Purpose. This study aimed to examine the effect of chronic exposure to flour dust on the pulmonary symptoms and pulmonary indices of mill workers. Methods. The cohort study was conducted on 67 mill workers and 53 controls from 2014 to 2016. Demographic information was collected through interviews and pulmonary indices; flour dust exposure was measured by spirometry, and NIOSH 0500 and NIOSH 0600 methods. Results. The incidences of pulmonary symptoms, including cough, sputum, dyspnea, wheezing and bronchitis, were significantly more in the case group than the control group. At the beginning of the study, there was no significant difference between the case and control groups regarding the pulmonary indices of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), peak expiratory flow and FEV1/FVC; however, after 2 years of exposure to flour dust, the pulmonary indices significantly decreased in the case group and showed a restrictive pattern. Based on the linear regression model, the most important predictor variables of FVC and FEV1 were age, body mass index, smoking and level of exposure to respirable flour dust. Conclusions: There is a strong correlation between chronic exposure to flour dust and the incidence of pulmonary complications and reduced pulmonary functions.
Keywords: cohort study; pulmonary symptoms; restrictive pattern.