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Terbium trinitrate is registered as an intermediate under strictly controlled conditions for a tonnage inferior to 100 t/y. Therefore, the data requirement is to submit the available existing information. Rather than concluding on the sole basis of the available data on Hyalella azteca (see IUCLID section 6.1.3), it was preferred to follow a weight-of-evidence approach and to consider all the data available on the rare earth trinitrates family in order to apply a worst-case classification as a matter of precaution. As it can be evidenced from rare earth trinitrates that have been already tested, these ones are:

 

- Toxic to very toxic fish:

    > Lanthanum trinitrate: 96h-LC50 (Oncorhynchus mykiss) = 1.01 mg/L (Klimisch 1, key study)

    > Cerium trinitrate: 96h-LC50 (Oncorhynchus mykiss) = 0.3 mg/L (Klimisch 1, key study)

    > Praseodymium trinitrate: 96h-LC50 (Oncorhynchus mykiss) = 0.71 mg/L (Klimisch 3, supporting study*)

    > Neodymium trinitrate: 96h-LC50 (Oncorhynchus mykiss) = 2 mg/L (Klimisch 3, supporting study*)

    > Gadolinium trinitrate: 96h-LC50 (Oncorhynchus mykiss) = 0.93 mg/L (Klimisch 3, supporting study*)

    > Dysprosium trinitrate: 96h-LC50 (Oncorhynchus mykiss) = 2 mg/L (Klimisch 3, supporting study*)

    > Yttrium trinitrate: 96h-LC50 (Oncorhynchus mykiss) = 0.62 mg/L (Klimisch 1, key study) and 96h-LC50 (Oncorhynchus mykiss) = 2.3 mg/L (Klimisch 3, supporting study*)

 

N.B. Studies on praseodymium, neodymium, praseodymium, gadolinium, dysprosium and yttrium trinitrates legended with * did not include any analytical monitoring to investigate the stability of the test items in the test media. Precipitation of rare earths may have occurred; which could have led to an underestimation of the ecotoxicity. Therefore, the results should not be considered entirely reliable. However, as relatively important adverse effects were observed in these studies underestimating toxicity, they may be used as supporting studies.

 

- Harmful to toxic to daphnids:

    > Lanthanum trinitrate: 48h-EC50 (Daphnia magna) = 3 mg/L (Klimisch 1, weight-of-evidence)

    > Cerium trinitrate: 48h-EC50 (Daphnia magna) = 16 mg/L (Klimisch 1, key study)

    > Praseodymium trinitrate: 48h-EC50 (Daphnia magna) = 2 mg/L (Klimisch 1, key study)

    > Neodymium trinitrate: 48h-EC50 (Daphnia magna) = 8.1 mg/L (Klimisch 1, key study)

    > Gadolinium trinitrate: 48h-EC50 (Daphnia magna) = 2.9 mg/L (Klimisch 1, key study)

    > Yttrium trinitrate: 48h-EC50 (Daphnia magna) = 11.5 mg/L (Klimisch 1, key study)

Considering this pool of data, it was decided to apply the worst-case conclusion to terbium trinitrate and to consider it as very toxic to aquatic life. In spite of its Klimisch score of 3, the available data on Hyalella azteca (see IUCLID section 6.1.3) goes in the same direction by concluding that terbium trinitrate is very toxic to Hyalella azteca in soft water (7d-LC50 = 0.182 mg/L based on measured concentration). This further supports the decision to apply the worst-case conclusion. 

 

Toxicity to algae was not considered in this rationale based on the arguments provided in section 6.1.5.

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