The methods of thermally stimulated luminescence (t.s.l), thermally stimulated exoelectron emission (t.s.e.e.), electron spin resonance (e.s.r), and infrared spectroscopy (i.r.) have been used to investigate whether the specific cytotoxic activities of SiO2 dust of various origins can be attributed to physical parameters. After interaction of toxic dusts with water an increase in the intensity of the t.s.l. peaks below room temperature has been detected whereas no effect could be observed in the case of inert materials. Dusts of weak cytotoxicity have been characterized by infrared absorption bands at 3610 cm-1 and 3685 cm-1. The results of the present studies emphasize the significance of silanol groups and adsorption properties in relation to the fibrogenic activity of quartz dusts.