Wheeler's nomination has been welcomed by businesses eager to see reduced regulation, but upset Democrats and conservation groups anxious that environmental rollbacks under the Trump administration are going too far.
With two years under their belt now, however, Hartl says the agency has likely learned from the legal setbacks and will be more deliberative in its attempts to rollback regulations.
Hayden accused Senate Majority Leader Mitch McConnell (R-Ky.) and Republicans of putting "the wealth of a few over the health of the many by confirming the coal industry's favored Wheeler-dealer to what used to be the leading environmental enforcement post in the federal government".
While Wheeler doesn't outright deny climate change, he has also downplayed its urgency during his time in the Trump administration.
During his confirmation hearing in January, Wheeler said he did not believe climate change was a major crisis - a stance that resonates with Trump's skepticism but which clashes with the scientific consensus that global warming will have devastating consequences if not addressed urgently.
Susan Collins, a moderate Republican senator from ME, has said she would oppose Wheeler's nomination, arguing his efforts to roll back standards on emissions blamed for climate change took the country in the wrong direction.
Senators voted 52-47 on Thursday to confirm Wheeler, who was nominated by President Donald Trump after former administrator Scott Pruitt resigned under pressure previous year. He capped off the month by announcing plans to relax a rule restricting how much mercury and other unsafe pollutants coal-fired plants can release into the air. But opposed Wheeler's confirmation this time, he said, in light of his push to freeze vehicle fuel efficiency standards and to revisit the cost-benefit analysis the agency used to impose limits on mercury pollution that power companies have already achieved. A month later, federal scientists from 13 agencies, including the EPA, confirmed the findings in a National Climate Assessment that forecast US average temperatures surging "9 degrees F (5 degrees C) or more by the end of this century".
Senator John Barrasso, a Republican from Wyoming, chair of the Senate Committee on Environment and Public Works, said Wednesday that Trump picked the right man for the job.
Wheeler's EPA has continued efforts as well to scale back Obama-era constraints on coal-fired power plants, and with Wheeler at the helm the agency proposed a rollback of rules that regulate leaks of methane from oil and gas facilities.
But Sen. Tom Udall, D-N.M., said Wheeler was failing to protect the environment and human health and was "nominated to unravel and undo the environmental protections that are now in place".
"Unlike with some nominees, we do not have to speculate about what Mr. Wheeler will do in office", she said. "From his actions as acting administrator for the past eight months, we have clear evidence of his agenda: undermine rules to limit toxic mercury, allow more smog and water pollution, and roll back protections against the threat of climate change".
All five senators had met with Wheeler earlier in February over the issue and voted to approve Wheeler on Thursday.