I spoke with my GP and my Endocrinologist and both gave me the same answer. (BTW my Endo is on the board currently doing a 2 year study on the effects of
vaping within Texas)
While it is better than smoking by far, you are still inhaling something that is not supposed to be in the lungs.
After saying that, my Endo said that in so far all reports to the board that he sits on there have been no cases that he has seen to suggest that
vaping has done significant harm to an individual except for one case, but this person was soon excluded from the report as he was found to have an allergy to VG.
He also did mention that there is a lab test ongoing where a series of mice are being kept in a "fog" of mixtures (different mice being given a different mixture between 100% VG to 50/50 VG/PG to 90% PG) and other than some effects that are to be expected due to the 100% humidity 100% of the time there are still no signs of long term damages. This is the same type of experiment that caused some artificial sweeteners to be pulled from shelves (come on, a diet of nothing but 100% artificial sweeteners is going to kill anyone).
When I see him again in 6 months I will ask for an update.