[E-Cigarettes: Assessment of Health Effects and Potential Benefits for Smokers]

E-cigarettes are electronic devices used to vaporize a flavored liquid resulting in aerosols to be inhaled by the user. The high variety of e-cigarettes and liquids makes it difficult to assess the health effects of e-cigarette use. The ingredients of the liquids - apart from nicotine - are generally recognized as safe for oral and dermal use, however, toxicological data on health effects upon chronic inhalation are missing. Studies have detected several harmful substances in e-cigarette aerosol, including carcinogens, but in lower concentrations than tobacco smoke. Evidence suggests that e-cigarette use entails acute health effects such as inflammatory responses in the lung. In animal and in vitro studies e-cigarette aerosol showed adverse effects like cytotoxicity, increased infiltration of inflammatory cells and pro-inflammatory cytokines, increased oxidative stress and moderate inflammation. Compared to tobacco smoking e-cigarettes are very likely to be less harmful, however, due to scarce data the extent of harm reduction cannot be quantified. Although smokers often use e-cigarettes to quit smoking, currently they are not approved as smoking cessation aids. As e-cigarette aerosol is a new source of air pollution, it is reasonable to assume that it poses an increased health risk to bystanders, in particular to vulnerable persons such as children and people with health conditions. E-cigarettes can have a positive effect on public health, if many smokers completely switch from smoking tobacco to e-cigarettes and, finally, also stop e-cigarette use, and if at the same time adverse consequences (such as increased initiation among youths) remain limited.