Regulatory Determination 5
The Safe Drinking Water Act (SDWA), as amended in 1996, directs the EPA to publish a list of contaminants (referred to as the Contaminant Candidate List, or CCL) to assist in priority-setting efforts. The SDWA also directs the EPA to select no fewer than five contaminants from the current CCL and determine whether to regulate these contaminants with a National Primary Drinking Water Regulation (NPDWR). A regulatory determination is a decision on whether the EPA should initiate a rulemaking process to develop an NPDWR for a specific contaminant.
Final Regulatory Determinations for Contaminants on the Fifth Contaminant Candidate List
On March 17, 2026, the EPA issued a final determination that nine of these contaminants do not meet the criteria for regulation development established by SDWA. The decision for each of these nine contaminants is being made because they are not commonly found in drinking water at levels and at a frequency of concern. As a result, EPA will not develop regulations for 2-aminotoluene, cylindrospermopsin, ethoprop, microcystins, molybdenum, permethrin, profenofos, tebuconazole, and tribufos.
On January 15, 2025, the EPA announced the preliminary determinations not to regulate these nine CCL 5 contaminants and requested public comment on these determinations.
Federal Register Notices
- Federal Register Notice (Pre-publication version): Announcement of Final Regulatory Determinations for Contaminants on the Fifth Drinking Water Contaminant Candidate List (pdf)
- Federal Register Notice: Announcement of Preliminary Regulatory Determinations for Contaminants on the Fifth Drinking Water Contaminant Candidate List
Supporting Materials
- The Final Regulatory Determination 5 Support Document (pdf)
- Responses to Public Comments on Preliminary Regulatory Determinations for Contaminants on the Fifth Drinking Water Contaminant Candidate List (pdf)
- Additional Supporting Documents for Regulatory Determination 5 are available on www.regulations.gov: Docket ID No. EPA-HQ-OW-2024-0456.