While the 2010 elections and holiday season may have slowed them down, celebrities are once again streaming into town in support of various causes.

Actor Mark Ruffalo and director Josh Fox were on Capitol Hill on Thursday morning to raise awareness about hydraulic fracturing, a form of natural gas extraction that sometimes contaminates drinking water.

Ruffalo joined Democratic Reps. Maurice Hinchey (N.Y.), Jared Polis (Colo.) and Rush Holt (N.J.), who plan to introduce a bill to close loopholes in the Safe Drinking Water Act, at a press conference on the Capitol’s East Front. Ruffalo resides in the Catskills, an area affected by natural gas extraction, and he’s one of Hinchey’s constituents.

“I’m not here as an actor today,” Ruffalo said. “I’m actually here as a father and a citizen. As a father, I don’t want my kids to be poisoned. I’m here to bare witness and to say that drilling isn’t safe.”

Ruffalo wasn’t the only actor in town Thursday.

Pippa Black, star of NBC’s “Outsourced,” was also in town, though for a more cuddly cause. The Australian actress and longtime animal lover is scheduled to attend the Thursday night opening of the American Humane Association’s D.C. office.

“It’s going to be really critical for them to be closer to the politics,” Black told HOH.