Perfluorobutane Sulfonate (PFBS, C-4)CAS 375-73-5
Short-chain sulfonate replacement for PFOS — touted as safer, REACH SVHC anyway.
Toxic Chemical Databases
Substance-specific listings — these flags are for Perfluorobutane Sulfonate alone, not for the broader family.
Chemical Type
Short-Chain C4 Perfluoroalkyl Sulfonate
Chemical Description
PFBS is the four-carbon sulfonate analog of PFOS. Industry shifted to PFBS as PFOS came under regulatory pressure. Shorter chain reduces bioaccumulation (human half-life ~26-40 days vs PFOS's 5-8 years), but PFBS is still environmentally persistent and mobile in groundwater. EU REACH added it to the SVHC Candidate List in 2019 for persistence and mobility concerns.
Biological Activity
Severity scores specific to this substance, NOT the parent family average. Differences between siblings are real and meaningful.
Top Health Consequences
- Thyroid hormone disruption in developmental rodent studies
- REACH SVHC for persistence, mobility, and toxicity
- Environmental persistence indistinguishable from PFOS
- Rising groundwater detections
Pathways of Exposure
- Drinking water contamination near firefighting-foam release sites
- Inhalation of degradation products from C-8 sulfonates
Building Materials with Perfluorobutane Sulfonate
Listed alphabetically — product categories where this specific substance appears.
Modern AFFF Replacement Foam Residuals
Replacement Stain Treatments
How We Keep Perfluorobutane Sulfonate Out of a House
Avoiding Perfluorobutane Sulfonate is only half of it. The replacement has to work in a mold free, airtight, PHPP-modeled assembly as well — and finding materials that do both is most of what we do.
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 Los Gatos, San Jose, Santa Clara County and across the San Francisco Bay Area.