Sodium tetrahydroborate

Sediment toxicity

Description of key information

Three studies are available for boric acid.  The geometric mean of these two studies was calculated, and converted to account for the boron content in sodium borohydride. 

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:

255 mg/kg sediment dw

Additional information

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. A 2011 chronic sediment toxicity study was designated a key study for exposure of boric acid to Chironomus 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/kg sediment. An additional study using the same route of exposure was available and reported a NOEC of 108 mg/kg sediment for mortlaity and emergence rate. Because these studies were similar exposures using similar guidelines, the geometric mean was calculated as 82.4 mg/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 255 mg/kg boron. 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.