ENVIRONMENTAL AND DIETARY RISK-FACTORS FOR NASOPHARYNGEAL CARCINOMA -A CASE-CONTROL STUDY IN ZANGWU COUNTY, GUANGXI, CHINA

A case-control study was conducted on 88 incident cases of histologica lly confirmed undifferentiated nasopharyngeal carcinoma (NPC) in Zangw u County, China, and 176 age- sex- and neighbourhood-matched controls. The design of this study was defined after an anthropological survey on living habits in regions of high NPC incidence and the evidence of carcinogenic substances in some commonly consumed preserved foods. Sub jects were interviewed regarding living conditions and diet in the yea r preceding the diagnosis of NPC and, with the help of their families, during childhood and weaning. After adjustment for a living condition s score to eliminate a confounding effect, an increased risk associate d with consumption of salted fish during weaning and childhood was con firmed, especially for salted fish in rice porridge. The consumption o f leafy vegetables was associated with a reduced risk for NPC, and con sumption of melon seeds between 2 and 10 years of age with an increase d risk. After multivariate analysis and adjustment according to the li ving conditions score, the consumption of salted fish in rice porridge before age 2 (OR = 3.8, P = 0.005), exposure to domestic woodfire (OR = 5.4, P = 0.01) and consumption of herbal tea (OR = 4.2, P = 0.02) w ere found to be independently related to the risk of NPC. The excess r isk associated with the use of domestic wood fire increased if there w ere no windows in the house and with poor ventilation and cooking outs ide the house in a shack. As well as confirming the importance of the consumption of salted fish in childhood, this. study has been the firs t to provide unequivocal evidence for two other factors implicated in increasing the risk of NPC in China, the adult consumption of traditio nal medicines (herbal tea) and exposure to domestic wood fumes.