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Short-term toxicity

One reliable acute toxicity to fish study of Peither (2011) with a klimisch score of 1 is available. The 96-h acute toxicity to rainbow trout was studied under semi-static conditions according to the OECD guideline 203. The 96-h LC50 of 0.13 mg dissolved Ce/L (corresponding to 0.3 mg Ce(NO3)3/L) was obtained. Based on the results cerium trinitrate 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 acute studies were identified on the acute toxicity of cerium to aquatic invertebrates. Two of them (Bazin, 1995 and Bringman and Kühn, 1959), were given a reliability score of 3 and flagged as disregarded studies. The key study from Hefner (2014), was given a reliability score of 1. In the latter study Daphnia magna were exposed to cerium trinitrate under semi-static conditions according to the 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). Based on these results, cerium trinitrate is considered harmful to aquatic invertebrates.

Three algae growth inhibition studies are available. Two of them (Tai, 2010; Bringman and Kühn, 1959), were given a reliability score of 3 and flagged as supporting studies. The key study from Hefner (2013) was assigned a klimisch score of 2 because the results of this study are used for read-across purposes in this dossier. In this study, algae growth inhibition was investigated in a 72-h static test according to the OECD guideline 201 with the unicellular green algae Pseudokirchneriella subcapitata. The test substance was CeCl3. The growth rate-based 72-h EC50 and NOEC were 0.63 and 0.46 mg Ce/L, respectively (corresponding to 1.46 mg Ce(NO3)3/L and 1.07 mg Ce(NO3)3/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 to micro-organisms. A reliability score of 2 was assigned to the new study from Eisner (2013) which has been performed with the read-across substance CeCl3. This study was considered as key study. The study was run according to the OECD 209. The 3-hr NOEC and EC50 to activated sludge micro-organisms was 91 and 436 mg Ce/L (corresponding to 212 and 1015 mg Ce(NO3)3/L) respectively.

Long-term toxicity

In accordance with Column 2, specific rules for adaptation from Column 1, of REACH Annex IX, the long-term testing on daphnia and fish studies, listed under standard information requirements 9.1.5 and 9.1.6 respectively, do not need to be conducted as the chemical safety assessment concludes that the substance is of no immediate concern to the environment. The available data are adequate for classification and labelling purposes and PBT/vPvB assessment is not applicable for inorganic substances, so no further testing is required.

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