[Mugwump]

The cancer risk from pipe smoking is much less than for cigarettes, perhaps because the smoke is generally not inhaled. In America, with a population of over 300 million, there are an estimated 1000 or so cancer deaths (all kinds, not just lung cancer) per year attributed to pipe smoking. That's about one death per 300,000 people in the population (a much smaller number smoked pipes, of course). Although it's not politically correct to say so, perhaps pipe smoking just isn't all that dangerous.

Besides which, we don't know much about hobbits' smoking habits. We don't know how often they smoked, whether or not they inhaled, or even whether their "pipe weed" was even tobacco! We also don't know whether hobbits had a greater resistance to diseases like cancer than humans have.

In fact, if we can accept the existence of Balrogs in Middle Earth, then why couldn't we accept the existence of pipe weed smoking that doesn't cause any kind of cancer? If Tolkien did not put lung cancer into his world, then why should we assume it exists there!