PFOS (Perfluorooctane sulfonic acid)
PFAS ("forever chemical")
Firefighting foam (AFFF), industrial discharge, stain- and water-repellent products, landfill leachate.
EPA regulatory status
Legal limit (MCL)
4 ppt
Goal (MCLG)
0 ppt
MCL 4.0 ppt (ng/L), finalized April 2024. MCLG = 0. Initial monitoring by 2027; treatment/compliance by 2029. EPA's May 2025 plan proposes to UPHOLD the PFOS MCL with an optional extension to 2031 — proposed, not final; the 2024 rule remains in force.
Health effects
Linked to cancer, liver and thyroid effects, immune suppression, high cholesterol, and developmental effects. Bioaccumulates; a 'forever chemical.'
This is general public-health information, not medical advice — consult your physician with any health concerns.
National violations
0
EPA's enforcement data (SDWIS/ECHO) records zero violations of PFOS (Perfluorooctane sulfonic acid)'s rule nationally. See this contaminant's regulatory status above for its current standard and compliance timeline — a zero count is not necessarily an all-clear.
How to remove PFOS (Perfluorooctane sulfonic acid)
anion exchange
NSF/ANSI 53
Frequently asked questions
What is PFOS (Perfluorooctane sulfonic acid)?
PFOS (Perfluorooctane sulfonic acid) is a PFAS ("forever chemical") regulated in US drinking water. Firefighting foam (AFFF), industrial discharge, stain- and water-repellent products, landfill leachate.
What is the legal limit for PFOS (Perfluorooctane sulfonic acid) in drinking water?
MCL 4.0 ppt (ng/L), finalized April 2024. MCLG = 0. Initial monitoring by 2027; treatment/compliance by 2029. EPA's May 2025 plan proposes to UPHOLD the PFOS MCL with an optional extension to 2031 — proposed, not final; the 2024 rule remains in force.
What health effects does PFOS (Perfluorooctane sulfonic acid) have?
Linked to cancer, liver and thyroid effects, immune suppression, high cholesterol, and developmental effects. Bioaccumulates; a 'forever chemical.'
How many violations of PFOS (Perfluorooctane sulfonic acid) limits are on record nationally?
EPA's enforcement data (SDWIS/ECHO) records zero violations of PFOS (Perfluorooctane sulfonic acid)'s rule nationally. See this contaminant's regulatory status above for its current standard and compliance timeline — a zero count is not necessarily an all-clear.
How do I remove PFOS (Perfluorooctane sulfonic acid) from my water?
Filter technologies certified to reduce PFOS (Perfluorooctane sulfonic acid) include: reverse osmosis (NSF/ANSI 58), activated carbon (NSF/ANSI 53 (formerly P473)), anion exchange (NSF/ANSI 53). Look for a filter independently certified against the specific NSF/ANSI standard for this contaminant — general "reduces contaminants" marketing claims are not the same as a contaminant-specific certification.
Source: EPA National Primary Drinking Water Regulations · Data as of 2026-07-16