My youngest daughter's man vapes....
He has a big, fancy "rig" and breathes some of the most wonderful aromas!
I, personally, (a smoker) think that anything breathed into the lungs has potential to do some form of harm.
I haven't delved much into the actual ingredients that are used or how the body reacts to those ingredients over long and continuous use....so I just stick with my nasty cigarettes. Lol!
I do know that there car sure smells good after he has vaped inside! Lol!

There have been reports of teens using these devices to smoke pot...which was what I thought the rigs were first designed for!