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Environmental fate & pathways

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Description of key information

Hydrolysis is not a relevant process for tungsten dioxide, as in principle, water acts as an oxidizing agent with tungsten compounds (Lassner and Schubert, 1999). The behavior of the substance in water is more accurately examined through the Transformation/Dissolution testing protocol (see Table 5 in section 1.3).

Additional information

No data on bioaccumulation or levels of tungsten dioxide in aquatic organisms are available. However, bioaccumulation/bioconcentration of tungsten metal and inorganic tungsten compounds such as tungsten dioxide is not expected to occur in aquatic or sediment species, as the bioavailability of tungstate (the bioavailable form) from tungsten compounds is expected to be low in the water column due to stream and river sediment adsorption and low potential for leaching from soils. Furthermore, any uptake mediated by transport proteins would be expected to be internally regulated. The absence of methylated tungsten species also supports the claim that bioaccumulation is not expected to be of concern for tungsten and inorganic tungsten compounds.

Bioaccumulation of tungsten in terrestrial organisms after tungsten dioxide exposures are not expected based on BCFs calculated from paired concentrations of tungsten in soil and worm or soil and plant tissue (read-across from tungsten metal and sodium tungstate).

Based on reported Kd values for tungsten compounds in soil and sediment, their mobility in respective compartments is expected to be low.