Introduction
EPA has reviewed an Alternate Test Procedure application, SGS AXYS Method ATM 16130 (ATP Case No. N18-0003), “Determination of 2,3,7,8-Substituted Tetra- through Octa-Chlorinated Dibenzo-p-Dioxins and Dibenzofurans (CDDs/CDFs) Using Waters and Agilent Gas Chromatography-Tandem-Mass Spectrometry (GC/MS/MS),” and the supporting validation data in ATP Case No. N18-0003. EPA determined that this method meets all requirements for measurement of 2,3,7,8-substituted tetra- through octa-chlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) in wastewater. That is, the performance of this method is substantially similar to methods listed at 40 CFR Part 136 for measurement of PCDDs/PCDFs in wastewater.
EPA plans to include the method in a future regulatory action in which the Agency adds to the list of approved methods at Part 136. However, this ATP review does not replace the normal notice-and-comment rulemaking process required for methods to be approved for nationwide use. In the interim, a user may, on a facility-by-facility basis, seek approval from its EPA regional authority for use of this method in measuring PCDDs/PCDFs in wastewater in Clean Water Act (CWA) programs.
Information regarding this review has been released publicly from several different sources and has caused some confusion. EPA is providing information on this page to resolve any questions regarding the status of the method until it is approved and promulgated at Part 136.
Questions and Answers
- What methods are approved by EPA for measurement of the 17 2,3,7,8-substituted PCDDs/PCDFs that are regulated under the Clean Water Act?
The only method currently approved at 40 CFR Part 136 for measurement of the 17 2,3,7,8-substituted PCDDs/PCDFs is EPA Method 1613B. EPA Method 625.1 may be used for screening purposes when a specific NPDES permit requires monitoring of only 2,3,7,8-Tetrachlorodibenzo-p-dioxin. EPA Method 613 may be used for analyte-specific determination of 2,3,7,8-Tetrachlorodibenzo-p-dioxin and for its quantitation provided that the laboratory can demonstrate that the method is sufficiently sensitive to allow for quantitation at the limit specified in a given permit in a given matrix.- SeeTable IC—List of Approved Test Procedures for Non-Pesticide Organic Compounds at 40 CFR Part 136.3 – Identification of Test Procedures
- SeeTable IC—List of Approved Test Procedures for Non-Pesticide Organic Compounds at 40 CFR Part 136.3 – Identification of Test Procedures
- Has EPA approved SGS AXYS Method ATM 16130 as an alternate test procedure (ATP) for determination of 2,3,7,8-substituted tetra- through octa-chlorinated PCDDs/PCDFs in wastewater?
Not at the present time. The method was submitted to EPA for review as an ATP for nationwide-use under the Clean Water Act ATP program. The method and supporting information, including the validation study report and method performance data, were reviewed and EPA determined that the method met all requirements for measurement of the regulated PCDDs/PCDFs in wastewater. As a result, this method is a candidate for inclusion in a future regulatory action in which EPA periodically updates the methods approved at 40 CFR Part 136 for use in CWA compliance monitoring. An ATP review does not replace the normal notice-and-comment rulemaking process required for promulgation (approval) of the method at Part 136.
- Can SGS AXYS Method ATM 16130 be used to support NPDES permits right now? How does one obtain limited use approval?
SGS AXYS Method ATM 16130 can be approved for NPDES permits on a case-by-case basis as a limited-use ATP, as is outlined in the regulatory text at 40 CFR 136.5, "Approval of alternate test procedures for limited-use.” Limited use approval is granted by the Regional ATP Coordinator, typically for a specific discharge or facility (and its laboratory). For more information, see the full text at §136.5.
- What prompted EPA to consider the ATP?
EPA routinely considers requests for ATPs to promote innovation in the CWA analytical methods program. Any person or organization may apply for an ATP, and EPA considers every ATP application that is received. In the case of SGS AXYS Method ATM 16130, EPA heard from instrument vendors and laboratories analyzing PCDDs/PCDFs for some time that there was likely to be little further development or support of the high-resolution mass spectrometers (GC/HRMS) required to run Method 1613B. Several vendors have ceased development of high resolution mass spectrometers, so it will become increasingly challenging for laboratories to obtain parts and supplies for specific instrument models from these vendors. EPA recognized the need to consider other detector systems, such as GC/MS/MS. Therefore, when EPA was approached by the ATP applicant several years ago, we were open to discussions about an ATP to Method 1613B.
- What is different about SGS AXYS Method ATM 16130, compared to EPA Method 1613B?
The major difference between the two methods is the use of a GC/MS/MS instrument that uses Multiple Reaction Monitoring (MRM) in place of the GC/HRMS instrument. This change of detector system required the ATP applicant to come up with an alternative metric for mass resolution and ionization stability, in lieu of that in Method 1613B, as well as specifying the mass fragments and mass transitions and transition response ratios that must be monitored by the MS/MS system to accurately identify the target analytes.
All of the sample preparation, extraction, and cleanup steps in Method 1613B are included in the ATP. That is, the matrix-specific extraction procedures in both methods are the same. In both methods, each sample is spiked with the same suite of carbon-labeled standards prior to extraction and those standards are used for isotope dilution quantitation, in the same way. All of the relevant QC acceptance criteria are the same in both methods as well.
- Will SGS AXYS 16130 become an EPA-approved method?
SGS AXYS ATM 16130 needs to go through the same approval process as any other ATP that has been positively reviewed for nationwide use. EPA will have to propose the ATP in a future regulatory action that adds it to the list of approved methods at 40 CFR Part 136. These regulatory actions are called "Method Update Rules" (MURs). After a MUR is proposed, there is a public comment period and an ATP will not be approved if there are any adverse public comments that cannot be addressed in EPA’s formal Response to Comments document. If EPA has not received any unresolvable public comments regarding the ATP, then it will be included in the final MUR, and is approved and added to the relevant table at §136.3.
- Can my organization submit an application for approval of a GC/MS/MS method for determination of 2,3,7,8-substituted tetra- through octa-chlorinated PCDDs/PCDFs in wastewater as an ATP?
Yes, the CWA ATP process is open to any individual or organization. Applicants have historically been permittees, laboratories, vendors, and other state or federal agencies. An application for approval of an ATP must specify the method approved at 40 CFR Part 136 to which an ATP has been submitted as an alternate. In this case, the approved method would be EPA Method 1613B, since SGS AXYS Method ATM 16130 is not yet an approved method. The ATP applicant must submit an application and a written method utilizing a GC-Tandem-MS/MS with MRM. (MRM analysis is required to achieve specificity in the CDD/CDF analysis. Quantitative analysis is performed in the MRM mode by monitoring two MRM transitions for each analyte and labeled standard.) The applicant also must submit a study plan for validation of their ATP using either an interlaboratory validation or side-by-side validation comparing Method 1613B and the proposed ATP for review by EPA.
- Can SGS AXYS Method ATM 16130 be used for reporting results for drinking water compliance monitoring?
No, the SGS AXYS method was submitted and reviewed as an ATP for nationwide-use for compliance monitoring required under the CWA. The Office of Ground Water and Drinking Water maintains a separate ATP program, as well as its own method approval program under the Safe Drinking Water Act (SDWA). Those programs have separate requirements from the CWA ATP and method approval programs. Review of an ATP under the CWA or promulgation of an ATP at 40 CFR Part 136 does not affect the methods approved for use in compliance monitoring required under the SDWA.
- If our laboratory gets limited-use ATP approval to use the method for reporting results for CWA compliance monitoring, how should we refer to the method?
The name of the method is “SGS AXYS Method ATM 16130” and it should be identified that way in any applications for limited-use approval and for any subsequent reports and correspondence. The fact that the ATP applicant’s name is in the name of the method is not unusual or unprecedented and is intended to clearly identify the analytical method that was submitted for review as an ATP for nationwide-use and the organization responsible for the method.
