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Description of key information

The acute oral LD50 of cesium hydroxide in albino rats was determined to be 1026 mg/kg bw. Acute inhalation and dermal toxicity was waived as cesium hydroxide monohydrate and cesium hydroxide anhydrous are corrosive to the skin.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records
Reference
Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1974
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No GLP, equivalent or similar to OECD and EU guideline.
Reason / purpose:
reference to other study
Reference:
Composition 0
Composition 0
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 401 (Acute Oral Toxicity)
Deviations:
not specified
Qualifier:
equivalent or similar to
Guideline:
EU Method B.1 (Acute Toxicity (Oral))
Deviations:
not specified
GLP compliance:
no
Test type:
standard acute method
Limit test:
no
Test material information:
Composition 1
Species:
rat
Strain:
other: Charles River albino rats
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River, cesarian-derived albino rats
- Weight at study initiation: 175 -250 g
- Fasting period before study: yes (overnight, 16 h)
Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
VEHICLE
- Justification for choice of vehicle: good solubility in water

CsOH was dissolved in deionized-distilled water on a weight-to-weight basis prior to administration.
Doses:
500, 625, 781, 976, 1220, 1525 mg/kg bw.
No. of animals per sex per dose:
10 male rats
Control animals:
not specified
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: 1 and 4 h following administration and dayly thereafter for the 14-day period
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, histopathology, behavioral observations
Statistics:
The LD50 values and their 95% confidence limits were calculated by probit analysis of Finney (1971).
Preliminary study:
no preliminary results.
Sex:
male
Dose descriptor:
LD50
Effect level:
1 026 mg/kg bw
Based on:
test mat.
Remarks:
Caesium hydroxide
95% CL:
929 - 1 133
Mortality:
All deaths occured within the first 72 h after dosing.
Clinical signs:
Clinical signs were increased respiration rate, ruffled fur, eye closing and huddling together. A bloody nasal exudate was noted in several animals receiving the higher doses.
Body weight:
No data on body weight.
Gross pathology:
Lethal and certain sublethal doses induced stomach and intestinal haemorrhage and adhesions of abdominal organs (stomach, pancreas, spleen, liver and small intestines). In the higher dose range, death was related to the degree of blockage of the gastrointestinal tract from the resultant adhesions and/or the leakage of the bloody fluid exudate into the peritoneal cavity.
Other findings:
Behavioral effects noted for survivors were initial hyperexcitability followed by apathy and weakness which persited the 14-day observation period.
Interpretation of results:
Toxicity Category IV
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
The acute oral LD50 of cesium hydroxide in albino rats was determined to be 1026 mg/kg bw.
Executive summary:

In an acute oral toxicity study, groups of 10 fasted male albino rats were given a single oral dose of cesium hydroxide in water at 6 different doses and observed for 14 days.

All deaths occurred within the first 72 h after dosing. Clinical signs were increased respiration rate, ruffled fur, eye closing and huddling together. A bloody nasal exudate was noted in several animals receiving the higher doses. Lethal and certain sublethal doses induced stomach and intestinal haemorrhage and adhesions of abdominal organs (stomach, pancreas, spleen, liver and small intestines). In the higher dose range, death was related to the degree of blockage of the gastrointestinal tract from the resultant adhesions and/or the leakage of the bloody fluid exudate into the peritoneal cavity.

Oral LD50 for males for cesium hydroxide = 1026 mg/kg bw (95% C.L: 929 - 1133).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
1 026 mg/kg bw
Quality of whole database:
Non GLP, but scientifically well documented studiy. Procedure equivalent or similar to OECD and EU guideline.

Acute toxicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no study available

Acute toxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Oral:

In an acute oral toxicity study, groups of 10 fasted male albino rats were given a single oral dose of cesium hydroxide in water at 6 different doses and observed for 14 days.

All deaths occurred within the first 72 h after dosing. Clinical signs were increased respiration rate, ruffled fur, eye closing and huddling together. A bloody nasal exudate was noted in several animals receiving the higher doses. Lethal and certain sublethal doses induced stomach and intestinal haemorrhage and adhesions of abdominal organs (stomach, pancreas, spleen, liver and small intestines). In the higher dose range, death was related to the degree of blockage of the gastrointestinal tract from the resultant adhesions and/or the leakage of the bloody fluid exudate into the peritoneal cavity.

Oral LD50 for males for cesium hydroxide = 1026 mg/kg bw (95% C.L: 929 - 1133).

Inhalation:

In accordance with column 2 of REACH Regulation (EC) No. 1907/2008, Annex VIII, the test on acute inhalation toxicity (required in section 8.5.2) does not need to be conducted as cesium hydroxide monohydrate is classified as corrosive to the skin. In addition, exposure via the inhalation route is not likely as cesium hydroxide has a very low vapour pressure of < 0.1 hPa at 20°C and the particle size distribution shows no inhalable particles (d10 = 146 µm).

Dermal:

In accordance with column 2 of REACH Regulation (EC) No. 1907/2008,

Annex VIII, the test on acute dermal toxicity (required in section 8.5.3) does not need to be conducted as cesium hydroxide monohydrate is classified as corrosive to the skin.

Other routes:

In a study by Cochran et al. (1950) rats were intraperitoneally exposed to cesium hydroxide. The study revealed a LC50 of 100 mg/kg bw (Cochran et al., "Acute toxicity of zirconium, columbium, strontium, lanthanum, cesium, tantalum and yttrium.", Arch Ind Hyg Occup Med. 1950 Jun;1(6):637-50).

Further information:

A review article issue by “The British Industrial Biological Research Associations” (bibra), titled “Toxicity Profile of Cesium Compounds (2000)”, states oral LD50 values for cesium hydroxide of 600 to 1000 mg/kg bw for rats and 800 mg/kg bw for mice.


Justification for selection of acute toxicity – oral endpoint
Most reliable study.

Justification for selection of acute toxicity – inhalation endpoint
Exposure via inhalation is not considered relevant, due to unlikely exposure via inhalation. Furthermore, cesium hydroxide monohydrate and cesium hydroxide anhydrous are classified as corrosive to the skin and the evaluation of acute toxicity via inhalation route is not appropriate.

Justification for selection of acute toxicity – dermal endpoint
Cesium hydroxide monohydrate and cesium hydroxide anhydrous are classified as corrosive to the skin and further evaluation of acute toxicity via dermal route is not appropriate.

Justification for classification or non-classification

Based on the results obtained in the acute oral toxicity study (LD50, rat = 1026 mg/kg bw) cesium hydroxide and hence, also cesium hydroxide monohydrate have to be classified in acute toxicity category 4 (H302: Harmful if swallowed) according to Regulation (EC) No 1272/2008 (GHS).

No data for acute inhalation and dermal toxicity is available and required as cesium hydroxide is corrosive to the skin.