1. OLIN Studies, Department of Medicine, Sunderby Central Hospital of Norrbotten, Luleå, Sweden;
2. Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York;
3. Department of Internal Medicine/Respiratory Medicine and Allergology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; and
4. Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, University of Umeå, Umeå, Sweden