While the US EPA’s April 2024 PFAS MCL rule establishes a federal floor of 4 ppt for PFOA and PFOS, many states have enacted their own standards — in some cases years ahead of federal action — and several have set limits significantly stricter than the federal MCL. Understanding this regulatory patchwork is essential for water utilities and technology vendors operating across multiple states.
States with the Strictest PFAS Limits
Massachusetts was among the first states to establish enforceable PFAS MCLs, adopting a combined limit of 20 ppt for six PFAS compounds (PFOA, PFOS, PFNA, PFHxS, PFDA, and PFUnDA) in 2020. Vermont followed with a 20 ppt combined limit for five PFAS compounds. Michigan established individual MCLs ranging from 8 ppt (PFNA, PFHxS) to 16 ppt (PFOA, PFOS) — all more stringent than the federal 4 ppt standard for the same compounds — in 2020. These early-acting states have generated the most extensive body of treatment implementation experience in the US.
New Hampshire, Connecticut, and New York have also enacted sub-20 ppt PFAS standards for multiple compounds. Maine has taken a particularly aggressive approach, targeting PFOA and PFOS at 20 ppt while also establishing notification levels and action levels for a broader set of emerging PFAS. New Jersey adopted a 14 ppt MCL for PFOA and a 13 ppt MCL for PFOS in 2020, predating federal action by four years.
Variation in Compound Coverage and Enforcement
Beyond concentration limits, states differ significantly in the range of PFAS compounds regulated, monitoring frequency requirements, and enforcement mechanisms. Some states regulate only PFOA and PFOS; others cover 6, 14, or more compounds. States like California have adopted a PFAS notification level system that triggers public communication requirements below formal MCL levels, effectively creating a multi-tier compliance framework.
For water utilities operating in multiple states, the patchwork of state MCLs creates compliance complexity — particularly where a utility serves customers in adjacent states with different standards. Treatment systems must be designed to meet the most stringent applicable limit, which in practice means targeting the lowest state MCL in the service area.
For technology vendors, state-level regulatory variation creates differentiated market segments. States with early, strict MCLs — Massachusetts, Michigan, New Jersey, New Hampshire — have already executed substantial treatment procurement and can provide reference installations and performance validation data. States still in early regulatory development represent the next wave of procurement demand, typically 2-4 years behind the leading states in implementation timeline.