[1] Tech Univ Dresden, Inst & Policlin Occupat & Social Med IPAS, D-01307 Dresden, Germany
[2] German Fed Inst Occupat Safety & Hlth BAuA, Berlin, Germany
[3] Univ Freiburg, Dept Pneumol, Univ Med Ctr, D-79106 Freiburg, Germany
[4] Res Ctr Borstel, Dept Pneumol, Borstel, Germany
[5] Goethe Univ Frankfurt, Inst & Policlin Occupat & Environm Med, Frankfurt, Germany
[6] Johannes Gutenberg Univ Mainz, Inst Occupat Social & Environm Med, Mainz, Germany