WASHINGTON (Reuters) - U.S. regulators on Wednesday postponed until 2020 new limits on toxic metals and other pollutants in the wastewater of coal-fired power plants, a delay welcomed by industry groups that had sought it but decried by environmental groups.

The Environmental Protection Agency’s move “resets the clock” for the effluent guidelines for power plants, providing relief to the plants from existing regulatory deadlines while the agency studies the regulation, EPA Administrator Scott Pruitt said in a statement. The plants now will have until Nov. 1 2020 to comply with the rule, instead of Nov. 1, 2018.

The rule, which the Obama administration finalized in 2015, set new limits on metals linked to human health problems including lead, mercury and arsenic in the wastewater of the coal-fired plants. High levels of mercury in the bloodstream, for instance, can cause learning problems in children.

The EPA estimates that annual compliance costs to coal plants, once the rule goes into effect, will be $480 million. Benefits associated with the pollution reductions will be worth $451 million to $566 million a year, it estimates.

The move is one of a series of actions by the administration of President Donald Trump to roll back more stringent Obama-era environmental standards, particularly affecting the coal and oil industries.

The U.S. Small Business Administration and the Utility Water Act Group had both petitioned the EPA to delay the rule.

Environmentalists decried the delay. Thomas Cmar, a lawyer at Earthjustice, called it “a bold-faced gift to the coal industry at the expense of the health of families everywhere.”