It is axiomatic that cigarette smoke is carcinogenic for oral, pharyngeal, laryngeal, esophageal, bronchial, and urinary epithelia. Convincing evidence implicates smoking as one cause of uterine-cervical cancer. Mutagens have been found in the cervical mucus of smokers. Carcinogenicity has been confirmed not only for the voluntary smoker (who later becomes the cigarette addict), but also for the involuntary inhaler of environmental smoke. Legislative efforts to restrict smoking areas abound, but the real deterrent, particularly to children, of much heavier taxation languishes. Repopularization of snuff as "smokeless" tobacco has already been associated with fatal oral cancers with short latency even among the young.
The role of oncogenes in the pathogenesis of tumors has become more clear. N-nitroso-N-methylurea is a powerful carcinogen known to cause mammary carcinoma in rats after a single dose. Activated Ha-ras-1 oncogenes are consistently found in these tumors, in which a guanine molecule in codon 12 of the