Re: This is all about carcinogen levels
(I was a long term smoker of 'strong' cigarettes and am now nine months into a 'vaping only' regime and have got down to 1mg strength liquid from an original 24mg strength.)
The e-cig vaping liquid is in fact a mixture of propylene glycol and glycerin, in various ratios depending on the 'feel' preferred by the user. It also, of course, contains a small amount of nicotine.
It's been accepted for a long time that nicotine, as ingested by smokers or in any other therapeutic dose, is not carcinogenic.
I'm surprised that you say that snus use does not lead to an increase in cancer. I'm sure that I've read that snus use is associated with cancers of the soft tissue of the mouth. Also, I believe there is a difference between the 'mini-teabag of tobacco' and 'snus', where snus is in the form of a paste that is rubbed onto the inner cheek or gums. I may have got those two totally mixed up since I've never had any interest in either of them. However, I'm prepared to believe they have equivalent risk if you consider how they work.
Propylene glycol and glycerin are indeed permitted food additives but they have not been 'officially approved' for vaporisation and inhaling. You can't say that because they are safe for one then they are safe for the other. However, I'm prepared to believe that they are nowhere near as dangerous, for inhaling, as tobacco smoke.
I have extensive experience of both inhaling tobacco smoke and inhaling e-cig vapour and I can tell you that after nine months of heavy vaping, I feel a heck of a lot better and don't get out of breath easily nowadays. Actually, I ought to stop now since it's become just a behavioural and psychological habit that doesn't provide me with any definite sense of physical relief. (When I was using 24mg liquid, I really needed it. Now, I can go all day without if I forget my kit when I leave home.)