1. Department of Community Medicine, University of Tromsø, Tromsø, Norway
2. NILU-Norwegian Institute for Air Research, Fram Centre, Tromsø, Norway
3. University Hospital of North Norway, Tromsø, Norway
4. NILU-Norwegian Institute for Air Research, Kjeller, Norway
5. Department of Chemistry, University of Oslo, Oslo, Norway
6. Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada