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PFBS in drinking water

Also called Perfluorobutane sulfonic acid, Perfluorobutanesulfonic acid.

Legal limit
None
Health goal
None
Federal benchmark
EPA health-based water concentration used in the Hazard Index (not an MCL): 2,000 ppt

Values in parts per trillion (ppt). Comes from the source.

Limits checked Oct. 4, 2026

Where the rules stand

No individual MCL. Under the April 26, 2024 rule, PFBS counts only toward the Hazard Index, when it occurs with PFHxS, PFNA or HFPO-DA. On May 20, 2026, EPA proposed rescinding the Hazard Index. Comments closed July 20, 2026. As of Oct. 4, 2026, the Federal Register shows no final rule, so the Hazard Index still stands.

The scale every TapBuff report uses for this contaminant: the legal line at the middle, twice it at the right.

Is it in your water?

Matched to your utility using EPA records.

What EPA says about health

EPA based its 2,000 ppt health-based water concentration on thyroid effects. That level is used inside the Hazard Index, not as a limit on its own.

Where it comes from

PFAS have been used since the 1940s in products like nonstick cookware, food packaging, waterproof clothing, stain-resistant furniture and firefighting foam. They last a long time in the environment and can reach drinking water sources.

What EPA found nationally

Under UCMR 5, EPA tested 9,944 utilities for PFBS. It was found at 1,672 of them, which report serving 86 million people. The highest single sample was 290 ppt.

Highest single results for PFBS
UtilityHighest sampleFound in
CalhounCalhoun, GA · serves 53,090290 ppt8 of 8
Newton Falls CityNewton Falls, OH · serves 6,109220 ppt4 of 4
City of Gadsden, the Wwsb of theGadsden, AL · serves 44,637155 ppt4 of 4
Chattooga CountyTrion, GA · serves 9,190150 ppt10 of 14
City of SaffordSafford, AZ · serves 20,600144 ppt12 of 12
Northeast Etowah County Water Co - OpGadsden, AL · serves 4,275140 ppt4 of 4
Highland Water AuthorityGadsden, AL · serves 3,963134 ppt4 of 4
West Etowah Water & Fire Pro AuthorityAttalla, AL · serves 6,900120 ppt3 of 6
Shelby County Commission - Water ServicesColumbiana, AL · serves 40,101114 ppt8 of 8
City of GlobeGlobe, AZ · serves 7,536113 ppt2 of 6
Highest single sample per utility, EPA UCMR 5 file of Aug. 27, 2026. One high sample is not a violation; compliance is judged on averages over time.

What handles it

  • NSF/ANSI 53

    Claim to look for: Total PFAS Reduction

    NSF listing footnotes include PFBS in Total PFAS. No single-compound PFBS claim was found on NSF or WQA listings.

Filters with that claim on a certifier’s listing

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Sources

  1. Per- and Polyfluoroalkyl Substances (PFAS): Final PFAS National Primary Drinking Water Regulation, U.S. EPA. Checked Oct. 4, 2026.
  2. PFAS National Primary Drinking Water Regulation (final rule, April 26, 2024), Federal Register. Checked Oct. 4, 2026.
  3. Rescission of Regulatory Determinations and Removal of Related Provisions for Four PFAS Substances (proposed rule, May 20, 2026), Federal Register. Checked Oct. 4, 2026.
  4. Proposed PFAS Rescission Rule, U.S. EPA. Checked Oct. 4, 2026.
  5. Federal Register: EPA documents mentioning PFAS, newest first (no final rule on either 2026 proposal), Federal Register. Checked Oct. 4, 2026.
  6. The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary: July 2026 (EPA 815-S-26-007), U.S. EPA. Checked Oct. 4, 2026.
  7. NSF listings for the NSF/ANSI 53 "Total PFAS Reduction" claim (footnotes define Total PFAS), NSF. Checked Oct. 4, 2026.
  8. Find WQA Certified Products (Gold Seal listings by standard and claim), Water Quality Association. Checked Oct. 4, 2026.
  9. SDWA Dataset Download Summary (codes from SDWA_REF_CODE_VALUES.csv, 2026 Q2 extract), U.S. EPA ECHO. Checked Oct. 4, 2026.

Where to go next

  • NSF/ANSI 53, decoded

    What a NSF/ANSI 53 listing covers, and the claim to look for.

    About NSF/ANSI 53

  • Filters, checked

    Every filter TapBuff has checked against a certifier’s listing, with five-year costs.

    Compare filters

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