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Toxicological information

Eye irritation

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Administrative data

Endpoint:
eye irritation: in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
between 1 March 1993 and 5 March 1993.
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1993
Report date:
1993

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 405 (Acute Eye Irritation / Corrosion)
Deviations:
not applicable
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
2-bromo-6-(4-methylbenzoyl)pyridine
EC Number:
618-079-0
Cas Number:
87848-95-1
Molecular formula:
C13H10BrNO
IUPAC Name:
2-bromo-6-(4-methylbenzoyl)pyridine
Specific details on test material used for the study:
45W81 (2-bromo-6-(4-toluoyl)-pyridine), batch BXC67
Prior to use, the test article was stored in a closed container at room temperature in darkness.

Test animals / tissue source

Species:
rabbit
Strain:
New Zealand White
Details on test animals or tissues and environmental conditions:
Three young adult female New Zealand White rabbits were selected from the stock colony originally received from Froxfield farms, Froxfield, Petersfield, Hampshire and were in the weight range 3.89-5.08kg at the start of the study. No formal randomisation procedure was adopted. The animals were individually identified by means of a unique number on a metal ear tag plus a six digit experimental animal number.
The animals were individually housed in plastic grid floor cages in a single air conditioned room, Room 7, Building 88 East Wing, routinely maintained at a temperature between 16 and 20°C and a constant daily photoperiod of 12 hours artificial light, 12 hours darkness. The animals were acclimatised for approximately 2 weeks prior to the start of dosing.
Pelleted diet (FD1 SQC, Batch No: 8623, Special Diet Services Ltd., Manea, Cambs) and tap water (Thames Water Authority) were provided ad libitum. The diet and drinking water were considered not to contain any contaminant at a level that might have affected the purpose or integrity of the study.

Test system

Vehicle:
unchanged (no vehicle)
Controls:
yes, concurrent no treatment
Amount / concentration applied:
0.1g
no vehicle
Observation period (in vivo):
Irritancy scoring was performed 1, 6, 24, 48 and 72 hours after instillation. At the 72 hour observation there were no scores for any of the parameters assessed, and the study was terminated.
Number of animals or in vitro replicates:
3 females
Details on study design:
Experimental Design
One rabbit was held firmly but gently until quiet. A 'cup' was formed by gently pulling the lower lid of the right eye away from the eyeball and 0.1 g of the test material was placed inside. Both the upper and lower eye lids were then held together for about 2 seconds then released. The left eye was used as an untreated control for comparison.
The remaining rabbits were dosed the following day because at this time the first animal showed only low grade reactions and the animal itself showed no signs of distress, discomfort or interference with the treated eye.

Observations
On the day prior to dose administration the bodyweight of the animal was recorded and each eye examined with fluorescein stain (Fluorets) for any abnormalities.

Clinical Signs / Procedures
Irritancy scoring was performed 1, 6, 24, 48 and 72 hours after instillation. At the 72 hour observation there were no scores for any of the parameters assessed, and the study was terminated.
Ocular irritation was scored in accordance with the Draize system.

Bodyweights were measured on the day before dosing.
The animals were killed after termination of the study. No necropsy was performed.

Results and discussion

In vivo

Resultsopen allclose all
Irritation parameter:
cornea opacity score
Basis:
animal #1
Time point:
24/48/72 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
cornea opacity score
Basis:
animal #2
Time point:
24 h
Score:
1
Max. score:
4
Reversibility:
fully reversible within: 48h
Irritation parameter:
cornea opacity score
Basis:
animal #2
Time point:
48 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
cornea opacity score
Basis:
animal #2
Time point:
72 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
cornea opacity score
Basis:
animal #3
Time point:
24/48/72 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
iris score
Basis:
mean
Time point:
24/48/72 h
Score:
0
Max. score:
2
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
conjunctivae score
Basis:
animal #1
Time point:
24/48/72 h
Score:
0
Max. score:
3
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
conjunctivae score
Basis:
animal #2
Time point:
24/48/72 h
Score:
0
Max. score:
3
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
conjunctivae score
Basis:
animal #3
Time point:
24 h
Score:
1
Max. score:
3
Reversibility:
fully reversible within: 48h
Irritation parameter:
conjunctivae score
Basis:
animal #3
Time point:
48 h
Score:
0
Max. score:
3
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
conjunctivae score
Basis:
animal #3
Time point:
72 h
Score:
0
Max. score:
3
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
chemosis score
Basis:
mean
Time point:
24/48/72 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation

Any other information on results incl. tables

Instillation of 45W81 into the rabbit eye produced signs of low grade conjunctivitis in all animals, up to 24 hours after dosing. At 24 hours after instillation, one rabbit also had low density corneal opacity. All reactions regressed rapidly and by the 48 hour time point, all treated eyes appeared normal.

Applicant's summary and conclusion

Interpretation of results:
Category 2B (mildly irritating to eyes) based on GHS criteria
Conclusions:
According the eighth revised edition of GHS (2019) criteria, for a substance to meet the classification of Category 2/2A it must produce in at least 2 of 3 tested animals a positive response of ≥1 for corneal opacity and/or iritis and/or ≥2 for conjunctivae and/or chemosis, calculated as a mean score following grading at 24, 48 and 72 hours after instillation. It goes on to state that the grading criteria are as described in OECD 405.

The scale for scoring of the original study follows the same principles, but are graded with a modified Kay and Calandra interpretation. Using the raw data which is reported above, it can be seen that the requirements in the GHS criteria for classification are not met, as while an individual score at 24h for one rabbit demonstrated a corneal opacity of 1, the mean is less than one and all other time points score as 0. Furthermore no Conjunctivae score is greater than 2, in fact again only one animal demonstrates a score of 1 at the 24 hour time point, and all iris and chemosis scores are 0.

However, the conclusion of the original study was that the observed reactions and the subsequent rate of regression, were considered sufficient to stablish 45W81 as a slight irritant, according to the Kay and Calandra scoring system.

At the 1 hour and 6 hour time points, conjunctivae and chemosis are shown with a score of 1 in animal 1 and animal two had a score of 1 for conjunctivae at 1h and 6h also. so effects were observed.

It is therefore proposed as a worst case conclusion that the classification be made according to the Category 2B criteria from GHS, where an eye irritant is considered mildly irritating to eyes when the effects listed above are fully reversible within 7 days of observation. In the study, all reactions regressed rapidly and by the 48 hour time point, all treated eyes appeared normal.

So while the Category 2/2A criteria are not met, as a worst case we propose the classification should be Category 2B under GHS.
However, Category 2B is not currently an option under EU CLP, and therefore the classification should be Category 2 in this instance.