FILE - In this Thursday, Nov. 10, 2016 file photo, a doctor holds an e-cigarette in a smoking lab at the Centers for Disease Control and Prevention in Atlanta. An exhaustive government report issued Tuesday, Jan. 23, 2018 wrestles with the potential benefits and harms of the vapor-emitting devices, which remain unclear more than a decade after their introduction in the U.S. (AP Photo/Branden Camp)