Six-Year Review 4 Frequent Questions and Answers
Why did EPA conduct a review of the National Primary Drinking Water Regulations (NPDWRs)?
The 1996 Safe Drinking Water Act (SDWA) Amendments require EPA to conduct a review every six years of existing national primary drinking water regulations and determine which, if any, need to be revised. This requirement is contained in Section 1412(b)(9) of SDWA, which reads:
The Administrator shall, not less often than every 6 years, review and revise, as appropriate, each national primary drinking water regulation promulgated under this title. Any revision of a national primary drinking water regulation shall be promulgated in accordance with this section, except that each revision shall maintain, or provide for greater, protection of the health of persons.
What NPDWRs are covered by this action?
The Six-Year Review process only applies to existing national primary drinking water regulations (NPDWRs) (i.e., currently regulated contaminants/parameters). Unregulated contaminants, such as those listed on the Contaminant Candidate List (CCL), are not covered by the Six-Year Review. The current review specifically focused on all current NPDWRs with the exception of the per-and polyfluoroalkyl substances (PFAS) regulations.
EPA did not include in this Six-Year Review cycle the PFAS regulations that were promulgated in April 2024, and which established six new NPDWRs. The EPA anticipates that once the PFAS regulations go into effect and sufficient information regarding compliance monitoring becomes available, those NPDWRs will be subject to a more detailed regulatory review under a future Six-Year Review cycle.
How did EPA review the NPDWRs under Six-Year Review 4?
A detailed description of the process the Agency used to review the NPDWRs is documented in the “EPA Protocol for the Fourth Review of Existing National Primary Drinking Water Regulations.” The foundation of this protocol was developed for the Six-Year Review 1 based on the recommendations of the National Drinking Water Advisory Council and has undergone minor clarifications during each Six-Year Review cycle. The Six-Year Review 4 process is very similar to the process implemented during the previous three cycles of Six-Year Review.
The protocol for the Six-Year Review 4 is broken down into a series of questions that can inform a decision about the appropriateness of revising an NPDWR. These questions are structured into a decision tree related to the following review elements considered for each NPDWR during the Six-Year Review 4: initial review, health effects, analytical feasibility, occurrence and exposure, treatment feasibility, and other regulatory revisions.
What are the impacts of the review results from Six-Year Review 4?
This action does not change or add to existing regulatory requirements, and no new requirements will be imposed by this action. Instead, it notifies interested parties of EPA’s review of existing NPDWRs and the Agency’s conclusions that none of these rules warrant new regulatory action at this time.
Will EPA consider reviewing any NPDWRs before the next review cycle?
If the result of an ongoing health risk assessment or the resolution of data gaps/research needs indicate that significant or compelling new information becomes available that will change the basis for an NPDWR, the Agency may decide to accelerate the review schedule for a particular NPDWR.
Where can I find more information about this notice and the Six-Year Review?
For information on the Six-Year Review, please visit the EPA internet website, https://www.epa.gov/dwsixyearreview.
For general information on drinking water, please visit the EPA Office of Ground Water and Drinking Water website at https://www.epa.gov/ground-water-and-drinking-water.