Table 1.

Main factors determining the public health impact of electronic cigarettes.

Factor	Details
Safety/risk profile	The safety/risk profile of e-cigarettes should be determined both relative to smoking, to inform smokers about the relative risks, and in absolute terms to inform never-smokers about potential risks from adoption of use.
Effectiveness on smoking cessation and reduction	The intended use of e-cigarettes (from a public health perspective) would be as smoking substitutes. Studies need to assess their real-world effectiveness in this aspect as well as any possible unintended consequences such as delaying or hindering smoking cessation.
Patterns of use by population subgroups	Ideally, e-cigarettes should be used only by current and former smokers. Their popularity among never-smoking adults needs to be monitored. Additionally, monitoring use by adolescents is important to determine how it affects smoking initiation and prevalence at a young age, which is a major predictor of long-term sustained smoking.