1. Unit of Occupational Medicine, Department of Diagnostics and Public Health Policlinico “G. Rossi” Verona Italy
2. Unit of Epidemiology and Medical Statistics, Department of Diagnostics and Public Health University of Verona Verona Italy
3. Section of Occupational Medicine, Respiratory Diseases and Toxicology University of Perugia Perugia Italy
4. Unit of Hygiene and Preventive, Environmental and Occupational Medicine, Department of Diagnostics and Public Health University of Verona Verona Italy
5. Department of Medicine, Section of Respiratory Diseases University of Verona Verona Italy