Dear Harvard: Research shows vaporized propylene glycol kills airborne bacteria

Harvard scientists published a vaping study last week suggesting that some e-liquids manufactured in the United States are laced with trace amounts of microbes and microbial toxins.  The study has since caught the attention of nearly every major anti-vaping organization in the country, resulting in gross misrepresentations of the report’s true findings that have since gone viral across social media. 

There are several problems with the study.  First of all, the scientists tested 75 different electronic cigarettes, all of which were first-generation technology.  Even the U.S. Food and Drug Administration (FDA) has no apparent beef with antiquated cigalikes and vape cartridges.  It’s Juul pods that the agency seems to despise so aggressively.

But perhaps the most troubling issue related to the Harvard vaping study is that the researchers only tested the e-liquids.  They failed to test the actual aerosol vapor produced from said e-liquids. One would think that Harvard scientists would be just a tad bit smarter, would one?

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The Harvard vaping study entitled Endotoxin and (1→3)-β-D-Glucan(1→3)-β-D-Glucan Contamination in Electronic Cigarette Products Sold in the United States is available via Environmental Health Perspectives.  According to the published findings, some of the e-liquids tested positive for trace levels of two district microbials, endotoxin and glucan. Both microbials are also present in the smoke produced from conventional tobacco cigarettes, and to much higher levels compared to those of vaping. 

“To our knowledge, this study is the first to identify endotoxin and glucan in EC cartridges and e-liquids sold in the United States. Endotoxin was detected in 17 of 75 (23%) of EC samples, and glucan was detected in 61 of 75 (81%) of EC samples. After adjusting for brand and flavor, the estimated mean glucan concentration in EC cartridges was 3.2 times higher (95% CI: −0.10−0.10, 18) than in concentrations found in e-liquids. When adjusted for brand and product type, glucan concentrations in tobacco- and menthol-flavored ECs were 10 times (95% CI: 1.8, 45) and 3.5 times (95% CI: 0.11, 17) higher than concentrations in fruit-flavored ECs, respectively.”

While discovering that e-liquids may contain small amounts of bacteria may sound somewhat alarming at first blush, it’s not really all that unexpected.  The chances of a scientist finding similar trace results after testing another publicly purchased product like a bottle of aspire, for example, are also fairly high.  However, the major difference between a bottle of aspirin and a bottle of e-liquid is that consumers don’t drink the latter.  They load it, burn it, and inhale its vapor.

The Puck study on vaporized propylene glycol

As far back as the 1940s, scientists have known that vaporized propylene glycol – a primary ingredient of e-liquids – kills numerous forms of airborne bacteria.  In a study entitled The Bactericidal action of propylene glycol vapor on microorganisms suspended in air (NLB-NIH), lead author Dr. Theodore Puck made several revolutionary scientific discoveries.  When heated to temperatures that are closely associated with today’s standard vaping practices, the Puck team concluded that vaporized propylene glycol eviscerates many forms of bacteria, including pneumococci, streptococci, staphylococci, and even the influenzae virus. 

While the existence of the Puck research does not disprove the Harvard vaping study automatically, it does raise serious concerns about the researchers’ scientific research protocols.  Why did they test the e-liquid and ignore the e-liquid vapor?  Why did they test e-liquids associated with old-fashioned technology and ignore the much-in-the-news Juul pods that the FDA despises so much?  And why did the scientists not research the basic ingredients of vape juice like propylene glycol and vegetable glycerin to determine their potential bacterial toxicities prior to conducting their germ tests?  To this reporter, the Harvard study appears to be either intentionally manipulated based on an anti-vaping bias, or the researchers were severely dropping the proverbial ball scientifically speaking. 

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(Image courtesy of Shutterstock)

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