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:

• Federal eRulemaking Portal: https://www.regulations.gov/ (preferred). Follow the online instructions for submitting comments.

• 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.

• 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: bowden.brenda@epa.gov; 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: adams.william@epa.gov.

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 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

µm 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 UCMRWebinar@cadmusgroup.com. The last day to pre-register to speak at the webinar is April 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 UCMRWebinar@cadmusgroup.com. 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.

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.

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.

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).

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 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).

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.

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.

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.

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 (µm) 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.

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 °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.

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 µm 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 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 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., Vénisseau, 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.

(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 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 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.