PFAS in Wisconsin Drinking Water

PFAS is shorthand for per- and polyfluoroalkyl substances, a family of thousands of synthetic chemicals used since the 1940s in firefighting foam, non-stick coatings, water-repellent fabrics, and industrial processes. They're called 'forever chemicals' because the carbon-fluorine bond doesn't break down in the environment — they accumulate in groundwater, in fish, and in human blood. In Wisconsin, the largest known contamination plumes are at military bases (Mitchell ANG in Milwaukee, Truax in Madison, Camp Williams in Juneau County) and at industrial sites where firefighting foam was used.

In April 2024 the EPA finalized federal MCLs for six PFAS compounds: PFOA and PFOS at 4 parts per trillion each, PFHxS, PFNA, and HFPO-DA (GenX) at 10 ppt each, and PFBS regulated through a Hazard Index calculation that accounts for the combined toxicity of mixtures. Wisconsin water systems have until 2029 to comply. Several systems are already over the new limits and are working through treatment installations — UCMR5 monitoring data shows the scope of the problem statewide.