Effects of Asbestos in the Human Respiratory Tract

Taylor, Reginald George William (1984). Effects of Asbestos in the Human Respiratory Tract. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f7ea

Abstract

The aims of this investigation were to study differences in the protein composition and cellular content of the sputum from workers in an asbestos textile factory and also to reconstruct the sequence of events that occurs when inhaled chrysotile is retained in the human respiratory tract. The mean value of total protein in the sputum from workers exposed to chrysotile without asbestosis was lower than that from workers in the unexposed and the asbestotic groups. Within the group 'exposed without asbestosis' sputum total protein was correlated with all electrophoretic fractions except beta/gamma globulin whereas within the group 'exposed with asbestosis' sputum protein levels were correlated only with beta/gamma globulin. Immunoanalysis showed increased transferrin in sputa from exposed donors but no specific marker protein for asbestosis was found. A non-serous, PAS reacting protein with beta^ electromobility was isolated by cation exchange separation from all sputa examined.

Cytological analysis showed that half of the exposed donors possessed Type 1 pneumocytes in their sputa; Type 2 pneumocytes and iron-containing histiocytes were also found but with lower frequency. Histiocytes with endocytosed chrysotile or asbestos bodies were found only in sputa from asbestotic donors and extracellular asbestos bodies were found five times more frequently in these sputa than in those from exposed donors without asbestosis. None of these findings were seen in sputa from unexposed donors. A negligible amount of water was taken up by chrysotile from wet air at 37°C during the inhalation period, 1.74 seconds, but when chrysotile was immersed in sputum, water uptake proceeded protein adsorption. About 45 mg protein/g chrysotile was taken up in the proportion 1:1:3:1 of albumin: alpha globulin: beta/gamma globulin: lysozyme independent of sputum protein concentration and about two thirds of all adsorbed protein was PAS positive protein. When chrysotile was coated with sputum protein, its cytolytic property was markedly attenuated and viable histiocytes were still present after 25 hours exposure to the coated fibre.

The results indicate that some part of retained chrysotile reaches the lung alveoli causing loss of alveolar epithelial cells although in exposed persons without asbestosis the capillary endothelium probably remains intact.

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