Gadolinium trinitrate

Endpoint summary

Description of key information

All available existing information on the toxicity of gadolinium trinitrate to aquatic organisms, complemented with available data for the related substance gadolinium trichloride (which is a water soluble gadolinium substance with expected similar behaviour as gadolinium trinitrate), is presented in this dossier. Most of the available data received a Klimisch score of 3 or 4, the reliability score of 3 being assigned because of methodological deficiencies, such as experimental conditions or an experimental setup that might have been resulted in (slight) underestimation of toxicity. In spite of this, adverse effects were commonly observed in aquatic toxicity studies, which is confirmed by the Klimisch 1 study performed with Daphnia magna (48-h EC50 = 2.9 mg Gd(NO3)3/L, Ablitt, 2018). Therefore, it was decided to consider not only the available data included in this dossier, but also data available on other rare earth trinitrates in order to apply a worst-case classification as a matter of precaution. Other rare earth trinitrates that have already been tested have been observed to be:

- Toxic to very toxic to fish:

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

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

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

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

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

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

N.B. Studies on praseodymium, neodymium, 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, they may be used as supporting studies or in a weight of evidence approach.

- Harmful to toxic to daphnids:

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

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

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

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

> Yttrium trinitrate: 48-h 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 gadolinium trinitrate and to consider it as very toxic to aquatic life. In spite of their Klimisch scores of 3, the available data on Oncorhynchus mykiss (Bazin, 1997) and Hyalella azteca (Borgmann et al., 2005) point in the same direction by concluding that gadolinium trinitrate is very toxic to these two species. This further supports the decision to apply the worst-case conclusion.

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