1. Department of Occupational Medicine, Eskisehir Yunus Emre Hospital, Eskisehir, Turkey;
2. Department of Public Health, Faculty of Medicine, Hacettepe University, Ankara, Turkey;
3. Department of Pulmonary Medicine, Faculty of Medicine, Hacettepe University, Ankara, Turkey;
4. Department of Public Health, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey