Coalmining, emphysema and compensation.

Sir,-In his editorial, Seaton (1990; 47:433-5) makes a plea for awarding compensation to coal miners with simple coal workers' pneumoconiosis (CWP) who have a reduced forced expiratory volume in one second (FEV,). He justifies his recommendation by attributing the reduction in the FEV, to emphysema, which he claims has been induced by coal dust. In doing so he states that the Industrial Injuries Advisory Council (IIAC) did not appreciate the strength or logic of his previous submission; a statement that would seem to imply that the members of the IIAC are perhaps a trifle obtuse. We share Seaton's view that coal miners have an excess of emphysema over and above the general population. Indeed, some of our earlier studies carried out by the United States Public Health Service, and in which he participated, made this evident. In this connection, the Appalachian Laboratory for Occupational Respiratory Disease (ALFORD) showed that simple CWP in non-smokers was associated with an increase in residual volume (RV) and total lung capacity (TLC) and in some instances a slight to moderate loss of elastic recoil. ''3 Hankinson and colleagues who were working at ALFORD also showed that simple CWP was associated with an increase in air space size.4 Although some of the increase in RV occurring in non-smoking coal miners with simple CWP can be attributed to industrial bronchitis, this cannot explain the increase in TLC.l 25 The increment in TLC must be a consequence of the fact that there is decreased elastic recoil of the lungs. We also accept that cumulative exposure to respirable dust is associated with a greater prevalence of both pneumoconiosis and fibrosis and that the severity of the latter is related to the category of the simple CWP. Similarly we accept the concept that the higher the category ofsimpleCWP and fibrosis, the more extensive is the emphysema.6 Seaton's next inference that the emphysema which is present causes obstruction is, however, much more difficult to accept. Were this the case, the FEVI should decrease as the category of simple CWP increases in much the same manner as the RV and TLC increase as the category of CWP worsens. That it does not is all too obvious from other studies.2 78By contrast, in cigarette smoke induced emphysema the extent of the emphysema is clearly related to FEVy, RV, and TLC. Similarly we ask why is it that, despite the increased air space size shown in subjects with simple CWP, there is no associated fall in the FEVy, and why is the mean FEVy of subjects with category 0 the same as those with simple CWP? 27 Surely if there is more emphysema in those with simple CWP, and the emphysema is associated with airways obstruction, the FEV, should decrease with increasing category of simple CWP. Seaton fortifies his argument by alluding to 95 non-smoking miners with CWP, who showed an inverse relation between FEVy and the extent of centracinar emphysema present in them. We can show him similar findings, however, and a slightly reduced FEV, in a similarly selected and comparably dust exposed group of non-smoking coal miners without simple CWP who do not have any significant loss of elastic recoil or other evidence of emphysema, but who have bronchitis. It is also pertinent to note that a rather similar decline in the FEVy and the FEF,,7, is present in gold miners who are exposed to silica.9 Here again cumulative dust exposure is associated with a greater prevalence of silicosis and a lower than normal FEV, and FEF2,575, but as the Institute of Occupational Medicine and others have pointed out, the one thing silica is not associated with is emphysema.6"0 This also needs to be borne in mind in view of Seaton's endorsement of the hypothesis, "wherever there is fibrosis, there is also emphysema. " Certainly this is not true of simple silicosis, healed miliary tuberculosis, and the various fungal diseases seen in North America. Moreover, one wonders whether the overdistension and airways obstruction that are seen in advanced tuberculosis and sarcoidosis have anything in common with focal dust emphysema of coal miners. We support the concept expressed in the Pearson Report that -equal disability should receive equal compensation, no matter whether the cause is occupationally related, natural disease, or another person's negligence. What is necessary is a fair and uniformly administered system, not a system that, on somewhat tenuous evidence, rewards a smoking coal miner with airways obstruction while ignoring a smoking slate worker with the same problem. In trying to convince others, Seaton seems to have convinced himself. We would remind him he also failed to convince the late Archie Cochrane, whose many contributions Seaton generously recognised. We hope the IIAC will give due weight to the old adage, namely, "Never to swallow anything whole unless you happen to be a python, otherwise you might choke on it. " J B L GEE Pulmonary and Critical Care Section, Department of Internal Medicine, Yale University School of Medicine, 50 38 LMP, PO Box 3333, Newhaven, Connecticut 06510-8057 USA W K C MORGAN Chest Diseases Unit, University Hospital, PO Box 5339,339 Windermere Road, London, Ontario, Canada N6A 5AS