Tricobalt tetraoxide

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-09-14 to 2010-11-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class Method)

Version / remarks:

2009-09-07

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2009-11-12

Test type:

acute toxic class method

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Tricobalt tetraoxide

EC Number:

215-157-2

EC Name:

Tricobalt tetraoxide

Cas Number:

1308-06-1

Molecular formula:

Co3O4

IUPAC Name:

dicobalt(3+) λ²-cobalt(2+) tetraoxidandiide

Details on test material:

- Name of test material (as cited in study report): Tricobalt tetraoxide
- Molecular formula: Co3O4
- Molecular weight: 240.7972 g/mol
- Physical state: grey-black powder
- Storage condition of test material: in original container, tightly closed in a dry, cool and well ventilated place
- Particle size parameter determined with a CILAS 715 (non-GLP determination): d(0.1) = 0.86 µm; d(0.5) = 7.17 µm (median); d(0.9) = 12.18 µm
- Melting point: Decomposes at 900 °C
- Water solubility: 1.62 mg/L at 20 °C

Test animals

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, 97633 Sulzfeld, Germany
- Age at start of administration: males: 49 - 50 days; females: 63 - 64 days
- Weight at start of administration: males: 244 - 266 g; females: 210 - 244 g
- Fasting period before study: feeding was discontinued approx. 16 hours before exposure; only tap water was then available ad libitum
- Housing: granulated textured wood (Granulat A2, J. Brandenburg, 49424 Goldenstedt, Germany) was used as bedding material for the cages. The cages were changed and cleaned twice a week; kept by sex in groups of 2 -3 animals in MAKROLON cages (type III plus)
- Diet (please refer to "Fasting period before study" above): commercial diet, ssniff® R/M-H V1534 served as food (ssniff Spezialdiäten GmbH, 59494 Soest, Germany)
- Water (ad libitum): drinking water
- Acclimation period: at least 5 adaptation days; the animals were randomised before use. The animals were acclimatised to the test apparatus for approx. 1 hour on 2 days prior to testing. The restraining tubes did not impose undue physical, termal or immobilization stress on the animals.

ENVIRONMENTAL CONDITIONS
- Temperature: 22 °C +/- 3 °C (maximum range)
- Relative humidity: 55 % +/- 15 % (maximum range)
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

clean air

Mass median aerodynamic diameter (MMAD):

>= 3.085 - <= 3.763 µm

Geometric standard deviation (GSD):

>= 2.75 - <= 3.26

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: the study was carried out using a dynamic inhalation apparatus (RHEMA-LABORTECHNIK, 65719 Hofheim/Taunus, Germany) (air changes/h (≥ 12 times)) with a nose-only exposure of the animals according to KIMMERLE & TREPPER. The apparatus consists of a cyclindrical exposure chamber (volume 40 L) which is able to hold 10 animals in pyrex tubes at the edge of the chamber in a radial position.

- System of generating particulates/aerosols: the dust of the test material was generated with a rotating brush dust generator (RBG 1000, PALAS GmbH Partikel und Lasermesstechnik, 76229 Karlsruhe, Germany).
The generator was fed with compressed air (5.0 bar) from a compressor (ALUP Kompressorenfabrik, 73257 Köngen, Germany)(air was taken from the surrounding atmosphere of the laboratory room and filtered using an in-line disposable gas-filter).
At the bottom of the exposure chamber, the air was sucked off at a lower flow rate than it was created by the dust generator in order to produce a homogeneous distribution and a positive pressure in the exposure chamber (inflow 900 L/h, outflow 800 L/h).
A manometer and an air-flow meter (ROTA Yokogawa GmbH & Co. KG, 79664 Wehr/Baden, Germany) were used to control the constant supply of compressed air and the exhaust, respectively. Flow rates were checked hourly and corrected if necessary.
The exhaust air was drawn through gas wash-bottles.

- Temperature, humidity, oxygen content, carbon dioxide content: the oxygen content in the inhalation chamber was 21 %. It was determined at the beginning and at the end of the exposure with a DRÄGER Oxygen-analysis test set (DRÄGER Tube oxygen 67 28 081). Carbon dioxide concentration did not exceed 1 %.
Temperature (20.9 °C +/- 0.1 °C (main study) or 20.3 °C +/- 0.1 °C (satellite group)) and humidity (60.4 % +/- 0.1 % (main study) or 50.4 % +/- 0.0 (satellite group)) were measured once every hour with a climate control monitor (testo 175-HZ data logger).

The whole exposure system was mounted in an inhalation facility to protect the laboratory staff from possible hazards.

The exposure was initiated by placing the animals' noses into the exposure chamber after equilibration of the chamber concentration for at least 15 minutes (t95 approximately 8 minutes).

Before initiating the study with the animals, a pre-test was carried out with the exposure system in order to verify that under the experimental settings chosen, the limit concentration of 5 mg/L air could be achieved by gravimetric analysis.

The tests with the main study animals and the recovery animals were conducted in the same inhalation chamber but on different days. Between the exposure times the chamber was cleaned carefully.

- Method of particle size determination: an analysis of the particulate size distribution was carried out twice during the exposure period using a cascade impactor according to MAY (MAY, K.R. Aerosol impaction jets, J. Aerosol Sci. 6, 403 (1975), RESEARCH ENGINEERS Ltd., London N1 5 RD, UK).
The dust from the exposure chamber was drawn through the cascade impactor for 5 minutes at a constant flow rate of 5 L/min. The slides were removed from the impactor and weighed on an analytical balance (SARTORIUS, type 1601 004, precision 0.1 mg). Deltas of slides' weight were determined.
The mass median aerodynamic diameter (MMAD) was estimated by means of non-linear regression analysis. The 32 µm particle size range and the filter (particle size range < 0.5 µm were not included in the determination of the MMAD in order not to give undue weight to these values.
The Geomteric Standard Deviation (GSD) of the MMAD was calculated from the quotient of the 84.1 %- and the 50 %-mass fractions, both obtained from the above mentioned non-linear regression analysis.
In addition, a sample of approx. 10 g test material was taken from the exposure chamber to determine the median physical particulate size with a CILAS 715 by My-Tec, 91325 Adelsdorf, Germany. This determination was non-GLP.

TEST ATMOSPHERE
- Brief description of analytical method used: the actual dust concentration in the inhalation chamber was measured gravimetrically with an air sample filter (Minisart SM 17598 0.45 µm) and pump (Vacuubrand, MZ 2 C (Membrane Pump, Vacuubrand GmbH + Co. KG, 97877 Wertheim/Main, Germany)) controlled by a rotameter. Dust samples were taken once every hour during the exposure. For that purpose, a probe was placed close to the animals' noses and air was drawn through the air sample filter at a constant flow of air of 5 L/min for 1 minute. The filters were weighed before and after sampling (accuracy 0.1 mg). The correct loading of the filter was checked by the airflow via the rotameter and by a positive weight increase of the filter after the sampling period of 1 minute.
- Samples taken from breathing zone: yes

TEST ATMOSPHERE (if not tabulated)
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.):
Main study: 3.085 µm (GSD: 2.75 µm)
Satellite group: 3.763 µm (GSD: 3.26 µm)
No smaller GSD could be obtained with the test item supplied.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

please refer to "details on inhalation exposure" above

Duration of exposure:

4 h

Concentrations:

Main study (limit test):
- actual concentration: 5.06 +/- 0.07 mg/L air
- nominal concentration: 5.0 mg/L air
Satellite group:
- actual concentration: 5.04 +/- 0.07 mg/L air
- nominal concentration: 5.0 mg/L air

No. of animals per sex per dose:

Main study (limit test):
3 males / 3 females
Satellite group:
3 males / 3 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 24 hours (satellite group) and 14 days (main study)
- Frequency of observations and weighing: during and following exposure, observations were made and recorded systematically; individual records were maintained for each animals. Careful clinical examinations were made at least twice daily until all symptoms subsided, thereafter each working day. Observations on mortality were made at least once daily (in the morning starting on test day 2) to minimize loss of animals to the study, e.g. necropsy or refrigeration of those animals found dead and isolation or sacrifice of weak or moribund animals.
Cageside observations included, but were not limited to: changes in the skin and fur, eyes, mucous membranes, respiratory, circulatory, autonomic and central nervous system, as well as somatomotor activity and behaviour pattern.
Particular attention was directed to observation of tremor, convulsions, salivation, diarrhoea, lethargy, sleep and coma. The animals were also observed for possible indications of respiratory irritation such as dyspnoea, rhinitis etc..
Individual weights of animals were determined once during the acclimatisation period, before and after the exposure on test day 1, on test days 3, 8 and 15. Changes in weight were calculated and recorded when survival exceeded one day. At the end of the test, all animals were weighed and sacrificed.
- Necropsy of survivors performed: yes
Necropsy of all main study and satellite animals (3 + 3 males and 3 + 3 females) was carried out and all gross pathological changes were recorded:
- satellite animals: necropsy at 24 hours after cessation of exposure, as this is likely to be the time at which any signs of respiratory irritation would have manifested;
- main study animals: necropsy at the end of the 14- day observation period
Histopathology:
All main study and satellite animals were subjected to the same level of histopathological examination upon necropsy at the end of the respective observation period. During histopathology, attention was paid to alterations that might be indicative of respiratory irritation, such as hyperaemia, oedema, minimal inflammation, thickened mucous layer.
The following organs of all animals were fixed in 10 % (nose, i.e. head without brain, eyes and lower jar) or 7 % (other organs) buffered formalin for histopathological examination:
- nose (5 levels of the nasal turbinates): the tip and Level 1 of the nose were taken from the cut just anterior to the incisor teeth. With tip removed, Level 2 was taken approximately 2 mm posterior to free tip of the incisor teeth. Level 3 was cut through the incisive papilla. Level 4 was cut through the middle of the second palatal ridge, which is located just anterior to the molar teeth. Level 5 was cut through the middle of the molar teeth. All sections were embedded face down to yield a section from the anterior section, except the nose tip was embedded posterior surface down.
- larynx
- trachea
- lungs (five levels)
Paraffin sections were prepared of all above mentioned organs and stained with haematoxylin eosin.

Statistics:

Since no mortality occurred, the calculation of an LC50 was not required.

Results and discussion

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.06 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

No mortality occurred in either the main study or the satellite group.

Clinical signs:

other: Main study: A 4-hour inhalation exposure to tricobalt tetraoxide at a concentration of 5.06 mg/L air revealed slight dyspnoea (reduced frequency of respiration with increased volume) in all 3 male and 3 female rats on test day 1 immediately after the end

Body weight:

Body weight gain of the 3 female animals of the main study appeared to be reduced.
Body weight of the animals of the satellite group was not significantly reduced.

Gross pathology:

Haemorrhagic lungs were observed in all satellite animals (24-hour sacrifice).
No necropsy findings were made in the animals of the main study.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

LC50 (male and female rats, 4 hours) > 5.06 mg/L air
Based on the results of the histopathological and macroscopic investigations, tricobalt tetraoxide does not require classification for respiratory irritation.
According to the criteria specified by Directive 67/548/EEC and subsequent regulations, tricobalt tetraoxide does not require classification either for acute inhalation toxicity or for respiratory irritation.
According to the EC Regulation No. 1272/2008 and subsequent regulations, tricobalt tetraoxide does not require classification for acute inhalation toxicity or specific target organ toxicity -single exposure.