Perfluorooctane Sulfonate (PFOS)CAS 1763-23-1
The other big long-chain PFAS — immune suppression, half-life 5-8 years, Stockholm Convention POP.
Toxic Chemical Databases
Substance-specific listings — these flags are for Perfluorooctane Sulfonate alone, not for the broader family.
Chemical Type
Long-Chain C8 Perfluoroalkyl Sulfonate
Chemical Description
PFOS was the active ingredient in Scotchgard and a key constituent of AFFF firefighting foam until 3M phased out production in 2002. Stockholm Convention added PFOS to its POPs list in 2009 — only the second PFAS so listed. The immune-suppression endpoint is the strongest signal — multiple human cohort studies show reduced antibody response to childhood vaccinations. Human serum half-life is even longer than PFOA (5-8 years).
Biological Activity
Severity scores specific to this substance, NOT the parent family average. Differences between siblings are real and meaningful.
Top Health Consequences
- Reduced antibody response to vaccines (well-replicated immune signal)
- Thyroid hormone disruption
- Elevated cholesterol
- Stockholm Convention POP — global ban with exemptions
- Bioaccumulation with 5-8 year human serum half-life
Pathways of Exposure
- Drinking water contamination near military bases and airports
- Legacy stain-treatment exposure from older carpets and upholstery
- Diet — bioaccumulated load in fish
- AFFF firefighting foam residuals at industrial sites
Building Materials with Perfluorooctane Sulfonate
Listed alphabetically — product categories where this specific substance appears.
Legacy Stain-Resistant Carpet
Legacy Stain-Resistant Upholstery
Specialty Surface Treatments
How We Keep Perfluorooctane Sulfonate Out of a House
Perfluorooctane Sulfonate is on our avoid list, which means it is specified out of the project before bidding — not caught on site. Keeping chemistry like this out of the house is the practical difference between a healthy home and an ordinary one.
If you want a house specified this way from the start, or an existing house assessed for what is already in it, that is the work we do. Earth Bound Homes builds in Menlo Park, Redwood City, San Mateo County and across the San Francisco Bay Area.