For purposes of this discussion we're talking vaping flavored nicotine. Ultimately, it's in the industry's interest to provide an addictive liquid that has very little to no carcinogenic compounds. They want you addicted but don't want liability.

BUT they COULD include them if they wanted and that's one issue.

So saying Vaping is safe is a bit like saying a non-specific car is safe (when in reality a tank/SUV is going to be a lot safer than some tiny car).

And ultimately I think the safest position is to explicitly state what liquid one is talking about and state "it has not yet been proven safe for longtime consumption and proceed with caution." I think for many it could also be stated that they haven't been proven to be unsafe yet.