Objectives The present study sought to examine the long-term effects of exposure to respirable dust, in particular of respirable quartz on pulmonary function.
Method The study is based on the Wismut cohort of former uranium miners. Spirometric data, including forced expiratory volume in 1s (FEV1) and forced vital capacity (FVC) were ascertained together with quantitative estimates of cumulative exposure to respirable dust and respirable quartz for each of the 1421 study subjects born between 1954 and 1956. Linear mixed regression models were fitted to identify significant determinants of longitudinal changes in lung function parameters. Point estimators and confidence intervals for the exposure concentration threshold value were fitted by partial likelihood profiles of the corresponding models.
Results Overall, 7122 data records were included in the analysis - on average five spirometries for each miner. The mean annual exposure concentration to respirable quartz was 0.072 mg/m³. It was shown that cumulative exposure to 1 mg/m³-year respirable quartz leads, on average, to a relative reduction in FEV1 of 2.07% and in the quotient of FEV1/FVC of 2.75% (p < 0.001). The analysis of the whole respirable dust shows, that the fraction of quartz in the dust is the decisive determinant for the impact of dust. A significant improvement of model fit by applying threshold models could not be observed.
Conclusions This study adds further evidence on the long-term effects of exposure to respirable quartz. Current exposure limits for respirable quartz require a critical review.
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