1. 1 Pneumology Department, Medicine Faculty , «Ovidius» University of Constanta , Romania
2. 2 PhD Medicine School , «Ovidius» University of Constanta , Romania
3. 3 Physiology Department, Medicine Faculty , «Ovidius» University of Constanta , Romania
4. 4 Clinical Hospital of Pneumology , Constanta , Romania
5. 5 Occupational Department, Medicine Faculty , «Carol Davila» University of Medicine and Pharmacy , Bucharest , Romania
6. 6 Occupational Department , Clinical Colentina Hospital Bucharest , Romania