It's pretty impossible to find something that is less safe than cigarettes. I guess if you hook a tube up to an exhaust pipe of a diesel engine, that is probably less safe.
The only less safe thing for an e-cig compared to a cigarette is that if you don't have a vent hole on your battery cap. If the battery vents, it can very well explode in your hand and face. I've only seen one mechanical mod that didn't have a vent hole for the battery cap though.
Assuming that the wording of your question is a little off, VG&PG.. vegetable glycerin and propylene glycol are used in numerous pharmaceutical and/or food applications. Both of these compounds are used with inhalers of different sorts. I wouldn't say it is entirely healthy, but both can be beneficial to your lungs if you're not allergic to the compounds. I'm not going to get into a debate about flavors..those will range in effect based on their make-up.
I will tell you that you're more likely inhaling safer air vaping than you would driving down the road..definitely if you're on a congested highway.
Oxygen is poisonous when extremely concentrated and also causes cells to die, but we need it for APT production.
sorry to say but as a diesel techh for many years i can aruge that a cig is more then likly worse then diesel exhaust. with the advent of dpf/doc/scr combo exhaust they burn very clean. also they nolonger clatter and produce loud noise