DURABILITY OF MAN-MADE VITREOUS FIBERS AS ASSESSED BY DISSOLUTION OF SILICON, IRON AND ALUMINUM IN RAT ALVEOLAR MACROPHAGES

The dissolution of man-made vitreous fibres (MMVF) by rat alveolar mac rophages (AM) was studied in vitro. The fibre samples included refract ory ceramic (RCF 1-4), glasswool (MMVF 10, 11), rockwool (MMVF 21) and slagwool fibres (MMVF 22). Experimental fibre REC 1 of calcium silica te type served as an internal control fibre. The fibres were incubated with cultured rat AM or in mere cell-culture medium for 2, 4 or 8 day s. The dissolution of the fibres was determined by measuring the amoun t of silicon (Si), iron (Fe) and aluminium (Al) in the medium with or without rat AM. Si was markedly dissolved only from the glasswool fibr es (MMVF 10 and 11) and from the experimental fibre REC 1. Fe was diss olved, in turn, more from rockwool fibres than from the other fibres. Al was effectively dissolved from the ceramic fibres (RCF) 1-3. The di ssolution of Fe and Al from the fibres was effective in the presence o f AM, whereas the dissolution of Si was greater in the mere culture me dium. The results of present study suggest that glasswool fibres (MMVF 10 and 11) are dissolved more readily in mere culture medium where th e pH is close to neutral, whereas rockwool fibres are sensitive to the effects of more acidic milieu in AM culture.