Individual's reactions and sensitivities (talking comfort around stuff like irritation) will vary. But that's not really a safety issue as that's a minor side effect. The issue is what happens when you break up vapers into different cohorts.
The most common cohort around this place is ex-smoker using vaping to stay off of them. Generally an older population possibly/probably with some health issues related to their decades of smoking. In this cohort, I think there's excellent evidence that vaping is the way to go. Maybe a little fine tuning which you might individually decide is of value for an incremental increase in safety, or just happy to go along as is, unless it's discovered (and as unlikely) that it will result in a second head growing out of your shoulder.
The second cohort are nonsmokers who turn to vaping, with or without nic in it. Occasional use, like social smoking for those that remember it, is probably not going to add additional risk to their health of any significance. A subset of that cohort are nonsmokers who vape daily, and have no intention of stopping. Now there may be folks in that group who would otherwise turn to cigarettes if vaping were not available, in which case the benefits of vaping over smoking would be in their favor. But for others who would otherwise never smoke, long term safety remains unknown.
The reason we talk about it as harm reduction is because that's a different issue than safety. Safety is an absolute, harm reduction is a risk/benefit analysis. I think we all should keep that in mind, especially when discussing this with the ANTZ crowd, as their standard is safety, while ours is harm reduction. Even the "95% safer" really must presented as a 95% reduction in risk (or more or less if the evidence bears it out).That creates a different discussion than a "this is way safer" discussion. Some might feel that's just playing with semantics, but it's really being more precise in what we're addressing and why.
And this is why I said, when it comes to safety - absolute safety verses real harm factors, we will never medically be able to ascertain the answer using cohort #1 as our test group.
Will it cause cancer? Won't be able to answer that question with group #1, as smoking does cause cancer and that group has been steeped in cancer causing chemicals.
Will it cause lung scarring if used in long term? Can't answer that using group #1 because our lungs are already irreversibly damaged.
What kind of damage will it cause to lung tissue? Cannot answer that with group one either..
Only group #2 can answer real long term harm.
We can all answer in the acute short term, but only one group, group #2, can answer long term risks associated with vaping...
To my knowledge, acute short term affects and problems have been appropriately dealt with by the industry to date, and since I'm not in group two, and we know by the multitudes of healing bodies that it is
far better than smoking, so I see most of these questions posed by the OP to be wholly irrelevant at this time.
What they are trying to ascertain, from what I'm gathering is safety as an absolute measurable quantity, no one can say that yet, as we don't have a large enough pool that has been able to be examined in long enough term to measure the absolutes. All we can do is measure short term.. and that can and is being addressed on a daily basis.
People say 10 years is plenty long, but it's not long enough to say vaping causes cancer, or causes x amount of lung damage in the long term when vaping high watt 100% vg verses x amount of damage when vaping low watt pg/vg mix or flavor groups abc cause x amount of damage verses no flavors.. those types of long term studies where an absolute can be learned can only be done using cohort group #2, and we need longer than 10 years studying them.
Now, if I'm wrong here as far as the type of studies and the type of information the OP is desirous of getting from pro-vaping studies verses anti-vaping studies then I've simply been lost this whole thread. But if your looking for a certain kind of information about harm, and your not seeing it in what you deem an appropriate manner, there is usually a reason for that and it's not because studies are biased, but rather, because the studies cannot yet be done. I've yet to see anyone say there will never be harm found, and I've never seen acute short term harm not be addressed within the vaping community when it rears its ugly head, which leaves only one type of harm left.. and that's a harm that is absolute and long term.
And, as Robin has already kindly pointed out, we dont even know if that group will vape in the long term, especially with vaping being devoid of the majority of addictive qualities/chemicals that are inherent in smoking cigarettes - therefore those questions may well be a reasonably moot point.
After 14 years of smoking i was an addict that couldn't quit. Will the same level of addiction be present for a vaper who never smoked? Most believe it's doubtful.. and I concur with that belief.