No PFAS were detected in any of the 4 samples EPA's program collected.
Oak Park Water Service is a public water system drawing on surface water, based in Westlake Village, California, serving about 13,898 people. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 4 times across 1 sampling point between Sep 2024 and Jun 2025.
None of the 29 PFAS were found at or above EPA's minimum reporting levels (2 to 20 ppt depending on the compound).
Not detected: PFEESA, PFHxS, ADONA, PFOS, PFNA, PFDA, PFDoA, PFHxA, PFUnA, 11Cl-PF3OUdS, 9Cl-PF3ONS, PFOA, HFPO-DA, PFBA, 6:2 FTS, 4:2 FTS, 8:2 FTS, PFMPA, PFMBA, NFDHA, PFPeS, PFHpS, PFHpA, PFPeA, NMeFOSAA, PFTrDA, PFTA, PFBS, NEtFOSAA.
Lithium, tested in the same program: highest 9.8 ppb, detected in 1 of 4 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.
No PFAS action is needed on these results. If your water tastes or smells of chlorine, a whole-house city water filter is the usual fix.
All 707 tested systems in California
91377
As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.
Well & Tap. "PFAS in Oak Park Water Service water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID CA5610043. https://wellandtap.com/pfas/california/oak-park-water-service/
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID CA5610043). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
