Yes, at low levels. 1 PFAS was detected, all below EPA's 2024 limits.
Also detected, no federal limit: PFBA.
Gswc-south San Gabriel is a public water system drawing on surface water, based in San Dimas, California, serving about 26,240 people, including Monterey Park, Rosemead. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 8 times across 3 sampling points between Oct 2023 and Jul 2024.
| PFAS | Detected | Highest | Worst point avg | EPA limit |
|---|---|---|---|---|
| PFBA Perfluorobutanoic acid |
1 of 8 | 5.6 ppt | 2.8 ppt | none |
Not detected: NFDHA, 4:2 FTS, 8:2 FTS, PFMPA, PFMBA, PFEESA, 6:2 FTS, PFHpS, PFPeA, PFPeS, PFTA, PFTrDA, NEtFOSAA, HFPO-DA, PFUnA, NMeFOSAA, PFDoA, ADONA, PFHpA, PFDA, PFBS, PFHxA, 11Cl-PF3OUdS, PFNA, PFOS, PFOA, 9Cl-PF3ONS, PFHxS.
Lithium, tested in the same program: highest 57 ppb, detected in 4 of 8 samples. EPA's health-based screening level is 10 ppb.
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.
Levels here are under EPA's limits, so no treatment is required. If you want them lower anyway, a certified reverse osmosis system under the sink handles drinking water, and a whole-house carbon filter also takes out the chlorine or chloramine your utility adds.
All 707 tested systems in California
91755 91770
As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.
Well & Tap. "PFAS in Gswc-south San Gabriel water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID CA1910223. https://wellandtap.com/pfas/california/gswc-south-san-gabriel/
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID CA1910223). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
