Trichloro(propyl)silane

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

There are no oral, inhalation or dermal reproductive toxicity studies available for trichloro(propyl)silane. Data waivers are in place for this endpoint.

Limited data are available regarding the reproduction and development of animals following oral, dermal or inhalation exposure to hydrogen chloride or hydrochloric acid, however, protons and chloride ions both exist as normal constituents of body fluid in animals, hence low concentrations of hydrogen chloride appear not to cause adverse effects in animals. Therefore hydrochloric acid would not contribute to any reproductive toxicity (fertility or developmental) effects at the dose levels tested.

Link to relevant study records

Reference

Endpoint:

extended one-generation reproductive toxicity - basic test design (Cohorts 1A, and 1B without extension)

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Effects on developmental toxicity

Description of key information

In the key prenatal developmental toxicity study with the registered substance, trichloro(propyl)silane, conducted according to OECD Test Guideline 414 and in compliance with GLP, the NOAEL for maternal and developmental toxicity was concluded to be 50 mg/kg bw/day, the highest dose tested, based on the absence of statistically significant test-item related effects in maternal animals and foetuses (Bioservice, 2021).

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

In-life phase 13 October 2020 to 30 January 2021; Study completion 09 July 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

2018

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

Crl: WI(Han)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: e.g. Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: 11-12 weeks
- Weight at study initiation:
males: 330 - 400 g
(mean: 362.85 g, ± 20% = 290.28 – 435.43 g)
females: 194 - 259 g
(mean: 222.00 g, ± 20% = 177.60 – 266.40 g)
- Fasting period before study:
- Housing: Full barrier in an air-conditioned room, individually in IVCs (type III H, polysulphone cages) on Altromin saw fibre bedding (except during the pre-mating period when females were kept in groups of two animals and during mating period when two females were paired with one male). During the pre-mating period and after mating, males were housed in groups (up to 5 animals / cage) in type IV cages.
- Diet: ad libitum Altromin 1324 maintenance diet for rats and mice
- Water: ad libitum tap water (bottles provided), sulphur acidified to a pH of approximately 2.8 (drinking water, municipal residue control, microbiological controls at regular intervals)
- Acclimation period: at least five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3°C
- Humidity (%): 55 ± 10%
- Air changes (per hr): 10 per hour
- Photoperiod (hrs dark / hrs light): 12 hours light, 12 hours dark

Route of administration:

oral: gavage

Vehicle:

corn oil

Remarks:

dried and de-acidified corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The test item formulation was prepared freshly on each day of administration. The test item was diluted in dried and de-acidified corn oil. Dose volumes were adjusted individually based on weekly body weight measurements.

VEHICLE
- Justification for use and choice of vehicle (if other than water): in consultation with the sponsor based on the test item’s characteristics.
- Concentration in vehicle: 0, 6.25, 12.5, 25 mg/mL
- Amount of vehicle (if gavage): 4 mL/kg bw
- Lot/batch no. (if required): MKCK6411

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Before beginning of the treatment period, formulation samples were prepared and analysed in order to obtain knowledge about stability and homogeneity of the test item in the selected vehicle. The test item formulations were stable for up to 12 days at room temperature. Prestart homogeneity investigation was included on the samples collected from various levels (top, middle and bottom) of high dose and low dose groups. As the test item was shown to be homogenous after 30 min without stirring samples were not collected during the study for the investigation of homogeneity. Samples were taken for substance concentration in the first and last week of the study for all doses.

Details on mating procedure:

- Impregnation procedure: cohoused
- M/F ratio per cage: 1:2 male:female
- Length of cohabitation: no information
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

from gestation day (GD) 5 to gestation day (GD) 19

Frequency of treatment:

Daily

Duration of test:

20 days

Dose / conc.:

0 mg/kg bw/day (actual dose received)

Remarks:

control group

Dose / conc.:

10 mg/kg bw/day (actual dose received)

Remarks:

low dose (LD)

Dose / conc.:

25 mg/kg bw/day (actual dose received)

Remarks:

medium dose (MD)

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Remarks:

high dose (HD)

No. of animals per sex per dose:

138 animals (46 males and 92 females)

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on dose range-finding study
- Rationale for animal assignment (if not random): animals were weighed and assigned to experimental groups to acheive the most homogeneous variation in body weight throughout groups of males and females (randomisation performed with IDBS workbook)

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: morbidity and mortality: twice daily (except evenings and weekends when observed once).

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: General clinical observations at least once a day
- Clinical observations include spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoea, asphyxia, vocalisation, diarrhoea, changes in the skin and fur, eyes and mucous membranes (salivation, discharge), piloerection and pupil size. Changes in gait, posture, response to handling as well as the presence of clonic or tonic movements, stereotypes or bizarre behaviour were recorded.

BODY WEIGHT: Yes
- Time schedule for examinations: All animals were weighed once before initiation of pairing to ensure that the body weights were within ±20% variation. The sperm-positive females were weighed on GDs 0, 5, 8, 11, 14, 17 and 20. Males were not weighed in this study except once before initiation of pairing.

FOOD CONSUMPTION: Yes
- Food consumption of sperm-positive females was determined for the following intervals: GDs 0-5, 5-8, 8-11, 11-14, 14-17 and 17-20. Food consumption was not measured for males during the entire study or for both males and females during the mating period.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #20
- Organs examined: See Table 1 below

OTHER: Thyroid hormones
- Blood samples were collected prior to sacrifice for thyroid hormone (T3, T4, TSH) analysis.

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
- Alive and dead fetuses: 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, at least 20 litters per group

Statistics:

statistical assessment of the results of the body weight and food consumption was performed by comparing values of dosed animals with control animals using a one-way ANOVA and a post-hoc Dunnett Test. Results of absolute and relative organ weights, thyroid hormones and foetal evaluation parameters like external, visceral, craniofacial and skeletal parameters were statistically analysed by comparing values of dosed with control animals using either a parametric one-way ANOVA and a posthoc Dunnett Test or a non-parametric Kruskal-Wallis Test and a post-hoc Dunn’s Test, based on the results of homogeneity and normality tests. The statistics were performed with GraphPad Prism V.6.01 software or Ascentos 1.3.4 software (p<0.05 is considered as statistically significant).

Historical control data:

See attached historical control data tables.

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

There were no relevant test item-related clinical signs observed in any of the treated groups. None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice.
Clinical signs observed occasionally during the treatment period of the study included skin and fur, hairless area in one control and one LD group rat (nos. 5, 28, respectively) on GDs 18-19 at thorax; one MD group rat (no. 62) on GDs 17-20 at both forelimbs and pale discoloured faeces was observed in one MD group rat (no. 66) on GDs 16-19. All these findings are considered to be incidental findings.
One MD group rat (no. 69) on GD 19 showed moderate salivation and moving the bedding materials. Moving the bedding was observed immediately after dosing in HD groups in animal nos.74, 76, 78, 81 on GD19; animal no. 84 on GDs 16-19, animal no. 85 on GDs 16-18, animal no. 86 on GD 17, animal no. 87 on GDs 17, 19; animal no. 88 on GD 12, animal no. 89 on GDs 12, 14; animal no. 90 on GDs 12-13, 18-19 and animal no. 91 on GDs 11-13 and 18. Slight salivation was observed in HD group animal nos. 75, 78, 87, 88, 90 on GDs 18, 19, 17-19, 12-15 and 18-19 respectively. Moderate salivation was observed in HD group animal nos. 85 and 86 on GDs 16-19 and 17, respectively. Slight to moderate salivation and moving the bedding materials are considered to be a local reaction to the treatment with test item. These clinical signs were observed on a few days of the treatment period immediately after dosing.

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

No statistically significant differences in the absolute and relative (to body weight) thyroid/parathyroid weights of the treated groups when compared to the control.

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

At histopathologic evaluation, degenerative and inflammatory lesions related to the direct irritative effect of the test item were observed in the stomach of HD group animals and consisted of forestomach and glandular stomach ulcerations, forestomach erosions, squamous hyperplasia, forestomach submucosal oedema hyperkeratosis and mixed cell infiltrates (i.e. inflammation). Further, mural necrosis and intramural haemorrhages were also observed in a few animals. These effects are considered to be a result of the direct irritative effect of the test item on the gastric mucosa.

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

No test item related histopathological findings were observed in thyroid glands and parathyroid of all females.

Other effects:

no effects observed

Description (incidence and severity):

Thyroid hormones: no statistically significant or toxicologically relevant effects were observed on group mean T3, T4 and TSH hormone levels and values were comparable to the control.

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Description (incidence and severity):

No dead fetuses were observed in any treatment group.

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

no effects observed

Key result

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: no adverse systemic effects were observed.

Abnormalities:

no effects observed

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Description (incidence and severity):

No statistically significant or dose-dependent effects were observed.

Visceral malformations:

no effects observed

Other effects:

no effects observed

Description (incidence and severity):

The absolute and relative anogenital distance (AGD) in male and female foetuses and testicular descent in males were unaffected by treatment.

Key result

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects observed

Abnormalities:

no effects observed

Developmental effects observed:

no

See attached tables of results.

Conclusions:

In the prenatal developmental toxicity study, conducted according to OECD Test Guideline 414 and in compliance with GLP, the NOAEL for maternal and developmental toxicity in rats was concluded to be 50 mg/kg bw/day based on the absence of adverse effects in the high dose group.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

50 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

Summary method

In the key prenatal developmental toxicity study with the registered substance, trichloro(propyl)silane, conducted according to OECD Test Guideline 414 and in compliance with GLP, the test substance was administered daily via oral (gavage) to groups of 23 pregnant female Wistar rats during gestation days (GDs) 5 to 19 at doses of 0 (control), 10 (LD), 25 (MD) and 50 (HD) mg/kg bw/day in dried and de-acidified corn oil (Bioservice, 2021). The dose levels in the study were selected in consultation with the sponsor and based on a dose range finding study (Bioservice, 2019), reported in Section 7.5.1. The highest dose level was chosen with the aim of inducing toxic effects, but not death or severe suffering. In the 14-day dose range-finding study, male and female Wistar rats were treated with the test item trichloro(propyl)silane at dose levels of 50, 100, 175, 250 and 500 mg/kg bw/day. All animals in the highest does died, the cause of death was considered to be inflammatory lesions of the stomach. Clinical signs were observed at 500 mg/kg bw/day. No mortality or marked clinical signs were observed at lower doses. Test item-related gross lesions were noted in the gastrointestinal organs at ≥ 175 mg/kg bw/day and these were evident during histopathological examination. At the microscopic examination, specific findings were found, starting at the dose of 50 mg/kg bw/day. Based on the results of the dose range finding study the highest dose is expected to cause some irritation and probably inflammation in the gastrointestinal tract at a level that does not lead to severe distress and suffering of the animals. Thereafter, a descending sequence of dose levels was selected with a view to demonstrate any dose-related response and a NOAEL.

During the period of administration, the animals were observed each day for signs of toxicity and mortality. All female animals were sacrificed on their respective GD 20. Following the gross necropsy, the uteri with cervix and ovaries were removed. Each uterus was weighed and examined for number of implantations, resorptions (early and late), and alive and dead foetuses. Foetuses were identified by colour strings, sexed and weighed. All foetuses were observed for external abnormalities, half of the foetuses for visceral and craniofacial abnormalities and the remaining half of the litter were observed for skeletal abnormalities. The uteri of the non-pregnant females were processed with 10% ammonium sulphide solution and checked for the early embryonic deaths.

The sperm-positive females were weighed on GDs 0, 5, 8, 11, 14, 17 and 20. Food consumption of sperm-positive females was measured on GDs 5, 8, 11, 14, 17 and 20.

Thyroid/parathyroid glands from all dams were preserved. The weight of thyroid/parathyroid glands was measured after fixation. Blood samples were assessed for serum levels of thyroid hormones.

A full histopathology was carried out on the preserved thyroid/parathyroid glands and specified organs. All foetuses were assessed for external abnormalities. One half of each litter was examined for soft tissue anomalies by a microdissection technique. The remaining foetuses were processed by Alizarin red staining and the first 20 litters per group were examined for skeletal alterations. Craniofacial examination of the heads of the foetuses used for the soft tissue examination of at least 20 litters per group was performed for internal structure including the eyes, brain, nasal passage and tongue by razor blade serial sectioning technique.

In addition, special attention was given to the gastrointestinal tract in order to assess possible corrosive effects of the test item. All these organs (head with paranasal sinuses, oral cavity (pharynx), oesophagus, stomach and intestine) were observed for macroscopic findings and collected for histopathological evaluation. Histopathological analysis was done for these tissues collected from control and HD treated groups. As suggested by the sponsor, no further histopathology analysis was done with lower dose levels.

Summary results, maternal findings

No test item-related mortality was observed during the study and all animals survived until the end of the study.

There were no test item-related or adverse clinical signs of toxicological relevance observed in any of the treatment groups. None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice.

The mean body weight and mean body weight gain remained unaffected and increased with progress of the study in all treatment and control groups. No test item-related effect was observed in food consumption in all the treatment groups when compared to control.

Successful mating resulted in 21/23 pregnancies in the LD group, 22/23 in the MD group and 22/23 in the HD group compared to 21/23 pregnancies in the control group. No test item-related effects of toxicological relevance were noted for any prenatal parameters including terminal body weight, adjusted maternal weight (carcass weight), net weight change from GD 0, uterine weight, number of corpora lutea, implantation sites, early and late resorptions, pre- and post-implantation loss, number of live foetuses, number of male and female foetuses and sex ratios in treatment groups when compared to the control group. No dead foetuses were noted in any of the groups.

No test item-related gross pathological changes were observed during the macroscopic examination in any of the females examined.

No statistically significant or test item-related effects were observed on group mean T3, T4 and TSH hormone levels and values were comparable to the control group.

No statistically significant differences in the absolute and relative (to body weight) thyroid/parathyroid weights were observed in the treated groups when compared to the control.

At histopathologic evaluation, degenerative and inflammatory lesions related to the direct irritative effect of the test item were observed in the stomach of HD group animals and consisted of forestomach and glandular stomach ulcerations, forestomach erosions, squamous hyperplasia, forestomach submucosal oedema hyperkeratosis and mixed cell infiltrates (i.e. inflammation). Further, mural necrosis and intramural haemorrhages were also observed in a few animals.

No test item-related histopathological findings were observed in thyroid glands and parathyroid of all females.

Summary results, foetal findings

In male and female foetuses, the cube root of foetal body weight in treatment groups remained unaffected and no statistical significance was observed in any of the treatment groups when compared to the control.

In male and female foetuses, the absolute and relative anogenital distance (AGD) in treatment groups remained unaffected and no statistical significance was observed in any of the treatment groups when compared to the control. All male foetuses from all groups showed completion of testicular descent (abdominal).

No test item-related and statistically significant effects on mean foetal weight, male and female foetal weight on a per litter basis (group mean of individual litter mean) were observed in any of the treated groups when compared to the control group.

There were no test item-related external abnormalities observed in any of the treated groups.

Internal observation of the foetal viscera by free hand microdissection technique revealed a range of visceral findings in treated groups and the control. Visceral findings observed in the treated groups were at frequencies generally comparable to or in some cases slightly higher or lower in frequency compared to controls. As the observed findings were either minor variations and/or lacking dose dependency and consistency, no toxicological significance can be attributed to these findings and they were considered to be spontaneous in nature. All litter incidences from treated groups were well within the historical control data range and statistically insignificant when compared to the control group.

Craniofacial examination by razor blade serial sectioning technique revealed a finding of head, subcutaneous hematoma (general) in the LD group (23.8%) when compared to control group (20%) and a finding of head, subcutaneous space in the MD group (13.6%) when compared to control group (0%). Midbrain, haematoma, subdural in MD and HD groups (18.2% and 23.8% respectively) were observed when compared to control (25%). These findings were considered to be spontaneous in nature and not related to the treatment with the test item. Statistical analysis of the data revealed no statistical significance for any of these findings. In addition, all values were within the historical control range for this strain.

Skeletal examination and examination of cartilage of the Alizarin red and Alcian blue stained foetuses revealed a range of findings in all groups including control.

At gestation day 20, incomplete ossification was seen in several bones of litters in all treated groups and the control. Mostly, bones of the skull, sternum, paws, limbs and vertebra were affected by variations in the status of expected ossification, described in terms of incomplete ossification, irregular ossification, unossified or increased ossification throughout all experimental groups. However, there were no dose dependency and no trend towards a treatment-related incomplete ossification of bones observed. Statistical analysis did not reveal any significance; except slight but statistically significantly lower foetal incidences of rudimentary 7th cervical rib were observed in LD, MD and HD groups (0%) when compared to control (4.17%).

Observed ossification-related findings were observed at lower or higher incidences and without dose dependency and thus were not considered as toxicologically relevant.

There were also slightly higher or lower litter incidences of skeletal findings in the LD and MD groups, but they did not show any statistical significance or dose dependency.

Conclusion

On the basis of this prenatal developmental toxicity study with pregnant female Wistar rats dosed with trichloro(propyl)silane at levels of 10, 25, and 50 mg/kg bw/day the following conclusions can be made:

No test item-related mortality and no test item-related adverse clinical signs were observed in any of the treated animals during the study period.

No test item-related effects on mean body weight gain and food consumption were observed in any of the treated animals during the study.

No test item-related effects were observed on prenatal parameters including terminal body weight, adjusted maternal weight (carcass weight), net weight change from GD 0, uterine weight, number of corpora lutea, implantation sites, early and late resorptions, percent pre- and post-implantation loss, number of live foetuses, anogenital distance (AGD), foetal weight, number of male and female foetuses, sex ratio and testicular descent in treatment groups when compared to the control.

No statistically significant or toxicologically relevant effect was observed on group mean T3, T4 and TSH hormone levels and thyroid/parathyroid weights from all dams. No gross or histopathological lesions were observed in thyroid glands. No test item-related macroscopic findings were observed in this study.

Furthermore, no test item-related and toxicologically relevant external, visceral, craniofacial and skeletal findings were observed in the treatment groups.

Therefore, a NOAEL for maternal and foetal toxicity could be established at 50 mg/kg bw/day. The NOAEL for the direct irritative effect of the test item on the gastric mucosa could not be established.

Justification for classification or non-classification

The available data indicate that trichloro(propyl)silane does not need to be classified for toxicity to reproduction (fertility or developmental toxicity) according to Regulation (EC) No 1272/2008.