1. Department of Internal Medicine, Spaarne Gasthuis, P.O. Box 417, 2000 AK Haarlem and Hoofddorp, The Netherlands
2. Spaarne Gasthuis Academy, P.O. Box 417, 2000 AK Haarlem and Hoofdorp, The Netherlands
3. Centre for Environment and Health, University of Leuven (KU Leuven), P.O. Box 952, 3000 Leuven, Belgium
4. Department of Epidemiology, School of Medicine in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
5. IDEWE, External Service for Prevention and Protection at Work, 3000 Leuven, Belgium
6. Department of Paediatrics, Spaarne Gasthuis, P.O. Box 417, 2000 AK Haarlem and Hoofddorp, The Netherlands
7. Leuven Child and Health Institute, University of Leuven (KU Leuven), P.O. Box 3717, 3000 Leuven, Belgium
8. Department of Development and Regeneration, University of Leuven (KU Leuven), P.O. Box 611, 3000 Leuven, Belgium