Study: Propylene glycol vapor kills airborne bacteria, including streptococci

While the smoking of combustible tobacco is proven to diminish the immunity system and making smokers more susceptible to colds and the flu, decades-old research indicates that vapers may have a secret advantage.  In multiple studies conducted as far back as the 1940s, Dr. Theodore Puck was successful in proving that the vapor produced from propylene glycol kills several forms of airborne bacteria. Perhaps most noteworthy are streptococci, pneumococci, staphylococci, the influenza virus, and other microbes.   

Propylene glycol is a major component of e-liquids used in both open-tank vaping devices and disposable e-cigarettes.  It’s also an artificial sweetener commonly used in baked goods, cake frostings, and ice creams, which means that it is approved by the U.S. Food and Drug Administration and considered safe for human consumption.

The Black Plague, propylene glycol, and respiratory disease

In his 1943 study entitled The Bactericidal action of propylene glycol vapor on microorganisms suspended in air (NLB-NIH), Dr. Puck discovered that when propylene glycol is heated to a mere 80 degree Fahrenheit, it’s vapor can significantly help patients living with a variety of respiratory diseases.  Even though mass-marketed vaping had not yet been invented, Puck accidentally stumbled upon his findings when researching The Black Plague of the 14^th century in England. 

Always intellectually curious since he was a young boy, Puck was always intrigued about how and why the Black Plague ended.  While the disease would linger in Europe for centuries, the city of London was somewhat successful in eradicating it seemingly overnight after the plague had killed approximately 70,000 Brits between 1665-66.   How did they do it, Puck always wondered?

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After reading piles of historic documents, Puck soon learned that the citizens of London were so overwhelmed by death and suffering that they eventually decided to literally burn the town to the ground.  The theory at the time was that the fire would destroy whatever pathogen or bacteria that was causing the deadly outbreak. 

Strangely, their arson-inspired logic seemed to work.  Almost immediately after the fire, cases of the Black Plague began to drop sharply.

The Black Plague was caused by yersinia pestis, a bacterium commonly found on rodents and typically transmitted to 14^th century Londoners by flea bites.  Dr. Puck theorized that something in the ashen air must have contributed to the outbreak’s demise by killing this Yersinia pestis bacterium. 

He began testing all sorts of substances before stumbling upon propylene glycol. Not only did Puck determine that this e-liquid ingredient kills yersinia pestis, but he also found that it eradicates several kinds of bacteria known to cause all kinds of illness in humans.  Streptococci alone can cause impetigo, scarlet fever, and of course, the notorious strep throat (pharyngitis). 

“The killing of air-suspended bacteria by means of very small concentrations of vapors of various compounds, particularly propylene glycol and triethylene glycol, was reported. Under the experimental conditions employed, numerous kinds of bacteria, including pneumococci, hemolytic streptococci, staphylococci, influenzae, etc., as well as influenza virus, when sprayed into atmospheres containing such vapors, were killed so rapidly that no microorganisms or virus could be recovered from the test chamber. Propylene and triethylene glycols were chosen for especial study, since these compounds are relatively non-toxic and in vapor form are odorless, tasteless, and non-irritating to the respiratory mucosa. The degree of germicidal activity of the vapors was observed to depend upon the concentration of the glycol in the atmosphere. Furthermore, the effectiveness of any given concentration of glycol vapor could be changed markedly by altering certain experimental conditions, such as the volume of culture inoculum atomized into the air, the number of bacteria per unit of volume, the relative humidity and temperature of the atmosphere, and the state of bacterial suspension.”

Dr. Theodore Puck’s research was considered so revolutionary that the New York Times reported on his death in 2005.   His research was also used as the building blocks for more recent studies in the field of vaping research.  For example, the California Department of Public Health announced in 2017 that the toxicities exposure of second-hand e-cig vapor is negligible, especially when compared to the smoking of combustible tobacco cigarettes.

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