Caesium iodide

Long-term toxicity to aquatic invertebrates

Description of key information

A chronic daphnia toxicity study with cesium iodide is not available. Consequently, read-across was applied using study results from the structural analogue cesium hydroxide monohydrate. Moreover, 
Under the conditions of this chronic daphnia toxicity study the observed endpoints related to reproduction for the effect of cesium hydroxide monohydrate were the following: 21d NOEC: 15.8 mg/L; 21d LOEC: 30.0 mg/L; 21d EC50: > 15.8 mg/L. All reported biological results are related to the nominal concentrations. 
Based on these data, the calculated 21d-NOEC for cesium iodide was 24.5 mg/L, the 21d-EC50 > 24.5 mg/L and the LOEC = 46.4 mg/L.
In addition to this data the calculated 21d-NOEC for cesium was 12.5 mg/L, the 21d-EC50 > 12.5 mg/L and the LOEC = 23.7 mg/L.
In addition, iodine and iodine compounds are considered to have a significant toxicity towards the aquatic compartment. However, iodine and iodine compounds, are omnipresent distributed in the environment, created by the natural cycle of iodine species in the environment. A lot of reasearch has been made on the environmental fate and distribution of iodine and iodine compounds.  The Swedish competent authority published an evaluation report on iodine. In this report, which refers to open literature data, e.g. overview articles, data on environmental background concentration of iodine are available. For the freshwater compartment (river and lake) a background concentration of iodine up to 20 μg/L is reported. This concentration corresponds to 40.94 μg/L for CsI. Therefore, for the PNEC derivation the worst-case approach using these iodine background data was applied (see IUCLID summary section “Ecotoxicological Information”).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

24.5 mg/L

Additional information

For the endpoint long-term toxicity to invertebrates no study on cesium iodide was performed since the data base on the cesium as well as on the iodide ion is sufficient. On the one hand, read-across data on the structural analogue cesium hydroxide monohydrate were used to fill the data gap. In addition, iodine and iodine compounds are considered to have a significant toxicity towards the aquatic compartment. However, iodine and iodine compounds, are omnipresent distributed in the environment, created by the natural cycle of iodine species in the environment. A lot of reasearch has been made on the environmental fate and distribution of iodine and iodine compounds. The Swedish competent authority published

an evaluation report on iodine. In this report, which refers to open literature data, e.g. overview articles, data on environmental background concentration of iodine are available. For the freshwater compartment (river and lake) a background concentration of iodine up to 20 μg/L is reported. This concentration corresponds to 40.94 μg/L for CsI. Therefore, for the PNEC derivation the worst-case approach using these iodine background data was applied (see IUCLID summary section “Ecotoxicological Information”).

The chronic daphnia toxicity study with the structural analogue cesium hydroxide monohydrate used for read-across revealed the following results. A semi-static Daphnia magna reproduction test was performed according to OECD Guideline 211 and EU Method C.20. At this method Daphnia magna, aged lower or equal 24 h at the beginning of the test, are exposed to a range of cesium hydroxide monohydrate under defined conditions over a period of 21 days. In the definitive test the nominal concentrations were as follows: 2.3, 4.4, 8.3, 15.8 and 30 mg/L. The performed parallel running analytical determinations confirmed that the test item concentrations remained within the range of ±20 % of the nominal and of the initial concentrations (varied between 93 and 109 per cent of the nominal concentration); therefore all of the results are based on the nominal test item concentrations. In the main test the mean number of offspring produced per animal was slightly lower (100.1, 106.5 and 109.1) in concentrations of 2.3, 4.4 and 8.3 mg/L and somewhat higher (124.2) at the concentrations of 15.8 mg/L. Due to the 100 % mortality in parent animals at the highest concentration of 30 mg/L, results of this concentration is excluded from data analysis. Correspondingly the 21-day NOEC related to reproduction was determined to be 15.8 mg/L and the LOEC as 30 mg/L. At the highest tested concentration of 30 mg/L the produced offspring were excluded from data analysis (because all of parent animals were died by the end of the experiment) and the mean number of offspring produced in the next lower concentration (15.8 mg/L) was higher than produced in the control (i.e. NOEC), therefore the obtained results were not sufficient for an exact EC50 value estimation. A Probit analysis was not performed from the available data. The 21-day EC50 was determined to be higher than 15.8 mg/L. Based on these data, the calculated 21-day NOEC for cesium iodide was 24.5 mg/L, the 21-day EC50 > 24.5 mg/L and the LOEC = 46.4 mg/L. In addition to this data the calculated 21-day NOEC for cesium was 12.5 mg/L, the 21 -day EC50 > 12.5 mg/L and the LOEC = 23.7 mg/L.

For detailed information on the read-across strategy please refer to the read-across justification in IUCLID section 13.