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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

No long-term toxicity studies in fish are available for sodium borohydride since it rapidly hydrolyzes in water to form sodium borate/boric acid and hydrogen gas with half-lives ranging from seconds to minutes at environmentally relevant pHs. Therefore, aquatic toxicity data for boric acid was used.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater fish:
17.5 mg/L

Additional information

No aquatic toxicity data is available for sodium borohydride since the compound rapidly hydrolyzes in water to form sodium borate/boric acid and hydrogen gas with half-lives ranging from seconds to minutes at environmentally relevant pHs.

Therefore, toxicity data for the toxicologically relevant hydrolysis product boric acid is applied for the safety assessment.

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 NaBH4 for this IUCLID. The lowest value taken from the key study with zebrafish was a 34 -day NOEC for growth determined as length. The NOEC was 5.6 mg B/L which was converted to 17.5 mg NaBH4/L and used for the freshwater PNEC derivation. A lower value was reported from this study for dry weight but due to the presence of an outlier and an indiscrpency between the results and summary sections within the report, the NOEC for growth as length was chosen. This value is seen as conservative due to the large number of studies with fish (~174).