On May 18, 2026, EPA announced two proposals that affect the federal PFAS rule we described in April 2024. The first would let water systems request a two-year extension — from 2029 to 2031 — to comply with the enforceable limits for PFOA and PFOS. The second would rescind the individual limits for three other PFAS compounds (PFHxS, PFNA, and HFPO-DA/GenX) and the combined "Hazard Index" limit for mixtures of those plus PFBS, on the grounds that EPA says the prior administration didn't follow required Safe Drinking Water Act procedure in setting them.
What doesn't change: the 4 ppt limits for PFOA and PFOS individually — the two compounds most consistently linked to health effects in research, and the one (PFOA) already detected in Weir River water above that level — are not part of either rescission proposal. What's uncertain is timing: a system could legally take until 2031 rather than 2029 to act on it.
Both proposals were still open for public comment as of this writing, with the comment period on the record scheduled to close July 20, 2026. Nothing here is final; treat the 2024 rule as the current baseline until EPA actually finalizes a change.
See the full regulatory timeline for how this fits with the 2020 state standard and the 2024 federal rule.
Until April 2024, there was no federal limit on PFAS in drinking water at all — only the Massachusetts state standard set in 2020. That changed when EPA finalized its National Primary Drinking Water Regulation (NPDWR) for PFAS: the first time PFAS compounds have been individually, enforceably regulated at the federal level.
The rule set limits of 4 parts per trillion (ppt) each for PFOA and PFOS, 10 ppt each for three additional compounds (PFHxS, PFNA, and HFPO-DA), and a combined "Hazard Index" limit for mixtures of those plus PFBS. Water systems nationwide were given until 2027 to complete initial monitoring and until 2029 to come into full compliance — with treatment, blending, or a new water source if needed.
For Weir River specifically, this is the rule that turned an already-known number into a compliance question: the system's 5.7 ppt PFOA reading, first surfaced through UCMR5 testing, sits above this new 4 ppt limit. That doesn't mean the utility is currently in violation — the compliance clock only started running once the rule was finalized, and the deadline (2029, or later if the proposal described in our newest update is finalized) hasn't arrived yet.
Source: Federal Register — PFAS National Primary Drinking Water Regulation.
The PFAS numbers we've published didn't come from a one-off test or a leak — they came from a routine, nationwide EPA program most people have never heard of: the Unregulated Contaminant Monitoring Rule, now in its fifth iteration (UCMR5).
Every few years, EPA picks a rotating list of contaminants that aren't yet subject to enforceable limits and requires large water systems across the country to test for them. The point isn't enforcement — it's data collection. This is literally how EPA decides what to regulate next: UCMR3 data on PFOA and PFOS in the mid-2010s was part of what built the case for the federal rule that eventually followed in 2024.
Weir River's UCMR5 testing ran in the 2023–2025 window and returned detectable levels of five PFAS compounds, most notably PFOA at 5.7 ppt. At the time of testing, there was no enforceable federal limit for any of them — that arrived afterward, in April 2024. The full table of what was detected, and how it compares to the limits that exist today, is on our Water data page.
Source: EPA Fifth Unregulated Contaminant Monitoring Rule (UCMR5) occurrence data.
Long before there was a federal PFAS rule, there was a Massachusetts one. In October 2020, MassDEP finalized an enforceable drinking water standard — a Maximum Contaminant Level, or MCL — of 20 parts per trillion for the combined total of six PFAS compounds, a grouping the state calls "PFAS6": PFOS, PFOA, PFHxS, PFNA, PFHpA, and PFDA.
At the time, this made Massachusetts one of a small number of states with any enforceable PFAS standard at all. The federal government wouldn't set its own limits for another three and a half years. That gap is part of why state-level standards like this one matter: they can move faster than federal rulemaking, and they're what actually governed Weir River's PFAS obligations for most of the 2020s.
This 20 ppt combined standard remains the operative Massachusetts rule today, and it's separate from (and less strict, compound-for-compound, than) the individual federal PFOA/PFOS limit of 4 ppt that followed in 2024. Both apply simultaneously — a system has to meet whichever is more protective for a given compound.
Source: Mass.gov — Massachusetts PFAS Drinking Water Standard (MCL).
We're kicking off this initiative by publishing what EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR5) found in the Weir River Water System's 2023–2025 testing round: five PFAS compounds, including PFOA at a level above the EPA's individual health-based limit. None of this represents a legal violation — the utility has recorded no health-based MCL violations since 2010 — but it's the kind of detail that doesn't always make it into the annual Consumer Confidence Report summary. See the full breakdown on the Water data page.
System-wide data only tells part of the story — service lines, home plumbing, and private wells can all change what actually comes out of your tap.
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