State Drill Down – PFAS in Drinking Water

In Q1 of 2025, several states proposed PFAS limits in drinking water to preempt any attempts by the current administration to roll back the current Maximum Contaminant Levels (MCLs) finalized by the U.S. EPA in 2024. In this post, I’ll summarize what we’re seeing and provide insights into what this may mean for our drinking water clients.

Background – Are the MCLs in Danger?

In 2024, under the auspices of the Safe Drinking Water Act (SDWA), the U.S. EPA finalized National Primary Drinking Water Regulations (NPDWR) limiting the concentration of certain PFAS in drinking water. These compounds include PFOS, PFOA, HFPO-DA (GenX), PFHxS, PFNA, and PFBS. Some media outlets and organizations have implied that the Regulatory Freeze Pending Review (Regulatory Freeze) impacts these limits. Since this action was finalized, published in the Federal Register and put into effect (required sampling and reporting has already started), the Regulatory Freeze may have limited impact.

However, that’s not to say that the current EPA administration might not revisit the MCLs and change them. Presumably, this would require the agency to follow the established rulemaking process, so even if the change does happen, it probably won’t happen quickly. Public Water Systems (PWSs) required to sample under the NPDWR can continue to do so. In fact, those systems participating in UCMR 5 are compelled to, and those systems will use that data to comply with the PFAS NPDWR Initial Monitoring requirements.

Another threat to the established limits comes from the courts. At least three groups filed lawsuits ahead of the June 2024 deadline. As you might expect, chemical companies are in that mix, citing concerns over the science used to establish the MCLs and the EPA’s authority. The American Water Works Association (AWWA) and Association of Metropolitan Water Agencies (AMWA) also brought a lawsuit, also questioning the science used to set limits and further claiming that the EPA underestimated the compliance costs to water systems. As we reported in our March News and Views, this suit was put on hold for 60 days and will resume in early April.

At this point, it’s difficult to predict the outcome of these cases and the future of the PFAS MCLs for drinking water. We are closely watching events unfold and will share what we learn here at www.PFAS.com.

What the UCMR Data Tells Us About PFAS in the Nation’s Public Water Systems

Data is always helpful when making sense of a situation, and in this case, the Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) can help. Under UCMR 5, all PWSs serving more than 3300 people and a randomly selected set of 800 smaller systems were required to begin sampling for 29 PFAS (plus lithium) in January of 2023. This is a substantial subset of the PWSs required to sample under the SDWA, so the data provides insights into how prevalent the problem is.

The EPA estimated that about 10% of PWSs would be required to take action to remediate elevated levels of PFAS in their drinking water. So far, this estimate comes close to what the UCMR data reveals. In January 2025, the 7^th set of UCMR 5 data was released. As with previous data sets, PFOA and PFOS are the compounds of greatest concern, with 9% of all PWSs tested to date detecting PFOS (the most prevalent PFAS detected) at levels exceeding the NPDWR limits.

Source: The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary: January 2025

Under the NPDWR, Public Water Systems have until 2029 to address elevated levels of PFAS. However, as discussed in a recent Pace® webinar, your options aren’t limited to what the EPA calls Best Available Treatment, or BET, solutions. What works for one water system might not work for another. Pilot testing can help you choose the most efficient and cost-effective solution for your system.

Watch: Navigating PFAS in Drinking Water: Treatability Insights and Analytical Overview

PFAS MCLs Proposed by State Legislators in 2025

There are a few ways PFAS MCLs can be set at the state level. One primary path is for the state legislature to pass a law, either setting an MCL directly or requiring the applicable state agency that administers the SDWA on behalf of U.S. EPA to do so. Many states took the latter route when the U.S. EPA published their initial Health Advisory for PFOA and PFOS of 70 parts per trillion (ppt), individually or combined, back in 2016.

According to the Safer States Bill Tracker, 19 states have 59 proposed bills pertaining to PFAS in drinking water as of the end of March 2025. Minnesota leads the pack, with 19 bills being proposed so far. However, many of these bills deal with funding of existing laws and programs. In fact, a good portion of the 59 proposed laws address appropriations in some way, including setting aside funding for certain communities to address their water quality challenges. Five bills address PFAS in private wells, but that’s a discussion for another day.

Of the 59 proposals, eight state legislatures have proposed bills pertaining to MCLs in drinking water. The chart below originated from Safer States, but we added a little more color to the description where appropriate. If some of these laws seem to lack clarity or specificity, it may be because they aren’t very far along in the process. Details are often added in committees and through proposed amendments.

What Happens Next?

Remember, states can set their own MCLs for PFAS in drinking water, provided they are at least as stringent as those set by the U.S. EPA. Most proposals that directly specify limits set them at levels comparable to the current federal MCLs. Vermont is an outlier, proposing an MCL of zero ppt for PFOA, PFOS, PFHxS, PFNA, PFHpA, and PFDA and an MCL for any other testable PFAS. Not only is the limit lower, the subset of PFAS assigned the zero ppt limit differs from the federal NPDWR. In addition, the proposal covers ALL testable PFAS. Since the bill pertains to drinking water, most likely that would include the 29 PFAS currently detectable using the EPA-validated drinking water test methods, EPA 533 and EPA 537.1.

If the federal PFAS limits do get modified, it will be interesting to see what further actions are taken at the state level. If these bills make their way through their respective state legislatures and get signed into law, any changes made by U.S. EPA won’t matter in these states – or any others that already set enforceable levels.