Underground mining, smoking, and lung cancer: a case-control study in the iron ore municipalities in northern Sweden.

A case-control study of lung cancer in males was performed in two municipalities in northern Sweden with large iron ore mines. Previous studies had revealed an increased lung cancer risk for underground workers in these mines, with all probability related to radon daughter exposure. Data concerning underground mining and smoking were obtained from questionnaires. All analyses suggested an interaction of a multiplicative type between underground mining and smoking in the causation of lung cancer in this population. The calculated population etiologic fraction was about 45% for underground mining and about 80% for smoking.