Chemours did not respond to requests for comment.

Almost 40 years after DuPont began quietly dumping that chemical into the river, the mess it has made is proving extremely difficult to clean up. “What mystifies me is the barrier for chemicals’ entry seems to be very low,” said Knappe, who has spent much of the past two years consumed with finding and cleaning up the PFAS compounds in drinking water. “But when it comes to thinking about developing regulation, the barrier is really high.”

The EPA says it is working to solve the problem. After holding a series of local meetings about PFAS contamination this summer, the agency announced that it will be releasing a plan to manage the chemicals later this year. The EPA website points to the work it’s already done studying the health impacts of the chemicals, monitoring their presence in drinking water, and coordinating with states and tribes dealing with contamination. But it’s hard to see how it can fix the country’s massive PFAS problem without addressing how these chemicals come onto the market in the first place.