As U.S. President Donald Trump takes aim at what he considers an excess of federal regulations, a new lawsuit accuses the Environmental Protection Agency of illegally rescinding a rule to reduce the discharge of mercury from dental offices, mere hours after Trump took office.

In a complaint filed on Wednesday, the nonprofit Natural Resources Defense Council said the final rule was withdrawn on Jan. 20, the date of Trump's inauguration, after White House Chief of Staff Reince Priebus directed federal agencies to “immediately withdraw” final rules slated for publication.

But the NRDC said the mercury rule could not be withdrawn before its expected Jan. 24 publication in the Federal Register because it was subject to a Clean Water Act provision that, given the wording of Priebus' memorandum, forbade withdrawal.

As a result, the EPA had no authority to rescind the rule without first getting public comment, according to the NRDC, an environmental advocacy group. Its lawsuit filed in Manhattan federal court seeks to undo the rule's rescission.

“The Trump administration, and President Trump himself, have made it seem like it will be easy to wipe away environmental protections for the American people,” David Goldston, director of government affairs for the NRDC, said in an interview. “We view this rule as one that is final, and which can be rescinded only through the full rulemaking process.”

An EPA spokeswoman had no immediate comment.

Mercury discharged into the environment can damage people's health, including through seafood consumption.

Dentists nonetheless can use mercury safely in amalgams for fillings.

The EPA rule would have reduced discharges by dental offices of mercury and other metals into municipal sewage treatment plants by more than 10 tons annually.

It would also have required dentists to adopt “best management” practices recommended by the American Dental Association. (here)

On Monday, Trump issued an executive order requiring many federal agencies to eliminate two regulations for each new regulation introduced. Trump is not a defendant in the NRDC lawsuit.

The case is Natural Resources Defense Council v EPA et al, U.S. District Court, Southern District of New York, No. 17-00751.

(Reporting by Jonathan Stempel in New York; Editing by Andrew Hay)