You want to classify sugar as harmful? It's physiologically addictive (go a few days without carbs altogether and tell us how it goes).
What about caffeine?
Caffeine is also addictive and if you drink enough, stopping gives you withdrawal headaches. But in my experience not drinking caffeine at all makes me just as alert as getting used to the daily dose I thought I needed before.
So yeah, I'd totally classify both as slightly harmful.
But some harmful things are worth the tradeoff if you can maintain a low enough dose (sugar or caffeine)
Vaping might have social and physiological benefits which outweigh the harm also.
Even the physical addictiveness of nicotine is not that strong when separated from the rituals of smoking compared to e.g. caffeine (where addiction is also massively affected by rituals).
https://en.m.wikipedia.org/wiki/Nicotine
> Nicotine is classified as a poison. However, at doses used by consumers, it presents little if any hazard to the user.
I would be surprised to see that inhaling any kind of smoke or non-water aerosol is good for your lungs, so I'd expect at least a minor harmful effect.
This study, for example, claims increased risks for heart disease [1] (disclaimer: I'm not a medical doctor and cannot evaluate its credibility)
[1] https://link.springer.com/article/10.1007/s40138-020-00219-0
However, by comparison, tobacco smoke is like "what if we could engineer the perfect lung assailant."
Tar causes inflammation, damages DNA directly, intercalates DNA and induces replication errors, collapses alveoli, and paralyzes cillia, making clearance of all those chemical assailants from the lungs even harder.
