DuPont introduced GenX in 2009 to replace PFOA , also known as C8, a chemical it had used for decades in North Carolina, West Virginia, and other locations to make Teflon and other products. Like GenX, PFOA escaped the West Virginia plant and seeped into local drinking water. The contamination — and the fact that DuPont executives knew about it and hid their knowledge — set off a mammoth class-action suit , which DuPont settled for $671 million.

“EPA is concerned that drinking water wells in the vicinity of the Washington Works facility may similarly be contaminated by GenX,” the letter explained.

McManus also referred to GenX contamination near the Chemours factory in Fayetteville, North Carolina, where DuPont and its spinoff Chemours dumped approximately 200,000 pounds of GenX into the Cape Fear River since 1980, according to Detlef Knappe, a North Carolina State University professor who has studied the contamination. In that time, more than 200,000 people have been exposed to GenX in their drinking water.

The Environmental Protection Agency has asked Chemours to test water near its plant in West Virginia for the presence of the chemical GenX. In a January 11 letter to Andrew Hartten, Chemours’ principal project manager for corporate remediation, Kate McManus, acting director of the EPA’s water protection division, noted that GenX has already “been detected in three on-site production wells and one on-site drinking water well” at the company’s factory in West Virginia, which is known as Washington Works.

PFOA, which has been associated with cancers, autoimmune diseases, hormonal dysfunction, and other health problems, was phased out of use in the U.S. in 2015. Though DuPont presented GenX as a safer alternative to PFOA, the chemical has been associated with some of the same health problems, as The Intercept reported in 2016.

Attorney Robert Bilott has been asking the West Virginia Department of Environmental Protection to provide information on the use and release of GenX at the Parkersburg plant for more than a year. In a November 28 letter to the agency, Bilott noted that “at least some of the GenX materials at issue in North Carolina may be shipped to or used at the Washington Works plant in West Virginia, where there could also be air and water emissions.”

As the lead attorney in the epic legal battle over DuPont’s release of PFOA into the Ohio River, Bilott first asked the state agency to provide details on its agreement to allow DuPont to discharge GenX into the Ohio River in July of last year. But the agency didn’t respond to many of his letters — just as it had evaded many of his questions about PFOA before that.

“As noted in our previous correspondence, we have been writing to the West Virginia Department of Environmental Protection (“WVDEP”) for over sixteen years to try to focus your Agency’s attention on the threats to human health and the environment posed by perfluorochemicals,” Bilott wrote in July.

A month before that, testing done by a university student in Ohio named Jason Galloway measured GenX in surface water as far as 20 miles from the West Virginia Chemours plant. Galloway also found the chemical in various creeks and streams in the area at levels reaching more than 100 parts per trillion.

The EPA chose 14 public and private drinking water supplies in the vicinity of the Washington Works facility to be tested for GenX “based upon their historically high concentrations of PFOA,” according to McManus’s letter. “It is likely that these same wells would be impacted by GenX based upon the common methods of dispersal.”

McManus instructed Chemours to complete the testing by March 31.