Occupational exposure to dusts containing asbestos and chronic airways disease

Abstract

Chronic inhalation of asbestos fibres has been recognized as a cause of both malignant and non-malignant diseases of lung parenchyma and pleura. The objective of this review was to examine epidemiological evidence concerning this type of occupational exposure as a risk factor for chronic disorders of airways, classified as peripheral airways disease and chronic airflow limitation. A number of published pathophysiological findings that are suggestive of the involvement of peripheral airways in workers exposed to asbestos could be supported by workforce-based assessment of simple tests of small airways function. In asbestos workers the tests' results are usually found to be lower than in reference groups and depend on cumulative exposure. The cross-sectional surveys carried out in large populations of workers exposed to asbestos document an association of both forced expiratory volume in the first second and forced vital capacity with increasing exposure. The majority of the studies reviewed show an exposure-response type of association, also documented by longitudinal studies. The presence of lung function impairment in subjects with normal chest radiographs is compatible with the view that the airway defect may be an independent outcome of exposure to asbestos. The occurrence of the obstructive ventilatory impairment is not infrequent in workforce-based cross-sectional studies, also in nonsmokers in whom the prevalence of obstruction was found to exceed the prevalence of restriction. In conclusion, the review provides evidence that peripheral airways abnormality could be a consequence of inhalation of asbestos. This association seems to be strong and exposure to mineral dust containing asbestos can be therefore regarded as one of the etiologic factors in the genesis of peripheral airways abnormalities. A number of findings favour the plausibility of causal association of chronic airflow limitation with exposure to asbestos dust. However, the insufficient epidemiological data concerning the relationships of an obstructive pattern of ventilatory defect preclude the elaboration of frequent occurrence of obstructive profile in non-smoking asbestos workers. The epidemiologic evidence on association between occupational exposure to dusts containing asbestos and chronic airways disease confirms the presence of "mineral dust airways disease" and adds credibility to the concept of "work-related chronic airflow limitation".