A Harvard study found many flavored Vaping fluids to contain the chemical Diacetyl, which is commonly linked to serious lung diseases like Bronchiolitis obliterans, which is an irreversible inflammatory lung disease. Those with Bronchiolitis obliterans ususally have such severe damage to their lungs, they have no other choice but to undergo lung transplants. Yeah...oh, and the link:

EHP ? Flavoring Chemicals in E-Cigarettes: Diacetyl, 2,3-Pentanedione, and Acetoin in a Sample of 51 Products, Including Fruit-, Candy-, and Cocktail-Flavored E-Cigarettes

I wont buy into how seeming "harmless" vaping is. It's just as bad, if not worse than, smoking cigarettes.