Caesium carbonate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

HYPOTHESIS FOR THE ANALOGUE APPROACH
Cesium carbonate completely dissociates in water forming cesium cation and the corresponding carbonate anion. Thus, cesium salts with different anion moieties were found to be suitable candidates for read-across. (Eco)toxicological properties were extrapolated to different endpoints by using the lowest effect concentration.
For further information, please refer to the read-across justification in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

795 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for Cs

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 795 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for Cs

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 795 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for Cs

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

974 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for Cs2CO3

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 974 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for Cs2CO3

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 974 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for Cs2CO3

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Description of key information

A toxicity study to microorganisms with cesium carbonate 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 carbonate the calculated values were as follows: EC10 and EC 50 >974 mg/L and NOEC 974 mg/L.
Due to the ratio of the molecular weight of cesium atoms and counter ion the values for cesium carbonate are slightly below the limit dose of 1000 mg/L. However, it is assumed that this has no impact on the regulatory assessment of the test result.

Key value for chemical safety assessment

EC50 for microorganisms:

974 mg/L

EC10 or NOEC for microorganisms:

974 mg/L

Additional information

A toxicity study to microorganisms with cesium carbonate is not available. Consequently, read-across was applied using study 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 795 mg/L and the NOEC was 795 mg/L and for cesium carbonate the calculated values were as follows: EC10 and EC 50 >974 mg/L and NOEC 974 mg/L.

Due to the ratio of the molecular weight of cesium atoms and counter ion the values for cesium carbonate are slightly below the limit dose of 1000 mg/L. However, it is assumed that this has no impact on the regulatory assessment of the test result.