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For tetrafluoroboric acid (HBF4) the base set data are available either from the substance itself or from its structural analogues sodium tetrafluoroborate (NaBF4) and potassium tetrafluoroborate (KBF4).

A GLP-compliant guideline short-term toxicity study with freshwater fish is available for HBF4. Prior to the initiation of the test the pH value of the stock solution was adjusted to 7.5 with NaOH. The critical effect concentration is a 96-h LC50 value of 1300 mg/L in zebrafish (Brachidanio rerio).

A GLP-compliant guideline short-term toxicity study with aquatic invertebrates is available for the HBF4 structural analogue KBF4. The 48 -h EC50 value is determined at >100 mg/L which is equivalent to >70 mg/L when corrected for molecular weight of HBF4. In addition, a non-GLP near guideline study short-term toxicity study is available for the HBF4 structural analogue NaBF4. In this study a 48 -h EC50 value of 4766 mg/L NaBF4 was determined which is equivalent to 3811 mg/L HBF4 after correction for molecular weight. As no effects were seen at any of the KBF4 concentrations tested and in addition the effect value from the NaBF4 study was considerably higher, molecular weight correction of the critical effect value of >100 mg/L is considered non-proportional for purposes of risk assessment and classification and labeling. Therefore the critical effect value of HBF4 for aquatic invertebrates is maintained at 100 mg/L.

Long-term toxicity data for aquatic invertebrates are also available for the HBF4 structural analogue NaBF4. The 21-d NOEC for NaBF4 in daphnids was determined at 188 mg/L which is equivalent to 150 mg/L when corrected for the molecular weight of HBF4.

A GLP-compliant guideline study with freshwater algae is available for the HBF4 structural analogue KBF4. The 72-h ErC50 and NOEC values for KBF4 in alga were determined at >100 mg/L and 100 mg/L, respectively. The EC50 value is maintained at 100 mg/L (i.e. not corrected for molecular weight) as no effects were seen up to the highest concentration tested and lowering of the EC50 values is considered non-proportional for purposes of risk assessment and classification and labeling. The 72-h NOErC is corrected for molecular weight which leads to a value of 70 mg/L.

A GLP-compliant guideline microorganism growth inhibition study is available for HBF4. In this study Pseudomonas putida were exposed to test concentrations of HBF4 with and without pH correction for a period of 18 hours under static conditions. The 18-h EC50 and EC10 values were 6.4 and 61.3 mg/L without pH adjustment en 397 and 4974 mg/L at pH 7.4 (nominal concentrations). The 18-h EC10 pH corrected value of 397 mg/L at pH 7.4 is used in the assessment.