EPA Releases Final IRIS Toxicological Review of Hexavalent Chromium [Cr(VI)]

On August 1, EPA released the final Intergrated Risk and Information System (IRIS) toxicological review of hexavalent chromium (Cr-VI). Based on this release and a prior settlement agreement with Waterkeepers Alliance, et al., EPA is now required to make a regulatory determination by August 1, 2027 (within three years of August 1, 2024) as to whether the existing National Primary Drinking Water Regulation (NPDWR) for chromium is appropriate for revision based on the final IRIS assessment. This regulatory action would likely be an “off-cycle” regulatory determination, since, on February, 22, 2021, EPA issued the final regulatory determinations for contaminants on the Fourth Contaminant Candidate List (CCL 4). Given the five-year cycle for regulatory determinations, the fifth cycle of regulatory determinations are scheduled to be released by February 22, 2026, which is approximately a year-and-a-half prior to the deadline for a regulatory determination for hexavalent chromium.