Strontium bis(2-ethylhexanoate)

Endpoint summary

Description of key information

Skin corrosion/irritation: irritating (OECD 435 and OECD 439; GLP)

Eye irritation: causes serious eye damage (OECD 437; GLP)

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-03-26 to 2018-03-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 435 (In Vitro Membrane Barrier Test Method for Skin Corrosion)

Version / remarks:

2015-07-28

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2015-06-05

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

Test system:

artificial membrane barrier model

Source species:

other: not specified

Cell type:

other: synthetic macromolecular bio-barrier

Cell source:

other: not specified

Source strain:

not specified

Details on animal used as source of test system:

not applicable

Justification for test system used:

The CORROSITEX™ Assay is a standardized, quantitative in vitro test for skin corrosivity and has been validated by the ECVAM for testing acids, bases and their derivatives (ECVAM, 2000)*. The bio-barrier membrane is constructed to have physico-chemical properties similar to rat skin.

Reference:
- ECVAM (2000) ESAC statement on the application of the Corrositex® assay for skin corrosivity testing

Vehicle:

unchanged (no vehicle)

Details on test system:

SOURCE AND COMPOSITION OF MEMBRANE BARRIER USED
- Was the Corrositex® test kit used: yes (lot no. CT120516; supplier: Invitro International; Irvine, CA 92614)
- Components: a synthetic macromolecular bio-barrier and a chemical detection system (CDS)
- Apparatus and preparation procedures: the preparation was completed at least 2 hours prior to running tests. The entire content of the BIOBARRIER diluent was added to the vial of BIOBARRIER matrix powder. The vial was heated to 68°C (± 1°C) in a water bath under smooth agitation. After complete dissolution (approx. 20 min.) the solution was allowed to sit for 5 min. to allow any air bubbles to rise to the surface. 200 µL of the BIOBARRIER were pipetted into each membrane disc. The BIOBARRIERS were set on the tray and kept in the cold (2 - 8°C) for at least two hours.

WAS THE COMPATIBILITY TEST PERFORMED: yes
In order to test whether the test system is suitable for the test item, 100 mg of the test substance was added to the Qualify test tube. The vial was shaken to allow dissolution of the test substance and let stand for one minute. If the colour or consistency of the CDS changes at the sample/testing fluid interface, the test material is qualified for the assay. If no reaction is observed within five minutes, the sample is not qualified for the CORROSITEX TM assay.

WAS THE TIMESCALE CATEGORY TEST PERFORMED: yes
This step established the category of cut-off times for the sample. 100 mg of the test substance was added to the tubes labelled Tube A and Tube B. The vial was shaken to allow dissolution of the test substance. In case a colour change was observed in either of the tubes and colour was matched to the corresponding colour charts on the CORROSITEX™ Testing Protocol Poster. Test materials having high acid/alkaline reserves are defined as Category 1 materials, while those with low acid/alkaline reserves are defined as Category 2 materials. If no colour change had been observed in either tube, CONFIRM reagent was added to Tube B. After shaking, the resulting colour was matched to the colour chart on the CORROSITEX™ Testing Protocol Poster. If the test item has a strong inherent colour or shows other characteristics impairing a clear categorization according to the colour chart, the pH value can be measured in tubes A and B and is used to confirm/determine the category of the test item, according to the Corrositex® Reference Manual (1995)*.

TEMPERATURE USED DURING TREATMENT: room temperature (17 - 25 °C)

METHOD OF DETECTION
- Chemical or electrochemical detection system: chemical detection system (CDS)

METHOD OF APPLICATION (CLASSIFICATION TEST):
The CDS vials were warmed to room temperature (17 - 25˚C) before using. Four vials were utilized for test item sample replicate testing. One vial was utilized for a positive control sample and another vial for a negative control. Lastly, one vial served as a CDS colour control. One BIOBARRIER disc was added on top of the first vial (discs were not longer in the vial than two minutes before adding the test samples).
500 mg of the test item was applied evenly on the top of the BIOBARRIER disc and starting time was recorded. This step was repeated for the remaining vials, staggering each start time by e.g. 10 seconds (but not longer than 2 minutes). The start time difference for each vial was subtracted from the final time to determine the net response time. As soon as a reaction had been observed, the time was recorded.

NTERPRETATION OF THE RESULTS:
For Category 1 substances, test chemicals were categorized as non-corrosive in case no colour change occurs after 240 minutes. For Category 2 substances, test chemicals were categorized as non-corrosive in case no colour change occurs after 60 minutes. The start time difference for each vial was subtracted from the final time to determine the net response time.
The time (in minutes) elapsed between application and barrier penetration for the test substance was recorded in tabular form as individual replicate data.
The mean time (± standard deviation) of the four sample replicates to activate the CDS was calculated and reported in tabular form. Using the table as shown in the field "Any other information on materials and methods incl. tables" below, the test item was categorised.

TEST ACCEPTANCE CRITERIA:
The test meets acceptance criteria if:
- test item qualifies in qualification test
- positive control activates CDS > 3 - 60 min.
- negative control activates CDS not before 60 min.
The exact breakthrough time of the positive control should be determined to demonstrate, that the response is in the acceptable historical range of breakthrough times for the positive control (mean ± 2 - 3 standard deviations).

*Reference:
- InVitro International (1995), Corrositex® Reference Manual

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 500 mg of the test item

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 500 µL of citric acid (10%) in aqua dest.

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 500 µL of phosphoric acid (85 %)

Duration of treatment / exposure:

60 minutes

Duration of post-treatment incubation (if applicable):

not applicable

Number of replicates:

Test item: quadruplicates
Negative control: single measurement
Positive control: single measurement

Irritation / corrosion parameter:

penetration time (in minutes)

Value:

0

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Colour change or structural change was not observed up to 60 minutes (treatment period)

Other effects / acceptance of results:

QUALIFICATION TEST:
The test substance was compatible with the CORROSITEX™ Assay, as assessed in the qualification step. The categorization step and the classification step could be performed.

CATEGORIZATION TEST:
A direct colour change was not observed. CONFIRM reagent was added to tube B and the category was read from the CORROSITEX™ colour chart. The chemical has been categorized to category 2.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: negative control did not activate the CDS before 60 minutes (> 60 minutes).
- Acceptance criteria met for positive control: positive control activated the CDS between 3 - 60 minutes (26.04 min).

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

Table1:  Results of the test item strontium bis(2 -ethylhexanoate)

	CORROSITEX™ Time [min]	Colour Change	Consistency Change
Replicate 1	> 60	no	no
Replicate 2	> 60	no	no
Replicate 3	> 60	no	no
Replicate 4	> 60	no	no
Mean ± SD	> 60
Positive control	26.04	yes	no
Negative control	> 60	no	no

The mean time, required to activate the CDS was> 60min.

Interpretation of results:

GHS criteria not met

Conclusions:

The test item, strontium bis(2 -ethylhexanoate), is not corrosive to the skin.
According to the Regulation (EC) No 1272/2008 and subsequent regulations, the test item is not corrosive to the skin.

Reference 2

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-01-24 to 2018-01-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2015-07-28

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: MatTek Corporation Protocol for: In Vitro EpiDermTM Skin Irritation Test (EPI-200-SIT) For use with MatTek Corporation’s Reconstructed Human Epidermal Model EpiDerm (EPI-200-SIT)

Version / remarks:

2014-11-07

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2015-06-05

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

Test system:

human skin model

Source species:

human

Cell type:

other: normal, human epidermal keratinocytes

Cell source:

other: humans

Source strain:

other: not applicable

Details on animal used as source of test system:

not applicable

Justification for test system used:

This test uses the EpiDerm™ reconstructed human epidermis model (MatTek) which consists of normal human-derived epidermal keratinocytes (NHEK) and therefore represents in vitro the target organ of the species of interest and closely resembles the biochemical and physiological properties of the upper parts of the human skin, i.e. the epidermis.

Vehicle:

other: Dulbecco's phosphate buffered saline

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDermTM (EPI-200-SIT; MatTek)
- Tissue lot number: 25875

TEST FOR DIRECT MTT REDUCTION
- to check the non-specific MTT-reducing capability of the test item 25 mg of the test item were mixed per 1 mL MTT medium and incubated for 60 min at 37 ± 1 °C in the incubator (5 % CO2, 95 % RH).
- untreated MTT medium was used as control.
- if the mixture turns blue/purple, the test item is presumed to have reduced MTT and the part of absorption due to the non-specific reduction of MTT (NSMTT) was determined by using freeze-killed tissues.

TEST FOR COLOUR INTERFERENCE
- to check the colouring potential of the test item 25 mg of the test item were mixed per 300 µL aqua dest. and per 300 µL isopropanol each in a transparent recipient and incubated at 37 ± 1°C for 60 min (5 % CO2, 95 % RH).
- the mixture showed no colouring detected by unaided eye assessment. So the additional functional test with viable tissues and the quantitative corrections were not necessary.

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 ± 1 °C for 35 ± 1 minutes followed by incubation at room temperature until the 60 ± 1 minute treatment period was completed
- Temperature of post-treatment incubation: 37 ± 1 °C

REMOVAL OF TEST MATERIAL AND CONTROLS
- after the end of the treatment period the tissues were washed 15 times with DPBS.
- subsequently, the inserts were submerged three times in DPBS and shaken to remove rests of the test item.
- then inserts were rinsed once from the inside and the outside with sterile DPBS.
- inserts were placed in prepared 6-well plates containing pre-warmed fresh assay medium per well.
- plates were post-incubated at 37 ± 1 °C, 5.0% CO2, humidified to 95%, for 24 ± 2 h. Following this incubation the tissues were transferred to new wells containing fresh assay medium and incubated for additional 18 ± 2 h.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1 mg/mL (300 µL/well)
- Incubation time: 3 hours ± 5 minutes
- Extraction of formazan: after the MTT incubation period, the tissues were rinsed three times with DPBS and allowed to dry. The tissues were transferred into 12-well plates and immersed in 2 mL isopropanol, sealed to inhibit evaporation. Extraction was carried out protected from light at room temperature at least for 2 hours with shaking on a plate shaker.
Before using the extracts, the plate had been shaken for at least 15 minutes on a plate shaker and the inserts were pierced with an injection needle. The extract was pipetted up and down 3 times before 2 x 200 µL aliquots per each tissue were transferred into a 96-well plate. Optical density (OD) was measured with a filter band without reference wavelength in a plate spectrophotometer using isopropanol as a blank.
- Wavelength: 570 nm
- Filter bandwidth: maximum ± 30 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: tissues pass analysis for tissue viability
- Barrier function: tissues pass analysis for tissue functionality
- Morphology: presence of a functional stratum corneum, a viable basal cell layer, and intermediate spinous and granular layers.
- Contamination: absence of bacteria, yeast, and other fungi (long term antibiotic, antimycotic free culture) as well as absence of HIV1-virus, Hepatitis B virus and Hepatitis C virus
Please also refer to the field "Attached background material" below.

PREDICTION MODEL / DECISION CRITERIA
The mean optical density (OD) of the three negative control tissues was calculated after blank correction. This value corresponded to 100 % tissue viability in the current test. For each individual tissue treated with the test item or the positive control, the individual relative tissue viability is calculated according to the following formula:
Relative viability (%) = [(mean ODtest item / positive control) / ODmean of negative control] * 100
For the test item and the positive control the mean relative viability ± relative standard deviation of the three individual tissues were calculated and used for classification according to the following prediction model:
Irritant potential of the test item was predicted from the relative mean tissue viabilities compared to the negative control tissues concurrently treated with DPBS. The test item is considered to be irritant to skin in accordance with regulation EC 1272/2008 (UN GHS “Category 2”), if the tissue viability after exposure and post-incubation is less or equal to 50%. Further testing is required to resolve between UN GHS categories 1 and 2 and decide on the final classification of the test substance. The test substance may be considered as non-irritant to skin in accordance with regulation EC 1272/2008 and UN GHS “No Category” if the tissue viability after exposure and post-treatment incubation is more than 50%.

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 (39 mg/cm²) of the test item
Firstly, 25 µL of the vehicle were applied to the epidermal surface in order to improve the contact between the powder and the epidermis. Afterwards, 25 mg (39 mg/cm²) of the test item were applied directly atop the EpiDermTM tissue using an application spoon avoiding compression of the test item. The test item was spread to match size of the tissue by using a bulb-headed Pasteur pipette.

VEHICLE
- Amount(s) applied (volume or weight with unit): 25 µL of the vehicle

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL DPBS

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL of 5 % SDS solution

Duration of treatment / exposure:

60 ± 1 minute

Duration of post-treatment incubation (if applicable):

approx. 42 hours

Number of replicates:

triplicates

Irritation / corrosion parameter:

% tissue viability

Remarks:

(mean)

Value:

4.2

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

- OTHER EFFECTS:
- Direct-MTT reduction: The mixture of 25 mg test item per 1 mL MTT medium showed no reduction of MTT compared to the solvent. The mixture did not turn blue/purple. Therefore, NSMTT equalled 0%.
- Colour interference with MTT: The mixture of 25 mg of the test item per 300 μl aqua dest. and per 300 μL isopropanol showed no colouring detectable by unaided eye-assessment. Therefore, NSC equalled 0%.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: mean absolute OD570 of the three negative control tissues was ≥ 0.8 and ≤ 2.8 (value: 1.845).
- Acceptance criteria met for positive control: mean relative tissue viability (% negative control) of the positive control was ≤ 20% (4.1 %)
- Acceptance criteria met for variability between replicate measurements: standard deviation of viability of replicate tissues of all dose groups was ≤ 18% (0.6 % - 5.5 %).
- The absorbance values were not below historically established boundaries.

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

Table1:  Result of the test item strontium bis(2-ethylhexanoate)

Name	Negative Control			Positive Control			Test Item
Tissue	1	2	3	1	2	3	1	2	3
Absolute OD570	1.717	1.912	1.872	0.106	0.124	0.125	0.130	0.114	0.109
	1.743	1.895	1.929	0.107	0.125	0.124	0.135	0.116	0.111
Mean Absolute OD570	1.845****			0.119			0.119
OD570(Blank Corrected)	1.673	1.868	1.828	0.062	0.080	0.081	0.086	0.071	0.065
	1.699	1.851	1.885	0.063	0.081	0.081	0.091	0.072	0.068
Mean OD570of the Duplicates (Blank Corrected)	1.686	1.860	1.857	0.063	0.081	0.081	0.088	0.071	0.067
Total Mean OD570of 3 Replicate Tissues (Blank Corrected)	1.801*			0.075			0.075
SD of Mean OD570of the Replicates (Blank Corrected)	0.099			0.010			0.011
Relative Tissue Viability [%]	93.6	103.3	103.1	3.5	4.5	4.5	4.9	4.0	3.7
Mean Relative Tissue Viability [%]	100.0			4.1**			4.2
SD of Relative Tissue Viability [%]	5.5***			0.6***			0.6***
CV [% Viabilities]	5.5			13.9			15.1

^* Blank-corrected mean OD_{570 nm}of the negative control corresponds to 100% absolute tissue viability.

^** Mean relative tissue viability of the three positive control tissues is ≤ 20%.

^*** Standard deviation (SD)of relative tissue viabilityobtained from the three concurrently tested tissuesfor test item, positive and negative controlis≤ 18%

****Mean absolute OD₅₇₀of the negative control tissues is ≥0.8 and ≤2.8.

Table2:  Historical data

	Mean Absolute OD570±30nmNC	MeanAbsoluteOD570±30nmPC	Mean Relative Viability [%] PC	SD Viability [%] NC, PC, TI
Mean	1.861	0.114	3.7	4.4
SD	0.247	0.033	1.5	4.1
Range of LCL – UCL	1.367 – 2.355	0.048 – 0.181	0.7 – 6.8	0.0 – 12.5
n	25	25	25	117

LCL:      Lower control limit (95%, mean – 2*SD)

UCL:      Upper control limit (95%, mean + 2*SD)

n:            number of control values

Historical data were generated in 2017.

Interpretation of results:

other: Category 1 (corrosive) or Category 2 (irritant) based on GHS criteria

Conclusions:

The test item, strontium bis(2-ethylhexanoate), is either corrosive or irritating to the skin. Since the RhE test methods covered by OECD TG 439 cannot resolve between UN GHS Categories 1 or 2, further information on skin corrosion is required to decide on its final classification.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Link to relevant study records

Reference

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

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

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.

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.

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.

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

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

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)

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irreversible damage)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin corrosion/irritation:

The substance was observed to be either corrosive or irritating to the skin in a reliable in vitro skin irritation/corrosion study according to OECD 439. As the results of an OECD 439 test are not suitable to differentiate between skin categories 1 and 2, the substance was tested in an in vitro skin corrosion test.

Strontium bis(2 -ethylhexanoate) was tested in an in vitro skin corrosion test according to OECD 435 and the substance was not observed to be corrosive to the skin.

Eye irritation:

The substance was observed to be serious eye damaging to the eyes in a reliable in vitro eye irritation study according to OECD 437.

Justification for classification or non-classification

Skin irritation:

Strontium bis(2-ethylhexanoate) does possess a skin irritation potential based on in vitro OECD 435 and 439 studies. The substance does require classification as skin irritant according to Regulation (EC) No 1272/2008 and its subsequent adaptations (Category 2; H315).

Eye irritation

The substance does possess a serious eye damaging potential based on an in vitro OECD 437 test and does require classification as serious eye damaging according to Regulation (EC) No 1272/2008 and its subsequent adaptations (Category 1; H318).