Benzimidazole

Endpoint summary

Description of key information

Skin irritation

The dermal irritation potential of target chemical Benzimidazole (CAS No: 51-17-2) was assessedin various in- vitro and in-vivo experimental studies.Based on the available key data and supporting studies,it can be concluded thatchemical Benzimidazole (CAS No: 51-17-2) is unable to cause skin irritation and considered as not irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Not Classified”.

 

Eye irritation

Data available for the structurally and functionally similar read across chemicals has been reviewed to determine the ocular irritation potential of the test chemical Benzimidazole (CAS No: 51-17-2). Based on the summarized studies for target chemical Benzimidazole (CAS No: 51-17-2) and its structurally similar read across substances,it can be concluded that the testchemical is not able to cause eye irritation and considered as not irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Not Classified”.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

December 04, 2017 to March 13, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Data is from experimental study report

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Principles of method if other than guideline:

The purpose of this study is to provide classification of dermal irritation potential of a chemical by using a three-dimensional human epidermis model, according to the OECD Test Guideline No. 439, “In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method”.

GLP compliance:

yes

Specific details on test material used for the study:

Name of test material : Benzimidazole
Molecular formula : C7H6N2
Molecular weight :118.1384 g/mol
Smiles notation : c12c(nc[nH]1)cccc2
InChl : 1S/C7H6N2/c12476(31)8597/h15H,(H,8,9)
Substance Type: Organic
Physical State: Solid

Test system:

human skin model

Remarks:

MatTek EpiDerm™ Tissue Model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: EpiDerm™ 3-dimensional human tissues used in this study

Source strain:

other: Not applicable

Details on animal used as source of test system:

EpiDerm™ tissues, Lot No. 27646 Kits I and J, were received from MatTek on 12 Dec 2017, and Lot No. 27654 Kits O and P, were received from MatTek on 19 Dec 2017. All tissues were refrigerated at 2-8°C upon receipt. Before use, the tissues were incubated (37±1°C, 5±1% CO2) with assay medium (MatTek) for a one-hour equilibration. The tissues were then moved to new wells with fresh medium for an additional overnight equilibrium, for 18±3 hours. Equilibration medium was replaced with fresh medium before dosing.

Justification for test system used:

The EpiDerm™ Skin Model closely parallels human skin, thus providing a useful in vitro means to assess dermal irritancy and toxicology

Vehicle:

unchanged (no vehicle)

Details on test system:

EpiDerm™ Tissue Samples
EpiDerm™ tissues, Lot No. 27646 Kits I and J, were received from MatTek on 12 Dec 2017, and Lot No. 27654 Kits O and P, were received from MatTek on 19 Dec 2017 All tissues were refrigerated at 2-8°C upon receipt. Before use, the tissues were incubated (37±1°C, 5±1% CO2) with assay medium (MatTek) for a one-hour equilibration. The tissues were then moved to new wells with fresh medium for an additional overnight equilibrium, for 18±3 hours. Equilibration medium was replaced with fresh medium before dosing.

Mesh Compatibility
Five of the test articles supplied were liquids. These test articles were assessed for compatibility with pre-cut nylon mesh supplied with the tissues. The mesh was placed on a slide and 30 μl of a liquid test articles or PBS (negative control) were applied. After 60 minutes of exposure, the mesh was checked microscopically. If no damage or other interaction was observed, indicating that the mesh was compatible with the test article, the mesh was used as a spreading aid.

Tissue Viability (MTT Reduction)
At the end of the incubation period, each EpiDerm™ tissue was rinsed with PBS and transferred to a 24-well plate containing 300 μl of MTT solution (1 mg/ml MTT in DMEM). The tissues were then returned to the incubator for a three-hour MTT incubation period. Following the MTT incubation period, each EpiDerm™ tissue was rinsed with PBS and then treated with 2.0 ml of extractant solution (isopropanol) per well for at least two hours, with shaking, at room temperature. Two aliquots of the extracted MTT formazan were measured at 540 nm using a plate reader (μQuant Plate Reader, Bio-Tek Instruments, Winooski, VT).
For several tissues, the test article had stained the tissues. Therefore, the tissues were extracted with only 1.0 ml, allowing extraction to occur only through the bottom of the insert. After the extraction period, the tissue insert was removed and discarded and 1.0 ml of extraction solution were added to each well, bringing the volume to a total of 2.0 ml.

Quality Controls
The assay meets the acceptance criteria if the mean OD540 of the negative control tissues is between 1.0 and 2.5, inclusive, and the mean viability of positive control tissues, expressed as percentage of the negative control tissues, is at least 20%. In addition, the standard deviation (SD) calculated from individual percent tissue viabilities of the three identically-treated replicates must be less than 18%.
Note: Chemicals that provide tissue viabilities in a range of 30% to 70% may provide high SD. If the high SD (above acceptance limits) is typical for the chemical and the classification of the chemical is consistent in all independent runs, MatTek recommends that this result be accepted, although it did not meet the Assay Acceptance Criterion.

Analysis of Data
See Table 1 for Experimental Data. The mean absorbance value for each time point was calculated from the optical density (OD) of the duplicate samples and expressed as percent viability for each sample using the following formula:
% viability = 100 X (OD sample/OD negative control)

Skin Irritation Prediction
According to the EU1,2 and GHS3 classification (R38 / Category 2 or no label), an irritant is predicted if the mean relative tissue viability of three individual tissues exposed to the test substance is 50% or less of the mean viability of the negative controls.

In vitro result In vivo Classification
Mean tissue viability ≤ 50% Category 2
Mean tissue viability > 50% Non-irritant (NI)


Assessment of direct MTT reduction and assessment of coloring or staining materials was not performed. Therefore, it cannot be fully assessed if the test articles interfered with MTT viability measurements.

Retention of Data
Upon signing the final report, all raw data, supporting documentation and reports are submitted to the Archivist by the Study Director. The raw data are filed at MB Research by project number. The final report is filed at MB Research by Sponsor name and MB project number.
All data generated during the conduct of this study will be archived at MB Research for at least one year from the date of the final report and optionally longer at additional cost. The Sponsor will be contacted in writing to determine final disposition of the records.
Any remaining test article will be discarded upon submission of the report.

Amendment to the Protocol
There were no amendments to the protocol. See Appendix C for the protocol in its entirety
Evaluation of Test Article in the Cell Models:
1. Cell system: Upon receipt, the MatTek EpiDerm™ tissue cultures were placed in 0.9 mL of fresh Maintenance medium (in a 6-well plate). The culture inserts are incubated for ~one hour. The tissues were then transferred to 6-well plates containing 0.9 mL fresh Maintenance medium and they were incubated overnight at ~37°C, 5% CO2 in a humidified incubator.

2. Control and Test Article Exposures: On the day of dosing, the tissues are then removed from the incubator and the controls and the test article are applied topically to tissues by pipette. Tissues were exposed to controls and the test articles for one hour, with ~35 minutes in a 37°C, 5% CO2 humidified incubator and the remaining 25 minutes at room temperature.

a) Controls
30 µL of negative control DPBS, positive control 5% SDS was applied topically to the tissue and gently spread by placing a nylon mesh on the apical surface of each tissue, if necessary.

b)Test Article
For solid test article, the tissues were moistened with 25 μL of ultrapure water to improve contact of the tissue surface with the test article. Approximately 25 mg of each test article was evenly applied to the apical surface of each tissue (n=3). All the tissues were placed into the ~37°C incubator with 5% CO2. The exposure times were approximately 1 hour, with ~35 minutes exposure in the incubator and ~25 minutes at room temperature.

3.Post-exposure treatment
After the 1 hour exposure, the tissues were rinsed 20 to 25 times with 1 mL of DPBS. The apical surface was gently blotted with a cotton swab. The tissues were placed in 0.9 mL of fresh Maintenance medium (6-well plate) for either 25 hours, 38 minutes and 23 seconds or for 24 hours, 10 minutes and 09 seconds (as there were numerous tissues, they had to be broken down into 2 sets to complete dosing in a timely manner). After this initial ~24 hour incubation, the tissues were placed in 6-well plates containing 0.9 mL fresh Maintenance medium and incubated for another 17 hours, 03 minutes and 34 seconds prior to performing the MTT assay, for a total of an approximately 42 hour post-exposure incubation.

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: The EpiDerm™ 3 dimensional human tissue model
- Tissue Lot number(s): 26459
- Date of initiation of testing: 6/08/2017

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37°C
- Temperature of post-treatment incubation (if applicable): 37°C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: Twice

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 300 µL MTT medium (1.0 mg/mL).
- Incubation time: After 2 hours, 57 minute and 25 second MTT incubation
- Spectrophotometer: Synergy H4 spectrophotometer
- Wavelength: 570 nm
- Filter: No data
- Filter bandwidth: No data
- Linear OD range of spectrophotometer: No data

NUMBER OF REPLICATE TISSUES: 3

CALCULATIONS and STATISTICAL METHODS
All data were background subtracted before analysis. MTT data are presented as % viable compared to negative control. Data were generated as follows:

MTT Assay
Blanks:
·        The optical density (OD) mean from all replicates for each plate (ODblank).

Negative Controls (NC):
Identity: Phosphate-Buffered Saline (PBS), Lot No. AC10239794
Provided by:MatTek
Date Received:12 Dec 2017 and 19 Dec 2017
Expiration Date:18 Jul 2018
Storage:Room temperature and humidity
Description:Clear colorless liquid
Sample Preparation:Used as received

Positive Control (PC):
Identity: 5% Sodium Dodecyl Sulfate (SDS), Lot No. 071817MAB
Provided by:MatTek
Date Received:12 Dec 2017 and 19 Dec 2017
Expiration Date:18 Jul 2018
Storage:Room temperature and humidity
Description:Clear colorless liquid
Sample Preparation:Used as received

- Assay quality controls
- Negative Controls (NC)
The Dulbecco’s phosphate buffered saline (DPBS) was used as a NC. The assay passed all acceptance criteria if the ODs of the negative control exposed tissues were between ≥0.8 and ≤2.8.
 
- Positive Controls (PC)
5% solution of sodium dodecyl sulfate was used as a PC. The assay is meeting the acceptance criteria if the viability of the PC is ≤20% of the negative control.
 
- Standard Deviation (SD)
The standard deviation (SD) calculated from individual percent tissue viabilities of the test article exposed replicates was ≤18.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 25 mg
- Concentration (if solution): neat (undiluted)

VEHICLE (Not used)
- Amount(s) applied (volume or weight with unit): none
- Concentration (if solution): none
- Lot/batch no. (if required): none
- Purity: none

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL
- Concentration (if solution): neat

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL
- Concentration (if solution): 5% solution of sodium dodecyl sulfate

Duration of treatment / exposure:

Tissues will be topically exposed to the test article and control articles for 60 minutes.

Duration of post-treatment incubation (if applicable):

After dosing, the tissues will be returned to the incubator for 35 ±1 minute, and then returned to the sterile hood for the remainder of the 60-minute exposure period.

Number of replicates:

All treatments with test articles and controls will be dosed in triplicate EpiDerm™ tissues.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Run 1

Value:

101.3

Vehicle controls validity:

not specified

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

All treatments with test articles and controls will be dosed in triplicate EpiDerm™ tissues.

In vitro result In vivo Classification
Mean tissue viability ≤ 50% Category 2
Mean tissue viability > 50% Non-irritant

Interpretation of results:

other: not irritating

Conclusions:

The dermal irritation potential of test article was determined according to the OECD 439 test guideline followed for this study. The Mean % tissue viability compared to negative control (n=3) of the test substance Benzimidazole, CAS No. 51-17-2 was determined to be 101.3%. Thus, Benzimidazole was considered to be not irritating to the human skin.

Executive summary:

The dermal irritation potential of test article was determined according to the OECD 439 In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method”. The MatTek EpiDerm™ model was used to assess the potential dermal irritation of the test article by determining the viability of the tissues following exposure to the test article via MTT. The objective of this study was to assess the dermal irritation potential of test article Tissues were exposed to test article and controls for ~one hour, followed by a 42 hour post-exposure recovery period. The viability of each tissue was determined by MTT assay. 

The MTT data shows that the assay quality controls were met. The mean tissue viabilities for the Positive control, Methyl acetate were 6.5%, 10.7% respectively in the first and second run, whereas the tissue viabilities of the negative control, Tissue culture water remained at 100% in the both the runs.

The Mean % tissue viability compared to negative control (n=3) of the test substance Benzimidazole, CAS No. 51-17-2 was determined to be 101.3%.

Hence, under the experimental test conditions it was concluded that test substance Benzimidazole, CAS No. 51-17-2 was considered to be not irritating to the human skin and being classified as “Not Classified'' as per CLP Regulation.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

experimental data of read across substances

Justification for type of information:

Data for the target chemical is summarized based on the structurally similar read across chemicals

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: as mentioned below

Principles of method if other than guideline:

WoE report is based on 2 eye irritation studies as- WoE-2 and WoE-3.
An eye irritation study of test chemical was conducted on rabbits to assess its eye irritating effects.

GLP compliance:

not specified

Specific details on test material used for the study:

Name of test material: Benzimidazole
Molecular formula: C7H6N2
Molecular weight: 118.1384 g/mol
Smiles notation: c12c(nc[nH]1)cccc2
InChl: 1S/C7H6N2/c12476(31)8597/h15H,(H,8,9)
Substance Type: Organic
Physical State: Solid

Species:

rabbit

Strain:

other: 1.New Zealand White 2.albino

Details on test animals or tissues and environmental conditions:

1.- Source: Institute for Industrial Research & Toxicology
- Age at study initiation: 10 to 12 weeks
- Weight at study initiation: 2.0kg ±200g
- Housing: Rabbit was housed in stainless steel cages provided with stainless steel mesh bottom and facilities for food and water bottle.
- Diet (e.g. ad libitum):Pelleted feed supplied ad libitum
- Water (e.g. ad libitum): Community tap water passed through ‘Aqua Guard on line water filter’ was kept in bottles, ad libitum.
- Acclimation period: The rabbit was acclimatized to standard laboratory condition for 24 hours in experimental room before study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C):22-25 degC
- Humidity (%):40-60%
- Air changes (per hr):10-15 air changes per hour
- Photoperiod (hrs dark / hrs light): illumination cycle set to 12 hours artificial fluorescent light and 12 hours dark.

2.not specified

Vehicle:

other: 1.unchanged (no vehicle) 2.not specified

Controls:

other: 1. yes 2.not specified

Amount / concentration applied:

1.TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.1 gm

2.75% wettable powder formulation

2.

Duration of treatment / exposure:

1.21 days
2.single exposure

Observation period (in vivo):

1.1, 24, 48 and 72 hours. To determine the reversibility of the effect the animal was observed normally for 21 days.
2.4 days

Number of animals or in vitro replicates:

1.Three female rabbits
2.9 (6 eyes remained unwashed and 3 eyes were washed)

Details on study design:

1.REMOVAL OF TEST SUBSTANCE
- Washing (if done):after 24 hrs.

2.REMOVAL OF TEST SUBSTANCE
- Washing (if done): yes, for 3 rabbits of the 9


SCORING SYSTEM: Draize

TOOL USED TO ASSESS SCORE: Biomicroscope and hand slit lamp further examined with the aid of fluorescein.

2.

Irritation parameter:

other: 1.overall irritation score

Basis:

mean

Time point:

21 d

Score:

0

Reversibility:

not specified

Remarks on result:

no indication of irritation

Irritation parameter:

overall irritation score

Basis:

mean

Time point:

other: 4 days

Score:

0

Reversibility:

not specified

Remarks on result:

no indication of irritation

Irritant / corrosive response data:

1.The test compound when applied to the eye of New Zealand white rabbit at the dose level of 0.1 gm did not produce any eye irritation. Furthermore, any lesions such as pannus, staining were not recorded throughout the observation period of 72 hours.
2.not irritating to the eyes of albino rabbits

Other effects:

1.Clinical Signs: The test compound applied in conjunctival sac of rabbits at the dose level of 0.1 gm did not show any observable clinical signs such as cage side activity and pain or stress etc. throughout the observation period of 21 days.
2.not irritating to the eyes of albino rabbits

1.

GRADING OF OCULAR LESIONS

 

S.NO/ SEX		OBSERVATION	Score				Total	Total Score
1/F			1 hour	24hours	48 hours	72 hours
	Cornea	A.       Opacity-Degree of Density	0	0	0	0	0	0×0×5=0
		B.       Area of Cornea Involved	0	0	0	0	0
	Iris	A.       Values	0	0	0	0	0	0
	Conjunctivae	A.       Redness	0	0	0	0	0	0+0+0×5=0
		B.       Chemosis	0	0	0	0	0
		C.       Discharge	0	0	0	0	0
2/F	Cornea	A.       Opacity-Degree of Density	0	0	0	0	0	0×0×5=0
		B.       Area of Cornea Involved	0	0	0	0	0
	Iris	A.       Values	0	0	0	0	0	0
	Conjunctivae	A.       Redness	0	0	0	0	0	0+0+0×5=0
		B.       Chemosis	0	0	0	0	0
		C.       Discharge	0	0	0	0	0
3/F	Cornea	A.       Opacity-Degree of Density	0	0	0	0	0	0×0×5=0
		B.       Area of Cornea Involved	0	0	0	0	0
	Iris	A.       Values	0	0	0	0	0	0
	Conjunctivae	A.       Redness	0	0	0	0	0	0+0+0×5=0
		B.       Chemosis	0	0	0	0	0
		C.       Discharge	0	0	0	0	0
Grand total								0.00
Mean								0.00
Eye Irritation Scoring index								0.00

 

Interpretation of results:

other: Not irritating

Conclusions:

The test chemical Benzimidazole (CAS No: 51-17-2) was considered to be not irritating to the eyes of treated rabbits.

Executive summary:

Data available for the structurally and functionally similar read across chemicals has been reviewed to determine the ocular irritation potential of the test chemical Benzimidazole (CAS No: 51-17-2). The studies are as mentioned below:

 

The acute eye irritation study of similar read across chemical was conducted in New Zealand White Rabbits as per the Guideline OECD- 405. Initial study of test chemical was conducted on one healthy rabbits of body weight 2.0kg. Both eyes of rabbits were examined for any abnormal disch arge such as eye irritation, ocular defects or pre-existing corneal injury from eye 24 hours prior to application of test compound. The test compound when applied to conjunctival sac of rabbit in the amount of 0.1gm did not produce any eye irritation during the observation period. Furthermore, no other clinical signs were recorded after application of test compound such as cage side activity, pain etc. The result obtained from the initial test was confirmed in additional two animals of same sex and same dose level (OECD-405). Test compound was applied in the amount of 0.1 gm in the conjunctival sac of each rabbit after gently pulling the lower lid away from the eyeball. The other eye which remain untreated, served as a control. The acute irritation to eye conjunctiva, cornea and iris was evaluated at 1, 24, 48 and 72 hours after the treatment. The grades of ocular reaction (conjunctiva, cornea and iris) were recorded at each observation. To determine the reversibility of the effect the animals were observed normally for 21 days. Any other lesions in the eye viz pannus, staining were observed and scored accordingly. Examination of reactions was facilitated by use of biomicroscope and hand slit lamp. Test compound applied to the conjunctival sac of the rabbits at the dose level of 0.1 gm did not produce any eye irritation as well as eye discharge. Furthermore, there was no other clinical sign recorded in both of the animals during the whole observation period for 21 days. Based on above findings, it can be concluded that the test compound was practically non-irritant when applied in the amount of 0.1 gm in the conjunctival sac of the rabbits.

 

The above result was supported by the primary ocular irritation potential of another read across chemical which was assessed on albino rabbits. The chemical was instilled into eyes of 9 albino rabbits as a 75% wettable powder formulation. The eyes of 3 rabbits of 9 were washed after sometime (duration not mentioned), remaining rabbit eyes were unwashed. The rabbits were observed for ocular lesions for 4 days. The test chemical induced transient corneal opacity in six of six unwashed and two of three washed eyes. Microscopic examination confirmed the corneal opacity as mild to moderate. Conjunctival irritation (redness, swelling, discharge) was also transient. All eyes were normal after four days. The irritation response was probably related to the inert ingredients in the wettable powder formulation. Since the irritation was due to inert ingredients in the formulation, but not caused due to test substance, it can be considered that the test material was not an eye irritant.

 

Based on the above summarized studies for target chemical Benzimidazole (CAS No: 51-17-2) and its structurally similar read across substances,it can be concluded that the testchemical is not able to cause eye irritation and considered as not irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Not Classified”.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation:

Various studieshas been investigated for the test chemicalBenzimidazole (CAS No: 51-17-2)to observe the potential for dermal irritation to a greater or lesser extent. The studies are based on in-vitro and in-vivo experiments conducted for target chemicalBenzimidazole (CAS No: 51-17-2) and its structurally similar read across substanceswhich have beensummarized as below;

 

The dermal irritation potential of test article Benzimidazole (CAS No: 51-17-2) was determined according to the OECD 439 In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method”. The MatTek EpiDerm™ model was used to assess the potential dermal irritation of the test article by determining the viability of the tissues following exposure to the test article via MTT. The objective of this study was to assess the dermal irritation potential of test article Tissues were exposed to test article and controls for ~one hour, followed by a 42 hour post-exposure recovery period. The viability of each tissue was determined by MTT assay.  The MTT data shows that the assay quality controls were met. The mean tissue viabilities for the Positive control, Methyl acetate were 6.5%, 10.7% respectively in the first and second run, whereas the tissue viabilities of the negative control, Tissue culture water remained at 100% in the both the runs. The Mean % tissue viability compared to negative control (n=3) of the test substance Benzimidazole, CAS No. 51-17-2 was determined to be 101.3%. Hence, under the experimental test conditions it was concluded that test substance Benzimidazole, CAS No. 51-17-2 was considered to be not irritating to the human skin and being classified as “Not Classified'' as per CLP Regulation.

 

The in-vivo Skin irritation study of test chemical Benzimidazole (CAS No: 51-17-2) was carried out in humans that support the above mentioned result. 16 females aged 32 to 55 year old participated in the study. The test chemical concentration of 0.2 ml was applied in duplicate to the left and right sides of the back approximately 3 cm away from and parallel to the midline. The humans were exposed for 2 days and observed up to 3 days. The skin sites were evaluated for erythema and edema scores and also checked for redness of the skin. The mean erythema and edema scores after 24 hours were 0.62, 0.0 respectively. Based on the scores, Benzimidazole can be considered as not irritating to skin.

 

The above results were supported by dermal irritation study conducted for similar read across chemical in New Zealand White Rabbits according to guideline OECD-404. In the initial test one healthy rabbit of body weight 2.24 kg selected for study after acclimatization. The test compound in the amount of 0.5 gm was applied at the different sites on the shaven back skin of animal. Since no corrosive effect was observed in the initial test, a confirmatory test was done using two additional animals. In the confirmatory test the test compound in the amount of 0.5 gm was applied on the shaven back skin of two animals (body weight ranges 2.14 and 2.09 kg), each with one patch, for an exposure period of four hours. After four hours the patch was removed and the skin reactions were graded according to Draize’s method. The test compound did not produce any dermal irritation in terms of erythema or edema in any of the animals after the four hours application. Both the animals were also free from any clinical signs of toxicity throughout the observation period of 14 days. The dermal irritation index of New Zealand white rabbits was calculated as 0.00. Thus based on result obtained, it can be concluded that the test compound was considered to be non-irritant to skin of the New Zealand white under test condition.

 

The overall results were further supported by the primary dermal irritation study of another read across chemical performed on New Zealand White rabbits. About 5‐g aliquot of chemical was applied to the intact, clipped skin of six New Zealand white rabbits for 4 h. The test sites were evaluated for erythema, oedema, and other evidence of dermal effects and were scored according to the Draize scale. No dermal irritation was seen at any time during the study. Thus the test material was considered to be not irritating to skin.

 

Thus on the basis of results obtained in key and supportingstudies,it can be concluded that the testthe chemical Benzimidazole (CAS No: 51-17-2) is not able to cause skin irritation and considered as not irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Not Classified”.

 

Eye irritation

Data available for the structurally and functionally similar read across chemicals has been reviewed to determine the ocular irritation potential of the test chemical Benzimidazole (CAS No: 51-17-2). The studies are as mentioned below:

 

The acute eye irritation study of similar read across chemical was conducted in New Zealand White Rabbits as per the Guideline OECD- 405. Initial study of test chemical was conducted on one healthy rabbits of body weight 2.0kg. Both eyes of rabbits were examined for any abnormal disch arge such as eye irritation, ocular defects or pre-existing corneal injury from eye 24 hours prior to application of test compound. The test compound when applied to conjunctival sac of rabbit in the amount of 0.1gm did not produce any eye irritation during the observation period. Furthermore, no other clinical signs were recorded after application of test compound such as cage side activity, pain etc. The result obtained from the initial test was confirmed in additional two animals of same sex and same dose level (OECD-405). Test compound was applied in the amount of 0.1 gm in the conjunctival sac of each rabbit after gently pulling the lower lid away from the eyeball. The other eye which remain untreated, served as a control. The acute irritation to eye conjunctiva, cornea and iris was evaluated at 1, 24, 48 and 72 hours after the treatment. The grades of ocular reaction (conjunctiva, cornea and iris) were recorded at each observation. To determine the reversibility of the effect the animals were observed normally for 21 days. Any other lesions in the eye viz pannus, staining were observed and scored accordingly. Examination of reactions was facilitated by use of biomicroscope and hand slit lamp. Test compound applied to the conjunctival sac of the rabbits at the dose level of 0.1 gm did not produce any eye irritation as well as eye discharge. Furthermore, there was no other clinical sign recorded in both of the animals during the whole observation period for 21 days. Based on above findings, it can be concluded that the test compound was practically non-irritant when applied in the amount of 0.1 gm in the conjunctival sac of the rabbits.

 

The above result was supported by the primary ocular irritation potential of another read across chemical which was assessed on albino rabbits. The chemical was instilled into eyes of 9 albino rabbits as a 75% wettable powder formulation. The eyes of 3 rabbits of 9 were washed after sometime (duration not mentioned), remaining rabbit eyes were unwashed. The rabbits were observed for ocular lesions for 4 days. The test chemical induced transient corneal opacity in six of six unwashed and two of three washed eyes. Microscopic examination confirmed the corneal opacity as mild to moderate. Conjunctival irritation (redness, swelling, discharge) was also transient. All eyes were normal after four days. The irritation response was probably related to the inert ingredients in the wettable powder formulation. Since the irritation was due to inert ingredients in the formulation, but not caused due to test substance, it can be considered that the test material was not an eye irritant.

 

Based on the above summarized studies for target chemical Benzimidazole (CAS No: 51-17-2) and its structurally similar read across substances,it can be concluded that the testchemical is not able to cause eye irritation and considered as not irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Not Classified”.

Justification for classification or non-classification

The skin and eye irritation potential of test chemical Benzimidazole (CAS No: 51-17-2)  and its structurally and functionally similar read across substanceswere observed in various studies. The results obtained from these studies indicate that the chemical  is unlikely to cause skin and eye irritation. Hence Benzimidazole (CAS No: 51-17-2)  can be classified under the category “Not Classified” for skin and eye as per CLP.