Cerium tetranitrate

Endpoint summary

Description of key information

Skin irritation / corrosion:
A 'weight-of-evidence' approach is used to cover this endpoint.
Based on the determination of the pH of 0.68 and the acidic reserve of 20, a solution containing 10% of cerium tetranitrate was considered to be corrosive (Rhodia Operations, 2012). This study was scored Klimisch 2.
The concentration of nitric acid in cerium tetranitrate solution is > 5%. Nitric acid concentration ranges of 5 to 20% lead to classification as corrosive 1B and concentration ranges of 20 - < 65% lead to classification as corrosive 1A.
Two studies were performed with cerium tetranitrate solution in rabbits and revealed contradictory results:  irritant according to the criteria of Directive 67/548/EEC (de Jouffrey, 1998) versus necrosis  - corrosive to the skin (Michot, 1998). One study was scored as K2 and the other as K4. This one was disregarded. In both studies no information was given on the amount of test substance in the test solution.
Based on all the abovementioned information cerium tetranitrate is considered to be corrosive to skin.
Eye irritation: 
No further testing is needed for this endpoint as the substance is considered corrosive to skin, according to Column 2, Annex VII, section 8.2 of Reach Regulation. 

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin Irritation:

A 'weight-of-evidence approach is used to cover this endpoint.

The pH of a 10% cerium tetranitrate solution was determined electrochemically at 20°C with a calibrated pH meter in a K2 study

(Rhodia Operations, 2012)

A pH value of 0.68 was determined. In addition, the acidic reserve of the solution was determined via titration of a 1 mol/L NaOH solution, which was required to achieve a pH of 4 of a 10% solution (or slurry) at 20°C. Based on the pH value of 0.68 and the acidic reserve of 20, the calculation for corrosivity was -0.987. As in this test the calculation pH - 1/2 acid reserve was lower than -0.5, the solution containing 10% of cerium tetranitrate was considered to be corrosive, and therefore, cerium tetranitrate was considered to be corrosive.

In a K2 study (de Jouffrey, 1998) performed according to OECD 404 and in compliance with GLP regulations, the test item was a solution of cerium tetranitrate but no information was given on the amount of this substance in the test solution. The test solution was applied to the intact shaved skin of a first New Zealand White rabbit for 3 minutes using a semi-occlusive dressing.

As no cutaneous reactions were observed after 1 hour, 24, 48 and 72 hours after removal of the dressing, the substance was applied to a different flank of the rabbit for 4 hours. The substance was also applied for 4 hours to other two additional rabbits. The skin of these three animals was examined approximately 1 hour, 24, 48 and 72 hours after removal of the dressing. Thereafter observations were done daily up to 14 days after removal of the dressing. After a 4-hour exposure (three animals), a very slight or well-defined erythema (grade 1 or 2) was recorded in all animals from day 1 up to day 3, 8 or 10. A slight oedema (grade 2) was noted in one animal between days 3 and 7. A yellow colouration of the skin was observed in all animals and dryness of the skin was recorded in two animals, from day 8 or 9 up to day 13 or 15. Under the conditions of the test, the Cerium tetranitrate solution was observed to be irritant when applied topically to rabbits (according to the criteria of Directive 67/548/EEC). However, according to the criteria of the CLP Regulation, the substance should not be classified for irritation to the skin.

A second study (Michot, 1998) was also identified. This study lacked of some information that made possible the evaluation of the reliability of the study and therefore it was considered K4 study and disregarded. In this study the substance was classified as C R34 under DSD. No information was given on the amount of test substance in the test solution in this study.

Finally, there is evidence that the concentration of nitric acid in cerium tetranitrate solution is > 5%. Nitric acid concentration ranges of 5 to 20% lead to classification as corrosive 1B and concentration ranges of 20 - < 65% lead to classification as corrosive 1A. In both case the substance is considered to be corrosive.

Summarising, the acidic-alkaline reserve and the pH were determined in a K2 study (Rhodia Operations, 2012). The pH resulted to be 0.68 and the acidic reserve 20. Therefore the substance was considered to be corrosive. Two studies were performed with cerium tetranitrate solution in rabbits and revealed contradictory results: irritant according to the criteria of Directive 67/548/EEC (de Jouffrey, 1998) versus necrosis - corrosive to the skin (Michot, 1998). The first study was scored as K2 for reliability and the second as K4. This one was disregarded. In both studies no information was given on the amount of test substance in the test solution.

The concentration of nitric acid in cerium tetranitrate solution is > 5%. Nitric acid concentration ranges of 5 to 20% lead to classification as corrosive 1B and concentration ranges of 20 - < 65% lead to classification as corrosive 1A. In both case the substance is considered to be corrosive. Taking into consideration all the information here above and applying a 'weight of evidence' approach, further testing seems inappropriate and that due to the presence of nitric acid.

Eye irritation:

No further testing is performed on eye irritation. According to the REACH Regulation (Annex VII, 8.2, Column 2), as the substance is considered corrosive to skin, the study does not need to be conducted if the substance is classified as corrosive to the skin.

Justification for selection of skin irritation / corrosion endpoint:
One study cannot be selected as the endpoint is covered using a 'weight-of-evidence' approach

Justification for selection of eye irritation endpoint:
No further testing needed, as the substance is considered corrosive to skin.

Effects on skin irritation/corrosion: corrosive

Justification for classification or non-classification

The pH of the 10% cerium tetranitrate solution was determined to be 0.68. The acidic reserve was determined to be 20 and the calculation for corrosiveness was -0.987. Based on the formula pH - 1/2 acid reserve < -0.5, cerium tetranitrate was considered to be corrosive. In addition, the concentration of nitric acid in cerium tetranitrate solution is > 5%. Nitric acid concentration ranges of 5 to 20% lead to classification as corrosive 1B and concentration ranges of 20 - < 65% lead to classification as corrosive 1A.

No further testing was performed related to eye irritation. It should be noted that if a substance or mixture is classified as Skin corrosive Category 1 then serious damage to eyes is implicit. Therefore, the substance is classified for irreversible effects on the eye (category 1).