OBJECTIVESThe possible adverse respiratory effects of airborne pollutants in sawmills have not been thoroughly investigated in Iran. Additionally, the extent to which workers are exposed to this organic dust and its associated bioaerosols has not been extensively quantified. Likewise, the predominant bacterial and fungal species associated with wood dust have not been characterized. The present study was undertaken to address these issues.METHODSOne hundred male individuals exposed to wood dust and 100 unexposed male subjects were investigated. They completed a standardized respiratory symptom questionnaire and underwent spirometry testing. Additionally, airborne concentrations of respirable and inhalable dust particles, bacteria, and fungi were measured.RESULTSThe mean concentrations of inhalable and respirable dust particles, bacteria, and fungi were found to be 2.44, 6.76 mg/m3 , 756.38, and 299.15 colony-forming units/m3 , respectively. The predominant Gram-negative bacteria in the sawmills included the Pseudomonadaceae, Klebsiella pneumoniae, and Rhinoscleromatis spp., and the predominant fungi consisted of the zygomycetes and Aspergillus spp. Respiratory symptoms were significantly more prevalent among exposed workers. Significant cross-shift decrements were noted in some pulmonary function parameters. Similarly, pre-shift spirometry results indicated that some pulmonary function parameters were significantly lower in the exposed group.CONCLUSIONSExposure to wood dust and its bioaerosols was associated with significantly higher prevalence of respiratory symptoms and both acute (i.e., partially reversible) and chronic (i.e., irreversible) decrements in the functional capacity of the lung. Additionally, the characterized bioaerosols did not differ significantly from those isolated in other parts of the world.