The pathology and dust content of lungs from 261 coalminers in relation to the appearances of their chest radiographs taken within four years of death were examined. Radiological opacities of coalworkers' pneumoconiosis were more profuse the more dust was retained in lungs. Among the men who had mined low rank coal-that is, with a relatively high proportion of ash-the increase in profusion was most closely related to the ash component of the dust, whereas in men who had mined high rank coal both coal and ash increased in the lungs in relation to radiological profusion. The fine p type of opacity was found to be associated with more dust and a higher proportion of coal and less ash than the nodular r opacity, and was also more likely to be associated with emphysema. The pathological basis of the different types of opacity found on the radiographs of coalminers related to the number, size, and nodularity of the dust lesions. Larger fibrotic lesions were likely to appear as r opacities, whereas fine reticular dust deposition was most likely to present as p opacities, q opacities showing a mixture of appearances. The study has shown that the composition of dust retained in the lung, as well as its amount, makes an important contribution to the radiographic appearances of pneumoconiosis. In particular, the r type of lesion on the radiograph of a low rank coalminer indicates the possibility of a silicotic like lesion.The relation between exposure to coalmine dust and the radiographic profusion of small opacities in simple pneumoconiosis has been well documented. '-3 The primary relation appears to be with exposure to mixed respirable dust, and no generally applicable additional effect of the ash component of the dust has been shown.3 Consequently it seems logical to suppose that radiographic opacities are due largely to an accumulation of dust and, indeed, such an association between retained dust and profusion of opacities has been clearly shownm.45Most workers, however, describe groups in which the radiological changes appear disproportionate for the amount of dust in the lungs and recognise that factors other than the mass of retained dust contribute to the radiographic picture. It has been noted, for example, that the higher the proportion of coal in the retained dust, the more dust is required to produce a given radiological category,6 and Caplan found that the radiological category was more closely associated with the profusion of fibrotic nodules in the lung than with the profusion of dust foci of all types.7The principal aim of the present study was to examine further the factors that affect the relation between the profusion of small opacities and the mass of retained lung dust. Additional aims were to determine the pathological basis for the three types of small rounded opacity and to verify the reported association of both the p type of small rounded opacity8 and irregular opacities9 with the presence of emphysema. Methods SOURCE AND CLASSIFICATION OF RADIOGRAPHSThe study was based on 261 men drawn from a...

The relation between dust exposure, retained lung dust, and pneumoconiosis have been examined in 430 dead coalminers who had participated in a large scale epidemiological survey of respiratory health. The men were divided into three groups depending on the presence of particular lesions in their lungs. Lungs containing no fibrotic lesions in excess of 1 mm were included in the "M" group, those with fibrotic lesions of between 1 mm and 9 mm in diameter were included in the "F" group, and those with any lesion 10mm or more were categorised as having progressive massive fibrosis (PMF). The men were further divided into four groups according to the rank of coal mined at the colliery of employment. The mean weight of lung dust increased over the pathological range (M-.F-+PMF) regardless of the rank of coal mined. The men with PMF had not received unusually high exposures to dust in life but were found to have accumulated more dust in their lungs per unit of dust exposure than men without PMF, providing further evidence for differences in the patterns of deposition or clearance, or both, of dust in these men compared with those who do not develop PMF. For men who had mined the higher rank coals there was no difference in the composition of the lung dust between the pathological groups. Lungs from men mining low rank coal, however, showed a striking increase in the proportion of ash over the pathological groups (M, F, and PMF). In men who had mined low rank coal the proportion of ash in the airborne dust to which they had been exposed and in the dust retained in their lungs was, as expected, greater than in men who had worked with higher rank coals. For the same men, and particularly associated with the presence of some dust related fibrosis, the proportion of ash in retained dust was higher than that in the dust to which the men were exposed suggesting the occurrence of selective deposition or retention of the mineral components of dust in this group.Early work on miners from south Wales suggested that the pathological grade of pneumoconiosis was directly proportional to the mass of dust recovered from the lungs at necropsy' and that the composition of the retained dust was little different from that encountered at the workplace.2 Progressive massive fibrosis (PMF) was considered to be either a complication resulting from a secondary factor, widely believed to be tuberculosis, or a form of silicosis.Regional variations in the prevalence of pneumoconiosis, particularly PMF, prompted an interest in studies of miners from areas other than south Wales. The results showed that the amount of dust found in lungs from north west England was somewhat lower than in south Wales and that this dust had a significantly greater ash content.34 Subsequent work, covering most coalfields in Britain, indicated Accepted 14 April 1986 that the composition of the lung dust was related to the rank of coal mined.5At the same time the accumulation of dust in lungs was examined. Lungs from hauliers and other underground workers were...

The dust content and composition of lesions and hilar lymph nodes from the lungs of British coalworkers have been examined. Samples of macules, fibrotic nodules, and massive fibrosis (both peripheral and central sites) were dissected from 49 lungs. The highest mean dust concentrations (about 20%) were found in nodules and massive fibrosis. Overall there were no significant differences between the selected lesion types and their respective whole lung dust composition, although the central sites of massive fibrosis were found to contain on average a higher proportion of coal and a lower proportion of ash and its measured constituents, quartz and kaolin plus mica, than the edge of the lesion (p < 0-001 for each component). There were striking differences between recovered lung and lymph node dusts. An examination of 180 specimens showed a mean quartz in lymph node dust of 20-3% compared with 611% in lung dust. As expected the proportion of quartz was greater in lymph nodes and lungs from men who had worked "low" rank (high ash) coal. Materials and methods SELECTION OF LUNGSThe original necropsy study included 500 sets of lungs with a measure of lung dust content available for 490 of these specimens. In the course of the study one lung from each pair was retained in store, the other having been used in determining the overall dust burden.

The lungs of 490 British coal miners were examined for comparisons of the lesions of coal workers' pneumoconiosis with lung dust content and dust exposure. Variations were found in histological appearances that formed a range, the extremes of which indicated two separate patterns of disease. In men from high rank collieries, whose lung dust had a high carbon content and little ash, most of the nodules of simple pneumoconiosis were evenly pigmented with dust, and where progressive massive fibrosis (lesions greater than 1 cm in diameter) had developed, this appeared to be by the enlargement of a single lesion. In men from low rank collieries where the ash content of lung dust was high, the centers of the nodules were often free of dust particles and in extreme cases these lesions were very similar to silicotic nodules. If PMF developed in these cases, it often appeared to be by the fusion of closely spaced groups of smaller nodules. While there appeared to be little difference between the lung dust composition of men from high rank collieries and the dust to which they had been exposed, in men from low rank collieries the proportion of the noncoal minerals in the lungs was usually higher than it had been in the mine dust. This indicated some form of differential retention of these components, which was progressively more marked in men with the more serious grades of pneumoconiosis.

The relation between the profusion and predominant type of small rounded opacities on chest radiographs taken within four years of death and the postmortem counts of dust lesions in four classes (macules, "pinhead" fibrotic nodules, nodules 1-3 mm, and nodules > 3-9 mm in diameter) has been examined for 71 coalworkers without progressive massive fibrosis. The radiographs were categorised by four readers independently, according to the ILO classification. For subjects considered by each reader to present predominantly p type opacities, increasing opacity profusion was exclusively and significantly associated with an increase in the number of pinhead fibrotic nodules. Numbers of nodules measuring 1-3 mm and > 3-9 mm in diameter both showed significant linear associations with opacity profusion category in subjects presenting predominantly q opacities, the closer association being observed with the smaller lesions. These observations held true for all readers. Opacities of type r were rarely considered to be the predominant type. For the reader who recorded the maximum number of such cases, opacity profusion was not significantly related to the numbers of dust lesions in any of the lesion classes. Nevertheless, the closest association was observed with nodules measuring > 3-9 mm in diameter. An overall significant linear association between total lung dust content and opacity profusion was found to be due mainly to subjects presenting predominantly p type opacities and to a lesser extent to those with predominantly q opacities.Radiological pathological correlations are of particular importance in coalworkers' pneumoconiosis because they are the only means of establishing how reliable the radiological classification is in assessing the extent and severity of the disease. They also provide data which may allow the visualisation of what is present in the lung when a certain radiological category is read. Although several studies of this nature have been carried out,'`4 the emphasis has been on determining how the profusion of small rounded opacities relates to the number and character of dust lesions within the lung, opacity type being largely ignored.In a recent study of "pure" opacity types we showed that the three types of small rounded opacity, p, q, and r, present somewhat different pathological features with regard to dust lesion size, shape, and extent of fibrosis.5 On the basis of these results it Accepted 8 July 1986 seemed logical to suppose that in coalworkers the relation between profusion of opacities and the number and character of dust lesions might vary according to the type of opacity. This we have investigated in the present study. We also report the results of preliminary analyses in which we considered the two factors, profusion and type of opacity, separately.Lastly, we have included data on the content and composition of lung dust in our study subjects; we thought that these data would help in the interpretation of our findings in view of the relation between the content and compositi...