Nov. 16, 1942
Published way back in 1942, This article from TIME magazine touches on the possibility that Propylene Glycol could be used as a germicide. Through various experiments, scientists found that PG is very strong against certain respiratory ailments.
“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.”
“…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.”
“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.”
In case you were wondering about the respiratory effects of the PG, here is a further experiment. Not quite the most precise measurements, but interesting nonetheless.
“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.”
Another article published in Dec. 1943 further reports on experiments with Propylene Glycol as a germicide.
“To prevent colds, Pediatrician Joseph Stokes Jr. and Dr. Tzvee N. Harris used propylene glycol vapor (TIME, Nov. 16, 1942) last winter to spray the air of six wards containing 105 children at the Children’s Seashore House in Atlantic City. While the wards were being sprayed, three children came down with colds. While the wards were unsprayed, 79 got colds.”
I was stoked find this article on Twitter (sorry, I forgot who posted it! I apologize!) about a study using Propylene Glycol for medical usage. The study is from 2007, but it yields some interesting finds.
The study was for a medicine, Cyclosporine, to be delivered through inhalation to patients that had undergone lung transplants. Their intention is to deliver an immunosuppressant directly to the allograft, or transplated organ. They were testing the toxicity of the aerosolized medication given by inhalation. They were tested on rats and dogs for 28 days.
The outcome was promising. Giving at 2.7 times the maximum human exposure, “There were no respiratory or systemic effects of high doses of propylene glycol relative to air controls. These preclinical studies demonstrate the safety of aerosolized cyclosporine in propylene glycol and support its continued clinical investigation in patients undergoing allogeneic lung transplantation.”
While the study shows that the medication delivery was successful, reaching far greater concentrations in the lung tissue instead of the blood, I was excited to hear that it seems that high doses of PG seems to be safe. It’s definately food for thought and good news for people using the solution in electronic cigarettes.