Generation of reactive oxygen species by quartz particles and itsimplication for cellular damage

Using wet analytical chemistry and electron spin resonance spin trapping, we have shown that aqueous suspensions of freshly fractured quartz particles generated hydrogen peroxide, hydroxyl radical, superoxide radical, and singlet oxygen. Superoxide dismutase partiallyinhibited the hydroxyl radical yield, whereas catalase suppressed it.Hydrogen peroxide enhanced the hydroxyl radical generation, whiledeferoxamine decreased it. Oxygen consumption measurementsshowed that freshly fractured quartz particles consumed molecularoxygen. Electrophoretic assays showed that freshly fractured quartzparticles induced DNA double-strand breakage, which was inhibitedby catalase. In an argon atmosphere DNA damage was suppressed, showing that molecular oxygen is required for quartz-induced DNAdamage. Quartz particles also caused dose-dependent lipid peroxidation as measured by malondialdehyde formation. Superoxide dismutase, catalase, and sodium benzoate inhibited quartz-induced lipidperoxidation by 49, 52, and 75 percent, respectively. The resultsdemonstrate that reaction of freshly fractured quartz particles withaqueous medium and hydrogen peroxide generates reactive oxygenspecies, which may play an important role in the mechanism ofquartz-induced cellular injury.