Exposure-response relations for self reported asthma and rhinitis in bakers

OBJECTIVES To explore relations between two estimates of exposure to inhalable flour dust, and the incidence rates (IRs) of asthma and rhinitis in bakers. METHODS This was a retrospective cohort study among 2923 bakers. A posted questionnaire registered the disease and work history. For every year, each baker was assigned an estimate of the exposure concentration to inhalable flour dust derived from reported job-tasks and dust measurements. Exposure at onset of disease was expressed as current dust exposure concentration, and as cumulative dose of exposure to dust. A multiple Poisson regression analysis assessed the impacts of the exposure estimates on the IRs of asthma and rhinitis. RESULTS IRs of asthma and rhinitis increased by dust concentration at onset of disease. The IR of asthma for the bakers with highest exposure (dough makers) was 7.3/1000 person-years in men and 6.5 in women and for rhinitis 43.4 and 38.5, respectively. There was a significant association between the dust concentration at onset of disease and the risk for asthma or rhinitis, but not of the cumulative exposure. CONCLUSION The risk of asthma seemed to be increased at inhalable dust concentrations ⩾3 mg/m3 (dough making or bread forming), whereas the risk of rhinitis was increased at all concentrations ⩾1 mg/m3, indicating an increased risk in all bakery job-tasks. The risks seemed to be less dependent on the cumulative exposure dust than the inhalable dust concentrations.