Carcinogenicity of dark liquor.

To investigate whether the non-alcohol content of distilled alcoholic beverages affects the carcinogenicity of the beverage, we conducted an epidemiologic study of laryngeal and hypopharyngeal cancer. We interviewed 384 cases (or spouses, for deceased cases), and compared their responses with those of 876 controls. We classed distilled liquors as dark or light, a rough division according to content of potentially carcinogenic compounds in the beverages. The relative effect on hypopharyngeal cancer risk was much stronger for those who reported high consumption of dark liquor (relative risk = 4.4, 90% confidence interval = 2.9, 6.8) than for those reporting comparable consumption of light liquor (relative risk = 1.3, 90% CI = 0.8, 2.1). For laryngeal cancer, consumption of dark liquor had a smaller effect, and there was little distinction between the effects of dark and light liquor. The data appear consistent with the theory that the non-alcoholic content of distilled alcoholic beverages is a determinant of cancer risk, and that alcoholic beverages act topically rather than systemically in their carcinogenic action.