Further studies of the dust in lungs of coal-miners.

In a previous communication (King and Nagelschmidt, 1945), analytical data were given for the amount and composition of the dust found in the lungs of 54 coalworkers from South Wales. Coal, total silica, quartz, mica, and kaolin were determined as the percentages of dried lung tissue, and the results were related to type of work and degree of pathology. The main findings were the following: (1) The kind of occupation was clearly revealed in the composition of the dust from the lungs. For instance, its coal percentage varied from 25 for rock-workers* to 95 for trimmers and screenworkers. (2) The average dust composition in the lungs of 27 anthracite workers was very similar to the composition of the airborne dusts at the coal face, and thus there was no evidence of any mineral change in the lung, as far as the ratio of coal to non-coal or the relative proportions of mica, quartz, and kaolin were concerned. (3) In the pathological classification three grades were distinguished: reticulation, mixed nodulation, and confluent fibrosis. In addition, three rockworkers were classed as a silicotic nodulation group. The concentrations of coal, quartz, and total silica varied considerably within each pathological group, but increased only very slightly from one group to the next, except for the silicotic nodulation group; in the more homogeneous group of the 27 anthracite colliers the increases in lung dust components with increasing grade of pathology were not significant at the 95% significance level. In the discussion of the results it was stated that the silicotic nodulation was due to quartz, but that it could not be decided on the basis of the data whether reticulation was also a quartz effect, modified by the large amounts of coal and other