Reaction mass of cerium dioxide and lanthanum oxide and lanthanum fluoride

Endpoint summary

Description of key information

LD50 oral, rat > 2000 mg/kg bw (Reaction mass) - LD50 oral, rat > 5000 mg/kg bw (cerium dioxide, lanthanum oxide and cerium trifluoride)
LC50 inhalation, rat > 5.05 mg/L (cerium dioxide)
LD50 dermal, rat > 2000 mg/kg bw (cerium dioxide)

Additional information

Acute toxicity: Oral

One key study was identified on the reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride (Klimisch 1). The reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride has been tested for acute oral toxicity in Sprague Dawley rats, according to O.E.C.D. guideline Nb.423 and in compliance with Good Laboratory Practice. The test item was prepared in 0.5% methylcellulose and was administered once by oral route (gavage) to a group of three fasted female rats at a dose level of 2000 mg/kg. As no death occurred in the first groups the results were confirmed in 3 other females treated following the same experimental conditions. Clinical signs, mortality and body weight gain were checked for a period of up to 14 days after the single administration. All animals were subjected to necropsy. No deaths occurred and no clinical signs were observed in this study. Body weight gain was not affected by treatment. At necropsy, macroscopic examination revealed no abnormality .

 

As the minimal lethal dose was found to be higher than 2000 mg/kg, no classification for acute oral toxicity is warranted.

Further information on acute oral toxicity are also available on the main constituents of the reaction mass, Cerium dioxide, Lanthanum oxide as well as Cerium trifluoride, a lanthanide salt closely related to Lanthanum fluoride. As these constituants showed similar physicochemical, toxicological, ecotoxicological and environmental properties, results of studies performed on all constituents are used as supporting studies.

By oral route, the LD50 of cerium dioxide in rats was higher than 5000 mg/kg bw, as confirmed by two distinct studies (Institut Français de Toxicologie, 1983; Lambert et al., 1993), therefore warranting no classification. For lanthanum oxide, the oral LD50 -value in Sprague-Dawley rats was > 5000 mg/kg bw (Lambert et al., 1993). Cerium trifluoride was also assayed for its oral acute toxicity and showed a LD50 -value in Sprague-Dawley rats > 5000 mg/kg bw (Lambert et al., 1993). This is corroborated by the results of a previous study in Sprague-Dawley rats where the oral LD0 of cerium trifluoride was > 2000 mg/kg (Guillot, 1987).

Acute toxicity: Inhalation

No study is available for the reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride. The data on the cerium dioxide main constituent of the reaction mass are considered in a weight-of evidence approach to conclude on the acute inhalation toxicity of the reaction mass of Cerium dioxide, Lanthanum oxide and Lanthanum fluoride.

Regarding cerium oxide, 2 acute inhalation studies (with Klimisch 1 reliability score) were performed according to OECD guideline and in accordance with GLP. In both studies, rats were exposed to cerium dioxide at 5.05 mg/L (RCC, 1993; nose only exposure) and 2.01 mg/L, the maximum technically administrable concentration (Institut Français de Toxicologie, 1983; whole body exposure) for 4 hours. No mortality occured in both studies, therefore warranting no classification.

No acute inahlation toxicity data were available for Lanthanum oxide or Lanthanum fluoride.

An acute inhalation study on reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride is therefore not regarderd as scientifically necessary according to section 1 of Reach Annex XI and is not recommended under animal protection considerations.

Acute toxicity: Dermal

No study is available for the reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride. Based on similar properties of cerium dioxide as compared to reaction mass of Cerium oxide and Lanthanum oxide and Lanthanum fluoride, a study on acute dermal toxicity performed with cerium dioxide is considered as a key study to conclude on the acute dermal toxicity of the reaction mass of Cerium oxide and Lanthanum oxide and Lanthanum fluoride.

In an acute dermal toxicity study (Institut Français de Toxicologie report No. 301229) quoted as Klimisch 2 (due to read-accross), Sprague-Dawley male and female rats (5/sex) were treated with a single dermal dose of Cerium dioxide, as a suspension in 10% gum arabic, at doses of 0 (vehicle only) or 2000 mg/kg bw (limit test) under an occlusive dressing for 24 hours. The animals were observed for 14 days.

No mortality occurred during the observation period. Slightly reduced activity was observed on day1 in rats exposed to the test substance. No signs of cutaneous irritation were seen. No significant changes in body weight were seen when compared to controls and no relevant findings were seen at necropsy on day 14. 

Therefore, the dermal LD50 was higher than 2000 mg/kg for males and females, therefore warranting no classification.

No acute dermal toxicity data were available for Lanthanum oxide or Lanthanum fluoride.

 

An acute dermal study on reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride is therefore not regarded as scientifically necessary according to section 1 of Reach Annex XI and is not recommended under animal protection considerations.

Acute toxicity – LD/LC 50	Reaction mass	Cerium dioxide	Lanthanum oxide	Lanthanum fluoride
Oral	LD 50 > 2000 mg/kg bw	LD 50 > 5000 mg/kg bw	LD 50 > 5000 mg/kg bw	LD 50 > 5000 mg/kg bw (by analogy with Cerium trifluoride)
Dermal	-	LD 50 > 2000 mg/kg bw	-	-
Inhalation	-	LC 50 >5.05mg/L	-	-

Justification for classification or non-classification

Based on the available data on the reaction mass and its constituents showing that no mortality occured after exposure up to the limit dose/concentration whatever the roure of exposure, oral, dermal or inhalation, reaction mass of Cerium dioxide and Lanthanum oxide and Lanthanum fluoride is not classified according to Annex VI Directive 67/548/EEC or UN GHS/EU CLP classification criteria.