The Ohio River delivers billions of gallons past Louisville, Kentucky, every day; the Louisville Water Company draws from that flow to produce the city’s tap water. A team of scientists and technicians there continuously monitors pH, odors, metals, microbes — and, unlike many smaller utilities, routinely tests for PFAS (per- and polyfluoroalkyl substances).
PFAS are a class of long-lasting chemicals used for decades in items such as nonstick cookware, cosmetics, raincoats, food wrappers and firefighting foams. Research has linked certain PFAS to health risks including cancer, weaker immune responses, higher cholesterol and developmental delays in children. Their chemical stability earns them the nickname “forever chemicals,” and they now appear widely in soils, waters and in the blood of most Americans.
Louisville tracks several PFAS, including HFPO-DA, better known by the trade name GenX. In December 2024 the utility detected an unexpected spike in GenX in raw (untreated) water drawn from the Ohio River: 52 parts per trillion, up from about 3.4 parts per trillion the previous month. To illustrate scale, Peter Goodmann, Louisville Water’s director of water quality and research, said a part per trillion is like one second in 32,800 years; one drop in 20 Olympic swimming pools is another way to picture it.
The utility traced the elevated GenX upstream through the Ohio River past Cincinnati and into forested stretches, ultimately linking the increase to public discharge data from a Chemours facility near Parkersburg, West Virginia — about 400 miles upstream. That plant, Washington Works, manufactures fluoropolymers used in semiconductors and has a well-documented PFAS history. Legal battles over PFAS at DuPont, the plant’s previous owner, revealed decades-old concerns about toxicity; Chemours was spun off from DuPont in 2015.
Goodmann said the December spike aligned with public Chemours discharge records, but he did not believe local customers were at immediate risk. PFAS-related risks are assessed over lifetime exposures, and Louisville’s data showed finished drinking water — after standard treatment — fell under the federal limits that regulators adopted in 2024. Chemours has asserted finished downstream water is safe and has denied that its discharges caused the spike; the company did not respond to an NPR request for comment.
Federal PFAS regulation is recent. In 2024 the EPA finalized national drinking water limits for six PFAS. Those rules require utilities exceeding the limits to treat their water beginning in 2029. When the EPA previously took enforcement action in 2023, it said Chemours’ West Virginia plant had repeatedly exceeded permit limits for GenX and PFOA. Environmental groups, led by the West Virginia Rivers Coalition, filed suit. In 2024 the coalition sued over continuing discharges, saying the EPA’s consent order was not being aggressively enforced.
In August a federal judge ordered Chemours to stop exceeding permit limits immediately; the company appealed. In its litigation responses, Chemours acknowledged permit violations but said it was working with regulators on fixes and emphasized downstream finished-water compliance.
Regulatory shifts followed political changes. After a subsequent re-election and appointment of a new EPA administrator, the agency announced it would retain maximum contaminant levels only for PFOA and PFOS, dropping limits for four other PFAS including GenX, and extended compliance deadlines for remaining rules to 2031, citing costs and the burden on smaller systems.
Many utilities will face infrastructure and expense challenges removing PFAS. Louisville is investing about $23 million to redesign its powdered activated carbon treatment system, one method for removing PFAS. A federal study estimated roughly 45% of U.S. tap water contains at least one PFAS. When the 2024 rules were announced, the Biden administration estimated that up to 10% of the nation’s roughly 66,000 public drinking water systems might have PFAS levels high enough to require action.
Advocates stress that preventing PFAS from reaching source waters is more effective and less costly than treating contamination downstream. Nick Hart, water policy director at the Kentucky Waterways Alliance, described regulatory permits as a “license to pollute,” arguing that permit limits represent maximum allowable contamination rather than an absolute guarantee of safety.
Louisville’s experience highlights how upstream industrial discharges can affect downstream utilities. Goodmann has urged that when regulators issue or renew permits for dischargers such as Chemours, they should consider impacts on downstream treatment plants and communities. Source-water protection, he said, is central to managing risk: keeping contaminants out of the river reduces the burden on water treatment.
Environmental groups hailed the court order in the Chemours case as a win for public health and the Ohio River. Autumn Crowe, deputy director of the West Virginia Rivers Coalition, called the ruling recognition of long-standing pollution and a step toward accountability.
As research into PFAS health effects continues, utilities, regulators and communities face decisions about monitoring, treatment investments and upstream pollution controls. Louisville’s routine PFAS testing allowed it to detect the spike, trace its likely source and confirm finished water complied with then-applicable federal standards — a sequence that illustrates both the reach of PFAS contamination and the practical challenges of protecting drinking water.