1. National Institute for Occupational Safety and Health; Respiratory Health Division; 1095 Willowdale Road Morgantown West Virginia USA 26505
2. University of Texas School of Public Health; Department of Epidemiology, Human Genetics and Environmental Sciences; 1200 Pressler ST#W1004a Houston Texas USA TX 77030
3. University of Arkansas for Medical Sciences; Department of Epidemiology; 4301 W Markham St, Slot#820 Little Rock Arkansas USA 72205
4. Coronel Institute of Occupational Health, Academic Medical Center; Netherlands Center of Occupational Diseases; PO Box 22660 Amsterdam Netherlands 1100 DD
5. University of Alberta; Department of Medicine; Edmonton AB Canada
6. University of Toronto; Department of Medicine, and Dalla Lana School of Public Health; Toronto Western Hospital EW7-449 399 Bathurst St Toronto ON Canada M5T 2S8
7. University of Bologna; Department of Medical and Surgical Sciences; UO Medicina del Lavoro - Policlinico Sant'Orsola-Malpighi Via Palagi 9 Bologna Italy 40138