RESIDENTIAL RADON EXPOSURE AND LUNG-CANCER IN SWEDEN

Background. Residential radon is the principal source of exposure to i onizing radiation in most countries. To determine the implications for the risk of lung cancer, we performed a nationwide case-control study in Sweden. Methods. The study included 586 women and 774 men 35 to 74 years of age with lung cancer that was diagnosed between 1980 and 198 4. For comparison, 1380 female and 1467 male controls were studied. Ra don was measured in 8992 dwellings occupied by the study subjects at s ome time since 1947. Information on smoking habits and other risk fact ors for lung cancer was obtained from questionnaires. Results. Radon l evels followed a log-normal distribution, with geometric and arithmeti c means of 1.6 and 2.9 pCi per liter (60.5 and 106.5 Bq per cubic mete r), respectively. The risk of lung cancer increased in relation to bot h estimated cumulative and time-weighted exposure to radon. In compari son with time-weighted average radon concentrations up to 1.4 pCi per liter (50 Bq per cubic meter), the relative risk was 1.3 (95 percent c onfidence interval, 1.1 to 1.6) for average radon concentrations of 3. 8 to 10.8 pCi per liter (140 to 400 Bq per cubic meter), and it was 1. 8 (95 percent confidence interval, 1.1 to 2.9) at concentrations excee ding 10.8 pCi per liter. The estimates of risk were in the same range as those projected from data in miners. The interaction between radon exposure and smoking with regard to lung cancer exceeded additivity an d was closer to a multiplicative effect. Conclusions. Residential expo sure to radon is an important cause of lung cancer in the general popu lation. The risks appear consistent with earlier estimates based on da ta in miners.