By Dr Farsalinos
As mentioned in my previous comment about the formaldehyde study published in NEJM, it is very important to identify which vape atomizer was used and what energy levels (watts) were applied to the atomizer in order to understand whether the findings were associated with overheating. As I calculated, based on the consumption reported by the authors, I considered 3.3 volts as being about 7 watts and 5 volts being 14-16 watts. It seems that I was pretty close.
According to a post on Reddit, the authors used a top-coil CE4 atomizer and an Innokin VV V3.0 battery. The Reddit user has forwarded the email response of the study author to me, so I have verified the content of the response and the equipment used (I have also sent an email myself to the authors, and I am expecting their response). My predictions in the previous comment about the overheating possibility have been completely verified, while I was quite close in my calculations about the wattage levels applied to the atomizer.
I should first mention that i have personal research experience with the use of top-coil atomizers. I tried to use a very similar top-coil atomizer in my study evaluating plasma nicotine levels from e-cigarette use. In that study, we used an EVIC e cigarette battery set at 9watts. Unfortunately it was impossible for most vapers to use the top-coil vape atomizer and puff at their preferred conditions, due to dry puff taste which they could not withstand. Only a small minority who were taking very short puffs were able to use this atomizer at 9 watts. So, I had to change the atomizer to a bottom-coil EVOD, which worked quite well at 9 watts. In fact, the average puff duration of the participants in that study was 3.5seconds. So, the top-coil atomizer used at 9 watts became overheated at puff duration less than the 4 seconds used in the NEJM study. This is not the first time that an atomizer was proven to be insufficient and resulted in dry puff phenomenon which was immediately detected by the vapers; in our vaping topography study I specifically mentioned: “Originally our intention was to test another atomiser (“eGo-C”, Joyetech); however, some EC users experienced overheating of the atomizer and a phenomenon known as “dry-puff” (unpleasant, burning taste caused by insufficient supply of liquid to the resistance so that evaporation rate is higher than liquid supply-see the Discussion section for more details). They had to lower the puff duration and increase the inter-puff interval in order to avoid this phenomenon. In response to that, the eGo-C was substituted with “Epsilon” and participants were asked to come back for recordings with the new atomizer. All recordings with the eGo-C atomizer were discarded”. The authors of the NEJM study should have read our study and should have known about the existence of this phenomenon.
According to the Reddit post and author’s email, the vape atomizer had a resistance of 2.1 Ohms. This means that at 3.3 volts, the energy delivery was about 5.5 watts and at 5 volts it was 12 watts. It is more than obvious that the findings of very high levels of formaldehyde are a result of overheating. Lack of experience on e-cigarettes and no contact with vapers can result in such erroneous and unrealistic results, which can create confusion and misinformation both in the scientific community and among users and potential users of e cigarette. Finally, it is extremely important that every study evaluating vapor chemistry from e cigarette should mention in detail the equipment used.