FILE - In this Feb. 20, 2014 file photo, a man exhales vapor from an e-cigarette in New York. A study at 10 Los Angeles high schools links e-cigarettes with later tobacco use. The government-funded study was published in Tuesday, Aug. 18, 2015 in the Journal of the American Medical Association. It doesn't prove that electronic cigarettes are a "gateway drug" but some doctors say it bolsters arguments that the devices need to be strictly regulated. (AP Photo/Frank Franklin II)