As far as I'm aware this hasn't seen the inside of a courtroom yet (if I'm wrong no doubt someone will pipe up, no pun intended).
I don't know, is the honest answer. I would have thought, using common sense alone, that if you spend a large portion of your life cooped up in a metal tube breathing fairly recycled air which happens to be full of carcenogenic contaminants you're more likely to suffer a related disease than if you don't, all other nasties in everyday air notwithstanding.
We all breathe in stuff that does us no good, but the problem that airlines face in any potential litigation is that it all sounds far too plausible; smoke in a cabin is all too obvious and pervasive. Never mind that the very same frequent flyer probably also goes to a pub in London two or three times a week, for much the same time as he'd spend in flight, and inhales just as much. You can walk out of a pub - it's a bit harder to do that at 30,000ft, and that fact together with the fact that most people still regard flying as the work of the devil, means that I think you'd have a fair chance in court, particularly in America.
Incidentally, am I correct in remembering Iberia as having a particularly novel approach to separating smokers from non-smokers? Smokers on the left hand side of aisle, non-smokers down the right.....?