There is also pretty decent evidence that it's not that dangerous:

https://gwern.net/nicotine

-edit- that write up is almost exclusively for adults. The affects on teens and children, with developing brains etc., is much less clear and if nothing else the precautionary principle would probably say that it's a bad idea.

But for adults, I'm personally convinced that the balance of evidence is that nicotine itself is not particularly harmful when consumed in reasonable amounts.

-edit- also realized that I linked to the same article that the top level comment linked. Considering that that post includes dozens of journal articles, linking one single research article without addressing any of the contrary ones isn't particularly useful. Beware the man of one study:

https://slatestarcodex.com/2014/12/12/beware-the-man-of-one-...

If you read the article carefully it accelerate tumor growth but it's doesn't cause cancer it act synergistically with other carcinogenic:

  Through its tumor promoter effects, it acts synergistically with other carcinogens from automobile exhausts or wood burning and potentially shorten the induction period of cancers.

That difference is subtle and past a certain age that difference is meaningless.

This seems like a fairly weak review, it just presents links to other papers with a lot of “might”s. I don’t see any meta-analysis computing actual harm.

Eg “nicotine and cancer”:

> In addition, nicotine is a precursor of tobacco specific nitrosamines (TSNAs), through nitrosation in the oral cavity.[32,33] It is shown that nitrosation of nicotine could lead to formation of NNN and NNK. This effect of nicotine may be important…

As Gwern noted, the cardiovascular risks are nonzero, but it doesn’t seem like there is evidence of a strong effect for increasing cancer. (Still room for a weak effect I suppose.)

Thanks for linking this. I wish though that there were a more useful standard of summary: a list of a lot of "nicotine has a negative effect on X" and "associated with a negative on Y" that only tells you a sign, which some publication found statistically "significant". What matters for decisions is effect size and the probable range thereof. (Either sign has a prior probability of 50%, and you can expect publication bias.)

Since I'm only curious I'm not doing all the work to try to figure that out; hope someone else has that kind of review.

The evidence is fairly weak.

> Although nicotine itself does not cause cancer in humans,[40] it is unclear whether it functions as a tumor promoter as of 2012.[104] A 2018 report by the US National Academies of Sciences, Engineering, and Medicine concludes, "[w]hile it is biologically plausible that nicotine can act as a tumor promoter, the existing body of evidence indicates this is unlikely to translate into increased risk of human cancer."[105]

https://en.wikipedia.org/wiki/Nicotine#Cancer

In any case, it's crucial to distinguish between a weak tumor promoter which may have statistically minor impact on cancer rates (nicotine), and an unambiguous carcinogen that kills people by the bucketload (tobacco).

The same could be said of coffee

That is if you consume too much. Anything is poisonous in great enough quantities, including water. I'm assuming OP is asking about whether it's dangerous in normal dosages.

That's likely the vape smoke rather than the nicotine.

A studied on vapes showed that any smoke/irritant (including vapes) going through the air passageways stimulates the vagus nerve and cause a inflammation in arteries/increased heart rate/increased cardiac risks.

Nicotine delivered without smoke didnt have the same effect