1. Department of Public Health, Section of Environmental Health, University of Copenhagen , Øster Farimagsgade 5A, DK-1014 Copenhagen K , Denmark
2. Division of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University , SE-22363 Lund , Sweden
3. Ergonomics and Aerosol Technology, Lund University , SE-22100 Lund , Sweden
4. NanoLund, Lund University , SE-22100 Lund , Sweden
5. Division of Combustion Engines, Lund University , SE-221 00 Lund , Sweden