Peter has it right.

“Twenty years ago, a journal published by the Society for the Study of Addiction imagined a wondrous device:

“If people have difficulty overcoming both nicotine dependence and long-term habit change, then surely the solution is to help them avoid most of the health risks with only a minimal alteration in their nicotine-seeking habits. This implies a nicotine replacement device which looks like a cigarette and delivers cigarette-like boli of nicotine, but does not deliver the tar and carbon monoxide which cause he vast majority of smoking-related disease … the development and promotion of such a product [and its eventual replacement of tobacco] could have massive beneficial public health implications lasting into the 21st century.”

From http://www.pennlive.com/midstate/index.ssf/2014/02/electronic_cigarettes_e-cigare_1.html