In the first study of human exposure produced by passive vaping under real-life conditions, researchers from Italy and Greece found no chemicals of concern in room air while five electronic cigarette users vaped for a five-hour session in a 60 cubic meter closed room.
The researchers compared the constituents of room air during passive vaping to those present during passive smoking. During passive smoking, levels of chemicals were as follows (all in micrograms per cubic meter):
Polycyclic aromatic hydrocarbons: 9.4
Carbon monoxide: 11
The detected levels of these same chemicals during the passive vaping session were as follows:
Polycyclic aromatic hydrocarbons: 0
Carbon monoxide: 0
(Romagna G, Zabarini L, Barbiero L, Bocchietto E, Todeschi S, Caravati E, Voster D, Farsalinos K. Characterization of chemicals released to the environment by electronic cigarettes use (ClearStream-AIR project): Is passive vaping a reality? Presented at the 14th Annual Meeting of the Society for Research on Nicotine and Tobacco, 2012, Helsinki, Finland.)
The Rest of the Story
These results should be viewed as preliminary, especially because only one brand of electronic cigarettes was tested. There could be variability between various brands, so no firm conclusions should be drawn until many brands of electronic cigarettes are tested under realistic exposure conditions.
Nevertheless, these results seem to suggest that electronic cigarettes at least have the potential to present little risk to bystanders. Not only can we say that there is currently no evidence that passive vaping is harmful, but we can now say that the first study to examine passive vaping under realistic conditions found no chemicals of concern in the ambient air.
One previous study (Flouris et al., 2013) did find an increase in serum cotinine levels in nonsmokers exposed to passive vaping; however, that study involved blowing air using an air pump into an experimental chamber. It did not involve the actual, real-life use of electronic cigarettes by humans. Also, that study measured only serum cotinine; it did not measure the levels of contaminants in the ambient air.
Stan Glantz and others have been using that study to argue that passive vaping is hazardous to bystanders. Of course, they ignore the results of the present study - the only one to be conducted under realistic conditions and to actually measure potentially hazardous chemical exposures. The finding that there were no detectable levels of nicotine, acrolein, polycyclic aromatic hydrocarbons, carbon monoxide, xylene, and toluene is inconvenient to Glantz's argument that electronic cigarettes are a significant health hazard to non-vaping bystanders.
Glantz and others also fail to inform the public that the Flouris et al. study -- which they tout as demonstrating the significant hazards of passive vaping - actually showed that exposure to electronic cigarette vapor in the experimental chamber for one hour had no effect on acute lung function of nonsmokers. This was in contrast to secondhand smoke, which adversely affects acute lung function.
The rest of the story is that there is no current evidence that passive vaping poses any significant threat to the health of bystanders. Thus, I do not see any public health justification for banning vaping in public places at the present time.