Four groups of males subjects will be recruited (G1 : occupational COPD (6 groups of 60 subjects, corresponding to 6 groups of occupational agents) ; G2 : non occupational COPD (n = 60) ; G3 : subjects with similar occupational exposure to G1 subjects but without COPD (6 groups of 60 subjects) ; G4 : subjects free of occupational exposure and of COPD (n = 60)), paired on tobacco-smoking and age. For each subject, information on clinical data, lung function parameters, occupation history and blood samples will be collected.