Introduction and Objective Former German uranium miners had been exposed underground in the early years to high levels of radon and silica dust. The objective of these analyses is to compare mortality in the Wismut cohort with that of the male general population.

Methods A sub-cohort of 35,204 miners who worked at least 180 days between 1946 and 1989 underground, but never in processing or open pit mining was defined with observation period from 1960 to 2013. The underlying cause of death was available for 96.1% of the 18,510 deceased. For numerous causes of death, observed deaths (O) were compared with expected deaths (E) based on external mortality rates for the general male population by standardized mortality ratios (SMR=O/E). Exposure to radon progeny and silica was retrospectively estimated by job-exposure matrices. SMR trends for different exposure levels were examined by the Poisson trend statistic.

Results A significant excess of lung cancer deaths was found (O=2,960; SMR=2.36; 95% CI: 2.28–2.45). Of the 27 considered cancer sites other than lung, SMR was statistically significantly increased for liver (O=175; SMR=1.34; 95% CI: 1.15–1.55) and stomach (O=504; SMR=1.28; 95% CI: 1.17–1.40) cancers. A significant excess mortality from non-malignant respiratory diseases was found (O=1,928; SMR=1.86; 95% CI: 1.78–1.94), mainly related to mortality from silicosis/other pneumoconiosis (O=941; SMR=22.62; 95% CI: 21.20–24.11) and influenza/pneumonia (O=294; SMR=1.13; 95% CI: 1.01–1.27). Additionally, significant mortality excesses occurred for infectious diseases (O=157; SMR=1.18; 95% CI: 1.01–1.38) and cerebrovascular diseases (O=1,335; SMR=1.33; 95% CI: 1.26–1.41). SMRs for lung and liver cancer significantly increased with cumulative radon exposure; SMRs for silicosis/other pneumoconiosis significantly increased with silica exposure.

Conclusion Underground miners of this cohort showed a clear excess mortality for lung cancer and silicosis/other pneumoconiosis even for those later hired with lower exposures. Further research is ongoing to investigate exposure-response-relationships via internal analyses in more detail.