1. Department of Food, Water and Cosmetics, Norwegian Institute of Public Health, Oslo, Norway
2. Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
3. Department of Pediatrics, Oslo University Hospital, Oslo, Norway
4. Faculty of Medicine, University of Oslo, Oslo, Norway
5. National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA