Affiliation: | National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands (S. Hahné, L. Mollema, C. Swaan, H. de Melker, R. van Binnendijk);Municipal Health Service, The Hague, the Netherlands (E. van Velzen, E. de Coster );Municipal Health Service, Utrecht, the Netherlands (M.J.M. te Wierik) |