Dimethoxydimethylsilane

Endpoint summary

Description of key information

Skin irritation (OECD 439 EPISKIN and EpiDerm): not irritating

Eye irritation (OECD 437): non-corrosive

Eye irritation (WoE in vivo studies according or similar to OECD 405): not irritating (RA CAS 1185-55-3 and RA CAS 2031-67-6)

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:

key study

Study period:

15 - 22 Nov 2021

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:

June 2021

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

September 2019

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: EPISKIN Small model (EPISKIN-SM™)

Justification for test system used:

In the interest of sound science and animal welfare, a sequential testing strategy is recommended to minimize the need of in vivo testing. One of the validated in vitro skin irritation tests is the EPISKIN test, which is recommended in international guidelines (e.g. OECD and EC).

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN Small Model™ (SkinEthic Laboratories, Lyon, France)
- Tissue batch number: 21-EKIN-046
- Production date: 16 Nov 2021
- Date of initiation of testing: on the day of tissue receipt

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: at room temperature
- Temperature of post-treatment incubation: 37.0 ± 1.0°C (actual range 36.4 - 36.9°C)

REMOVAL OF TEST MATERIAL AND CONTROLS
- Volume and number of washing steps: The tissues were washed with phosphate buffered saline to remove residual test item. After rinsing, the cell culture inserts were each dried carefully and moved to a new well on 2 mL pre-warmed maintenance medium until all tissues were dosed and rinsed.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/mL in PBS
- Incubation time: 3 h ± 5 min at 37°C
- Spectrophotometer: TECAN Infinite® M200 Pro Plate Reader
- Wavelength: 570 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Barrier function: The IC50 determined by MTT test after incubation with SDS was 1.8 mg/mL (acceptance criteria: 1.5 mg/L ≤ IC50 ≤ 3.0 mg/L).
- Morphology: Multi-layered, highly differentiated epidermis consisting of organized basal, spinous and granular layers, and a multilayered stratum corneum. The number of cell layers was 8.
- Contamination: On cells from the donors, the absence of bacteria, fungus and mycoplasma was verified. On blood of the donors, the absence of HIV1 and 2 antibodies, hepatitis C antibodies and hepatitis B antigen HBs were verified.

TESTING OF INTERFERENCE OF THE TEST ITEM WITH THE MTT ENDPOINT
- COLOR INTERFERENCE: The test item was checked for possible color interference before the study was started. 50 µL of the test item or 50 µL sterile Milli-Q water as a negative control was added to 1.0 mL Milli-Q water. The mixture was incubated for at least 1 h at 37.0 ± 1.0°C in the dark. Furthermore, 50 µL of the test item or 50 µL sterile Milli-Q water as a negative control was added to 2.0 mL isopropanol. The mixture was incubated for 2 - 3 h at room temperature with gentle shaking. At the end of the exposure time, the mixtures were centrifuged for 30 sec at 16000 g if needed and the absorbance of the solutions was determined spectrophotometrically at 570 nm in duplicate with the TECAN Infinite® M200 Pro Plate Reader. If after subtraction of the negative control, the OD for the test item solution is >0.08, the test item is considered as possibly interacting with the MTT measurement.

- MTT REDUCTION: The test item was checked for possible direct MTT reduction before the study was started. To assess the ability of the test item to reduce MTT, 50 µL of the test item was added to 1 mL MTT solution (1 mg/mL MTT in phosphate buffered saline). The mixture was incubated for approximately 3 h at 37.0 ± 1.0°C in the dark. A negative control, 50 µL sterile Milli-Q water was tested concurrently. If the MTT solution color turned blue / purple or if a blue / purple precipitate was observed the test item interacts with MTT.

NUMBER OF INDEPENDENT TEST SEQUENCES / EXPERIMENTS TO DERIVE FINAL PREDICTION: single experiment

PREDICTION MODEL / DECISION CRITERIA
- The test substance is considered to be irritant (Cat. 2) or corrosive (Cat. 1) to skin if the relative mean viability of 3 individual tissues after 15 min of exposure and 42 h of post incubation is less than or equal to 50%.
- The test substance is considered to be non-irritant (no category) to skin if the relative mean viability of 3 individual tissues after 15 min of exposure and 42 h of post incubation is greater than 50%.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount applied: 25 µL
- Concentration: neat test material

NEGATIVE CONTROL
- Amount applied: 25 µL

POSITIVE CONTROL
- Amount applied: 25 µL
- Concentration: 5%
- The positive control was re-spread after 7 min contact time.

Duration of treatment / exposure:

15 ± 0.5 min at room temperature

Duration of post-treatment incubation (if applicable):

42 ± 1 h at 37°C

Number of replicates:

triplicates for each treatment and control group

Irritation / corrosion parameter:

% tissue viability

Remarks:

mean value of 3 tissues

Run / experiment:

15 min exposure

Value:

114

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Direct-MTT reduction: Because no color change was observed in the presence of MTT it was concluded that the test item did not interact with the MTT endpoint. An additional functional check with freeze-killed or viable tissues was not performed.
- Color interference with MTT: Addition of the test item to Milli-Q and isopropanol resulted after subtraction of the blank in an OD of -0.0003 and 0.0011, respectively. Therefore, it was concluded that the test item did not induce color interference.


ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: The absolute mean OD570 of the negative control tissues was within the laboratory historical control data range.
- Acceptance criteria met for positive control: The positive control had a mean cell viability of 2.5% after 15 ± 0.5 min exposure.
- Acceptance criteria met for variability between replicate measurements: The standard deviation value of the percentage viability of three tissues treated identically was ≤ 16%.

Table 1:  Mean Absorption in the In Vitro Skin Irritation Test

	A (OD570)	B (OD570)	C (OD570)	Mean (OD570)		SD
Negative control	1.046	1.181	1.243	1.157	±	0.101
Test item	1.127	1.351	1.483	1.320	±	0.180
Positive control	0.026	0.031	0.029	0.028	±	0.003

OD = optical density

SD = Standard deviation

Triplicate exposures are indicated by A, B and C.

In this table the values are corrected for background absorption (0.044). Isopropanol was used to measure the background absorption.

 

Table 2:  Mean Tissue Viability in the In Vitro Skin Irritation Test

	Mean tissue viability (percentage of control)	Standard deviation (percentage)
Negative control	100	8.7
Test item	114	16
Positive control	2.5	0.2

 

Table 3: Historical Control Data for In Vitro Skin Irritation Studies

	Negative control (absorption; OD570)	Positive control (absorption; OD570)
Range	0.507 - 1.478	0.026 - 0.549
Mean	1.060	0.106
SD	0.153	0.085
n	159	159

SD = Standard deviation

n = Number of observations

The above mentioned historical control data range of the controls were obtained by collecting all data over the period of May 2018 to May 2021.

Interpretation of results:

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

Conclusions:

In the EPISKIN test according to OECD TG 439 the relative mean tissue viability obtained after 15 ± 0.5 min treatment with the test item compared to the negative control tissues was 114%. Since the mean relative tissue viability for the test item was above 50%, the test item is considered to be non-irritant.

Reference 2

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 - 26 Nov 2021

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:

June 2021

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

September 2019

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: EpiDerm Skin Model (EPI-SIT)

Justification for test system used:

In the interest of sound science and animal welfare, a sequential testing strategy is recommended to minimize the need of in vivo testing. One of the validated in vitro skin irritation tests is the EpiDerm test, which is recommended in international guidelines (e.g. OECD and EC).

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDerm Skin Model (EPI-SIT) (MatTek In Vitro Life Science Laboratories, Bratislava, Slovakia)
- Tissue batch number: 36108
- Date of initiation of testing: on the day of tissue receipt

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 35 ± 1.0 min at 37.0 ± 1.0°C and the remaining period of the 60 ± 1 min test item exposure at room temperature
- Temperature of post-treatment incubation: 37.0°C

REMOVAL OF TEST MATERIAL AND CONTROLS
- Volume and number of washing steps: The tissues were thoroughly rinsed with Dulbecco’s phosphate buffered saline (DPBS) to remove residual test item. If necessary cotton wool swabs were used to remove any remaining test item. After rinsing, the cell culture inserts were each dried carefully and moved to a new well on 0.9 mL pre-warmed maintenance medium until all tissues were dosed and rinsed.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1.0 mg/mL
- Incubation time: 3 h ± 5 min at 37°C
- Spectrophotometer: TECAN Infinite® M200 Pro Plate Reader
- Wavelength: 570 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: The tissue viability was assessed by an MTT QC assay. The determined OD (540-570 nm) was 1.735 ± 0.069 (acceptance criteria: 1.0 - 3.0).
- Barrier function: The barrier function was assessed by determination of the exposure time required to reduce tissue viability by 50% (ET-50) upon application of 100 µL of 1% Triton X-100. The ET-50 value was determined to be 5.47 h (acceptance criteria: 4.77-8.72 h).
- Contamination: The cells used to produce the EpiDerm™ tissue were screened for the presence of viruses (HIV-1, Hepatitis B and C), bacteria, yeast and other fungi. No contamination was detected.

TESTING OF INTERFERENCE OF THE TEST ITEM WITH THE MTT ENDPOINT (done in Episkin test, Study No.20333347)
- COLOR INTERFERENCE: The test item was checked for possible color interference before the study was started. 50 µL of the test item or 50 µL sterile Milli-Q water as a negative control was added to 1.0 mL Milli-Q water. The mixture was incubated for at least 1 h at 37.0 ± 1.0°C in the dark. Furthermore, 50 µL of the test item or 50 µL sterile Milli-Q water as a negative control was added to 2.0 mL isopropanol. The mixture was incubated for 2 - 3 h at room temperature with gentle shaking. At the end of the exposure time, the mixtures were centrifuged for 30 sec at 16000 g if needed and the absorbance of the solutions was determined spectrophotometrically at 570 nm in duplicate with the TECAN Infinite® M200 Pro Plate Reader. If after subtraction of the negative control, the OD for the test item solution is >0.08, the test item is considered as possibly interacting with the MTT measurement.

- MTT REDUCTION: The test item was checked for possible direct MTT reduction before the study was started. To assess the ability of the test item to reduce MTT, 50 µL of the test item was added to 1 mL MTT solution (1 mg/mL MTT in phosphate buffered saline). The mixture was incubated for approximately 3 h at 37.0 ± 1.0°C in the dark. A negative control, 50 µL sterile Milli-Q water was tested concurrently. If the MTT solution color turned blue / purple or if a blue / purple precipitate was observed the test item interacts with MTT.

NUMBER OF INDEPENDENT TEST SEQUENCES / EXPERIMENTS TO DERIVE FINAL PREDICTION: single experiment

PREDICTION MODEL / DECISION CRITERIA
- The test substance is considered to be irritant (Cat. 2) or corrosive (Cat. 1) to skin if the relative mean viability of 3 individual tissues after 60 min of exposure and 42 h of post incubation is less than or equal to 50%.
- The test substance is considered to be non-irritant (no category) to skin if the relative mean viability of 3 individual tissues after 60 min of exposure and 42 h of post incubation is greater than 50%.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount applied: 30 µL
- Concentration: neat test material

NEGATIVE CONTROL
- Amount applied: 30 µL

POSITIVE CONTROL
- Amount applied: 30 µL
- Concentration: 5%

Duration of treatment / exposure:

60 ± 1 min (35 ± 1.0 min at 37.0 ± 1.0°C and the remaining period at room temperature)

Duration of post-treatment incubation (if applicable):

42 h at 37°C

Number of replicates:

triplicates for each treatment and control group

Irritation / corrosion parameter:

% tissue viability

Remarks:

mean value of 3 tissues

Run / experiment:

60 min exposure

Value:

76

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Direct-MTT reduction: Because no color change was observed in the presence of MTT it was concluded that the test item did not interact with the MTT endpoint. An additional functional check with freeze-killed or viable tissues was not performed.
- Color interference with MTT: Addition of the test item to Milli-Q and isopropanol resulted after subtraction of the blank in an OD of -0.0003 and 0.0011, respectively. Therefore, it was concluded that the test item did not induce color interference.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: One negative control treated skin was considered to be an outlier and results of this skin were omitted (absolute mean OD570 of 0.761). The absolute mean OD570 of the two remaining negative control tissues was within the laboratory historical control data range.
- Acceptance criteria met for positive control: The positive control had a mean cell viability after 60 ± 1 minutes exposure of 3.1%.
- Acceptance criteria met for variability between replicate measurements: The standard deviation value of the percentage viability of three tissues treated identically was ≤ 18%.

Table 1: Mean Absorption in the In Vitro Skin Irritation Test

	A (OD570)	B (OD570)	C (OD570)	Mean (OD570)		SD
Negative control	1.577	-*	1.687	1.632	±	0.078
Test item	1.506	1.283	0.932	1.240	±	0.290
Positive control	0.054	0.046	0.052	0.051	±	0.004

OD = optical density

SD = Standard deviation

Triplicate exposures are indicated by A, B and C.

* original OD570 was 0.761

In this table the values are corrected for background absorption (0.044). Isopropanol was used to measure the background absorption.

 

Table 2: Mean Tissue Viability in the In Vitro Skin Irritation Test

	Mean tissue viability (percentage of control)	Standard deviation (percentage)
Negative control	100	4.8
Test item	76	17.7
Positive control	3.1	0.2

 

Table 3: Historical Control Data for In Vitro Skin Irritation Studies

	Negative control (absorption; OD570)	Positive control (absorption; OD570)	Positive control (viability; %)
Range	1.333 - 2.386	0.052 - 0.165	2.70 - 11.0
Mean	1.818	0.081	4.63
SD	0.257	0.023	1.77
n	30	30	30

SD = Standard deviation

n = Number of observations

The above mentioned historical control data range of the controls were obtained by collecting all data over the period of April 2015 to May 2021.

Interpretation of results:

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

Conclusions:

In the EpiDerm test according to OECD TG 439 the relative mean tissue viability obtained after 60 ± 1 min treatment with the test item compared to the negative control tissues was 76%. Since the mean relative tissue viability for the test item was above 50%, the test item is considered to be non-irritant.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not 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:

Please refer to the attached justification below and the overall justification for grouping of substances attached 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:

mean

Remarks:

out of all 3 animals

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: no effects

Remarks on result:

no indication of irritation

Remarks:

Kreiling and Jung, 1991. CAS 1185-55-3.

Irritation parameter:

iris score

Basis:

mean

Remarks:

out of all 3 animals

Time point:

24/48/72 h

Score:

0

Max. score:

2

Reversibility:

other: no effects

Remarks on result:

no indication of irritation

Remarks:

Kreiling and Jung, 1991. CAS 1185-55-3.

Irritation parameter:

conjunctivae score

Basis:

mean

Remarks:

out of all 3 animals

Time point:

24/48/72 h

Score:

0

Max. score:

3

Reversibility:

fully reversible within: 24 h

Remarks on result:

no indication of irritation

Remarks:

Kreiling and Jung, 1991. CAS 1185-55-3.

Irritation parameter:

chemosis score

Basis:

mean

Remarks:

out of all 3 animals

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

fully reversible within: 24 h

Remarks on result:

no indication of irritation

Remarks:

Kreiling and Jung, 1991. CAS 1185-55-3.

Irritant / corrosive response data:

All together, data from two source substance are available and used in a weight of evidence approach.
Trimethoxy(methyl)silane was found to be only slightly irritating. The test animals showed irritation in response to the undiluted test substance (lacrimation, congestion and oedema of the mucous membrane) which was reversible within 24 hours. Corneal opacity was present in 3 animals, which was also rapidly reversible. At the 30% concentration, the irritation was very slight, some lacrimation and congestion was present in the first 6 hours. At the 10% and 3% concentrations, no signs of irritation were observed (Juloi, L., 1992: CAS 1185-55-3).
For triethoxy(methyl)silane (CAS 2031-67-6) only one out of six animals showed conjuctivae redness with a score of 1 after 24 hours. This was resolved after 48 hours. All other irritation parameter scores were 0 for all reading time points and all animals.

Interpretation of results:

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

Conclusions:

Several studies are available from structural analogue substances CAS 2031-67-6 and CAS 1185-55-3. Slight eye irritation was partly observed which were reversed latest after 48 hours after exposure. As explained in the analogue justification, the differences between the target and the source are unlikely to lead to differences in the eye irritation potential.

Reference 2

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

9 Nov 2021

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:

adopted 26 June 2020

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

cattle

Strain:

not specified

Details on test animals or tissues and environmental conditions:

SOURCE OF COLLECTED EYES
- Source: slaughterhouse (Vitelco, 's Hertogenbosch, The Netherlands)
- Storage, temperature and transport conditions of ocular tissue: Eyes were collected and transported in physiological saline in a suitable container under cooled conditions.
- Time interval prior to initiating testing: Eyes were tested the day of arrival in the laboratory.
- Indication of any existing defects or lesions in ocular tissue samples: no
- Indication of any antibiotics used: no
- Quality check of the isolated corneas: The eyes were checked for unacceptable defects, such as opacity, scratches, pigmentation and neovascularization by removing them from the physiological saline and holding them in the light. Those exhibiting defects were discarded.
- Selection and preparation of corneas: The isolated corneas were stored in a petri dish with cMEM (Eagle’s Minimum Essential Medium containing 1% (v/v) L-glutamine and 1% (v/v) Foetal Bovine Serum).
The isolated corneas were mounted in a corneal holder (one cornea per holder) with the endothelial side against the O-ring of the posterior half of the holder. The anterior half of the holder was positioned on top of the cornea and tightened with screws. The compartments of the corneal holder were filled with cMEM of 32 ± 1°C. The corneas were incubated for the minimum of 1 hour at 32 ± 1°C.
After the incubation period, the medium was removed from both compartments and replaced with fresh cMEM. Opacity determinations were performed on each of the corneas using an opacitometer. The opacity of each cornea was read against a cMEM-filled chamber, and the initial opacity reading thus determined was recorded. Corneas that had an initial opacity reading higher than 7 were not used.

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount applied: 750 µL
- Concentration: neat

Negative and positive control
- Amount(s) applied: 750 µL

Duration of treatment / exposure:

10 ± 1 min at 32 ± 1°C

Duration of post- treatment incubation (in vitro):

120 ± 10 minutes at 32 ± 1°C

Number of animals or in vitro replicates:

triplicates for each treatment and control groups

Details on study design:

TREATMENT METHOD:
The medium from the anterior compartment was removed and 750 µL of either the negative control, positive control or test item was introduced onto the epithelium of the cornea. The holders were slightly rotated, with the corneas maintained in a horizontal position, to ensure uniform distribution of the control or the test item over the entire cornea. Corneas were incubated in a horizontal position for 10 ± 1 minutes at 32 ± 1°C.

REMOVAL OF TEST SUBSTANCE
- Number of washing steps after exposure period: After the incubation the solutions were removed and the epithelium was washed with MEM with phenol red (Eagle’s Minimum Essential Medium, Life Technologies) and thereafter with cMEM. Possible pH effects of the test item on the corneas were recorded. The medium in the posterior compartment was removed and both compartments were refilled with fresh cMEM. Subsequently the corneas were incubated for 120 ± 10 minutes at 32 ± 1°C.

METHODS FOR MEASURED ENDPOINTS:
- Corneal opacity: The opacity of a cornea was measured by the diminution of light passing through the cornea.
The light was measured as illuminance (I = luminous flux per area, unit: lux) by a light meter.
- Corneal permeability: passage of sodium fluorescein dye measured with the aid of a microtiter plate reader (OD490)

SCORING SYSTEM: In Vitro Irritancy Score (IVIS) = mean opacity value + (15 x mean OD490 value)

DECISION CRITERIA:
Test substance with an IVIS > 55 was regarded as serious eye damage and labelled Category 1 according to CLP/EPS/GHS.
Test substance with an IVIS ≤ 3 was regarded as non-irritant and labelled in no category.
Test substance with an IVIS > 3; ≤ 55 no prediction can be made.

Irritation parameter:

in vitro irritation score

Remarks:

mean value of 3 corneas

Run / experiment:

10 min exposure

Value:

16

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other:

Remarks:

no definite prediction on ocular irritation can be made

Other effects / acceptance of results:

OTHER EFFECTS:
- Visible damage on test system: The corneas treated with the positive control and test item were observed to be turbid after the 10 min treatment.
- pH effects: No pH effects of the negative and positive controls as well as of the test item were observed on the rinsing of the corneas with MEM (with phenol red).


ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes for two negative controls: the negative control responses resulted in opacity and permeability values that were less than the upper limits of the laboratory historical range. One of the negative control eyes was excluded from the analysis since the permeability was increased. This resulted in an IVIS above the cut-off value of 3.0. This had no impact on the study validity.
- Acceptance criteria met for positive control: yes: the positive control gave an in vitro irritancy score that fell within two standard deviations of the current historical mean.

Table 1: Summary of Opacity, Permeability and In Vitro Scores

Treatment	Mean Opacity^1	Mean Permeability^1	Mean In vitro Irritation Score^1, 2
Negative control	-0.3	-0.018	-0.6
Positive control (Ethanol)	19	1.110	36
Test item	8.7	0.474	16

¹  Calculated using the negative control corrected mean opacity and mean permeability values for the positive control and test item.

²  In vitro irritancy score (IVIS) = mean opacity value + (15 x mean OD₄₉₀ value).

 

Table 2: Opacity Score

Treatment	Opacity before treatment	Opacity after treatment	Final Opacity^1	Negative control corrected Final Opacity^2	Mean Final Opacity
Negative control	3.7*	2.5*	-1.2*		-0.3
	1.9	2.1	0.2
	1.9	1.0	-0.9
Positive control	3.4	22.5	19.1	19	19
	1.5	17.5	15.9	16
	3.5	25.8	22.3	22
Test item	2.7	10.5	7.8	7.8	8.7
	2.2	11.2	9.0	9.0
	0.9	10.0	9.1	9.1

Calculations are made without rounding off.

1   Final Opacity = Opacity after treatment – Opacity before treatment.

²   Negative control corrected Final Opacity = Final opacity – Mean final opacity negative control.

³  In case the mean final opacity of the negative control is below zero, no correction will be made.

* Excluded from analysis.

 

Table 3: Permeability Score Individual Values (Uncorrected)

Treatment	Dilution factor	OD490	OD490	OD490	Average OD	Final OD	Mean final negative control
		1	2	3
Negative control	1	0.583*	0.589*	0.587*	0.586*	0.586*^1	-0.018
	1	-0.011	-0.020	-0.018	-0.016	-0.016
	1	-0.022	-0.019	-0.020	-0.020	-0.020
Positive control	1	1.381	1.378	1.380	1.380	1.380
	1	1.051	1.042	1.040	1.044	1.044
	1	0.853	0.852	0.852	0.852	0.852
Test item	1	0.400	0.395	0.394	0.396	0.396
	1	0.477	0.477	0.481	0.478	0.478
	1	0.496	0.493	0.486	0.492	0.492

*  Excluded from analysis.

Calculations are made without rounding off.

 

Table 4: Permeability Score Individual Values (Corrected)

Treatment	Dilution factor	Negative control corrected OD490 1#	Negative control corrected OD490 2#	Negative control corrected OD490 3#	Negative control corrected OD490 Average	Negative control corrected final OD490	Average OD
Positive control	1	1.399	1.396	1.398	1.398	1.398	1.110
	1	1.069	1.060	1.058	1.063	1.063
	1	0.871	0.870	0.870	0.871	0.871
Test item	1	0.418	0.413	0.412	0.415	0.415	0.474
	1	0.495	0.495	0.499	0.497	0.497
	1	0.514	0.511	0.504	0.510	0.510

Calculations are made without rounding off.

^# OD₄₉₀ values corrected for the mean final negative control permeability (-0.018).

 

Table 5: In Vitro Irritancy Score

Treatment	Final Opacity^2	Final OD490^2	In vitro Irritancy Score^1
Negative control	-1.2*	0.586*	7.6*
	0.2	-0.016	0.0
	-0.9	-0.020	-1.2
Positive control	19	1.398	40
	16	1.063	32
	22	0.871	35
Test item	7.8	0.415	14.1
	9.0	0.497	16.5
	9.1	0.510	16.7

¹  In vitro irritancy score (IVIS) = opacity value + (15 x OD₄₉₀ value).

²  Positive control and test item are corrected for the negative control.

* Excluded from analysis.

 

 

Table 6: Historical Control Data for the BCOP Studies

	Negative control			Positive control
	Opacity	Permeability	In vitro Irritancy Score	In vitro Irritancy Score
Min	-2.50	-0.017	-2.50	26
Max	3.70	0.065	4.00	86
Mean	0.86	0.002	0.89	50
SD	1.26	0.009	1.28	14
n	143	143	143	143

SD = Standard deviation

n = Number of observations

The above mentioned historical control data range of the controls were obtained by collecting all data over the period of May 2018 to May 2021.

 

Interpretation of results:

other: non-corrosive

Conclusions:

In a BCOP test according to OECD TG 437 and in compliance with GLP, dimethoxy(dimethyl)silane induced ocular irritation as assessed for both endpoints (corneal opacity and
permeability), resulting in a mean in vitro irritancy score (IVIS) of 16 after 10 minutes of treatment. Since the test substance induced an IVIS > 3 ≤ 55, no definitive prediction on ocular irritation can be made.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation

Dimethoxy(dimethyl)silane was evaluated for its ability to induce skin irritation on human three dimensional epidermal models (EPISKIN Small model (EPISKIN-SM^TM) and EpiDerm (EPI-SIT)) according to OECD TG 439 and in compliance with GLP (Charles River Laboratories, 2022).

In the EPISKIN test, 25 µL of the undiluted test item was applied directly on top of three skin tissues (EPISKIN-SM^TM). Three tissues were treated with 25 µLphosphate buffered saline (PBS, negative control) and three tissues with 25 µL 5%sodium dodecyl sulfate (SDS, positive control). After the exposure period of 15 ± 0.5 min at room temperature, the tissues were washed followed by a 42±1 h post-incubation period at 37°C. After incubation, determination of the cytotoxic (irritancy) effect was performed. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) at the end of the treatment. No colour interference or reduction of MTT by the test item was concluded based on the respective pre-tests.

Skin irritation is expressed as the remaining cell viability after exposure to the test item. The relative mean tissue viability obtained after 15 ± 0.5 min treatment with the test item compared to the negative control tissues was 114%. Since the mean relative tissue viability for the test item was above 50%, the test item is considered to be non-irritant in the EPISKIN test.

The positive control had a mean cell viability of 2.5% after 15 ± 0.5 min exposure. The absolute mean OD570 (optical density at 570 nm) of the negative control (PBS) tissues was within the laboratory historical control data range. The standard deviation value of the percentage viability of three tissues treated identically was ≤ 16%, indicating that the test system functioned properly.

 

In the EpiDerm test, the test item was applied undiluted (30 µL) directly on top of three skin tissues (EPI-SIT) for 60±1 min (35 ± 1.0 min at 37.0 ± 1.0°C and the remaining period at room temperature). Three tissues were treated with 30 µL Dulbecco’s phosphate buffered saline (DPBS, negative control) and three tissues with 30 µL 5% sodium dodecyl sulfate (SDS, positive control). After a 42 h post-incubation period at 37°C, determination of the cytotoxic (irritancy) effect was performed via MTT assay. The relative mean tissue viability obtained after 60±1 min treatment with the test item compared to the negative control tissues was 76%. Since the mean relative tissue viability for the test item was above 50%, the test item is considered to be non-irritant in the EpiDerm test.

The positive control (5% SDS) had a mean cell viability after 60±1 min exposure of 3.1%. One negative control (DPBS) treated skin was considered to be an outlier and results of this skin were omitted (absolute mean OD570 of 0.761). The absolute mean OD570 of the remaining two negative control tissues was within the laboratory historical control data range. The standard deviation value of the percentage viability of three (test substance and positive control) or two (negative control) tissues treated identically was ≤ 18%, and thus the in vitro skin irritation test met the acceptability criteria.

 

In conclusion, dimethoxy(dimethyl)silane is non-irritant in the in vitro skin irritation test under the experimental conditions of the EPISKIN Small Model^TM and EpiDerm Skin Model.

Eye irritation

The eye hazard potential of dimethoxy(dimethyl)silane was tested in a BCOP test according to OECD TG 437 and in compliance with GLP (Charles River Laboratories, 2022).

After a first opacity measurement, 750 µL of the neat test item, the positive control (ethanol) or the negative control (physiological saline) was applied for 10 min 32 ± 1 °C on the top of three fresh corneas. After the incubation phase the test item, the positive, and the negative controls were each washed from the corneas. Further, the corneas were incubated for another 120 minutes at 32 ± 1 °C. Afterwards, opacity was measured a second time. After the opacity measurements, permeability of the corneas was determined by measuring spectrophotometrically the transfer of sodium fluorescein after incubation in a horizontal position for 90 min at 32 ± 1 °C.

The individual in vitro irritancy scores (IVIS) for the negative controls (physiological saline) ranged from 0.0 to -1.2. One of the negative control eyes was excluded from the analysis since the permeability was increased. This resulted in an IVIS above the cut-off value of 3.0. The mean of the two remaining eyes met the acceptability criteria, therefore, this had no impact on the study validity.

The individual positive control (ethanol) in vitro irritancy scores ranged from 32 to 40. The corneas treated with the positive control item were observed to be turbid after the 10 minutes of treatment.

The corneas treated with the test item showed opacity values ranging from 7.8 to 9.1 and permeability values ranging from 0.415 to 0.510. The corneas were turbid after the 10 minutes of treatment with the test item. No pH effect of the test item was observed on rinsing of the corneas with MEM (with phenol red). Hence, the in vitro irritancy scores ranged from 14 to 17 after 10 minutes of treatment with the test item.

In conclusion, dimethoxy(dimethyl)silane induced an IVIS > 3 ≤ 55, indicating that no definitive prediction on ocular irritation can be made.

 

A further in vitro eye irritation study is planned for dimethoxy(dimethyl)silane to come to a final conclusion on its eye irritation properties. 

As an interim measure, the hazard assessment on eye irritation was performed based on available data from the structural analogues trimethoxy(methyl)silane (CAS 1185-55-3) and triethoxy(methyl)silane (CAS 2031-67-6).

Details on read across justifications can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

 

The available study for eye irritation with the structural analogue substance trimethoxy(methyl)silane (CAS 1185-55-3) was conducted in accordance with OECD TG 405 and to GLP (Kreiling and Jung, 1991). Trimethoxy(methyl)silane was found to be not irritating to rabbit eyes.

Furthermore, an eye irritation study on the structural analogue substance triethoxy(methyl)silane (CAS 2031-67-6) which was not in compliance with GLP, but was equivalent or similar to OECD TG 405, showed that triethoxy(methyl)silane was not irritating to rabbit eyes. Only minor, transient eye irritation was observed following instillation of the test material into the eyes of six rabbits. The Draize score of 0.06 out of 3 indicates that triethoxy(methyl)silane would not be considered irritating to the eyes of rabbits (Bushy Run Research Center, 1981). All studies are in agreement of the lack of eye irritation potential of the structural analogue substances, trimethoxy(methyl)silane and triethoxy(methyl)silane. This therefore strengthens the overall assumption that the registered substance, dimethoxy(dimethyl)silane, will not be an eye irritant.

Justification for classification or non-classification

The available data on irritation / corrosion of the registration substance and structural analogue substances, trimethoxy(methyl)silane and triethoxy(methyl)silane, respectively, do not meet the criteria for classification according to Regulation (EC) No 1272/2008, and are therefore conclusive but not sufficient for classification of the registered substance.