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ESR evidence for the hydroxyl radical formation in aqueous suspension of quartz particles and its possible significance to lipid peroxidation in silicosis.

Shi-X; Dalal-NS; Vallyathan-V
J Toxicol Environ Health 1988 Oct; 25:237-245
Hydroxyl radical formation in aqueous suspensions of quartz (14808607) particles was investigated. Aqueous suspensions of ground or unground quartz with initial particle sizes of 0.2 to 2.5 millimeters were prepared and examined by electron spin resonance (ESR) spectroscopy using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap. Similar experiments were conducted with titanium- dioxide (13463677) for comparison surfaces. The suspensions of ground quartz produced a strong signal indicative of the hydroxyl radical trapped in DMPO. The strength of the signal depended on the amount of quartz. Suspensions of freshly ground quartz particles produced more hydroxyl radicals than those containing particles that had stood in air before grinding. The hydroxyl radical was not detected in suspensions of unground quartz or titanium-dioxide. Additionally, ESR spectra were obtained of the products of the reaction of ferrous-sulfate and hydrogen-peroxide (the Fenton reaction) and of ground quartz suspensions containing 30 percent ethanol, a hydroxyl radical scavenger. The ESR spectra of the Fenton reaction products were identical to those of the ground quartz suspensions. The intensity of the hydroxyl radical signal was decreased by ethanol. The authors conclude that hydroxyl radicals are generated by freshly ground quartz particles reacting with aqueous solutions. The radicals are formed on the surface of the quartz rather than by a Fenton type reaction. These findings suggest that inhaled quartz particles may damage cell membranes through lipid peroxidation by way of a free radical reaction initiated by hydroxyl reactions.
NIOSH-Author; In-vitro-studies; Quartz-dust; Oxidative-processes; Surface-properties; Particulates; Physiological-chemistry; Silicosis
14808-60-7; 13463-67-7
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Journal of Toxicology and Environmental Health