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Federal Register / Vol. 86, No. 40 / Wednesday, March 3, 2021 / Rules and Regulations Action Plan to assist states and communities with PFAS contaminated drinking water, EPA will continue to prioritize regulatory determinations of additional PFAS in drinking water. The Agency is committing to making regulatory determinations in advance of the next SDWA deadline for additional PFAS for which the Agency has a peer reviewed health assessment, has nationally representative occurrence data in finished drinking water, and has sufficient information to determine whether there is a meaningful opportunity for health risk reduction for persons served by public water systems.
EPA is currently developing scientifically rigorous toxicity assessments for seven PFAS chemicals.
The chemicals currently undergoing assessment include PFBS, PFBA, PFHxS, PFHxA, PFNA, PFDA, and HFPODA GenX chemicals, all of which are currently scheduled to be completed by 2023. These assessments all include public comment periods, independent scientific external peer review, and a robust interagency review process. Furthermore, these toxicity assessments will provide critical health information for PFAS with varying chain lengths and functional groups.
When complete, these assessments will summarize available scientific information regarding the anticipated human dose-response relationship for these chemicals, which is a key information need for informing a variety of Agency decisions.
To inform EPAs understanding of PFAS occurrence in drinking water as discussed in EPAs PFAS Action Plan USEPA, 2019b, the Agency is also leading efforts to gather additional monitoring data for 29 PFAS
contaminants in finished drinking water. EPA recently announced its proposal for nationwide drinking water monitoring for PFAS under the next UCMR monitoring cycle UCMR 5
utilizing Methods 537.1 and 533 to detect more PFAS chemicals and at lower reporting limits than previously possible.
EPA is also is generating new PFAS
toxicology data for a much larger set of less-studied PFAS through new approach methods NAMs 4 such as high throughput screening, computational toxicology tools, and chemical informatics for chemical prioritization, screening, and risk assessment. EPA will continue research 4 New approach methods NAMs refer to any technologies, methodologies, approaches, or combinations thereof that can be used to provide information on chemical hazard and potential human exposure that can avoid or significantly reduce the use of testing on animals.

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on methods for using these data to support risk assessments using NAMs such as read-across i.e., an effort to predict biological activity based on similarity in chemical structure and transcriptomics i.e., a measure of changes in gene expression in response to chemical exposure or other external stressors, and to make inferences about the toxicity of PFAS mixtures that commonly occur in real world exposures. This research can inform a more complete understanding of PFAS
toxicity for the large set of PFAS
chemicals without conventional toxicity data and can allow prioritization of actions to potentially address groups of PFAS. For additional information on the NAMs for PFAS toxicity testing, please visit: https www.epa.gov/chemicalresearch/pfas-chemical-lists-and-tieredtesting-methods-descriptions. These EPA actions, in addition to other research, may provide useful information for future EPA evaluations of additional PFAS.
a Summary of Public Comments on Considerations for Additional PFAS and Agency Responses EPA requested comment on potential regulatory constructs the Agency may consider for PFAS chemicals including PFOA and PFOS. EPA specifically requested input on a regulatory approach to evaluate PFAS by different grouping approaches.
EPA received multiple comments on how the Agency could consider additional PFAS for potential future rulemaking. Many commenters support a class-based approach for regulating PFAS based on one or more characteristics such as chain length, functional group, treatment processes, health effects, toxicity, common analytical methods, and/or shared occurrence with other contaminants within a group. Additionally, many commenters also urge EPA to make additional regulatory determinations for PFAS that have a proposed or final drinking water standard in at least one state; PFAS that have been measured in water systems through monitoring programs such as UCMR; and/or PFAS
for which EPA or the Agency for Toxic Substances and Disease Registry ATSDR has established a toxicity value. Some commenters suggest that EPA should make positive regulatory determinations for PFHxS and PFNA as well as in combination with PFOA, PFOS, and other PFAS such as PFBS.
Many commenters recommend EPA
consider various grouping and treatment technique approaches for PFAS beyond PFOA and PFOS that may not have sufficient health and occurrence data.

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Some of these commenters recommend approaches that consider acute and chronic health effects, long-term compared to short-term exposures, exposures during sensitive lifestages, and type of water systems and vulnerable populations such as vulnerable workers. Many commenters stated that the data may not be robust enough for each PFAS and therefore support a class-based approach for regulating PFAS in drinking water. In contrast, two commenters did not support a class-based approach for regulating PFAS. In summary, these commenters suggest that regulation without assessing each chemicals individual traits would be contrary to the intent of SDWA and that the Agency should address outstanding data and knowledge gaps regarding PFAS of concern prior to determining a regulatory grouping approach.
With respect to comments received on regulatory determinations for additional PFAS compounds other than PFOA and PFOS, EPA remains committed to filling information gaps by completing peer reviewed health assessments where appropriate and collecting nationally representative occurrence data. As discussed above, in response to public comments advocating timely regulation of additional PFAS in drinking water, where sufficient information is available, EPA intends to make regulatory determinations for additional PFAS prior to the fifth Regulatory Determinations statutory deadline 2026.
The Agency acknowledges many commenters support for a class-based approach for regulating PFAS and appreciates commenter recommendations regarding potential regulatory constructs. EPA
acknowledges commenters recommendations to evaluate whether PFAS can be regulated as groups, and the Agency is developing the science necessary to consider whether such regulation is necessary and appropriate for PFAS. Regarding commenters assertions that regulation without assessing each chemicals individual traits would be contrary to the intent of SDWA, the Agency notes that the Safe Drinking Water Act establishes a robust scientific and public participation process that guide EPAs development of regulations for unregulated contaminants that may present a risk to public health.
Regulation by groups is a regulatory strategy that is already used for certain regulated contaminants like disinfection byproducts, polychlorinated biphenyls, and radionuclides. EPA will continue to use best available science and available
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