1. From the Department of Pediatrics, Sophia Children's Hospital, Erasmus University, Rotterdam, The Netherlands;
2. Departments of Chronic Disease Epidemiology and Infectious Diseases Epidemiology, National Institute of Public Health and the Environment, Bilthoven, The Netherlands;
3. Department of Environmental and Occupational Health, Institute for Risk Assessment Sciences, University of Utrecht, Utrecht, The Netherlands; and
4. Beatrix Children's Hospital, Groningen University, Groningen, The Netherlands.