“Mists containing propylene glycol, a liquid used to generate the vapor in e-cigarettes, can cause ocular and upper airway irritation,” states the research paper, oddly citing a study that looked at propylene glycol mist in aviation emergency training. If test conditions do not relate to actual vaping practice then it is hard to see how the results are relevant, and this goes for previous studies looking at PG too.
The team claim to be motivated by concerns over “recent studies [that] have measured harmful pollutants in vapour generated by e-cigarettes, including fine and ultrafine particles, reactive oxygen species, and toxic compounds associated with flavourants [sic].”
Their findings led them to state: “This study pinpoints key parameters influencing chemical emissions from e-cigarettes and identifies chemical pathways and vaping conditions that yield harmful compounds.”
In a way they did identify key parameters – but only through using the device in a manner that vapers would not. They used a simple CE4 style atomiser and a fixed head dual-coil system. Their puff machine then took 5 second puffs every thirty seconds for 10 minutes. Absolutely no vaper uses their device in this way.
“When you apply the same voltage to the double-coil e-cigarette you see a lot less emissions,” said co-author and Berkeley Lab researcher Lara Gundel. “We think it has to do with lower temperatures at each of the coil surfaces.”
They estimated that, even when pushed to this level, the atomisers released 90-100µg of acrolein. A tobacco cigarette releases 400 to 650µg of acrolein. There are two ways to look at this: as a positive step to harm reduction or, as they chose, to say, “All e-cigarettes emit harmful chemicals, but some emit more than others.”
They uncover information that offers more realistic advice for vapers. In relation to aging coils, they noted that toxin levels were increased with coils often referred to as having a build up of “coil gunk or caramelisation”.
“This effect is consistent with the buildup of polymerization byproducts on or near the coil leading to accumulation of … residues,” they say. “Heating these residues would provide a secondary source of volatile aldehydes.”
“Understanding how these compounds are formed is very important,” the study’s corresponding author Hugo Destaillats said. “One reason is for regulatory purposes, and the second is, if you want to manufacture a less harmful e-cigarette, you have to understand what the main sources of these carcinogens are.” As the University of California managed the study, we suspect it is more for the regulation and less for safer ecigs.