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Effects on fertility

Description of key information

There are no reproductive toxicity data on 3-chloropropyl(dimethoxy)methylsilane or its hydrolysis product, 3-chloropropyl(methyl)silanediol.

A draft ECHA decision has been received on a 90-day oral repeated dose toxicity test proposal. When the final decision is received a subchronic (90-day) repeated dose toxicity study with the registered substance 3-chloropropyl(dimethoxy)methylsilane will be conducted according to OECD Test Guideline 408 and in compliance with GLP. The need for an extended one-generation reproductive toxicity study will be assessed based on the results of the subchronic repeated dose toxicity study with the registered substance.

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 3-chloropropyl(dimethoxy)methylsilane, 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 based on statistically significant test item-related effects in maternal animals and foetuses at the highest dose tested of 100 mg/kg bw/day. The maternal effects included decrease in mean body weight gain and food consumption, decrease in uterus weight, increase in percentage of early resorption and pre and post implantation loss. In foetuses, statistically significant test item-related effects were observed for the mean foetal weight and male and female foetal weight on a per litter basis in the high dose group when compared to the control. These are considered to be related to the reduced maternal body weight gain and lower food consumption which were indicative of maternal toxicity at the high dose group. Furthermore, there were statistically significant skeletal findings observed in the high dose group such as incomplete ossification of several bones of the skull, sternebra, vertebra, forelimbs and hind limbs, missing ossification (unossified) for forelimb metacarpals, hind limb metatarsals, cervical centra, thoracic centra, caudal centra and caudal arches, misshapen/bent/thick bones, wavy ribs. The skeletal findings are generally classified as variation, however incidences of altered ossification were clearly increased at the highest dose tested and are considered to be a secondary effect to lowered weights of the foetuses (BSL Bioservice, 2020a).

Link to relevant study records
Reference
Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
28 February 2020 to 24 April 2020
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:
adopted 25 June 2018
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Species:
rat
Strain:
Wistar
Remarks:
Crl: WI(Han) (Full Barrier)
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: approx. 14-15 weeks old at mating
- Weight at study initiation: females: 201 - 259 g at mating
- Fasting period before study: no
- Housing: kept individually in IVC cages except during the pre-mating period when kept in groups of two animals and during mating period when two females were paired with one male.
- Diet (e.g. ad libitum): Altromin 1324 maintenance diet for rats and mice, ad libitum
- Water (e.g. ad libitum): tap water, sulphur acidified to a pH of approximately 2.8, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3°C
- Humidity (%): 55 +/- 10 %
- Air changes (per hr): 10 x / 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
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): The vehicle was selected 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: 2:1 ratio
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: sperm positive vaginal smears 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.:
25 mg/kg bw/day (actual dose received)
Remarks:
low dose (LD)
Dose / conc.:
50 mg/kg bw/day (actual dose received)
Remarks:
middle dose (MD)
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Remarks:
high dose (HD)
No. of animals per sex per dose:
23 females per group
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: In consultation with the sponsor and based on a dose range finding study. The highest dose level was chosen with the aim of inducing toxic effects, but not death or severe suffering. Thereafter, a descending sequence of dose levels was selected with a view to demonstrate any dose-related response and a NOAEL. In the dose range-finding study, pregnant Wistar rats were treated with the test item (3-chloropropyl)-dimethoxymethylsilane at dose levels of 100, 300 and 600/1000 mg/kg bw/day administered on GD 5 to 19. Test item related clinical signs and mortality were observed at 300 mg/kg bw/day (MD group) and 600/1000 mg/kg bw/day (HD group). Test item-related maternal toxicological effects in terms of body weight gain, food consumption, uterine weight, terminal maternal weight and net weight change were observed at 300 (MD) and body weight gain, food consumption at 600/1000 (HD) mg/kg bw/day when compared to the control group. The post-implantation loss was higher in MD and HD groups when compared to controls. A statistically significant reduction in mean foetal weight was observed in both male and female foetuses at 100 mg/kg bw/day. No external foetal abnormalities were noted in LD group.

- Rationale for animal assignment (if not random): random
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: general clinical observations were made once per 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: Clinical 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 or bizarre behaviour were recorded.

DETAILED CLINICAL OBSERVATIONS: Yes / No / No data
- Time schedule:

BODY WEIGHT: Yes
- Time schedule for examinations: The sperm positive females were weighed on GDs 0, 5, 8, 11, 14, 17 and 20.

FOOD CONSUMPTION: Yes
- Time schedule: Food consumption of sperm positive females was measured on GDs 5, 8, 11, 14, 17 and 20.

POST-MORTEM EXAMINATIONS: Yes / No / No data
- Sacrifice on gestation day # 20
- Organs examined: macroscopic examination of structural abnormalities or pathological changes which may have influenced the pregnancy; uteri; gastrointestinal tract (see Table 1); gravid uterus with the cervix was weighed; thyroid/parathyroid glands were weighed; a full histopathology was carried out on the preserved thyroid/parathyroid glands.

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
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]
- Other: anogenital distance; foetal weight; examination of reproductive tract; external foetal sex was compared to gonadal sex; testicular descent/cryptorchidism was examined.
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 post-hoc 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 test item-related or adverse clinical signs of toxicological relevance observed in any of treatment groups.
Clinical signs observed occasionally during the treatment period of the study included skin and fur, hairless area in three control animals (no. 13, 19, 22) on GDs 15-20, GDs 0-20 and GDs 14-20 at lower back/left forelimb, neck and lower back respectively; two animals (nos. 33, 46) in the LD group on GD 20 and GDs 15-20 at neck (left) and ventral abdomen respectively; one animal (no. 69) in MD group on GDs 18-19 at left side lower back region and one animal (no. 83) in HD group on GDs 13-19 at right cheek. All these findings are considered to be incidental findings.
Moderate piloerection was observed in two animals (no. 40, 42) on GD 20 and GD 19 respectively and one animal (no.43) showed severe piloerection on GD 15 of LD group. The clinical sign of piloerection is considered as general sign of discomfort after dosing. Slight, spontaneous reduced activity was observed in animal no. 47 of MD group on GDs 14-19. These clinical signs were observed on few days of treatment period immediately after dosing and not observed in other treated groups.
Mortality:
no mortality observed
Description (incidence):
No test-related mortality was observed during the study period and all animals survived until the end of the study.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
The mean body weight remained unaffected and increased with the progress of the study in all treatment and control groups. However, statistically significant reduction in mean body weight gain was observed in high dose group at GDs 15-20 (17.59% below control). In correlation to mean body weight gain, there were also a reduction in food consumption in HD group on GD5-20 (9.64% below control) when compared to control. These changes are considered to be test item related effects at HD group.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
There was a reduction in food consumption in HD group on GDs 5-20 (9.64% below control) when compared to control. The change is considered to be test item related effects at HD group.
Food efficiency:
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
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. A slight decrease in mean uterine weight was observed in the HD group when compared to control. The finding is considered to be a test item related effect.
Gross pathological findings:
effects observed, non-treatment-related
Description (incidence and severity):
No test item related gross pathological changes were observed during the macroscopic examination of any treatment groups.
Enlarged spleen in one LD female (no. 40) and dilated uterus in 2 LD female (no. 41, 42) and cyst in right ovary of MD female no. 47 were observed. These findings are considered to be incidental.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
No test item related histopathological findings were observed in thyroid glands and parathyroid of all females.
Histopathological findings: neoplastic:
no effects observed
Other effects:
no effects observed
Description (incidence and severity):
No statistically significant or test item related effect were observed on group mean T3, T4 and TSH hormone levels and values were comparable to the control group.
Number of abortions:
no effects observed
Description (incidence and severity):
None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice.
Pre- and post-implantation loss:
effects observed, treatment-related
Description (incidence and severity):
No test item-related effects of toxicological relevance were noted for implantation sites in treatment groups when compared to the control group. A slight increase in the percentage of pre- and post-implantation loss was observed in the HD group when compared to control. The finding is considered to be a test item related effect.
Total litter losses by resorption:
not specified
Early or late resorptions:
effects observed, treatment-related
Description (incidence and severity):
No test item-related effects of toxicological relevance were noted for late resorptions in treatment groups when compared to the control group. A slight increase in the percentage of early resorption was observed in the HD group when compared to control. The finding is considered to be a test item related effect.
Dead fetuses:
no effects observed
Description (incidence and severity):
No dead foetuses were noted in any of the groups.
Changes in pregnancy duration:
no effects observed
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice.
Key result
Dose descriptor:
NOAEL
Effect level:
50 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
body weight and weight gain
early or late resorptions
food consumption and compound intake
organ weights and organ / body weight ratios
pre and post implantation loss
Abnormalities:
effects observed, treatment-related
Localisation:
uterus
Description (incidence and severity):
Decreased mean uterine weight, increased percentage of early resorption, increased percentage of pre and post implantation loss were observed in the HD group when compared to control.
Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
Slight but statistically significant lower mean male and female foetal weight was observed on an individual basis (sum of weight of all foetuses in group divided by total number of foetuses in respective group) in the MD (male: 6.76%, female: 8.55% below control) and HD (male: 23.71%, female: 25.03% below control) groups when compared to the control. Slight but statistically significant lower foetal weights was observed in the LD group (4.62% below control) when compared to control.
Test item related effects were observed for the mean foetal weight or male and female foetal weight on a per litter basis (group mean of individual litter mean) in HD group when compared to the control.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
No test item-related effects of toxicological relevance were noted for number of live foetuses in treatment groups when compared to the control group.
Changes in sex ratio:
no effects observed
Description (incidence and severity):
No test item-related effects of toxicological relevance were noted for sex ratio in treatment groups when compared to the control group.
Changes in litter size and weights:
not examined
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Description (incidence and severity):
There were no test item related external abnormalities observed in any of the dose groups.
Skeletal malformations:
effects observed, treatment-related
Description (incidence and severity):
Craniofacial examination revealed a predominant finding, subcutaneous hematoma (general), in all treated (88%, 64% and 47% in the LD, MD and HD groups, respectively) and control groups (70%) , and a few incidences of subdural oedema in mid brain in control (5%) and LD (12%) groups, increased perimeningal space in the control (5%) and LD (6%) groups and haematoma, intracerebral at pituitary level were observed in HD group (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 that no statistical significance for any of these findings. In addition, all these values were within the historical control range for this strain.
As usual for foetuses at this stage of gestation (day 20) incomplete ossification was seen in several bones of litters in all groups including the control. Mostly, bones of the skull, sternum, paws 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, in this study a trend towards a test item-related incomplete ossification of several bones was observed, which resulted in a statistically significant higher foetal incidence of incomplete ossification of numerous bones in mostly the HD group. This is considered to be a secondary effect of the observed lower foetal weight and maternal toxicity.
Bones showing a statistically significant higher foetal incidence of incomplete ossification in the HD group compared to the control group were 2nd sternebra (48% compared to 3%), skull mandible (15% compared to 0%), vertebra caudal arches (56% compared to 2%), vertebra sacral arches (71% compared to 2%), Scapula (30% compared to 0%), forelimb humerus (25% compared to 0%), skull parietal bone (73% compared to 22%), skull frontal bone (44% compared to 6%), 4th sternebra (39% compared to 1%), vertebra thoracic arches (12% compared to 0%), skull basioccipital (10% compared to 0%), forelimb ulna (48% compared to 0%), vertebra thoracic centrum-trunk (bone)/head neck bone (28% compared to 0%), skull pre-sphenoid bone (52% compared to 1%), 1st sternebra (45% compared to 0%), skull interparietal bone (92% compared to 55%), skull zygomatic arch (Left) (9% compared to 1%), hind limb metatarsal (30% compared to 0%), forelimb radius (15% compared to 0%), skull nasal (23% compared to 2%), hind limb femur (15% compared to 0%), skull nasal (39% compared to 0%), 3rd sternebra (26% compared to 0%), skull basisphenoid (52% compared to 1%), skull maxilla (8% compared to 0%), pelvic girdle pubis (16% compared to 1%), vertebra sacral centrum (15% compared to 0%), hind limb tibia (15% compared to 0%), vertebra cervical arches (69% compared to 2%), skull squamosal bone (55% compared to 9%), ribs (28% compared to 0%), skull zygomatic arch bone (52% compared to 10%) and hind limb fibula (12% compared to 0%).
Bones showing a statistically significant higher foetal incidence of being unossified in the HD group compared to the control group were 2nd sternebra (32% compared to 0%) and vertebra caudal arch(es) (54% compared to 1%), bent scapula (32% compared to 1%), misshapen and thick forelimb humerus (20% and 10% respectively, compared to 0%), unossified 4th sternebra (12% compared to 0%), rudimentary 7th cervical rib (head-neck region- 12% compared to 0%), irregular ossification of vertebra thoracic centrum (58% compared to 14%), unossified forelimb metacarpal (91% compared to 14%), pelvic girdle caudal shift (45% compared to 2%), unossified hind limb metatarsal (29% compared to 0%), rudimentary 7th cervical right rib (6% compared to 0%), unossified 5th sternebra-truck bone (59% compared to 2%), unossified skull supraoccipital (8% compared to 0%), hind limb femur, bend (lower extremity, 4% compared to 0%), unossified 3rd sternebra-truck bone (7% compared to 0%), scapular spine, bent at upper extremity (28% compared to 0%). Incomplete and unossified pelvic girdle ischium (7% compared to 0%), unossified vertebra cervical centrum (100% compared to 69%), unossified vertebra caudal centrum (25% compared to 0%), unossified vertebra sacral centrum (16% compared to 0%), unossified 6th sternebra (89% compared to 2%), Irregular ossification of vertebra lumbar centrum (20% compared to 1%), rudimentary 7th cervical left rib (12% compared to 0%), vertebra cervical cartilaginous arches fused, head-neck (cartilage) (42% compared to 5%), supernumerary cervical cartilaginous rib head-neck (cartilage) (10% compared 0%) and hind limb fibula bent, lower extremity (4% compared to 0%).
The occurrence of wavy ribs was statistically significant higher in the HD group when compared to control (84% compared to 18%). In general, wavy ribs are typically classified as transient and reversible postnatally and may thus be considered as variations but not malformations.
In the LD and HD groups, statistically significant higher foetal incidences were observed for skull basioccipital (cartilage) with small hole, at head-neck (cartilage) region in the MD group (5% compared to 0%) unossified forelimb metacarpals in the LD and MD groups (49 and 56% respectively, compared to 14%), incomplete ossification of skull supraoccipital in the MD group (97% compared to 77%), unossified cervical vertebral centrum in the LD and MD groups (88% and 97% respectively, compared to 69%) and unossified 6th sternebra in the MD group (37% compared to 2%).
Statistically significant lower foetal incidences of incomplete ossification of 6th sternebra were observed in the HD group (8% compared to 76%). Statistically significant lower foetal incidences of vertebra sacral centrum and arch fused, lower extremity was observed in the MD group (0% compared to 5%). Statistically significant higher foetal incidences of vertebra cervical cartilaginous arches fused, lower extremity were observed in the MD group (45% compared to 5%).
All the statistically significant changes observed in HD groups are considered to be test item-related effects.
Other ossification-related findings observed at lower or higher incidences showed no statistical significance or dose-dependency and were thus not considered of toxicologically relevance.
There were also slightly higher or lower foetal incidences of skeletal findings in the LD and MD groups, but they did not show statistically significant changes.
Visceral malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Slight but statistically significantly lower litter incidences of azygos vein (bilateral) was observed in HD group (42.1% compared to 80%) when compared to the control.
All other litter incidences were statistically insignificant when compared to the control group. Higher litter incidences for long thymus were observed in the MD and HD groups (16% and 21%, respectively, compared to 0% in the control). In the LD group, there were higher litter incidences observed for malpositioning of the umbilical artery (53% compared to 50% in the control). Higher litter incidences of malpositioned testes were observed in the HD group (21% compared to 10% in the control). Higher litter incidences of abdomen internal haemorrhage were observed (82%, 79% and 63% in the LD, MD and HD groups, respectively, compared to 80% in the control). Higher litter incidences of liver, supernumerary lobe were observed in the LD, MD and HD groups (41%, 68% and 63%, respectively, compared to 45% in the control group).
Visceral findings observed in the dose groups were at frequencies generally comparable to or, in some cases, slightly higher or lower in frequency compared to the control. The observed findings were either minor variations and/or due to a lack of dose dependency and consistency, therefore, no toxicological significance can be attributed to these findings and they were considered to be spontaneous in nature. In addition, all these values were within the historical control range for this strain.
Other effects:
effects observed, non-treatment-related
Description (incidence and severity):
In males 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 group, except for a marginal but statistically significant decrease in absolute AGD in male HD foetuses and an increase on relative AGD in HD female foetuses. As these values are within the historical control range, these finding are considered to be incidental findings.
All male foetuses showed completion of testicular descent (abdominal) in all male foetuses from all groups.
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:
fetal/pup body weight changes
skeletal malformations
Key result
Abnormalities:
effects observed, treatment-related
Localisation:
skeletal: skull
skeletal: scapule
skeletal: forelimb
skeletal: rib
skeletal: vertebra
skeletal: hindlimb
Description (incidence and severity):
At skeletal examination, a trend towards incomplete ossification of several bones could be observed with statistically significantly higher foetal incidences of incomplete ossification in the HD group. These include bones of the skull, sternebra, vertebra, forelimbs and hind limbs. Foetal incidence for missing ossification (unossified) was statistically significantly higher mostly in the HD group for forelimb metacarpals, hind limb metatarsals, cervical centra, thoracic centra, caudal centra and caudal arches.
Increasing incidence of misshapen/bent/thick bones was observed in HD group resulting in statistically significant differences of some findings which were considered test item-related. Misshapen bones were seen as short and thick which was classified as malformation; as this finding was assumed to be permanent and possibly affecting health.
Misshapen bent scapulae and bent scapular spines were observed with statistically significantly higher foetal incidence in the HD group. The finding of bent scapula appears to be transient and completely repaired postnatally. Without corresponding external observations of short and/or malformed limbs they may be classified as variation.
Wavy ribs were observed with statistically significantly higher foetal incidence in the HD group. In general, wavy ribs are typically classified as transient and reversible postnatally and thus may be considered as variations which are not considered as an adverse effect of treatment with the test item. However, they are reported to occur more often in the presence of maternal and/or foetal toxicity, secondary to generalized toxicity or stress. Thus, the significantly higher incidence of wavy ribs in the HD group might be related to maternal toxicity with the observed reduced body weight and food consumption of dams of the HD group.
Developmental effects observed:
yes
Lowest effective dose / conc.:
100 mg/kg bw/day (actual dose received)
Treatment related:
yes
Relation to maternal toxicity:
developmental effects as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
yes
Relevant for humans:
not specified

Concentration analysis of formulation samples was determined at three concentrations, 6.25 mg/mL, 12.5 mg/mL and 25.0 mg/mL in study weeks 1, 2 and in the last week of the study. The mean recoveries observed for the LD dose group was between 93.0% and 98.8% of the nominal value, between 86.9% and 98.9% for the MD dose group and between 87.5% and 101.0% of the nominal value for HD dose group. The mean recoveries observed in the low dose (LD), medium dose (MD) and high dose (HD) groups were 95.9%, 92.9%, and 94.3% of the nominal concentration, respectively.

See attachments for result tables.

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 was concluded to be 50 mg/kg bw/day based on statistically significant test item-related effects in maternal animals at the highest dose tested of 100 mg/kg bw/day such as decrease in mean body weight gain and food consumption, decrease in uterus weight, increase in percentage of early resorption and pre and post implantation loss. In addition, statistically significant test item-related effects were observed for the mean foetal weight or male and female foetal weight on a per litter basis in the high dose group when compared to the control. These are considered to be related to the reduced maternal body weight gain and lower food consumption which were indicative of maternal toxicity at the high dose group. Furthermore, there were statistically significant skeletal findings observed in the high dose group such as incomplete ossification of several bones of the skull, sternebra, vertebra, forelimbs and hind limbs, missing ossification (unossified) for forelimb metacarpals, hind limb metatarsals, cervical centra, thoracic centra, caudal centra and caudal arches, misshapen/bent/thick bones, wavy ribs. The skeletal findings are generally classified as variation, however incidences of altered ossification were clearly increased at the highest dose tested and are considered to be a secondary effect to lowered weights of the foetuses.
Effect on developmental toxicity: via oral route
Endpoint conclusion:
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 (3-chloropropyl)dimethoxymethylsilane, conducted according to OECD Test Guideline 414 and in compliance with GLP, the test substance was administered daily via oral (gavage) to pregnant female Wistar rats during gestation days (GDs) 5 to 19 at doses of 0, 25 (LD), 50 (MD) or 100 (HD) mg/kg bw/day in dried and de-acidified corn oil (BSL Bioservice, 2020a). The dose levels in the study were selected in consultation with the sponsor and based on a dose range finding study (BSL Bioservice, 2020b). The highest dose level was chosen with the aim of inducing toxic effects, but not death or severe suffering. Thereafter, a descending sequence of dose levels was selected with a view to demonstrate any dose-related response and a NOAEL. In the dose range-finding study, pregnant Wistar rats were treated with the test item (3-chloropropyl)-dimethoxymethylsilane at dose levels of 100, 300 and 600/1000 mg/kg bw/day administered on GD 5 to 19. Test item related clinical signs and mortality were observed at 300 mg/kg bw/day (MD group) and 600/1000 mg/kg bw/day (HD group). Test item-related maternal toxicological effects in terms of body weight gain, food consumption, uterine weight, terminal maternal weight and net weight change were observed at 300 (MD) and body weight gain, food consumption at 600/1000 (HD) mg/kg bw/day when compared to the control group. The post-implantation loss was higher in MD and HD groups when compared to controls. A statistically significant reduction in mean foetal weight was observed in both male and female foetuses at 100 mg/kg bw/day. No external foetal abnormalities were noted in LD group.

During the administration period, the animals were observed each day for signs of toxicity and mortality. All female animals were sacrificed on the respective GD 20. Following the gross necropsy, the uteri and ovaries were removed, weighed and examined for number of implantations, resorptions (early and late), and live and dead foetuses. Foetuses were identified, 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 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 the same days. During necropsy the thyroid/parathyroid glands from all dams were preserved and weighed. 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. In addition, special attention was given to the gastrointestinal tract in order to assess possible corrosive effects of the test substance. The following organs were observed for macroscopic findings and collected for histopathological evaluation: head with paranasal sinuses, oral cavity (pharynx), oesophagus, stomach and intestine.

Summary results, maternal findings

No test substance-related mortality was observed during the study period and all animals survived until the end of the study. There were no test substance-related or adverse clinical signs of toxicological relevance observed in any of treatment groups. The mean body weight remained unaffected and increased with the progress of the study in all treatment and control groups. However, statistically significant reduction in mean body weight gain was observed in high dose group at GDs 15-20 (17.59% below control). In correlation to mean body weight gain, there was also a reduction in food consumption in HD group on GDs 5-20 (9.64% below control) when compared to control. These changes are considered to be test item related effects at HD group. 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 22/23 in the control group. None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice. No test item-related effects of toxicological relevance were noted for any prenatal parameter including terminal body weight, adjusted maternal weight (carcass weight), net weight change from GD 0, number of corpora lutea, implantation sites, late resorptions, 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. A slight decrease in mean uterine weight, increase in percentage of early resorption and in percentage of pre- and post-implantation loss were observed in the HD group when compared to control. These findings are considered to be test item related effects. 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 effect were observed on group mean T3, T4 and thyroid stimulating hormone (TSH) 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. No test item related histopathological findings were observed in thyroid glands and parathyroid of all females. Since no macroscopic changes were noted in the organs of the gastrointestinal tract, they were not examined at histopathology.

Summary results, foetal findings

In male and female foetuses, body weight and 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 males 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 showed completion of testicular descent (abdominal) in all male foetuses from all groups. Test item-related effects were observed for the mean foetal weight or male and female foetal weight on a per litter basis (group mean of individual litter mean) in HD group when compared to the control group. There were no test item related external abnormalities observed in any of the dose groups. Internal observation of the foetal viscera revealed a range of visceral findings in all groups including control. Visceral findings observed in the dose 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 due to a lack of 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 dose groups were well within the historical control data range and statistically insignificant when compared to the control group. Craniofacial examination revealed a predominant finding of general subcutaneous hematoma in all treated (88%, 64% and 47% in the LD, MD and HD groups, respectively) and control groups (70%) and a few incidences of subdural oedema in mid brain in control (5%) and LD (12%) groups, increased perimeningeal space in the control (5%) and LD (6%) groups and haematoma, intracerebral at pituitary level, were observed in HD group (5%). These findings were considered to be spontaneous in nature and not relate 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 revealed a range of findings in all groups including control. At skeletal examination, a trend towards incomplete ossification of several bones was observed with statistically significantly higher foetal incidences of incomplete ossification in the HD group. These included bones of the skull, sternebra, vertebra, forelimbs and hind limbs. Foetal incidence for missing ossification (unossified) was statistically significantly higher mostly in the HD group for forelimb metacarpals, hind limb metatarsals, cervical centra, thoracic centra, caudal centra and caudal arches. Increasing incidence of misshapen/bent/thick bones was observed in HD group resulting in statistically significant differences of some findings which were considered test item-related. Misshapen bones were seen as short and thick which was classified as malformation; as this finding was assumed to be permanent and possibly affecting health. Misshapen bent scapulae and bent scapular spines were observed with statistically significantly higher foetal incidence in the HD group. The finding of bent scapula appears to be transient and completely repaired postnatally. Without corresponding external observations of short and/or malformed limbs they may be classified as variation. Wavy ribs were observed with statistically significantly higher foetal incidence in the HD group. In general, wavy ribs are typically classified as transient and reversible postnatally and thus may be considered as variations which are not considered as an adverse effect of treatment with the test item. However, they are reported to occur more often in the presence of maternal and/or foetal toxicity, secondary to generalized toxicity or stress. Thus, the significantly higher incidence of wavy ribs in the HD group might be related to maternal toxicity with the observed reduced body weight and food consumption of dams of the HD group. There were also slightly higher foetal incidences of skeletal findings in LD and MD groups, though they did not show statistically significant changes and/or many of these findings were within historical control range for this strain, hence it not considered as test item related findings at lower dose groups.

Conclusion

Based on the findings of the study, the maternal and developmental NOAEL was concluded to be 50 mg/kg bw/day. The NOAEL was based on effects on body weight gain, food consumption, uterus weight, percentage of early resorption and pre- and post-implantation loss in maternal animals at 100 mg/kg bw/day and effects on foetal weight and skeletal malformations in foetuses at 100 mg/kg bw/day group. The foetal effects were concluded to be secondary to maternal toxicity.

Summary of preliminary prenatal developmental toxicity study

In the preliminary prenatal developmental toxicity study, not conducted according to any OECD Test Guideline or GLP, 3-chloropropyl(dimethoxy)methylsilane was administered orally (gavage) in dried and deacidified corn oil to pregnant female rats during gestation days 5 to 19 at doses of 0, 100 (low dose, LD), 300 (middle dose, MD), 600/1000 (high dose, HD) mg/kg bw/day (BSL Bioservice, 2020b). Each test group consisted of 8 animals. Four high dose group animals were given 1000 mg/kg bw/day. One of these animals (no 28) received the reduced high dose of 600 mg/kg bw/day from gestation day 8. The other four high dose animals received 600 mg/kg bw/day only. Test item-related clinical signs and mortality were observed at 300 mg/kg bw/day (MD group) (1/8) and 600/1000 mg/kg bw/day (7/8) (HD group). Test item-related maternal toxicological effects in terms of body weight gain, food consumption, uterine weight, terminal maternal weight and net weight change were observed at MD group and body weight gain, food consumption at HD group when compared to the control group. Test item-related histopathological findings were observed in the stomach and glandular components of MD and HD group dams. There were no foetuses in the MD and HD groups at respective C-sections. The post-implantation loss was higher in MD and HD groups when compared to controls. This was likely related to a higher rate of early resorptions at both dose groups. No external foetal abnormalities were noted in this study.

Justification for classification or non-classification

Based on the available data, 3-chloropropyl(dimethoxy)methylsilane is not classified for reproductive or developmental toxicity according to Regulation (EC) No 1272/2008.

Additional information