Alteration of Respirable Quartz Particle Cytotoxicity by Thermal Treatment in Aqueous Media.
Wallace-WE; Hill-CA; Keane-MJ; Page-SJ; Bolsaitis-P; Razzaboni-BL; Vallyathan-V; Mike-P
NIOSH 1990 Sep:755-764
The effect of boiling in aqueous media on the cytotoxicity of respirable quartz (14808607) particles was examined. Min-U-Sil quartz dust at concentrations up to 30mg/ml was mixed with deionized water in flint or borosilicate glass or polycarbonate plastic tubes and boiled for 0 to 60 minutes. Cytotoxicity was evaluated by measuring the hemolytic activity of the dust in suspension against sheep erythrocytes. Some samples were allowed to age by drying them at 110 degrees-C and storing them or allowing them to stand for up to 4 days in water at room temperature before testing. Boiling for 60 minutes in glass tubes reduced the cytotoxicity of the dusts at concentrations up to 10mg/ml to near zero. For concentrations above 10mg/ml cytotoxicity increased linearly with concentration. At 20mg/ml the cytotoxicity of the boiled dusts was similar to that of unboiled quartz. Loss of cytotoxicity was not seen in dusts boiled in polycarbonate tubes. Loss of cytotoxicity did not vary significantly with boiling time except at 1mg/ml. Replacing the water with fresh water midway through boiling caused a complete loss of cytotoxicity at concentrations up to 20mg/ml. Using water preboiled with another sample reduced the detoxicatory effect. Detoxified samples that had been dried did not recover their toxicity for up to 8 hours. The authors conclude that boiling quartz samples in glass tubes causes a concentration dependent loss of cytotoxicity. This may be due to release of soluble or partially soluble factors, possibly silicic-acid (1343982) or sodium or calcium silicates or hydroxides, from the mineral surface.
NIOSH-Author; In-vitro-studies; Silica-dusts; Thermal-effects; Cytotoxic-effects; Red-blood-cells; Respirable-dust; Hemolysis; Dose-response; Surface-properties; Detoxification;
Proceedings of the VIIth International Pneumoconioses Conference