[1] Hop Bicetre, INSERM, U292, Le Kremlin Bicetre, France
[2] Aarhus Univ Hosp, Dept Occupat Med, Steno Inst Publ Hlth, DK-8000 Aarhus C, Denmark
[3] Imperial Coll Sch Med, London W2 1PG, England
[4] Hospices Civils Strasbourg, Ctr Etude & Conservat Sperme, F-67091 Strasbourg, France