Lung Burden of a Glass Fiber By Inhalation

Abstract

Pulmonary deposition and clearance of deposited particles from lungs are very important factors in order to induce pneumoconioses.

In this paper, five Wistar male rats were exposed to glass fiber particles( mass median aerodynamic diameter(MMAD), 2.8 μm) for 6 hrs/day, 5 days/week for 4 weeks. The average expo sure concentration was controlled by a continuous fluidized bed with a screw feeder and an overflow pipe at 0.79 mg/m during the exposure period. The fibrous particles concentra tions in the exposure chamber were monitored by a light scat tering method and showed to be constant during the exposure.

The rats were sacrificed at 24 hours after the termina tion of the exposure and then the wet lung weight and the silica concentration in the lungs were measured. The lungs were treated for low temperature ashing (ca. 150 °C) by a plasma asher. After ashing, these samples were melted with sodium carbonate in platinum pot for the measurement of the silica content by the absorption spectrophptometry.

The maximum content of SiO₂ was 45 μg in the exposed rats and 20 μg in the control, The deposited amount of SiO₂ by the exposure to glass fiber was 25 μg. The apparent deposition fraction defined as the deposited amount in the lungs to the amount of the inhaled glass fiber during the exposure was 6.8 %. There was no significant difference of the apparent deposi tion fraction at same MMAD between glass fiber in this study and non-fibrous particles.