Some environmental groups argue that the EPA can’t legally weaken the regulations. The Safe Water Drinking Act gives the EPA authority to limit water contaminants, and it includes a provision meant to prevent new rules from being looser than previous ones.

The administration said it wants to rescind and reconsider whether limits are needed for four PFAS that chemical companies are still producing and using in the U.S. — despite known health risks.

PFAS are linked with cancer, fertility issues, and developmental delays in children — yet the E.P.A. has moved to weaken regulations designed to protect Americans