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Experimental data on the acute toxicity of Boron orthophosphate (CAS 13308-51-5) are available for fish, daphnia and algae. All three studies show no toxicity up to 100 mg/L nominal test concentration.  The test substance revealed low water solubility in the test media. In all aquatic toxicity tests, the test substance achieved the maximum solubility in all test media under the test solution preparation methods, but the dissolved boron concentrations increased with increasing of the nominal test concentrations and did not achieve saturation. Thus, the test results are reported with both nominal test substance concentrations and the measured boron concentrations respectively. Since no effects observed in either short-term or long-term tests of three trophic levels, it can be concluded that no aquatic toxicity was found under the test conditions. .

The acute toxicity of Boron orthophosphate to fish (Danio rerio) was conducted according to OECD 203 (Simon, 2015) under semi-static conditions. The test solutions were freshly prepared by adding respective amount of test substance to dilution water. Subsequently the insoluble parts were separated by filtration using 0.2 µm membrane. There were no concentration-dependent effects on survival up to the highest nominal test substance concentrations of 100 mg/L , which correspond to the measured concentration of 0.207 mg boron per liter (96h LC50 > 0.207 mg boron/L (meas. arithm. mean)).

The acute toxicity of Boron orthophosphate to Daphnia magna was determined in a study following OECD 202 (Simon, 2014) under static conditions. The test solutions were freshly prepared by serial dilution of supernatant solution prepared with 100 mg/L of nominal test substance concentration. There were no concentration-dependent effects on immobilization up to the highest nominal test substance concentration of 100 mg/L, corresponding to  0.135 mg boron per liter (48h EC50 > 0.135 mg boron/L (meas. arithm. mean).

The influence of Boron orthophosphate (CAS 13308-51-5) on growth of the freshwater green alga Pseudokirchneriella subcapitata was investigated in a static OECD 202 test under GLP conditions (Simon, 2014). The test solutions were freshly prepared by serial dilution of supernatant prepared with 100 mg/L of nominal test substance concentration and growth rate of algae. The test was terminated after 72 hours. There were no concentration-dependent effects on the growth of the green algae up to the highest test concentrations of 1.35 mg boron/L. The ErC50 and EyC50 values for inhibition of growth rate and yield were set to be > 1.35 mg boron/L (> 100 mg/L nominal). Based on the growth a NOEC ≥ 1.35 mg boron/L (meas. initial) and > 100 mg/L nominal test substance concentration was observed.

Experimental data on the long-term toxicity of Boron orthophosphate (CAS 13308-51-5) to aquatic invertebrates are available. Daphnia magna was exposed to Boron orthophosphate in a semi static OECD 211 test under GLP conditions (Simon, 2016). The highest test solution with 3.75 mg/L nominal test substance concentration was freshly prepared by addition method and the other test solutions were using serial dilution of supernatant prepared with 1.5 mg/L of nominal test substance concentration. No adverse effects were observed in the test. The NOEC is ≥ 3.75 mg /L (nominal test substance concentration) and ≥ 494 µg test item/L (TWM).

The influence of Boron orthophosphate (CAS 13308-51-5) on the respiration of activated sewage sludge was investigated in a static OECD 209 test under GLP conditions (Simon, 2015). The effect of Boron orthophosphate on the respiration of activated sewage sludge gave a 3h- EC50 of greater than 1000 mg/L. The EC20 (3h) was determined to be ≥ 1000 mg/L (nominal test substance conc.). No significant inhibition of bacterial respiration by Boron orthophosphate up to and including a concentration of 1000 mg/L was observed.

Based on the available information Boron orthophosphate (CAS 13308-51-5) is considered not having short-term or long-term toxicity to aquatic organisms under environmental conditions.