Silica dust, radon and death from non-malignant respiratory diseases in German uranium miners

Objective To quantify the relationship between death from non-malignant respiratory diseases (NMRD) and exposure to silica dust or radon in a cohort of 58690 former German uranium miners. Methods In the follow-up period from 1946 to 2008, a total of 2336 underlying deaths from NMRDs occurred, including 715 deaths from chronic obstructive pulmonary diseases (COPD) and 975 deaths from silicosis or other pneumoconiosis. Exposure to respirable crystalline silica and radon was individually assessed by means of a comprehensive job-exposure matrix. Risk analyses were based on a linear Poisson regression model with the baseline stratified by age, calendar year and duration of employment. Results There was no increase in risk of death from COPDs or any other NMRDs in relation to cumulative exposure to silica (mean=5.9, max=56mg/m(3)-years), except in the group of deaths from silicosis or other pneumoconiosis. Here, a strong non-linear increase in risk was observed. Cumulative radon exposure (mean=280; max=3224 Working Level Months) was not related to death from COPDs or any other NMRDs. Conclusions The present findings do not indicate a relationship between mortality from COPD with silica dust or radon. However, validity of cause of death and lack of control for smoking remain potential sources of bias.