Cesium potassium fluoroaluminate

Short-term toxicity to fish

Description of key information

The 96-h LC50 for cesium potassium fluoroaluminate in Gobiocypris rarus was >120 mg/L based on nominal concentrations. 

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

120 mg/L

Additional information

One reliable study is available and was selected as key study. The GLP-compliant OECD 203 guideline study with Gobiocypris rarus was conducted as part of a new chemical substance notification in China. The study was conducted as semi-static limit test at a nominal concentration of 120 mg/L. The treatment group and the control group had one replicate, each containing 10 fish and the test duration was 96h. No mortality occurred in the control during the test and the dissolved oxygen concentration was greater than 60% of the air saturation value throughout the test. Hence, the test was considered to be valid. During the test, the measured concentration of aluminum (Al) analysed by ICP-MS, varied greater than 20% during the test. Since the test substance consists of four elements (Cs, K, Al and F), the measured concentrations of the test substance were not actually calculated by the measured concentrations of Aluminium analyzed by ICP-MS. In order to reflect the toxicity of the test substance, the results were expressed as the nominal concentrations.The 96h LC50 (based on the nominal concentrations) for cesium tetrafluoroaluminate was >120 mg/L.

A previous study (Bouwman, 2004a) performed by NOTOX BV according to OECD 203 has been disregarded because of deficiencies in the analytical method. The quantification of the test substance is based on the analysis of cesium which is present at 5.64% w/w in the test substance. The measured concentrations of the test substance were actually calculated by the measured concentrations of Cesium.

Part of the test solutions prepared for the range-finding test and the final test were used in the simultaneously performed acute daphnia toxicity test (NOTOX project 394717). Analyses of a sample taken at the start of the final daphnia test from the undiluted filtrate prepared at a loading rate of 100 mg/L showed a cesium concentration of 505 µg/L (8.9 mg/L test substance) while a cesium concentration of only 178 µg/L (3.1 mg/L test substance) was measured in the same solution at the start of the final fish test. In addition, this concentration was much lower than the concentration found in the range-finding test in which a cesium concentration of 889 µg/L (15.8 mg/L test substance) was measured in the undiluted filtrate that was prepared in the same way and at the same concentration. Overall, the concentrations of cesium in the test solutions are significantly lower than expected based on the percentage of cesium in the test substance. No explanation was given for this difference.

Since the analytical method used to quantify the test substance in the test solution is not considered sufficiently robust, the effect concentrations found in this study are disregarded for assessment. In addition, the test substance consists of four elements (Cs, K, Al and F) and the biological effects are expected to be mostly governed by the presence of fluoride and aluminium ions formed upon dissociation of the fluoroaluminate moieties. Therefore in order to reflect the toxicity of the test substance, it is not correct to express the results as the mean measured cesium concentrations.