Well, what I'm getting from more googling, and reading the blogs that Kristin linked (though I haven't finished yet - some of them are very good, so thanks for that), is that:
* Nicotine or its metabolites are basically proven to cause cancerous mutations in vitro. There isn't that much research on it, but what exists seems pretty conclusive.
* That's in scientifically interesting doses only, and might not be true at all in clinically relevant doses.
* In clinically relevant doses, there's more evidence that nicotine may 'promote' some tumours.
* The epidemiology linking NRT / snus and cancer is thin, and usually biased. If there is a link, it's a very small one - and it may well be that even that dissolves into confounding variables (like sneaking a ciggie, or being an ex-smoker, or still living with or being friends with smokers...) given time and more study.
My tentative practical conclusions are basically the same as what I started with, viz.:
* NRT and e-cigarettes aren't necessarily safe, but they're so overwhelmingly safer than cigarettes that there's not really much point directly comparing them
* At the individual level, they might be sufficiently safe to effectively say "they're harmless".
* At the population level, they might cause detectable harm, more study is needed.
* Nicotine or its metabolites are basically proven to cause cancerous mutations in vitro. There isn't that much research on it, but what exists seems pretty conclusive.
* That's in scientifically interesting doses only, and might not be true at all in clinically relevant doses.
* In clinically relevant doses, there's more evidence that nicotine may 'promote' some tumours.
* The epidemiology linking NRT / snus and cancer is thin, and usually biased. If there is a link, it's a very small one - and it may well be that even that dissolves into confounding variables (like sneaking a ciggie, or being an ex-smoker, or still living with or being friends with smokers...) given time and more study.
My tentative practical conclusions are basically the same as what I started with, viz.:
* NRT and e-cigarettes aren't necessarily safe, but they're so overwhelmingly safer than cigarettes that there's not really much point directly comparing them
* At the individual level, they might be sufficiently safe to effectively say "they're harmless".
* At the population level, they might cause detectable harm, more study is needed.
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