[jjsheridan5]

They are not saying that nicotine causes lung cancer but that it will speed it up if it occurs.

This, IIRC, is a somewhat controversial study. First, it was in vitro, and, often, what happens in a petri dish, stays in a petri dish, so to speak. Second, apparently they used extremely large amounts of nicotine (far more than any cell would ever see, in practice). Third, there has never been any actual study that shows that this occurs in practice (even though nicotine is probably the most studied chemical on earth). Finally, it is a scare headline only -- how many otherwise healthy chemicals (or even vitamins) would, in an in vitro study, speed up cancer?

[TigersEye]

This, IIRC, is a somewhat controversial study.

That may be true. It indicates that there is a possibility though.

Finally, it is a scare headline only -- how many otherwise healthy chemicals (or even vitamins) would, in an in vitro study, speed up cancer?

I don't know but if they aren't in cigarette smoke it would be a non-sequitur to this subject.