Influence of airspace geometry and surfactant on the retention of man-made vitreous fibers (MMVF 10a)

Inhaled and deposited man-made vitreous fibers (MMVF) 10a (low-fluorine preparation of Schuller 901 insulation glass) were studied by electron microscopy in hamster lungs, fixed by intravascular perfusion within 23 +/- 2 min (SD) of the initial inhalation. We found fibers on the surfaces of conducting airways and alveoli. In the airways, 89% of the fibers were totally and 11% partially covered by lining-layer material. In the alveoli, 32% of the fibers were totally submersed; others touched the alveolar wall, stuck at one end, bridging the airspace. Studies in a surface balance showed that fibers were immersed into the aqueous subphase by approximately 50% at film surface tensions of 20-25 mJ/m2) and were submersed (totally immersed; i.e., totally surrounded by fluid) at approximately 10 mJ/m2). Fibers were also found to be phagocytosed by macrophages. We found a substantial number of particle profiles within alveolar blood capillaries. Fiber length and alveolar geometry appear to be important limiting factors for the submersion of vitreous fibers into the lungs' surface lining layer.