Asbestos is a mixture of silicates of iron, magnesium, nickel, cadmium and aluminium, and has the unique property of occurring naturally as a fibre. It is remarkably resistant to heat, acid and alkali, and has been widely used for roofing, insulation and fireproofing. Asbestos has been mined in southern Africa , Canada and eastern Europe. Several different types of asbestos are recognized: about 90% of asbestos is chrysotile, 6% crocidolite and 4% amosite.
Chrysotile or white asbestos is the softest asbestos fibre. Each fibre is often as long as 2 cm but only a few microns thick. It is less fibrogenic than crocidolite. Crocidolite (blue asbestos) is particularly resistant to chemical destruction and exists in straight fibres up to 50 mm in length and 1-2 µm in width. Crocidolite is the most likely type of asbestos to produce asbestosis and mesothelioma. This may be due to the fact that it is readily trapped in the lung. Its long, thin shape means that it can be inhaled, but subsequent rotation against the long axis of the smaller airways, particularly in turbulent airflow during expiration, causes the fibres to impact. Crocidolite is also particularly resistant to macrophage and neutrophil enzymatic destruction. Read more>>
Except in localized regions with single industrial exposures, such as coal-mining or granite-quarrying regions, the most frequent inorganic dust-related chronic pulmonary diseases are associated with industries using asbestiform fibers. Asbestos is a generic term for several different mineral silicates, including chrysolite, amosite, anthophyllite, and crocidolite. Besides workers involved in the mining, milling, and manufacturing of asbestos products, workers in the building trades, including pipe fitters and boilermakers, were exposed to asbestos, which was widely used in construction because of its exceptional thermal and electric insulation properties. In addition, asbestos was used in the manufacture of fire-smothering blankets and safety garments, as filler for plastic materials, in cement and floor tiles, and in friction materials, such as brake and clutch linings.
Asbestosis is a diffuse interstitial fibrosing disease of the lung that is directly related to the intensity and duration of exposure. Except for its association with a history of exposure to asbestos (generally in a work setting), asbestosis resembles the other forms of diffuse interstitial fibrosis.
Exposure to asbestos occurred particularly in shipbuilding yards and in power stations, but its ubiquitous use meant that low levels of exposure were common. Up to 50% of urban dwellers have been found to have evidence of asbestos bodies (asbestos fibre covered in protein secretions) in their lungs at post-mortem. Regulations in the UK prevent the use of crocidolite and severely restrict the use of chrysotile. Careful dust control measures are enforced, which should eventually abolish the problem. Workers continue to be exposed to blue asbestos in the course of demolition or in the replacement of insulation, and it should be remembered that there is a considerable time lag between exposure and development of the disease, particularly mesothelioma (20-40 years).
A synergistic relationship between asbestosis and cigarette smoking and the development of bronchial carcinoma, usually adenocarcinoma, exists; the risk is multiplied fivefold above the risk attributable to smoking. The risk of lung cancer is also increased in non-smokers, especially in those who have parenchymal asbestosis but also in those with pleural plaques without parenchymal fibrosis.
The diseases caused by asbestos are summarized in tabular form. Bilateral diffuse pleural thickening, asbestosis, mesothelioma and asbestos-related carcinoma of the bronchus are all eligible for industrial injuries benefit in the UK , but account for only one-quarter of the number of cases of compensation compared with coal-worker's pneumoconiosis.
Asbestosis is defined as fibrosis of the lungs caused by asbestos dust, which may or may not be associated with fibrosis of the parietal or visceral layers of the pleura. It is a progressive disease characterized by breathlessness and accompanied by finger clubbing and bilateral basal end-inspiratory crackles. Fibrosis, not detectable on chest X-ray, may be revealed on CT scan. No treatment is known to alter the progress of the disease, though corticosteroids are often prescribed.
Chrysotile or white asbestos is the softest asbestos fibre. Each fibre is often as long as 2 cm but only a few microns thick. It is less fibrogenic than crocidolite. Crocidolite (blue asbestos) is particularly resistant to chemical destruction and exists in straight fibres up to 50 mm in length and 1-2 µm in width. Crocidolite is the most likely type of asbestos to produce asbestosis and mesothelioma. This may be due to the fact that it is readily trapped in the lung. Its long, thin shape means that it can be inhaled, but subsequent rotation against the long axis of the smaller airways, particularly in turbulent airflow during expiration, causes the fibres to impact. Crocidolite is also particularly resistant to macrophage and neutrophil enzymatic destruction. Read more>>
Except in localized regions with single industrial exposures, such as coal-mining or granite-quarrying regions, the most frequent inorganic dust-related chronic pulmonary diseases are associated with industries using asbestiform fibers. Asbestos is a generic term for several different mineral silicates, including chrysolite, amosite, anthophyllite, and crocidolite. Besides workers involved in the mining, milling, and manufacturing of asbestos products, workers in the building trades, including pipe fitters and boilermakers, were exposed to asbestos, which was widely used in construction because of its exceptional thermal and electric insulation properties. In addition, asbestos was used in the manufacture of fire-smothering blankets and safety garments, as filler for plastic materials, in cement and floor tiles, and in friction materials, such as brake and clutch linings.
Asbestosis is a diffuse interstitial fibrosing disease of the lung that is directly related to the intensity and duration of exposure. Except for its association with a history of exposure to asbestos (generally in a work setting), asbestosis resembles the other forms of diffuse interstitial fibrosis.
Exposure to asbestos occurred particularly in shipbuilding yards and in power stations, but its ubiquitous use meant that low levels of exposure were common. Up to 50% of urban dwellers have been found to have evidence of asbestos bodies (asbestos fibre covered in protein secretions) in their lungs at post-mortem. Regulations in the UK prevent the use of crocidolite and severely restrict the use of chrysotile. Careful dust control measures are enforced, which should eventually abolish the problem. Workers continue to be exposed to blue asbestos in the course of demolition or in the replacement of insulation, and it should be remembered that there is a considerable time lag between exposure and development of the disease, particularly mesothelioma (20-40 years).
A synergistic relationship between asbestosis and cigarette smoking and the development of bronchial carcinoma, usually adenocarcinoma, exists; the risk is multiplied fivefold above the risk attributable to smoking. The risk of lung cancer is also increased in non-smokers, especially in those who have parenchymal asbestosis but also in those with pleural plaques without parenchymal fibrosis.
The diseases caused by asbestos are summarized in tabular form. Bilateral diffuse pleural thickening, asbestosis, mesothelioma and asbestos-related carcinoma of the bronchus are all eligible for industrial injuries benefit in the UK , but account for only one-quarter of the number of cases of compensation compared with coal-worker's pneumoconiosis.
Asbestosis is defined as fibrosis of the lungs caused by asbestos dust, which may or may not be associated with fibrosis of the parietal or visceral layers of the pleura. It is a progressive disease characterized by breathlessness and accompanied by finger clubbing and bilateral basal end-inspiratory crackles. Fibrosis, not detectable on chest X-ray, may be revealed on CT scan. No treatment is known to alter the progress of the disease, though corticosteroids are often prescribed.