How Mark Ruffalo found an outlet for his political passions in 'Dark Waters'

Mark Ruffalo has long been paranoid about his drinking water. His home, tucked in the Catskill Mountains along the Delaware River, is outfitted with an elaborate water filtration system even though his well water is some of the cleanest in the nation.

But he knows the risks, and he can't ignore them. A decade ago, energy companies threatened to begin natural gas drilling near his 47-acre former dairy farm in New York. He subsequently became an outspoken environmental activist, arguing that the process of extracting gas via hydraulic fracturing - or hydrofracking - contaminates water with dangerous chemicals.

But until this weekend - with the nationwide release of his new film "Dark Waters" - Ruffalo has kept his politics and his acting career largely separate. In his off time, he shows up at rallies to speak about his antifracking stance and campaigns for Bernie Sanders, whom he supports in part because of the candidate's belief in the Green New Deal. At work, most of his calendar has been dominated by Marvel. Since 2012, he's played the Hulk in four films in the comic book universe.

"I love those, and I fit in well there and I enjoy that, but I also - I have more to say," said Ruffalo. "So finally I was like, 'Hey, wait a minute. How do I blend this activism that means so much