1. Environmental and Occupational Medicine, Department of Public Health and Clinical Medicine, Umea University, Umea, Sweden
2. Unit of Industrial Toxicology, Catholic University of Louvain, Brussels, Belgium
3. Respiratory Medicine and Allergy, Department of Public Health and Clinical Medicine
4. Paediatrics, Department of Clinical Sciences, and
5. Clinical Physiology, Department of Surgical and Peri-operative Sciences, Umea University, Umea, Sweden