Cerium

Endpoint summary

Description of key information

LD50 oral, rat > 5000 mg/kg bw
LC50 inhalation, rat > 5.05 mg/L (4 hours)

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

5 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Dose descriptor:

LC50

Value:

5.05 mg/m³ air

Additional information

Acute oral toxicity:

Test Regulation, B.1 “Acute toxicity, oral” reads that the test substance is administered in a single dose by gavage using a stomach tube or a suitable intubation canula. Cerium metal presents sample preparation constraints due to the fact that cerium metal powder quickly oxidises under normal atmosphere. Therefore, studies to characterise the acute toxicity oral behaviour of cerium metal have been done on cerium-compounds with 3+ valency (i.e. cerium chloride, cerium carbonate), based on the read-across approach as explained in the CSR.

Acute inhalation toxicity:

Only dusty forms of a substance (never massive) could be of relevance for the inhalation exposure. Dusty forms of Ce however cannot be found under the normal atmosphere (see flammability properties), but only its oxidised form CeO2. According to published data (see literature above) CeO2 would be the form of cerium typically encountered in industrial exposures. Exposure to general population to CeO2 coming from the foreseen use of cerium metal as such or in an alloy, can be disregarded as irrelevant.

Therefore, read-across to CeO2 acute and chronic inhalation exposure (IUCLID5 endpoints 7.2.1 and 7.5.3) will be applied.

Acute dermal toxicity:

The foreseen test to study the acute dermal toxicity is not suitable for this sample, since it is not feasible to have cerium powder under normal atmosphere due to its flammable behaviour. Test Regulation B3, page 178: "When testing solids, which may be pulverised if appropriate, the test substance should be moistened sufficiently with water or, where necessary, a suitable vehicle to ensure good contact with the skin".

 

The oral and inhalation routes of exposure are more relevant as they have been already described in the Toxicological Review “Cerium oxide and Cerium compounds” – EPA/IRIS Sept 2009. Therefore, dermal acute toxicity information can be waived.

Justification for classification or non-classification

As for the acute oral toxicity, one Klimish 2 study on cerium carbonate, selected as the key study, gave a value of LD50 > 5000 mg/kg bw. No classification in therefore justified.

As for the acute inhalation toxicity, one klimish 1 study on cerium oxide, showed a value of Lc50 > 5,05 mg/L air. No classification is therefore justified.