Monitored — not federally regulated
PFBS
Perfluorobutane sulfonic acid
Introduced as a shorter-chain PFOS replacement after 3M phased out PFOS in 2002. The shorter chain clears the body faster but is harder to filter out of water.
01Health effects
Linked outcomes
- · Thyroid disruption
- · Reproductive toxicity
- · Kidney effects
- · Developmental harm in animal studies
Organs affected
Thyroid, kidneys, reproductive system
Effects above are summarized from EPA, NIH/NTP, ATSDR, and IARC documentation. Not a clinical or medical claim — see our sourcing standards.
02Where it comes from
Used as a replacement for PFOS in industrial applications. Found in Scotchgard reformulations, firefighting foam alternatives, and semiconductor manufacturing wastewater.
03Regulatory status
EPA issued a health advisory of 2,000 ppt in 2022. Minnesota set a state MCL of 100 ppt. Under active EPA review for federal regulation.
04What you can do
If PFBS was detected in your water supply, two filter technologies reliably remove it at the tap:
- RO (reverse osmosis) under-sink systems — 90–99.9% removal across all PFAS chain lengths. Look for NSF/ANSI 58 certification.
- GAC (granular activated carbon) block filters — effective for long-chain PFAS; less reliable for short-chain compounds. Look for NSF/ANSI 53 with NSF P473.
See our certified-filter picks or read the in-depth PFAS removal guide.
Related compounds
Other monitored compounds
- PFHxA →
Perfluorohexanoic acid
One of the most frequently detected PFAS in US drinking water and a common degradation product of fluorotelomer chemistry used in food packaging and stain protection. Its short chain length makes it especially hard to remove with activated carbon filters.
- PFBA →
Perfluorobutanoic acid
Very short half-life in the body (3–4 days) compared to PFOA (years), but still persistent in the environment. Often the final breakdown product when longer-chain PFAS degrade.
- PFDA →
Perfluorodecanoic acid
A long-chain PFAS with an estimated human half-life of 7–12 years — among the most persistent compounds in the body of any monitored PFAS. Frequently detected in human blood samples even decades after primary uses ended.
- PFUnA →
Perfluoroundecanoic acid
One of the longest-chain PFAS in the UCMR 5 monitoring set — extremely persistent in both the environment and the human body. Often used by researchers as a marker of fluoropolymer manufacturing emissions.