The way I see the risks of
vaping can be summed up thusly:
Risk level 0: not breathing.
Risk level 1: breathing clean air
...
Risk level 5: breathing slightly polluted city air
Risk level 6:
vaping glycerin
Risk level 7: Vaping glycerin and nic
Risk level 8: Vaping glycerin, PG and nic
...
Risk level 12: Vaping glycerin, PG, nic and whatever chemicals happen to be present in flavoring
...
Risk level 20: light smoking (1 or 2 per day)
...
Risk level 30: medium smoking (5-10 per day)
...
Risk level 40: Living in Beijing
...
Risk level 50: Heavy smoking (1 pack or more per day)
I accept risk level 12, mostly because I come from 50. If I ever feel some odd effect due to an ingredient I can identify (such as PG for me), I'll take it out of the equation. I know that if worse comes to worst, I can fall back on unflavored VG and nic for minimal risk vaping that'll keep me off cigarettes. But I'm pretty sure I can't eliminate nic without going right back to cigarettes.