[The Saucepan Man]

Some posters have questioned the fact that Tolkien's pipeweed is tobacco.
It definitely is.

Yup. In The Hobbit, Chapter 1, An Unexpected Party, Bilbo says to Gandalf:

And a very fine morning for a pipe of tobacco out of doors, into the bargain

So the Hobbits' pipeweed was definately tobacco, or as Tar-Palantir rightly points out, the leaf of the tobacco plant. And yes, it is doubtful that the Hobbits added to Longbottom Leaf and the like the kind of additives that go into most tobacco products today.

I agree that the risk of serious disease for those in Middle Earth who indulged in pipesmoking would generally be less than for the average smoker in our world due to their otherwise healthy lifestyle.

But there is also another point to consider. As I understand it, in addition to precluding death from old age, immortality also brings with it immunity from disease. I seem to recall it being said in the Silmarillion that Elves could not die of old age or disease, but could be physically slain, for example by means of a blow from a weapon (in which case they went to the Halls of Mandos).

The question is, does that immunity relate only to externally caused diseases, ie those caused by bacteria and viruses, or does it also extend to internally caused diseases, such as cancer, heart disease etc? If the latter, then Elves would be at no risk whatsoever from tobacco. However, it seems from Legolas' comments at Isengard that Elves did not indulge, which is kind of ironic if they were the only race not to be at any risk. Gandalf too, of course, would not be at risk, being a Maia and therefore immortal. Possibly Aragorn, who had Elven blood in his veins, albeit very much diluted, would have had a stronger resistance to disease, although that seems doubtful since the immunity appears to be a function of immortality rather than simply Elven ancestry.

Overall, however, I think that the combination of the purity of the tobacco, the relatively low level of indulgence and the otherwise healthy lifestyle meant that the risk for the non-immortal races was very much lower than the average smoker in our world.