Top environmentally conscious House Republicans criticized the Trump administration on Tuesday for planning to weaken an Obama-era mercury and toxic air pollution rule to help coal plants.

“There is no reason to relax that standard,” Rep. Francis Rooney, R-Fla., told the Washington Examiner in an interview. “I am against it. I am against coal. Why don’t we just stop burning coal? We’ve got all the natural gas we will ever need.”

In a separate interview, Rep. Carlos Curbelo, R-Fla., said the move lacked rationale.

“The only explanation I can come up with is this was pure zealotry, and more and more Republican members of Congress are standing up against these kind of actions,” Curbelo told the Washington Examiner. “More of them need to join us, because this is bad for our country and I’m sure deeply troubling to a majority of Americans.”

The Environmental Protection Agency said Monday that it sent to the White House a proposal to relax the 2011 Mercury and Air Toxics Standards, or MATS.

While the mercury rule is less publicized than other Obama administration initiatives, the coal industry considers it the most expensive air emissions regulation ever implemented and is already spending $18 billion to comply with it, the EPA said.

States have been setting air pollution targets based on those investments and the rules remaining law. However, the coal industry blames it for forcing the closure of dozens of coal plants across the country.

EPA is not looking to cancel the regulation entirely. Mercury is a neurotoxin that can especially harm the nervous systems of children and fetuses.

But the agency intends to provide legal justification for weakening it, and perhaps other air pollution rules, by proposing to change the way that it calculates the costs and benefits of regulations.

Rooney said Tuesday that the move is indicative of the Trump administration’s broader agenda to help coal and other fossil fuels by rolling back regulations intended to reduce pollution. He cited the administration’s moves last month to weaken Obama-era regulations targeting methane, a potent greenhouse gas that is the main component of natural gas, and its plan to expand offshore oil and gas drilling.

“I am disappointed with the Trump administration,” Rooney said. “And I am also against relaxing the methane and onshore well inspection requirements that Obama put in. I am not for relaxing those. And I am certainly not for relaxing offshore drilling regulations.”

Rooney is speaking out as he increases his visibility on addressing climate change.

On Monday, he became the latest Republican to join the Climate Solutions Caucus, a bipartisan group vowing to combat climate change that consists of 88 equal number GOP members and Democrats — and chaired by Curbelo.

Rooney co-sponsored a carbon tax bill introduced this summer by Curbelo, who is facing a tough re-election fight in a swing district won by Hillary Clinton in 2016.

Both of their districts are vulnerable to sea level rise caused by climate change.