Surface chemistry and biological pathogenicity of silicates: an X-ray photoelectron spectroscopic study.

We extend our electron spectroscopy for chemical analysis studies of the chemistry of silicates to provide direct surface chemical information on the interactions involved in silicate-induced lung and tissue pathology. A total of five fibrous and non-fibrous silicate minerals, primarily amphiboles, have been studied: anthophyllite, tremolite, cummingtonite, hornblende and actinolite. We have followed the 'inlattice' surface chemistry of these materials and monitored features such as the simultaneous presence of four- and six-coordinate (with respect to oxygen) structural aluminium, and the presence of iron in the M4 octahedral positions. In vitro experiments involving contact of the silicate with cultured murine Ehrlich cells have identified modifications in the surface chemistry of Al, Mg and Fe in the silicates and changes in cellular iron content.