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Acute Toxicity: oral

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acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-03-19 to 2012-05-07
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guidelines study

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
according to
OECD Guideline 425 (Acute Oral Toxicity: Up-and-Down Procedure)
GLP compliance:
Test type:
up-and-down procedure
Limit test:

Test material

Test material form:
solid: particulate/powder
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): Cobalt powder Ultrafine (C23PTL)
- Physical state: dark gray-black, fine powder
- Stability: test substance was expected to be stable for the duration of testing
- Storage condition of test material: at room temperature in aclosed container and protected from light
- Solubility: sparingly soluble in water

Test animals

Details on test animals and environmental conditions:
- Source: Harlan Laboratories, Inc.
- Age at study initiation: 8 - 11 weeks
- Weight at study initiation: 168 - 218 grams
- Fasting period before study: prior to each dosing, experimentally naive rats were fasted overnight by removing the feed from their cages. During fasting period, the rats were examined for health and weighed (initial). Feed was replaced approximately 3 -4 hours after dosing.
- Housing: the animals were singly housed in suspended stainless steel caging with mesh floors, which conform to the size recommendations in the most recent Guide for the Care and Use of Laboratory Animals (Natl. Res. Council, 2011).
- Diet (ad libitum, except during fasting): Harlan Teklad Global 16% Protein Rodent Diet® #2016
- Water (ad libitum): filtered tap water
- Acclimation period: 6 - 23 days

- Temperature: 19 - 21°C
- Relative humidity: 26 - 69%
- Air changes: 14 air changes/hour
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Details on oral exposure:
Individual doses were calcualted based on the initial body weights, taking into account the sendity (determined by the laboratory) and concentration of the test mixture.

The sample was administered as a 40% w/w mixture in distilled water. Preliminary solubility testing conducted by the laboratory, indicated that mixtures in excess of 40% (i.e., 50% -80%) were too viscous to be adminsitered properly.

Initially, a single animal received a limit dose of 5000 mg/kg. Due to the mortality of this animal, a Main test was conducted. For the Main test, the test substance was administered in sequence to the animals as can be seen in Table 1 (please refer to the field "Any other information on materials and methods incl. tables" below).The decision to proceed with the next animal was based on the survival of the previous animal following dosing. Dose progressions and stopping criteria were determined using a statistical program.

175, 550, 1750 and 5000 mg/kg
No. of animals per sex per dose:
175 mg/kg: 2 female rats
550 mg/kg: 4 female rats
1750 mg/kg: 3 female rats
5000 mg/kg: 1 female rat
Control animals:
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: individual body weights of the animals were recorded prior to test substance administration (initial) and again on Days 7 and 14 (termination) following dosing or after death.
The animals were observed for mortality, signs of gross toxicity, and behavioural changes during the first several hours post-dosing and at least once daily thereafter for 14 days after dosing or until death occurred. Observations included gross evaluation of skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous system, somatomotor activity and behaviour pattern. Perticular attention was directed to observation of tremors, convulsions, salivation, diarrhoea, and coma.
- Necropsy of survivors performed: yes
Surviving rats were euthanized via CO2 inhalation at the end of the 14-day observation period. Gross necropsies were performed on all decedents and euthanized animals. Tissues and organs of the thoracic and abdominal cavities were examined.
The Acute Oral Toxicity (Guideline 425) Statistical Program (Westat. version 1.0, May 2011) was used for all data analyses including: dose progression selections, stopping criteria determinations and/or LD50 and confidence limit calculations.

Results and discussion

Effect levels
Dose descriptor:
Effect level:
ca. 550 mg/kg bw
Based on:
test mat.
95% CL:
215.9 - 1 140
- 175 mg/kg: all animals survived exposure to the test substance
- 550 mg/kg: two animals died within five days of test substance administration.
- 1750 mg/kg: all animals died within four days of test substance administration.
- 5000 mg/kg: the animal died within two days of test substance adminstration.
Clinical signs:
- 175 mg/kg: all animals appeared active and healthy during the study. There were no signs of gross toxicity, adverse pharmacologic effects, or abnormal behaviour.
- 550 mg/kg: prior to death, the animals were hypoactive and exhibited ano-genital staining, reduced faecal volume, diarrhoea, irregular, respiration, nasal discharge and/or facial staining. The surviving females exhibited ano-genital staining, soft faeces, reduced faecal volume, diarrhoea and/or facial staining following test substance administration, but recovered by Day 10 and appeared active and healthy.
- 1750 mg/kg: prior to death, the animals were hypoactive and exhibited reduced faecal volume, ano-genital staining, hunched posture, diarrhoea, soft faeces, nasal discharge, ocular discharge, irregular respiration and/or mouth discharge.
- 5000 mg/kg: prior to death, the animal was hypoactive and exhibited reduced faecal volume, soft faeces, ano-genital staining, hunched posutere and irregular respiration.
Body weight:
- 175 mg/kg: all animals gained body weight.
- 550 mg/kg: The surviving females gaining body weight over the entire 14-day observation period.
Gross pathology:
- 175 mg/kg: no gross abnormalities were noted for these animals when necropsied at the conclusion of the 14-day observation period.
- 550 mg/kg: gross necropsy of the decedents revealed distention of the stomach and/or intestines, discoloured lungs or mottled liver. No gross abnormalities were noted for the euthanized animals when necropsied at the conclusion of the 14-day observation period.
- 1750 mg/kg: gross necorpsy of the decedents revealed distention of the stomach and/or discoloured lungs, or mottled liver.
- 5000 mg/kg: gross necorpsy of the decedent revealed distention of the stomach and intestines and discoloured lungs.

Applicant's summary and conclusion

Interpretation of results:
Toxicity Category IV
Migrated information Criteria used for interpretation of results: EU
LD50 (female rats): ca. 550 mg/kg bw (95% Cl: 215.9 mg/kg - 1140 mg/kg)
According to the EC-Commission directive 67/548/EEC and its subsequent amendments, cobalt is classified as harmful if swallowed.
According to the EC-Regulation 1272/2008 and subsequent regulations, cobalt is classified as Category 4.