[marktwain]

However, are we to believe that by some mysterious filtering process, smoke is purified of carcinogens in the lungs of a smoker, such that the smoker exhales only safe smoke?

No "mysterious filtering process" is required. It is obvious that some filtering takes place, perhaps quite a bit, or there would be no effect on smokers. It is also clear that people breathing "second hand smoke" are subjected to far lower concentrations of smoke {and presumably carcinogens) simply because the primary source of the smoke is directed directly to the smokers lungs, not to other people.

If you just consider the amount of air that "second hand smoke" is mixed with in comparison with the direct exposure to the smokers lungs, it is obvious that the effects on non smokers must be much, much lower than on smokers. Add to this the limited effects of smoke on smokers, and it is easy to see why no significant effects of second hand smoke on mortality have been found in serious studies on the subject, dispite the numerous junk science efforts to imply that they exist.

[Old Professer]

Why would you try to use logic on "a man of reason?"

[Lee'sGhost]

"It is also clear that people breathing "second hand smoke" are subjected to far lower concentrations of smoke {and presumably carcinogens) simply because the primary source of the smoke is directed directly to the smokers lungs, not to other people."

So, like, what's filtering the smoke that comes out of the lit end of the cigarette that's spends half its time in someone's hand or in the ashtray?