As the popularity of electronic cigarettes has grown over the past several years, so have concerns over the health risks tied to them. So, what’s in e-cigarettes?

That’s not an easy question to answer. No federal agency oversees the e-cigarette industry. That means no standards exist. Labels may inaccurately describe ingredients, and what you find in one brand may be vastly different from that found in another, for better or worse.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.”