If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.


Persistent Pollutants

US EPA orders toxicity tests on PFAS used in GenX

HFPO-DAF may present unreasonable health risks, US agency says

by Britt E. Erickson
August 23, 2023 | A version of this story appeared in Volume 101, Issue 28


The US Environmental Protection Agency wants more data on the hazards of a member of the chemical family known as per- and polyfluoroalkyl substances (PFAS). The chemical—2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoyl fluoride (HFPO-DAF)—is used to make hexafluoropropylene oxide dimer acid (HFPO-DA). HFPO-DA is a key part of GenX, technology used by Chemours to replace perfluorooctanoic acid, a toxic PFAS once used as a processing aid by fluoropolymer manufacturers.

Chemical structure of HFPO-DAF.

In an Aug. 15 test order, the EPA directed three chemical companies—Chemours, E. I. du Pont de Nemours, and 3M—to provide information on various physical-chemical properties of HFPO-DAF and whether the substance causes serious eye damage. Depending on the results, the companies may also have to test for effects on skin and DNA. Workers may be exposed to HFPO-DAF, and the chemical may pose unreasonable health risks, including organ damage and cancer, the agency says.

The test order is the EPA’s third to target PFAS under the Toxic Substances Control Act. The first order addressed 6:2 fluorotelomer sulfonamide betaine (6:2 FTAB), found in firefighting foams. The second sought toxicity data on another PFAS used in GenX—hexafluoropropylene oxide (HFPO).

“We still don’t know enough about the dangers that many PFAS might pose to human health,” Michal Freedhoff, assistant administrator for the EPA’s Office of Chemical Safety and Pollution Prevention, says in a statement. “We’re using all the tools at our disposal to rapidly gather data about these substances so that we can better understand the potential environmental and human health impacts of PFAS and take any necessary steps to address them.”



This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.