1. Department of Clinical Science, University of Bergen, 5021 Bergen, Norway
2. Section for Microbiology, Department of Biology, Aarhus University, 8000 Aarhus, Denmark
3. Department of Public Health, Environment, Work and Health, Danish Ramazzini Center, Aarhus University, 8000 Aarhus, Denmark
4. Department of Occupational Medicine, Danish Ramazzini Center, Aarhus University Hospital, 8200 Aarhus, Denmark
5. Faculty of Medicine, University of Iceland, 102 Reykjavík, Iceland
6. Department of Occupational and Environmental Medicine, University of Gothenburg, 405 30 Gothenburg, Sweden
7. Department of Medical Sciences: Respiratory, Allergy, Sleep Research, Uppsala University, 751 85 Uppsala, Sweden
8. Department of Medical Sciences: Clinical Physiology, Uppsala University, 751 85 Uppsala, Sweden
9. Tartu University Hospital, Lung Clinic, 50406 Tartu, Estonia
10. Division of Occupational and Environmental Medicine, Department of Public Health and Clinical Medicine, Umeå University, 901 87 Umeå, Sweden
11. Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, 751 85 Uppsala, Sweden
12. Department of Occupational Medicine, Haukeland University Hospital, 5053 Bergen, Norway
13. Centre for International Health, University of Bergen Department of Global Public Health and Primary Care, 5009 Bergen, Norway
14. Department of Anesthesia and Intensive Care, Landspitali University Hospital, 101 Reykjavik, Iceland
15. Institute for Risk Assessment Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CS Utrecht, The Netherlands