A Study of the Incidence of Cancer of the Lung and Larynx

XIII Summary The death certificates for cancer of the lung and of the larynx in males from England and Wales for the years 1921–32 inclusive, numbering 18,280, have been investigated. Sources of error in statistical work on death certificates are discussed. Latterly autopsies have been made upon about 28 per cent, of cases of cancer of the lung, and 9 per cent, of cases of cancer of the larynx. The increase in the recorded cases of lung cancer is not nearly accounted for by the increase of data obtained by autopsy. The agricultural and coal-mining industries show a low incidence of cancer of the lung and of the larynx. The factors which lead to silicosis appear not to be very active in producing cancer of the lung or larynx, but in metal grinders the incidence of cancer of the lung is 2¼ times that in the general population. A group of open-air occupations, where there is exposure to the dust of roads, have rather high ratios for cancer of the lung and of the larynx with the exception that motor drivers have a normal liability to cancer of the larynx. On the whole, no occupation involving exposure to any kind of dust has been found in which there is any very high incidence of cancer of the lung or larynx. Cases of cancer of the lung in asbestos workers are described in recent literature, but none has been found among the certificates considered here (up to 1932). Workers exposed to coal gas and tar, and those engaged in the preparation and sale of tobacco, tend to show an increased prevalence of cancer of the lung. Occupations concerned with the supply of alcohol have a high incidence of cancer of the larynx. To investigate the occupational incidence of cancer thoroughly one should have before one, simultaneously, comparable figures for cancer of all parts of the body which could be effected by an external agent. With regard to the view, that the recent rapid increase in recorded deaths from cancer of the lung is due to the detection of more cases by improved diagnosis, the very moderate ratio (129) for cancer of the lung in medical men is noteworthy, for this is an occupation where the availability of the existing methods for the detection of cancer is presumably at a maximum. Data are given of the prevalence of cancer of the lung and larynx in men and in women, and of the rate of increase in the two sexes in recent years. The greater incidence of cancer of the lung upon men than upon women is discussed. The recent rate of increase of cancer of the lung in men is found to be not much greater than that in women, when these increases are reckoned in percentages. The increase in recorded cases of cancer of the lung may be due to (1) an actual increase; (2) improvement in diagnosis; (3) fashion in diagnosis; or to any combination of these factors. A comparison is made between the increase of cancer of the lung, and of cancer of the prostate; the number of deaths attributed to cancer of the prostate appears to have reached a steady level. No special occupations have been found to which the increase in the total of cases of cancer of the lung can be attributed; rural workers show an increase which is not much less than that in the general population. No evidence has been found that tarring of roads has affected the incidence of cancer of the lung upon the general population. Such data as are available suggest that coal tar in the atmosphere, whether derived from roads, domestic chimneys, or any other source, does not readily give rise to cancer of the lung. Cotton-mule spinners show an especially small liability to cancer of the lung although they inhale air sprayed with an oil which produces cancer of the skin. Improvements in diagnosis must have led to the detection of a larger proportion of the existing cases of cancer of the lung; whether there has been an actual increase in these cases cannot be decided from the data presented here, but a source of evidence on this question is suggested. We are indebted to the Registrar-General for the data considered in this paper, and also for kindly permitting us to use some figures which have not yet been officially made public. We have received much assistance in the classification of occupations from some members of the Staff of the General Register Office, to whom we wish to express our gratitude. We wish to thank also Dr J. C. Bridge, Senior Medical Inspector of Factories, for information upon various matters, and especially upon silicosis. We are greatly indebted to Miss L. D. Henderson for much assistance in carrying out the calculations.