[1] Univ Paris 06, Epidemiol Allerg & Resp Dis Dept, UMRS 707, INSERM, F-75571 Paris 12, France
[2] Rome E Hlth Author, Dept Epidemiol, Rome, Italy
[3] Inst Municipal Invest Med, Ctr Res Environm Epidemiol, E-08003 Barcelona, Spain
[4] Univ Utrecht, Inst Risk Assessment Sci, NL-3508 TC Utrecht, Netherlands