1 Specialist Registrar, Occupational Health Department, St George's University Hospitals National Health Service Foundation Trust, London SW17 0QT, United Kingdom.
2 Consultant Physician, St George's University Hospitals National Health Service Foundation Trust, London LE1 5WW, United Kingdom.
3 Consultant Physician, Occupational Health Department, University Hospitals of Leicester National Health Service Trust, Leicester SW17 0QT, United Kingdom.