Triethoxysilane

Endpoint summary

Description of key information

Oral (OECD  TG 401), rat: LD50 > 1000 < 2000 mg/kg bw (female) and LD50>2000 mg/kg bw (male)
Dermal (OECD TG 402), rabbit: LD50 > 2000 mg/kg bw (limit test)
Inhalation (OECD  403) rat, 4 h exposure: LC50 > 500 < 1300 mg/m³

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: The study did not meet current guideline requirements for acute oral toxicity. It does, however, add weight of evidence for acute toxicity potential.

Qualifier:

no guideline followed

Principles of method if other than guideline:

No guideline indicated. The methodology is broadly similar to the now deleted OECD 401 guidance with the deviation that only single sex was used.

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 3-4 weeks
- Weight at study initiation: 90-120 g (males)
- Diet: Wayne diets ad libitum except during period of manipulation or confinement.
- Water: Water ad libitum except during period of manipulation or confinement.

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

No data

Doses:

1.0, 4.0, 8.0 and 16.0 ml/kg

No. of animals per sex per dose:

5 males

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Other examinations performed: clinical signs and body weight.

Statistics:

LD50 was calculated by the moving average method based on a 14-day observation period.

Sex:

male

Dose descriptor:

LD50

Effect level:

5 400 mg/kg bw

Based on:

test mat.

95% CL:

2 923 - 9 976

Remarks on result:

other: dose given in ml/kg, converted using a relative density of 0.875.

Mortality:

16.0 ml/kg -5/5 deaths (from 30 min to 4.25 hr after dosing)
8.0 ml/kg -3/5 deaths
4.0 and 3.0 mL/kg -1/5 deaths

Clinical signs:

other: 16.0 ml/kg -sluggishness and unsteady gait prior to death. 8.0 ml/kg- unsteady gait, prostration, piloerection.

Gross pathology:

In animals that died: lungs mottled red, pink and maroon; livers mottled pink and red; stomachs transparent, gas-filled, distended, glandular portions red; medullae of kidneys pink; intestines gas-filled, distended, transparent or red; adrenals pink. In surviving animals no remarkable findings.

Table 1: Result summary.

Dose (ml/kg)	Mortality	Days to death	Weight change	Signs
16.0	5/5	0,0,0,0,0	-	Sluggish, unsteady gait 1min; prostrate 3 min; death 30 min to 4.25 hr.
8.0	3/5	0,1,2	-20 to 87 mg	Unsteady gait 4 min; prostrate 1.75 hr; death of 1 at 4.5 hr; pilo-erection 1 day.
4.0	1/5	8	107 to 129 mg
1.0	1/5	9	87 to 115 mg

Interpretation of results:

harmful

Remarks:

Migrated information Criteria used for interpretation of results: expert judgment

Conclusions:

A limited report of an acute oral study without guideline or GLP compliance (reliability score 4), identified oral LD50 values in the rat of 5400 mg/kg bw, for males.

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11-02-1994 to 22-03-1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

yes

Remarks:

; only two doses tested, the guideline required 3

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

other: CDF® (F344)/Crl BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Not reported.
- Age at study initiation: Young adult.
- Weight at study initiation: 141 - 178 g
- Fasting period before study: The rats were fasted approximately 18-20 hours prior to dosing and returned to feed 3-4 hours after dosing.
- Housing:Individual suspended wire-mesh cages.
- Diet: Purina® Certified Rodent Chow® provided ad libitum
- Water: Municipal water were provided ad libitum
- Acclimation period: The animals were acclimated to laboratory conditions for a minimum of seven days prior to initiation of dosing.

ENVIRONMENTAL CONDITIONS
- Temperature : 68-76°F
- Humidity (%): 32-82
- Photoperiod (hrs dark / hrs light): 12/ 12.

IN-LIFE DATES: From: 20-04-1994 To: 21-05-1994

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DOSAGE PREPARATION : The test material was dosed undiluted based on density (specific gravity).The dose volume was determined by dividing the dose level, expressed in g/kg, by the specific gravity (0.91 g/mL). Individual doses were calculated based on body weights taken just prior to dosing and appropriate dose volumes.

Doses:

1000 and 2000 mg/kg.

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: The rats were observed at approximately 1.0, 3.0 and 4.0 hours post-dose on day 0 and twice daily (morning and afternoon) thereafter for 14 days for clinical observation and mortality. Body weights were obtained and recorded on Days -1, 0 (initiation), 7 and 14 (study termination).
- Necropsy of survivors performed: yes.Upon study termination, all rats were euthanized by carbon dioxide asphyxiation.
- Other examinations performed: clinical signs, body weight, organ weights, histopathology,cranial, thoracic and abdominal cavities were examined for all animals.

Statistics:

Not reported

Sex:

male

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Sex:

female

Dose descriptor:

LD50

Effect level:

> 1 000 - < 2 000 mg/kg bw

Based on:

test mat.

Mortality:

There were three delayed deaths noted in the 2000 mg/kg bw female group, which occurred on study day 6, 7 and 10. All other animals survived through study termination (Day 14).

Clinical signs:

other: Ante mortem clinical findings included decreased defecation and urination, mucoid feces, hypothermia and prostration. For the surviving animals, clinical findings were noted in both dose groups, but findings for the male rats were limited to two of the 2

Gross pathology:

Gastrointestinal abnormalities and external mattings were noted for the three rats found dead. One rat had reddened adrenal glands. There were no other gross necropsy findings for animals that died during the study.
Motted lungs and ovarian cysts were noted at the scheduled necropsy for one and two rats, respectively. These findings were considered unrelated to the test material. There were no other significant changes observed for all examined tissues at necropsy.

Table 1. Summary.

Dose level (mg/kg)	Study Day												Total Mortality
	0		1		2		3		4		5-14
	M	F	M	F	M	F	M	F	M	F	M	F	M	F	C
1000	-	-	-	-	-	-	-	-	-	-	-	-	0/5	0/5	0/10
2000	-	-	-	-	-	-	-	-	-	-	-	3	0/5	3/5	3/10

M = Males F= Females C= Combined.

Interpretation of results:

harmful

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

An acute oral toxicity study conducted according to the now deleted OECD 401 guideline and GLP, the LD50 of triethoxysilane was found to be greater than 2000 mg/kg for male albino rats and greater than 1000 mg/kg but less than 2000 mg/kg for female’s albino rats.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

discriminating dose

Value:

1 000 mg/kg bw

Quality of whole database:

This study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: The study did not meet current guideline requirements for acute inhalation toxicity. It does, however, add weight of evidence for acute toxicity potential.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Acute inhalation toxicity study in rats where they were introduced in a gasketed drawer-type cage and exposed to substantially saturated vapour concentration of triethoxysilane.

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Diet: Wayne diets ad libitum except during period of manipulation or confinement.
- Water: Water ad libitum except during period of manipulation or confinement.

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

not specified

Details on inhalation exposure:

Substantially saturated vapour was prepared by spreading 50 to 100 g of chemical over 200 cm2 area on shallow tray placed near the top of a 120- litre glass chamber which was then sealed for at least 16 h while an intermittently operated fan agitates the internal chamber atmosphere. Rats were then introduced into a gasketed drawer-type cage designed and operated to minimise vapour loss.

Analytical verification of test atmosphere concentrations:

not specified

Remarks on duration:

No data

Concentrations:

Substantially saturated vapour

No. of animals per sex per dose:

6

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: Not reported.
- Frequency of observations and weighing: Not reported.
- Necropsy of survivors performed: yes.
- Other examinations performed: clinical signs and histopathology.

Sex:

not specified

Dose descriptor:

other: LT50

Effect level:

4.95 other: h

Based on:

test mat.

95% CL:

4 - 6.13

Remarks on result:

other: Exposure duration: 3.5 and 7 h

Mortality:

7.0 h- 6/6 mortality seen. All dead within 7 h of exposure.
3.5 h- 0/6 .

Clinical signs:

other: 7.0 h -Lacrimation, salivation within 30 min, slight coordination loss within 40 min; severe coordination loss within 1 h and anesthesia within 1.5 h. 3.5 h - Signs time-related as above

Body weight:

3.5 h - weight change: 46 to 69 mg

Gross pathology:

7.0 h- lungs red with many dark red foci; stomachs and intestines gas-filled.

Interpretation of results:

toxic

Remarks:

Migrated information Criteria used for interpretation of results: expert judgment

Conclusions:

An acute inhalation toxicity study not following a guideline and without GLP identified a LT50 of 4.95 h in substantially saturated vapour for triethoxysilane.

Reference 2

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

only 2 concentrations tested

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

other: CDF®(F-344)/ CrlBR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Not reported.
- Age at study initiation: 66 d (group 1) and 57 d (group 2)
- Weight at study initiation: 179-207 g (males) and 129-135 g (females)
- Housing: Individual stainless steel wire mesh cages.
- Diet: Certified pelleted rodent chow® #5002 provided ad libitum except during exposure.
- Water: Tap water was supplied ad libitum except during exposure.
- Acclimation period: Group 1 animals were acclimated for a period of 16 days. Group 2 animals were acclimated for a period of seven days.

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and glass exposure chamber.
- Exposure chamber volume: 160 Liters.
- Source and rate of air: Compressed air at 20 L/min.
- System of generating particulates/aerosols: The test article was metered via a syringe drive (Harvard Model 22) to a glass vaporisation column (2.5 cm² diameter x 22 cm² height) filled approximately three-quarters full with glass beads ranging from 4-6 mm in diameter. The test article was delivered to the centre of the glass beads where compressed air entering the base of the column at 20 L/min, measured by a flow meter (Fischer & Porter, FP-1-27-G-10/55), facilitated vaporisation. The test material was swept through a condensation trap and into the exposure chamber. Additional dilution air measured by a flow meter (Fischer & Porter, FP-4-21-G-10/55) was used to decrease the vapour concentration to the desired level.
- Method of particle size determination: gravimetrically.
- Treatment of exhaust air: The test atmosphere was exhausted to a fume hood.
- Temperature, humidity in air chamber: 24 °C and 2% - Group 1. 23 °C and 6% - Group 2. The low relative humidity resulted from the dry compressed air used to generate the vapour.

TEST ATMOSPHERE
- Brief description of analytical method used: Exposure atmosphere was measured using Infrared spectrophotometer (IR) analysis methods (Wilks Miran 1A Model 5688).
- Samples taken from breathing zone: yes

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: The exposure atmosphere was judged to have no aerosols present. Negligible amounts were collected during the sampling for the particle size determination.
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.):Not reported

Analytical verification of test atmosphere concentrations:

yes

Remarks:

Infrared spectrophotometer (IR) analysis methods (Wilks Miran 1A Model 5688).

Duration of exposure:

4 h

Concentrations:

0.5 (Group 1) and 1.3 mg/L (Group 2).

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing:Observed for pharmacotoxic signs pre-exposure and immediately after exposure; two times daily during the 14-day post-exposure period, one for pharmacotoxic signs and once for mortality only. Body weights were recorded just prior to the exposure, and at 7 and 14 days post-exposure and when animals were found dead.
- Necropsy of survivors performed: yes. All animals were euthanized by intraperitoneal sodium pentobarbital overdose and exsanguinations via the abdominal aorta and underwent complete necropsy.
- Other examinations performed: clinical signs, body weight, organ weights, histopathology.

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 500 - < 1 300 mg/m³ air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

500 mg/m³ – One female died on Day 13 post administration
1300 mg/m³ – All the animals died by Day 13 post administration

Clinical signs:

other: 500 mg/m³ –During the two weeks post-exposure period the significant pharmacokinetic signs observed for these animals were death, gasping, wheezing, laboured breathing, slow respiration, decreased activity and excessive lacrimation. 1300 mg/m³ – During

Body weight:

500 mg/m³ – All animals lost weight during the first post-exposure observation week (approximately 13% for males and 11% for females) based on mean group body weight. During the 2nd week males started regaining weight but females continued to lose.
1300 mg/m³ - All animals lost weight during the first week (approximately 19% for males and 11% for females) and none survived to the 2nd week.

Gross pathology:

500 mg/m³ – One male and three females were observed with red discoloration of the lung ranging from trace to moderate.
1300 mg/m³ – All animals exhibited red discoloration of the lungs from mild to severe. No other significant macroscopic abnormalities were observed.

Table 3. Number of Animals Found Dead on Day of Study:

Dose (mg/L)	Study Day
	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
0.5	0	0	0	0	0	0	0	0	0	0	0	0	0	1	0
1.3	0	0	2	1	0	0	1	0	0	1	1	2	1	1	NA

NA- Not Applicable, all animals dead.

Interpretation of results:

toxic

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Acute inhalation toxicity study conducted according to OECD 403 and GLP, identified a LC50 in the range of >0.5 < 1.3 mg/L for triethoxysilane.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

discriminating conc.

Value:

500 mg/m³ air

Quality of whole database:

This study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Acute toxicity: via dermal route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: The study did not meet current guideline requirements for acute dermal toxicity. It does, however, add weight of evidence for acute toxicity potential.

Qualifier:

no guideline followed

Principles of method if other than guideline:

No guideline indicated. The methodology is broadly similar to OECD 402, however only 4 test animals per dose - sex not stated. 24 h occluded contact.

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rabbit

Strain:

other: Albino

Sex:

not specified

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 3-5 months
- Diet: Wayne diets ad libitum except during period of manipulation or confinement.
- Water: Water ad libitum except during period of manipulation or confinement.

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

TEST SITE
- Area of exposure: Clipped skin of the dorsal area of the truck.
- Type of wrap if used: The test substance was kept in contact under impervious sheetings

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Any remaining fluid was removed to prevent ingestion

Duration of exposure:

24 hours

Doses:

2.0, 4.0 and 8.0 ml/kg

No. of animals per sex per dose:

4

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Other examinations performed: clinical signs and body weight, organ weights.

Statistics:

LD50 was calculated by the moving average method based on a 14-day observation period.

Sex:

not specified

Dose descriptor:

LD50

Effect level:

3 500 mg/kg bw

Based on:

test mat.

95% CL:

2 144 - 5 714

Remarks on result:

other: dose given in ml/kg, converted using a relative density of 0.875

Mortality:

8.0 ml/kg - 4/4 deaths
4.0 ml/kg - 2/4 deaths

Clinical signs:

other: Not reported.

Gross pathology:

In animals that died, livers with tan mottling were seen. In surviving animals no remarkable findings were observed. .

Other findings:

- Other observations: Erythema, ecchymosis and oedema at all dose levels, plus desquamation in survivors at Day 14

Table 1: Skin penetration, single dose to rabbit.

Dose (ml/kg)	Mortality	Days to death	Weight change	Skin irritation	Signs
8.0	4/4	0,0,1,3	-	Erythema, ecchymosis, edema	Death of 2 at 30 to 40 min
4.0	2/4	3,4	-82 to 33 mg	As above plus desquamation at 14 days
2.0	0/4	-	-127 to 280 mg	As above

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

A limited report of an acute dermal study without guideline or GLP compliance (reliability score 4), identified dermal LD50 values in the rabbit of 3500 mg/kg bw.

Reference 2

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11-02-1994 to 22-03-1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rabbit

Strain:

other: Albino white

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Not reported.
- Age at study initiation: Young adult.
- Weight at study initiation: 2124 - 2430 g
- Housing: Individual suspended mesh-bottom cages.
- Diet: Purina® Certified Rodent Chow® provided ad libitum
- Water: Municipal water were provided ad libitum
- Acclimation period: The animals were acclimated to laboratory conditions for a minimum of five days prior to initiation of dosing.

ENVIRONMENTAL CONDITIONS
- Temperature: 68-71°F
- Humidity (%): 34-76
- Photoperiod (hrs dark / hrs light): 12/ 12.

IN-LIFE DATES: From: 22-04-1994 To: 06-05-1994

Type of coverage:

semiocclusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

TEST SITE
- Area of exposure: Clipped skin of the dorsal area of the trunk
- % coverage: 23%
- Type of wrap if used: Plastic wrap that was secured with Dermiform®.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The exposed site was wiped with disposable paper towels moistened with tepid tap water
- Time after start of exposure: 24 h

Duration of exposure:

24 h

Doses:

2000 mg/kg

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Clinical observation and mortality were observed at approximately 1.0, 3.0 and 4.0 hours post-dose on Day 0 and twice daily thereafter for 14 days. Body weights were obtained and recorded on Days 0 (initiation), 7 and 14 (study termination). Also the application sites were examined for erythema, edema and other dermal findings beginning approximately 30-60 minutes after bandage removal and daily thereafter for thirteen days. The rabbit were shaved to facilitate dermal observations on Days 4, 7, 10 and 14
- Necropsy of survivors performed: yes. Upon termination of the study, the rabbits were euthanized by intravenous injection of sodium pentobarbital solution.
- Other examinations performed: clinical signs, body weight, organ weights, histopathology, cranial, thoracic and abdominal cavities were examined for all animals.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

There were no deaths during the study.

Clinical signs:

other: There were no clinical findings related to systemic toxicity. local effects were observed.

Gross pathology:

No treatment-related gross necropsy findings.

Other findings:

- Other observations:The test material induced severe erythema, moderate to severe edema, fissuring, eschar and exfoliation on all animals. In addition, six rabbits had corrosion and one site had blanching. Desquamation was present on all animals by day 5 and persisted throughout the remainder of the study. There were no other dermal findings. Severe erythema and slight to moderate edema persisted through study termination (Day 14) for four rabbits. Erythema decreased to slight and very slight for five and one animals, respectively, and edema decreased to slight or very slight for nine rabbits by study termination.

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

In an acute dermal toxicity study conducted according to OECD 402 and GLP, the LD50 of triethoxysilane was found to be greater than 2000 mg/kg when administered once for 24 hours to the shaved, intact skin of male and female albino rabbits.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Quality of whole database:

This study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Additional information

Studies were chosen as key when the available study was of relevance and of sufficient quality for classification, labelling and for risk assessment. Other available data are included as supporting studies.

The key acute oral toxicity study which was conducted in compliance with GLP and according to the now deleted OCED TG 401, reports an LD50 value of >2000 mg/kg for male rats and >1000 mg/kg - <2000 mg/kg for female rats after a single oral administration (DCC, 1995a). Three delayed deaths occurred in the 2000 mg/kg group (females), on study day 6, 7 and 10. Ante mortem clinical findings included decreased defecation and urination, mucoid faeces, hypothermia and prostration. For the surviving animals, clinical findings were noted in both dose groups, but findings for the male rats were limited to two of the 2000 mg/kg group animals with clear ocular discharge present on the day of dosing. All other findings were noted for the females. Clear ocular discharge was observed for eight rats. Various external matting was noted in seven animals. Six rats were hypoactive and/or ataxic. All surviving animals appeared normal by day 10 or earlier and throughout the remainder of the study, with the exception of one rat in the 1000 mg/kg dose group which had dried yellow urogenital staining present at the study termination. A limited report without guideline or GLP compliance (reliability score 4) on acute oral toxicity of triethoxysilane was also available, which reports an oral LD50 value of 5400 mg/kg bw (dose given in ml/kg, converted using a relative density of 0.875), in male rats (Wacker, 1978). Mortality was seen in 5/5 and 3/5 male rats dosed with 14000 mg/kg bw and 7000 mg/kg bw, respectively. The results of both studies are in agreement with the acute toxicity potential of triethoxysilane via the oral route.

 

The key acute inhalation toxicity study which was conducted in compliance with GLP and according to OECD TG 403 reports an LC50 value of > 500 mg/m³ - <1300 mg/m³ for triethoxysilane vapour in rat after 4 hours. All animals exposed to 1300 mg/m³ died post exposure (day 13) while only one female died (day 13) when exposed to 500 mg/m³. Clinical signs in animals exposed to 1300 mg/m³ included decreased activity and excess lacrimation. During the two weeks post-exposure period the significant signs observed were decreased activity, laboured breathing, wheezing, corneal opacity, gasping and excessive lacrimation (DCC, 1995b).A limited report on acute inhalation toxicity without guideline compliance or GLP was also available, which reports an LT50 of 4.95 h in substantially saturated vapour for triethoxysilane (Wacker, 1978). This study further supports the acute toxicity potential of triethoxysilane by the inhalation route.

In the key acute dermal toxicity study which was conducted according to OECD TG 402, the LD50 of triethoxysilane was found to be greater than 2000 mg/kg when administered once for 24 hours to the shaved, intact skin of male and female albino rabbits. There were no deaths or clinical findings during the study. However, the test material induced severe erythema, moderate to severe edema, fissuring, eschar and exfoliation in all animals. In addition, corrosive effects were evident in six rabbits, with concurrent blanching at one site. Desquamation was present in all animals by day 5 and persisted throughout the remainder of the study. There were no other dermal findings. Severe erythema and slight to moderate edema persisted until study termination (day 14) in four rabbits. Erythema decreased to slight and very slight in five and one animals, respectively, and edema decreased to slight or very slight in nine rabbits by study termination (DCC, 1995c).A limited acute dermal toxicity study which was not compliant with GLP or carried out according to guideline (reliability score 4) reports a dermal LD50 value in the rabbit of 3500 mg/kg bw (dose given in ml/kg, converted using a relative density of 0.875) (Wacker, 1978). The irritation potential of the substance was seen again with erythema, ecchymosis and oedema at all dose levels, and desquamation prevailed in survivors at day 14. The results of both studies support the lack of acute toxicity potential of triethoxysilane via the dermal route.

Justification for selection of acute toxicity – oral endpoint
The key study was selected for assessment.

Justification for selection of acute toxicity – inhalation endpoint
The key study was selected for assessment.

Justification for selection of acute toxicity – dermal endpoint
The key study was selected for assessment.

Justification for classification or non-classification

Based on the available information on acute oral toxicity, triethoxysilane is proposed to be classified as R22 ‘’Harmful if swallowed’’ according to the criteria of EU Directive 67/548/EEC, and Acute Toxic 4 (oral) under Regulation 1272/2008.

The available data on acute inhalation toxicity necessitates the classification of triethoxysilane as R23 ''Toxic by inhalation'' according to the criteria of EU Directive 67/548/EEC, and Acute Toxic 2 (inhalation) under Regulation 1272/2008.

The available data on acute dermal toxicity of the substance do not meet the criteria for classification according to Regulation 1272/2008 or EU Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.