I read with great interest Schade and Swanson's paper [ 19881 coupled with Lilienfeld's editorial [ 19881 because this is an increasingly important subject as the use of epidemiological methods of investigating industry-associated morbidity and mortality proliferate.
My interest in this subject was aroused by the work done by Liddell 27 years ago [1973] in which he demonstrated how the relatives of the deceased tended to "promote" into more senior occupations. For some years, medico-legal work [Adelstein, 1969; Unknown, 19711 has recognized the importance of a detailed occupational history if the relative risks of a variety of occupations are to be assessed. Computerization of personal occupational records can be of great help if the employee lives and dies working for only one employer but may not be of much use if such records are scattered over half-a-dozen companies. Changes in the pattern of employment in the United Kingdom in the 1980s can mean that a man made redundant in Scotland might find work in the West Midlands and finally find a permanent job in the South East. The asbestos that contributed to his death might have been inhaled in Scotland.
So it is vitally important that occupational histories be carefully taken and the results critically evaluated before conclusions are drawn. Another aspect of the same problem is the accuracy of death certification, another subject that aroused my interest when I had a spirited argument with an epidemiologist friend, the validity of whose conclusions was based solely on the death certificate [Unknown, 19661. Until autopsies become more or less routine, the accuracy of death certificates will always be less than 100%.