AceShowbiz - Actor Mark Ruffalo has been placed on a terror advisory list by U.S. officials after organizing screenings for a new documentary about natural gas drilling. The "Zodiac" actor arranged showings for GasLand earlier this year and voiced his concerns about the affects the practice is having on America's water supplies.

But his efforts to raise awareness and demand a stop to natural gas drilling reportedly attracted the attention of officials from Pennsylvania's Office of Homeland Security - and he recently discovered it had landed him on a terror alert watchlist.

But Ruffalo is taking it all in his stride and has laughed off the idea he could be a threat to security in his native U.S. He tells America's GQ magazine, "(It's) pretty f**kin' funny."