Characterization of Asbestos Bodies and Uncoated Fibers in Lungs of Hamsters

Abstract

Dimensional changes of asbestos bodies and uncoated fibers and the leaching of magnesium from the surface of chrysotile after a single intratracheal injection (1 mg) were investigated in male hamsters. The animals were sacrificed at 1 day, 6 months, 1 and 2 years later. In addition to histopathological observation, asbestos tissue burdens were investigated in 25 microns thick sections of the lungs. The sections were ashed in a low-temperature asher to be extracted with carbon film. The carbon extracted ashed sections were investigated by high resolution analytical electron microscopy to characterize asbestos fibers and asbestos bodies. Pulmonary interstitial and pleural fibrosis were observed after 6 months and later on. Light microscopically, asbestos bodies were observed after 6 months; their incidence subsequently increased with the lapse of time after the injection. Asbestos bodies measured on light micrographs became longer with the lapse of time. This suggested that the coating of chrysotile fibers had been continuously progressing in the lung. Geometric means of length and width of uncoated chrysotile fibers seen by transmission electron microscopy in animals at 1 year (length: 1.4 microns; width: 0.057 micron) or 2 years (1.2 microns, 0.047 micron) were greater compared with those of animals at 1 day (0.9 micron, 0.041 micron) or 6 months (0.9 micron, 0.037 micron) after instillation. These findings suggested that short and thin chrysotile fibers were cleared from the…