Registration Dossier

Classification & Labelling & PBT assessment

PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

Trimethyl borate rapidly hydrolyzes in water with a half-life less than 1 second (0.02 minutes) to form methanol and boric acid. Thus, the PBT assessment is based on an evaluation of methanol and boric acid.

Methanol is readily biodegradable while boric acid is an inorganic compound to which biodegradation is not applicable.

Conclusion: Not P/vP.

Methanol has a log  Kow < 3 which indicates that it will have a low potential for bioaccumulation. Boric acid is a water soluble, inorganic compound for which bioaccumulation is not relevant in this case.

Conclusion: Not B/vB.

Methanol is much less toxic to aquatic organisms compared to boric acid. Therefore, data compiled on boric acid is used to assess toxicity. 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. Although a number of studies were available for exposure to fish, the lowest reliable value was taken from a key study with zebrafish (Hooftman et al, 2000). The NOEC was 5.6 mg B/L which was converted to 53.82 mg C3H9BO3/L and used for freshwater PNEC derivation. This value is above the threshold for T.

Conclusion: Not T based on ecotoxicology endpoints.

However, boric acid is classified as a reproductive toxicant.

Conclusion: T based on mammalian toxicology endpoints.