Methods for Measurement of 2,3,7,8-substituted tetra through octa-chlorinated dibenzo-p-dioxins and dibenzofurans in Wastewater

Introduction

The EPA has reviewed two Alternate Test Procedure applications for the measurement of 2,3,7,8-substituted tetra through octa-chlorinated dibenzo-p-dioxins and dibenzofurans in wastewater: 

• 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
• Pace Analytical Method PAM-16130-SSI (ATP Case No. N21-0001), “Determination of 2,3,7,8-Substituted Tetra- through Octa-Chlorinated Dibenzo-p-Dioxins and Dibenzofurans (CDDs/CDFs) Using Shimadzu Gas Chromatography Mass Spectrometry (GC-MS/MS), Revision 1.1.”

After reviewing the method and the supporting validation data, the EPA determined that these methods meet 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 these methods is substantially similar to methods listed at 40 CFR Part 136 for measurement of PCDDs/PCDFs in wastewater.

The EPA plans to include the methods 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. The 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

1. What methods are approved by the 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. The EPA has no plans to withdraw 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.
   • Refer to Table IC—List of Approved Test Procedures for Non-Pesticide Organic Compounds at 40 CFR Part 136.3 – Identification of Test Procedures
      
2. Has the EPA approved SGS AXYS Method ATM 16130 and Pace Analytical Method PAM-16130-SSI as alternate test procedures (ATPs) for determination of 2,3,7,8-substituted tetra- through octa-chlorinated PCDDs/PCDFs in wastewater?
   
   Not at the present time. The methods were submitted to the EPA for review as  ATPs for nationwide-use under the Clean Water Act ATP program. The methods and supporting information, including the validation study reports and method performance data, were reviewed and the EPA determined that the methods met all requirements for measurement of the regulated PCDDs/PCDFs in wastewater. As a result, these methods are candidates for inclusion in a future regulatory action in which the EPA periodically updates the methods approved at 40 CFR Part 136 for use in CWA compliance monitoring. ATP reviews do not replace the normal notice-and-comment rulemaking process required for promulgation (approval) of methods at Part 136.

3. Can SGS AXYS Method ATM 16130 and Pace Analytical Method PAM-16130-SSI be used to support NPDES permits right now? How does one obtain limited use approval?
   
   SGS AXYS Method ATM 16130 and Pace Analytical Method PAM-16130-SSI can be approved for NPDES permits on a case-by-case basis as limited-use ATPs, 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, refer to the full text at §136.5.
4. What prompted the EPA to consider these ATPs?
   
   The 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 cases of SGS AXYS Method ATM 16130 and Pace Analytical Method PAM-16130-SSI, 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. The EPA recognized the need to consider other detector systems, such as GC/MS/MS. Therefore, when the EPA was approached by the ATP applicants several years ago, we were open to discussions about ATPs to Method 1613B.
5. What is different about SGS AXYS Method ATM 16130 and Pace Analytical Method PAM-16130-SSI, compared to EPA Method 1613B?

   The major difference between the ATPs and Method 1613B 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 ATPs. That is, the matrix-specific extraction procedures in these methods are the same. In these 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.

6. Will SGS AXYS 16130 and Pace Analytical Method PAM-16130-SSI become EPA-approved methods?
   
   SGS AXYS ATM 16130 and Pace Analytical Method PAM-16130-SSI need to go through the same approval process as any other ATP that has been positively reviewed for nationwide use. The EPA will have to propose the ATPs in a future regulatory action that adds them 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 these ATPs will not be approved if there are any adverse public comments that cannot be addressed in the EPA’s formal Response to Comments document. If the EPA has not received any unresolvable public comments regarding the ATPs, then the SGS AXYS ATM 16130 and Pace Analytical Method PAM-16130-SSI will be included in the final MUR and approved and added to the relevant table at §136.3.
7. 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 and Pace Analytical Method PAM-16130-SSI are not yet approved methods. 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 its ATP using either an interlaboratory validation or side-by-side validation comparing Method 1613B and the proposed ATP for review by the EPA.
    
8. Can SGS AXYS Method ATM 16130 and Pace Analytical Method PAM-16130-SSI be used for reporting results for drinking water compliance monitoring?
   
   No, the SGS AXYS Method ATM 16130 and Pace Analytical Method PAM-16130-SSI were submitted and reviewed as ATPs 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.
9. 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 names of the methods “SGS AXYS Method ATM 16130” or “PAM-16130-SSI” should be identified that way in any applications for limited-use approval and for any subsequent reports and correspondence. The fact that the ATP applicants’ names are in the name of the methods is not unusual or unprecedented and is intended to clearly identify the analytical methods that were submitted for review as an ATP for nationwide-use and the organizations responsible for the method.