They don't contain any of the substances that are harmful in analog cigarettes. They're essentially nicotine + stage smoke.

They don't have the same harmful chemicals as "analog" cigarettes, but the combustion by-products are still not something a rational person would want in their lungs.

I wouldn't argue that they're harmless but my understanding is that combustion is not involved, and that is exactly why they are presumed to be _less_ harmful than smoking.

Cigarettes kill 50% of long term users. Being safer than that is not a big accomplishment.

I agree completely. I don't mean to suggests that vaping is a good idea, only that it apparently doesn't have PICs in it.

Being safer in general isn't. Being safer while also being a psychologically acceptable substitute for smokers - this is the achievement.

This is correct. The mixture is almost always propylene glycol, vegetable glycerin, nicotine, and flavoring. I don't know of any negative effects of propylene glycol and vegetable glycerin, and as long as you don't use a carcinogenic flavoring (they exist) your biggest problem will likely be nicotine.

I don't think nicotine is good for you, but vaporized nicotine seems much less dangerous than smoking a cigarette.

Even glycol and glycerin vapor are probably not a good idea to inhale. They could hardly be as bad as smoking cigarettes, but so far basically anything you breathe in that isn't air turns out to be a bad idea once we study it thoroughly.

Whether nicotine is harmful seems to be under debate:

https://tobacco.ucsf.edu/cdc-publishes-more-evidence-nicotin...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4363846/

also a good & nuanced read: https://www.gwern.net/Nicotine

Your second link mentions LD50 in adults of around 30-60 mg of nicotine. In children the LD50 is around 10 mg.

Seems harmful enough to me.

even advil has an LD50. dosage matters

Even water has LD50.

12L/day.