Autopsy study of coalminers’ lungs – phase II. Final report on CEC Contract 7246-15/8/001

This report is based on a post mortem study of the lungs and hearts of various groups of coalworkers drawn from an original cohort of 500 men. The men had worked in collieries which took part in Pneumoconiosis Field Research and which covered the range of mining conditions in Britain.The aim of the study was to relate pathological evidence of pneumoconiosis, emphysema and bronchitis and the radiographic appearances of pneumoconiosis to both the dust retained in the lung and the respirable dust to which the men were exposed. Also included were studies of right-sided heart disease and respiratory function during life in relation to lung pathology.Cases were sub-divided in a number of ways. Divisions could be made on the basis of the presence or absence of a feature such as dust lesions of a particular size and type, emphysema or right ventricular hypertrophy. For some assessments individual cases were more closely characterised by, for example, sizing and counting of dust lesions. Further division was made according to the rank of coal mined. This division was usually into ‘high’ and ‘low’ rank groups; being above or below 88% carbon content.There was an association between the weights (in lung) of retained dust, iron, calcium and phosphate and the severity of pneumoconiosis, the mean weights being least in cases showing only macules and greatest in those showing progressive massive fibrosis (PMF). For ‘low’ rank cases only there was a difference in the composition of lung dust such that cases showing PMF contained dust with proportionately more ash and less coal than cases showing only macules. In some cases, particularly those drawn from ‘low’ rank areas or showing PMF, the proportion of ash compoments was higher than would be expected from the composition of respirable coalmine dust. This observation might be explained by assuming different clearance rates and/or routes for the coal and ash (particularly quartz) compoments of the dust. Some support for the latter was offered by the finding that the proportion of quartz in dust was much higher in the hilar lymph nodes than in the lung.Differences in lung dust content and composition were broadly reflected in the macroscopic and microscopic appearances of the lung. In general, the number of most types of dust lesions (macules and nodules grouped by size) and the area of massive fibrosis increased with increasing amounts of dust in the lungs. The number of fibrotic nodules was also positively related to the amount of ash in lung dust. There were, however, no significant differences in the dust composition in different types of lesion within a given lung. Two patterns of microscopic features were recognised. High ash content in lung dust was associated with a type of fibrotic nodule which showed a clear centre and with the formation of PMF by aggregation of such lesions. On the other hand, high coal content was related to densely packed dust in all lesions, evenly pigmented fibrotic nodules and PMF which seemed to be a solitary mass.There was a clear and consistent pattern of an increase in the proportion of cases showing radiographic category 0/1 or higher with increasing weight of retained lung dust. The profusion of small rounded opacities was positively related to the weight of retained lung dust and that of its measured constituents. Cases showing p type opacities were associated with the highest mean lung dust content regardless of the rank of coal mined. In general, cases showing r opacities had the lowest mean lung dust content. This difference could not be explained by differences in profusion scores for the types of opacity. Lung examination showed that p opacities were associated with dust foci which were smaller, less often palpable and more numerous than those presenting as r opacities. It is reasonable to conclude that profusion score is affected by the size and number of dust lesions in addition to the mass and composition of retained dust.The prevalence of right ventricular hypertrophy was significantly greater in PMF cases than in those without massive fibrosis. There was no obvious association between simple pneumoconiosis and right ventricular hypertrophy. In PMF cases both the size of the PMF lesion and the extent of panacinar emphysema were positively related to the degree of right ventricular hypertrophy. It is recognised that both chronic hypoxia and bronchiolbstenosis, which could not be included in the present study, may relate more closely to right ventricular hypertrophy.Smoking contributed significantly to the enlargement of bronchial mucous glands (as an indicator of chronic bronchitis). Over and above this, exposure to coalmine dust was also significantly related to a measure of bronchial gland enlargement. This observation adds further support to a concept of ‘industrial bronchitis’.Age, smoking and the extent of pneumoconiosis all contributed to the probability of showing panacinar and centriacinar emphysema. The prevalence, but not the extent, of centriacinaremphysema was additionally related to the amount of dust retained in the lung. The effect of dust exposure was such that the greater the amount of ash in the respirable dust the less the likelihood of showing centriacinar emphysema. There was no clear indication that emphysema caused accumulation of dust.Cases who had lower than expected values of FEVj showed bronchial mucous gland enlargement and greater amounts of emphysema. The same cases had been exposed to more respirable dust than those with a normal FEVa. When rate of decline of EEVj was examined the proportion of PMF cases was highest in the group with the steepest decline (> – 75 ml/yr).