But the manufacturer doesn't have to disclose that information if there's no regulation compelling them to, or they can downright lie if nobody's there watching them. Or just put random shit in there that hasn't been tested for safety.
http://www.webmd.com/smoking-cessation/news/20150218/e-cigar...
>The results of one FDA review of 18 different e-cigarette cartridges found toxic and carcinogenic chemicals in some but not others. All but one of the cartridges labeled “no nicotine” did, in fact, contain nicotine. The authors suggest that “quality control processes used to manufacture these products are inconsistent or non-existent.”
> Flavorings: Goniewicz says hundreds of flavors exist, including cherry, cheesecake, cinnamon, and tobacco. Many of those flavoring chemicals, he says, are also used to flavor food.
>“These are the big unknowns,” he says. “When we eat them, they are safe, but we don’t know what’s going on when we inhale them.”