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Biodurability of inhaled tungsten oxide fibers and particles.
Stefaniak A; Virji MA; Day G
Epidemiology 2011 Jan; 22(1)(Suppl S):S289
Background/Aims: To manufacture wire for light bulb filaments, tungsten oxide (WOx) powder is reduced to tungsten metal, during which fiber-containing aerosols may be generated. While fiber dimensions determine, in part, the extent which they are inhaled, retained, and mechanically cleared by the lung, their chemistry influences physiological durability. The purpose of this study was to measure the dissolution of fiber- and isometric-shaped tungsten compounds in lung fluids. Methods: Three common industrial powders that contained fibers (WO2.81, WO2.66, and WO2.51) and 3 that contained isometric-shaped particles (WO3.00, WO2.98, and W metal) were characterized by microscopy. Dissolution behavior of all powders was evaluated using a static dissolution technique in 2 different artificial fluids: airway epithelial lining fluid (pH = 7.3) and alveolar macrophage phagolysosomal fluid (pH = 4.5). Fiber data were modeled assuming constant dissolution velocity and isometric particle data modeled assuming surface-area-limited dissolution. Results: Fibers were respirable with high probability of deposition in the nonciliated alveolar region of the lung. The WO2.81 and WO2.51 powders were 80% fibers/20% particles by mass, whereas the WO2.66 powder was 2% fibers/98% particles by mass. At pH 4.5, the rank order of dissolution in units of g/cm2·day was as follows: WO2.66 (4.3 +/- 0.4 × 10-7) > W (3.7 +/- 1.9 × 10-7) [almost equal to]WO2.51 (2.4 +/- 0.1 × 10-7) > WO2.98 (1.0 +/- 0.1 × 10-8) > WO2.81 (3.3 +/- 0.9 × 10-8) > WO3.00 (9.3 +/- 5.5 × 10-9). At pH 7.3, the order was: WO3.00 (5.7 +/- 1.8 × 10-6) > W (3.0 +/- 0.5 × 10-6) > WO2.98 (1.0 +/- 0.1 × 10-6) [almost equal to] WO2.81 (1.0 +/- 0.1 × 10-6) > WO2.66 (6.7 +/- 0.5 × 10-7) > WO2.51 (3.0 +/- 0.2 × 10-7). Conclusion: All tungsten compounds were poorly soluble and each tended to dissolve slower in acidic phagolysomal fluid than in neutral airway epithelial lining fluid. Fiber-containing WO2.81 and WO2.51 materials were respirable size and generally less soluble than isometric-shaped tungsten materials and therefore, may persist longer in the alveolar region of the lung.
Tungsten-compounds; Oxides; Particulates; Occupational-exposure; Biological-effects; Fiber-deposition; Metal-oxides; Metals; Metal-compounds; Lung; Lung-function; Physiological-response; Fluids; Microscopy; Pulmonary-system; Respiration
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Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division