Almost any "heavy" mineral oil product has been found to be carcinogenic, although the proofs for refined light oils aren't too persuasive unless there are common additives present. The heavier stuff, like greases and tars, quite probably should not be applied to body parts repeatedly or left for long periods. The greatest danger is, of course, for "habitual exposures" repeated over long periods of time.

The warnings are quite similar to the reports that "any animal product (meat) blackened by fire is carcinogenic," which suggests that the "health-food-niks" who still barbecue in the backyard in common ways are probably missing something in the instruction manual.

There is less information on the "pine tars" or other vegetable renderings or distillates. Pine tar has been used, as noted, in veterinary concoctions for a very long time, and there have been few claims of cancers caused by or related to them. That might be partly because horses don't live long enough for many cancers to advance enough to be recognized for what they are. The common use of the "hoss liniment out in the barn" for human ailments/injuries suggests reasonable safety, but there's been little publicity on any studies that may have been done, at least as far as I've noticed.

John