Risk factors for respiratory work disability in a cohort of pulp mill workers exposed to irritant gases

Data about respiratory symptoms and disease diagnoses, socio-demographic variables, occupational exposures, gassing episodes, and reported work changes due to respiratory problems were collected using a questionnaire answered by 3226 pulp mill workers. Information about work history and departments was obtained from personnel files. Incidence and hazard ratios for respiratory work disability were calculated with 95% confidence intervals (CI).The incidence of respiratory work disability among these pulp mill workers was 1.6/1000 person-years. The hazard ratios for respiratory work disability were increased for workers reporting gassings (HR 5.3, 95% CI 2.7-10.5) and for those reporting physician-diagnosed asthma, chronic bronchitis, and chronic rhinitis, when analyzed in the same model.This cohort study of pulp mill workers found that irritant peak exposure during gassing episodes was a strong predictor of changing work due to respiratory problems, even after adjustment for asthma, chronic bronchitis, and chronic rhinitis.There is increasing scientific evidence indicating that asthma is an important predictor of work disability [1]. This evidence mainly comes from large general population-based studies such as the European Community Respiratory Health Survey (ECRHS), in which the prevalence of respiratory work disability, defined as changing or leaving work due to affected breathing, was found to range from 1.6% to 8.1% in various countries [2]. In the follow-up of the ECRHS population, the incidence of respiratory work disability was 1.2/1000 person-years in the total population and 5.7/1000 person-years among participants with asthma [3]. The corresponding cumulative prevalences were 1.1% and 4.9%, respectively. Exposure to air pollution at the workplace was an important predictor of respiratory work disability, both in the cross-sectional analysis [2] and in the longitudinal analysis [3]. In the longitudinal study, the exposure was divided into three groups; organ