Calcium hexaboride

Acute Toxicity: dermal

Administrative data

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Version / remarks:

2017

Deviations:

no

Remarks:

No deviations that impacted the intergrity or interpretability of the study occurred.

GLP compliance:

yes

Test type:

fixed dose procedure

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Calcium hexaboride

EC Number:

234-525-3

EC Name:

Calcium hexaboride

Cas Number:

12007-99-7

Molecular formula:

B6Ca

IUPAC Name:

hexaboron(3+) calcium

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Aldrich, Lot 10125LZV
- Expiration date of the lot/batch: 01 February, 2019
- Purity test date: 01 December, 2017

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature
- Stability under test conditions: Stabile
- Solubility and stability of the test substance in the solvent/vehicle: Stabile
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: Stabile

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test article was suspended in 1% aqueous carboxymethyl cellulose.
- Preliminary purification step (if any): None

Test animals

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Deutschland, Sulzfeld, Germany
- Females nulliparous and non-pregnant: Yes
- Age at study initiation: approximately 10 weeks old
- Weight at study initiation: 182 to 198 g
- Fasting period before study: None
- Housing: On arrival, animals were group housed (up to 5 animals of the same sex together) in polycarbonate cages (Makrolon MIV type; height 18 cm.) and following assignment to the study, animals were individually housed in polycarbonate cages (Makrolon MIII type; height 18 cm.) containing sterilized sawdust as bedding material (Lignocel S 8-15, JRS - J.Rettenmaier & Söhne GmbH + CO. KG, Rosenberg, Germany) equipped with water bottles.
- Diet (e.g. ad libitum): Pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany) was provided ad libitum throughout the study
- Water (e.g. ad libitum): Municipal tap-water was freely available to each animal via water bottles.
- Acclimation period: At least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-24 C
- Humidity (%): 30-51
- Air changes (per hr): At least 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 12 March, 2018 To: 20 March, 2018

Administration / exposure

Type of coverage:

semiocclusive

Vehicle:

CMC (carboxymethyl cellulose)

Details on dermal exposure:

TEST SITE
- Area of exposure: Back of the animal
- % coverage: 10% of the total body area
- Type of wrap if used: Coban

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Yes, the area was washed with water to remove the test article following exposure.
- Time after start of exposure: 24 hours.

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 2,000 mg/kg body weight
- Concentration (if solution): The dose volume was 10 mL/kg
- Constant volume or concentration used: yes
- For solids, paste formed: Homogenous suspension.

VEHICLE
- Amount(s) applied (volume or weight with unit): 10 mL/kg

Duration of exposure:

24 hours

Doses:

2,000 mg/kg bodyweight

No. of animals per sex per dose:

3 females per dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Postdose observations were performed at periodic intervals on the day of dosing (at least three times) and once daily thereafter. The observation period was 14 days. All the animals were examined for reaction to dosing. The onset, intensity and duration of these signs was recorded (if appropriate), particular attention being paid to the animals during and for the first hour after dosing.

- Necropsy of survivors performed: Yes
- Other examinations performed:
The skin reactions were assessed approximately 24, 48 and 72 hours after the removal of the dressing and test item. Adjacent areas of untreated skin of each animal served as controls.
The following numerical scoring system was used in the scoring of skin reactions:
Erythema and eschar formation:
No erythema: 0
Very slight erythema (barely perceptible): 1
Well-defined erythema: 2
Moderate to severe erythema: 3
Severe erythema (beef redness) *: 4
*. Where signs of necrosis or corrosion (injuries in depth) prevent erythema scoring, the maximum grade for erythema (= 4) is given.

Oedema formation:
No oedema: 0
Very slight oedema (barely perceptible): 1
Slight oedema (edges of area well-defined by definite raising): 2
Moderate oedema (raised approximately 1 millimeter) 3
Severe oedema (raised more than 1 millimeter and extending beyond the area of exposure): 4

Results and discussion

Effect levels

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

no indication of skin irritation up to the relevant limit dose level

Mortality:

No mortality ocurred during the study.

Clinical signs:

other: No signs of systemic toxicity were noted. Black staining of the treated skin was noted for the animals on Days 2 and/or 3. Additionally, blue discoloration of the skin was noted for one animal on Day 3. This was considered to be due to the staining prop

Gross pathology:

No abnormalities were found at macroscopic post mortem examination of the animals.

Other findings:

Skin irritation: No irritation was noted for any of the animals at any time point.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Based on the results of the study, the dermal LD50 of the test article is greater than 2,000 mg/kg body weight and no skin irritation was noted in any animal at any time point.

Executive summary:

The acute dermal lethality and skin irritation potential of the test article was evaluated in three female Wistar rats. The test was performed according to OECD 402 (2017) and the study was conducted in compliance with OECD GLP (1997) regulations. The test article was suspended in 1% aqueous carboxymethyl cellulose. One day before dosing, an area of approximately 5x7 cm on the back of the animals was clipped. 2,000 mg/kg body weight of the test item was applied to each rat in an area of approximately 10% of the total body surface, i.e. approximately 18 cm² for females. The test item was held in contact with the skin with a dressing, consisting of a surgical gauze patch (Surgy 1D), successively covered with Coban elastic bandage. A piece of Micropore tape was additionally used for fixation of the bandages in females only. The application period was 24 hours, after which the dressing was removed and the skin cleaned of residual test item using water. The dose volume for each animal was based on the body weight measurement prior to dosing. A dose volume of 10 mL/kg body weight will be used for each dose. Post-dose observations were performed at periodic intervals on the day of dosing (at least three times) and once daily thereafter.  The observation period was 14 days. All the animals were examined for reaction to dosing.  The onset, intensity and duration of these signs was recorded (if appropriate), particular attention being paid to the animals during and for the first hour after dosing. Animals were weighed individually on Day 1 (pre-dose), 8 and 15. Skin reactions were assessed approximately 24, 48, and 72 hours after removal of the test article and scored using the standard Draize scoring method. No mortality ocurred during the study. No signs of systemic toxicity were noted.  No skin irritation was noted for any animals at any time point. Black staining of the treated skin was noted for the animals on Days 2 and/or 3. Additionally, blue discoloration of the skin was noted for one animal on Day 3.  This was considered to be due to the staining properties of the test item. The body weight gain shown by the surviving animals during the observation period was within the range expected for rats used in this type of study. No abnormalities were found at macroscopic post mortem examination of the animals. Based on the results of the study, the dermal LD50 of the test article is greater than 2,000 mg/kg body weight and no skin irritation was noted in any animal at any time point.