On October 30, 2026, the U.S. Environmental Protection Agency’s (EPA) approval of Illinois’ enforcement of the federal drinking water rule for Per- and Polyfluoroalkyl Substances (PFAS) became final and effective. The EPA received no requests for a public hearing during the Federal Register notice period following its September 30, 2026, tentative approval. As a result, Illinois now has final authority to administer and enforce the 2024 PFAS National Primary Drinking Water Rule as part of its Public Water System Supervision program. This changes who enforces the PFAS limits in Illinois, not what those limits require. Illinois’ April 2027 monitoring and April 2029 compliance deadlines remain in place.
The EPA’s core finding is that Illinois’ PFAS rules are “no less stringent” than the federal rule. The timing makes the approval notable: The EPA is now proposing to narrow that same federal rule, and it had previously encouraged states to delay their PFAS applications while it did so. Illinois moved ahead anyway.
The Primacy Framework
Under the Safe Drinking Water Act, states can take over day-to-day enforcement of federal drinking water standards, a status known as “primacy.” To keep it, a state must adopt each new federal rule and submit a program revision for EPA approval.
The revision at issue concerns the EPA’s April 2024 PFAS rule. It sets Maximum Contaminant Levels (MCLs) of 4 parts per trillion (ppt) each for PFOA and PFOS and 10 ppt each for PFHxS, PFNA, and HFPO-DA (GenX), plus a Hazard Index for mixtures of PFHxS, PFNA, GenX, and PFBS. Systems must report initial monitoring by April 25, 2027 and meet the MCLs by April 26, 2029.
On January 22, 2026, the Illinois Pollution Control Board (Board) adopted the federal numbers and deadlines, passed by the Illinois General Assembly as Public Act 103-1077. The EPA subsequently published notice of its tentative approval of Illinois’ program revision at 91 Fed. Reg. 61,847 (Sept. 30, 2026). The notice provided an opportunity to request a public hearing through October 30, 2026. No hearing was requested, and the EPA confirmed that its determination became final and effective on October 30, 2026. Accordingly, Illinois’ authority to administer and enforce these federal PFAS drinking water requirements is no longer tentative.
How the Approval Fits the Federal Rollback
On May 18, 2026, the EPA proposed to rescind the limits for PFHxS, PFNA, GenX, and the Hazard Index and to allow eligible water systems to request an exemption pushing PFOA and PFOS compliance from 2029 to 2031. The 2024 rule remains fully in effect but is pending review before the D.C. Circuit in American Water Works Association v. EPA, No. 24-1188. The more pressing question is what a federal rollback would mean in Illinois. The state’s limits are binding state law and would not disappear simply because the EPA rescinded or modified its own requirements. However, the Board adopted them as “identical-in-substance” rules under a statute directing it to track federal regulations and their amendments. It is not yet clear whether that tracking runs in both directions.
The timing also creates a practical gap. The proposed federal extension would be available only in states that have not obtained primacy for the PFOA and PFOS limits; states with primacy would decide for themselves. Because Illinois’ primacy determination became final and effective on October 30, 2026, its applicable water systems may remain on the April 2029 date unless Illinois grants exemptions or the Board amends its rules.
Scope of the Approval
The final approval also has distinct limits. It does not answer the inquiry regarding who causes PFAS contamination or who must pay to address it. Those questions turn on other law, including the D.C. Circuit’s August 18, 2026, decision in Chamber of Commerce v. EPA upholding the designation of PFOA and PFOS as CERCLA hazardous substances. Meeting an MCL does not resolve a tort claim, and an exceedance notice does not establish causation.
Other States
Illinois is not the only state to adopt the federal limits. Wisconsin, Vermont, Maine, and Delaware have each brought federal standards into state law, and a New York bill to adopt them awaits the governor’s signature. The method matters: Limits adopted by reference may change when the federal rule changes, while a standalone state rule generally stays in place until the state itself amends it.
Implications for Utilities and Businesses
The Illinois EPA’s published schedule requires initial monitoring to be completed by April 25, 2027. Any result at or above the trigger level, set at half the MCL, moves a water system to quarterly sampling. Federal changes alone do not move these dates, so systems should not wait for the rescission rulemaking or the D.C. Circuit before sampling. Treatment systems can take years to design, finance, and build, so systems with elevated results should begin capital planning for 2029 now. The four contested limits raise a “sunk cost” question: Before deferring that work, water utilities should consider whether treatment for PFOA and PFOS would capture the other regulated compounds.
Schools, factories, campuses, hotels, hospitals, and mobile home parks on their own wells can be regulated as public water systems and are directly impacted by the rule. For other businesses, the larger exposure sits next to the drinking water rule rather than within it. PFOA and PFOS belong in every Phase I environmental site assessment, and buyers should address PFAS in representations, indemnities, and pre-closing sampling decisions.
For Illinois, uncertainty over EPA approval ended when its approval of the state’s program revision became final and effective on October 30, 2026. While that determination settles which agency administers and enforces these federal PFAS drinking water requirements in Illinois, it does not change the existing limits or deadlines. For businesses, the practical takeaway is that Illinois’ current PFAS requirements and compliance dates remain the rules to plan around today. Companies should continue preparing to meet those requirements while monitoring federal and state developments that could later change which PFAS limits apply or when compliance is required.
For questions or guidance on how this update may impact your organization, please reach out to your Gordon Rees Scully Mansukhani attorney or a member of the Environmental & Toxic Tort team.