"In summary, only a few studies have directly investigated the health effects of exposure to e-cigarette aerosol, but some demonstrate the ability of e-cigarette aerosol exposure to result in biological effects. Long-term biological effects are unknown at this time because e-cigarettes have not been in widespread use long enough for assessment."
Source
Rachel Grana, Neal Benowitz and Stanton A. Glantz, "Contemporary Reviews in Cardiovascular Medicine: E-Cigarettes: A Scientific Review," Circulation (Dallas, TX: American Heart Association, May 13, 2014). 2014;129:1972-1986. doi: 10.1161/CIRCULATIONAHA.114.007667, p. 1978.
http://circ.ahajournals.org/c…
http://circ.ahajournals.org/c…
