The questions you raise are addressed in the 2011 Harm Reduction Update by Brad Rodu, posted on www.aaphp.org/tobacco. If you go to that page, click on the top item on that page, and download the full 22 page text, you will find the following:
Please keep in mind that, given the 15-25 year incubation period between starting smoking and onset of potentially fatal cancer, heart and lung disease in smokers, almost all of the 8 million (400,000 per year x 20 years) persons who will die of a tobacco-related disease (not counting deaths due to environmental tobacco smoke) are currently adults over 35 years of age. Those of us supportive of tobacco harm reduction believe that a well coordinated tobacco harm reduction initiative could save the lives of half of those smokers, and do so in a way that will have little or no impact on teen initiation of tobacco/nicotine use. It is that belief that is driving me to bring this topic up for discussion within AAPHP, and, hopefully, through AAPHP to AMA and other health-related organizations.
The literature supporting the premise that smokeless tobacco is not a gateway to smoking, issues related to dual use and electronic cigarettes are also discussed in the 2011 Harm Reduction Update, with literature references provided.
Joel L. Nitzkin, MD
Past co-Chair, APPHP Tobacco Control Task Force