[Prevalence of bronchitis in socio-professional groups. III. Unexposed workers (author's transl)].

Besides the two groups of exposed workers (building workers and workers of a steel mill), a reference group of age-matched (40--60 years) unexposed workers was studied. They were examined by the same procedures (interrogation by ESC questionnaire, vital capacity, forced expiratory volume in 1 sec residual volume, apnea CO test and steady-state Co test at rest and exercise of 40 W. Results are presented according to age and smoking habits. They are compared with results observed in the two exposed groups, and discussed.