[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 [www.gpo.gov]
[FR Doc No: 2024-02247]


=======================================================================
-----------------------------------------------------------------------

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.

-----------------------------------------------------------------------

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: https://www.regulations.gov/ 
(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 https://www.regulations.gov/, 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 https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials. 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 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 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 
https://www.regulations.gov (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 https://www.regulations.gov 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 https://www.epa.gov/dockets/commenting-epa-dockets 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 https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials 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 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: https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials. 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 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 
https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials 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: https://www.epa.gov/ccl.
    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 (https://www.epa.gov/sdwa/national-contaminant-occurrence-database-ncod) or via the UCMR web page 
at: https://www.epa.gov/dwucmr.

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 https://www.epa.gov/water-research/microplastics-research.
    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 https://www.federalregister.gov/documents/2022/11/14/2022-23963/drinking-water-contaminant-candidate-list-5-final.
    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 
https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines.
    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 astm.org.
(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 astm.org.
(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 
astm.org.
(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 astm.org.
(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 astm.org.
(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 astm.org.
(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 astm.org.
(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 astm.org.
(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 astm.org.
(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 astm.org.
(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 astm.org.
(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. DOI.org/10.1016/j.chroma.2015.07.013.
(xiv) ISO Online. 2017. 11731:2017--Water Quality--Enumeration of 
Legionella. ISO Standards. Available for purchase at https://www.iso.org/standards.html.
(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 
https://www.iso.org/standards.html.
(xvi) Interstate Technology Regulatory Council (ITRC). 2023. 
Microplastics Outreach Toolkit--Sampling and Analysis. February 
2023. Available at https://mp-1.itrcweb.org/sampling-and-analysis/.
(xvii) SM Online. 1997a. 3500-V--Vanadium (Editorial Revisions, 
2020). Standard Methods Online. Available for purchase at http://www.standardmethods.org.
(xviii) SM Online. 1997b. 6200--Volatile Organic Compounds Method 
(Editorial Revisions, 2011 and 2020). Standard Methods Online. 
Available for purchase at http://www.standardmethods.org.
(xix) SM Online. 1999a. 3111--Metals by Flame Atomic Absorption 
Spectrometry Method (Editorial Revisions, 2019). Standard Methods 
Online. Available for purchase at http://www.standardmethods.org.
(xx) SM Online. 1999b. 3120--Metals by Plasma Emission Spectroscopy 
Method (Editorial Revisions, 2020). Standard Methods Online. 
Available for purchase at http://www.standardmethods.org.
(xxi) SM Online. 1999c. 3500-Mn--Manganese (Editorial Revisions, 
2020). Standard Methods Online. Available for purchase at http://www.standardmethods.org.
(xxii) SM Online. 2000a. 4110--Determination of Anions by Ion 
Chromatography Method (Editorial Revisions, 2020). Standard Methods 
Online. Available for purchase at http://www.standardmethods.org.
(xxiii) SM Online. 2000b. 4500-B--Boron (Editorial Revisions, 2020). 
Standard Methods Online. Available for purchase at http://www.standardmethods.org.
(xxiv) SM Online. 2004a. 3500-Li--Lithium (Editorial Revisions, 
2020). Standard Methods Online. Available for purchase at http://www.standardmethods.org.
(xxv) SM Online. 2004b. 6610--Carbamate Pesticides Method (Editorial 
Revisions, 2021). Standard Methods Online. Available for purchase at 
http://www.standardmethods.org.
(xxvi) SM Online. 2005. 6252--Disinfection Byproducts: Aldehydes 
Method (Proposed) (Editorial Revisions, 2020). Standard Methods 
Online. Available for purchase at http://www.standardmethods.org.
(xxvii) SM Online. 2007a. 6251--Disinfection Byproducts: Haloacetic 
Acids and Trichlorophenol Method (Editorial Revisions, 2020). 
Standard Methods Online. Available for purchase at http://www.standardmethods.org.
(xxviii) SM Online. 2007b. 6450--Nitrosamines Method (Editorial 
Revisions, 2021). Standard Methods Online. Available for purchase at 
http://www.standardmethods.org.
(xxix) SM Online. 2007c. 9213--Recreational Waters (Editorial 
Revisions, 2022). Standard Methods Online. Available for purchase at 
http://www.standardmethods.org.
(xxx) SM Online. 2010. 3113--Metals by Electrothermal Atomic 
Absorption Spectrometry Method (Editorial Revisions, 2020). Standard 
Methods Online. Available for purchase at http://www.standardmethods.org.
(xxxi) SM Online. 2013. 6810--Pharmaceuticals and Personal Care 
Products Method (Editorial Revisions, 2021). Standard Methods 
Online. Available for purchase at http://www.standardmethods.org.
(xxxii) SM Online. 2021. 9750--Detection of Naegleria fowleri in 
Water. Standard Methods Online. Available for purchase at http://www.standardmethods.org.
(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 https://www.nemi.gov/methods/method_summary/4784/.
(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 
https://www.nemi.gov/methods/method_summary/12611/.
(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 https://www.epa.gov/esam/method-2007-determination-metals-and-trace-elements-water-and-wastes-inductively-coupled-plasma.
(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 https://www.epa.gov/sites/default/files/2015-06/documents/epa-200.8.pdf.

[[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 https://www.epa.gov/sites/default/files/2015-08/documents/method_200-9_rev_2-2_1994.pdf.
(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 https://www.nemi.gov/methods/method_summary/4827/.
(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 https://www.nemi.gov/methods/method_summary/4825/.
(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 https://www.nemi.gov/methods/method_summary/4799/.
(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 https://www.nemi.gov/methods/method_summary/4801/.
(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 https://www.nemi.gov/methods/method_summary/4826/.
(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 https://www.nemi.gov/methods/method_summary/4802/.
(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 https://www.epa.gov/sites/default/files/2015-06/documents/epa-524.2.pdf.
(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 https://www.epa.gov/sites/default/files/2015-06/documents/epa-525.2.pdf.
(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 https://www.nemi.gov/methods/method_summary/4805/.
(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 https://www.epa.gov/sites/default/files/2015-06/documents/epa-551.1.pdf.
(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 https://www.nemi.gov/methods/method_summary/4787/.
(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 https://www.epa.gov/sites/default/files/2015-06/documents/epa-300.1.pdf.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 
https://www.epa.gov/dwanalyticalmethods.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://www.epa.gov/sites/default/files/2015-06/documents/epa-531.2.pdf.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi/901V0400.PDF?Dockey=901V0400.PDF.
(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 
https://www.epa.gov/sites/default/files/2015-08/documents/method_200-5_rev_4-2_2003.pdf.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi/P1005E35.PDF?Dockey=P1005E35.PDF.
(lx) USEPA. 2008. Method 522--Determination of 1,4-Dioxane in 
Drinking Water by Solid Phase

[[Page 8597]]

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 https://www.epa.gov/dwanalyticalmethods.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J75C.PDF?Dockey=P100J75C.PDF.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi/P1005OKO.PDF?Dockey=P1005OKO.PDF.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J7D4.PDF?Dockey=P100J7D4.PDF.
(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 https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=241188.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi/P100J7EE.PDF?Dockey=P100J7EE.PDF.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=306930&Lab=NERL.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi/P100MD0C.PDF?Dockey=P100MD0C.PDF.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100NGIF.txt.
(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 https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=337629&Lab=NHSRC.
(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 https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines.
(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 https://www.epa.gov/measurements-modeling/method-validation-and-peer-review-policies-and-guidelines.
(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 https://www.epa.gov/dwanalyticalmethods.
(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 https://www.epa.gov/sites/default/files/2019-12/documents/pfas_methods-sampling_tech_brief_23dec19_update.pdf.
(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 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.
(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 https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=CESER&dirEntryId=349691.
(lxxxii) USEPA. 2022a. Draft Method 1621: Screening Method for the 
Determination of Adsorbable Organic Fluorine (AOF) in Aqueous 
Matrices by Combustion Ion

[[Page 8598]]

Chromatography (CIC). EPA-821-D-22-0202. Office of Research and 
Development, Cincinnati, OH. April 2022. Available at https://www.epa.gov/system/files/documents/2022-04/draft-method-1621-for-screening-aof-in-aqueous-matrices-by-cic_0.pdf.
(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. https://comptox.epa.gov/dashboard/chemical-lists/PFASSTRUCT (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 https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/microplastics/swb-mp1-rev1.pdf.

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


</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>