- Wednesday, 08 April 2015 16:24
By Dr Farsalinos
A new study was published today in International Journal of Environmental Research and Public Health. Researchers from Germany evaluated the cytotoxic potential of e-cigarette vapor (from 0% and 2.4% nicotine-containing liquids). They were also “brave enough” to compare the effects with tobacco cigarettes. Although this should have been the norm, you rarely see any cytotoxicity study today comparing e-cigarettes with tobacco cigarettes.
The study had some methodological problems. Firstly, they compared 200 puffs of e-cigarettes with 60 puffs of tobacco cigarettes, but the researchers correctly made the necessary normalization in the final results presentation. An important issue was that the e-cigarette was puffed consecutively, with minimal interpuff interval (probably 7 seconds, which was reported as “blow-out” time). This has probably resulted in overheating of the liquid (despite taking 2 second puffs). However, the results clearly showed that oxidative stress and cell death were much lower after e-cigarette exposure compared to tobacco cigarette exposure. In many cases, the results of e-cigarettes were close to the control measurements (exposure to clean air).
Note: after contacting the leading author I was informed that the interpuff interval was 10 seconds, while 7 seconds was the time for the piston pump to blow all the vapor to the cell culture. Although the authors of the study disagree, I insist that overheating may have been an issue with such a short interpuff interval, which could result in the production of aldehydes.
The study verifies our previous findings from two cytotoxicity studies (here and here), which showed that tobacco cigarettes were by far more cytotoxic than e-cigarettes. The German group acknowledges this in their publication. Of course, this was possible because the authors decided to use tobacco cigarettes for comparison. In many other recent studies the authors avoided any comparison with tobacco cigarettes, leading to erroneous conclusions about adverse effects from e-cigarette use in smokers, which were completely irrelevant to the study purpose and methodology. This German study verifies all previous conclusions and confirms that results of e-cigarette research are perfectly reproducible when proper methodology is followed.