Smelting, underground mining, smoking, and lung cancer: a case-control study in a tin mine area.

An increased risk of lung cancer in the Dachang tin mine of Guangxi has been reported. To investigate the factors contributing to the excessive risk of lung cancer, we conducted a matched case-control study in the mine area and analyzed the effects of multiple factors, such as living and housing conditions, occupational exposure, and smoking, with the methods of conditional logistic regression. The case series consisted of 69 patients with primary bronchial cancer, 55 of whom had died. The control series consisted of 138 individuals, 55 of whom were decreased. The results showed that the factors contributing to the excessive risk of lung cancer in the mine area related mainly to occupational exposure. The significant risk factors were time of exposure to smelting, time of exposure to underground mining, and age at which underground mining was begun. In study model II where living controls were used, daily consumption of cigarettes was an additional risk factor. Furthermore, there was a synergistic action among these factors. The relation of the risk factors to lung cancer is discussed.