here is an interesting article to read Propylene glycol in e cigarettes might keep us healthy, says researchers

I think I'll go blow some vapor in my wife's face. Hey, it's healthy, right?![]()

Monday, Nov. 16, 1942
A powerful preventive against pneumonia, influenza and other respiratory diseases may be promised by a brilliant series of experiments conducted during the last three years at the University of Chicago's Billings Hospital. Dr. Oswald Hope Robertson last week was making final tests with a new germicidal vapor—propylene glycol—to sterilize air. If the results so far obtained are confirmed, one of the age-old searches of man will finally achieve its goal.