Epidemiological studies of Czech miners

Lung cancer risk from radon was analysed in three cohorts of uranium (N=4320+5628) and burnt clay (N=915) miners. The follow-up of miners was extended up to 1990. Most of the cases (708) have been observed in the oldest (S) cohort followed since 1952. The other two cohorts, 18 years younger in average with substantially lower exposures, contributed 72 cases. Therefore, the main analyses of risk from radon were based on the S cohort. The data of the S cohort were subjected to checks both as for the individual exposures of the miners and the completeness of follow-up. The present mortality analyses from other causes suggest the follow-up is correct. The general patterns of mortality from violent deaths and diseases other than lung cancer show similar features in all the three cohorts, i.e. decreasing trend with time since first exposure in the first case, and increasing trend in the second one, confirming thus the healthy worker effect, in the first 20 years. A raised mortality was observed in later periods in respiratory and circulatory diseases and also in cancers other than lung cancer, suggesting that smoking habits among miners might be more frequent than in the general population. The estimates of lung cancer risk from radon exposure were based on relative linear models, where cumulative exposures were lagged by 5 years. The linear effect of cumulative exposure was substantially modified by time since exposure, exposure rate, and age at exposure. From the estimated intercept, it can be deduced that in the absence of exposure to radon, the estimated mortality from lung cancer in the cohort is about 1.5 times higher than in the general population. (orig.)