How does that line up with the fact that chewing tobacco is still associated with oral cancer?

Most preparations of chewing tobacco are smoke or fire cured. The process still introduces many of the byproducts that are created during the combustion of dried organic material.

The most prominent example of chewing tobacco that isn't smoke cured would be Scandinavian-style snus. There's pretty compelling evidence that snus is not associated with oral cancer[1], or at the very least the risk is substantially lower than traditional chewing tobacco.

[1] https://onlinelibrary.wiley.com/doi/full/10.1046/j.1360-0443...

There are a few meta-analysis about snus cancer risk. I think generally the opinion [1] is that while lower than other smoke-cured tobaccos, there still exists a non-zero risk for oropharyngeal cancer risk and statistically-valid increase in pancreatic and esophageal cancer risk compared to non-tobacco users. [1](https://www.thelancet.com/journals/lanonc/article/PIIS1470-2...)

Unless nicotine gum has a similar association, it's probably the same generic cause.

That may be carcinogenic in another way. It's my impression that nasally ingested dry snuff tobacco is not as strongly associated with cancer as smoked or chewed tobacco. That said, it's hard for me to trust anything I read suggesting that, since I can't rule out the possibility that the tobacco industry has corrupted anything I might read suggesting it.

https://en.wikipedia.org/wiki/Snuff_(tobacco)#Health

I agree with your second point, however, respectfully, your first point is incorrect (I was going to call it absolute bloody bullshit, but that would be the amphetamines talking).

Here's a better breakdown of carcinogens in cigarette smoke (same book, same author)[0]. The most lethal way tobacco smoking impacts health is through carcinogenic by-products created from metabolizing said tobacco.

"PAH, N-nitrosamines, aromatic amines, 1,3-butadiene, benzene, aldehydes, and ethylene oxide are probably the most important carcinogens because of their carcinogenic potency and levels in cigarette smoke."[0]

To elucidate on one of your points: nicotine isn't on any of the "carcinogens in tobacco" lists, because it, nor any of its metabolites, aren't carcinogens at any dosage that is practically applicable to humans.[1]

[0] https://www.ncbi.nlm.nih.gov/books/NBK53010/ [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4553893/

> The most lethal way tobacco smoking impacts health is through carcinogenic by-products created from metabolizing said tobacco.

Maybe, we're misunderstanding each other. But all those compounds you listed are directly present in smoke itself. I.e. they're not metabolic byproducts.

In fact they're not even related to tobacco specifically. (With the major exception of N-nitrosamine). Cannabis smoke (gram for gram) contains equivalent of higher levels of PAH, benzene, 1,3-butadiene, aldehyde, and aromatic amines.[1] These are all pretty much universal byproducts of burning any type of dried plant material, and the same reason that exposures are similar for wood-burning fireplaces.[2]

[1] https://pubs.acs.org/doi/full/10.1021/tx700275p [2] https://www.epa.gov/burnwise/wood-smoke-and-your-health

You do not actually disagree with dcolkitt.

Right, but there are going to be other compounds released from this heatedtobacco product, most likely. Maybe not combustion products, but more than in (say) vaping.