DEPOSITION EFFICIENCY OF INHALED FIBERS IN THE HAMSTER LUNG

Abstract

Deposition efficiency, a necessary parameter in models of pulmonary deposition and clearance, has not been extensively studied with inhaled fibers. Accurate assessment of pulmonary deposition requires brief exposures with sufficiently high numbers of particles for quantification, and concomitant measurements of pulmonary ventilation. We produced aerosols of fiberglass fibers with mean diameter of 0.98 0.40 (SD) m, length of 17.2 3 14.2 m, airborne mass concentration determined gravimetrically of 5.6 0.9 mg/m, and 6 3 fiber number of 7.3 1.1 x 10 fibers/m. Preliminary studies showed that 10-min exposures were ideal in that they provided adequate numbers of particles without significant clearance. Five hamsters were exposed to the aerosol for 10 min by nose-only exposure, and pulmonary function was measured using plethysmography. Following exposure, the lung and conducting airways were digested by bleach, and deposited fibers were quantified on membrane filters. Deposition efficiency, calculated as the deposited fiber number divided by the inspired fiber number, was 23.2 4.7%. Respiratory rate tended to be inversely proportional to the deposition efficiency. This measured efficiency in hamsters is larger than that in previously reported studies of deposition efficiency using rats or dogs with longer exposure times.