Dissolution and biodurability of mineral fibres

Dissolution rates of mineral fibres in several environments are obtained as proxies for their biodurability in body fluids. This chapter provides a description of the experimental methods, the parameters and characteristics to be fixed during the design of dissolution experiments in closed (batch reactors) and open systems (flow-through cells), as well as details of the dissolution media. The dissolution of mineral fibres in buffered inorganic solutions is the key to understanding their behaviour during weathering processes because it contributes not only to their chemical transformation, but also to the breakdown of the fibres that may be dispersed in the environment. On the other hand, preparation of fluids representing different interstitial conditions in the lung is described, with particular attention to artificial lysosomal fluid (ALF) employed to mimic the environment that inhaled particles would encounter after phagocytosis by alveolar and interstitial macrophages. Moreover, the use of a neutral fluid such as Gamble’s solution (GS) simulates the interstitial lung fluid and airway lining fluid. Finally, the results of studies of mineral fibre dissolution in inorganic and body fluids, found in the literature, are discussed. Methodologies for assessing the biodurability of fibres are illustrated, starting from dissolution rate data and focus on in vitro studies. Rate constants are used to assess fibre lifetimes utilizing a fibre-shrinking model equation. Finally, literature studies show differences in biopersistence between serpentine and amphibole asbestos, due to their different crystal structures and dissolution conditions of pH and solution composition.