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Short-term toxicity to fish

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Description of key information

A short-term toxicity study to fish with cesium sulphate is not available. Consequently, read-across was applied using data from cesium hydroxide monohydrate. 
Under the conditions of this acute fish toxicity study the observed endpoints for the effect of cesium hydroxide monohydrate were the followings: 96h NOEC value: ≥ 100 mg test item/L; 96h LOEC value: > 100 mg test item/L and 96h LC50 value: > 100 mg test item/L. Based on these data the calculated values of 96h-LC50, 96h-LOEC and 96h-NOEC for cesium are greater than 79.2 mg/L and for cesium sulphate are greater than 107.8 mg/L.

Key value for chemical safety assessment

LC50 for freshwater fish:
107.8 mg/L

Additional information

A short-term toxicity study to fish with cesium sulphate is not available. Consequently, read-across was applied using data from cesium hydroxide monohydrate.

Acute toxicity of the test item was assessed with acute fish toxicity test on Zebrafish (Danio rerio) over an exposure period of 96 hours in a static system. The recorded effects were mortality and symptoms of intoxication of the fish. Based on the results of a preliminary range finding test, a limit test was performed: one control and the concentration of 100 mg/L of the test item were tested according to the relevant guideline (OECD 203). Both test groups comprised seven zebrafish and 5 L test solution. No replicates were tested. The test was considered to be valid because assay acceptance criteria were fulfilled. Analytical determination of the test concentration was performed by flame photometry.

Based on the analytical results, the test concentration did not differ from the nominal concentration significantly, hence the biological results based on the nominal concentration of 100 mg/L. No mortality or clinical symptoms were observed in the control. Clinical symptoms (increased motility of operculum, unbalanced swimming, localisation under the water surface, thrashing toward the bottom) was observed on 1 fish from the 7 in the 100 mg/L test item treated group at the 24 hours observation time. Although mortality (1/7 fish) was observed on the subsequent day (at the 48 hours observation time) in this group, this was within the assay acceptance criteria (one animal can die in the control group). Hence the test was considered to be valid and the mortality observed was not taken into consideration during evaluation of the results.

Under the conditions of this acute fish toxicity study the observed endpoints for the effect of cesium hydroxide monohydrate were the following: 96h NOEC value: ≥ 100 mg test item/L; 96h LOEC value: > 100 mg test item/L and 96h LC50 value: > 100 mg test item/L. Based on these data the calculated values of 96h-LC50, 96h-LOEC and 96h-NOEC for cesium are greater than 79.2 mg/L and for cesium sulphate are greater than 107.8 mg/L.