Dineodymium tricarbonate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

2 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

1 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.2 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

100 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Conclusion on classification

Solubility: The substance has a low water solubility of 3.65 mg/L.

Acute toxicity to aquatic organisms: Acute data on the three trophic levels (fish, Dapnia and algae); all show an absence of toxicity. In the case of fish and algae results read-across from cerium carbonate the EC50values are greater than the initial loading rate of 100 mg/L. For these studies Water Accomodated Fraction (WAF) methodology was used to prepare a super-saturated solution of test item: an initial loading rate of 100 mg/L was added and then stirred during a period pre-determined to allow a maximum solubility of the test item. At the end of the stirring phase, a sedimentation period was conducted. Then, the supernatant was collected and considered as a supersaturated solution containing the maximum concentration of dissolved test item. Test organisms were therefore exposed to the substance up to its solubility limit into water. In the case of the acute toxicity to Daphnia study the test results are quoted in terms of mean measured concentration based on ICP-MS analysis of neodymium. In each study case it appears that the maximum solubility limits were lower than those obtained during the water solubility test using column elution method. rved this. This is considered to be the the water media being different between water solubility test (Milli-Q-water) and ecotoxicological studies (media containing analytical grade salts). As a result of this during the ecotoxicity tests, the test item, dineodymium carbonate, can complex with salts from the test medium; resulting in a reduced concentration of dissolved test item. In summary, it is considered that the maximum solubility limit was attained during the ecotoxicity studies and that since no adverse effects were observed up to this value dineodymium carbonate has been shown not to be acutely harmful to aquatic organisms.  

Biodegradation: Biodegradation tests are not applicable to inorganic substances. Abiotic and biotic degradation will not occur.

Bioaccumulation: No bioaccumulation data are available on insoluble salts of neodymium. However, literature data (Bioconcentration and elimination of five light rare earth elements in carp, Hao et al, 1996, as summarised in Section 5.3.1) provide data on the soluble salt neodymium nitrate. These data show that the highest potential for bioaccumulation is within the internal organs of carp (highest BCF = 634 after 29 days) but that BCF values begin to decline after this time, reducing to 451 at 43 days (the end of the study period). Elimination is considered to be via a first-order process and the half-life of neodymium in internal organs is given as 6.30 days. By analogy to neodymium carbonate it can be predicted that dineodymium tricarbonate is unlikely to be bioaccumulative. Furthermore, being poorly water soluble this substance can be expected to be less bioavailable than soluble salts for bioaccumulation.  

Chronic toxicity results: A chronic test on daphnids has been read-across from cerium carbonate. This was performed using WAF methodology. Based on the same reasoning reported above for the acute fish and algal inhibition tests tests, it can be concluded that the maximum concentration of dissolved test item was tested. As no chronic effect was observed at the highest loading rate, cerium carbonate does not show any chronic effect up to its solubility limit into water.  

Conclusion: In the absence of toxicity to aquatic organisms in acute and chronic studies in which the substance was tested up to its maximum dissolved concentration and in the absence of a potential to bioaccumulate it is concluded that classification of the substance for environmental effects is not required.

PBT assessment: According to the Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT assessment, “the PBT and vPVB criteria of Annex XIII to the regulation do not apply to inorganic substances”. Therefore it is not considered necessary to undertake further assessment of PBT properties.