"17. In summary, the existing evidence shows that ENDS aerosol is not merely 'water vapour' as is often claimed in the marketing for these products. ENDS use poses serious threats to adolescents and fetuses. In addition, it increases exposure of non-smokers and bystanders to nicotine and a number of toxicants. Nevertheless, the reduced exposure to toxicants of well-regulated ENDS used by established adult smokers as a complete substitution for cigarettes is likely to be less toxic for the smoker than conventional cigarettes or other combusted tobacco products. The amount of risk reduction, however, is presently unknown. The 2014 Surgeon General's Report concluded that non-combustible products such as ENDS are much more likely to provide public health benefits only in an environment where the appeal, accessibility, promotion, and use of cigarettes and other combusted tobacco products are being rapidly reduced.7

Source

Electronic Nicotine Delivery Systems, Report by World Health Organization to 6th Session of the Conference of the Parties to the WHO Framework Convention on Tobacco Control, July 21, 2014, p. 5.
http://apps.who.int/gb/fctc/P…