Lung-Retained Fibre Content in Brazilian Chrysotile Workers

Abstract

Introduction. Beginning with observations in Quebec in 1976, the study of lung-retained fibre has led to an increased understanding of exposure and disease in chrysotile mining areas. Until 2000 this was confined largely to Quebec, but recent work has outlined exposure profiles for lung content in Russian, Chinese and South African chrysotile production and factory workers. We now report the first findings from Brazilian chrysotile production and asbestos cement workers with well characterized clinical, exposure and smoking histories. Methods. Subjects working either in the chrysotile mining industry in Brazil (n = 6) or in the asbestos cement industry (n = 4) were admitted to hospital for investigation of pulmonary lesions. Six had benign infections and four lung cancer, while two also had pleural plaques (both miners) and one cement worker had asbestosis. Portions of formalin-fixed lung tissue obtained at surgery or autopsy were obtained for analysis. Asbestos bodies (AB) were quantified following bleach digestion using phase contrast optical microscopy at ×312. Additional portions were examined using transmission electron microscopy at ×14000. Seven hundred and four fibres (aspect ratio > 3:1) were identified and quantified by X-ray energy dispersive spectrometry in three length classes, 20 µm, each at a theoretical detection limit of 0.1 fibres/µg dry lung. Results. AB counts confirmed occupational exposure as proportional to years of exposure (r = 0.72, P 90% of asbestos fibres in all length classes (median 98% of all asbestos fibres; median 4.99 fibres/µg chrysotile versus 0.11 for amphiboles; P 5 µm in one who worked in a nowabandoned mine known to contain that mineral.