Hexyltrimethoxysilane

Endpoint summary

Description of key information

Skin irrtation: OECD TG 439: EpiDerm: not irritating; EpiSkin: irritating

similar to OECD 404: irritating (read across from CAS 1067 -25 -0 and CAS 3069 -40 -7)

Eye irritation: OECD TG 437: non-corrosive

OECD TG 405: not irritating (read across from CAS 1067 -25 -0 and CAS 3069 -40 -7)

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

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:

28 July 2015

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

06-Jul-2012

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: human donors

Source strain:

not specified

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: reconstituted three-dimensional human skin model EpiDerm (MatTek)
- Tissue batch number(s): 25885

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 ± 1°C
- Temperature of post-treatment incubation (if applicable): 37 ± 1°C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: tissues were washed by filling and emptying the inserts 15 times with Dulbecco’s phosphate buffered saline (DPBS) using a constant stream in about 1.5 cm distance from the tissue surface, staggered again in e.g. one-minute intervals.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: MTT stock solution (i.e., 5 mg/mL MTT in PBS) diluted 1 + 4 with Dulbecco’s Modified Eagle Medium (DMEM)-based medium (final concentration 1 mg/mL)
- Incubation time: 3 h ± 5 min
- Spectrophotometer: Yes, plate spectrophotometer
- Wavelength: 570 nm
- Filter: Yes
- Filter bandwidth: ± 30 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: 1.52 ± 0.086
- Barrier function: 7.27 h

NUMBER OF REPLICATE TISSUES: 3

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
The irritant potential was predicted from the relative mean tissue viabilities compared to the negative control. If the mean relative tissue viability is > 50% the test material is not considered an irritant. If the mean relative tissue viability is ≤ 50%, the test material is considered an irritant.

The test meets acceptance criteria if:
- mean absolute OD570 of the three negative control tissues is ≥ 0.8 and ≤ 2.8
- mean relative tissue viability of the three positive control tissues is ± 20%
- standard deviation (SD) of relative tissue viability obtained from each three concurrently tested tissues is ≤ 18%.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied: 30 µL (undiluted)

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

POSITIVE CONTROL
- Amount(s) applied: 30 µL SDS
- Concentration: 5%

Duration of treatment / exposure:

60 min

Duration of post-treatment incubation (if applicable):

42 h

Number of replicates:

3

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

mean out of 3 replicates

Value:

102.3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

- OTHER EFFECTS:
- Direct-MTT reduction: The mixture of 30 µL test item per 1 mL MTT medium showed no reduction of MTT compared to the solvent.
- Colour interference with MTT: The mixture did not turn blue/purple.

DEMONSTRATION OF TECHNICAL PROFICIENCY: The controls confirmed the validity of the study. The mean absolute OD570 of the three negative control tissues was ≥ 0.8 and ≤ 2.8 (2.002). The mean relative tissue viability (% negative control) of the positive control was ≥ 20% (3.0%). Standard deviation of viability of replicate tissues of all dose groups was ≤ 18% (0.1% - 9.8%).

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes
- Acceptance criteria met for positive control: yes
- Acceptance criteria met for variability between replicate measurements: yes

Table 1:  Result of the Test Item Hexyltrimethoxysilane

Name	Negative Control			Positive Control			Test Item
Tissue	1	2	3	1	2	3	1	2	3
Absolute OD570	2.070	1.785	2.187	0.100	0.101	0.100	2.000	2.062	2.028
	2.045	1.789	2.133	0.103	0.107	0.100	2.061	2.072	2.056
OD570(Blank Corrected)	2.027	1.741	2.144	0.057	0.057	0.056	1.957	2.018	1.985
	2.002	1.746	2.090	0.060	0.063	0.057	2.017	2.029	2.012
Mean OD570of the Duplicates (Blank Corrected)	2.014	1.743	2.117	0.058	0.060	0.056	1.987	2.023	1.998
Total Mean OD570of 3 Replicate Tissues (Blank Corrected)	1.958*			0.058			2.003
SD OD570	0.193			0.002			0.019
Relative Tissue Viability [%]	102.9	89.0	108.1	3.0	3.1	2.9	101.5	103.3	102.1
Mean Relative Tissue Viability [%]	100.0			3.0**			102.3
SD Tissue Viability [%]***	9.8			0.1			1.0
CV [% Viabilities]	9.8			3.2			0.9

 ^*                      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) obtained from the three concurrently tested tissues is≤ 18%

Interpretation of results:

other: CLP/EU GHS criteria are not met, no classification required according to Regulations (EC) No 1272/2008.

Conclusions:

In this in vitro skin irritation study conducted in accordance with OECD 439 and in compliance with GLP, the test item showed no irritant effects.

Reference 2

Endpoint:

skin irritation: in vivo

Type of information:

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

Remarks:

Summary of available data used for the endpoint assessment of the target substance

Adequacy of study:

weight of evidence

Justification for type of information:

refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Irritation parameter:

erythema score

Basis:

animal #1

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 8 days

Remarks on result:

other: Scaling to the end of the observation period

Irritation parameter:

erythema score

Basis:

animal #2

Time point:

24/48/72 h

Score:

1.67

Max. score:

4

Reversibility:

fully reversible within: 8 days

Remarks on result:

other: Scaling to the end of the observation period

Irritation parameter:

erythema score

Basis:

animal #3

Time point:

24/48/72 h

Score:

1.67

Max. score:

4

Reversibility:

fully reversible within: 8 days

Remarks on result:

other: Scaling to the end of the observation period

Irritation parameter:

edema score

Basis:

animal #1

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 8 days

Irritation parameter:

edema score

Basis:

animal #2

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 8 days

Irritation parameter:

edema score

Basis:

animal #3

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 8 days

Irritant / corrosive response data:

Clear defined erythema and slight edema in all three animals. Scaling to the end of the observation period (14 days).

The key result found with the source substance trimethoxypropylsilane (CAS 1067 -25 -0) indicate that the source substance is irritating to the skin.

Similar results were also found for the second source substance trimethoxy(octyl)silane (CAS 3069-40-7) which was also found to be irritating to the skin of rabbits.

Mean erythema scores (24/48/72 h) for the three rabbits were 3, 2.3, and 3, respectilvely. The erythema was resolved by Day 10 after treatment. Mean edema scores (24/48/72h) for the three rabbits were 3, 2, and 3, respectively. The edema fully reversed after 9 days.

Interpretation of results:

other: Category 2 based on CLP criteria (EU criteria according to Regulation (EC) No. 1272/2008)

Conclusions:

Reliable skin irritation studies, conducted according to OECD 405 but not GLP, indicate that the source substances CAS 1067-25-0 and CAS 3069-40-7 are irritating to the skin of rabbits. As explained in the analogue justification, it is considered that the target and the source substances are unlikely to lead to differences in skin irritation potential.

Reference 3

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

June 20 - August 10 2018

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:

28 July 2015

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP-Landesleitstelle Bayern, Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, Rathausgasse 4, 91126 Schwabach, Germany

Test system:

human skin model

Remarks:

EPISKIN-SM™ reconstructed human epidermis model (SkinEthic)

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: human donors

Source strain:

not specified

Justification for test system used:

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

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used:EPISKIN-SM™ reconstructed human epidermis model (SkinEthic)
- Tissue batch number(s): 18-EKIN-032

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 ± 1°C
- Temperature of post-treatment incubation: 37 ± 1°C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: tissues were washed with Dulbecco’s phosphate buffered saline (DPBS)

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: MTT stock solution diluted 1 + 9 with Dulbecco’s Modified Eagle Medium (DMEM)-based medium (final concentration 0.3 mg/mL)
- Incubation time: 3 h
- Spectrophotometer: Yes, plate spectrophotometer
- Wavelength: 570 nm
- Filter: Yes
- Filter bandwidth: ± 30 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Barrier function: 2.2 mg/mL
- Morphology: Well-differentiated epidermis consisting of a basal layer, several spinous and granular layers and a thick stratum corneum.

NUMBER OF REPLICATE TISSUES: triplicate

PREDICTION MODEL / DECISION CRITERIA
The irritant potential was predicted from the relative mean tissue viabilities compared to the negative control. If the mean relative tissue viability is > 50% the test material is not considered an irritant. If the mean relative tissue viability is ≤ 50%, the test material is considered an irritant.

The test meets acceptance criteria if:
- mean OD570 nm of the blank is < 0.1
- mean absolute OD570 nm of the three negative control tissues is ≥ 0.6 and ≤ 1.5
- mean relative tissue viability of the three positive control tissues is ≤ 40%
- standard deviation (SD) of relative tissue viability obtained from each three concurrently tested tissues is ≤ 18%.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit):10 μL
- Concentration: undiluted

NEGATIVE CONTROL
- Amount(s) applied (volume or weight):10 μL
- Concentration: undiluted

POSITIVE CONTROL
- Amount(s) applied (volume or weight):10 μL
- Concentration: 5% SDS solution

Duration of treatment / exposure:

15 min

Duration of post-treatment incubation (if applicable):

42 hr

Number of replicates:

3

Irritation / corrosion parameter:

% tissue viability

Value:

27.2

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: The test item showed no visible damage on the test system.
- Direct-MTT reduction: The mixture of 10 μl test item per 2 mL MTT medium showed no reduction of MTT as compared to the solvent. The mixture did not turnblue/purple. Therefore, NSMTT (non-specific reduction of MTT) equalled 0%.
- Colour interference with MTT: No

DEMONSTRATION OF TECHNICAL PROFICIENCY:
The test item showed irritative effects. All test acceptance criteria were met. The OD570 of the blank sample was 0.044, meeting the acceptance criteria. Positive and negative controls responded appropriately. The maximum inter-tissue viability difference of replicate tissues fell within the acceptance criteria. Positive and negative controls responded appropriately. The maximum inter-tissue viability difference of replicate tissues fell within the acceptance criteria.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: The mean absolute OD570 of the three negative control tissues was ≥ 0.6 and ≤ 1.5 (0.774), meeting the acceptance criteria for a negative control.
- Acceptance criteria met for positive control: The mean relative tissue viability of the positive control was ≤ 40% (5.2%), meeting the acceptance criteria for a positive control.
- Acceptance criteria met for variability between replicate measurements: The standard deviation of viability of replicate tissues of all dose groups was ≤ 18% (4.3%), meeting the acceptance criteria.

Interpretation of results:

other: Category 2 based on CLP criteria (EU criteria according to Regulation (EC) No. 1272/2008)

Conclusions:

In an in vitro skin irritation human skin model test (EpiSkin) according to OECD guideline 439 and in compliance with GLP, a cell viability of 27.2% was measured when compared to the untreated control. Therefore, the test item should be classified as an irritant (Cat. 2, H315).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Link to relevant study records

Reference

Reference 1

Endpoint:

eye irritation: in vivo

Type of information:

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

Remarks:

Summary of available data used for the endpoint assessment of the target substance

Adequacy of study:

weight of evidence

Justification for type of information:

refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Irritation parameter:

cornea opacity score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility not applicable

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

cornea opacity score

Basis:

animal #2

Time point:

24/48/72 h

Score:

1

Max. score:

4

Reversibility:

fully reversible within: 6 days

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

cornea opacity score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility not applicable

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

iris score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

2

Reversibility:

other: reversibility not applicable

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

iris score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0.33

Max. score:

2

Reversibility:

fully reversible within: 48 h

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

iris score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

2

Reversibility:

other: reversibility not applicable

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

conjunctivae score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0.33

Max. score:

3

Reversibility:

fully reversible within: 48 h

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

conjunctivae score

Basis:

animal #2

Time point:

24/48/72 h

Score:

2.67

Max. score:

3

Reversibility:

fully reversible within: 6 days

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

conjunctivae score

Basis:

animal #3

Time point:

24/48/72 h

Score:

1.67

Max. score:

3

Reversibility:

fully reversible within: 6 days

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

chemosis score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility not applicable

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

chemosis score

Basis:

animal #2

Time point:

24/48/72 h

Score:

1

Max. score:

4

Reversibility:

fully reversible within: 72 h

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

Irritation parameter:

chemosis score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility not applicable

Remarks on result:

other:

Remarks:

CAS 1067-25-0, Toxikologie Degussa-Asta, 1987

The key result found with the source substance trimethoxypropylsilane (CAS 1067 -25 -0) indicate that the source substance is not irritating to the eyes. This result is supported by an older study which is used as supporting study (INBIFO, 1979) where also no eye irritating potential was found. The mean cornea opacity and iris score out of 6 animals (24/48/72h) were found to be 0. The mean conjunctivae score of 0.8 (24/48/72 h) was found to be reversible within 7 days and the mean chemosis score of 0.2 (24/48/72h) was fully reversible within 72 hours.

Furthermore, similar results were also found for the second source substance trimethoxy(octyl)silane (CAS 3069-40-7) which was also found to be not irritating to the eye of rabbits.

Corneal opacity score, iris score and chemosis score were 0 at 24h, 48, and 72 hours after treatment. Conjunctival redness was observed in all three animals with a mean score after 24/48/72 hours of 0.3, 0.3 and 1.3 for each animal. Conjuntival redness was completely resolved after 72 hours.

Interpretation of results:

other: CLP/EU GHS criteria are not met, no classification required according to Regulations (EC) No 1272/2008.

Conclusions:

Reliable eye irritation studies, conducted according to OECD 405 but not GLP, indicate that the source substances CAS 1067-25-0 and CAS 3069-40-7 were not irritating to the eyes of rabbits. As explained in the analogue justification, it is considered that the target and the source substances are unlikely to lead to differences in eye irritation potential.

Reference 2

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

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 Ocular Corrosives and Severe Irritants)

Version / remarks:

09 October 2017

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit

Species:

cattle

Strain:

not specified

Details on test animals or tissues and environmental conditions:

SOURCE OF COLLECTED EYES
- Source: A. Moksel AG, Buchloe, Germany
- Source: obtained from a slaughterhouse
- Storage, temperature and transport conditions of ocular tissue (e.g. transport time, transport media and temperature, and other conditions): On the test day, 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.

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 750 µL

Duration of treatment / exposure:

10 minutes

Duration of post- treatment incubation (in vitro):

2 hours

Number of animals or in vitro replicates:

3 corneas for the test item
3 corneas as negative controls treated with physiological saline 0.9% NaCl
3 corneas as positive controls treated with ethanol 100%

Details on study design:

SELECTION AND PREPARATION OF CORNEAS
The eyes were carefully examined for defects and any defective eyes were discarded.

The tissue surrounding the eyeball was carefully pulled away and the cornea was excised leaving a 2 to 3 mm rim of sclera. The isolated corneas were stored in a petri dish containing HBSS. Before the corneas were mounted in corneal holders 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 RPMI (without phenol red) containing 1% FBS and 2 mM L-glutamine (complete RPMI). The posterior chamber was always filled first. The corneas were incubated for one hour at 32 ± 1 °C.

NUMBER OF REPLICATES
3

NEGATIVE CONTROL USED
yes; 750 µL physiological saline 0.9% NaCl

POSITIVE CONTROL USED
yes; 750 µL ethanol 100%

APPLICATION DOSE AND EXPOSURE TIME
750 µL test material for 10 minutes

POST-INCUBATION PERIOD: no

REMOVAL OF TEST SUBSTANCE
- Number of washing steps after exposure period: After 10 minutes incubation at 32 ± 1 °C either the test substance or the control substance was removed and the epithelium 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).
- POST-EXPOSURE INCUBATION: 2 hours incubation at 32 ± 1 °C

METHODS FOR MEASURED ENDPOINTS:
- Corneal opacity: The change in opacity for each cornea was calculated by subtracting the initial opacity reading from the final opacity reading. These values were corrected by subtracting from each the average change in opacity observed for the negative-control corneas. The mean opacity value for each treatment was calculated by averaging the corrected opacity values of each cornea for a given treatment.
- Corneal permeability: The mean OD490 for the blank cuvettes was calculated. The 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. The 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
The 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: The following formula was used to determine the in vitro irritation score (IVIS): IVIS = mean opacity value + (15 x mean permeability OD490 value)

DECISION 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 following criteria was used for the BCOP Assay: ≤ 3 = not classified for eye irritation; > 3 ≤ 55: no prediction can be made; and > 55: inducing serious eye damage. When no prediction for inducing serious eye damage can be made further testing with another suitable method is required.

Irritation parameter:

in vitro irritation score

Value:

3.35

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

OTHER EFFECTS:
- Visible damage on test system: All 3 corneas treated with hexyl(trimethoxy)silane showed no opacity of the tissue

DEMONSTRATION OF TECHNICAL PROFICIENCY: yes

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes; 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: yes; 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.

Interpretation of results:

other: non-corrosive (Eye Irrit. 2 or not classified according to Regulation (EC) No 1272/2008)

Conclusions:

Under the conditions of the test, the test substance was shown to have no corrosive potential in the bovine corneal opacity and permeability (BCOP) test prediction model. No prediction can be made regarding the classification of the test substance hexyl(trimethoxy)silane according to the evaluation criteria. Mean in vitro irritation score of 3.35. Further testing in another suitable method is required.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation:

A reliable in vitro skin irritation study with the test substance CAS 3069 -19 -0 is available according to OECD TG 439 and GLP (Eurofins, 2018). The EpiDerm™-Standard Model (EPI-200™), a reconstituted three-dimensional human epidermis model, was used in oder to evaluate the skin irritation potential of hexyltrimethoxysilane. Hereby, the test item was applied topically. No cytoxocity was observed. The test item showed no irritant effects. The mean relative tissue viability (% negative control) was > 50% (102.3%) after 60 min treatment and 42 h post-incubation.

A second reliable in vitro skin irritation study with test substance CAS 3069 -19 -0 is available according to OECD TG 439 and GLP (Eurofins, 2019). The EpiSkin™ (SkinEthic) a reconstituted three-dimensional human epidermis model, was used in order to evaluate the skin irritation potential of hexyltrimethoxysilane. Hereby, the test item was applied topically. No cytoxocity was observed. The test item showed irritant effects. The mean relative tissue viability (% negative control) was < 50% (27.2%) after 15 min treatment and 42 h post-incubation.

Because of these contradicting results the skin irritation potential was further investigated based on the available data from the source substance trimethoxy(propyl)silane (CAS 1067-25-0) and trimethoxy(octyl)silane (CAS 3069 -40 -7). In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and following the Read across assessment framework (RAAF, ECHA 2017) read across from an analogue substance has been applied to support the human health hazard assessment of hexyl(trimethoxy)silane (CAS 3069-19-0).

 

In the skin irritation study according to OECD TG 404 but not to GLP trimethoxy(propyl)silane (CAS 1067 -25 -0) was irritating to the skin of rabbits under occluded conditions. Erythema or edema were seen for up to 8 days with a mean erythema scores of 2, 1.67 and 1.67 or mean edema scores of 2, 2, 2 for the three animals, respectively, at the reading time point 24/48/72 hours. Scaling continued to study termination at 14 days (limited information appears to be presented on observations post-72h) (ASTA-WERKE, 1987).

 

In the skin irritation study conducted to OECD 404 but not to GLP (ASTA Pharma AG, 1987a) trimethoxy(octyl)silane was irritating to the skin of rabbits under occluded conditions. Erythema occurred in all three animals immediately after removal of the patches. The erythema was moderate to severe, but had disappeared by day 10 of observation (mean score of 3, 2.3 and 3 for the three animals, respectively). Edema also occurred immediately after the end of exposure; slight in one animal and moderate in two animals (mean score of 3, 2 and 3 for the three animals, respectively). The findings had disappeared by day 9. From the middle of the first observation week all animals showed eschar formation, which had not completely peeled off in two animals until the end of the observation period.

In conclusion, in a weight of evidence approach the registered substance hexyl(trimehtoxy)silane is considered to be a skin irritant.

 

Eye Irritation:

An in vitro eye irritation study on hexyl(trimethoxy)silane (CAS 3069-19-0) is available; however, results from this study are not sufficient to allow for classification as irritant. Therefore, the hazard assessment for eye irritation of the registered substance was performed based on the available data from the source substance trimethoxy(propyl)silane (CAS 1067-25-0) and trimethoxy(octyl)silane (CAS 3069 -40 -7). In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and following the Read across assessment framework (RAAF, ECHA 2017) read across from an analogue substance has been applied to support the human health hazard assessment of hexyl(trimethoxy)silane (CAS 3069-19-0).

 

The eye irritancy potential of hexyl(trimethoxy)silane was investigated in the bovine corneal opacity and permeability assay according to OECD 437 and in compliance with GLP (Eurofins, 2018). All 3 corneas treated with hexyl(trimethoxy)silane showed no opacity of the tissue and the mean in vitro irritation score was calculated to be 3.35. Based on this result, the test substance is considered to be not seriously eye damaging according to the evaluation criteria. However, no prediction can be made regarding the non-classification or classification as irritant to eyes. Therefore, read across data from similar substances as trimethoxy(propyl)silane and trimethoxy(octyl)silane are considered.

In the key eye irritation study with the source substance CAS 1067-25-0 according to OECD TG 405 redness of the conjunctivae was the most prominent effect of the test substance. It was seen in all three animals to a varying degree (score: 0.33 - 2.67, mean over 24, 48 and 72 h). Nevertheless, the scores in the report indicate that the test material is not classified irritating to the eyes of rabbits. All effects were reversible within six days of treatment (Toxikologie Degussa-Asta, 1987). The second study supported the findings of the key study (INBIFO, 1979).

In the key eye irritation study conducted to OECD 405 but not to GLP (ASTA Pharma AG, 1987b) trimethoxyoctylsilane was not irritating to the eyes of rabbits. Cornea and iris did not show any findings. The conjunctiva reacted with hyperemia (grade 1) in one animal and in two animals diffuse crimson or beefy discolouration (grade 2 or 3) was observed. In addition, slight swelling (grade 1) or swelling with partial eversion of lids (grade 2) occurred. Swelling had completely disappeared at 24 hours and redness 48 or 96 hours after substance treatment. Nevertheless the scores in the report indicate that the test material is not classified irritating to the eyes of rabbits.

 

In conclusion, no eye irritation potential is also considered for the target substance CAS 3069 -19 -0.

Justification for classification or non-classification

Reliable data from the registered substance on skin irritation and structural analogues on skin irritation indicates that the registered substance meets the criteria for classification according to Regulation (EC) No. 1272/2008, and is therefore classified as skin irritant Category 2 (H315).

Reliable data from the registered substance on eye irritation and structural analogues on eye irritation indicates that the registered substance does not meet the criteria for classification according to Regulation (EC) No. 1272/2008, and the available data are therefore conclusive but not sufficient for classification.