They might be, or might not. It never fails to amaze me that a pill is hyper regulated, food is somewhat regulated, and at least where I live vape juice is completely unregulated for a couple more years. Whats in there, THC, benzene, used engine oil, who knows.
Obviously its trivial to make a substance that when vaporized is harmless; consider pure distilled filtered water. Its a hair trickier to supply nicotine with the vapor. But when they go all ochem crazy with flavors and smells, who knows whats in there and how long the users will live.
The FDA is moving extremely slowly on regulating vape juice. In a couple years it'll at least be licensed and documented. Until recently it was complete wild west.
I've never seen the FDA move on anything so slowly. There must be a lot of political money involved.