1. Department of Occupational Medicine, University Research Clinic, Danish Ramazzini Centre, Goedstrup Hospital , 7400 Herning , Denmark
2. Department of Occupational Medicine, Danish Ramazzini Centre, Aarhus University Hospital , 8200 Aarhus N , Denmark
3. Department of Public Health, Research Unit for Environment, Occupation and Health, Danish Ramazzini Centre, Aarhus University , 8000 Aarhus C , Denmark
4. Department of Occupational and Environmental Medicine, Danish Ramazzini Centre, Aalborg University Hospital , 9000 Aalborg , Denmark
5. Department of Occupational and Environmental Medicine, Bispebjerg and Frederiksberg Hospital, University of Copenhagen , 2400 Copenhagen NV , Denmark