect. The subject technique seeks to estimate the concentration of
EOF in drinking water. It captures organofluorine compounds from PFAS
and non-PFAS fluorinated substances that are retained using weak anion
exchange SPE. The method has potential application for screening,
recognizing that it will not measure fluorinated compounds
individually, but as an aggregate sum of the fluorinated compounds
captured on the sorbent. Notably, non-PFAS fluorinated compounds may
also be accounted for in the reported value along with residual
inorganic fluoride that is added to drinking water to prevent tooth
decay.
For this EOF method in development by the EPA, the preservation
scheme follows EPA Method 533, with the aqueous samples preserved with
ammonium acetate to sequester free chlorine to form chloramine.
Additionally, the EOF method follows the EPA Method 533 holding time
scheme set at 28 days.
The drinking water sample is concentrated using weak anion-exchange
SPE. After passing the sample through the SPE cartridge, preserved
reagent water is pulled through the cartridge, then aqueous ammonium
hydroxide is used to wash the SPE cartridge to remove inorganic
fluoride. A solution of ammonium hydroxide in methanol is used to elute
the adsorbed compounds. The extract is evaporated to dryness and
reconstituted in a methanol and water mixture. The entire extract is
transferred to a ceramic boat and combusted at high temperature in the
furnace of a combustion ion chromatography (CIC) instrument to break
the carbon-fluorine bond. The released fluorine is absorbed in a water
solution to form the fluoride ion. A portion of the fluoride solution
is separated by ion chromatography using a potassium hydroxide-based
eluent. External calibration is used to establish the retention time
for fluoride and report the extractable organic fluorine as fluoride.
The agency notes that aggregate techniques considered to-date do not
have the same sensitivity as targeted techniques. The quantitation
capabilities of the EOF technique, and the suitability of the technique
for drinking water monitoring, continue to be evaluated.
The agency considered other aggregate methods, including an

[[Page 8594]]

adsorbable organic fluorine (AOF) procedure, such as draft EPA Method
1621 (USEPA, 2022a). In the AOF method, larger samples achieve better
sensitivity. The agency notes that draft EPA Method 1621 does not
retain short carbon PFAS within the data quality objective limits of
70-130%. In addition, draft EPA Method 1621 does not permit rinsing of
the sample container, meaning hydrophobic PFAS may be lost to
adsorption on the sample container. A method wash step removes
inorganic fluoride up to 95%, but a trace amount of inorganic fluoride
may remain because of the weak anion exchange sorbent.
The EPA invites comments to support development and consideration
of aggregate PFAS measurement. The agency is particularly interested in
the following: (1) techniques to extract or adsorb ultra short chain
PFAS; (2) alternative ways to remove inorganic fluoride from aqueous
drinking water samples prior to or during the extraction or adsorption
for organic fluoride; (3) techniques to capture anionic, neutral and
cationic PFAS in a single solid phase extraction procedure; and (4)
techniques to improve the selectivity of the extraction process to
reduce or eliminate retention of non-PFAS fluorinated compounds.
2. Draft EPA Method Microplastics--Analysis of microplastics in
drinking water using spectroscopic instrumentation.
The target contaminant for this method is ``microplastics.'' Common
spectroscopic libraries contain spectra for thousands of different
polymers that can all be identified using these instruments. For this
discussion, EPA's water research definition of microplastics is
particles ranging in size from 5 millimeters (mm) to 1 mm at <a href="https://www.epa.gov/water-research/microplastics-research">https://www.epa.gov/water-research/microplastics-research</a>.
The agency is in the early stages of developing a microplastics
method and is gathering information about analytical approaches. The
agency recognizes that voluntary consensus standards bodies (VCSBs)
methods ASTM D8332-20 and ASTM D8333-20 are available. This section
summarizes the currently available research. In developing the final
method approach, the agency will seek to incorporate the latest
advancements in microplastic research and analytical methodologies.
There are a variety of spectroscopic techniques that can be
utilized for microplastic analysis, including fourier transform
infrared (FTIR) spectroscopy, laser direct infrared (LDIR)
spectroscopy, and Raman spectroscopy. The analytical instruments
associated with these techniques have more similarities than
differences and all provide similar information to characterize
microplastics, including size, shape, and polymer type of individual
microplastics.
For all of the spectroscopy techniques examined by the agency,
samples are stored at 4 degrees Celsius (Wong and Coffin, 2022) or have
a maximum of one freeze and thaw cycle (ITRC, 2023). Depending on the
requirements and capabilities of the analytical instrument, a variety
of instrument filter types with different coatings and pore sizes have
been used to collect microplastics from aqueous samples. For example,
the LDIR imaging system uses gold-coated filters that are infrared-
reflective. The California State Water Resources Control Board does not
recommend density separation or digestion for drinking water samples
(Wong and Coffin, 2022).
Spectroscopic methods only quantify the number of particles, not a
mass of polymer, and can identify even a single particle on a filter,
so the measurement capability is only related to the size of the
particle. Many infrared and Raman-based instruments can identify
particles with a minimum diameter of 20 microns and 1-micron,
respectively. However, the minimum size for reliable identification on
the widest range of instrument models should be considered as 50
microns for infrared-based instruments and 20 microns for Raman-based
instruments. (Wong and Coffin, 2022).
The EPA invites comments to support the development of a
microplastics method. The agency is specifically interested in comments
that will help identify the changes to microplastics that happen as a
result of reactions to environmental exposures (i.e., sunlight, water,
and temperature) and how these changes can affect reliable polymer
identification.

D. What information should the public provide when submitting comments
about drinking water analytical methods for CCL 5 and other emerging
contaminants?

The EPA welcomes comments from the public regarding analytical
methods for measuring emerging contaminants in drinking water. This
includes methods already published by the agency or others, those under
development by the agency or others, and those that should be
considered for future development. The agency is particularly
interested in methods that may be used to monitor drinking water for
the contaminants published on final the CCL 5 (87 FR 68060, November
14, 2022 (USEPA, 2022b)). The agency encourages commenters to include
their name, affiliation, phone number, mailing address, and email
address. However, this information is not required, and comments can be
submitted anonymously. When addressing non-EPA or voluntary consensus
standards bodies (VCSBs) methods, comments should address the
following, as applicable:
1. Specify the method name and describe, at least generally, the
instrumentation upon which it relies.
2. Specify the status of the method (e.g., fully-developed, nearing
completion, early development).
3. Specify the emerging contaminant(s), particularly the CCL
contaminants, that can be analyzed with the drinking water analytical
method. CCL 5 contaminants are listed in Exhibits 1-5 of this notice
and at <a href="https://www.federalregister.gov/documents/2022/11/14/2022-23963/drinking-water-contaminant-candidate-list-5-final">https://www.federalregister.gov/documents/2022/11/14/2022-23963/drinking-water-contaminant-candidate-list-5-final</a>.
4. Specify method performance information, such as sensitivity,
selectivity, accuracy, and precision attainable for the contaminant(s).
Describe the degree to which the method performance has been validated;
the latter is important for any method being considered by the EPA for
UCMR or other purposes. Guidelines for analytical method validation are
described by the EPA Forum on Environmental Measurement (FEM) in
documents available through the FEM website (USEPA, 2016b, c) at
<a href="https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines">https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines</a>.
5. To the extent possible, specify the cost, availability, and your
laboratory's capacity to run the method commercially.
6. Provide complete citations for referenced analytical methods,
including author(s), title, journal (or other publication), and date.
7. Provide contact information for the principal investigator, when
available.

IV. References

(i) Anisuzzaman, A., Storehalder, T., Williams, D., Ogg, N.,
Kilbourne, T., John Samuel, J., & Cottrell, C. 2008. Effect of
Alcohols on the Stability of Iprodione in Solution. Journal of
Agricultural and Food Chemiemergingstry, 56 (2), 502-506. DOI:
10.1021/jf0720483.
(ii) ASTM. 2015. ASTM D3558-15--Standard Test Methods for Cobalt in
Water. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
Approved February 1, 2015. Available for purchase at <a href="http://astm.org">astm.org</a>.
(iii) ASTM. 2017a. ASTM D5175-91--Standard Test Method for
Organohalide

[[Page 8595]]

Pesticides and Polychlorinated Biphenyls in Water by Microextraction
and Gas Chromatography. ASTM, 100 Barr Harbor Drive, West
Conshohocken, PA 19428. Approved December 15, 2017. Available for
purchase at <a href="http://astm.org">astm.org</a>.
(iv) ASTM. 2017b. ASTM D5315-04--Standard Test Method for
Determination of N-Methyl-Carbamoyloximes and N-Methylcarbamates in
Water by Direct Aqueous Injection HPLC with Post-Column
Derivatization. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA
19428. Approved December 15, 2017. Available for purchase at
<a href="http://astm.org">astm.org</a>.
(v) ASTM. 2018a. ASTM D6581-18--Standard Test Methods for Bromate,
Bromide, Chlorate, and Chlorite in Drinking Water by Suppressed Ion
Chromatography. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA
19428. Approved May 1, 2018. Available for purchase at <a href="http://astm.org">astm.org</a>.
(vi) ASTM. 2018b. ASTM D5790-18--Standard Test Method for
Measurement of Purgeable Organic Compounds in Water by Capillary
Column Gas Chromatography/Mass Spectrometry. ASTM, 100 Barr Harbor
Drive, West Conshohocken, PA 19428. Approved December 15, 2018.
Available for purchase at <a href="http://astm.org">astm.org</a>.
(vii) ASTM. 2019. ASTM D5246-19--Standard Test Method for Isolation
and Enumeration of Pseudomonas aeruginosa from Water. ASTM, 100 Barr
Harbor Drive, West Conshohocken, PA 19428. Approved December 1,
2019. Available for purchase at <a href="http://astm.org">astm.org</a>.
(viii) ASTM. 2020a. ASTM D1976-20--Standard Test Method for Elements
in Water by Inductively Coupled Plasma Atomic Emission Spectroscopy.
ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428. Approved
May 1, 2020. Available for purchase at <a href="http://astm.org">astm.org</a>.
(ix) ASTM. 2020b. ASTM D8332-20-- Standard Practice for Collection
of Water Samples with High, Medium, or Low Suspended Solids for
Identification and Quantification of Microplastic Particles and
Fibers. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
Approved July 15, 2020. Available for purchase at <a href="http://astm.org">astm.org</a>.
(x) ASTM. 2020c. ASTM D8333-20-- Standard Practice for Collection of
Water Samples with High, Medium, or Low Suspended Solids for
Identification and Quantification of Microplastic Particles and
Fibers Using Ramen Spectroscopy, IR Spectroscopy, or Pyrolysis-GC/
MS. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
Approved July 15, 2020. Available for purchase at <a href="http://astm.org">astm.org</a>.
(xi) ASTM. 2021. ASTM D8429-21--Standard Test Method for Legionella
pneumophila in Water Samples Using Legiolert. ASTM, 100 Barr Harbor
Drive, West Conshohocken, PA 19428. Approved 2021. Available for
purchase at <a href="http://astm.org">astm.org</a>.
(xii) ASTM. 2023. ASTM D7645-23--Standard Test Method for
Determination of Aldicarb, Aldicarb Sulfone, Aldicarb Sulfoxide,
Carbofuran, Methomyl, Oxamyl, and Thiofanox in Water by Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS). ASTM, 100 Barr
Harbor Drive, West Conshohocken, PA 19428. Approved April 15, 2023.
Available for purchase at <a href="http://astm.org">astm.org</a>.
(xiii) Bichon, E., Guiffard, I., V[eacute]nisseau, A., Marchand, P.,
Antignac, J.P., & Le Bizec, B. 2015. Ultra-trace quantification
method for chlordecone in human fluids and tissues. Journal of
Chromatography A, 1408, 169-177. <a href="http://DOI.org/10.1016/j.chroma.2015.07.013">DOI.org/10.1016/j.chroma.2015.07.013</a>.
(xiv) ISO Online. 2017. 11731:2017--Water Quality--Enumeration of
Legionella. ISO Standards. Available for purchase at <a href="https://www.iso.org/standards.html">https://www.iso.org/standards.html</a>.
(xv) ISO Online. 2019. 12869:2019--Water quality--Detection and
quantification of Legionella spp. and/or Legionella pneumophila by
concentration and genic amplification by quantitative polymerase
chain reaction (qPCR). ISO Standards. Available for purchase at
<a href="https://www.iso.org/standards.html">https://www.iso.org/standards.html</a>.
(xvi) Interstate Technology Regulatory Council (ITRC). 2023.
Microplastics Outreach Toolkit--Sampling and Analysis. February
2023. Available at <a href="https://mp-1.itrcweb.org/sampling-and-analysis/">https://mp-1.itrcweb.org/sampling-and-analysis/</a>.
(xvii) SM Online. 1997a. 3500-V--Vanadium (Editorial Revisions,
2020). Standard Methods Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xviii) SM Online. 1997b. 6200--Volatile Organic Compounds Method
(Editorial Revisions, 2011 and 2020). Standard Methods Online.
Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xix) SM Online. 1999a. 3111--Metals by Flame Atomic Absorption
Spectrometry Method (Editorial Revisions, 2019). Standard Methods
Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xx) SM Online. 1999b. 3120--Metals by Plasma Emission Spectroscopy
Method (Editorial Revisions, 2020). Standard Methods Online.
Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxi) SM Online. 1999c. 3500-Mn--Manganese (Editorial Revisions,
2020). Standard Methods Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxii) SM Online. 2000a. 4110--Determination of Anions by Ion
Chromatography Method (Editorial Revisions, 2020). Standard Methods
Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxiii) SM Online. 2000b. 4500-B--Boron (Editorial Revisions, 2020).
Standard Methods Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxiv) SM Online. 2004a. 3500-Li--Lithium (Editorial Revisions,
2020). Standard Methods Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxv) SM Online. 2004b. 6610--Carbamate Pesticides Method (Editorial
Revisions, 2021). Standard Methods Online. Available for purchase at
<a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxvi) SM Online. 2005. 6252--Disinfection Byproducts: Aldehydes
Method (Proposed) (Editorial Revisions, 2020). Standard Methods
Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxvii) SM Online. 2007a. 6251--Disinfection Byproducts: Haloacetic
Acids and Trichlorophenol Method (Editorial Revisions, 2020).
Standard Methods Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxviii) SM Online. 2007b. 6450--Nitrosamines Method (Editorial
Revisions, 2021). Standard Methods Online. Available for purchase at
<a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxix) SM Online. 2007c. 9213--Recreational Waters (Editorial
Revisions, 2022). Standard Methods Online. Available for purchase at
<a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxx) SM Online. 2010. 3113--Metals by Electrothermal Atomic
Absorption Spectrometry Method (Editorial Revisions, 2020). Standard
Methods Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxxi) SM Online. 2013. 6810--Pharmaceuticals and Personal Care
Products Method (Editorial Revisions, 2021). Standard Methods
Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxxii) SM Online. 2021. 9750--Detection of Naegleria fowleri in
Water. Standard Methods Online. Available for purchase at <a href="http://www.standardmethods.org">http://www.standardmethods.org</a>.
(xxxiii) USEPA. 1992a. Method 552.1--Determination of Haloacetic
Acids and Dalapon in Drinking Water by Ion-Exchange Liquid-Solid
Extraction and Gas Chromatography with an Electron Capture Detector.
Revision 1.0. Office of Research and Development, Cincinnati, OH.
August 1992. Available at <a href="https://www.nemi.gov/methods/method_summary/4784/">https://www.nemi.gov/methods/method_summary/4784/</a>.
(xxxiv) USEPA. 1992b. Method 554--Determination of Carbonyl
Compounds in Drinking Water by Dinitrophenylhydrazine Derivatization
and High Performance Liquid Chromatography. Revision 1.0. Office of
Research and Development, Cincinnati, OH. August 1992. Available at
<a href="https://www.nemi.gov/methods/method_summary/12611/">https://www.nemi.gov/methods/method_summary/12611/</a>.
(xxxv) USEPA. 1994a. Method 200.7--Determination of Metals and Trace
Elements in Water and Wastes by Inductively Coupled Plasma-Atomic
Emission Spectrometry. Revision 4.4. Office of Research and
Development, Cincinnati, OH. 1994. Available at <a href="https://www.epa.gov/esam/method-2007-determination-metals-and-trace-elements-water-and-wastes-inductively-coupled-plasma">https://www.epa.gov/esam/method-2007-determination-metals-and-trace-elements-water-and-wastes-inductively-coupled-plasma</a>.
(xxxvi) USEPA. 1994b. Method 200.8--Determination Trace Elements in
Waters and Wastes by Inductively Coupled Plasma-Mass Spectrometry.
Revision 5.4. Office of Research and Development, Cincinnati, OH.
1994. Available at <a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-200.8.pdf">https://www.epa.gov/sites/default/files/2015-06/documents/epa-200.8.pdf</a>.

[[Page 8596]]

(xxxvii) USEPA. 1994c. Method 200.9--Determination of Trace Elements
by Stabilized Temperature Graphic Furnace Atomic Absorption.
Revision 2.2. Office of Research and Development, Cincinnati, OH.
1994 Available at <a href="https://www.epa.gov/sites/default/files/2015-08/documents/method_200-9_rev_2-2_1994.pdf">https://www.epa.gov/sites/default/files/2015-08/documents/method_200-9_rev_2-2_1994.pdf</a>.
(xxxviii) USEPA. 1995a. Method 502.2--Volatile Organic Compounds in
Water by Purge and Trap Capillary Column Gas Chromatography with
Photoionization and Electrolytic Conductivity Detectors in Series.
Revision 2.1. Office of Research and Development, Cincinnati, OH.
1995. Available at <a href="https://www.nemi.gov/methods/method_summary/4827/">https://www.nemi.gov/methods/method_summary/4827/</a>.
(xxxix) USEPA. 1995b. Method 504.1--1,2-Dibromoethane (EDB), 1,2-
Dibromo-3-Chloro-Propane (DBCP), and 1,2,3-Trichloropropane (123TCP)
in Water by Microextraction and Gas Chromatography. Revision 1.1.
Office of Research and Development, Cincinnati, OH. 1995. Available
at <a href="https://www.nemi.gov/methods/method_summary/4825/">https://www.nemi.gov/methods/method_summary/4825/</a>.
(xl) USEPA. 1995c. Method 505--Analysis of Organohalide Pesticides
and Commercial Polychlorinated Biphenyl (PCB) Products in Water by
Microextraction and Gas Chromatography. Revision 2.1. Office of
Research and Development, Cincinnati, OH. 1995. Available at <a href="https://www.nemi.gov/methods/method_summary/4799/">https://www.nemi.gov/methods/method_summary/4799/</a>.
(xli) USEPA. 1995d. Method 507--Determination of Nitrogen and
Phosphorus Containing Pesticides in Water by Gas Chromatography with
a Nitrogen-Phosphorus Detector. Revision 2.1. Office of Research and
Development, Cincinnati, OH. 1995. Available at <a href="https://www.nemi.gov/methods/method_summary/4801/">https://www.nemi.gov/methods/method_summary/4801/</a>.
(xlii) USEPA. 1995e. Method 508--Determination of Chlorinated
Pesticides in Water by Gas Chromatography with an Electron Capture
Detector. Revision 3.1. Office of Research and Development,
Cincinnati, OH. 1995. Available at <a href="https://www.nemi.gov/methods/method_summary/4826/">https://www.nemi.gov/methods/method_summary/4826/</a>.
(xliii) USEPA. 1995f. Method 508.1--Determination of Chlorinated
Pesticides, Herbicides, and Organohalides by Liquid-Solid Extraction
and Electron Capture Gas Chromatography. Revision 2.0. Office of
Research and Development, Cincinnati, OH. 1995. Available at <a href="https://www.nemi.gov/methods/method_summary/4802/">https://www.nemi.gov/methods/method_summary/4802/</a>.
(xliv) USEPA. 1995g. Method 524.2--Measurement of Purgeable Organic
Compounds in Water by Capillary Column Gas Chromatography/Mass
Spectrometry. Revision 4.1. Office of Research and Development,
Cincinnati, OH. 1995. Available at <a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-524.2.pdf">https://www.epa.gov/sites/default/files/2015-06/documents/epa-524.2.pdf</a>.
(xlv) USEPA. 1995h. Method 525.2--Determination of Organic Compounds
in Drinking Water by Liquid-Solid Extraction and Capillary Column
Gas Chromatography/Mass Spectrometry. Revision 2.0. Office of
Research and Development, Cincinnati, OH. 1995. Available at <a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-525.2.pdf">https://www.epa.gov/sites/default/files/2015-06/documents/epa-525.2.pdf</a>.
(xlvi) USEPA. 1995i. Method 531.1--Measurement of N-
Methylcarbamoyloximes and N-Methylcarbamates in Water by Direct
Aqueous Injection HPLC with Post Column Derivatization. Revision
3.1. Office of Research and Development, Cincinnati, OH. 1995.
Available at <a href="https://www.nemi.gov/methods/method_summary/4805/">https://www.nemi.gov/methods/method_summary/4805/</a>.
(xlvii) USEPA. 1995j. Method 551.1--Determination of Chlorination
Disinfection Byproducts, Chlorinated Solvents, and Halogenated
Pesticides/Herbicides in Drinking Water by Liquid-Liquid Extraction
and Gas Chromatography with Electron-Capture Detection. Revision
1.0. Office of Research and Development, Cincinnati, OH. 1995.
Available at <a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-551.1.pdf">https://www.epa.gov/sites/default/files/2015-06/documents/epa-551.1.pdf</a>.
(xlviii) USEPA. 1995k. Method 552.2--Determination of Haloacetic
Acids and Dalapon in Drinking Water by Liquid-Liquid Extraction,
Derivatization and Gas Chromatography with Electron Capture
Detection. Revision 1.0. Office of Research and Development,
Cincinnati, OH. 1995. Available at <a href="https://www.nemi.gov/methods/method_summary/4787/">https://www.nemi.gov/methods/method_summary/4787/</a>.
(xlix) USEPA. 1997. Method 300.1--Determination of Inorganic Anions
in Drinking Water by Ion Chromatography. Revision 1.0. Office of
Research and Development, Cincinnati, OH. 1997. Available at <a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-300.1.pdf">https://www.epa.gov/sites/default/files/2015-06/documents/epa-300.1.pdf</a>.
(l) USEPA. 1999. Method 556.1--Determination of Carbonyl Compounds
in Drinking Water by Fast Gas Chromatography. Revision 1.0. Office
of Research and Development, Cincinnati, OH. September 1999.
Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(li) USEPA. 2000a. Method 526--Determination of Selected
Semivolatile Organic Compounds in Drinking Water by Solid Phase
Extraction and Capillary Column Gas Chromatography/Mass Spectrometry
(GC/MS). Revision 1.0. Office of Research and Development,
Cincinnati, OH. June 2000. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lii) USEPA. 2000b. Method 528--Determination of Phenols in Drinking
Water by Solid Phase Extraction and Capillary Column Gas
Chromatography/Mass Spectrometry (GC/MS). Revision 1.0. Office of
Research and Development, Cincinnati, OH. April 2000. Available at
<a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(liii) USEPA. 2000c. Method 532--Determination of Phenylurea
Compounds in Drinking Water by Solid Phase Extraction and High
Performance Liquid Chromatography with UV Detection. Revision 1.0.
Office of Research and Development, Cincinnati, OH. June 2000.
Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(liv) USEPA. 2001. Method 531.2--Measurement of N-
Methylcarbamoyloximes and N-Methylcarbamates in Water by Direct
Aqueous Injection HPLC with Postcolumn Derivatization. Revision 1.0.
EPA 815-B-01-002. Office of Ground Water and Drinking Water,
Cincinnati, OH. September 2001. Available at <a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-531.2.pdf">https://www.epa.gov/sites/default/files/2015-06/documents/epa-531.2.pdf</a>.
(lv) USEPA. 2003a. Method 552.3--Determination of Haloacetic Acids
and Dalapon in Drinking Water by Liquid-Liquid Microextraction,
Derivatization, and Gas Chromatography with Electron Capture
Detection. Revision 1.0. EPA 815-B-03-002. Office of Ground Water
and Drinking Water, Cincinnati, OH. July 2003. Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/901V0400.PDF?Dockey=901V0400.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/901V0400.PDF?Dockey=901V0400.PDF</a>.
(lvi) USEPA. 2003b. Method 200.5--Determination of Trace Elements in
Drinking Water by Axially Viewed Inductively Coupled Plasma-Atomic
Emission Spectrometry. Revision 4.2. EPA 600-R-06-115. Office of
Research and Development, Cincinnati, OH. October 2003. Available at
<a href="https://www.epa.gov/sites/default/files/2015-08/documents/method_200-5_rev_4-2_2003.pdf">https://www.epa.gov/sites/default/files/2015-08/documents/method_200-5_rev_4-2_2003.pdf</a>.
(lvii) USEPA. 2004. Method 521--Determination of Nitrosamines in
Drinking Water by Solid Phase Extraction and Capillary Column Gas
Chromatography with Large Volume Injection and Chemical Ionization
Tandem Mass Spectrometry (MS/MS). Version 1.0. EPA 600-R-05-054.
Office of Research and Development, Cincinnati, OH. September 2004.
Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lviii) USEPA. 2005. Method 527--Determination of Selected
Pesticides and Flame Retardants in Drinking Water by Solid Phase
Extraction and Capillary Column Gas Chromatography/Mass Spectrometry
(GC/MS). Revision 1.0. EPA 815-R-05-005. Office of Ground Water and
Drinking Water, Cincinnati, OH. April 2005. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lix) USEPA. 2007. Method 536--Determination of Triazine Pesticides
and their Degradates in Drinking Water by Liquid Chromatography
Electrospray Ionization Tandem Mass Spectrometry (LC/ESI-MS/MS).
Version 1.0. EPA 815-B-07-002. Office of Ground Water and Drinking
Water, Cincinnati, OH. October 2007. Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/P1005E35.PDF?Dockey=P1005E35.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/P1005E35.PDF?Dockey=P1005E35.PDF</a>.
(lx) USEPA. 2008. Method 522--Determination of 1,4-Dioxane in
Drinking Water by Solid Phase

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Extraction (SPE) and Gas Chromatography/Mass Spectrometry (GC/MS)
with Selected Ion Monitoring (SIM). Revision 1.0. EPA 600-R-08-101.
Office of Research and Development, Cincinnati, OH. September 2008.
Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxi) USEPA. 2009a. Method 524.3--Measurement of Purgeable Organic
Compounds in Water by Capillary Column Gas Chromatography/Mass
Spectrometry. Version 1.0. EPA 815-B-09-009. Office of Ground Water
and Drinking Water, Cincinnati, OH. June 2009. Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J75C.PDF?Dockey=P100J75C.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J75C.PDF?Dockey=P100J75C.PDF</a>.
(lxii) USEPA. 2009b. Method 557: Determination of Haloacetic Acids,
Bromate, and Dalapon in Drinking Water by Ion Chromatography
Electrospray Ionization Tandem Mass Spectrometry (IC-ESI-MS/MS).
Version 1.0. Office of Water, Cincinnati, OH. September 2009.
Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/P1005OKO.PDF?Dockey=P1005OKO.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/P1005OKO.PDF?Dockey=P1005OKO.PDF</a>.
(lxiii) USEPA. 2009c. Method 538--Determination of Selected Organic
Contaminants in Drinking Water by Direct Aqueous Injection-Liquid
Chromatography/Tandem Mass Spectrometry (DAI-LC/MS/MS). Version 1.0.
EPA 600-R-09-149. Office of Research and Development, Cincinnati,
OH. November 2009. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxiv) USEPA. 2010. Method 539--Determination of Hormones in
Drinking Water by Solid Phase Extraction (SPE) and Liquid
Chromatography Electrospray Ionization Tandem Mass Spectrometry (LC-
ESI-MS/MS). Version 1.0. EPA 815-B-10-001. Office of Water,
Cincinnati, OH. November 2010. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxv) USEPA. 2011. Method 523--Determination of Triazine Pesticides
and their Degradates in Drinking Water by Gas Chromatography/Mass
Spectrometry (GC/MS). Version 1.0. EPA 815-R-11-002. Office of
Water, Cincinnati, OH. February 2011. Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J7D4.PDF?Dockey=P100J7D4.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J7D4.PDF?Dockey=P100J7D4.PDF</a>.
(lxvi) USEPA. 2012. Method 525.3--Determination of Semivolatile
Organic Chemicals in Drinking Water by Solid Phase Extraction and
Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS).
Version 1.0. EPA 600-R-12-010. Office of Research and Development,
Cincinnati, OH. February 2012. Available at <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=241188">https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=241188</a>.
(lxvii) USEPA. 2013a. Method 524.4--Measurement of Purgeable Organic
Compounds in Water by Gas Chromatography/Mass Spectrometry Using
Nitrogen Purge Gas. EPA 815-R-13-002. Office of Water, Cincinnati,
OH. May 2013. Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J7EE.PDF?Dockey=P100J7EE.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J7EE.PDF?Dockey=P100J7EE.PDF</a>.
(lxviii) USEPA. 2013b. Method 540--Determination of Selected Organic
Chemicals in Drinking Water by Solid Phase Extraction and Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS). Version 1.0. EPA
600-R-13-119. Office of Research and Development, Cincinnati, OH.
September 2013. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxix) USEPA. 2014. Method 1615--Measurement of Enterovirus and
Norovirus Occurrence in Water by Culture and RT-qPCR. Version 1.3.
Office of Research and Development, Cincinnati, OH. September 2014.
Available at <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=306930&Lab=NERL">https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=306930&Lab=NERL</a>.
(lxx) USEPA. 2015a. Method 530--Determination of Select Semivolatile
Organic Chemicals in Drinking Water by Solid Phase Extraction and
Gas Chromatography/Mass Spectrometry (GC/MS). Version 1.0. EPA 600-
R-14-442. Office of Research and Development, Cincinnati, OH.
January 2015. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxxi) USEPA. 2015b. Method 544--Determination of Microcystins and
Nodularin in Drinking Water by Solid Phase Extraction and Liquid
Chromatography/Tandem Mass Spectrometry (LC/MS/MS). Version 1.0. EPA
600-R-14-474. Office of Research and Development, Cincinnati, OH.
February 2015. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxxii) USEPA. 2015c. Method 543--Determination of Selected Organic
Chemicals in Drinking Water by On-Line Solid Phase Extraction-Liquid
Chromatography/Tandem Mass Spectrometry (On-Line SPE-LC/MS/MS).
Version 1.0. EPA 600-R-14-098. Office of Research and Development,
Cincinnati, OH. March 2015. Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi/P100MD0C.PDF?Dockey=P100MD0C.PDF">https://nepis.epa.gov/Exe/ZyPDF.cgi/P100MD0C.PDF?Dockey=P100MD0C.PDF</a>.
(lxxiii) USEPA. 2015d. Method 545: Determination of
Cylindrospermopsin and Anatoxin-a in Drinking Water by Liquid
Chromatography Electrospray Ionization Tandem Mass Spectrometry (LC/
ESI-MS/MS). EPA 815-R-15-009. Office of Water, Cincinnati, OH. April
2015. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxxiv) USEPA. 2015e. Method 541: Determination of 1-Butanol, 1,4-
Dioxane, 2-Methoxyethanol and 2-Propen-1-ol in Drinking Water by
Solid Phase Extraction and Gas Chromatography/Mass Spectrometry. EPA
815-R-15-011. Office of Water, Cincinnati, OH. November 2015.
Available at <a href="https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100NGIF.txt">https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100NGIF.txt</a>.
(lxxv) USEPA. 2016a. Method 600/R-16/114-Analytical Protocol for
Measurement of Extractable Semivolatile Organic Compounds Using Gas
Chromatography/Mass Spectrometry. Office of Research and
Development, Cincinnati, OH. July 2016. Available at <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=337629&Lab=NHSRC">https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=337629&Lab=NHSRC</a>.
(lxxvi) USEPA. 2016b. Method Validation of U.S. Environmental
Protection Agency (EPA) Microbiological Methods of Analysis. FEM
Document Number 2009-01. December 2016. Available at <a href="https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines">https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines</a>.
(lxxvii) USEPA. 2016c. Validation and Peer Review of U.S.
Environmental Protection Agency Chemical Methods of Analysis. FEM
Document Number 2005-01. February 2016. Available at <a href="https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines">https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines</a>.
(lxxviii) USEPA. 2019a. Method 533: Determination of Per- and
Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution
Anion Exchange Solid Phase Extraction and Liquid Chromatography/
Tandem Mass Spectrometry. EPA 815-B-19-020. Office of Water,
Cincinnati, OH. November 2019. Available at <a href="https://www.epa.gov/dwanalyticalmethods">https://www.epa.gov/dwanalyticalmethods</a>.
(lxxix) USEPA. 2019b. Technical Brief Innovative Research for a
Sustainable Future: Perfluoroalkyl and Polyfluoroalkyl Substances
(PFAS) Methods and guidance for sampling and analyzing water and
other environmental media. EPA 600-F-17-022g. Office of Research and
Development, Cincinnati, OH. March 2010. Available at <a href="https://www.epa.gov/sites/default/files/2019-12/documents/pfas_methods-sampling_tech_brief_23dec19_update.pdf">https://www.epa.gov/sites/default/files/2019-12/documents/pfas_methods-sampling_tech_brief_23dec19_update.pdf</a>.
(lxxx) USEPA. 2020a. Method 537.1: Determination of Selected Per-
and Polyfluorinated Alkyl Substances in Drinking Water by Solid
Phase Extraction and Liquid Chromotography/Tandem Mass Spectrometry
(LC/MS/MS). Version 2.0. EPA 600-R-20-006. Office of Research and
Development, Cincinnati, OH. March 2010. Available at <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=348508&Lab=CESER&simpleSearch=0&showCriteria=2&searchAll=537.1&TIMSType=&dateBeginPublishedPresented=03%2F24%2F2018">https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=348508&Lab=CESER&simpleSearch=0&showCriteria=2&searchAll=537.1&TIMSType=&dateBeginPublishedPresented=03%2F24%2F2018</a>.
(lxxxi) USEPA. 2020b. Method 559--Determination of Nonylphenol and
4-Tert-Octylphenol in Drinking Water by Solid Phase Extraction and
Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). Version
1.0. EPA 600-R-20-270. Office of Research and Development,
Cincinnati, OH. September 2020. Available at <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=CESER&dirEntryId=349691">https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=CESER&dirEntryId=349691</a>.
(lxxxii) USEPA. 2022a. Draft Method 1621: Screening Method for the
Determination of Adsorbable Organic Fluorine (AOF) in Aqueous
Matrices by Combustion Ion

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Chromatography (CIC). EPA-821-D-22-0202. Office of Research and
Development, Cincinnati, OH. April 2022. Available at <a href="https://www.epa.gov/system/files/documents/2022-04/draft-method-1621-for-screening-aof-in-aqueous-matrices-by-cic_0.pdf">https://www.epa.gov/system/files/documents/2022-04/draft-method-1621-for-screening-aof-in-aqueous-matrices-by-cic_0.pdf</a>.
(lxxxiii) USEPA. 2022b. Drinking Water Contaminant Candidate List
5--Final. Federal Register. Vol. 87, No. 218, p. 68060, November 14,
2022.
(lxxxiv) USEPA. 2023. Comptox Chemicals Dashboard v2.3.0. <a href="https://comptox.epa.gov/dashboard/chemical-lists/PFASSTRUCT">https://comptox.epa.gov/dashboard/chemical-lists/PFASSTRUCT</a> (accessed
January 24, 2024) PFAS Structure Lists.
(lxxxv) Wong, C. & Coffin, S. 2022. Standard Operating Procedures
for Extraction and Measurement by Infrared Spectroscopy of
Microplastic Particles in Drinking Water. California State Water
Resources Control Board. May 27, 2022. Available at <a href="https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/microplastics/swb-mp1-rev1.pdf">https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/microplastics/swb-mp1-rev1.pdf</a>.

Jennifer L. McLain,
Director, Office of Ground Water and Drinking Water.
[FR Doc. 2024-02247 Filed 2-7-24; 8:45 am]
BILLING CODE P

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