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1.  Dust and Collagen Content of Lungs of Coal-Workers with Progressive Massive Fibrosis 
In order to test the silica theory of the origin of progressive massive fibrosis (P.M.F.) in coal-miners' pneumoconiosis, separate dust analyses have been made of the massive lesions and of the rest of the lung from 18 coal-workers with P.M.F. who had been employed in several coalfields. The dry weight of the massive lesions ranged from 5 to over 100 g. and the dust concentration in the P.M.F. lesions was on an average twice as high as in the rest of the lung. It was found that the quartz percentage of the lung dust was almost identical in the two samples from each lung (Table 3). The quartz content of the average lung dust (P.M.F. and “rest of lung”) of 32 cases of P.M.F. was compared with that of 58 cases of simple pneumoconiosis. The quartz content of the P.M.F. dust was slightly higher but, allowing for variable dust composition in different coalfields, the difference was not significant (Table 8). The silica theory of P.M.F. cannot be supported by this study.
Comparisons of the collagen content of the P.M.F. lesions and of the rest of the lung in 17 lungs and of lesions of P.M.F. and of simple pneumoconiosis in 31 and 27 lungs, respectively, showed no clear difference between any of the groups and surprisingly low values for the massive lesions. A possible way in which this result could be reconciled with the histopathological observations is suggested. One gram of coal-mine dust produced, on an average, 0·4 g. of dust produced between 2 and 7 g. of extra collagen.
extra collagen. In five silicotic lungs, where the lung dust contained 15 to 50% of free silica, 1 g. of dust produced between 2 and 7 g. of extra collagen.
PMCID: PMC1039198  PMID: 14046154
2.  Part I: General Observations 
Lungs from 45 coalworkers with simple pneumoconiosis have been compared with chest films obtained within two years of death. The carbon, quartz, mica, and kaolin content of the lungs was determined chemically. Large lung sections were used to assess the type and severity of emphysema and the presence of fibrous dust nodules. Histological sections were used to grade the amounts of reticulin and collagen in the simple dust foci. By using averages of four independent readings of each radiograph, subdivisions of the I.L.O. 1950 scale of categories were related to amounts of dust in the lungs.
It was found that the mean weight of total dust in the right lung was: category 0, 4·3 g.; category 1, 10·5 g.; category 2, 14·5 g.; category 3, 26·7 g.; and that the mineral and carbon contributed about equally to the radiological changes but, weight for weight, mineral contributed about nine times more than carbon. A physical explanation for this is suggested, in terms of relative absorptions of ϰ rays by carbon and mineral; the coefficients of absorption of the various dust components and “wet tissue” are compared at various wavelengths, and the effects on the radiograph are discussed. An explanation in terms of tissue reaction to dusts was also investigated but was not found to be plausible. “Mean ages of dust foci” (periods of dust retention) were studied from records of work underground, and compared with the radiological changes, the gradings for reticulin and collagen, and the presence of fibrous dust nodules. Observer variability in reading the ϰ-ray films was greater when fibrous dust nodules were present. The application of the results to the interpretation of studies of progression of simple pneumoconiosis judged from the radiograph is described.
PMCID: PMC1038031  PMID: 14437667
3.  The Dust Content of the Lungs of Coal Workers from Cumberland 
The prevalence of pneumoconiosis varies from one coalfield to another. The present investigation arose from the observation that coal-miners' lungs from west Cumberland appeared much less black and had less coal in them than lungs from South Wales coal-miners.
Dust analyses were carried out on 33 lungs of coal workers from Cumberland which had been examined histologically and graded according to the classification of Belt and King (1945). No case of massive fibrosis (grade 4) occurred and this condition seems to be rare or absent in Cumberland. Compared with South Wales coal-miners' lungs, each histological grade of simple pneumoconiosis was on an average associated with less coal dust and more rock dust in Cumberland, and silicosis due to rock work in coal-mines appeared to be relatively more frequent.
PMCID: PMC1037860  PMID: 13618519
7.  Pneumoconiosis of Kaolin Workers 
PMCID: PMC1037711  PMID: 13364154

Results 1-21 (21)