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

Measurements are presented of the dissolution rates in neutral pH simu lated lung fluid (SLF) of several man-made vitreous fibers (MMVF) and crocidolite asbestos that were used recently in chronic rodent inhalat ion studies. The measured dissolution rate depended strongly on the fi ber composition. The MMVF tested dissolved from 30 timer; to nearly 10 00 times faster than the crocidolite asbestos. Measurements were made in flow-through equipment in four different laboratories in North Amer ica and Europe. The standard deviations of the measured values for eac h fiber were typically between 30 and 50% of the average value. It is believed that in order to be relevant to the dissolution of long fiber s in the extracellular fluid of the lung, the in vitro measurement mus t be performed at a flow rate high enough that corrosion products do n ot accumulate in sufficient concentration to affect the dissolution ra te.