Strontium bis(2-ethylhexanoate)

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-01-31

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 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

Version / remarks:

2017-10-09

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2015-06-05

Test material

Test material information

Constituent 1

Reference substance name:

Strontium bis(2-ethylhexanoate)

EC Number:

219-536-3

EC Name:

Strontium bis(2-ethylhexanoate)

Cas Number:

2457-02-5

Molecular formula:

C16H30O4Sr

IUPAC Name:

strontium bis(2-ethylhexanoate)

Test material form:

solid: particulate/powder

Details on test material:

- State of aggregation: solid, white powder

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature, avoid heat

The test item was treated as non-surfactant solid. This information was derived by extrapolating the experimental data from a soluble metal carboxylate: calcium bis(2-ethylhexanoate) was previously tested for surface tension and water solubility. The surface tension of a 1 g/L solution of calcium bis(2-ethylhexanoate) at 20 °C was determined to be 60.22 mN/m. Due to the fact that the surface tension was ≥ 60 mN/m, it was determined as a not surface-active substance. The water solubility of calcium bis(2-ethylhexanoate) was determined to be 80.4 ± 4.6 g/L. Preliminary results on water solubility for the test item strontium bis(2-ethylhexanoate) indicated a water solubility of 700 mg/L. Due to the lower water solubility of the test item compared to the non-surface-active calcium bis(2-ethylhexanoate) it can be safely assumed that the test item will not display surface-active properties. In general, surface active properties increase with increasing water solubility, due to the higher amount of free carboxylate anions and vice versa.

Test animals / tissue source

Details on test animals or tissues and environmental conditions:

SOURCE OF COLLECTED EYES
- Source: abattoir A. Moksel AG, Buchloe, Germany
- Characteristics of donor animals: cattle was between 18 and 22 months.
- Storage, temperature and transport conditions of ocular tissue: fresh eyes were collected from the slaughterhouse and were transported in HBSS containing Pen/Strep on ice to the laboratories
- Time interval prior to initiating testing: immediately after arrival of the eyes, cornea preparation was initiated and was used for BCOP testing on the same day.

Test system

Vehicle:

physiological saline

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 750 μL of the test item suspension
- Concentration (if solution): 20 % w/v concentration
The test item was mixed with the vehicle to give a 20% w/v concentration using ultrasonic technique. The sonicated suspension was incubated at 50 °C for 10 minutes. Prior to application, the mixture was re-suspended by vortexing and administered directly.

Duration of treatment / exposure:

4 hours ± 5 minutes

Observation period (in vivo):

not applicable

Duration of post- treatment incubation (in vitro):

not required

Number of animals or in vitro replicates:

Number of bovine corneae per dose:
Test item: triplicates
Negative control: triplicates
Positive control: triplicates

Details on study design:

SELECTION AND PREPARATION OF CORNEAS
- eyes were examined for defects and any defective eyes were discarded. Eyes with scratches or any kind of opacity were not used.
- tissue surrounding the eyeball was pulled away and the cornea was excised.
- isolated corneas were stored in a petri dish containing HBSS. Before mounting the corneas in corneal holders (BASF, Duratec GmbH) with the endothelial side against the O-ring of the posterior chamber, they had been visually examined for defects and any defective cornea had been discarded. The anterior chamber was then positioned on top of the cornea and tightened with screws. The chambers of the corneal holder were then filled with pre-warmed RPMI (without phenol red) containing 1 % FBS and 2 mM L-glutamine (complete RPMI).
- corneas were incubated for one hour at 32 ± 1 °C for equilibration in an air incubator.

QUALITY CHECK OF THE ISOLATED CORNEAS
- after the equilibration period, the medium was removed from both chambers and replaced with fresh complete RPMI.
- an initial measurement was performed on each of the corneas using the opacitometer.
- three corneas with illuminance readings approximately equivalent to the median illuminance of all corneas were selected as negative-control corneas.
- the illuminance of each cornea was read and recorded.
- only corneas that had an initial illuminance reading I > I0/1.1651 lux (an equivalent to the opacity threshold of 7 as listed in OECD 437) were used for the assay.

APPLICATION DOSE AND EXPOSURE TIME
- medium was removed from the anterior chamber and replaced with the test item or control.
- 750 μL of the test substance suspension or the control substance was introduced into the anterior chamber (closed-chamber method).
- after 4 hours ± 5 minutes incubation at 32 ± 1 °C either the test substance or the control substance was removed.

REMOVAL OF TEST SUBSTANCE/CONTROL SUBSTANCES
- epithelium was washed at least three times with MEM (containing phenol red).
- once the medium was free of test substance, the cornea was finally rinsed with complete RPMI (without phenol red).

METHODS FOR MEASURED ENDPOINTS:
- anterior chamber was refilled with complete RPMI and an illuminance measurement was performed.
- each cornea was observed visually and pertinent observations were recorded.
- corneas were visually examined for tissue peeling, residual test chemical and non-uniform opacity patterns and observation were recorded.
- after the illuminance measurement was performed, the permeability was measured.
- the medium was removed from both chambers of the holder.
- posterior chamber was refilled with fresh complete RPMI.
- 1 mL of a 5 mg/mL sodium fluorescein solution was added to the anterior chamber and the corneas were incubated for 90 minutes at 32 ± 1 °C.
- then the medium from the posterior chamber was removed and its optical density at 490 nm (OD490) was determined, using a spectrophotometer (Jenway 6405 UV/VIS).

Evaluation of the opacity:
- the following formula was used to calculate the opacity, whereas the values a and b are equipment-specific variables empirically determined by the manufacturer:
Opacity = ((I0/I) - b)/ a
with a = 0.025 and b = 0.9894
- value I0 is the illuminance through a holder without cornea, but with windows and liquid. This value is determined by taking the mean for a set of cornea holders and is reevaluated periodically. This I0 value was than calculated to the respective data of the opacitometer and the data according to guideline (opacity < 7). So the initial illuminance could be calculated and corneas below this value were discarded.
- change in opacity for each cornea (test item, positive and negative control) was calculated by subtracting the initial opacity reading from the final opacity reading. These values of test item treated cornea or positive control were corrected by subtracting from each the average change in opacity observed for the negative-control corneas to obtain the corrected opacity. The mean corrected opacity value for the negtive control and the mean corrected opacity value for the test item and the positive control was calculated by averaging the corrected opacity values of each cornea for a given treatment.

Evaluation of the permeability:
- mean OD490 for the blank cuvettes was calculated.
- mean blank OD490 was subtracted from the OD490 of each cuvette (corrected OD490).
- any dilutions that were made to bring the OD490 values into the linear range of the spectrophotometer (OD490 should be less than 1.500), were taken into account by multiplying the OD490 value of the dilution by the dilution factor.
- final-corrected OD490 of the test article and the positive control were calculated by subtracting the average-corrected OD490 of the negative-control corneas from the corrected OD490 value of each treated cornea:
Final-corrected OD490 = (OD490 – mean blank OD490) – average-corrected negative control OD490
- mean OD490 value of each treatment group was calculated by averaging the final corrected OD490 values of the treated corneas for that treatment condition.

SCORING SYSTEM: In Vitro Irritancy Score (IVIS)
The following formula was used to determine the in vitro irritation score (IVIS):
IVIS = mean opacity value + (15 x mean permeability OD490 value)
To determine the IVIS of the positive control and the test item, the corrected opacity and OD490 values were used.

ACCEPTABILITY CRITERIA
- the BCOP assay is considered to be valid if the in vitro irritation score obtained with the positive control falls within the two standard deviations of the current historical mean.
- the negative control responses should result in opacity and permeability values that are less than the established upper limits for background bovine corneas treated with the respective negative control.

Results and discussion

In vitro

Results

Irritation parameter:

in vitro irritation score

Remarks:

(mean)

Value:

296.98

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

- Visual Observation after treatment:
All 3 corneas treated with strontium bis(2-ethylhexanoate) showed complete opacity of the tissue and exceeded the opacity of the positive control corneas.

- Measurement after treatment:
Relative to the negative control, the test item strontium bis(2-ethylhexanoate) caused an increase of the corneal opacity and permeability compared with the values caused by the negative control.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: the negative control responses resulted in opacity and permeability values that are less than the established upper limits for background bovine corneas treated with the respective negative control.
- Acceptance criteria met for positive control: the in vitro irritation score obtained with the positive control fell within the two standard deviations of the current historical mean and therefore this assay is considered to be valid.

The evaluation of acceptability criteria was performed by using the following historical data:
- for evaluation of the validity of the positive control, the historical mean IVIS score as obtained from 2015 until 2018 and the historical upper limits of the opacity and permeability values as obtained in 2017 and 2018 were used (please refer to the tables in the field "Any other information on results incl. tables")..
- for the evaluation of the validity of the negative control, the historical mean IVIS score as obtained from 2015 until 2018 and the historical upper limits of the opacity and permeability values as obtained in 2017 and 2018 were used (please refer to the tables in the field "Any other information on results incl. tables").

Please also refer for results to the field "Any other information on results incl. tables" below

Any other information on results incl. tables

Table 1: Opacity

Cornea No.	Test Item	Initial Opacity	Final Opacity	Change of Opacity Value	Corrected Opacity Value
1	Negative Control	2.31	3.34	1.03
2		2.20	2.39	0.19
3		2.16	2.80	0.64
MV		2.22	2.84	0.62
4	Positive Control	4.31	99.85	95.54	94.92
5		3.78	87.36	83.58	82.96
6		4.31	95.42	91.11	90.49
MV		4.13	94.21	90.08	89.46
7	Test Item	1.47	227.17	225.70	225.08
8		2.96	221.22	218.26	217.64
9		2.05	241.63	239.57	238.96
MV		2.16	230.00	227.85	227.23

MV = mean value

Table 2: Permeability

Cornea No.	Test Item	OD490	Corrected OD490 Value
1	Negative Control	0.017
2		0.008
3		0.009
MV		0.011
4	Positive Control	1.478	1.467
5		1.500	1.489
6		2.095	2.084
MV		1.691	1.680
7	Test Item	4.310	4.299
8		3.105	3.094
9		6.570	6.559
MV		4.662	4.650

MV = mean value

Table 3: In vitro irritation score

Cornea No.	Test Item	Corrected Opacity	Corrected OD490 Value	IVIS
1	Negative Control	1.03	0.017
2		0.19	0.008
3		0.64	0.009
MV		0.62	0.011	0.79
4	Positive Control	94.92	1.467
5		82.96	1.489
6		90.49	2.084
MV		89.46	1.680	114.65
7	Test Item	225.08	4.299
8		217.64	3.094
9		238.96	6.559
MV		227.23	4.650	296.98

MV = mean value

Table 4: Historical mean in vitro irritation score of the positive control from February 2015 until January 2018

	IVIS Positive Control – Imidazole 20%
Mean Value (MV)	122.57
Standard Deviation (SD)	17.33
MV-2xSD	87.91
MV+2xSD	157.23
Number of Replicates providing Historical Mean: 27

Positive controls are updated after every single experiment or at least every 3 months

Table 5: Historical data on opacity and permeability of the positive control (Imidazole 20 %) from August 2017 until January 2018

	Number of Replicates Providing Historical Mean	Cornea No.	Opacity		Permeability		IVIS
			Change of Opacity Value	Corrected Opacity Value	OD490 Value	Corrected OD490 Value
2017	1	4	122.785	121.861	0.662	0.624	133.420
		5	117.173	116.249	1.220	1.182
		6	102.655	101.731	2.260	2.222
	2	4	108.553	106.381	1.473	1.450	123.050
		5	79.491	77.319	2.465	2.442
		6	83.618	81.446	3.065	3.042
	3	4	55.644	56.308	2.200	2.189	92.540
		5	71.511	72.175	1.348	1.337
		6	65.148	65.812	2.040	2.029
	4	4	68.39	67.72	2.400	2.383	112.690
		5	70.88	70.21	2.810	2.793
		6	94.23	93.56	1.945	1.928
	5	4	70.53	70.35	1.296	1.284	102.440
		5	78.68	78.50	1.363	1.351
		6	91.69	91.51	1.840	1.828
2018	6	4	95.54	94.92	1.478	1.467	114.650
		5	83.58	82.96	1.500	1.489
		6	91.11	90.49	2.095	2.084
	Mean Value (MV)		86.178	85.528	1.859	1.840	113.132
	Standard Deviation (SD)		18.438	18.015	0.617	0.619	14.497
	MV- 2xSD		49.303	49.499	0.624	0.603	84.138
	MV+2xSD		123.053	121.558	3.094	3.078	142.126

Table 6: Historical mean in vitro irritation score of the negative control from February 2015 until January 2018

	IVIS Negative Control - NaCl 0.9 %
Mean Value (MV)	1.11
Standard Deviation (SD)	0.79
MV- 2xSD	-0.47
MV+2xSD	2.70
Number of Replicates providing Historical Mean: 33

Negative controls are updated after every single experiment or at least every 3 months.

Table 7: Historical data on opacity and permeability of the negative control (NaCl 0.9 %) from August 2017 until January 2018

			Incubation: 240 min
	Number of Replicates Providing Historical Mean	Cornae No.	Opacity	Permeability	IVIS
			Change of Opacity Value	OD490 Value
2017	1	1	0.234	0.008	1.49
		2	1.738	0.008
		3	0.800	0.098
	2	1	0.978	0.019	2.52
		2	3.920	0.022
		3	1.617	0.028
	3	1	-0.149	0.009	-0.50
		2	-0.415	0.015
		3	-1.427	0.009
	4	1	0.776	0.008	0.92
		2	0.808	0.022
		3	0.418	0.020
	5	1	0.035	0.010	0.35
		2	0.036	0.013
		3	0.466	0.012
2018	6	1	1.030	0.017	0.79
		2	0.190	0.008
		3	0.640	0.009
	Mean Value (MV)		0.650	0.019	0.928
	Standard Deviation (SD)		1.097	0.021	1.024
	MV- 2xSD		-1.543	-0.023	-1.120
	MV+2xSD		2.843	0.060	2.976

Applicant's summary and conclusion

Interpretation of results:

Category 1 (irreversible effects on the eye) based on GHS criteria

Conclusions:

The test substance is serious eye damaging according to the Regulation (EC) No 1272/2008 and subsequent adaptations (Category 1; H318)