Designated Vaping

Is Propylene Glycol Dangerous?

The main liquid base in e-juice is Propylene Glycol.  Some people say we don't know what is in it and what its effects are on the human body.

We do know.  There has been research.  Decades of research.  For instance, this article was from 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.

This venture gave promising results, but all such research lapsed for another decade. Within the last few years, several research groups (notably the University of Pennsylvania’s new Air-Borne Disease Laboratories) again began testing various sprays. Many chemicals were found to kill airborne micro-organisms quickly, even in concentrations as low as one gram of chemical per 500 cu. ft. of air.

Trouble was that all these air germicides smelled bad, or were toxic, or irritated the respiratory tract. Dr. Robertson’s propylene glycol vapor is odorless, tasteless, nontoxic, non-irritating, cheap, highly bactericidal.

Its discovery was accidental. Dr. Robertson and his colleagues were trying out another possible germicide—a detergent or “soapless soap” (similar to Dreft, Aerosol and other products widely sold for household and industrial use). Water solutions of the detergent were only mildly effective, so the researchers tried solutions of detergents in propylene glycol, which is a sort of thin glycerin.

Results were much better. Then the researchers found that the propylene glycol itself was a potent germicide. One part of glycol in 2,000,000 parts of air would—within a few seconds—kill concentrations of air-suspended pneumococci, streptococci and other bacteria numbering millions to the cubic foot.

How did it work? Respiratory disease bacteria float about in tiny droplets of water breathed, sneezed and coughed from human beings. The germicidal glycol also floats in infinitesimally small particles.

Calculations showed that if droplet had to hit droplet, it would take two to 200 hours for sterilization of sprayed air to take place. Since sterilization took place in seconds, Dr. Robertson concluded that the glycol droplets must give off gas molecules which dissolve in the water droplets and kill the germs within them.

Dr. Robertson placed groups of mice in a chamber and sprayed its air first with propylene glycol, then with influenza virus. All the mice lived. Then he sprayed the chamber with virus alone. All the mice died.

Propylene glycol is harmless to man when swallowed or injected into the veins. It is also harmless to mice who have breathed it for long periods. But medical science is cautious—there was still a remote chance that glycol might accumulate harmfully in the erect human lungs which, unlike those of mice, do not drain themselves.

So last June Dr. Robertson began studying the effect of glycol vapor on monkeys imported from the University of Puerto Rico’s School of Tropical Medicine. So far, after many months’ exposure to the vapor, the monkeys are happy and fatter than ever. Dr. Robertson does not expect mankind to live, like his monkeys, continuously in an atmosphere of glycol vapor; but it should be most valuable in such crowded places as schools and theaters, where most respiratory diseases are picked up.


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