The effect of fiber length on the dissolution by macrophages of rockwool and glasswool fibers

Abstract

The effect of fiber length on the dissolution of experimental rockwool and commercial glasswood fibers in rat alveolar macrophage (AM) culture and in mere culture medium was studied. The ultrastructure of macrophages after their exposure to fibers and the suitability of macrophage-type cell line P388D1 culture in dissolution studies were also explored. The fiber samples included short (ground) and long (untreated) rockwool and glasswool fibers. The fibers were incubated in rat AM cultures, in P388D1 culture, or in mere culture medium for 4 or 8 days. The dissolution of the fibers was determined by measuring the amounts of silicon (Si), iron (Fe), and aluminum (Al) in the medium. There were no differences in the diameter of the fibers, but a clear difference existed in the length of the short and long fibers. The dissolution of Si, Fe, and Al was more pronounced from experimental rockwool than from commercial glasswool fibers. The dissolution of Si was always greater in mere culture medium than in rat AM culture. Moreover, the dissolution of Si was greater from the long fibers than from the short ones. On the contrary, the dissolution of Fe and Al in AM culture exceeded that in mere culture medium. The dissolution of Si, Fe, and Al from both fibers in P388D1 culture was similar to their dissolution in rat AM culture. The fibers were also effectively phagocytized by the macrophages. The present results together suggest that the intracellular and the extracellular dissolutions of man-made vitreous fibers differ from each other.