In this Feb. 4, 2014, photo, U.S. Surgeon General appointee Vivek Murthy appears on Capitol Hill in Washington. The U.S. surgeon general is calling e-cigarettes an emerging public health threat to the nation's youth. In a report being released Thursday, Murthy acknowledges a need for more research into the health effects of "vaping," but says e-cigarettes aren't harmless and too many teens are using them. (AP Photo/Charles Dharapak, File)