I would argue that it is flawed though as the PG is mixed with Ethylene Glycol which we dont use in Ecigs. Id be more inclined to agreeing or seeing the possibility if the EG wasnt involved. I have read tremendous amounts of studies on PG and in one where rats, exposed in environments where PG was pumped into the oxygen, there were no issues found. Over a course of months of continuous inhalation 24hrs a day. In humans exposed to similar conditions of continuous for hours, the most prevalent complaint was sore throat and dry mouth. i posted the links to the studies somewhere on here just a few weeks ago, they were a collective of studies from the 1940's to present as well.
I appreciate that the study in question focus on several compounds, and that there are studies suggesting exposure to pg in saturation conditions doesn't give raise to particularly worrying short term effects.
However, we are talking about different things and we have different concerns.
The long term effects I am interested in are those arising after a number of years of continual exposure, or even some kind of less intensive exposure, dependently on the compound we are investigating.
From how you describe the findings of the studies you refer, it seems to me they mostly considered detectable effects over a short period.
The equivalent of this for smoking would be to say that after several hours continual exposure to smoke most subjects would lament a certain sore throat, over several days of exposure with interruptions, many subjects would notice that exposure actually seems to attenuate the sore throat.
The vast majority of subjects will also find that throat irritation will disappear pretty rapidly if exposure cycles are days apart or stopped completely.
Actually, a certain number of subject won't suffer any irritation, it will take many years (15 in my case) for this to become apparent and chronical.
What does this tell me about the range of cancers, vascular pathologies and so forth smoking is believed to lead to? Nothing.
Conversely, data about hundred thousands patients, active smokers, passive smokers and non smokers, over say 30 years, will tell me there is what looks like a correlation.
The study I mentioned is interesting to me because it takes this kind of approach, and is therefore indicative of this type of long term effects. Then, it might well be not flawed, but not useful enough given it focusses on a range of compounds, not only PG.
But the methodology is the right one.
I didn't stop smoking because of the sore throat, personally.