Chronic Inhalation of Short Asbestos Fibers

Chronic Inhalation of Short Asbestos Fibers. PLATEK, S. F.,GROTH, D. H., ULRICH, C. E., STETTLER, L. E., FINNELL, M. S.,AND STOLL, M. (1985). Fundam. Appl. Toxicol. 5, 327–340.An animal inhalation study was initiated to study the chronicbiological effects of inhalation of short chrysotile asbestosfibers. Rats and monkeys were exposed for 18 months, 7 hr/day,5 days/week to a specially prepared, chrysotile asbestos aerosol.Based upon daily chamber measurements, the mean concentrationof fibers in the chamber air was 1.0 mg/m³. By phase contrastmicroscopy, the number of fibers > 5 µm in length wasdetermined to be 0.79 fiber per cubic centimeter. Rats wereautopsied for pathological and histochemical examination at1, 3, 6, 12, 18, and 24 months after initiating exposures. Nosignificnt differences in the histochemical data were seen betweenthe exposed and control groups. Gross and histopathologic examinationof exposed and control groups of rats indicated no compound-relatedlesions, including fibrosis. Open lung biopsies were performedon the chrysotile-exposed and the control monkeys 28 monthsafter initiating exposures. Histopathologic evaluation of thelung biopsy tissue showed the presence of asbestos bodies adjacentto the terminal bronchioles of the asbestos-exposed monkeys.There was no observed fibrosis in pulmonary tissue. All monkeysare being maintained for an indefinite period and observed forsigns of latent pulmonary disease.