[William Cloud Hicklin]

In the 1940s the link between smoking and lung cancer was little understood, and even what the medical research community may have suspected wasn't widely known outside. Tolkien's own doctor and fellow-Inkling 'Humphrey' Havard was himself a heavy smoker.

Remember also that Hobbits (and Tolkien) smoked pipes, which ordinarily do not involve inhaling and in fact pipe-smoking is not generally linked to lung cancer....just cancer of the mouth and lips. In any event, Tolkien himself for all his tobacco use lived to a ripe old age and ultimately died of a stomach ulcer. Cigarette smoking creates a very elevated risk of lung cancer, but it is not by any means automatic or guaranteed that a smoker will develop it!