In a April 10, 2018, file photo, a high school principal displays vaping devices that were confiscated from students in such places as restrooms or hallways at the school in Massachusetts. With one in four teenagers now using electronic cigarettes, underage vaping is universally condemned, and the federal government considers it an epidemic. But some other researchers believe recent trends continue to show vaping’s promise as a tool to steer millions of adult smokers away from cigarettes, the nation’s leading cause of death. (AP Photo/Steven Senne, File)