Electronic Cigarettes and Vaping: A New Challenge in Clinical Medicine and Public Health. A Literature Review http://w ww.n cbi.nlm.nih.gov/pmc/articles/PMC3859972/ It's not a very recent review and progresses have been made since then. This review offers an unbiased summary of scientific findings about ecig in health and in harm reduction compared to smoking. You will find many things that you already know with precise numbers and references. A good source of knowledge for education purposes and precise information for health related debates.