1. Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital, Göteborg, Sweden
2. Department of Occupational Medicine, Haukeland University Hospital, Bergen, Norway
3. Lung Clinic, Tartu University Hospital, Tartu, Estonia
4. Department of Environmental and Occupational Medicine, Institute of Public Health, Aarhus University, Aarhus, Denmark
5. Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, Umeå, Sweden
6. Department of Respiratory Medicine and Sleep, Landspitali University Hospital, Reykjavik, Iceland; and Medical Faculty, University of Iceland, Reykjavik, Iceland
7. Department of Medical Sciences, Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden