Symptoms and pulmonary functions as measures of morbidity.

A contemporary list of non-malignant respiratory conditions associated with exposure to environments contaminated by chrysotile asbestos dust includes pulmonary parenchymal and pleural fibrosis, small airway abnormality and conditions affecting the large airways such as chronic bronchitis and chronic airflow limitation. The first two are attributed to the specific biological effects of asbestos dust, the latter two to nonspecific effects of exposure to mineral dusts and/or other airborne pollutants in workplaces contaminated by asbestos dust. Prevalence rates for all the clinical markers of morbidity (radiographic change, lung function deficit and symptoms) have been shown to increase with increasing exposure to chrysotile but more steeply when exposure is in textile and other manufacturing plants than in mining and milling. The presence of amphiboles such as tremolite in the airborne dust may also result in steeper exposure-response relationships, while exposure in crocidolite mining results in very much steeper exposure-response relationships. Clinical asbestosis, though less frequent and less severe than previously, is still associated with increased moribidity, while localized pleural fibrosis in the form of plaques with minimal or no parenchymal fibrosis, currently the most frequently encountered non-malignant asbestos related condition encountered in clinical practice, may also be associated with morbidity, including lung function deficit. Determinants of progression of chrysotile-related parenchymal and pleural radiographic abnormality include duration and time since first exposure and, possibly, continued exposure after first appearance of radiographic changes. Progression of asbestos-related airway disease, documented as lung function loss over time, may, under the influence of continued exposure, be comparable to the progression observed under the influence of continued smoking.