Taking on late night comedian Stephen Colbert last night, U.S. Environmental Protection Agency Administrator Lisa Jackson made her case that a healthy environment is essential to human health.

Opening the interview on Comedy Central’s “Colbert Report,” Colbert mused, “Okay, I’ll bite. Environment. Why do we need it?”

Jackson responded that the environment is the air that we breathe, the water that we drink. “If those things aren’t clean, we can’t have a healthy and safe community.”

“EPA’s been around 41 years,” said Jackson. “We don’t always remember some of the things that we dealt with.” She reminded her host about lead in gasoline, the chemical alar that was sprayed on apples, rivers that were on fire and smoggy air.

To that, Colbert joked that the midday haze was natural sunblock.

Acknowledging the progress, he said, “We’ve cleaned things up. Things are way cleaner than they used to be.” He asked, “Why do we need the EPA anymore?”

“One of the things we worry a lot about is backsliding. And we’re not done,” replied Jackson. “It was not until this past year that we finally set a national standard in this country to deal with mercury,” she said, listing the many health hazards of the neurotoxin.

Colbert asked about the administration’s delay of stricter smog standards and whether Jackson would be voting for Republican candidate Mitt Romney in the fall as a result. Jackson explained that the president wanted all of the latest science taken into account before issuing new rules, which she expects next year.

“Okay, when Romney is president,” he asked, to which she replied with a furrowed brow.