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That a lung cancer occurs at some rate such that a particular study could only detect it when smoking five cigars a day doesn't actually tell you anything about your individual risk without knowing the population size of the study. Well, it tells you that there's probably some causative connection between smoking and cancer, but it definitely doesn't give you a "safe" threshold beneath which you can smoke without risk.

Also, shouldn't you be more concerned about oral cancers and cardiovascular disease? I understand most people don't inhale cigar smoke into their lungs like they do cigarette smoke, so you would certainly expect the lung cancer risk increases to be relatively lower.