Abstract
BackgroundDuring the manufacture of tungsten metal for non-sag wire, tungsten oxide powders are produced as intermediates and can be in the form of tungsten trioxide (WO3) or tungsten blue oxides (TBOs). TBOs contain fiber-shaped tungsten sub-oxide particles of respirable or thoracic size. The aim of this research was to investigate whether fiber-containing TBOs had prolonged biodurability in artificial lung fluids compared to tungsten metal or WO3 and therefore potentially could pose a greater inhalation hazard.MethodsDissolution of tungsten metal, WO3, one fiber-free TBO (WO2.98), and three fiber-containing TBO (WO2.81, WO2.66, and WO2.51) powders were measured for the material as-received, dispersed, and mixed with metallic cobalt. Solubility was evaluated using artificial airway epithelial lining fluid (SUF) and macrophage phagolysosomal simulant fluid (PSF).ResultsDissolution rates of tungsten compounds were one to four orders of magnitude slower in PSF compared to SUF. The state of the fiber-containing TBOs did not influence their dissolution in either SUF or PSF. In SUF, fiber-containing WO2.66 and WO2.51 dissolved more slowly than tungsten metal or WO3. In PSF, all three fiber-containing TBOs dissolved more slowly than tungsten metal.ConclusionsFiber-containing TBO powders dissolved more slowly than tungsten metal and WO3 powders in SUF and more slowly than tungsten metal in PSF. Existing pulmonary toxicological information on tungsten compounds indicates potential for pulmonary irritation and possibly fibrosis. Additional research is needed to fully understand the hazard potential of TBOs.
Highlights
Tungsten is a naturally occurring element that has industrial value in the form of its metal, oxide, and salts
Given the role of fiber-shaped particles in lung toxicity we investigated whether fibercontaining tungsten blue oxides (TBOs) are more durable in artificial lung fluids than tungsten metal or WO3 and potentially could pose a greater inhalation hazard
Study overview The objective of this study was to evaluate whether TBO fibers had prolonged biodurability in artificial lung fluids compared to tungsten metal or WO3
Summary
Tungsten is a naturally occurring element that has industrial value in the form of its metal, oxide, and salts. The production of non-sag wire involves calcination of ammonium paratungstate to yield tungsten oxide powder intermediates which are subsequently reduced under controlled conditions to yield tungsten metal powder for making wire filaments. The type of tungsten oxide intermediate produced depends on the calcination conditions, including furnace atmosphere. TBO is not a welldefined compound; rather, it is a blue-colored mixture of crystalline hexagonal tungsten bronzes, WO3, and various non-stoichiometric tungsten sub-oxides and an amorphous oxide [2,3]. During the manufacture of tungsten metal for non-sag wire, tungsten oxide powders are produced as intermediates and can be in the form of tungsten trioxide (WO3) or tungsten blue oxides (TBOs). TBOs contain fiber-shaped tungsten sub-oxide particles of respirable or thoracic size. The aim of this research was to investigate whether fiber-containing TBOs had prolonged biodurability in artificial lung fluids compared to tungsten metal or WO3 and potentially could pose a greater inhalation hazard
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