IRIS Toxicological Review of Perfluorohexanesulfonic Acid (Pfhxs) and Related Salts (Final Report, 2025)

IRIS

Perfluorohexanesulfonic Acid (PFHxS)

CASRN 355-46-4 | DTXSID7040150

Toxicological Review (PDF) (493 pp, 22.9 MB)
IRIS Summary (PDF) (6 pp, 403.3 KB)

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Overview
Background
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Notice

EPA announced the release of the IRIS Toxicological Review Perfluorohexanesulfonic Acid (PFHxS)and Related Salts. The interagency comments on the IRIS Interagency Science Discussion Draft were also released.

Overview

EPA has finalized the IRIS Toxicological Review of Perfluorohexanesulfonic Acid (PFHxS) and Related Salts. This assessment addresses the potential cancer and noncancer human health effects from exposure to PFHxS and related salts. EPA’s program and regional offices may use this assessment to inform decisions to protect human health.

Citation

U.S. EPA. IRIS Toxicological Review of Perfluorohexanesulfonic Acid (Pfhxs) and Related Salts (Final Report, 2025). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-25/012, 2025.

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Background

Perfluorohexanesulfonic Acid (PFHxS) and its related salts are members of the group of per and polyfluoroalkyl substances (PFAS). PFAS are not naturally occurring in the environment; they are man-made compounds that have been used widely over the past several decades in consumer products and industrial applications because of their resistance to heat, oil, stains, grease, and water. Concerns about PFHxS and other PFAS stem from the resistance of these compounds to hydrolysis, photolysis, and biodegradation, which leads to their persistence in the environment.

PFHxS is used in water- and stain-protective coatings for consumer products such as carpets, textiles, paper (including food-contact), packaging (including food-contact), textiles, and electronics. It has been used industrially as a surfactant to make fluoropolymers, as a surfactant or surface protection agent for cleaning and polishing products, and in other industrial fluids or water-proofing agents. It may also be present unintentionally as an impurity from industrial production processes. PFHxS has also been used in aqueous film-forming foam (AFFF) for fire suppression.

History/Chronology

Date	Description
01- Nov 2019	EPA released the Systematic Review Protocol for the PFHxS IRIS Assessment (Preliminary Assessment Materials). [Federal Register Notice Nov 8, 2019]
02- Jul 2020	EPA released an update to the Systematic Review Protocol for the PFBA, PFHxA, PFHxS, PFNA, and PFDA IRIS Assessments in response to public comments.
03- Jan 2023	EPA sent an interagency science consultation PFHxS draft for review and comment.
04- Jul 2023	EPA released the draft IRIS Toxicological Review of Perfluorohexanesulfonic Acid (PFHxS) and Related Salts for a 60-day public comment period and external peer review. EPA also released the interagency science consultation comments from reviewers. [Federal Register Notice: July 24, 2023]
05- Feb/Mar 2024	ERG, an independent contractor to the EPA, hosted multiple external peer review meetings for the review of the Integrated Risk Information System (IRIS) Assessment for PFHxS in late Febraury and early March.
06- Jul 2024	EPA posted the final peer review report from the contractor on the EPA website.
07- Nov 2024	EPA submitted the revised interagency science discussion draft for final Agency and Interagency review.
08- Jan 2025	EPA posted the final report IRIS Toxicological Review of Perfluorohexanesulfonic Acid (PFHxS) and Related Salts, released the interagency science discussion draft comments on the IRIS website, and updated key IRIS values for PFHxS in the IRIS database.

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This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

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