E cigarette use and associated changes in population smoking cessation: evidence from US current population surveys The BMJ E cigarettes linked to lung problems, first long term study on vaping finds Frontiers Trace Metals Derived from Electronic Cigarette (ECIG) Generated Aerosol: Potential Problem of ECIG Devices That Contain Nickel Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products: A Scientific Statement From the American Heart Association Circulation Vaping Increases Lung Disease Risk Even Without Smoking Tobacco: Study Business Insider