The EPA’s plan to designate for the first time two “forever chemicals” as hazardous substances under the powerful Superfund law has sparked fears of runaway costs associated with cleaning up contaminated sites, attorneys say.

An Environmental Protection Agency proposal to designate PFOA and PFOS would be the first time the agency has wielded the Comprehensive Environmental Response, Compensation, and Liability Act, known as CERCLA or the Superfund law, to designate chemicals as hazardous in the 40-plus years since its passage.

The move would allow the EPA to apply the Superfund law’s bedrock “polluter pays” principle to cleanups, which means the EPA or state agencies could recover full costs or contributions from polluters.

The plan, stuck in a White House review since January, raises concerns a hazardous designation would trigger reopening some remediated sites if significant enough levels of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) remain. The regulations, if finalized, are expected to impose detailed reporting requirements and could disrupt ongoing litigation focused on settling responsibilities for cleanups, say attorneys tracking the issue.