IN VITRO MEASUREMENT OF FIBER DISSOLUTION RATE RELEVANT TO BIOPERSISTENCE AT NEUTRAL pH: AN INTERLABORATORY ROUND ROBIN

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Abstract
Measurements are presented of the dissolution rates in neutral pH simulated lung (SLF) of several man-made vitreous fibers (MMVF) and crocidolite asbestos that were recently in chronic rodent inhalation studies. The measured dissolution rate depended strongly on the fiber composition. The MMVF tested dissolved from 30 times to nearly 1000 times faster than the crocidolite asbestos. Measurements were made in flow-through equipment in four different laboratories in North America and Europe. The standard deviations of the measured values for each fiber were typically between 30 and 50% of average value. It is believed that in order to be relevant to the dissolution of long fibers the extracellular fluid of the lung, the in vitro measurement must be performed at a rate high enough that corrosion products do not accumulate in sufficient concentration affect the dissolution rate.