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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

No aquatic 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 aquatic organisms compared to boric acid. Therefore, aquatic toxicity data for boric acid was used.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
168.18 mg/L

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 aquatic organisms compared to boric acid. Thus, PNEC values derived for boric acid are protective of the environment for the stoichiometric contribution of methanol.Therefore, 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 Trimethyl borate for this IUCLID. A GLP study following OECD 209 respiration inhibition test guidelines was identified as the key study (Hanstveit and Schoonmade, 2000). The reported endpoint used to derive the PNECstp was an NOEC of 17.5 mg B/L or 168.18 mg C3H9BO3/L.