Document 71YL52RKmZabXmjRgprGmg8wo

October. 1955 cannot be confused with other pneumoconioses. An x-ray survey of 708 employees in a milling operation showed that the majority had normal x-ray patterns, that ten or more years of exposure were nec essary to produce x-ray changes, and that no cases of asbestosis were found who had worked less than 20 years in the dust. The incidence and duration of nonoccupational respiratory disease were not increased by exposure. Asbestos does not predispose to tuberculosis, nor does it aggravate an apparently healed lesion. There are several reasons for different opinions expressed concerning the relationship of asbestosis and bronchogenic carcinoma. Differences in asbestos fibers were noted. -- Cond. from author's summary j240 The Effects of Inhaled Talc-Mining Dust on the Human Lung. G. W. H. Schepers and T. M. Durkan. Arch. Ind. Health 12, 182-197 (Aug. 1955). The talc mined in Northern New York State consists of a mix ture of talc, tremolite, and anthophyllite. Quartz is also present in moderate amounts in the dust generated in mining and processing. The three constituents of the talc were present in the lungs of deceased em ployees. Quartz was present in significant amounts only when the men had been additionally exposed in other mining industries. The histolog ical features suggest that tremolite may be the main pathogenic agent in provoking the characteristic "talc" lung lesion. The roles of talc and of anthophyllite have not been wholly excluded. The presence of quartz modifies materially the nature of the "talc" reaction, and the presence of "talc" dust in the lungs modifies both the response to quartz dust and the course of associated infection. Marked pulmonary vascu lar damage was present in cases where the quartz content of the lungs was highest, and this feature is in harmony with the tendency to cardiac deaths. Bronchitis, bronchiolitis obliterans, and bronchioiectasis are associated major findings in this series. -- Cond. from authors' summary 1241 Disabling Pneumoconiosis from Limestone Dust. Ind. Med. _12, 206-216 (July 1955). A. T. Doig. Brit. J. Attention is drawn to the occurrence of cases of pneumoconiosis in limestone workers. This pneumoconiosis is associated with fibrosis of the lungs and, in advanced cases, with disability. The lesion produced is almost certainly silicosis, due to the free silica content of the lime stone. The pneumoconiosis hazard, in the mining and grinding of at least certain limestones, is considerable, in spite of the relatively low free silica content. Whether or not calcium carbonate can modify the action of silica, it would not apparently, judging from these observations, ha^ any inhibitory effect. -- Author's summary IHF-560