Okay, so let's say for sake of discussion that a pack of smokes has 6500 micrograms, and (just for sake of making a point) that an eLiquid exists where 1ml equals 7000 micrograms.
Person smokes a pack a day for 25 years, and has moderate health issues, but nothing serious with lungs. Then vapes for 5 years at 1 ml a day.
Are we to believe there is, even in this hypothetical, a strong likelihood that this person will encounter lung issues? And that this is solely attributable to inhaling diketones?
If yes, then would it be fair to say that if smokes could get diketones out of their product, that smoking would be safer, perhaps causing zero lung issues in all users? Cause that really really really appears to be the argument that is put forth. And I had to go with hypotheticals (on the vaping side) that don't really exist, or if they do, are the exception to some fairly established rules, even by all participants in this thread.
Even in the workplace exposure examples, that are only information we have for actual harm, the likelihood of DA being deemed a causal factor is 1 in a thousand chance. Yet, some in vaping community are suggesting that having DA in eLiquid equals very strong chance that ALL vapers would be harmed (lung problems) and that would be (solely) attributable to the presence of DA.
Let's say that 1 in a thousand people that inhale nicotine have some very significant, perhaps even lethal malady that happens to them. They are only inhaling 1.2% nic at 1 ml a day. But science determines their malady is caused by them inhaling nicotine for say 3 months straight. So, even if 999 other people who inhale similar amount are not affected, shouldn't we be equally worried (along lines of DA concerns) that this is a very harmful ingredient in eLiquid and that it ought to be removed? That the whole industry could get shut down if we don't remove it? Cause clearly many vapers, who vape non-nic liquid, are establishing that this is not necessary ingredient in eLiquid. Therefore, why would anyone suggest that we need to have it in there?
Me, I hope nic is sold in eLiquid indefinitely, as an option to entire consumer base, and that DA laced liquids are an option to that same base, forever and ever. And that we realize 30 years from now (or 3 days from now, or even 300 years from now) that magically only .1% of the population seems impacted by this thing that a vocal minority was very concerned about in 2015.
ETA: That after reading Dr. F.'s post, it must be noted that removing nic from eLiquid is the right thing, because it is a compound that may cause harm. Hope we can all get aboard that train. /sarcasm
so if there is any issue you won't be alone, is that it? 
No we who understand common sense won't be taking that route and vaping being the pleasure/relief it is, it, is not a burden at all.
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