Respiratory symptoms and asthma among workers exposed to paper dust: a cohort study.

The aim of the present cohort study was to investigate whether exposure to paper dust causes increased risk for respiratory symptoms or asthma. The cohort included all workers at a soft paper mill who had worked there for more than 1 year 1960-1986 (n = 1,697). Randomly selected inhabitants of the mill town (n = 781) were used as unexposed referents. Both groups were investigated using a postal questionnaire. From the paper mill cohort, workers with high cumulative exposure (n = 313), with medium cumulative exposure (n = 321), and with low cumulative exposure (n = 338) to paper dust were selected. In the 1960s and 1970s, the dust levels were between 5 and 10 mg/m3. After adjustment for smoking and gender, paper dust exposure resulted in elevated prevalence ratios for chronic cough, chronic phlegm, wheeze, and breathlessness. The prevalence ratios ranged from 1.3 to 2.5. No significantly increased risk of asthma was found among the exposed, incidence rate ratio 1.4 (95% confidence interval 0.93-1.8). Among the exposed, there was an insignificantly increasing incidence rate ratio, 1.0, 1.4, 2.1, with increasing cumulative exposure. In conclusion, an increased risk for respiratory symptoms was observed among workers exposed to paper dust, but the study does not permit any definite conclusions regarding asthma and paper dust exposure.