Observations on cancer etiology in China.

Major variations in cancer by site and sex are being discovered in the People's Republic of China. Nasopharyngeal carcinoma, the most common form in Kwangtung Province, accounted for 43.0% of biopsied cancers in males. Liver cancer is predominant along the coast near Shanghai and appears to be a major cause of mortality in many other parts of the country. The mortality rate of esophageal cancer, the primary cause of all mortality along the eastern slopes of the Taihang Mountains in North China, varies by 100-fold in areas short distances apart; this geographical variation is paralleled by a carcinoma of the gullet in domestic chickens. Several foods, particularly a type of pickled vegetable, contain high concentrations of nitrosamines and nitrites, which are thought to be etiologically important.