Tetrafluoroboric acid

Toxicity to aquatic algae and cyanobacteria

Description of key information

Data on the toxicity to aquatic algae is available from the HBF4 chemical 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 due to molecular weight correction is considered unproportional 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.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

70 mg/L

Additional information

A GLP-compliant OECD 201 guideline study is available for toxicity in alga (Pseudokirchnerella subcapitata) for potassium tetrafluoroborate. In this combined limit/range-finding test alga were exposed to 0.10, 1.0, 10 and 100 mg/L potassium tetrafluoroborate a blank control (test medium without test substance or other additives) and 1 or 2 replicates of each test concentration without algae for a period of 72 hours under static conditions. Analysis of the samples taken from 100 mg/L showed a measured concentration of 116 mg/L at the start of exposure. The concentration remained stable during the 72-hour test period (96-101% of initial). No significant reduction of growth rate or inhibition of yield was recorded at any of the concentrations of potassium tetrafluoroborate tested. The 72-h EC50 values for both growth rate and biomass were >100 mg/L, the NOEC is 100 mg/L for both parameters (based on nominal concentrations).

As no significant effects were seen at any of the concentrations KBF4 tested and thus the effects values EC50 were expressed as "larger than" the highest concentration tested, the molecular weight correction (i.e. a 72 -h EC50 of >70 mg/L for HBF4) is considered unproportional for purposes of risk assessment and classification and labeling. Therefore the effect value EC50 of HBF4 for aquatic invertebrates is maintained at 100 mg/L. For the NOEC value molecular weight correction is in place. The 72 -h NOEC value for HBF4 is determined at 70 mg/L.