Detection of Hydroxyl Radicals in Aqueous Suspensions of Fresh Silica Dust and its Implication to Lipid Peroxidation in Silicosis.
Dalal-NS; Shi-X; Vallyathan-V
NIOSH 1990 Sep:250-253
Hydroxyl radical (OH) formation in aqueous suspensions of fresh silica (14808607) dust was examined. Samples of crystalline silica having particle diameters of 0.2 to 2.5 millimeters were ground for dimethyl-1-pyrroline-1-oxide (DMPO), which was used as a radical trap, in the presence or absence of 30% ethanol. The samples were analyzed for OHs by electron spin resonance (ESR) spectroscopy. ESR spectra produced by the Fenton reaction, a reaction between ferrous ions and hydrogen-peroxide that was known to produce OH radicals, were used as a positive control. A similar experiment was done in which the silica/DMPO suspensions were aged for 5 minutes to 4 days before analysis. The ESR spectra of the silica/DMPO suspensions with or without added ethanol were identical to spectra produced by the Fenton reaction indicating that OH radicals had been formed. The intensity of the ESR signals increased the amount of grinding. The intensity of the signals decreased with increasing aging time. Attempts to determine the kinetics of signal decay were unsuccessful; however, freshly ground dust samples appeared to lose about half of their OH generating capacity in 1 day. The authors conclude that OH generation by silica particles is related to some surface property, most likely silicon/oxygen radical sites that are known to be formed by grinding. Grinding itself causes the quartz surface to be a source of OH radicals in aqueous media and this activity decreases with aging of the particles. The mechanism of cellular membrane damage by quartz might involve OH radicals.
In-vitro-studies; Silica-dusts; Surface-properties; Free-radical-generation; Chemical-reactions; Sample-preparation; Spectrographic-analysis; Mineral-dusts;
DHHS (NIOSH) Publication No. 90-108
Proceedings of the VIIth International Pneumoconioses Conference