Correlation between in vitro and in vivo dissolution behaviour of stonewools by nonlinear modelling techniques

Toxicology studies have indicated that stone wools with different compositions have different levels of biopersistence. It is however not easy to carry out a large number of in vivo experiments. It is also known that in vitro dissolution rates at two pH values correlate with two dissolution phenomena in lungs. In this work, nonlinear models of in vitro dissolution rates at pH 4.5 and at pH 7.4 have been developed for stone wools of widely different compositions from a limited amount of experimental data. These in vitro dissolution rates, in combination with some other variables, have then been correlated with in vivo retention half times. It is expected that once the models predicting half times are reliable enough, testing on animals could be reduced to a negligible fraction of its amount today. The dissolution rates of stone wools depend on their composition in a complicated manner. Not only are the effects nonlinear, there are strong cross effects of combinations of variables. Therefore, the conventional linear techniques are not effective. Phenomenological modelling is hardly possible since very little is known about the kinetics of the potential surface reactions taking place at different pH values. New techniques of nonlinear modelling have made this kind of model development feasible, as it is illustrated in this paper. These techniques have opened up new possibilities in materials science, including fibre technology and ceramics. (c) 2006 Elsevier Ltd. All rights reserved.