1. Department of Medical Sciences: Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden
2. Centre for Clinical Research, Haukeland University Hospital, Bergen, Norway
3. Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
4. Department of Surgical and Perioperative Sciences, Surgery, Umea University, Umea, Sweden
5. Department of Public Health, Section for Environment, Occupation and Health, Aarhus University, Aarhus, Denmark
6. Department of Respiratory Medicine and Sleep, the National University Hospital of Iceland, University of Iceland, Reykjavik, Iceland
7. Lung Clinic, Tartu University Clinics, Tartu, Estonia
8. Department of Medical Sciences: Respiratory, Allergy and Sleep Research, Uppsala University, Uppsala, Sweden