The authors investigated the influence of working conditions--with particular reference to dust and fluorite pollution--on the epidemiology of chronic bronchitis in 197 subjects working in a fertilizer producing plant in Krakow (Poland). The investigation included history, respiratory function tests (VC, TVC), height and weight measurement, rhinolaryngologic examination, nasal mucosa cytology and physical examination. The environmental survey included measurements of the dust respirable fraction and fluorite concentration in the air. The prevalence of chronic bronchitis was found to increase with the length of working activity and to be much higher in smokers than in non-smokers. Furthermore, in subjects working at the sites with the worst environmental situations it proved to be twice as high as in the remainders. Likewise higher proved to be the prevalence of laryngitis and sinusitis. The prevalence of chronic bronchitis was found to be much higher in workmen with more marked spirometric changes. In subjects affected with chronic bronchitis alterations of the nasal mucosa epithelium were also found.