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Ecotoxicological information

Sediment toxicity

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Description of key information

No sediment toxicity data are available for trimethyl borate since the compound rapidly hydrolyzes in water with a half-life of less than 1 second to form methanol and boric acid. Methanol is much less toxic to sediment organisms compared to boric acid. Therefore, sediment toxicity data for boric acid was used.  Three studies are available for boric acid.  The geometric mean for two sediment studies was calculated, and converted to account for the boron content in trimethy borate.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:
792 mg/kg sediment dw

Additional information

The study is not technically feasible because the test substance hydrolyzes in water with a half-life of less than 1 second to form methanol and boric acid. Methanol is much less toxic to environmental organisms compared to boric acid. Therefore, sediment toxicity data compiled on boric acid was used. The endpoints included in the dossier under environmental hazard assessment were reported from studies on the ecotoxicity of boron and various compounds, such as boric acid (H3BO3), anhydrous sodium tetraborate (Na2B4O7), and hydrated sodium tetraborates (Na2B4O7.xH2O). All endpoints were converted to concentrations of elemental boron (B) using the relative molar mass and then converted to C3H9BO3 for this IUCLID. A 2011 chronic sediment toxicity study was designated a key study for exposure of boric acid toChironomus riparius,in which the organisms were exposed to spiked sediment (the most relevant route of exposure for this sediment-dwelling organism) and reported a NOEC for mortality, developmental rate and emergence rate of 37.7 mg B/kg sediment. An additional study using the same route of exposure was available and reported a NOEC of 180 mg B/kg sediment for mortality and emergence rate. Because these studies were similar exposures using similar guidelines, the geometric mean was calculated as 82.4 mg B/kg sediment to serve as the most conservative estimate of the NOEC for sediment exposure. When converted for the boron content of the compound, this equals a concentration of 792 mg/kg for trimethyl borate. A third study was available but not included in the calculation as it was not considered as relevant because the route of exposure was via spiked water.