Combined effects of mining and smoking in the causation of lung carcinoma. A case-control study in northern Sweden.

Within a case-control study of male lung carcinoma in northern Sweden combined effects of underground mining (iron ore mines) and smoking were analysed. A synergistic effect was found approximately of multiplicative type. Cases with lung carcinoma exposed to underground mining had a considerably lower average cumulative tobacco consumption than other lung carcinoma cases as an expression of the fact that smoking is particularly dangerous in underground miners. Small cell undifferentiated carcinoma was overrepresented among the cases exposed to underground mining and were especially often low tobacco consumers. In the 2 municipalities where the iron mines were located 74 per cent of the male lung carcinoma incidence could be explained by smoking and 55 per cent by underground mining (etiologic fractions).