BIOPERSISTENCE OF MAN-MADE VITREOUS FIBERS

Methods for the determination of biodurability of man-made vitreous fi bres are reviewed. For mineral wools the first step was the preparatio n of respirable fibre fractions. Fibres were administered to rats by i nhalation or by intratracheal instillation. After serial sacrifice the ir lungs were digested by low-temperature ashing or by hypochlorite. T he total number of fibres per lung and the distributions of length and diameter were analysed by electron microscopy. This resulted in a biv ariate distribution of fibres at the various sacrifice dates. If the l ogarithm of the number of fibres decreased approximately linearly with time after exposure then the elimination kinetics of fibres can be ch aracterized by a half-time. The half-times were compared between vario us experiments with rats exposed to mineral wool samples. In summary g ood agreement was found for the elimination of fibres after long-term inhalation and intratracheal instillation whereas shorter half-times w ere found after short-term inhalation.