AUGMENTATION OF PULMONARY REACTIONS TO QUARTZ INHALATION BY TRACE AMOUNTS OF IRON-CONTAINING PARTICLES

Fracturing quartz produces silica-based radicals on the fracture plane s and generates hydroxyl radicals ((OH)-O-.) in aqueous media. (OH)-O- . production has been shown to be directly associated with quartz-indu ced cell damage and phagocyte activation in vitro. This (OH)-O-. produ ction in vitro is inhibited by desferrioxamine mesylate, an Fe chelato r, indicating involvement of a Fenton-like reaction. Our objective was to determine if Fe contamination increased the ability of inhaled qua rtz to cause inflammation and lung injury. Male Fischer 344 rats were exposed 5 hr/day for 10 days to filtered air, 20 mg/m(3) freshly mille d quartz (57 ppm Fe), or 20 mg/m(3) freshly milled quartz contaminated with Fe (430 ppm Fe). High Fe contamination of quartz produced approx imately 57% more reactive species in water than quartz with low Fe con tamination. Compared to inhalation of quartz with low Fe contamination , high Fe contamination of quartz resulted in increases in the followi ng responses: leukocyte recruitment (537%), lavageable red blood cells (157%), macrophage production of oxygen radicals measured by electron spin resonance or chemiluminescence (32 or 90%, respectively), nitric oxide production by macrophages (71%), and lipid peroxidation of lung tissue (38%). These results suggest that inhalation of freshly fractu red quartz contaminated with trace levels of Fe may be more pathogenic than inhalation of quartz alone.