The U.S. Environmental Protection Agency will replace Obama-era carbon and clean water regulations and open up a national debate on climate change in 2018, part of a list of priorities for the year that also includes fighting lead contamination in public drinking water.

The agenda, laid out by EPA Administrator Scott Pruitt in an exclusive interview with Reuters on Tuesday, marks an extension of the agency’s efforts under President Donald Trump to weaken or kill regulations the administration believes are too broad and harm economic growth, but which environmentalists say are critical to human health.

READ MORE: Trump administration to reverse centerpiece of Obama’s climate change policy

“The climate is changing. That’s not the debate. The debate is how do we know what the ideal surface temperature is in 2100?… I think the American people deserve an open honest transparent discussion about those things,” said Pruitt, who has frequently cast doubt on the causes and implications of global warming.

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Pruitt reaffirmed plans for the EPA to host a public debate on climate science sometime this year that would pit climate change doubters against other climate scientists, but he provided no further details on timing or which scientists would be involved.

Pruitt said among the EPA’s top priorities for 2018 will be to replace the Clean Power Plan, former President Barack Obama’s centerpiece climate change regulation which would have slashed carbon emissions from power plants. The EPA began the process of rescinding the regulation last year and is taking input on what should replace it.

“A proposed rule will come out this year and then a final rule will come out sometime this year,” he said. He did not give any details on what the rule could look like, saying the agency was still soliciting comments from stakeholders.

READ MORE: Donald Trump to revoke Obama-era climate change rules on infrastructure projects

He said the agency was also planning to rewrite the Waters of the United States rule, another Obama-era regulation, this one defining which U.S. waterways are protected under federal law. Pruitt and Trump have said the rule marked an overreach by including streams that are shallow, narrow, or sometimes completely dry – and was choking off energy development.

Pruitt said that in both cases, former President Barack Obama had made the rules by executive order, and without Congress. “We only have the authority that Congress gives us,” Pruitt said.

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Pruitt’s plans to replace the Clean Power Plan have raised concerns by attorneys general of states like California and New York, who said in comments submitted to the EPA on Tuesday that the administrator should recuse himself because as Oklahoma attorney general he led legal challenges against it.

BIOFUELS AND STAFF CUTS

Pruitt said he hoped for legislative reform of the U.S. biofuels policy this year, calling it “substantially needed and important” because of the costs the regulation imposes on oil refiners.

The Renewable Fuel Standard, ushered in by former President George W. Bush as a way to help U.S. farmers, requires refiners to blend increasing amounts of biofuels like corn-based ethanol into the nation’s fuel supply every year.

Refining companies say the EPA-administered policy costs them hundreds of millions of dollars annually and threatens to put some plants out of business. But their proposals to change the program have so far been rejected by the Trump administration under pressure from the corn lobby.

The EPA in November slightly raised biofuels volumes mandates for 2018, after previously opening the door to cuts.

The White House is now mediating talks on the issue between representatives of both sides, with input from EPA, and some Republican senators from states representing refineries are working on possible legislation to overhaul the program.

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Pruitt said he also hoped Congress could produce an infrastructure package this year that would include replacing municipal water pipes, as a way of combating high lead levels in certain parts of the United States.

READ MORE: Donald Trump signs executive order rolling back Obama’s climate change plan

“That to me is something very tangible very important that we can achieve for the American people,” he said.

Pruitt added that EPA also continuing its review of automobile fuel efficiency rules, and would be headed to California soon for more meetings with the California Air Resources Board to discuss them.

California in 2011 agreed to adopt the federal vehicle emission rules through 2025, but has signaled it would opt out of the standards if they are weakened – a move that would complicate matters for automakers serving the huge California market.

In the meantime, Pruitt said EPA is continuing to reduce the size of its staff, which fell to 14,162 employees as of Jan. 3, the lowest it has been since 1998, under Ronald Reagan when the employment level was 14,400. The EPA employed about 15,000 when Obama left office.

Nearly 50 percent of the EPA will be eligible to retire within the next five years, according to the agency.

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