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Additional information

Short-term toxicity

One reliable study was identified on the acute toxicity of cerium to fish (Peither, 2011). This key study, which was performed using Ce(NO3)3, was assigned a reliability score of 2 because the results are used for read across purposes in this dossier. Rainbow trout were observed under semi-static exposure conditions for 96 h according to OECD guideline 203. The 96-h LC50 was determined to be 0.13 mg dissolved Ce/L (corresponding to a 96-h LC50 of 0.3 mg Ce(NO3)3 and 0.23 mg CeCl3/L). Based on these results CeCl3 is considered to be very toxic to fish. Two other studies from Gard (1990) and Bazin (1996) were assigned a Klimisch score of 3, the study from Gard was considered as a supporting study, the study from Bazin however was disregarded as no analytical measurements of the test concentrations were performed which may have led to an underestimation of the toxicity of cerium.

Three studies were identified on the acute toxicity of cerium to aquatic invertebrates. Two of them (Bazin, 1995; Bringman and Kühn, 1959), were assigned a reliability score of 3. The key study from Hefner (2014), which was performed using Ce(NO3)3, was assigned a reliability score of 2 because the results of this study are used for read across purposes in this dossier. In this study Daphnia magna juveniles were exposed to cerium under semi-static conditions according to OECD guideline 202. The 48-h EC50 was calculated based on mean measured concentrations and was 6.9 mg Ce/L (corresponding to 16 mg anhydrous Ce(NO3)3/L or 12 mg CeCl3/L). Based on these results, CeCl3 is considered harmful to aquatic invertebrates.

Three algal growth inhibition studies are available. Two of them (Tai et al., 2010; Bringman and Kühn, 1959) were assigned a reliability score of 3 and flagged as supporting studies.

The key study from Hefner (2013) was assigned a Klimisch score of 1 and selected as key study. In this study, algal growth inhibition was studied in a 72-h static test according to OECD guideline 201 with the unicellular green alga Pseudokirchneriella subcapitata. The test substance was CeCl3. The growth rate-based 72-h EC50 and NOEC were determined to be 0.63 and 0.46 mg Ce/L, respectively (corresponding to 1.1 and 0.81 mg CeCl3/L, respectively) and were based on measured dissolved Ce levels at the start of testing. Observations during the test indicated that the observed effects on algal growth were concurrent with phosphate depletion. Model calculations (Visual MINTEQ v3.0) indeed confirmed that whenever phosphate is in excess of cerium (i.e., at the lowest test concentrations), all cerium is precipitated from the test solution, whereas when cerium is in excess of phosphate (i.e., at the higher test concentrations), all phosphate is precipitated from the test solution. The latter results in phosphate deprivation effects in the algae. Therefore, the observed algal growth inhibition was due to an indirect effect instead of resulting from direct cerium toxicity. This problem cannot be resolved by adjusting the test setup and therefore no further testing will be performed and the results of the algal growth inhibition studies will not be taken forward to PNEC derivation.

Four studies were identified on the toxicity of cerium to microorganisms. A reliability score of 1 was assigned to the study performed by Eisner (2013). This study was considered as key study. The study was performed according to OECD guideline 209 using CeCl3 as test substance. The 3-h NOEC and EC50 for activated sludge microorganisms were determined to be 91 and 436 mg Ce/L, respectively (corresponding to 160 and 767 mg CeCl3/L).

Long-term toxicity

In accordance with Column 2 of REACH Annex IX, long-term tests on aquatic invertebrates and fish, listed under standard information requirements 9.1.5 and 9.1.6 respectively, do not need to be conducted because the chemical safety assessment concludes that the substance is of no immediate concern to the environment. Further, the available acute data are adequate for classification and labelling purposes, and PBT/vPvB assessment is not applicable for inorganic substances. In conclusion, no further testing is required.

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