Salt reaction of cobalt(2+) and C2/C8/C20 carboxylates

Endpoint summary

Description of key information

Acute oral toxicity:
LD50 > 2000 mg/kg bw 
Acute dermal toxicity:
Conduct of an acute dermal toxicity study is unjustified since dermal uptake is considered negligible.
Acute inhalation toxicity:
The classification from the acute oral toxicity is read-across to the acute toxicity via inhalation. Further results from the ongoing testing programme will be included upon availability.

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:

2021-09-22 to 2021-12-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Version / remarks:

dated December 17th, 2001

Qualifier:

according to guideline

Guideline:

EU Method B.1 tris (Acute Oral Toxicity - Acute Toxic Class Method)

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Saint-Germain-Nuelles, France
- Age at study initiation:8 weeks old at the beginning of the study
- Weight at study initiation: 183 - 208 g
- Fasting period before study: The rats were fasted approx. 1 day prior to dosing, with food being returned to the rats 4 hours after dosing.
- Housing: Animals were housed by group of three in solid-bottomed clear plycarbonate cages with a stainless steel mesh lid. Each cage contains sawdust and was installed in conventional air conditioned animal husbandry
- Diet (ad libitum): Envigo - 2014
- Water: ad libitum
- Acclimatization period: at least 5 days


ENVIRONMENTAL CONDITIONS
- Temperature: 19 - 25 °C
- Relative humidity: 30 - 70 %
- Photoperiod (hrs dark / hrs light): 12/12
- Rate of air exchange : at least 10 changes per hour

Route of administration:

oral: gavage

Vehicle:

olive oil

Details on oral exposure:

Olive oil (vehicle) was chosen as it produced the most suitable formulation at the requested dose of 300 mg/Kg body weight.
For steps 1 & 2 (300 mg/Kg body weight), the preparations were stirred using a vortex for 3 minutes, by Ultraturrax for 3 minutes and manually to obtain black suspensions just before the administration.
For Step 3 (2000 mg/Kg body weight), the preparation was stirred using a vortex for 2 minutes and by Ultraturrax for 3 minutes at 10 000 rpm to obtain a black homogeneous suspension just before the administration.
For Step 4 (2000 mg/Kg body weight), the preparation was stirred using a vortex to obtain a black homogeneous suspension just beofre the administration.
Each preparation was administered by gavage, in a single dose, under a volume of 10 mL/ kg body waight (accounting to the calculated density) using a suitable syringe graduated fitted with an oesophageal metal canula.

Doses:

300 and 2000 mg/Kg body weight

No. of animals per sex per dose:

300 mg/Kg body weight: 6 females
2000 mg/Kg body weight: 6 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Daily examination: Systematic examination were carried out to identify any behavioural or toxic effects on the major physiological functions 30 minutes, 1 hour +/- 6 minutes; 3 hours +/- 30 minutes, 4 hours +/- 30 minutes, 24 and 48 hours +/- 2 hours after administration of the test item and continued daily for 14 days. This examination focuses particularily on a list of symptoms recoreded as 'present' or 'absent'. These observations were compared to historical control data. Observations and a mortality report were then carried out every day for 14 days.
- Periodical examinations: The animals were weighed on D0 (just before administering the test item) then on D2, D7 and D14. Weight changes were calculated and recorded. The body weight evolution of animals treated with the test item is compared with the body weight evolution of the control group.
- Examination at the end of the test: On D14, the animals were anesthetised with sodium pentoarbital. Macroscopic observations were entered on individual autopsy sheets. Only those organs likely to be modified in cases of acute toxicity were examined. No organ was removed and preserved in view to microscopic examinations.

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

other: In accordance with the O.E.C.D. test guideline n° 423, the LD50 cut-off of the test item may be considered as 2500 mg/kg body weight by oral route in the rat.

Mortality:

No mortality occured during the study at the dose of 300 mg/Kg body weight.
One mortality (1/6) was noted on day 6 at the dose of 2000 mg/Kg body weight.

Clinical signs:

other: At the dose of 300 mg/Kg body weight, no clinical signs related to the administration of the test item were observed during the study. At the dose of 2000 mg/kg body weight, the mortality was preceeded by a decrease of spontaneous activity at 1-hour post-

Gross pathology:

At the dose of 300 mg/Kg body weight, the macroscopic examination of the animals at the end of the study did not reveal treatment related changes.
At the dose of 2000 mg/Kg body weight, the macroscopic examination of the dead animal revealed thin stomach membrances and advanced lysis of the digestive system, the urinary system and the reproductive system. The macroscopic examination at the end of the study revealed a thin proventricular (5/5) and fundic (2/5) wall, disintegrated when touched (1/5) with red spot (1/5) and transparent mass (1/5) on the fundic wall.

Interpretation of results:

Category 5 based on GHS criteria

Conclusions:

The LD50 of the test item is higher than 2000 mg/kg body weight by oral route in the rat.
In accordance with the O.E.C.D. test guideline n° 423, the LD50 cut-off of the test item may be considered as 2 500 mg/kg body weight by oral route in the rat..
In accordance with the Regulation EC n°1272/2008 on classification, labelling and packaging of substances and mixture, the test item does not have to be classified. No signal word or hazard statement is required.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

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 – dermal endpoint
Weight of evidence information.

Justification for classification or non-classification

Acute oral toxicity

The reference Chrifi (2021) is considered as the key study for acute oral toxicity and will be used for classification. According to Chrifi (2021) female rats were dosed at 300 and 2000 mg/kg orally via gavage. During the conduct of the study one mortality occurred at the highest dose group.

The LD50 of the test item is higher than 2000 mg/kg body weight by oral route in the rat. In accordance with the O.E.C.D. test guideline n° 423, the LD50 cut-off of the test item may be considered as 2500 mg/kg body weight by oral route in the rat..

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 the toxic effects observed in the acute oral toxicity test already leads to an acute oral toxicity classification. No additional effects in animals or humans are known that would justify a specific target organ toxicant (STOT) – single exposure: oral classification.

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

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

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

Cobalt compounds are not generally associated with local effects following acute inhalation exposure; only after long-term exposure, some inflammatory responses are seen. Thus, any acute inhalation toxicity may reasonably be assumed to be predominantly determined by systemic availability.

Based on the outcome of dustiness testing (Heubach rotating drum method) coupled with particle size analysis of the airborne fraction, all cobalt compounds have moderate to low values for total dustiness, indicating similar propensities to become airborne. Based on the concurrent particle size analysis, inhalation deposition modelling via MPPD clearly indicates that only minor substance amounts can be expected to be deposited in the pulmonary fraction of the respiratory tract of humans; in contrast, the majority of inhaled material will deposit in the extra thoracic and tracheo-bronchiolar regions, and therefore can safely be assumed to undergo translocation to the gastrointestinal tract via mucociliary escalation and subsequent swallowing.

Thus, any systemic effects may be read across from acute oral toxicity.

Based on the LD50 for Salt reaction of cobalt(2 +) and C2/C8/C20 carboxylates of 2500 mg/kg observed in an acute oral toxicity test in rats, it is therefore proposed to adopt the classification as not classified for acute oral toxicity also for acute inhalation toxicity, and to waive the testing requirement for acute inhalation toxicity in accordance with section 1.1, annex XI of regulation (EC) 1907/2006.

Furthermore a testing program is currently being executed, investigation the acute toxicity of cobalt compounds via inhalation. The aim is to cover a wide spectrum of substances to allow read-across to non-testes cobalt substances, to reduce the number of animals.