Figure 5.9

Relative risks (RR) from eight lung cancer case-control studies of indoor radon levels. Dashed line is extrapolation of risk from miners for a 25 y exposure. Dotted line is a relative risk of 1 (Lubin and Boice 1997).

Two followup studies of the cancer risk in organs other than the lung were performed. One cohort was uranium miners in West Bohemia, and the other was iron miners in Sweden. In the West Bohemia study of 4,320 uranium miners, 28 sites of cancer mortality were evaluated. No statistically significant cancers other than lung cancer occurred. The authors state that the possible exception is cancer of the gallbladder/extrahepaticducts, with 12 deaths (ratio of observed to expected (O/E), 2.26; and confidence interval (CI), 1.16–3.94), but they state that such cancers would have to be studied further to prove that radon was causal (Tomasek and others 1993).

In the Swedish study, the mortality of 1,415 iron miners was studied, and 27 sites of cancer were evaluated Darby (1995). There were no statistically significant increases in gallbladder or extrahepatic duct cancers, but a marginal excess of stomach cancers was found (O/E=1.45; CI=1.04–1.98). The authors state that the stomach cancer was probably due to the considerable number of Finns in the workforce; stomach cancer in males, especially in northern Finland, is considerably higher than in Sweden, the population used for reference.