Scott Pruitt, whom the Senate confirmed Friday, 52-46, doesn’t fit either mold. His focus is neither expanding nor reducing regulation. “There is no reason why EPA’s role should ebb or flow based on a particular administration, or a particular administrator,” he says. “Agencies exist to administer the law. Congress passes statutes, and those statutes are very clear on the job EPA has to do. We’re going to do that job.” You might call him an EPA originalist.

Not that environmentalists and Democrats saw it that way. His was one of President Trump’s most contentious cabinet nominations. Opponents objected that as Oklahoma’s attorney general Mr. Pruitt had sued the EPA at least 14 times. Detractors labeled him a “climate denier” and an oil-and-gas shill, intent on gutting the agency and destroying the planet. For his confirmation hearing, Mr. Pruitt sat through six theatrical hours of questions and submitted more than 1,000 written responses.

When Mr. Pruitt sat down Thursday for his first interview since his November nomination, he spent most of the time waxing enthusiastic about all the good his agency can accomplish once he refocuses it on its statutorily defined mission: working cooperatively with the states to improve water and air quality.

“We’ve made extraordinary progress on the environment over the decades, and that’s something we should celebrate,” he says. “But there is real work to be done.” What kind of work? Hitting air-quality targets, for one: “Under current measurements, some 40% of the country is still in nonattainment.” There’s also toxic waste to clean up: “We’ve got 1,300 Superfund sites and some of them have been on the list for more than three decades.”

Such work is where Washington can make a real difference. “These are issues that go directly to the health of our citizens that should be the absolute focus of this agency,” Mr. Pruitt says. “This president is a fixer, he’s an action-oriented leader, and a