President Bush, in a rare visit to the Environmental Protection Agency, pledged Monday that science would be at the heart of the nation's air, water and land policies.

Bush attended a ceremonial swearing-in ceremony for Stephen Johnson (search), the first career employee to take over the agency's reins. Johnson, a 24-year EPA veteran, also is the first administrator with a science background.

"With this background, Steve will help us continue to place sound scientific analysis at the heart of all major environmental decisions," Bush said at a 15-minute ceremony in which White House chief of staff Andy Card administered the oath of office.

Johnson had already been sworn in and taken over as EPA administrator on May 2.

Environmentalists and some federal scientists have complained that the Bush administration often puts politics ahead of science on issues such as global warming (search), toxic chemicals, forest and energy policies and protections for imperiled species.

With the visit, Bush became the first president to visit EPA headquarters. Bush, often at odds with environmentalists, used the occasion to plug his agenda while calling Johnson "the right man" for the job.

"As Steve leads the EPA, he will maintain our common-sense approach of collaborating with leaders and volunteers at the local level to find the best solutions to meet our national goals," Bush said.

"We'll continue to vigorously enforce our environmental laws," the president continued. "We'll encourage good stewardship of natural resources, and we will focus on results."

Bush said one of Johnson's first big tasks was to persuade Congress to pass the "Clear Skies" (search) air pollution plan. In March, a Senate committee rejected the bill. Opponents want limits on carbon dioxide, the chief "greenhouse" gas scientists blame for global warming, but which Bush says is too costly to regulate.

Johnson said he felt "great enthusiasm and profound optimism" for his agency's work, but admitted being at a loss for words to express what his new job felt like.

"As I prepared for today, I thought about how I felt when the president asked me to lead EPA," he recounted. "Even after years of Latin, German, scientific training, the only word I could think of was 'wow.' Wow."