Cerium tetranitrate

Short-term toxicity to aquatic invertebrates

Description of key information

The key study of Hefner (2014b), in which Daphnia magna was exposed for 48 h to cerium tetranitrate, yielded a 48-h EC50 of > 36 mg Ce/L (corresponding to > 100 mg Ce(NO3)4/L). No immobilisation was observed in this limit test at a nominal loading rate of 100 mg Ce(NO3)4/L. Therefore, the substance can be considered not to be toxic to aquatic invertebrates.

Additional information

One reliable study has been identified to cover this endpoint. This study performed by Hefner (2014b) was a 48-h semi-static acute toxicity study with Daphnia magna in which cerium tetranitrate was used as test item. In a limit test at a nominal loading rate of 100 mg/L anhydrous cerium tetranitrate no immobilised daphnids were observed after 48 h of exposure. Dissolved cerium concentrations were analytically monitored during the test and were between 0.028 and 0.0684 mg Ce/L. Due to the absence of adverse effects, the 48-h EC50 was expressed based on nominal concentrations and was > 36 mg dissolved Ce/L (corresponding to > 100 mg Ce(NO3)4/L). These results are considered as the key values.

As explained in the endpoint summary for acute toxicity to fish, any observed toxicity can reasonably be expected to be due to bioavailable Ce+3, since Ce+4 species are not stable in solution. Therefore, a tetravalent cerium compound can be expected to cause toxicity to the test species under consideration if, under similar conditions in the same test medium (to guarantee similar Ce+3 speciation), dissolved cerium concentrations higher than those causing toxicity in tests with trivalent cerium compounds can be reached upon addition of the limit nominal test dose of 100 mg/L. In the case of cerium tetranitrate, dissolved cerium concentrations were not high enough, when compared to the 48-h EC50 value obtained for cerium trinitrate (i.e. 6.9 mg Ce/L; Hefner, 2014e). Since the conditions of the test (e.g., pH 6.0) were selected in favor of maximal dissolution of cerium in the test medium, it can safely be concluded that cerium tetranitrate is not expected to be toxic to aquatic invertebrates at environmentally relevant conditions.

Further, a similar result was obtained for cerium ammonium nitrate (also a tetravalent cerium compound) (Hefner, 2014d), supporting the read across of the acute fish toxicity test with cerium amonium nitrate to cover the acute fish toxicity endpoint for cerium tetranitrate.

References not included in this dossier:

- Hefner N, 2014d. Cerium ammonium nitrate: Acute toxicity to Daphnia magna in a 48-hour immobilization test. Harlan Laboratories Ltd., Zelgliweg 1, 4452 Itingen, Switzerland. Report no. D60755. Owner company: Treibacher Industrie AG.

- Hefner N, 2014e. Cerium trinitrate: Acute toxicity to Daphnia magna in a 48-hour immobilization test. Harlan Laboratories Ltd., Zelgliweg 1, 4452 Itingen, Switzerland. Report no. D60722. Owner companies: Treibacher Industrie AG, AS Molycorp Silmet, Albemarle, Neo Performance Materials (Europe), MEL Chemicals, Rhodia Operations.