Definition: Electronic cigarettes (e-cigarettes) are battery-operated devices that heat a liquid usually containing nicotine, producing a vapor that the user inhales. E-cigarettes entered the market as consumer products without government regulation.
Conventional cigarettes burn tobacco and generate smoke, e-cigarettes have a cartridge containing a liquid (sometimes referred to as "e-liquid"), which contains nicotine and other constituents. The main components of the liquid vaporized is nicotine, propylene glycol or glycerol, and flavorings. A variety of other compounds have also been identified, some with carcinogenic potential.
The long-term health consequences of e-cigarette use are largely unknown but are likely to be less than continuing to smoke conventional cigarettes because e-cigarettes do not expose the user to many of the toxins in tobacco smoke. E-cigarettes expose users to nicotine as well as heated and aerosolized propylene glycol and glycerol and other compounds. The toxicity of chronic exposure to these and the other components of e-cigarettes is uncertain. We do not have long term data examining the health effects of e-cigarettes.
Nicotine Exposure: From e-cigarette use, as with cigarette smoking, increases heart rate and introduces levels of blood cotinine, a nicotine metabolite. The consequences of chronic inhalation of e-cigarette vapor are largely unknown, and levels of toxic and carcinogenic compounds may vary by e-cigarette liquid components and device used. We do know the potential adverse effects are related to nicotine exposure as well as exposure to other components in the vapor produced by the devices. There have also been documented emergency department visits for burns from electronic nicotine delivery systems (ENDS) due to device malfunction either while stored (eg, in a pocket) or during use, resulting in burns to the thigh, groin, face, and/or hand.
Passive Exposure: There is limited evidence on the health effects of passive vapor exposure and no conclusions can be drawn. Passive exposure to e-cigarette vapor produces small increases in serum cotinine, comparable with that from passive exposure to cigarettes. However, passive exposure to e-cigarette vapor is expected to be less toxic to bystanders than combustible cigarette smoke.
E-cigarettes are not approved by the US Food and Drug Administration (FDA) for smoking cessation and the FDA has not endorsed their safety or efficacy for smoking cessation. Using e-cigarettes is probably less harmful than smoking conventional cigarettes, but we do not know how safe they are to users or those around them. They continue the user's exposure to nicotine. The health consequences of vapor exposure are unknown, and there may be risks from inhaling e-cigarette flavorings on respiratory function.