Mortality in Underground Miners in a Former Uranium Ore Mine–Results of a Cohort Study Among Former Employees of Wismut AG in Saxony and Thuringia

Abstract

Background: From 1946 to 1990, more than 400 000 people were employed by Wismut AG, a Soviet/Soviet-German corporation (German abbreviation: SAG/ SDAG), in the East German states of Saxony and Thuringia. In the early years in particular, employees were exposed to large amounts of radon and respirable crystalline silica.

Methods: In a cohort of 35 204 former underground employees of Wismut AG, mortality was analyzed in comparison to the general male population of East Germany, and the pertaining standardized mortality ratios (SMRs) were calculated.

Results: 18 510 persons in the study cohort died in the follow-up period 1960-2013. Mortality from lung cancer was 2.36 higher in the study cohort than in the general population (95% confidence interval, [2.28; 2.45]); the associated SMRs rose markedly with increasing radon exposure. Mortality from silicosis and other types of pneumoconiosis was elevated by a factor of 22.62 [21.20; 24.11], and the associated SMRs rose exponentially with increasing exposure to respirable crystalline silica. Mortality from both of these causes was still markedly elevated more than 20 years after Wismut AG had ceased its activities. Mortality from a wide range of other diseases was elevated as well, with the following SMRs: stomach cancer, 1.28 [1.17; 1.40]; liver cancer, 1.34 [1.15; 1.55]; all tumors other than lung cancer, 1.06 [1.02; 1.09]; infections, 1.18 [1.01; 1.38]; cerebrovascular diseases, 1.33 [1.26; 1.41]; and influenza/pneumonia, 1.13 [1.01; 1.27]. Mortality from a small number of other causes was found to be markedly lowered in the study cohort (mental illness, renal diseases, and nervous system diseases). The role of occupational risk factors, lifestyle differences and other reasons for the latter results is unclear.

Conclusion: Underground miners employed by Wismut AG displayed marked excess mortality due to silicosis/other pneumoconiosis and lung cancer. The contribution of individual occupational risk factors for these and other causes of death with increased SMR are being further investigated in analyses within the study cohort.

eFigure

Timeline of the mean annual cumulative silica dust exposure in mg/m3-years and of the mean cumulative radon exposure in working level months (WLM) for the underground cohort of Wismut employees