Do we know anything is safe to vape? Personally, I'm not worried about it considering how many years I smoked. I had a long read about how molecules in different types of plastic breakdown and since my lungs aren't made of plastic, I'm not concerned.
What is produced during, or as a result of, the breakdown does concern me, which I why I use primarily glass and will stop using a device that appears to be reacting - however slightly. I think in terms of vinegar and bleach. Both are fine by themselves, but when mixed together there is a problem.