Production of free radicals arising from the surface activity of minerals and oxygen. Part II. Arsenides, sulfides, and sulfoarsenides of iron, nickel, and copper.

The excess incidence of lung cancers observed in metallic mines other than iron mines probably can be correlated not only to radioactivity, but also to dust pollution. The present work investigates the role of surface properties of sulfides and arsenides, which are present in metal mines, in oxidizing mechanisms capable of inducing oxidative stress and, possibly, of participating in carcinogenesis. Using added spin-trapping agent followed by ESR spectroscopy, it was observed that nickel and copper arsenides can be very active in the oxidation of formate or DMSO, by reducing the oxygen dissolved in a cell-free medium. Sulfides, on the other hand, are not active, except for the iron sulfides, which are very active as an air-aged powder. The process of activation and rendering the particle surface passive was investigated. Surface dissolution and moderate grinding were found to be activating factors, while air-aging generally rendered the particle surface passive. The critical factor in determining activity is the availability of reducing species of iron, copper, or nickel on the surface of the minerals.