Methyl propionate

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 February 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

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 438 (Isolated Chicken Eye Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU method B.48 (Isolated chicken eye test method for identifying occular corrosives and severe irritants)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Methyl propionate

EC Number:

209-060-4

EC Name:

Methyl propionate

Cas Number:

554-12-1

Molecular formula:

C4H8O2

IUPAC Name:

methyl propanoate

Test material form:

liquid

Details on test material:

- Appearance: clear, colourless liquid
- Storage conditions: room temperature

Specific details on test material used for the study:

The solubility of the test material in physiological saline was tested prior to the experiment (30 mg test material in 1 mL physiological saline). The test material dissolved in physiological saline.

Test animals / tissue source

Species:

chicken

Strain:

other: ROSS 308

Details on test animals or tissues and environmental conditions:

SOURCE OF COLLECTED EYES
Chicken heads were collected after slaughter in a commercial abattoir from chickens (approximately 7 weeks old) which are used for human consumption. Heads were collected by a slaughter house technician and heads transported to the Test Facility at ambient temperature at the earliest convenience.

After collection, the heads were inspected for appropriate quality and wrapped with tissue paper moistened with saline, then placed in a plastic box which was closed (4-5 heads per box). The heads were received at the Test Facility and processed within 2 hours of collection.

Test system

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied: 30 µL

POSITIVE CONTROL
- Amount(s) applied: 30 µL
- Concentration (if solution): Benzalkonium chloride solution 5 % (w/v)

NEGATIVE CONTROL
- Amount(s) applied: 30 µL
- Concentration (if solution): physiological saline (0.9 % (w/v) NaCl) solution

Duration of treatment / exposure:

10 seconds

Duration of post- treatment incubation (in vitro):

240 minutes

Number of animals or in vitro replicates:

Three test material treated eyes, three positive control treated eyes and one negative control eye were examined during the study.

Details on study design:

SELECTION AND PREPARATION OF ISOLATED EYES
- Eyes Selection:
After removing the head from the plastic box, it was put on soft paper. The eyelids were carefully cut away with scissors, avoiding damaging the cornea. One small drop of 2 % (w/v) fluorescein solution was applied onto the cornea surface for a few seconds and subsequently rinsed off with 20 mL physiological saline. Then the fluorescein-treated cornea was examined with a hand-held slit lamp or slit lamp microscope, with the eye in the head, to ensure that the cornea was not damaged. If the cornea was in good condition, the eyeball was carefully removed from the orbit.

- Preparation of eyes:
The eye ball was carefully removed from the orbit by holding the nictitating membrane with a surgical forceps, while cutting the eye muscles with bent scissors. Care was taken to remove the eyeball from the orbit without cutting off the optical nerve too short. The procedure avoided pressure on the eye while removing the eyeball from the orbit, in order to prevent distortion of the cornea and subsequent corneal opacity. Once removed from the orbit, the eye was placed onto damp paper and the nictitating membrane was cut away with other connective tissue. The prepared eyes were kept on the wet papers in a closed box so that the appropriate humidity was maintained.

- Examination of eyes:
The prepared eye was placed in a steel clamp with the cornea positioned vertically with the eye in the correct relative position (same position as in the chicken head). Again avoid too much pressure on the eye by the clamp. Because of the relatively firm sclera of the chicken eyeball, only slight pressure was needed to fix the eye properly. The clamp with the eyeball was transferred to a chamber of the superfusion apparatus.
The clamp holding the eye was positioned in such a way that the entire cornea was supplied with physiological saline solution dripping from a stainless steel tube, at a rate of approximately 3-4 drops/minute or 0.1 to 0.15 mL/minutes. The door of the chamber was closed except for manipulations and examinations, to maintain temperature and humidity.
The appropriate number of eyes was selected and after being placed in the superfusion apparatus. There they were examined again with the slit lamp microscope to ensure that they were in good condition. The focus was adjusted to see clearly the physiological saline which was flowing on the cornea surface. Eyes with a high baseline fluorescein staining (i.e., > 0.5) or corneal opacity score (i.e., > 0.5) were rejected. The cornea thickness was measured, any eye with cornea thickness deviating more than 10 % from the mean value for all eyes, or eyes that showed any other signs of damage, were rejected and replaced.

EQUILIBRATION AND BASELINE RECORDINGS
- Acclimatisation time:
If the selected eyes were appropriate for the test, acclimatisation started and it was conducted for approximately 45 to 60 minutes. The chambers of the superfusion apparatus were at controlled temperature (32 ± 1.5 °C) during the acclimatisation and treatment periods.

- Baseline Assessments
At the end of the acclimatisation period, a zero reference measurement was recorded for cornea thickness and opacity to serve as a baseline (t=0) for each individual eye. The cornea thickness of the eyes should not change by more than 5 % within the -45 min and the zero time. No changes in thickness (0.0 %) were observed in the eyes in the experiment. Following the equilibration period, the fluorescein retention was measured. Baseline values were required to evaluate any potential test item related effect after treatment. All eyes were considered to be suitable for the assay.

NUMBER OF REPLICATES : Three test material treated eyes, three positive control treated eyes and one negative control eye were examined during the study.

APPLICATION DOSE AND EXPOSURE TIME
After the zero reference measurements, the eye in its retainer was taken out of the chamber and placed on a layer of tissue with the cornea facing upwards. The eye was held in horizontal position, while the test material was applied onto the centre of the cornea. For treatment, 30 µL of the test material was applied onto the entire surface of the cornea attempting to cover the cornea surface uniformly with the test item, taking care not to damage or touch the cornea.
The positive control eyes were treated in a similar way with 30 µL of benzalkonium chloride solution 5 % (w/v). The negative control eye was treated with 30 µL of physiological saline (0.9 % (w/v) NaCl) solution.

REMOVAL OF TEST SUBSTANCE
- Volume and washing procedure after exposure period:
The time of application was noted, then after an exposure period of 10 seconds from the end of the application the cornea surface was rinsed thoroughly with 20 mL physiological saline solution at ambient temperature, taking care not to damage the cornea but attempting to remove all residual test material if possible.

OBSERVATION PERIOD
The control eyes and test eyes were evaluated pre-treatment and at approximately 30, 75, 120, 180 and 240 minutes after the post-treatment rinse. Minor variations within approximately ± 5 minutes were considered acceptable.

Corneal thickness and corneal opacity were measured at all time points. Fluorescein retention was measured on two occasions, at baseline (t=0) and approximately 30 minutes after the post-treatment rinse. Haag-Streit Bern 900 slit-lamp microscope was used for the measurements.


MEASURED ENDPOINTS:
- Corneal swelling
- Corneal opacity
- Fluorescein retenion

Corneal swelling was calculated according to the following formulae:
CS at time t = ((CT at time t - CT at t=0) /CT at t=0) x 100
Mean CS at time t = (FECS(at time t)+ SECS(at time t) + TECS(at time t)) / 3

CS = cornea swelling
CT = cornea thickness
FECS(at time t) = first eye cornea swelling at a given time-point
SECS(at time t) = second eye cornea swelling at a given time-point
TECS(at time t) = third eye cornea swelling at a given time-point
Small negative numbers for swelling (0 to -5 %) following application are evaluated as class I. Large negative numbers (>12 % below control) are probably due to erosion and indicate a severe effect (scored as class IV). Values of -5 % to -12 % are evaluated on a case by case basis but in the absence of other findings do not indicate a severe effect (class II).

Cornea opacity was calculated according to the following formulae:
ΔCO at time t = CO at time t – CO at t=0
Mean ΔCOmax = (FECOmax(30min to 240min)+ SECOmax(30min to 240min) + TECOmax(30min to 240min)) / 3

CO at time t = cornea opacity at (30, 75, 120, 180 and 240) minutes after the posttreatment rinse
CO at t=0 = baseline cornea opacity
ΔCO at time t = difference between cornea opacity at t time and cornea opacity baseline
FECO = first eye cornea opacity
SECO = second eye cornea opacity
TECO= third eye cornea opacity
max(30min to 240min) = maximum opacity of the individual eye at 30 to 240 minutes minus baseline cornea opacity of the individual eye

Fluorescein retention was calculated according to the following formulae:
ΔFR at time t = FR at time t – FR at t=0
Mean ΔFR = (FEFR (30min) + SEFR(30min) + TEFR(30min)) / 3

FR at time t = fluorescein retention at 30 minutes after the post-treatment rinse
FR at t=0 = baseline fluorescein retention
ΔFR at time t = difference between fluorescein retention at t time and fluorescein retention baseline
FEFR = first eye fluorescein retention at 30 minutes after the post-treatment rinse minus baseline fluorescein retention
SEFR = second eye fluorescein retention at 30 minutes after the post-treatment rinse minus baseline fluorescein retention
TEFR = third eye fluorescein retention at 30 minutes after the post-treatment rinse minus baseline fluorescein retention


DECISION CRITERIA:
> Criteria for “No category” (all true)
- 3 endpoints classed as I or 2 endpoints classed as I and 1 endpoint classed as II
- No severe corneal morphological changes
- Test material was not stuck to the cornea at 240 minutes after the post-treatment rinse

> Criteria for “Category 1” (one or more true)
- 2 or more endpoints classed as IV
- Corneal opacity ≥ 3 at 30 min (in at least 2 eyes)
- Corneal opacity = 4 at any time point (in at least 2 eyes)
- Severe loosening of epithelium (in at least 1 eye)

> Criteria for “No prediction can be made” (one or two true)
- Based on the endpoints not classifiable for No Category, or for Category 1
- Particles of test material were stuck to the cornea and could not be washed off during the study

Results and discussion

In vitro

Results

Results 1

Irritation parameter:

cornea opacity score

Run / experiment:

mean

Value:

2.67

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Results 2

Irritation parameter:

percent corneal swelling

Run / experiment:

mean

Value:

2.7

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Mean maximum corneal swelling at up to 75 min

Results 3

Irritation parameter:

percent corneal swelling

Run / experiment:

mean

Value:

5.9

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Mean maximum corneal swelling at up to 240 min

Results 4

Irritation parameter:

fluorescein retention score

Run / experiment:

mean

Value:

3

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

TEST MATERIAL
Based on this in vitro eye irritation in the isolated chicken eyes test, the test material is classified as severely irritating, UN GHS Classification: Category 1

POSITIVE CONTROL
The positive control Benzalkonium chloride solution (5 % (w/v) was classified as severely irritating, UN GHS Classification: Category 1.

NEGATIVE CONTROL
The negative control Physiological saline was classified as non-irritating, UN GHS Classification: No Category.

VALIDITY OF THE TEST
The results from all eyes used met the quality control standards. The negative control and positive control results were within the historical data range in experiment. This experiment was considered to be valid

Any other information on results incl. tables

Table 1: Results

Treatment	Test Material		Positive control		Negative control
Observation	Value	ICE Class	Value	ICE Class	Value	ICE Class
Mean maximum corneal swelling at up to 75 min	2.7 %	I	11.5 %	II	0.0 %	I
Mean maximum corneal swelling at up to 240 min	5.9 %	II	27.5 %	III	0.0 %	I
Mean maximum corneal opacity	2.67	IV	4.00	IV	0.00	I
Mean fluorescein retention	3.00	IV	3.00	IV	0.00	I
Other Observations	None		Severe loosening of epithelium was observed in one eye at 120 minutes after the post- treatment rinse		None
Overall ICE Class	1 x II, 2 x IV		1 x III, 2 x IV		3 x I

Applicant's summary and conclusion

Interpretation of results:

other: EU Criteria: Category 1

Conclusions:

Based on this in vitro eye irritation in the isolated chicken eyes test, the test material is classified as severely irritating, UN GHS Classification: Category 1

Executive summary:

The potential of the substance to be an eye irritant was investigated in vitro following the standardised guideline OECD 438, under GLP conditions.

During the study, after the zero reference measurements, the eyes were held in a horizontal position and the test material was applied onto the centre of the cornea such that the entire surface of the cornea was covered in all cases. After 10 seconds, the surface of the eyes was rinsed with physiological saline solution. Three eyes were treated with 30 µL test material. The three positive control eyes were treated in a similar way with 30 µL benzalkonium chloride solution 5 % (w/v). The negative control eye was treated with 30 µL of physiological saline (0.9 % (w/v) NaCl solution). Corneal thickness, corneal opacity and fluorescein retention were measured and any morphological effects (e.g. pitting or loosening of the epithelium) were evaluated.

The results from all eyes used in the study met the quality control standards. The negative control and positive control results were within the historical control data range in the experiment. Thus, the experiment was considered to be valid.

Slight corneal swelling (mean 5.9 %) was observed during the four-hour observation period on test material treated eyes. Severe cornea opacity change (severity 2 on one eye and severity 3 on two eyes) was observed on three eyes. Severe fluorescein retention change (severity 3) was noted on all three eyes. No other corneal effect was observed.

Based on this in vitro eye irritation in the isolated chicken eyes test, the test material is classified as severely irritating, UN GHS Classification: Category 1.