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Environmental tobacco smoke and lung cancer incidence.

Tobacco smoking has been irrefutably linked to lung cancer risk. Exposure to environmental tobacco smoke and lung cancer risk has been more controversial. Various sources have claimed confounding factors such as diet and classification bias could account for the reported link. We review the available evidence and some recent papers on this topic and conclude that the evidence linking environmental tobacco smoke and lung cancer is unequivocal and cannot be explained by confounding factors.