PFBS

Perfluorobutane sulfonate

1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonic acid

Also known as PFBS

perfluorobutanesulfonic acidNonafluoro-1-butanesulfonic acidNonafluorobutanesulfonic acidNonafluorobutane-1-sulfonic acid1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonic acid1-Perfluorobutanesulfonic acid1,1,2,2,3,3,4,4,4-Nonafluoro-1-butanesulfonic acid1FV02N6NVO

A short-chain perfluoroalkyl sulfonic acid (PFSA) — among the most-detected PFAS in U.S. drinking water (4,285 utilities, 99M served). 3M's chosen PFOS-replacement chemistry post-2002; regulated as part of the NPDWR Hazard Index mixture.

Chemistry

CAS 375-73-5

Formula C4HF9O3S

Mol. weight 300.10 g/mol

Solubility 510 mg/L

Serum half-life 26 days

Group PFAS · short-chain-pfsa

Chemistry — what these mean

CAS: CAS Registry Number — a unique numeric ID assigned by the Chemical Abstracts Service. Every chemical has one, and it's the universal lookup key across regulatory and scientific databases.
Formula: The contaminant's molecular formula — the count of each atom in one molecule (e.g. C8HF15O2 means 8 carbon, 1 hydrogen, 15 fluorine, 2 oxygen atoms). Used to identify the compound in chemistry references.
Mol. weight: Molecular weight — the total mass of one molecule in grams per mole. Used to convert between mass-based and concentration-based measurements.
Solubility: How much of the contaminant will dissolve in water before saturating. Higher solubility means it travels easily with water; lower solubility means it tends to bind to particles or settle out.
Serum half-life: The time it takes for the body to clear half of a given dose from the blood. A multi-year half-life (typical for many PFAS) means even brief exposure accumulates over time.
Group: The chemical family this contaminant belongs to — e.g. PFAS, disinfection byproducts, heavy metals. Contaminants in the same group often share treatment options and regulatory approach.

Regulatory limits

Values in ppt (parts per trillion)

Status: Under review

Detection limit 3 ppt

Regulatory limits — what these mean

Proposed status: Where the regulation sits in the EPA process — enforced (in force), proposed (awaiting finalization), under review, or withdrawn. A proposed limit is not legally binding yet, but it signals where regulation is heading.
Detection limit: The lowest concentration testing equipment can reliably measure. A "non-detect" result does not mean zero — it means below this threshold. Important for ultra-trace contaminants like PFAS, where the legal limit sits near what labs can actually measure.

Occurrence

UCMR 5

2023 – 2025

Occurrence — about this data

The Unregulated Contaminant Monitoring Rule — the EPA program that tests public water systems for contaminants that are not yet federally regulated. Each cycle (UCMR 1 through 6, roughly every five years) targets a different shortlist; UCMR 5 focused on PFAS. The data informs whether the EPA later regulates those contaminants.

External databases

PubChem 67815 EPA CompTox DTXSID5030030 EPA code PFBS

External databases — what these mean

PubChem 67815: PubChem CID — the unique compound ID in the NIH's PubChem chemical database. Tap the pill to open the substance record: structure, physical properties, safety data, and links to related research.
EPA CompTox: The EPA's research-side chemical registry — the CompTox Chemicals Dashboard. Each substance gets a DTXSID identifier that links it to bioactivity data, exposure estimates, and regulatory programs.
EPA code: Internal EPA code used in SDWIS (the EPA's drinking-water records system) to identify a contaminant across compliance reports and violations. Useful for cross-referencing against state monitoring data.

Group

PFAS

Regulatory status

UCMR

Unregulated Contaminant Monitoring Rule

Top removal tech

Activated carbon

Primary concern: Hormone disruption and developmental effects

Affected organ systems

Thyroid Developmental Kidney

Health effects

Endocrine disruptor Developmental toxin

Exposure routes

Drinking water Dietary Occupational

Vulnerable populations

Pregnant Infants Children

Overview

Perfluorobutane sulfonate (PFBS) is the four-carbon perfluoroalkyl sulfonic acid — the short-chain sibling of PFOS, with the same sulfonate head group but only four perfluorinated carbons in the tail instead of eight. After 3M voluntarily phased out PFOS production in 2002, the company adopted PFBS as the lead replacement chemistry for its 'next-generation' Scotchgard line and broader sulfonamide-based stain, grease, and water repellents. The short chain gives PFBS very high water solubility, low affinity for soil and granular activated carbon, and a much shorter human serum elimination half-life (about 26 days; cf. ~5.4 years for PFOS) — but environmental persistence is essentially unchanged. The combination makes PFBS the second-highest-occurrence PFAS in UCMR 5: detected in 4,285 U.S. public water systems serving roughly 99 million people across 46 states.

Pollution sources

Industry Manufacturing Consumer products

Sources

PFBS enters drinking water through three principal pathways: (1) direct industrial discharges and disposal-site leachate from former 3M production sites and downstream textile-, paper-, and carpet-treatment licensees — including the legacy 3M Cottage Grove, Minnesota complex, where post-PFOS PFBS chemistry produced a documented groundwater plume in the Twin Cities east metro; (2) AFFF firefighting-foam release sites and military airfields where PFBS appears as both a direct ingredient in newer-generation foams and as a degradation product of older perfluoroalkyl sulfonamide chemistries; and (3) environmental transformation of short-chain fluorotelomer sulfonates used in stain-resistant consumer coatings. The highest reported U.S. concentration is Rome, GA at 210 ppt (3 of 3 tests); the most striking chronic-source pattern is the Gadsden, AL water complex (40 of 41 tests positive at 84.5 ppt) — a clear localized industrial source.

Health risks

EPA finalized an Integrated Risk Information System (IRIS) toxicity assessment for PFBS in 2021, identifying neonatal thyroid hormone disruption (decreased serum T4 in newborn mice from gestational exposure) as the dose-defining endpoint. Thyroid hormone disruption and developmental effects on fetal growth and early childhood are the principal endpoints associated with that EPA reference dose. PFBS has not been classified as a carcinogen by IARC or NTP. Although PFBS does not have its own individual federal MCL under the 2024 PFAS NPDWR, it is one of four PFAS contributing to the Hazard Index mixture rule (alongside PFHxS, HFPO-DA, and PFNA) — meaning regulated utilities must include PFBS in the mixture calculation even though the analyte itself sits at the UCMR-monitoring tier of the schema.

Effective treatments

Activated carbon Reverse osmosis

Does not remove

UV Chlorination Boil

NSF certifications

NSF/ANSI 53 Health-related contaminants NSF/ANSI 58 Reverse osmosis systems

Water treatment

Like its PFCA sibling PFBA, PFBS is one of the harder UCMR 5 PFAS to remove with granular activated carbon: the short perfluorinated chain gives only modest hydrophobic interaction with GAC media, and bed breakthrough occurs at a small fraction of the throughput needed for long-chain PFAS like PFOS. Utilities targeting PFBS should plan on anion exchange resin (selective for short-chain PFAS), reverse osmosis, or nanofiltration as the primary barrier — with GAC as a polishing or co-removal step for the broader PFAS mixture. Conventional treatment processes — coagulation, sand filtration, disinfection, UV, and ozonation — do not remove PFBS. Boiling concentrates rather than removes it. NSF/ANSI 53 and NSF P473 certify point-of-use filters for general PFAS reduction; NSF/ANSI 58 covers RO systems.

Gallery

Related contaminants

Perfluorobutanoic Acid (PFBA) A short-chain perfluorocarboxylic acid (PFCA) — among the most-detected PFAS in U.S. drinking water (3,427 utilities, 95M served). Less bioaccumulative than long-chain PFAS; no individual federal MCL. Perfluorohexane sulfonate (PFHXS) A 6-carbon long-chain PFSA with 2024 NPDWR individual MCL of 10 ppt. EPA's 2023 IRIS RfD targets developmental immune effects; detected at 3,144 utilities serving 71M people across 46 states.

Chemistry + classification data sourced from public databases (PubChem, EPA CompTox, IARC monographs); 3D molecular models from 3d.nih.gov where available.