It has been well known since the 1964 Surgeon Generals Report on Smoking
That other forms of
tobacco use other than cigarettes have significantly lower
risks than inhaling cigarette smoke. We seem to forget that the 1964 report
(accurate or truthful or not) was a condemnation of cigarettes not all forms
of tobacco. Nicotine was thought by itself not to be a issue of significant harm.
Statistically one can show in certain demographic groups a higher rate of
oral cancers in those that use smokeless tobacco. It is interesting to note
that these same demographic groups a more statistically likely to have
poor oral hygiene.(think rural southern states) One can talk about nicotine
absorption all one wants. The fact of the mater is for those with limited
or no access to adequate dental care (that was the way it was for the most
part of the last century and still is in some parts) using chewing tobacco
(which was the primary form of use until recent times,might still be)
was a form of self medication because of the antiseptic qualities in
treating the pain of bad teeth and gums. Conveniently tobacco was something
readily available or grown by themselves. I think confusion arises when
people confuse snus and snuff.
Snus - Wikipedia, the free encyclopedia

Regards
Mike