BS”D
-depth of inhalation-
That looks like a skewed study that somehow found rednecks in the Appalachians who inhale pipe smoke. And that does not surprise me because the number of proper pipe smokers is so low.
The real risk with pipe smoking is oral malignancy. It is a real risk for constant pipe smokers but it really is hard to smoke more than one or 2 big pipefuls a day.