Trichloro(hexadecyl)silane

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

According to Regulation (EC) No 1907/2006, Annex IX, 8.7.3. column 1, an extended one-generation study for the assessment of reproductive toxicity is required if the available repeated dose toxicity studies indicate adverse effects on reproductive organs or tissues or reveal other concerns in relation with reproductive toxicity. A 90-day repeated dose toxicity study with special emphasis on the male and female reproductive tissues is available for trichloro(hexadecyl)silane. There was no effect on epididymal sperm motility and testicular sperm count at the end of the treatment and recovery period. Sperm staging did not reveal any indication of toxicity. The registered substance had no effect on oestrous cycle, nor were any other effects observed on male and female reproductive organs. Thus, no extended one-generation reproductive toxicity with trichloro(hexadecyl)silane is required.

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:

the extended one-generation reproductive toxicity study does not need to be conducted because there are no results from available repeated dose toxicity studies that indicate adverse effects on reproductive organs or tissues, or reveal other concerns in relation with reproductive toxicity

Reason / purpose for cross-reference:

data waiving: supporting information

Reproductive effects observed:

not specified

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

Prenatal developmental toxicity study (OECD 414, GLP), rat:

NOAEL developmental toxicity >= 250 mg/kg bw/day (highest dose level tested)

NOAEL maternal toxicity = 100 mg/kg bw/day

NOAEL local < 250 mg/kg bw/day

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Dec 2020 - 09 Mar 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:

25 June 2018

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

rat

Strain:

other: Wistar rats, Crl: WI(Han)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Sulzfeld, Germany
- Age at study initiation: females: 11-12 weeks on arrival at the test facility; males: 12-13 weeks at the start of pairing
- Weight at study initiation: 339 – 398 g (males); 199 – 256 g (females)
- Housing: the animals were kept individually in IVC cages (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). The pregnant females were provided with nesting material towards the end of the pregnancy (e.g. at GD 18)
- Diet: Altromin 1324 maintenance diet for rats and mice (Altromin Spezialfutter GmbH & Co. KG, Lage, Germany), ad libitum
- Water: tap water, sulphur acidified to a pH of approximately 2.8 (drinking water, municipal residue control, microbiological controls at regular intervals), ad libitum
- Acclimation period: at least five days under laboratory conditions

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

Route of administration:

oral: gavage

Vehicle:

paraffin oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Based on the results of stability testing, the test item formulations were prepared within the stability time frame of 3 days as given by Eurofins Munich Study No. STUGC20AA2272-1. The test item was weighed into a tared glass vial on a suitable precision balance and the vehicle was added to give the appropriate final concentration of the test item. The formulation was vortexed and/or stirred until visual homogeneity was achieved. During all steps of sample preparation, the formulation samples were overlaid with argon to prevent instability caused by repeated contact of the test item formulation with air. The prepared formulation was stored protected from light and at room temperature. The formulations were kept under magnetic stirring during the daily administration.

VEHICLE
- Justification for use and choice of vehicle: the vehicle was selected based on the test item’s characteristics.
- Concentration in vehicle: 10, 25 and 62.5 mg/mL
- Amount of vehicle: 4 mL/kg bw/day
- Lot/batch no.: 0000855509, 0001849607, 0001929619

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analysis of test item formulations was performed at the Analytical Department of the Test Facility using a validated GC-FID (Gas Chromatography – Flame Ionization Detector) method.
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 as part of a separate GLP study.
Study pre-start stability analysis was included on the samples from HD and LD groups and the investigation was made for 0 h, 4 h at room temperature (RT), 3 days (RT), 3 days (2-8 °C) and 3 days -15 to -35 °C.
Pre-start homogeneity investigation was included on the samples collected from various levels (top, middle and bottom) of HD and LD groups. As the test item formulation was shown to be homogenous (after 30 min without stirring), samples were not collected during the study for the investigation of homogeneity and samples were only taken for substance concentration in the first and in the last week of the study for all doses (8 samples in total).
Each sample taken during the study was retained in duplicate (sample A, sample B, each of at least 3 mL). The A-samples were analysed and until then stored under appropriate conditions based on available stability data. The B-samples are retained at below -15 °C and discarded after completion of the final study report.
Concentration analysis of formulation samples was determined at three concentrations (10 mg/mL, 25 mg/mL and 62.5 mg/mL). The mean recoveries observed for the LD group were between 86.5% and 99.4% of the nominal value, between 91.6% and 101.1% of the nominal value for the MD group and between 97.4% and 100.0% of the nominal value for HD group. The mean recoveries observed in the LD, MD and HD groups were 93.0%, 96.3%, and 98.7% of the nominal concentration, respectively.
Nominal concentrations were confirmed for all dose groups, as measured concentrations were within acceptance criterion of 15%.
On 14 January 2021, 6 animals of the MD group {animal no. 53-54 (GD19), animal no. 55-56 (GD13) and animal no. 57-58 (GD12)} and 6 animals of the HD group {animal no. 76-77 (GD19), animal no. 78-79 (GD13) and animal no. 80-81 (GD12)} were treated with a dose lower (about half of the concentrations; approx. 13 and 31 mg/ml respectively) than the respective targeted concentration due to human error in weighing the test item by mistake.

Details on mating procedure:

- Impregnation procedure: cohoused
- M/F ratio per cage: 1/2
- Length of cohabitation: until evidence of copulation was observed
- 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:

Day 5-19 of gestation (1 day prior to caesarean section)

Frequency of treatment:

daily, 7 days/week

Dose / conc.:

40 mg/kg bw/day

Dose / conc.:

100 mg/kg bw/day

Dose / conc.:

250 mg/kg bw/day

No. of animals per sex per dose:

23

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
In the dose range finding study, male and female Wistar rats were treated with the test substance at dose levels of 40, 80, 120, 200 and 300 mg/kg bw/day over a period of 14 days. There was no test item-related effect observed on mortality, clinical signs, body weight, food consumption or haematology. At necropsy, an abnormally coloured jejunum and ileum was found in one male dosed with 200 mg/kg bw/day. The thymus was enlarged in both males dosed with 200 mg/kg bw/day and in both females each dosed with 200 mg/kg bw/day or 300 mg/kg bw/day. In one male dosed with 300 mg/kg bw/day, grey foci in the stomach fundic region were observed correlating with inflammatory lesions found in the histopathological examination. Histologically, test item-related findings consisted of inflammatory and degenerative lesions in the stomach including squamous cell hyperplasia in the forestomach in one male at 120 mg/kg bw/day and in both sexes at all higher doses. The finding was associated with forestomach submucosa inflammation (both males and one female), inflammation of the muscularis of the glandular stomach (one male only) and forestomach ulceration (one male only) at 300 mg/kg bw/day.
The highest dose level for the main study was chosen with the aim of inducing toxic effects, but not death or severe suffering including severe effects like ulceration and necrosis. Thereafter, a descending sequence of dose levels is selected with a view to demonstrate any dose-related response and a NOAEL.
- Fasting period before blood sampling for (rat) dam thyroid hormones: no

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: general clinical observations were made at least once a day, preferably at the same time each day. Twice daily all animals were observed for morbidity and mortality except on weekends and public holidays when observations were made once daily.
- Cage side observations included 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, difficult or prolonged parturition or bizarre behaviour were recorded.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: prior to the start of the mating, a detailed clinical observation was made outside the home cage.

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 GD 0, 5, 8, 11, 14, 17 and 20.

FOOD CONSUMPTION: Yes
- Food consumption of sperm-positive females was determined for the following intervals: GD 0-5, 5-8, 8-11, 11-14, 14-17 and 17-20.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on GD 20
- Organs examined: each dam was examined macroscopically for any structural abnormalities or pathological changes which may have influenced the pregnancy. Any macroscopic findings were preserved in 4% neutral-buffered formaldehyde.
- Thyroid/parathyroid glands from all dams were preserved in 4% neutral-buffered formaldehyde. The weight of thyroid/parathyroid glands was measured after 24 hours fixation.
- Special attention was paid to gastrointestinal tract in order to examine corrosiveness of the test item.
- All organs listed in Table 1 from all dams underwent a detailed macroscopic observation. The organs were then preserved in 4% neutral-buffered formaldehyde for possible histopathological examination. For animals of control and HD groups, the organs listed in Table 1 were histopathologically analysed.

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
- Other: uteri that appeared non-gravid were further examined by staining with 10% ammonium sulphide solution to confirm the non-pregnant status.

Blood sampling:

- Serum: Yes, thyroid hormone levels from samples from all dams were assessed at the end of treatment prior to or as part of the sacrifice of the animals. At termination, blood samples were collected from the abdominal aorta in serum separator tubes and the serum obtained was stored under appropriate conditions. Serum samples were assessed for thyroid hormone levels (T3, T4, TSH) using ELISA.

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
- Anogenital distance of all live rodent pups: Yes

Statistics:

A 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).

Indices:

Preimplantation Loss = Corpora Lutea - Implantation Sites
Postimplantation Loss = Early / Late Resorptions + Dead Fetuses
Relative Anogenital Distance (AGD) = AGD / Cube Root of Foetus Weight

Historical control data:

Historical control data from studies conducted in-house were provided (see Attachments) and referred to in order to allow comparison with concurrent controls.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

In the control group, few incidental findings of hairless area in both forelimbs were observed in animal no. 13 and 17 on GD 10-20 and GD 18-20 respectively, including thorax in animal no. 13 on GD 17-20.
In the LD group, animal no. 24 showed crust on right neck side on GDs 7-20. Animal no. 42 showed hairless area, head on GDs 9-15 and animal no. 36 was found dead on GD 11.
In the MD group, moving the bedding was observed in 9/23 female immediately after dosing during the treatment days; this was considered to be local reaction to the test item after gavaging. Animal no. 56 showed salivation (moderate) on GD 18-19. Animal no. 60 showed light salivation on GD 8 and moderate salivation on GD 6-7 and crust on upper back region on GD 6-14. Animal no. 64 showed slight piloerection on GD 18-19. Animal No. 65 showed slight salivation on GD 16-17, slight spontaneous reduced activity and abnormal breathing on GD 17 and slight piloerection on GD 18. Other animals in the MD group (12/23) were found to be normal during the study period.
In the HD group, moving the bedding was observed in 9/23 female immediately after dosing during the treatment days; this was considered to be local reaction to test item after gavaging. Animal no. 78 (moribund sacrificed on GD 17) showed salivation (severe), piloerection (severe), both eyelid closed, abnormal breathing and nasal discharged on GD 17. Animal no. 80 showed salivation (severe) abnormal breathing and hunched posture on GD 17 and slight salivation on GDs 18-19. Animal no. 81 showed hairless area on both forelimbs on GD 10-20. Animal no. 86 showed signs of abortion on GD 13 but was found normal on GDs 14-20. Slight salivation was observed in animal no. 88, 89 and 91 on GDs 16-17, GD 19 and GDs 17-20 respectively. Other animals in the HD group (12/23) were found to be normal during the study period.
Clinical signs of salivations, piloerection, reduced spontaneous activity, hunched posture, eyelid closure, nasal discharge and abnormal breathing observed in MD and HD groups starting between GDs 6 and 20 were considered to be treatment related and caused by local irritation effects immediately after dosing.

Dermal irritation (if dermal study):

not examined

Description (incidence and severity):

Not applicable

Mortality:

mortality observed, treatment-related

Description (incidence):

One LD group animal (no. 36) was found dead on GD 11 and one HD group animal (no. 78) was euthanized on GD17 for animal welfare reasons.
In animal no. 78 (HD group), at necropsy stomach with red coloured cardiac region and creamy consistency and spotted thymus were observed. The cause of morbidity was related to the presence of forestomach erosion accompanied by forestomach submucosal oedema, squamous hyperplasia hyperkeratosis and mixed cell infiltrates.
In animal no. 36 (LD group), no clinical signs were observed prior to GD 11. At macroscopic observation, lungs were spotted (abnormal colour), fluid filled and failed to collapse. The cause of the mortality was assumed to be due to aspiration of the test item formulation or gavage error.
All other animals survived their scheduled treatment period.

Body weight and weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

Mean body weight was increased with the progress of the study in the control and all the treated groups throughout the study period. No statistical significance was observed in mean body weight.
There was a slight decrease in mean body weight gain observed on GDs 8-11 in MD (35.62%) and HD (10.50%) groups and an increase in mean body weight gain was observed on GDs 11-14 in all the dose groups (55.32% with statistical significance in LD, 13.77% in MD and 30.77% in HD groups) and on GDs 5-8 in MD (80.92%) and HD (13.58%) groups when compared to control. The increase in mean body weight gain could be due to slightly reduced weight gain in the control group. Overall, there were no test item-related effects on mean body weight gain observed on GDs 5-20.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Mean food consumption observed during GDs 5-20 in the treated groups was comparable to control; no statistical significance or test item related effects were observed in treated groups when compared to control.

Food efficiency:

not examined

Description (incidence and severity):

Not applicable

Water consumption and compound intake (if drinking water study):

not examined

Description (incidence and severity):

Not applicable

Ophthalmological findings:

not examined

Description (incidence and severity):

Not applicable

Haematological findings:

not examined

Description (incidence and severity):

Not applicable

Clinical biochemistry findings:

not examined

Description (incidence and severity):

Not applicable

Endocrine findings:

not specified

Description (incidence and severity):

The following ED-related parameters were investigated in the study: T3, T4 and TSH level dams, anogenital distance, genital abnormalities (testicular descent/cryptorchidism), thyroid histopathology dams, thyroid weight dams, gravid uterus weight, litter size, litter/foetus weight, number of implantations, corpora lutea, number of embryonic or fetal deaths and viable foetuses, post-implantation loss, pre-implantation loss, presence of anomalies (external, visceral, skeletal) and sex ratio. For details, please refer to the respective result fields and the endpoint summary.

Urinalysis findings:

not examined

Description (incidence and severity):

Not applicable

Behaviour (functional findings):

not examined

Description (incidence and severity):

Not applicable

Immunological findings:

not examined

Description (incidence and severity):

Not applicable

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Statistical analysis of post-fixed thyroid/parathyroid weights from all dams revealed 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:

effects observed, treatment-related

Description (incidence and severity):

Forestomach mucosa with multiple crater shaped indentations were observed in HD animal nos. 79, 80, and 91 and were most likely induced by test item irritation in the stomach.
A dark coloured thymus and peritoneal herniation at middle was observed in HD animal no. 72. An enlarged lumbar lymph node was observed in HD animal no. 86. A trachea filled with blood was observed in HD animal no. 92. One control animal (no. 19) had a red colored cardiac region, stomach. These gross findings were considered as incidental.

Neuropathological findings:

not examined

Description (incidence and severity):

Not applicable

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Degenerative and inflammatory lesions were observed in the stomach of both the decedent HD group animal no. 78 and the surviving animals from the HD group and consisted of forestomach ulcerations, forestomach erosions, squamous hyperplasia, forestomach submucosal oedema, hyperkeratosis and mixed cell infiltrates. In addition, in the stomach of HD group animal no. 83, apart from the above mentioned forestomach changes, oedema and mixed cell infiltrates were present in the submucosa of the glandular stomach. Further, in the control group squamous hyperplasia and hyperkeratosis, both of low severity, were observed at the limiting ridge. The gastric changes observed in control animals were considered incidental.
In the oesophagus of one HD group animal (no. 88) and one control animal (no. 6) mixed cell infiltrates (i.e. inflammation) were observed in the connective tissue surrounding the oesophagus. The change was considered incidental and most likely represents a traumatic injury (gavage error). In the lungs of some animals from the control and HD groups, granulomas and mixed cell infiltrates were observed. In one HD group animal (no. 84), the moderate mixed inflammatory changes affected the normal lung architecture and were accompanied by the intralesional presence of large macrophages with foamy cytoplasm. All lung changes mentioned were considered to be related to aspiration of small portions of the bolus and / or were induced by inflammatory processes most likely not related to the systemic test item action.
In the thyroid and parathyroid glands from females of all the groups, there were no histology changes that could be related to the treatment with the test item.
All other microscopic findings recorded during the histopathology evaluation were within the range of normal background lesions which may be recorded in this study type and animals of this strain and age.

Histopathological findings: neoplastic:

not examined

Description (incidence and severity):

Not applicable

Other effects:

effects observed, non-treatment-related

Description (incidence and severity):

In all terminally sacrificed females, 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, except for a statistically significant increase in mean TSH in the MD group; but without dose dependency. Hence, this was not considered to be test item related.

Number of abortions:

no effects observed

Description (incidence and severity):

No test item-related effects were observed. Animal no. 86 showed signs of abortion on GD 13 but was found to be normal on GDs 14-20.

Pre- and post-implantation loss:

no effects observed

Description (incidence and severity):

No test item-related effects were observed.

Total litter losses by resorption:

no effects observed

Description (incidence and severity):

No test item-related effects were observed.

Early or late resorptions:

no effects observed

Description (incidence and severity):

No test item-related effects were observed.

Dead fetuses:

no effects observed

Description (incidence and severity):

No test item-related effects were observed.

Changes in pregnancy duration:

not examined

Description (incidence and severity):

Not applicable

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

Successful mating resulted in 18/23 pregnancies in the LD group, 21/23 in the MD group and 21/23 in the HD group compared to 23/23 pregnancies in the control group.

Other effects:

no effects observed

Description (incidence and severity):

No test item-related effects were observed for terminal body weight, adjusted maternal weight (carcass weight), uterine weight and number of corpora lutea.

Details on maternal toxic effects:

A local NOAEL in relation to direct irritative effect of the test item on the gastric mucosa could not be established, as the LD and MD animals were not evaluated histopathologically.

Dose descriptor:

NOAEL

Remarks:

maternal

Effect level:

100 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

mortality

Dose descriptor:

NOAEL

Remarks:

local

Effect level:

< 250 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

clinical signs

gross pathology

histopathology: non-neoplastic

Abnormalities:

no effects observed

Fetal body weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

No statistical significance was observed in any of the treated groups when compared to control, except a slight but statistically significant increase in male and female mean cube root of fetuses weight in MD group and a slight but statistically significant decrease in male mean cube root of fetuses weight in HD group were observed. All these values are within the historical control range for this strain and therefore considered incidental.

Reduction in number of live offspring:

no effects observed

Description (incidence and severity):

No test item-related effects were observed.

Changes in sex ratio:

no effects observed

Description (incidence and severity):

No test item-related effects were observed.

Changes in litter size and weights:

effects observed, non-treatment-related

Description (incidence and severity):

No test item related effects on litter size were observed.
The mean male and female foetal weights observed on an individual basis (sum of weight of all foetuses in group divided by total number of foetuses in respective group) in the LD, MD and HD groups were comparable to control; however, statistically significant changes were observed in the LD and MD group male foetuses (3.47% and 5.21% respectively, above control) and in female foetuses of MD group (4.75% above control) when compared to control. This was considered to be incidental as it was without dose dependency and these values were within the historical control range in this strain.
No test item-related and statistically significant effects in 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.

Anogenital distance of all rodent fetuses:

no effects observed

Description (incidence and severity):

In males and female foetuses, the absolute and relative anogenital distance (AGD) in treatment groups remained unaffected when compared to the control group.

Changes in postnatal survival:

no effects observed

Description (incidence and severity):

No test item-related effects were observed.

External malformations:

effects observed, non-treatment-related

Description (incidence and severity):

There were no test item-related external abnormalities observed in any of the foetuses of test item treated groups. A single incidence of umbilical hernia was observed in one foetus of the LD group, this was considered to be an incidental finding.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

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 was no dose-dependency and no trend towards a treatment-related incomplete ossification of bones observed. Statistical analysis did not reveal any significance; except for slight but statistically significantly lower foetal incidences of skull parietal incomplete ossifications observed in the LD group (11.41%) when compared to control (33.86%). This was considered to be incidental in nature and not test item-related effects.
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 treated groups, but they did not show any statistical significance or dose-dependency.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

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 for this strain and statistically insignificant when compared to the control group.
All male foetuses from all groups showed completion of testicular descent (abdominal), except one incomplete testicular decent in one LD group male fetuses which are considered to be an incidental finding.

Other effects:

effects observed, non-treatment-related

Description (incidence and severity):

Craniofacial examination was performed by razor blade serial sectioning technique. No statistical significance was observed in any of the treated groups when compared to the control group. A single incidence of haematoma in the midbrain at the subdural region was observed in the MD group in one foetus. Few litter incidences of subcutaneous haematoma at head region were observed in the MD (10%) and HD (15%) groups when compared to control (5%). 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. As there was no statistical significance and no dose dependency, these findings were not considered test item-related and therefore incidental in nature.

Dose descriptor:

NOAEL

Remarks:

developmental

Effect level:

>= 250 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed at this dose level.

Abnormalities:

no effects observed

Developmental effects observed:

no

Conclusions:

The study was performed in accordance to OECD TG 414 under GLP conditions and is considered reliable. In the dams, treatment related mortality was observed in a single animal of the high dose group and treatment related clinical findings were observed in mid and high dose level animals. The clinical findings were attributed to local irritant effects of the test material, which was confirmed microscopically for the high dose animals, where inflammatory and degenerative findings were observed in the stomach. As no lower dose levels were evaluated histopathologically, a NOAEL for the direct irritative effect of the test item on the gastric mucosa could not be established. Overall, a NOAEL for maternal toxicity was established at 100 mg/kg bw/day, based on mortality of one animal in the high dose group. No test item related developmental effects were observed in the study, therefore, the developmental NOAEL was >= 250 mg/kg bw/day.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

250 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The available information comprises an adequate and reliable study, and is thus sufficient to fulfil the standard information requirements set out in Annex IX, 8.7, of Regulation (EC) No. 1907/2006.

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 a prenatal developmental toxicity study according to OECD TG 414 and in compliance with GLP, nulliparous and non-pregnant female Wistar rats were mated with males (2:1 ratio) and divided into four groups of 23 animals (BSL, 2022). The pregnant females were administered the test substance trichloro(hexadecyl)silane via gavage from Gestation Day (GD) 5 to 19 at dose levels of 40 (LD), 100 (MD) and 250 mg/kg bw/day (HD), respectively. The animals of the control group received the vehicle paraffin oil.

Test item-related mortality was observed in one animal at 250 mg/kg bw/day, this animal had to be euthanized for animal welfare reasons on GD 17. Clinical signs were observed at 100 and 250 mg/kg bw/day. Clinical signs of salivations, piloerection, reduced spontaneous activity, hunched posture, eyelid closure, nasal discharge and abnormal breathing observed in MD and HD groups starting between GDs 6 and 20 were considered to be treatment-related and caused by local irritative effects immediately after dosing.

No test item-related effects on mean body weight, mean body weight gain and food consumption were observed in the treated groups when compared to control during the study.

No test item-related effects were observed on prenatal parameters including terminal body weight, adjusted maternal weight (carcass weight), 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 ratios and testicular descent in treatment groups when compared to the control.

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, except for a statistically significant increase in mean TSH in the MD group; but without dose dependency this was considered incidental. No gross or histopathological lesions were observed in thyroid or parathyroid glands.

Test item-related macroscopic findings were observed in the moribund sacrificed animal of the HD group (stomach with red coloured cardiac region, creamy consistency and spotted thymus). Macroscopic findings were also observed in three HD animals at scheduled necropsy, consisting of forestomach mucosa with multiple crater shaped indentations. Microscopic analysis revealed inflammatory and degenerative findings in the stomach of HD group animals, including the moribund sacrificed animal. The findings consisted of ulceration, erosion, hyperkeratosis, squamous hyperplasia, submucosal oedema, and mixed cell infiltrates. No microscopic analysis was performed on LD and MD animals.

No test item related and toxicologically relevant external, visceral, craniofacial and skeletal findings were observed in the foetuses of all treatment groups when compared to control.

In conclusion, as no test item related effects were noted on foetal toxicity parameters, the no observed adverse effect level (NOAEL) for developmental toxicity was established to be >= 250 mg/kg bw/day. A NOAEL for local effects could not be established, as local irritant effects were observed in the forestomach of HD animals, but no further microscopic analysis of LD and MD animals was conducted. The maternal NOAEL in terms of general toxicity was established to be 100 mg/kg bw/day, based on mortality observed in one HD animal. Given there were no adverse systemic effects observed in the corresponding 90-day repeated dose toxicity study with the substance with identical dose selection (BSL, 2022), then the cause of death in this animal was most likely due to local irritative effects in the forestomach.

Justification for classification or non-classification

The available data on reproductive toxicity of the test substance do not meet the criteria for classification according to Regulation (EC) No. 1272/2008, and are therefore conclusive but not sufficient for classification.