The epidemiology and clinical features of asbestosis and related diseases

Abstract

Pulmonary fibrosis due to exposure to asbestos dust in factory workers has become uncommon and when it occurs is less severe than it was before the introduction of dust suppression measures in 1932 - 33. However there remain occupations which were not covered by the Merewether report which can cause sufficiently severe fibrosis to lead to death before the retiring age. Insulation workers are a group in which this is likely to occur but the spreading use of asbestos in the building industry may be leading to similar levels of exposure among occupational groups where this hazard has not existed before. An increase in the number of such cases can only be prevented by constant vigilance on the part of the medical profession in identifying this as a cause of diffuse pulmonary fibrosis in individual cases and bringing them to the notice of the factory inspectorate. One of the difficulties here is the lack of clinical features to distinguish asbestosis from other forms of diffuse fibrosis. When the source of exposure is not obvious open biopsy of the lung may be necessary to establish the cause and initiate investigation for sources of exposure. Carcinoma of the lung resulting from exposure to asbestos appears to be common in patients whose exposure to the dust was insufficiently long or intense to cause crippling fibrosis. There is evidence that the risk may have been eliminated by the application of thorough dust suppression under factory conditions. But there may be many other workers handling asbestos who are still at risk as has been shown for insulation workers. The nature, age of onset and course of cancer of the lung secondary to asbestos exposure does not appear to differ greatly from cases arising in the general population. A rapidly increasing number of cases of mesothelioma of the pleura and peritoneum have been recognised in the last 10 years. It is an invariably fatal tumour for which there is no satisfactory paliative treatment. There is an association between exposure to asbestos and the development of this tumour. The degree of exposure in many cases is slight and indicates that many people may by now have had sufficient exposure either in the course of their work, hobbies or in the home. As there is no evidence of another factor operating in the initiation of this tumour it seems likely that increasing numbers of cases will arise in the next 30 years. Prevention of further cases beyond that date depends on the restriction of use and greater precautions in the handling of all types of asbestos fibre now. It is possible that the elimination of one type of fibre (crocidolite) from commercial use might reduce the incidence of the tumour very considerably.