1. London School of Hygiene and Tropical Medicine, London, UK
2. Health and Safety Executive, Bootle, UK
3. Health and Safety Laboratory, Buxton, UK
4. Department of Cardiovascular Sciences, University of Leicester, UK
5. Department of Histopathology, Royal Brompton and Harefield Hospitals NHS Foundation Trust, and National Heart and Lung Institute, Imperial College, London, UK
6. Department of Cellular Pathology, Leeds Teaching Hospitals NHS Trust, Leeds, UK
7. Leeds Institute of Cancer and Pathology, University of Leeds, UK
8. Clinical Operational Research Unit, University College Hospital, London, UK