(3-chloropropyl)triethoxysilane

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

There are no reproductive toxicity data available for (3-chloropropyl)triethoxysilane (CAS 5089-70-3).

Two studies have been proposed with the registered substance, a repeated dose toxicity study to be conducted according to OECD Test Guideline 408 and in compliance with GLP, and a developmental toxicity study to be conducted in the rabbit according to OECD Test Guideline 414 and in compliance with GLP. An extended one-generation reproductive toxicity study (required in Section 8.7.3 of REACH Annex IX) may be proposed, if required, when the results of the proposed 90-day repeated-dose and developmental toxicity studies are available.

Effect on fertility: via oral route

Endpoint conclusion:

no study available (further information necessary)

Effect on fertility: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

813 mg/m³

Study duration:

subacute

Species:

rat

Quality of whole database:

Klimish score 1

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

There are no reproductive toxicity data available for (3-chloropropyl)triethoxysilane (CAS 5089-70-3).

Two studies have been proposed with the registered substance, a repeated dose toxicity study to be conducted according to OECD Test Guideline 408 and in compliance with GLP, and a developmental toxicity study to be conducted in the rabbit according to OECD Test Guideline 414 and in compliance with GLP. An extended one-generation reproductive toxicity study (required in Section 8.7.3 of REACH Annex IX) will be considered when the results of the proposed 90-day repeated-dose and developmental toxicity studies are available.

Good quality reproductive screening data from an inhalation study with the analogous substance (3-chloropropyl)trimethoxysilane are included and used as read-across data for interim risk assessment.

Both the registered and read-across substances share a common hydrolysis product, (3-chloropropyl)silanetriol, with the other hydrolysis products being ethanol and methanol respectively. Since neither methanol nor ethanol would contribute to reproductive toxicity effects in rodents at the dose levels tested, it is considered that any observed toxicological effects would be due to the action of the (3-chloropropyl) silyl moiety. Both substances have log K_ow in the range that is favourable for absorption across the respiratory tract (ethoxy log K_ow= 3.13and methoxy log K_ow= 2.0). It is therefore considered valid to read-across the results for the trimethoxy analogue to fill data gaps for the registered substance.

In the combined repeated dose toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP, (3-chloropropyl)trimethoxysilane was tested via the inhalation route of exposure, whole-body in rats, up to and including the highest concentration of 100 ppm (813 mg/m³). No signs of adverse effects on reproduction and development were observed. Based on the results the NOAEC for reproduction was concluded to be at least 100 ppm (813 mg/m³), the highest concentration tested (RCC, 2005).

Effects on developmental toxicity

Description of key information

In a prenatal developmental toxicity study conducted according to OECD Test Guideline 414 and in compliance with GLP with the registered substance (3-chloropropyl)triethoxysilane (CAS 5089-70-3), the maternal and foetal NOAELs were considered to be 300 mg/kg bw/day in rats (BSL, 2014).

An oral prenatal developmental toxicity study in a second species (rabbit) with the registered substance, (3-chloropropyl)triethoxysilane (CAS 5089-70-3), has been proposed and will be performed according to OECD Test Guideline 414 and in compliance with GLP, after approval by ECHA.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 May to 19 August 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study was conducted according to an appropriate guideline and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Crl:WI(Han)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Germany
- Age at study initiation: 11 to 12 weeks
- Weight at study initiation: 316 - 375 g males; 197 - 250 g females
- Fasting period before study: no
- Housing: individually in IVC cages, except during pre-mating and periods when 2 females or 2 females and 1 male in type III H, polysulphone cages
- Diet (ad libitum): Altromin 1324 maintenance diet
- Water (ad libitum): facility tap water
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 25
- Humidity (%): 45 - 65
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES:
From: 26 May 2014
To: not stated

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test item was weighed into a tared plastic vial on a precision balance.

The test item was dissolved in corn oil.

The vehicle was selected based on the test item’s characteristics and the testing guideline. The test item formulations were prepared once every ten days. Prepared test item formulations were stored in plastic falcon vials at room temperature until the day of administration procedure. The water content (if any) in the test item container was purged with liquid nitrogen after every use.

Homogeneity of the test item in the vehicle was maintained by vortexing the prepared solution thoroughly before every dose administration.

VEHICLE
- Concentration in vehicle: 25, 75 or 250 mg/mL
- Amount of vehicle: 4 mL/kg
- Lot/batch no.: MKBP7039V

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The assessment of homogeneity as well as a determination of the measured nominal concentration of the test item in the vehicle were was performed at various intervals.

Samples for analysis of the measured dose formulations of the test item in the vehicle (nominal concentration) were taken in the first and last week of the study for all doses (8 samples in total). Samples for homogeneity were taken from the top, middle and bottom of the high dose, medium dose and low dose preparation. Samples were taken in the first and last week of the study (18 samples in total). Samples for stability analysis were taken in the first week of the study, 0 hours after the preparation and another sample 10 days after the preparation (at room temperature), from high, medium, and low dose formulations (6 samples in total). Each sample was retained twice (sample A, sample B, each of at least 5 mL).

All formulation samples were stored at -15 to -35°C and the A samples were analysed after completion of the in-life phase of the toxicity study at BSL BIOSERVICE Scientific Laboratories GmbH. Samples were analysed by GC-FID.

Details on mating procedure:

- Impregnation procedure: cohoused
- M/F ratio per cage: 1/2
- Length of cohabitation: until positive evidence of mating
- Proof of pregnancy: sperm in vaginal smear (designated Gestation Day 0)

Duration of treatment / exposure:

Gestation Day 5 to Gestation Day 19

Frequency of treatment:

Once daily

No. of animals per sex per dose:

24 females per group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: little or no toxicity was expected with the test substance so the high dose was selected as 1000 mg/kg bw/day, corresponding to the limit dose. Doses of 100 and 300 mg/kg bw/day were selected to define a dose response.
- Rationale for animal assignment: random

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily (except weekends and public holidays when once daily)

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at least once daily

BODY WEIGHT: Yes
- Time schedule for examinations: Gestation Days 0, 5, 8, 11, 14, 17 and 20

FOOD CONSUMPTION: Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/period: Yes
- Time schedule for examinations: Gestation Days 0, 5, 8, 11, 14, 17 and 20

WATER CONSUMPTION: No
- Time schedule for examinations:

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day Gestation Day 20
- Organs examined: general macroscopic examination for structural abnormalities or pathological changes which may have influenced pregnancy.
- Organs weighed: liver

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Number of viable foetuses: Yes
- Position and number of foetuses in each uterine horn: Yes

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: half per litter

Statistics:

A statistical assessment of the results of the body weight, food consumption, prenatal parameters and litter weight data was performed by comparing values of dosed with control animals using a one-way ANOVA and a post-hoc Dunnett Test. Foetal evaluation parameters like external, visceral, craniofacial and skeletal parameters were analysed using a Fisher’s exact test. Litter incidence was the primary unit for the statistical analysis and interpretation. The statistics were performed with GraphPad Prism V.6.01 software (p<0.05 is considered as statistically significant).

Historical control data:

Historical control data from the Test Facility from 2010 to 2012 were provided.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Group mean body weight at 1000 mg/kg bw/day was slightly reduced compared to the control group with a maximal, statistically significant difference of 6% on gestation day 20. Body weight gain was also slightly lower in this group compared to the control group on various intervals within the study period and achieved statistical significance on gestation days 14-17.

A slightly, statistically significantly lower terminal body weight was observed in the 1000 mg/kg bw/day group when compared to the control group. The uterus weight in this group was also slightly but not statistically significantly lower than in the control group. This also resulted in a slightly lower adjusted maternal weight compared to the control females.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

In correlation to the body weight and body weight change, food consumption in the 1000 mg/kg bw/day group was noted to be slightly lower compared to the control group after the beginning of the treatment. Statistical significance was noted over the study period from gestation day 0 to day 20 as well as on several treatment intervals.

Description (incidence and severity):

The uterus weight in the 1000 mg/kg bw/day group was slightly but not statistically significantly lower than in the control group.

Dose descriptor:

NOAEL

Effect level:

300 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

A slightly but statistically significantly lower mean litter weight was observed in the 1000 mg/kg bw/day group, mean litter weight was marginally lower in the 300 mg/kg bw/day group but not statistically significant compared to the control group. Taking into account the marginally lower number of foetuses in the 1000 mg/kg bw/day group, a statistically significantly lower total litter weight of this group compared to control was noted. Consequently, statistically significantly lower male litter weight and a slightly lower female litter weight were also noted in the 1000 mg/kg bw/day group.

External malformations:

no effects observed

Description (incidence and severity):

No external abnormalities attributable to treatment were noted.

Skeletal malformations:

effects observed, treatment-related

Description (incidence and severity):

No craniofacial abnormalities attributable to treatment were noted. A statistically significant increase in litter incidences of incomplete ossification of interparietal bone, frontal bone, parietal bone, supraoccipital bone and zygomatic arch was observed in the 1000 mg/kg bw/day group when compared to the concurrent control group. For interparietal and frontal bones, incidences in this group were also higher compared to historical control data.

Furthermore, a statistically significant increase in unossified 4th sternebra was observed in the 1000 mg/kg bw/day group compared to the concurrent control group. Values were within the range of historical control data, but due to the clear dose-dependency this finding was considered related to the treatment with the test item. In each litter of the 1000 mg/kg bw/day group several foetuses were observed with unossified cervical vertebra centra. The incidence of this finding was statistically significant compared to the control group and was considered to be test item-related due to the dose-dependency. There was a higher, but not statistically significant, incidence of unossified xiphoid at 1000 mg/kg bw/day compared to the concurrent controls and historical control, which was considered to be test item-related. The observed reduced ossification of those bones that normally exhibit rapid ossification in the last days of gestation indicates a generalized skeletal delay in this group. This delayed ossification was considered to be associated with the observed maternal toxicity (lower body weight and food consumption) and reduced foetal body weight of the 1000 mg/kg bw/day group. Generally delayed ossification is not regarded to persist postnatally and not associated with long term consequences on survival, general growth and development and therefore not considered to be adverse.

There were a few findings of bent scapula body and of incompletely ossified 4th sacral arch which were only observed at 1000 mg/kg bw/day without statistical significance. Wavy ribs were seen in most litters of the 1000 mg/kg bw/day group showing a higher incidence than in the concurrent control group. Though this finding was not statistically significant, it can be considered treatment-related, as the incidence of this group was higher compared to historical control data.

No historical control data is available for the incompletely ossified 4th sacral arch or bent scapula findings, however, incomplete ossification of sacral arch is considered as variation. Wavy ribs are common findings in rodent studies and together with bent scapula are part of chondrodystrophy syndrome in rats (characteristic multiple skeletal abnormalities, such as bent and/or short bones) which has been demonstrated to be post-natally reversible (Carney and Kimmel (2007), De Schaepdrijver et al. (2014), Mitchard and Stewart) and therefore considered as variations and not adverse.

Visceral malformations:

no effects observed

Description (incidence and severity):

No visceral abnormalities attributable to treatment were noted.

Dose descriptor:

NOAEL

Effect level:

300 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: teratogenicity

Abnormalities:

not specified

Developmental effects observed:

not specified

Dose Formulation Analysis - tables to be added.

Table - Litter Data Summary

Group		Mean Litter Weight	Number of Males	Number of Females	Total No. of Foetuses	Total Litter Weight	Male Litter Weight	Female Litter Weight
Control	Mean	3.80	5.60	4.90	10.50	41.79	23.19	18.60
	SD	0.49	2.60	2.20	3.35	10.82	10.85	6.84
	N	19	20	20	20	19	19	19
100 mg/kg/day	Mean	3.81	4.20	5.50	9.70	38.50	16.84	21.66
	SD	0.70	1.99	2.16	2.89	8.02	6.53	7.93
	N	19	20	20	20	19	19	19
300 mg/kg/day	Mean	3.59	6.36	5.41	11.77	42.10	23.22	18.88
	SD	0.46	1.94	2.06	2.02	9.09	8.09	7.13
	N	22	22	22	22	22	22	22
1000 mg/kg/day	Mean	3.12***	4.76	4.71	9.48	29.62***	15.60*	14.02
	SD	0.39	2.57	2.22	3.28	10.50	8.66	6.48
	N	21	21	21	21	21	21	21
Asterisks indicate statistically significant differences to control group C, with* p<0.05, ** p<0.01 and *** p<0.001.

Table - Selected Foetal Skeletal Findings Summary

Skeletal Finding		Dose (mg/kg/day)
		Control	100	300	1000
Scapula body (B) bent	No of Incidences	0	0	0	3
	Total No of Observed Foetuses	109	101	135	103
	% Fetal incidence of Abnormality	0.00	0.00	0.00	2.91
	No of Litters with at least 1 incidence	0	0	0	2
	Total No of Observed Litters	19	19	22	21
	% Litter incidence of Abnormality	0.00	0.00	0.00	9.52
Scapula body (L) bent	No of Incidences	0	0	0	1
	Total No of Observed Foetuses	109	101	135	103
	% Fetal incidence of Abnormality	0.00	0.00	0.00	0.97
	No of Litters with at least 1 incidence	0	0	0	1
	Total No of Observed Litters	19	19	22	21
	% Litter incidence of Abnormality	0.00	0.00	0.00	4.76
Scapula body (R) bent	No of Incidences	0	0	0	3
	Total No of Observed Foetuses	109	101	135	103
	% Fetal incidence of Abnormality	0.00	0.00	0.00	2.91
	No of Litters with at least 1 incidence	0	0	0	3
	Total No of Observed Litters	19	19	22	21
	% Litter incidence of Abnormality	0.00	0.00	0.00	14.29

Asterisks indicate statistically significant differences to control group C, with* p<0.05, ** p<0.01 and *** p<0.001.

Conclusions:

Administration of (3-chloropropyl)triethoxysilane (CAS 5089-70-3; EC 225-805-6) at doses of 0, 100, 300 or 1000 mg/kg bw/day by oral gavage to pregnant female Wistar rats from gestation days 5 to 19 resulted in lower body weight, body weight gain and food consumption at 1000 mg/kg bw/day and were considered to be adverse. Lower terminal body weight, uterus weight and mean total litter weight were also noted at this dose.

Increased incidences of skeletal findings such as delayed ossification and lower litter weight recorded at 1000 mg/kg bw/day were considered to be attributable to the maternal effects and not adverse. An increased incidence of wavy ribs and bent scapula was also noted at this dose and these findings are recognised as part of chondrodystrophy syndrome in rats and have been demonstrated to be post-natally reversible and therefore also not adverse. However, the increased incidence of skeletal variations noted together with the lower litter weight was considered to be adverse at 1000 mg/kg bw/day.
Therefore the maternal and foetal No-Observed-Adverse-Effect-Levels (NOAEL) were both considered to be 300 mg/kg bw/day.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

300 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

In the key oral prenatal developmental toxicity study conducted according to OECD Test Guideline 414 and in compliance with GLP, administration of (3 -chloropropyl)triethoxysilane at doses of 0, 100, 300 or 1000 mg/kg bw/day by oral gavage to pregnant female Wistar rats from gestation days 5 to 19 resulted in lower body weight, body weight gain and food consumption at 1000 mg/kg bw/day and were considered to be adverse. Lower terminal body weight, uterus weight and mean total litter weight were also noted at this dose (BSL, 2014).

 

Increased incidences of skeletal findings such as delayed ossification and lower litter weight recorded at 1000 mg/kg bw/day were considered to be attributable to the maternal effects and not adverse. An increased incidence of wavy ribs and bent scapula was also noted at this dose and these findings are recognised as part of chondrodystrophy syndrome in rats and have been demonstrated to be post-natally reversible and therefore also not adverse (Carney and Kimmel, 2007; De Schaepdrijver et al., 2014, Mitchard and Stewart, 2014). However, the increased incidence of skeletal variations noted together with the lower litter weight was considered to be adverse at 1000 mg/kg bw/day. Therefore the maternal and foetal No-Observed-Adverse-Effect-Levels (NOAEL) were both considered to be 300 mg/kg bw/day.

In a supporting developmental screening study conducted by the inhalation route with read-across substance (3-chloropropyl) trimethoxysilane, no developmental effects were noted and the foetal No-Observed-Adverse-Effect-Concentration (NOAEC) was considered to be 813 mg/m³. Both the registered and read-across substances share a common hydrolysis product, (3-chloropropyl) silanetriol, with the other hydrolysis products being ethanol and methanol respectively. Since neither methanol nor ethanol would contribute to developmental toxicity effects in rodents at the dose levels tested, it is considered that any observed toxicological effects would be due to the action of the (3-chloropropyl) silyl moiety. Both substances have log K_ow in the range that is favourable for absorption across the respiratory tract (ethoxy log K_ow of 3.13 and methoxy log K_ow of 2.0). It is therefore considered valid to read-across the results for the trimethoxy analogue to provide additional screening developmental toxicity information (RCC, 2005).

An oral prenatal developmental toxicity study in a second species (rabbit) with the registered substance, (3-chloropropyl)triethoxysilane (CAS 5089-70-3), has been proposed and will be performed according to OECD Test Guideline 414 and in compliance with GLP, after approval by ECHA.

Carney EW, Kimmel CA. Interpretation of skeletal variations for human risk assessment: delayed ossification and wavy ribs. Birth Defects Research (Part B) 80 (2007) 473–96.

De Schaepdrjver L, Delille P, Geys H, Boehringer-Shahidi,Vanhove C. In vivo longitudinal micro-CT study of bent long bones rat offspring. Reproductive Toxicology 46 (2014) 91-97

Mitchard T, Stewart J. Reduced post-natal versus pre-natal incidence of bent long bones and scapulae in a preliminary investigation using the Han Wistar rat. Toxicology 45 (2014) 39-44

Justification for classification or non-classification

Based on the available data, 3-chloropropyltriethoxysilane (CAS 5089-70-3) does not require classification for reproductive or developmental toxicity according to Regulation (EC) 1272/2008.