Aromatic hydrocarbons in second-hand vaping: our response published today in International Journal of Hygiene and Environmental Health‏


By Dr Farsalinos

Many of you have probably seen the latest study on second-hand vaping published in International Journal of Hygiene and Environmental Health‏. A group of German researchers evaluated emissions from e-cigarette use by asking volunteers to vape in a 45m3 clean and well-ventilated room. They measured baseline environmental pollutants on day 1 and on days 2 to 5 when users consumed 4 different types of e-liquids (2 of them with and 2 without nicotine). The main findings from the study were that PAHs were elevated by 20% compared to baseline, and, once again, particulate matter was found at high levels and with very small size.

I prepared a letter to the editor about this study, which was accepted and published today, after the peer-review processwas finalized. We presented and emphasized the main limitation of their protocol design, that the baseline conditions were not evaluated just before e-cigarette use but on a separate day. We noted that environmental levels of PAHs have a significant day-to-day variability; therefore, it is highly likely that any differences were associated with changes in environmental conditions. Characteristically, the authors found lower PAHs levels after using a non-nicotine liquid compared to baseline, which of course cannot be considered as an indication that e-cigarette use may reduce environmental pollution! Moreover, we noted that levels of urinary 3-HPMA (a metabolite of acrolein) were elevated only after use of nicotine-containing e-liquids. There is no scientific justification for this, since acrolein is produced from thermal degradation of glycerol and not from nicotine. Another problem we noted was associated with the reported elevations in exhaled FeNO levels. This is in direct contrast with the findings by Vardavas et al; however, both groups presented their findings as an indication of inflammatory response! We specifically mentioned that all participants had exhaled FeNO levels within normal limits (both before and after e-cigarette use) with the exception of one participant whose baseline levels were also elevated. Moreover, no placebo was used to evaluate for the possibility of chance changes in exhaled FeNO. The issue of particulate matter (PM) was once again mis-presented, by implying that PM from e-cigarette emissions is similar to smoking or environmental pollutant PM. In reality, e-cigarettes emit mainly propylene glycol and glycerol microparticles, which is completely irrelevant to the combustible and toxic chemicals which constitute what we usually call PM. Finally, the issue of nicotine intoxication was grossly exaggerated by presenting the myth of the 40-60mg lethal dose of nicotinehis was addressed in our letter too.

It was interesting to read the response of the authors to our letter. They noted that outdoor PAHs are usually at levels 20 to 500 times lower than what they measured indoors. So, they support that the difference cannot be associated with variations in outdoor pollution. However, they do not explain why such high levels of PAHs were measured indoors. That was supposed to be a clean and well ventilated room, and meticulous cleaning was performed after each vaping session. Unless they did the measurements in a kitchen of a restaurant (where oils are burned all day) it is hard to understand where all these PAHs came from. In any case, it is fundamentally wrong to check for baseline conditions on a different day and without the subjects inside the room. This principle was correctly followed in the study by Schripp et al, who found that formaldehyde was emitted from the breath of the participant and not from the e-cigarette aerosol. For the issue of acrolein metabolite measured in urine, they consider the change after nicotine-free vaping as slightly significant. But the p value they report (0.06) is not statistically significant, therefore any change has absolutely no meaning and should not be reported. For FeNO, they mentioned that there is no need to use a placebo because “There were also no measurement procedures that are known to bias FeNO.” This is an unprecedented statement, and of course has absolutely no scientific basis. For the issue of PM, they acknowledged that the composition is different, and added that “it cannot be deduced from this, that long-term inhalation of 1,2-propanediol nano-droplets must be completely safe.” Well, in a similar way we can support that there is currently no evidence showing that inhalation of 1,2-propanediol (PG) nano-droplets is unsafe.

I think it is important that any scientific studies with serious methodological issues must be noted and presented through letters to the journals, and we will continue in our efforts to expose the truth and to raise concerns about errors in published research.




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