Factors influencing the occurrence of progressive massive fibrosis of various types. Final report on CEC Contract no. 7248/33/041

During the past decade, there have been major advances in understanding the factors influencing the occurrence of Progressive Massive Fibrosis (PMF) in coalminers. Studies of miners in Britain, with support both of British Coal and of the European Community, have clearly shown that incidence is related to age; to cumulative exposure to respirable dust; to simple pneumoconiosis category (CWP); to the carbon content of the coal; and to physique, as expressed via Quetelet’s index. Higher risks in ex-miners than in miners have been explained in terms of the ex-miner’s age, dust exposure, etc.: there was no evidence of particular susceptibility on their part. Smoking habit, and lung function level, appear to be unrelated to PMF development. The role of dust composition, particle size, residence time of dust in the lung, and respiratory symptoms was investigated, but remained unclear.Related work, on radiological classification of PMF, led to the distinction of six different types of the disease; film reading trials indicated that agreement within and between readers was sufficiently good that type of PMF might be used in epidemiological studies. On that basis, the present study was set up in order to investigate different types of PMF more comprehensively than before; and in particular, to see if distinguishing PMF by type might lead to clarification of the role of causal or predisposing factors.