Human Health Toxicity Assessment for Perfluorooctane Sulfonic Acid (PFOS)

The U.S. Environmental Protection Agency has finalized the human health toxicity assessment for Perfluorooctane Sulfonic Acid (PFOS) and related salts. The final toxicity assessment was published at the time of finalization of the Per- and Polyfluoroalkyl Substances (PFAS) National Primary Drinking Water Regulation (NPDWR).

The PFOS toxicity assessment provides hazard identification, dose-response information, and derives toxicity values called oral reference doses (RfDs) and cancer slope factors (CSFs). The assessment underwent external peer review by the EPA’s Science Advisory Board (SAB) and public comment. Policy makers can use the PFOS toxicity assessment along with exposure information and other important considerations to determine if, and when, it is appropriate to take action to reduce exposure to PFOS.

Final PFOS Toxicity Assessment Documents

• Human Health Toxicity Assessment of Perfluorooctane Sulfonic Acid (PFOS) and Related Salts (pdf) (16.05 MB, April 2024, 815-R-24-007)
• Appendix: Human Health Toxicity Assessment of Perfluorooctane Sulfonic Acid (PFOS) and Related Salts (pdf) (17.04 MB, April 2024, 815-R-24-009)

PFOS Toxicity Assessment Summary

• Infographic Fact Sheet: Human Health Toxicity Assessment for Perfluorooctane Sulfonic Acid (PFOS) (pdf) (183.18 KB, January 2025, 822-F-25-002)

EPA Response to Comments on Draft PFOS Toxicity Assessments

In August 2022, the SAB PFAS panel provided final recommendations on four draft documents supporting development of the EPA’s PFAS NPDWR. One of the four documents was the 2021 Draft Proposed Approaches to the Derivation of a Draft Maximum Contaminant Level Goal for Perfluorooctane Sulfonic Acid (PFOS) (CASRN 1763-23-1) in Drinking Water, the first draft of the PFOS toxicity assessment. In March 2023, the EPA published its response to those recommendations:

• EPA Response to Final Science Advisory Board Recommendations (August 2022) on Four Draft Support Documents for the EPA’s Proposed PFAS National Primary Drinking Water Regulation

The 2023 draft toxicity assessment for PFOS, which addressed the recommendations provided by the SAB PFAS Review Panel, was released for a 60-day public comment period in March 2023 along with the Proposed PFAS NPDWR. In April 2024, the EPA published its response to public comments:

• Responses to Public Comments on PFAS NPDWR Rulemaking (pdf) (22.3 MB, 815R24005)

Previous Drafts of the PFOS Toxicity Assessment

• 2021 Draft Proposed Approaches to the Derivation of a Draft Maximum Contaminant Level Goal for Perfluorooctane Sulfonic Acid (PFOS) (CASRN 1763-23-1) in Drinking Water
• 2023 PUBLIC COMMENT DRAFT Toxicity Assessment and Proposed Maximum Contaminant Level Goal for Perfluorooctane Sulfonic Acid (PFOS) in Drinking Water
• 2023 PUBLIC COMMENT DRAFT Appendix: Toxicity Assessment and Proposed Maximum Contaminant Level Goal for Perfluorooctane Sulfonic Acid (PFOS) in Drinking Water