OK, so I briefly read the source article in Environmental Science & Technology (
link) this morning. Note that the "supporting information" pdf is free to access, and Table S3 essentially contains all the relevant data in the paper.
Long story short: They appear to be operating under dry puff conditions.
Briefly, the study finds that the main source of harmful aldehydes (principally formaldehyde, acetaldehyde and acrolein) in vape aerosol is the flavourings, not VG/PG. Their evidence for this is that unflavoured e-liquid produces almost no concerning compounds. I think this is useful information to have.
They also found that concerning amounts of the aldehydes were present in the vape aerosol under their test conditions. So, let's look at the hardware setup:
Brand I: Kanger evod, 11W
Brand II: V2 cigalike, 5W
Brand III: CE4, 5W
Brand I (evod) produced the most aldehydes and the levels were concerningly high. Brand III (CE4) also produced high levels of aldehydes, Brand II (cigalike) was far lower. I'm not going to say anything more about the cigalike, because cigalikes are irrelevant here.
The CE4 was a 3 Ohm coil on an ego-T. Their power calculation is based on a nominal voltage of 3.9 V (should be 3.7 V AFAIK). The ego-T is a non-adjustable pen battery and outputs the battery voltage like a mech, it is not clear whether the device was always used with a fresh charge. Lots of potential for inconsistency here. This doesn't change the fact that high levels of adehydes were detected, it just leads me to question whether comparing results from different liquids used with this device is meaningful.
I used to vape with evods in 2013, and anyone who has will tell you 11 W is a recipe for a monster dry hit, 7-8 W was my upper limit. And this is where the alarming levels of aldehydes become less of a concern. The levels produced by the evod in this experiment are about 4-5 times higher than those previously demonstrated by Farsalinos to be
detectable as a dry hit (
link). Farsalinos showed in that paper that vapers detected and avoided dry hits as low as approx:
10 ug/puff formaldehyde
6 ug/puff acetaldehyde
^that is what a dry hit looks like in numbers.
Let's look at the evod:
35-50 ug/puff formaldehyde
18-28 ug/puff acetaldehyde
Ouch. Doubt I could vape that. Pretty much the fart of Satan you would expect from running an evod at 11W
And the CE4:
1-22 ug/puff
0-24 ug/puff
So highly variable and prone to dry hits. Well, we all knew that that is the classic CE4 experience.
Basically, it appears that these devices are being run in dry puff conditions and would not be vapable by a person. The authors of the study acknowledge that dry puffs exist, but do not mention any attempt to check whether they are measuring vapable aerosol or acrid dry hits. Given the numbers and the previous work by Farsalinos, I expect they are measuring dry hits, and once again we have a study that is not replicating real life vaping.