Ozone is known to induce lipid peroxidation of lung tissue, although no direct evidence of free radical formation has been reported. The study used the electron paramagnetic resonance (EPR) spin-trapping technique to search for free radicals produced in vivo by ozone exposure. The spin trap alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (4-POBN) was administered i.p. to male Sprague-Dawley rats. The rats were then exposed for 2 hrs to either 0, 0.5, 1.0, 1.5 or 2.0 ppm ozone with 8% CO2 to increase their respiratory rate. A 6-line 4-POBN/radical spin adduct signal a(sup N)=15.02 G and a(sup H)beta-3.27 G) was detected by EPR spectroscopy in lipid extracts from lungs of rats treated with 4-POBN and then exposed to ozone. Only a very weak signal was observed in the corresponding solution from rats exposed to 0 ppm ozone (air with CO2 only). The concentration of the radical adduct increased as a function of ozone concentration. After administration of 4-POBN, rats were exposed for either 0.5, 1.0, 2.0 or 4.0 hrs to either 0 or 2.0 ppm ozone (with CO2). These results demonstrate that ozone induces the production of free radicals in rat lungs during inhalation exposure and that radical production may be involved in the induction of lung edema by ozone.

"EPA 600/D-91/111." Microfiche.