Esr evidence for the hydroxyl radical formation in aqueous suspension of quartz particlesand its possible significance to lipid peroxidation in silicosis

Electron spin resonance (ESR) spectrum of the hydroxyl (o OH) radical spin adduct withthe spin trap 5, 5-dimethyl-1-pyrroline-N-oxide has been obtained in suspensions of freshly ground quartz particles. The concentration of the spin adduct (and hence of the o OH radicals) increases with the amount of grinding. The dust’s potential for the generation ofthe o OH radicals is maximum when fresh (i.e., immediately after grinding) and decreases to 50% in about a day on storage in air. Studies involving metal chelates indicate that the o OH radical formation involves mainly the silica sur face and H20 rather than the Fenton reaction. The results suggest that hydroxyl radi cal reaction(s) could be important in the lipid peroxidation and fibrogenicity by quartz dust, particularly in acute silicosis.