Interaction between underground mining and smoking in the causation of lung cancer: a study of nonuranium miners in northern Sweden.

Combined effects of underground mining (nonuranium mines) and smoking were analyzed in a case-control study of male lung cancer in northern Sweden. Lung cancer cases exposed to underground mining had a considerably lower average cumulative tobacco consumption than other lung cancer cases, indicating that smoking is especially dangerous for underground miners. When relative risks were estimated, a synergistic effect of multiplicative type was found between smoking and underground mining.