Augmentation of pulmonary reactions to quartz inhalation by trace amounts of iron-containing particles.

Abstract

Fracturing quartz produces silica-based radicals on the fracture planes and generates hydroxyl radicals (OH) in aqueous media. 'OH production has been shown to be directly associated with quartz-induced cell damage and phagocyte activation in vitro. This 'OH production in vitro is inhibited by desferrioxamine mesylate, an Fe chelator, indicating involvement of a Fenton-like reaction. Our objective was to determine if Fe contamination increased the ability of inhaled quartz to cause inflammation and lung injury. Male Fischer 344 rats were exposed 5 hr/day for 10 days to filtered air, 20 mg/m3 freshly milled quartz (57 ppm Fe), or 20 mg/m3 freshly milled quartz contaminated with Fe (430 ppm Fe). High Fe contamination of quartz produced approximately 57% more reactive species in water than quartz with low Fe contamination. Compared to inhalation of quartz with low Fe contamination, high Fe contamination of quartz resulted in increases in the following 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 fractured quartz contaminated with trace levels of Fe may be more pathogenic than inhalation of quartz alone. Environ Health Perspect 105(Suppl 5): 1319-1324 (1997)

Occupational Exposure to Crystalline Silica and Autoimmune Disease

“…For instance, iron ore in quartz dust can increase the production of reactive oxygen species and several measures of immune stimulation (126). Other factors may impact the effect of silica; freshly fractured silica appears to be more reactive than aged dust (127).…”

Free radical generation in the toxicity of inhaled mineral particles: the role of iron speciation at the surface of asbestos and silica

“…[21][22][23][24] Iron also has been claimed to act as a source of radicals on silica. 25,26 However, iron is not present on any silica specimen. Traces may be present only as impurities acquired during processing or endogenously.…”

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“…In other studies, the presence of minerals other than quartz has been noted to be critical for particle inflammatory potential [11]. For example, high iron concentrations in biological systems (e.g., iron released by ferritin under pathological conditions) can cause oxidation to biomolecules [12-16] and iron associated with asbestos [17,18], quartz [19], iron oxides [20,21], and iron sulfides [22-24] has been shown to be a key reactant in the mechanisms leading to lung injury.…”