Neodymium trinitrate

Ecotoxicological Summary

Conclusion on classification

Acute toxicity:

 

Short-term toxicity studies are available on fish and daphnids, with L/EC50 ranging from 1 to 10 mg/L, meaning that neodymium trinitrate is toxic to these species. No data is available on algae for the reasons explained in IUCLID section 6.1.5. Briefly, all available data from algal growth inhibition studies performed with rare earth compounds have provided evidence that adverse effects on algal growth are due to phosphate deprivation as a result of the strong interaction of rare earths with phosphate rather than a direct toxic effect as a result of exposure to bioavailable dissolved rare earths. For this reason, it was concluded that there is no scientific added value in performing further algal toxicity studies with rare earth compounds. As a result, the environmental hazard classification is based on data available on the two other trophic levels (i.e. fish and daphnids).

 

It has to be noticed that the available acute toxicity study on fish was judged not entirely reliable as performed in conditions minimizing the toxicity. Indeed, precipitation cannot be ruled out as no analytical monitoring was performed, and based on the knowledge aquired from the water solubility study (see IUCLID section 4.8), solubility is known to be significantly decreased when the pH is adjusted to environmental values (i.e. pH=6.98). In spite of these conditions which could have led to an underestimation of toxicity, some adverse effects were observed, giving a 96h-LC50 of 2 mg/L, thus relatively close to the 1-mg/L acute classification threshold under CLP. As a matter of safety, it was thus preferred not to rule out these results.

 

This precautionary principle is further supported by data available on other rare earth trinitrates. Indeed, in more recent acute toxicity studies in fish with analytical monitoring and taking care of applying a design to maintain dissolved rare earth concentrations as much as possible, the 96h-LC50 were below 1 mg/L (but still above 0.1 mg/L; e.g. cerium trinitrate, lanthanum trinitrate, yttrium trinitrate, erbium trinitrate).

 

Based on the above considerations, it was found appropriate to classify neodymium trinitrate in aquatic acute toxicity category 1 (H400) with an acute M factor of 1.

 

Chronic toxicity:

 

Long-term toxicity studies are available on fish and daphnids. In fish, the endpoint the most sensitive to exposure to neodymium trinitrate was the post-hatching survival with a 33d-LC10 of 0.081 mg/L. In daphnids, reproduction and body length were equally sensitive to exposure to neodymium trinitrate with a 21d-EC10 of 0.18 mg/L for both endpoints. No data is available on algae for the reasons explained in IUCLID section 6.1.5. and above summarized.

 

Considering the LC10 value obtained in the most sensitive species (i.e. fish) and in the absence of data on the rapid environmental transformation of neodymium, neodymium trinitrate has to be classified in aquatic chronic toxicity category 1 (H410) with a chronic M factor of 1.