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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

A toxicity study to microorganisms with cesium sulphate is not available. Consequently, read-across was applied using data from cesium hydroxide monohydrate. Under the conditions of the performed Activated Sludge Respiration Inhibition Test, the EC10 and EC50 values of cesium hydroxide monohydrate were determined as higher than 1000 mg/L. Based on the statistical evaluation in this test the NOEC was 1000 mg/L for cesium hydroxide monohydrate. 
Based on these data, the calculated EC10 and EC50 values of cesium were greater than 792 mg/L and the NOEC was 792 mg/L and for cesium sulphate the calculated values were as follows: EC10 and EC 50 >1077.6 mg/L and NOEC 1077.6 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1 077.6 mg/L
EC10 or NOEC for microorganisms:
1 077.6 mg/L

Additional information

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

The purpose of the 3-hour test was to evaluate the influence of the test item cesium hydroxide monohydrate on the activity of activated sludge by measuring the respiration rate under defined conditions. The respiration rates (total, heterotrophic and nitrification oxygen uptake rates) of samples of activated sludge fed with synthetic sewage were measured in an enclosed cell containing an oxygen electrode after a contact time of 3 hours. The test item was investigated at one (limit) concentration level of 1000 mg/L. The observed oxygen consumption rates consequently the specific respiration rates were in the range of the blank controls, no inhibitory effect of the test item was observed. Based on measured oxygen consumption values and calculated specific respiration rates it can be stated that the 3-hour EC10 and EC50 values of the test item are higher than 1000 mg/L.

Based on these data, the calculated EC10 and EC50 values of cesium were greater than 792 mg/L and the NOEC was 792 mg/L and for cesium sulphate the calculated values were as follows: EC10 and EC 50 >1077.6 mg/L and NOEC 1077.6 mg/L.