Is there PFAS in Gswc-south Arcadia water?

Yes. EPA's final UCMR 5 results show Gswc-south Arcadia averaged 20.0 ppt of PFOS at its worst sampling point, 5.0 times the EPA limit of 4 ppt.

Gswc-south Arcadia is a public water system drawing on groundwater, based in San Dimas, California, serving about 27,072 people, including Arcadia, Duarte, Monrovia, El Monte, San Gabriel, Temple City. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 10 times across 5 sampling points between Sep 2023 and Jul 2024.

Every PFAS detected

Not detected: 8:2 FTS, PFHpA, 4:2 FTS, NFDHA, PFMPA, PFPeA, PFMBA, PFEESA, PFPeS, PFHpS, NEtFOSAA, NMeFOSAA, PFTA, 6:2 FTS, 11Cl-PF3OUdS, PFTrDA, PFBA, ADONA, PFDA, PFDoA, PFHxA, PFUnA, 9Cl-PF3ONS, PFBS, HFPO-DA, PFNA.

Lithium, tested in the same program: not detected.

What the EPA limits mean here

In April 2024 EPA set enforceable limits of 4 ppt for PFOA and PFOS, 10 ppt each for PFHxS, PFNA and GenX, and a hazard index of 1 for mixtures. Utilities were given until 2029 to comply. In May 2026 EPA proposed keeping only the PFOA and PFOS limits and moving that deadline to 2031. Until that proposal is final, the 2024 limits stand.

Compliance is judged on a running annual average at each entry point, so we show the average at this system's worst sampling point next to its single highest result. UCMR 5 results do not by themselves put a utility in or out of compliance.

What you can do at home

Two routes work for PFAS. For drinking and cooking water only, a reverse osmosis system certified to NSF/ANSI 58 with a PFOA/PFOS reduction claim is the cheapest proven option. To treat every tap and shower, a whole-house carbon system with enough contact time works, but check that the maker has PFAS test data, not just a marketing claim. See the best filters for PFAS and how PFAS removal works.

Other systems in California

• City of Eureka none detected
• City of Benicia 3 PFAS detected
• City of Lemoore none detected
• City of Dinuba none detected
• City of Brawley none detected
• Placer Cwa - Auburn/bowman none detected

All 707 tested systems in California

ZIP codes served

91006 91007 91010 91016 91731 91776 91780

As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.

Cite this page

Well & Tap. "PFAS in Gswc-south Arcadia water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID CA1910212. https://wellandtap.com/pfas/california/gswc-south-arcadia/

About this data

Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID CA1910212). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.