Cobalt oxalate

Endpoint summary

Description of key information

Acute oral toxicity:
LD50(rat)> 5000 mg cobalt oxalate/kg bw
Acute dermal toxicity:
Conduct of an acute dermal toxicity study for cobalt oxalate is unjustified since dermal uptake is considered negligible.
Acute inhalation toxicity:

LC50(rat)> 5.06 mg cobalt oxalate/L

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:

2010-08-23 to 2010-09-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 425 (Acute Oral Toxicity: Up-and-Down Procedure)

Deviations:

no

GLP compliance:

yes

Test type:

up-and-down procedure

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Ace Animals, Inc., Boyertown, PA
- Age at study initiation: 9-11 weeks
- Weight at study initiation: 180-221 g
- Fasting period before study: Naive rats were fasted overnight.
- 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, 1996). Litter paper was placed beneath the cage and was changed at least three times per week.
- Diet: Purina Rodent Chow # 5012; feed was replaced approx. 3-4 hours after dosing.
- Water (ad libitum): Filtered tap water
- Acclimation period: 8-23 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19-22°C
- Relative humidity: 46-77%; humidity was above the targeted upper limit for one day during the study. A portable dehumidifier was used to lower the humidity levels during this time.
- Photoperiod (hrs dark / hrs light): 12-hour light/dark cycle

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

VEHICLE
- Concentration in vehicle: The test substance was administered as a 50% w/w mixture in distilled water.
- Justification for choice of vehicle: Preliminary solubility testing conducted by EPSL, indicated that mixtures in excess of 50% (i.e., 55-80%) were too viscous to be administered properly.

MAXIMUM DOSE VOLUME APPLIED:
5,000 mg/kg

DOSAGE:
Individual doses were calculated based on the initial body weights, taking into account the specific gravity (determined by EPSL) and concentration of the test mixture.

Based on a limit dose of 5,000 mg/kg at the request of the sponsor a Main test was conducted using a default starting dose level of 175 mg/kg administered to one healthy female rat and following the Up and Down procedure, five additional females were dosed.

Doses:

175, 550, 1,750 or 5,000 mg/kg

No. of animals per sex per dose:

1 animal per 175 mg/kg dose level
1 animal per 550 mg/kg dose level
1 animals per 1,750 mg/kg dose level
3 animals per 5,000 mg/kg dose level

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: All animals were observed for mortality, signs of gross toxicity and behavioral changes during the first several hours post-dosing and at least once daily thereafter for 14 days after dosing. Body weights were recorded prior to administration and again on Days 7 and 14 (termination) following dosing.
- Necropsy of survivors performed: yes; all rats were euthanized via CO2 inhalation at the end of the 14-day observation period. Gross necropsies were performed on all animals. Tissues and organs of the thoracic and abdominal cavities were examined.
- Other examinations performed: Observations included gross evaluation of skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous systems, somatomotor activity and behavior pattern. Particular attention was directed to observations of tremors, convulsions, salivation, diarrhea and coma.

Statistics:

The Acute Oral Toxicity (Guideline 425) Statistical Program (Westat, version 1.0, May 2001) was used for all data analyses including: dose progression selections, stopping criteria determinations and/or LD50 and confidence limit calculations.

Sex:

female

Dose descriptor:

LD50

Effect level:

> 5 000 mg/kg bw

Based on:

test mat.

Mortality:

All animals of the 175, 550, 1750 and 5000 mg/kg dose levels survived the test substance administration.

Clinical signs:

other: All animals of the 175, 550, 1750 and 5000 mg/kg dose levels appeared active and healthy during the study; no signs of gross toxicity, adverse pharmacologic effects or abnormal behaviour were noted.

Gross pathology:

No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-days observation period.

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of this study, the acute oral LD50 of Cobalt Oxalate is estimated to be greater than 5,000 mg/kg in female rats.
According to the EC Regulation No. 1272/2008 and subsequent regulations, the test item is not classified.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015-02-15 to 2016-03-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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 2014-05-14

Test type:

acute toxic class method

Limit test:

yes

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: container kept upright and tightly closed in a dry, cool and well-ventilated place, avoiding heat or direct sunlight.

Species:

rat

Strain:

other: Crl: 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, Sulzfeld ,Germany
- Females nulliparous and non-pregnant: yes
- Age at study initiation: males: approx. 8 weeks; females: approx. 9 weeks
- Weight at study initiation: males: 257 - 280 g; females: 233 - 260 g
- Fasting period before study: feeding was discontinued approx. 16 hours before exposure; only tap water was then available ad libitum.
- Housing: kept by sex in groups of 3 animals (MAKROLON cages (type III plus)) during the 14-day observation period; bedding material: granulated textured wood (Granulat A2, J. Brandenburg, Goldenstedt, Germany)
- Diet: commercial diet, ssniff® R/M-H V1534 (ssniff Spezialdiäten GmbH, Soest, Germany)
- Water (ad libitum): drinking water
- Acclimation period: at least 5 adaptation days
Animals were acclimatised to the test apparatus for approx. 1 hour on 2 days prior to testing.

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

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

clean air

Mass median aerodynamic diameter (MMAD):

>= 1.9 - <= 1.974 µm

Geometric standard deviation (GSD):

>= 2.5 - <= 2.55

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus /exposure chamber volume: dynamic inhalation apparatus (RHEMA-LABORTECHNIK) (air changes/h (≥ 12times)) with a nose-only exposure of the animals according to KIMMERLE & TEPPER.
The apparatus consists of a cylindrical exposure chamber, which holds the animals in pyrex tubes at the edge of the chamber in a radial position.
Actual dimensions of the inhalation chamber: inner diameter: 28.2 cm; height: 64.6 cm; volume: 40.3 L

- System of generating particulates/aerosols: dust of the test item was generated using a rotating brush dust generator (RBG 1000, PALAS GmbH Partikel und Lasermesstechnik). The generator was fed with compressed air (5.0 bar) from a compressor (ALUP Kompressorenfabrik).
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 homogenous 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) were used to control the constant supply of compressed air and the exhaust, respectively. Flow rates were checked hourly and corrected if necessary.

- Method of particle size determination: an analysis of the particle size distribution was carried out twice during the exposure period using a cascade impactor 6.0 L/min (TSE Systems GmbH).
The dust from the exposure chamber was drawn through the cascade impactor for 1 minute (constant flow rate: 5 L/min). The slides were removed from the impactor and weighed on an analytical balance (Sartorius BP 121 S, 120 g weighing capacity, precision: 0.1 mg, resolution: 0.1 mg, linearity: 0.2 mg). Deltas of slides’ weight were determined.
The mass median aerodynamic diameter (MMAD) was estimated by means of non-linear regression analysis. The 10.6 μm particle size range and the filter (particle size range < 0.55 μm) were not included in the determination of the MMAD in order not to give undue weight to these values.
The Geometric 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.

- Temperature, humidity, pressure in air chamber, oxygen content; carbon dioxide content: oxygen content in the inhalation chamber was 21% (determined at the beginning and at the end of the exposure; DRÄGER Oxygen-analysis test set)(DRÄGER Tube Oxygen 67 28 081). Carbon dioxide concentration did not exceed 1%.
Temperature (21.0°C ± 0.2°C (main study) or 21.1°C ± 0.1°C (satellite group)) and humidity (57.3% ± 0.1% (main study) or 51.4% ± 0.1% (satellite group)) were measured once every hour with a climate control monitor (testo 175-HZ data logger).

Exposition started by locating the animals into the exposure chamber after equilibration of the chamber concentration for at least 15 minutes (t95 approx. 8 minutes).
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.

TEST ATMOSPHERE
- Brief description of analytical method used: 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 2C) controlled by a rotameter. Dust samples were taken once every hour during the exposure. The filters were weighed before and after sampling (accuracy 0.1 mg).
- Samples taken from breathing zone: yes, at a constant flow of air of 5 L/min for 1 minute

Individual chamber concentration samples did not deviate from the mean chamber concentration by more than 1%.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

Main study (limit test):
- actual concentration: 5.06 ± 0.01 mg/L air
- nominal concentration: 24.44 mg/L air
Satellite group:
- actual concentration: 5.06 ± 0.03 mg/L air
- nominal concentration: 24.44 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 the exposure period the animals were observed frequently. Following exposure, observations were made at least twice on the day of exposure and at least once each day. Observations on mortality were made at least once daily (in the morning starting on test day 2).
Individual weights of animals were determined once during the acclimatisation period, before the exposure on test day 1, on test days 2, 4, 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 was carried out and all gross pathological changes were recorded:
- satellite animals: necropsy at 24 hours after cessation of exposure
- main study animals: necropsy at the end of the 14-day observation period

All main study and satellite animals were subjected to 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, and thickened mucous layer.
The following organs of all animals were fixed: nasal cavity (tip and 5 levels; tip and level 1: cut just anterior to the incisor teeth; level 2: cut approx. 2 mm posterior to free the tip of the
incisor teeth; level 3: cut through the incisive papilla; level 4: cut through the middle of the second palatal ridge, which is located just anterior to the molar teeth; level 5: cut through the middle of the molar teeth), nasopharynx, paranasal sinus, larynx, trachea, and lung.

The histopathology was conducted in consideration of the suggestions made in the OECD Guidance Document on Histopathology for Inhalation Toxicity Studies, Supporting TG 41 (Subacute Inhalation Toxicity: 28-day Study) and TG 413 (Subchronic Inhalation Toxicity: 90-day Study). OECD Series on Testing and Assessment No. 125, Document No. ENV/JM/MONO (2010) 16, June 01, 2010.

Assessment of respiratory tract irritation effects:
The assessment of respiratory tract irritation effects was conducted according to the criteria set forth in the OECD proposal document ENV/JM/HCL(2004)9/REV, where it is stated:
- There are currently no validated animal tests that deal specifically with respiratory tract irritation. However, useful information may be obtained from single and repeated inhalation toxicity tests. For example, animal studies may provide useful information in terms of toxicity (dyspnoea, rhinitis etc) and histopathology (e.g. hyperaemia, oedema, minimal inflammation, and thickened mucous layer) which are reversible and may be reflective of the characteristic clinical symptoms described above. Such animal studies can be used as part of weight of evidence evaluation.
- The special classification would occur only when more severe organ/systemic effects including the respiratory system were not observed.

Statistics:

not applicable

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.06 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

5.06 mg/L air (main study) and 5.06 mg/L air (satellite group): no animal died prematurely.

Clinical signs:

other: 5.06 mg/L air (main study) and 5.06 mg/L air (satellite group): slight dyspnoea (reduced frequency of respiration with increased volume) immediately after end of exposure until 3 hours post exposure was observed in 3 of 3 male and 3 of 3 female animals of

Body weight:

5.06 mg/L air (main study): all 3 of 3 male and 3 of 3 female animals appeared to be reduced in body weight gain throughout the whole recovery period.

Gross pathology:

No pathological findings were noted in the nasal cavity and in the lungs, neither for the main study animals (14-day sacrifice) nor for the satellite animals (24-hour sacrifice).

Other findings:

1) Histopathology (test item related changes):
- 5.06 mg/L air (satellite group): the turbinates of levels 2 to 5 of the nasal cavities showed an acute mild to moderate focal degeneration of the olfactory epithelium with focal pyknosis, karyorrhexis and loss of olfactory epithelial cells. In the neighborhood of these defects a normal olfactory epithelium was detected.
Inflammatory cells were not noted near the degenerative olfactory epithelium. A normal respiratory epithelium partially with cilia was observed for the levels 2 to 5 of the nasal cavity. The respiratory epithelium contained three normal major cell types, the basal cells above the basement membrane, the ciliated epithelial cells and the secretory goblet cells.

2) Histopathology (not test item related changes):
- 5.06 mg/L air (main study) and 5.06 mg/L air (satellite group):
Nose (five levels): the nasal cavity and the turbinates of the nose of levels 1 to 5 showed a normal squamous and respiratory epithelium and a normal olfactory epithelium for levels 2 to 5. The olfactory epithelium of the main study rats showed a complete reversibility after a recovery of 14 days. The respiratory epithelium contained three normal major cell types, the basal cells above the basement membrane, the ciliated epithelial cells and the secretory goblet cells without degenerative or inflammatory reactions.

Lungs (five levels): all 5 lung localizations per animal of the satellite animals and the main study rats showed a minimal to mild alveolar haemorrhage and a minimal to mild focal atelectasis. These minimal changes are interpreted as spontaneous incidental findings within the normal range.

Trachea and larynx : the trachea and larynx showed a focal minimal to mild subepithelial lymphohistiocytic infiltration without degeneration of the epithelial cells. The number of seromocous glands in the larynx without inflammatory reactions was morphologically normal.

Interpretation of results:

GHS criteria not met

Conclusions:

LC50 (male and female rats; 4 hours) > 5.06 mg/L air (actual concentration)
According to the EC-Regulation 1272/2008 and subsequent regulations, cobalt oxalate is not classified as acute toxic via the inhalation route.

Based on the results of the macroscopic and histopathological investigations, cobalt oxalate appears to be marginally irritating for the nasal cavities, confirmed by marginal histopathological changes in form of an acute mild to moderate focal degeneration of the focal olfactory epithelium. The changes observed were completely reversible during the 14-day recovery period.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Additional information

Justification for selection of acute toxicity – oral endpoint
Key study

Justification for selection of acute toxicity – inhalation endpoint
Key study

Justification for selection of acute toxicity – dermal endpoint
Weight of evidence information

Justification for classification or non-classification

Acute oral toxicity

The reference Durando (2011) is considered as the key study for acute oral toxicity of cobalt oxalate and will be used for classification. Female Sprague-Dawley rats were dosed a maximum of 5000 mg/kg orally via gavage. During the observation period of 14 days no adverse effects or mortalities were observed, thus the LD50 is > 5000 mg cobalt hydroxide oxide/kg bw.

The classification criteria according to regulation (EC) 1272/2008 as acutely toxic are not met since the ATE is above 2000 mg/kg body-weight, hence no classification required.

Specific target organ toxicant (STOT) – single exposure: oral

The classification criteria according to regulation (EC) 1272/2008 as specific target organ toxicant (STOT) – single exposure, oral are not met since no reversible or irreversible adverse health effects were observed immediately or delayed after exposure and no effects were observed at the guidance value, oral for a Category 1 classification of 300 mg/kg bw and at the guidance value, oral for a Category 2 classification of 2000 mg/kg bw. No classification required.

Acute dermal toxicity

Conduct of an acute dermal toxicity study for cobalt oxalate is unjustified since dermal uptake is considered negligible.

 

Specific target organ toxicant (STOT) – single exposure: dermal

Conduct of an acute dermal toxicity study for cobalt oxalate is unjustified since dermal uptake is considered negligible.

Acute inhalation toxicity

The reference Haferkorn (2016) is considered as the key study for acute inhalation toxicity of cobalt oxalate and will be used for classification. Male and female Sprague-Dawley rats were exposed to 5.06 mg/L air (main study, observation period 14 days and satellite group; observation period 24 hours) for 4 hours. No mortality occurred at 5.06 mg/L air concentration in the main study and in the satellite group. The LC50 is > 5.06 mg/L air. The classification criteria according to regulation (EC) 1272/2008 as acutely toxic are not met since the ATE is above 5.0 mg/L, hence no classification required.

Specific target organ toxicant (STOT) – single exposure: inhalation

The classification criteria according to regulation (EC) 1272/2008 as specific target organ toxicant (STOT) – single exposure, inhalation are not met since no reversible or irreversible adverse health effects were observed immediately or delayed after exposure and no effects were observed at the guidance value, inhalation for a Category 1 classification of ≤ 1 mg/L/4h and at the guidance value, inhalation for a Category 2 ≤ 5 mg/L/4h - > 1 mg/L/4h. No additional classification required.