MEASUREMENT OF IN-VITRO FIBER DISSOLUTION RATE AT ACIDIC PH

A low biopersistence of man-made vitreous fibres (MMVFs) has often bee n related to a high in-vitro dissolution rate at near-neutral pH. For some fibre types, however, a low in-vivo biopersistence cannot be expl ained by the in-vitro dissolution rate in near-neutral physiological f luids. It has been suggested, that the high in-vitro dissolution rate of these fibres at the acidic pH which is found inside the phagolysoso mes of the alveolar macrophages could be the reason for the fast in-vi vo clearance of such fibres, The aim of this study was, through interl aboratory comparison of in-vitro dissolution measurements at acidic pH , to investigate the causes of variations and to identify key paramete rs for a measurement method similar to the method used at near neutral pH, Results of in-vitro measurements of different fibre types at acid ic pH are presented, and the influence of different test parameters de scribed, The measurements and calculations at acidic pH can be made si milar to what is done for measurements at near-neutral conditions. Sin ce incongruent dissolution is often very pronounced, it is relevant to calculate two dissolution rates, one for the network represented by s ilicon and one for the leaching elements. In order to obtain comparabl e results it is necessary to use a Liquid which is well-defined with r espect to type and concentration of buffer system, and to compare only values obtained under similar experimental conditions. The measured d issolution rates differ substantially with different liquids and diffe rent experimental conditions, However, the ranking of the different te sted fibres with respect to the dissolution rates remains the same as long as they are tested under identical conditions. (C) 1998 British O ccupational Hygiene Society. Published by Elsevier Science Ltd. All ri ghts reserved.