[1] Natl Inst Occupat Hlth, DK-2100 Copenhagen O, Denmark
[2] Norwegian Inst Publ Hlth, Dept Environm Immunol, Div Environm Med, NO-0403 Oslo, Norway
[3] Natl Univ Hosp, Allergy Clin, DK-2100 Copenhagen O, Denmark
[4] Natl Working Environm Author, DK-2100 Copenhagen O, Denmark
[5] Danish Environm Protect Agcy, DK-1401 Copenhagen K, Denmark