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The data on airborne dust and occupational disease in the main dust-related industries of the People's Republic of Bulgaria are generalized and analyzed for a period of 15 years. In the ore producing industry is established a stability in the concentration of total and respirable dust 1-2 TWA concentrations and decrease of silica content in dust. The highest occupational hazard is registered in diggers. The levels of TWA total and respirable dust and silica concentrations in the other underground mines as well as in the overground industries are strongly variable and high. Silicosis is still in the first place among dust-related diseases, but mainly among miners of advanced age. The newly detected other pneumoconiosis, asbestosis, mixed pneumoconiosis are already more than the cases of silicotuberculosis. An essential part is taken by the newly detected diffusive pneumosclerosis and dust bronchitis. The distribution of the newly detected occupational lung diseases is studied according to branches of industry.

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One of the characteristic biological effects of the inhaled asbestos dust is the formation of hyaline thickenings on all pleurae in the form of plaques, in which calcium could be deposited. Due to the difficulties in the differentiation of the pleural hyalinosis with the conventional X-ray methods, the authors studied the potentialities of echography in 18 patients in contact with asbestos. They used two apparatuses (type "grey scale" 3401 of the firm (Brüel & Kjaër with linear scanning and "Siam" with sector scanning). Echography could establish areas of thickening on the parietal and diaphragmatic pleurae, to determine their thickness in micron and the degree of echogenicity. The comparison with the X-ray examination of the chest (face and I oblique position, lowvoltage technique) showed a positive finding with both methods in 7, suspicious X-ray finding with positive echography--in I, positive finding only with echography--in 6 and negative by both methods--in 4 subjects. The echographic examination on pleura is a rapid, cheap and harmless method, contributing not only to the early detection of its asbestosis lesions but to the elucidation of the etiology of pulmonary fibrosis.

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Dustiness in the asbestos-cement production department of the "Vulkan" plant in Dimitrovgrad was studied. The assay included concentration, dispersion, substance composition, morphology, asbestos content. Two types dustiness were encountered: In the storage and mixing shops the aerosol contained 7 to 78 percent asbestos needles, free from agglomeration; in the moulding and turnery shops the asbestos content rangeal from 2 to 21 percent. Considerable part of the needles were amalgamated by the cement and could be detected only on electron-microscopic observation. The total amount of inhaled asbestos exceeded the amount inhaled at threshold concentration of 0.2 mg pure asbestos aerosol 9 times in the preparatory division and from 2 to 14 times in other shops. In the moulding shop the content was lower than the threshold one. Elevel cases of asbestosis were established: 3 in the preparatory, 4 in the turnery and 3 in other shops. In five cases there were pleural plaques in addition to the parenchymal changes. The minimal length of service to develop asbestosis was 13-14 years at the preparatory division (more free asbestos in the aerosol) and 20-21 years at the turnery shop (less, but agglomerated asbestos). Work with asbestos-cement exposes the workers to a serious risk of development of asbestosis. No principal difference was established in the biologic activity of the two aerosol types; there only is a difference in the degree of their aggressiveness.

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Detailed investigations of the environment in asbestostextile industry ("Asbestos produce" plant in the town of Sevlievo) were carried out. The parameters determined were: overall dusting, amount of asbestos in aerosol, its mineral and disperse composition. Data on the degree of dusting in the plant for the period 1960--1976 were analyzed and summarized. Professiograms were elaborated, with chronometry and appraisal of the burden of the work operations. All workers were tested clinically and roentgenologically. The data obtained on the degree of dusting in the different departments were re-calculated as amount of inhaled asbestos, depending on how hard the work is, resp. the pulmonary ventilation. The actual risk of asbestos injury was highest in the carding department, followed by the preparatory and the spinning departments. A distinct correlation exists between the degree of professional risk, determined by the asbestos contaminations, and the clinical and laboratory findings.

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Diagnostics of intrathoracic sarcoidosis in people with an occupational injury or an annoyance of respiratory organs are frequently connected with additional difficulties. The first roentgenological manifestations of a silicosis caused during the period of dry drilling especially in ore metal mining, are frequently bilaterally increased shadows of the hilum without any worth mentioning findings in the parenchyma. The radiograph of diffuse restiform and speckled shadows in people exposed to dust without a sufficient load or in younger age always demands a search for sarcoidosis. Granulomatoses of the lungs caused by organic dusts, berillium and other things may develop difficulties not only in the interpretation of clinical data but also in the bioptic findings for instance after an endoscopic antalgic biopsy of the bronchomucosa. The authors summarize their experiences with the application of bioptic methods (skin biopsy, according to the Kveim-test, scalenobiopsy, explorative thoracotomy) in workers suspected to suffer from a sarcoidosis, who--as to their profession--had been influenced by noxious substances in respect to their lungs. Two typical cases are briefly discussed. The signification of the synopsis of clinico roentgenological, industriohygienical and bioptical data is stressed especially in case of a suspicion on the combination of pneumoconiosis and sarcoidosis.

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Lung dusts were investigated, post-mortem, in twenty-five miners from mixed metal mines, tunnels, and quarries who had exposed to high concentrations of mixed dust containing about 20-25% free crystalline silica. The character of the relations found between the amount of quartz per 100 g dry tissue and the clinical, X-ray and pathological findings is similar to that established in coal miners. The difference lies in the fact that with equal amounts of quartz per 100 g dry tissue, there is less silicosis in coal miners than in our cases; the average residence time of retained dust is longer in coal miners, but its quartz per cent is lower.

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