1. Environmental Health Department, National Institute for Health and Welfare, Kuopio, Finland
2. School of Public Health and General Practice, University of Kuopio, Kuopio, Finland
3. Institute of Clinical Chemistry and Molecular Diagnostics, Philipps University Marburg, Germany
4. Department of Internal Medicine, Helios Hospital Leipziger Land, Borna, Germany
5. Pediatric Research Center, Tampere University and University Hospital, University of Tampere, Tampere, Finland
6. Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland
7. Department of Allergy and Pulmonology, University of Munich Children's Hospital, Munich, Germany