Caesium iodide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

40.9 µg/L

Extrapolation method:

sensitivity distribution

PNEC freshwater (intermittent releases):

40.9 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

122.8 µg/L

Extrapolation method:

sensitivity distribution

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

100 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

3.92 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.392 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.196 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

PNEC_freshwater:

The comparison of ecotoxicological data from cesium hydroxide monohydrate and cesium iodide shows that the counter ion iodide triggers the toxicity. Therefore a very conservative approach using background data and not effect data from iodine was considered. 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 of up to 20 μg/L is reported. This concentration corresponds to 40.94 μg/L for CsI. Using a worst-case approach, the PNEC_freshwater for cesium iodide was thus set to 40.94 μg/L.

PNEC_marine water:

Equivalently to the approach described above for the derivation of the PNEC_ freshwater, the PNEC_marine water is set equal to the background concentration of iodine in marine water (60 μ/L). This concentration corresponds to 122.83 μg/L for CsI. Therefore, using the worst-case approach the PNEC_marine water for cesium iodide was set to 122.83 μg/L.

PNEC_intermittent releases:

The PNEC_intermittent releases was also set equal to the background concentration of iodine in the freshwater compartment (20 μ/L) (worst-case approach). Thus, the PNEC_intermittent releases for cesium iodide is 40.94 μg/L.

PNEC_STP:

The PNEC_STP was derived from results obtained in the “Activated Sludge, Respiration Inhibition Test” with cesium iodide. The test revealed a NOEC of 1000 mg/L. Therefore, an assessment factor of 10 was applied (CSA Guidance Document, Chapter R. 10, May 2008).

PNEC_freshwater sediment:

Typical background concentrations of iodine in the freshwater sediment compartment are reported to be 6 mg/kg. This great difference in the background levels of the freshwater compartment and the freshwater sediment compartment clearly reflects the distinctly lower toxicity potential of iodine in the sediment compartments, e.g. due to the degradation via microbial activity. Consequently, for the substance CsI the concentration of cesium itself is considered to trigger the toxicity in the sediment compartments. Therefore, the PNEC_freshwater sediment for CsI was derived using the equilibrium partitioning method (EPM) and the PNEC_freshwater of cesium (1 mg/L).

Parameter:

K_(susp- water) = 0.979

RHO_(susp) = 1150

Conversion factor (wwt -> dwt): 4.6

PNEC_freshwater sediment = (K_(susp-water)/ RHO_(susp))*PNEC_water * 1000

= (0.979/1150)* 1 mg/L *1000 = 0.851 mg/kg wwt

= 3.916 mg/kg dwt

This PNEC_freshwater water sediment calculated for CsI is well below the background concentration of iodine reported for freshwater sediment compartment (typically 6 mg/kg).

PNEC_marine water sediment:

In an analogous manner, the derivation of the PNEC_marine water sediment for CsI was performed using the equilibrium partitioning method (EPM) and the PNEC_marine water of cesium (0.1 mg/L).

Parameter:

K_(susp- water) = 0.979

RHO_(susp) = 1150

Conversion factor (wwt -> dwt): 4.6

PNEC_marine water sediment

= (K_(susp-water)/ RHO_(susp))*PNEC_ marine water * 1000

= (0.979/1150)* 0.1 mg/L *1000

= 0.0851 mg/kg wwt

= 0.3916 mg/kg dwt

This PNEC_marine water sediment calculated for CsI is well below the background concentration of iodine reported for the marine water sediment compartment (typically 3 - 4000 mg/kg).

PNEC_soil:

Equivalently to the approach described above, the derivation of the PNEC_soil for CsI was performed using the equilibrium partitioning method (EPM) and the PNEC_freshwater of cesium (1 mg/L).

Parameter:

K_(soil-water) = 0.295

RHO_(soil) = 1700

Conversion factor (wwt -> dwt): 1.13

PNEC_soil

= (K_(soil-water)/ RHO_(soil))*PNEC_water * 1000

= (0.295/1700)* 1 mg/L * 1000

= 0.1735 mg/kg wwt

= 0.1961 mg/kg dwt

This PNEC_soil calculated for CsI is well below the background concentration of iodine reported for the soil compartment (typically 0.5 - 20 mg/kg dwt).

For details on calculation please refer to the discussion and the attached document "CH337-00037_CsI_PNEC justification.pdf".

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

Conclusion on classification

Based on an acute toxicity test on daphnia magna the test item has to be classified as "very toxic to aquatic life (H400)" according to Regulation (EC) No 1272/2008 (CLP).