Pure nicotine seems to be harmless except in overdose, the main side effect being a compulsive need to consume more nicotine. Whether the delivery mechanism in vaping, year after year, is harmless, is a different question. Anecdotally, I used a nicotine vape to quit smoking -- and they're wonderful for that -- but when I quit that as well, my chest went through a phase where it cleared out all manner of gunk not unlike when I quit smoking cigarettes.
It's hard to separate the impacts of plain nicotine from the impact of cigarettes because the literature is almost entirely focused on smokers, and scientific writing sometimes conflates the two. That said,
> Nicotine constricts blood vessels, including those in the skin and coronary blood vessels, but dilates blood vessels in skeletal muscle. Vasoconstriction of the skin results in reduced skin blood flow and reduced fingertip skin temperature.
Vessel constriction or dilation by itself is not necessarily a bad thing. CO2 is a potent vasodilator, but no one would claim holding/pacing your breath for swimming is a bad thing. Caffeine too has a strong vasoconstricting effect.
Cardiovascular effects of nicotine are probably more dangerous than potential carcinogenic nature of smoking.
edit: smoking is carcinogenic, but how much of it is because of nicotine I wouldn't know; a smoker might not live long enough to find out at what age the cancer develops if he drops dead because of the heart infarct.
I cannot imagine sincerely believing a statement that is so blatantly wrong. Moreover, there’s nothing ‘potentially’ carcinogenic about smoking, it is a known carcinogen.
