Reaction mass of cerium dioxide and lanthanum oxide and lanthanum fluoride

Endpoint summary

Description of key information

- Skin irritation: not irritating (reaction mass or its main constituents)
- Eye irritation: minimally to slightly irritating, not resulting in classification (main constituents)

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

A skin irritation study (Klimisch 2) is available on the reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride. No eye irritation study using the reaction mass is available. However, further information on skin and eye irritation potential are available on the constituents of the reaction mass, Cerium dioxide, Lanthanum oxide as well as Cerium trifluoride, a lanthanide salt closely related to Lanthanum fluoride. As these constituents showed similar physicochemical, toxicological, ecotoxicological and environmental properties, results of studies performed on all constituents are used as supporting studies (skin irritation) or weight of evidence (eye irritation).

Skin irritation

In a primary dermal irritation study (IFREB, 1980; Klimisch 2) used as a key study, 6 New Zealand White rabbits received a dermal dose of 0.5 g of reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride, put on moistened gauze with 0.5 mL water, on intact and abraded skin sites under an occlusive dressing for a period of 24 hours. Erythema and oedema scores were measured 1 and 48 hours after patch removal and primary cutaneous index was calculated. No sign of dermal irritation was observed for intact skin site of the 6 rabbits at both reading times while slight erythema but no oedema was observed in 2/6 animals 1 hour after patch removal for the abraded skin site. Forty eight hours after patch removal, signs of irritation had subsided. Therefore no classification for skin irritation is warranted.

In addition, the skin irritation potential of cerium dioxide, lanthanum oxide and cerium trifluoride was tested separately in vivo. Following dermal application of cerium dioxide under semi-occlusive dressing for 4 hours on 3 male New-Zealand White rabbits, no signs of cutaneous irritation was observed 1, 24, 48 and 72 hours following dressing removal (Institut Français de Toxicologie, 1983). Similarly, cerium dioxide, lanthanum oxide or cerium trifluoride induced no signs of dermal irritation 24 and 72 hours after 24-hour occlusive application to one intact and one abraded skin site of 6 New-Zealand White rabbits (Lambert et al., 1993). All these reliable data (Klimisch 2) on the main constituents of the reaction mass or their analogs, the results of which corroborated testing results on the reaction mass itself, were used as supporting studies.

Eye irritation

In the absence of a specfic eye irritation study using the reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride, reliable (Klimisch 2) in vivo data on cerium dioxide, lanthanum oxide and cerium trifluoride were used as weight of evidence.

In a primary eye irritation study (Institut Français de Toxicologie, 1983), 3 male rabbits were observed for up to 7 days following a single conjunctival instillation of cerium dioxide in unwashed eyes. Signs of minimal ocular irritation were noted, mainly 1 hour after instillation, and had subsided by day 3. These changes were likely related to the mechanical irritation properties of cerium dioxide as a solid powder. These observations were consistent with the other study (Lambert et al., 1993) where cerium dioxide was found minimally irritating to both washed and unwashed rabbit eyes. However, due to their low intensity and short duration, the ocular changes did not warrant classification of cerium dioxide for eye irritation according to the EU classification criteria.

The eye irritation properties of lanthanum oxide and cerium trifluoride were also tested in vivo. Following instillation of 0.1 g in the left eye of 6 New-Zealand White rabbits, lanthanum oxide and cerium trifluoride were found slightly or minimally irritating to both washed and unwashed rabbit eyes, respectively, according to the US criteria. However, no classification is warranted based on the low intensity and short duration of the findings, according to the EU classification criteria.

Therefore, considering in vivo eye irritation data on the main constituents of the reaction mass or their analogs, no classification for eye irritation is warranted for the reaction mass itself.

Skin and Eye irritation	Reaction mass	Cerium dioxide	Lanthanum oxide	Lanthanum fluoride
Skin irritation	Not irritating	Not irritating	Not irritating	Not irritating (by analogy with Cerium trifluoride)
Eye irritation	-	Not irritating	Not irritating	Not irritating (by analogy with Cerium trifluoride)

Justification for classification or non-classification

Based on the classification criteria of Annex VI Directive 67/548/EEC or UN GHS/EU CLP, the absence of dermal irritation and the low magnitude and rapid reversibility of ocular irritation in rabbits resulted in no classification of reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride for skin and eye irritation. These results are supported by those observed in the individual constituents or their analogs.