Earlier this week, I wrote regarding the ongoing legal challenges to the EPA’s PFAS drinking water limits proposed under the Safe Drinking Water Act. In that update, one prediction was that the uncertainty surrounding the federal drinking water regulations (in terms of both which PFAS would ultimately be regulated and what the Maximum Contaminant Levels would be) would result in states acting to impose regulations that mirror the federal regulations. The Wisconsin PFAS proposal of yesterday makes it the first state to follow precisely this path since the oral argument in the D.C. Circuit Court related to the drinking water challenges.

Wisconsin’s Natural Resources Board approved a proposed rule by Wisconsin’s Department of Natural Resources that mirrors the federal PFAS drinking water regulations put forth by the EPA in April 2024. As a reminder, that rule set Maximum Contaminant Levels for PFOA and PFOS of 4ppt, a 10 ppt limit for PFNA, PFHxs, and GenX, and a Hazard Index approach to these latter three chemicals plus PFBS. The Wisconsin PFAS drinking water rule was proposed as a direct reaction to the EPA’s stated desire to eliminate all PFAS but for PFOA and PFOS from the federal regulations.

The rule still needs to be approved by the Governor and the Republican-controlled Wisconsin Legislature, but the action is nevertheless a critical first step towards the state implementing tough PFAS drinking water limits in the state. Corporations concerned about legacy uses (whether intentional or not) of PFAS and water discharges that may have contaminated drinking water sources would be well advised to continue due diligence appropriate for their specific needs to ensure that a complete potential risk picture is understood.