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Short-term toxicity to aquatic invertebrates

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Description of key information

In the 48-hour static acute toxicity test to Daphnia magna with cesium iodide the 48-hour EC50 value was determined as 0.51 mg/L (Probit analysis). The overall NOEC was determined to be 0.175 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
0.51 mg/L

Additional information

The purpose of this study was to evaluate the influence of the test item cesium iodide on the mobility respectively survival of Daphnia magna. Young Daphnia were exposed to test water at a range of test item concentrations for 48 hours. The main test was performed in a static system because the test item was stable for 48 hours. Five concentrations of cesium iodide and a untreated control were tested in the main study. The concentrations were: 0.0875; 0.175; 0.35; 0.7 and 1.4 mg/L. The cesium iodide content was determined in the test water (ISO Medium) by titration with a standard 0.001 M Sodium thiosulfate solution using starch indicator in acid media at the start and at the end of the test. The three highest test item concentrations of 0.35; 0.7 and 1.4 mg/L could be measured by the described analytical method. The analytically determined mean test item concentrations in the analysed test media varied in the range from 100 % to 102 % of the nominal value at the start of the study and from 99 % to 108 % at the end of the study. The deviation of the measured concentrations from the nominal values was lower than 20 %. Therefore, all reported biological results are related to the nominal concentrations applied in the test. The highest concentration tested without toxic effects after the exposure period of 48 hours, the 48h-NOEC, as well the 48h-EC0 of cesium iodide to Daphnia magna was determined to be 0.175 mg/L. 5 % mortality was observed at the concentration of 0.175, however this rate was within the assay acceptance range; therefore the observed immobilisation was not evaluated as an effect. The test item concentrations of 0.35 and 0.7 mg/L caused 30 and 65 % immobilization of the Daphnids, respectively. At 1.4 mg/L 95 % immobilization could be observed. The immobilisation observed in the concentration range of 0.35–1.4 mg/L test item concentration was significantly different from the control (Dunnett’s Test, Statistical Software Program TOXSTAT). The 48h-LOEC was 0.35 mg/L, while the 48h-EC50 was calculated to be 0.51 mg/L.

In the 48-hour static acute toxicity test to Daphnia magna with cesium iodide the 48-hour EC50 value was determined as 0.51 mg/L (Probit analysis). The overall NOEC was determined to be 0.175 mg/L.