[1] NIOH, Dept Toxicol, ZA-2000 Johannesburg, South Africa
[2] Wits Univ, Dept Haematol & Mol Med, Wits, South Africa
[3] Univ Pretoria, Sch Hlth Syst & Publ Hlth, ZA-0002 Pretoria, South Africa
[4] Wits Univ, Sch Publ Hlth, Wits, South Africa
[5] Med Forsch gGmbH, Particle Res Core, Dusseldorf, Germany
[6] W Virginia Univ, Med Ctr, Morgantown, WV 26506 USA
[7] NIOSH, Morgantown, WV USA
[8] Univ Edinburgh, Sch Med, ELEGI Colt Lab, Edinburgh EH9 8AG, Midlothian, Scotland