Some Peculiarities of the Organism’s Responses to a Long-Term Inhalation of Silica-Containing Submicron (Predominantly, Nanoscale) Particles in a Real Industrial Aerosol

Female white rats were exposed in a «nose only» inhalation device to an aerosol containing predominantly submicron (nanoscale included) particles of amorphous silica in a total concentration of 2.6±0.6 or 10.6±2.1 mg/m3, 4 h/day, 5 times a week, during up to 6 months. In an auxiliary experiment with a single-shot intratracheal instillation of these particles, it was shown that they induced a pulmonary cell response comparable with that when administrated a highly cytotoxic and fibrogenic standard quartz dust DQ12. However in a long-term inhalation test, the aerosol investigated proved to be of a very low systemic toxicity and fibrogenicity. This paradox may be explained by a low retention of SiO2 in lungs and other organs due to a relatively high in vivo solubility of those nanoparticles. Nevertheless their genotoxic action and transnasal penetration into the brain urge caution when assessing occupational or environmental hazard of that aerosol.