asbestos--crocidolite and Pneumoconiosis

Topics: Adsorption; Animals; Asbestos; Asbestos, Crocidolite; Asbestos, Serpentine; Catalysis; Chelating Agents; Chemical Phenomena; Chemistry, Physical; Cricetinae; Crystallization; Dust; Erythrocytes; Free Radicals; Guinea Pigs; Iron; Lipid Peroxidation; Lung; Macrophages, Alveolar; Mineral Fibers; Minerals; Nitric Oxide; Phagocytosis; Pneumoconiosis; Quartz; Rabbits; Rats; Reactive Oxygen Species; Reducing Agents; Silicon Dioxide; Surface Properties

Topics: Aerosols; Air Pollutants; Animals; Asbestos; Asbestos, Crocidolite; Asbestos, Serpentine; Asbestosis; Carbon; Chemotactic Factors; Electron Probe Microanalysis; Glass; Lung; Macrophages; Mice; Microscopy, Electron, Scanning; Minerals; Phagocytosis; Pneumoconiosis; Quartz; Rats

The different pulmonary macrophage (airway macrophages, alveolar macrophages, interstitial macrophages, intravascular macrophages, pleural macrophages) are an important part of the lungs' defences against non-fibrous and fibrous particles deposited by inhalation. The first line of defence is airway macrophages and alveolar macrophages (AM) which initially interact with deposited chrysotile fibres and subsequently release a number of mediators including growth regulatory and chemotactic proteins, arachidonic acid metabolites, proteases, NO and active oxygen species, all of which can affect--also adversely--specific target cells in the lung. Mechanical clearance via the mucociliary escalator and dissolution of phagocytized fibres in the acidic milieu of the phagolysosome in pulmonary macrophages are further important functions of AM. Chrysotile appears to be more toxic or at least has the same toxicity to AM as amphibole fibres when doses of a similar mass are administered. However, on a fibre number basis chrysotile appears to be less toxic to AM. The importance of the appropriate dose parameter--i.e. fibre mass, number or surface area--needs to be considered in in vitro as well as in in vivo studies. Short chrysotile fibres are cleared from rat lungs very rapidly whereas longer ones are cleared at a much slower rate. This is due to efficient phagocytosis of short fibres by AM accompanied by dissolution in the acidic milieu of the phagolysosome. Prediction of chrysotile clearance in primate lung based on results from rat studies result in an overall retention half-time of approximately 105 days, based on which no long-term accumulation of chrysotile in the primate lung is to be expected. Long-term inhalation studies in baboons exposed to chrysotile confirm the very fast build up of a low steady-state lung burden, consistent with a pulmonary retention half-time for chrysotile of approximately 90 days. Despite the fast clearance and low pulmonary accumulation of chrysotile, the resulting effects, such as asbestosis, were found to be of the same severity in rats as those induced by amphibole exposure. In the amphibole-exposed rats, the fibre lung burden continued to increase with exposure time. The potential contamination of chrysotile with tremolite cannot explain these results since there was no increased pulmonary accumulation of fibres in the chrysotile-exposed rats. Effects due to lung particle overload are not to be expected in long-term chrysotile inha

Topics: Animals; Asbestos, Amosite; Asbestos, Crocidolite; Asbestos, Serpentine; Asbestosis; Coal Mining; Cytokines; Dogs; Dust; Humans; Lung; Lymph; Macrophages, Alveolar; Papio; Pneumoconiosis; Quartz; Rats; Silicosis; Time Factors

Cytology and histology material from 46 bronchogenic carcinomas occurring in ex-workers from the Wittenoom crocidolite mine and mill in Western Australia and a matched random sample of 234 other bronchogenic carcinomas occurring in Western Australia over the same period were reviewed by a single histopathologist without knowledge of asbestos exposure status. Squamous-cell carcinomas formed 45.7% of the cancers in the asbestos-exposed group but only 32.5% of the cancers in the comparison group. This difference could not be explained by differences in smoking history between the two groups of lung cancer patients or in the type of histopathological material available for review. The excess of squamous-cell cancers was observed in subjects both with and without parenchymal asbestosis.

Topics: Adult; Aged; Asbestos; Asbestos, Crocidolite; Australia; Carcinoma, Bronchogenic; Carcinoma, Squamous Cell; Humans; Lung Neoplasms; Male; Middle Aged; Mining; Occupational Diseases; Pneumoconiosis; Regression Analysis; Smoking

The course of pulmonary asbestosis and its determinants have been examined in 280 applicants for compensation among former workers of the crocidolite mine and mill at Wittenoom Gorge, Western Australia. Serial chest radiographs accrued over more than 3 decades were graded for parenchymal disease separately by two observers according to the 1980 ILO Classification of Radiographs for Pneumoconioses and without knowledge of exposure histories or compensation details. In 136 subjects whose median duration of exposure was 37 months, radiographic asbestosis appeared between 1 and 34 yr after initial exposure and then progressed continuously. Total exposure to asbestos and time from first exposure to the appearance of definite radiographic asbestosis were significant determinants of the rate of progression of profusion of radiographic abnormality. Asbestosis should be considered to be an active disease even 3 decades after exposure has ended.

Topics: Adult; Asbestos; Asbestos, Crocidolite; Asbestosis; Australia; Humans; Male; Mining; Models, Theoretical; Pneumoconiosis; Radiography; Retrospective Studies; Severity of Illness Index; Time Factors

The pleura is a main target for various reactions related to asbestos exposure. However there are great radiological and clinical differences between the various reactions, and there is also increasing evidence that they have different prognoses. The main reactions are pleural plaques on the one hand and acute pleurisy and diffuse pleural fibrosis on the other. In a population with a low mesothelioma risk, the anthophyllite-exposed population of Northern Karelia in Finland, there are very few reactions of the second type, while plaques are very common. In Turkey, where the exposure is to erionite, the mesothelioma level is extremely high, and reactions of type two are very common in the exposed population. Thus it seems that careful discrimination of the various pleural changes can have prognostic value. There are also indications that plaques do not have any relation to a disturbed immunologic system, while pleurisy and diffuse pleurisy have.

Topics: Aluminum Silicates; Asbestos; Asbestos, Crocidolite; Asbestosis; Finland; Humans; Mesothelioma; Pleural Diseases; Pleural Neoplasms; Pneumoconiosis; Radiography; Risk; Sweden; Turkey; Zeolites

Epidemiological studies have not revealed any significant health hazards from exposure to fibrous glass and animal experiments have been inconclusive. Baboons exposed to a fibrous-glass dust cloud with size features similar to those of crocidolite asbestos developed focal peribronchiolar fibrosis with scant ferruginous body formation. The lesions were similar to those produced by crocidolite but were less extensive. No neoplasms occurred.

Topics: Animals; Asbestos; Asbestos, Crocidolite; Dust; Glass; Lung; Male; Papio; Pneumoconiosis; Respiration