I'm not sure how much propylene glycol vapor exists within a single puff from an E-Cig, but here's some interesting information about part of what we're breathing with these things. (Excerpt from article)
[SIZE=-1] From the Department of Medicine, the Douglas Smith Foundation for Medical Research, the Bartlett Memorial Fund, and the Zoller Memorial Dental Clinic of the University of Chicago, Chicago
[/SIZE] It has been found that propylene glycol vapor dispersed into the air of an enclosed space produces a marked and rapid bactericidal effect on microorganisms introduced into such an atmosphere in droplet form. Concentrations of 1 gm. of propylene glycol vapor in two to four million cc. of air produced immediate and complete sterilization of air into which pneumococci, streptococci, staphylococci, H. influenzae, and other microorganisms as well as influenza virus had been sprayed.
The full article is located at: http[:]//jem.rupress.org/cgi/content/abstract/75/6/593
(For those that don't know, remove the brackets from around the ":" after the "http."
[SIZE=-1] From the Department of Medicine, the Douglas Smith Foundation for Medical Research, the Bartlett Memorial Fund, and the Zoller Memorial Dental Clinic of the University of Chicago, Chicago
[/SIZE] It has been found that propylene glycol vapor dispersed into the air of an enclosed space produces a marked and rapid bactericidal effect on microorganisms introduced into such an atmosphere in droplet form. Concentrations of 1 gm. of propylene glycol vapor in two to four million cc. of air produced immediate and complete sterilization of air into which pneumococci, streptococci, staphylococci, H. influenzae, and other microorganisms as well as influenza virus had been sprayed.
The full article is located at: http[:]//jem.rupress.org/cgi/content/abstract/75/6/593
(For those that don't know, remove the brackets from around the ":" after the "http."