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.