Potassium tetrafluoroaluminate

Toxicity to aquatic algae and cyanobacteria

Description of key information

In alga (Pseudokirchneriella subcapitata), 72-h EC50 and NOEC values for growth rate are determined at 11.3 mg/L and 3.8 mg/L, respectively. These values correspond to ErC50 and NOErC values of 6.0 mg fluoride/L and 2.0 mg fluoride/L, respectively. These values will be used in the assessment. 

Key value for chemical safety assessment

EC50 for freshwater algae:

6 mg/L

EC10 or NOEC for freshwater algae:

2 mg/L

Additional information

Two reliable acute/chronic toxicity studies (Klimisch 1, GLP) for the algal species Pseudokirchneriella subcapitata are available (ECT Oekotoxikologie, 2012a and b). The studies have been conducted with two different batches of aluminium potassium fluoride: Nocolok Flux and Hot melt PAF. The 72-h EC50 values for growth rate were 33.5 and 12.7 mg/l, respectively. The 72 hr NOErC values were reported to be 11.2 and 4.3 mg/l, respectively. During the conductance of this study, special attention was given to the preparation of test solutions since it is known that the test substance can form precipitates with nutrient salts present in the algal medium. For this reason, two different medium types (Kuhl&Lorenzen-medium and modified OECD medium) have been tested in a pre-test and the medium with the highest recovery of the test substance was selected for the final test. Test solutions were analysed to determine actual levels of fluoride, calculated based on the fluoride content in the test item. The determinations of actual concentrations in the studies showed mean recoveries of 97.8% for Nocolok Flux and 73 - 96% for Hot melt PAF with a decline at higher concentrations. In addition, no precipitates were observed during the tests. For this reason, it was concluded that the results of both studies were suitable for hazard and risk assessment purposes. The lowest observed values, ErC50 of 12.7 mg/l and NOErC of 4.3 mg/l will be used in the assessment.

As the contents of fluoride, expressed as a percentage of the molar weight in both substances are comparable, namely 53.5% for potassium tetrafluoroaluminate and ca. 51% for multiconstituent aluminium potassium fluoride, as a result no safety factor is applied. Instead, the effect concentrations will be corrected for molecular weight. The ErC50 and NOErC values corrected for potassium tetrafluoroaluminate are 11.3 and 3.8 mg/L, respectively which corresponds to 6.0 and 2.0 mg/L when based on fluoride content.