Triethoxy(phenyl)silane

Endpoint summary

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Effects on fertility

Description of key information

OECD TG 422 (GLP, RL1, rat, oral):

NOAEL systemic toxicity = 40 mg/kg bw/day

NOAEL reproductive toxicity = 360 mg/kg bw/day

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

29 July 2016

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayrisches Landesamt für Gesundheit und Lebensmittelsicherheit

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Females nulliparous and non-pregnant: yes
- Age at study initiation: 14 - 15 weeks old
- Weight at study initiation: Males: 343 - 389 g; Females: 203 - 240 g
- Fasting period before study: not reported
- Housing: Housed in groups of 5 animals/sex/cage during the premating period for both males and females and during post-mating period for males depending on the mating status. Housed in ratio 1:1 (male to female) during the mating period. After the confirmation of mating, females were individually housed during gestation/lactation period and males were returned to their original cage. Animals of the recovery group were housed in groups of 3 animals/sex/cage.
- Diet: Altromin 1324 maintenance diet provided ad libitum
- Water: Tap water, sulphur acidified to a pH of approximately 2.8 provided ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- 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

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The test item was weighed 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. After homogenization the formulation was overlaid with argon to prevent instability caused by repeated contact of the test item formulation with air.

VEHICLE
- Justification for use and choice of vehicle: The vehicle was selected in consultation with the sponsor based on the test item’s characteristics and testing guideline.
- Amount of vehicle: 4 mL/kg body weight
- Lot/batch no.: MKCD1021

Details on mating procedure:

- M/F ratio per cage: 1:1 ratio
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy
- After successful mating each pregnant female was individually caged during gestation/lactation period in type III H, polysulphone cages.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Nominal concentrations were confirmed for all dose groups, as measured concentrations were within acceptance criterion of 15%.

Duration of treatment / exposure:

28 days for males and up to 63 days for females

Frequency of treatment:

The test item was administered daily.

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

No. of animals per sex per dose:

The 4 groups consisted of 10 male and 10 female rats.
Two recovery groups (control and high dose group) consisted of 12 male and 12 female rats.

Control animals:

yes

Details on study design:

- Dose selection rationale: Doses were selected based on the results of a 14-day oral dose range finding study, in which doses of 1000 mg/kg bw/day were found to be in the lethal toxic range, while at 100 and 300 mg/kg bw/day no signs of toxicity were noted.
- Rationale for animal assignment: Randomisation was performed with validated IDBS Workbook 10.1.2 software.

Positive control:

None

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: 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.
- 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, difficult or prolonged parturition or bizarre behaviour were recorded. Prolonged parturition of pregnant females and maternal behaviour during lactation period were also monitored.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once before the first exposure, and at least once a week thereafter.

BODY WEIGHT: Yes
- Time schedule for examinations: Once before the assignment to the experimental groups, on the first day of dosing and weekly thereafter as well as at the end of the study. During pregnancy, females were weighed on gestation days (GD) 0, 7, 14 and 20 and within 24 hours of parturition (day 0 post-partum), on PND 4, PND 9 and PND 13 along with pups. All animals were weighed directly before termination. Any animals prematurely sacrificed were weighed prior to the sacrifice.

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

OTHER: Multiple detailed behavioural observations were made in the week before the first treatment and during the last week of the treatment in 5 randomly selected males and during the last week of the lactation period in 5 randomly selected females (only lactating females were evaluated) of each group outside the home cage using a functional observational battery of tests. Sensory reactivity to different modalities, grip strength and motor activity assessments and other behavioural observations as well as supported rearing and non- supported rearing, urination, defecation, startle/ auditory response, equilibrium reflex, positional passivity, visual placing, fore and hind limb grip strength, tail pinch response, toe pinch reflex, extensor thrust/limb tone, hind limb reflex, righting reflex on the ground, air righting reflex, pupil response, body temperature and ophthalmoscopy (anterior chamber of the eye and fundus of eye).

A urinalysis was performed with samples from 5 randomly selected males and females (only lactating females were evaluated) prior to or as part of the sacrifice of the animals. Additionally, urine colour/ appearance was recorded. In the case of recovery groups, urinalysis was performed for all males and females at the end of the recovery period.

Haematology and clinical chemistry parameters were also evaluated.

Oestrous cyclicity (parental animals):

Estrous cycles were monitored before the start of the treatment to select for the study females with regular cyclicity (using vaginal smears). In addition, vaginal smears were also examined daily from the beginning of the mating period until evidence of mating of main study females.

Sperm parameters (parental animals):

Parameters examined in male parental generations: testis weight, epididymis weight, tubular stages of the spermatogenic cycle

Litter observations:

PARAMETERS EXAMINED
The following parameters were examined in offspring: number and sex of pups, stillbirths, live births, runts, presence of gross anomalies, weight gain, any abnormal behaviour, anogenital distance (AGD), and presence of nipples/areolae in male pups.

GROSS EXAMINATION OF DEAD PUPS: yes, for external and internal abnormalities

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals were sacrificed by using anesthesia (e.g. ketamine/xylazine), followed by exsanguination. The males of the recovery groups were subjected to necropsy 14 days after the last administration (end of recovery period).
- Maternal animals: All surviving animals were sacrificed on the respective PND 13 by using anesthesia (e.g. ketamine/xylazine), followed by exsanguination. Non-pregnant females were sacrificed on day 26 from the day of mating or from the last day of mating period. The females of the recovery groups were subjected to necropsy 14 days after the first scheduled necropsy of dams of any main group.

GROSS NECROPSY
- Gross necropsy consisted of careful examination of the external surface of the body, all orifices and the cranial, thoracic and abdominal cavities and their contents. Special attention was paid to the organs of the reproductive system. The ovaries, uterus with cervix, vagina, testes, epididymides, accessory sex organs (prostate, seminal vesicles with coagulating glands as a whole), the thyroid/parathyroid glands and all organs showing macroscopic lesions of all adult animals were preserved.

All animals found dead and/or intercurrently euthanised for animal welfare reasons were subjected to a gross necropsy and the organs preserved for a histopathological examination.

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in tables below were prepared for microscopic examination and weighed, respectively.

Postmortem examinations (offspring):

SACRIFICE
-On PND 13 dead pups and all surviving pups.

GROSS NECROPSY
- Blood samples were collected from the defined site in serum separator tubes from 2 female pups/litter on day 4 after birth from all dams and 2 pups/litter at termination on day 13 and from all adult males at termination. Blood samples from the day 13 pups and the adult males were assessed for serum levels for thyroid hormones (T4). Pup blood was pooled by litter for thyroid hormone analysis. Two pups per litter were sacrificed on day 4 after birth and blood samples were taken for possible serum hormone assessments. The two pups per litter were female pups to reserve male pups for nipple retention evaluations.

- Thyroid/parathyroid glands from 1 pup/sex/litter/group sacrificed on PND 13 and non-selected adult animals were preserved for potential histopathological examination, if required.

Statistics:

A statistical assessment of the results of behavioural parameters, body temperature, body weight, food consumption, clinical pathology parameters, organ weights and litter data was performed for each gender by comparing values of dosed with control animals using a one-way ANOVA and a post-hoc Dunnett Test. Results of absolute and relative organ weights, parameters of haematology, blood coagulation and clinical biochemistry 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. Statistical comparisons of data acquired during the recovery period were performed with a Student’s t-Test.

Reproductive indices:

Copulation Index (%) = (No. of rats copulated / No. of pairs) X 100
Fertility Index (%) = (No. of females pregnant / No. of females copulated) X 100
Delivery Index (%) = (No. of dams with live newborns / No. of pregnant dams) X 100
Viability Index (%) = (No. of live offspring at day 4 / No. of live offspring at birth) X 100

The number of implantation sites and corpora lutea was recorded for each parental female at necropsy. If appropriate and possible, the number of corpora lutea and implantation sites was recorded for any females sacrificed 26 days after the end of the mating period with no evidence of mating and or on day 26 post-coitum due to non-delivery.

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

At the high and mid dose, frequently observed clinical sings included moving the bedding, salivation, piloerection and alopecia. In the LD group females, few incidences of moving the bedding, salivation, piloerection and alopecia. Salivation and moving the bedding were mainly observed immediately after dose administration and, therefore, were considered to be a sign of discomfort due to a local reaction to the test item or adverse taste.

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

One high-dose recovery male rat (no. 92) was euthanised on study day 15. Clinical signs included markedly reduced spontaneous activity, prone position, slight salivation, wasp waist, dehydration, moderate piloerection, hypothermia, abnormal breathing. At necropsy, both kidneys were found enlarged, one kidney was white and of viscous consistency and ureters were dilated. Histopathologic al examination results show that the cause of morbidity is assumed to be a consequence of backflow nephrosis and it is considered to be treatment-related.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weights were statistically significantly lower in high-dose males throughout the study period when compared with the control group (up to 10 % below controls). In recovery males, no statistically significant changes were observed during the recovery period when compared to the respective control group.

In females, no statistically significant effect on body weight was observed during the premating and mating period. At the end of the gestation and start of the lactation period, however, body weights were statistically significantly lower in high-dose dams when compared to the controls (between 6 and 11% below controls). Statistically significantly lower body weight gain was observed in those animals on gestation day 14-20. During the recovery period, a slight but statistically significantly higher body weight was seen in high-dose females when compared to the recovery control group (approx. 6% higher). A tendency towards higher body weights, however, was seen in these animals already during the treatment period showing a statistical significance on day 42.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

During the premating period food consumption of high-dose males was slightly lower when compared to controls (30% and 28% below controls in premating week 1 and 2, respectively), while food consumption of low- and mid-dose males was comparable to the controls.

Slightly lower food consumption was also found in high-dose females, i.e. between gestation days 7 and 20 (approx. 16% below controls).

Food consumption during the recovery period in males and females were found to be comparable to the controls.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

A slight decrease or increase in the mean % neutrophils in mid-dose females at the end of the treatment period and % reticulocytes in high-dose males at the end of the recovery period, were not considered biologically relevant as these values were within the historical range of this strain.

Blood coagulation was not affected by the test item. Minimal but statistically significant differences in activated partial thromboplastin time in high-dose recovery males are not considered to be biologically relevant, as the individual values were within the normal range of variation for this strain.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

In male animals a slight but statistically significant decrease in creatinine level in the mid group and in aspartate-aminotransferase level in the mid- and high-dose groups are not of biological relevance as they were slight decreases and not associated with pathological conditions. Slight statistically significant increases in albumin in the males of the low-dose group and total cholesterol in the males of the mid-dose group are not considered toxicologically relevant as values were in the historical control ranges and without dose-dependency.

At the end of the recovery period the slight but statistically significant increase in glucose in male animals of the high-dose group and the decrease in aspartate-aminotransferase are not considered toxicologically relevant as they were in the range of historical control data. In females of the high-dose group slightly lower alanine aminotransferase level and slightly higher potassium level are not considered toxicologically relevant as values were in the range of historical control data.

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

A backflow nephrosis was recorded in two males at 120 mg/kg bw/day, and in all males and four females at 360 mg/kg bw/day.

In the kidneys of males at 120 mg/kg bw/day, the incidence of minimal tubular basophilia exceeded the background incidence levels. At 360 mg/kg bw/day, both sexes were affected, whereby the mean severity increased in both sexes, and males were much more affected than females. This finding was associated with inflammatory lesions, i.e., pyelitis was noted in males at 120 mg/kg bw/day, and pyelitis and interstitial inflammation, interstitial fibrosis and papillary necrosis were noted in both sexes at 360 mg/kg bw/day. The papillary necrosis appeared focally at the urothelium. Furthermore, the incidence of pelvic dilatation increased in males with dose (all doses), and tubular dilatation was noted in almost all males at 360 mg/kg bw/day. The findings caused urothelial hyperplasia, in two males at 120 mg/kg bw/day, and in all males and four females at 360 mg/kg bw/day.

The ureters of one male at 120 mg/kg bw/day, and from all males and three females at 360 mg/kg bw/day were dilated. In animals at 360 mg/kg bw/day, the findings were associated in some cases with mucosal and/or muscularis hyperplasia, and/or inflammation. Mucosal hyperplasia was occasionally observed, but the highest severity degrees were noted in ureter segments adjacent to the vagina and prostate gland.

The findings in the urinary bladder were characterized mainly by diffuse urothelial hyperplasia in both sexes at 120 and 360 mg/kg bw/day. This finding was associated with an increased incidence and severity of mononuclear cell foci.

In one male, the urethra was found in its full length and diameter within the prostate tissue. The urothelium showed a moderate hyperplasia accompanied by a minimal subacute inflammation. At some locations, in mucosal folds, precipitation of an unknown material was seen.

After the recovery period, findings were still present but decreased in severity. All animals were affected. Pelvic dilatation was noted in the decedent male only. No tissue from the urethra could be evaluated from recovery animals.

Diffuse cortical hypertrophy was noted in females at 40 mg/kg bw/day, and in both sexes at 120 and 360 mg/kg bw/day. After the recovery period, there were no differences between controls and test item-treated animals.

Increased thymic atrophy was noted in females at 40 mg/kg bw/day, and in both sexes at 120 and 360 mg/kg bw/day. After the recovery period, there were no differences between controls and test item-treated animals.
 
There were no abnormalities in the male reproductive organs. In addition, during sperm staging of PAS stained testicular sections, there were no indicators for induced lesions.

There were no abnormalities in the female reproductive organs. Female no. 65 from the mid dose group was non-pregnant. The reproductive organs of this female and its mating partner, male no. 25, did not reveal any specific abnormality in reproductive organs.

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

effects observed, non-treatment-related

Description (incidence and severity):

A slightly reduced copulation index of 90% in the high-dose group was observed compared to 100% in the control group. This is considered as biological variation. Fertility index was slightly lower in the high-dose group (80%), when compared to controls. As this included the non-mated female only a single high-dose females was affected. Moreover, as this value was within the range of historical control data, this is not considered to test item related.

See background material.

Key result

Dose descriptor:

NOAEL

Remarks:

systemic

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

organ weights and organ / body weight ratios

gross pathology

histopathology: non-neoplastic

Key result

Dose descriptor:

NOAEL

Remarks:

reproductive

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: There were no effects on estrous cyclicity, precoital interval, gestation duration. No adverse effect were observed with regards to sperm. There were no specific lesions noted in the reproductive system organs from males and females.

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

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

System:

urinary

Organ:

bladder

kidney

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Clinical signs:

not examined

Dermal irritation (if dermal study):

not examined

Mortality / viability:

mortality observed, non-treatment-related

Description (incidence and severity):

No test item related effect was observed on mean mortality of pups between PND 0 and PND 4 and during PND 4-13 in low- and mid-dose groups. However, a slightly higher mean mortality of pups on PND 1 was observed in the mid-dose group (3.7 %) and high-dose group (1.4 %). As this effect was only slight and not dose-dependent, it is not considered to be an adverse effect of the test item.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

effects observed, non-treatment-related

Description (incidence and severity):

In male pups, slightly but statistically significantly lower absolute and relative anogenital distance (AGD) was observed in the low-dose group when compared to the controls. At the time of measurement male pup weight was slightly but statistically significant lower in the high dose group when compared to controls (approx. 6% below controls). This is likely to be related to slightly lower body weight of the high-dose group dams at the end of the gestation period. In female pups, slightly but statistically significantly higher absolute and relative anogenital distance was observed in the low-dose group when compared with the controls. As no considerable difference was seen in the mid- and high-dose groups and values were within the historical control data, this is not assumed to be test item related.

No statistically significant effect or toxicological relevance was observed on nipple retention in the pups of any of the groups when compared with the controls.

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

No test item-related effect of toxicological relevance or statistical significance was observed on pup thyroid weight in males and PND 13 pups of the dose groups when compared to the controls.

Gross pathological findings:

no effects observed

Description (incidence and severity):

Few pups were found dead/still born on PND 0. Few specific findings like absent tail tip were observed. The external findings like absent hair coat on back, black, absent tail tip were considered to be spontaneous and not related to test item treatment.

No test item-related gross external abnormalities of toxicological relevance on PND 0-12 were observed in the pups of any of the groups.

Histopathological findings:

not examined

Other effects:

no effects observed

Description (incidence and severity):

Serum thyroxine hormone (T4) levels were in the normal range of variation in all groups. No differences between the dose groups and control group were seen that can be considered biologically relevant. A minimal tendency towards lower values observable in the dose groups is related to control values that were in the upper range of historical control data.

Behaviour (functional findings):

not examined

Developmental immunotoxicity:

not examined

See background material.

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: There were no effects on litter data, litter weight data, pup survival data, anogenital distance and nipple retention, pup thyroid weight and thyroid hormone analysis in pups sacrificed on PND 13.

Key result

Critical effects observed:

no

Key result

Reproductive effects observed:

no

Conclusions:

A well reported oral combined repeated dose/reproductive and developmental screening study, conducted according to the current guideline and in accordance with GLP, reported a NOAEL for reproductive effects at the highest tested dose of 360 mg/kg bw/day. General systemic parental effects were reported at the mid dose of 120 mg/kg bw/day.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

360 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

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

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

A reliable combined repeated dose/reproductive and developmental screening study according to OECD 422 is available for triethoxy(phenyl)silane (Eurofins, 2019). The test substance was administered in corn oil as vehicle at dosages of 40, 120, and 360 mg/kg body weight/day, and controls received the vehicle only. Two recovery groups were included which were treated with vehicle only or 360 mg test substance/kg bw/day. 

Treatment-related effects were observed in body weight and food consumption in the high dose group. One male rat from the high dose group with 360 mg/kg bw/day was sacrificed moribund on day 15. The death was considered treatment-related as a consequence of backflow nephrosis. At necropsy adverse effects in kidneys and urinary bladder were observed at 120 and 360 mg/kg bw/day. The systemic toxicity is described in detail under the chapter “repeated dose toxicity”.

There were no effects on estrous cyclicity, litter data, litter weight data, precoital interval and duration of gestation, reproductive indices, anogenital distance and nipple retention, pup thyroid weight and thyroid hormone analysis in parental males and pups sacrificed on PND 13 and male sacrificed at the end of recovery period in all groups up to 360 mg/kg bw/day.

A very slight and dose-dependent tendency towards lower a serum thyroxine hormone (T4) level was observed in PND 13 pups of the dose groups when compared to controls. A relation to treatment with the test item cannot be excluded.

Histopathologically, no specific lesions were noted in the reproductive system organs from males and females.

Based on the findings in the urinary tract, the NOAEL for triethoxyphenylsilane in this study for general toxicity is considered to be 40 mg/kg bw/day. As no effects were observed in any reproductive toxicity aspects, the NOAEL for reproductive toxicity is considered to be 360 mg/kg bw/day.

Furthermore, for the oral route, a reliable key OECD 422 combined repeated dose/reproductive and developmental screening study is available for the structural analogue substance trimethoxyphenylsilane (CAS 2996-92-1), conducted according to OECD TG 422 and in accordance with GLP was available for assessment of reproductive toxicity (SEHSC, 2009). Ten male and female Wistar rats per dose group were treated daily with 100, 250, 500 mg/kg bw/day trimethoxy(phenyl)silane from 2 weeks prior to mating for 4 (males) or 7 (females) weeks. No mortality or clinical signs were observed. Mean precoital time, fertility and gestation indices and conception rate were not affected by the treatment with the test item. Implantation rate and post-implantation loss were also not affected by the treatment with the test item. Thickening of the urinary bladder, which was correlated with transitional cell hyperplasia was observed in all treatment groups. In addition multifocal tubular degeneration was observed in the kidneys of male (250 and 500 mg/kg bw) and female (500 mg/kg bw) animals. Hyperplasia was observed in the kidneys of male and female rats of the 250 and 500 mg/kg bw dose groups.

In conclusion, the NOAEL for reproductive effects was determined to be 500 mg/kg bw/day, which was the highest dose tested. No NOAEL was derived for parental toxicity as general systemic effects were reported at the lowest tested dose of 100 mg/kg bw/day.

Both silanes caused adverse effects in the urinary tract and no effects on reproduction. Thus, read-across between these two substances can be justified.

Effects on developmental toxicity

Description of key information

OECD TG 414 (GLP, RL1, rat, oral):

NOAEL systemic toxicity = 120 mg/kg bw/day

NOAEL developmental toxicity = 400 mg/kg bw/day

OECD TG 422 (GLP, RL1, rat, oral):

NOAEL systemic toxicity = 40 mg/kg bw/day

NOAEL developmental toxicity = 360 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:

31 March 2020 to 28 May 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:

2018

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP-Landesleitstelle Bayern, Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

Crl: WI(Han)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: approx. 11-12 weeks
- Weight at study initiation: males: 324.3 – 429.5 g; females: 195.8 – 254.9 g
- Fasting period before study: no
- Housing: 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)
- Diet: ad libitum to Altromin 1324
- Water: ad libitum to tap water, sulphur acidified to a pH of approximately 2.8 (drinking water,municipal residue control, microbiological controls at regular intervals)
- Acclimation period: at least 5 days

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

IN-LIFE DATES: From: 17 March 2020 To: 28 May 2020

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Corn oil was filtered through a mixture of activated silica gel 60 and aluminium oxide (1:1, volume/volume), which had been filled into a glass chromatography column to three quarters of its height. For filtering, a vacuum of 75 mbar was applied. The dried and de-acidified vehicle was overlaid with argon and stored until usage.
The test item was weighed into a tared plastic 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.
After homogenization the formulation was overlaid with argon to prevent instability caused by repeated contact of the test item formulation with air.
Based on the results of stability testing (Eurofins Munich Study No. 178274), the test item formulations were prepared at least once in 10 days at room temperature. The prepared formulation was stored protected from light and at room temperature.


VEHICLE
- Justification for use and choice of vehicle: The vehicle was selected in consultation with the sponsor based on the test item’s characteristics and testing guideline.
- Concentration in vehicle: 0, 10, 30, 100 mg/mL
- Amount of vehicle (if gavage): 4 mL/kg bw

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 at Eurofins Munich as part of a separate GLP study (Eurofins Munich Study No. 178274). The formulations (10, 25 and 250 mg/mL) were stable for 6 h and for 10 days at room temperature and at -15 to -35 °C. Therefore, it was decided to store prepared formulations at room temperature and use them within 10 days after preparation.
Since 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 only taken for determining the substance concentration in the first and 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 at Eurofins Munich (Eurofins Munich Study Phase No. 193040) and until then stored under appropriate conditions based on available stability data. The B-samples were retained at below -15 °C at BSL Munich (test facility) and discarded after completion of the final study report.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:2
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

GD 5 to GD 19

Frequency of treatment:

daily

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

No. of animals per sex per dose:

23

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose levels are based on two 14-day oral dose range finding studies (BSL Munich Study Nos. 178272 and 180703) and OECD 422 oral toxicity study (BSL Munich Study No. 178271). In the first 14-day study male and female Wistar rats were treated with the test item at 100, 300 and 1000 mg/kg bw/day for a period of 14 days. Test-item related mortality (3/3 males and 2/3 females) and clinical signs indicating toxicity such as paresis, ataxia, lethargy/stupor, apathy, dehydration, abnormal breathing and haematuria were observed at the highest dose of 1000 mg/kg bw/day.
In the second 14-day study male and female Wistar rats were treated with the test item at doses of 100, 250 and 500 mg/kg bw/day for a period of 14 days. Mortality occurred in 1/3 males at the highest dose of 500 mg/kg bw/day. Also, at that dose level, animals showed signs of renal toxicity, such as a thickened wall of the urinary bladder, dilated ureters and dilated kidneys, increased weights of kidneys and clinical biochemistry markers. A thickened wall of the urinary bladder was also observed at the two lower dose levels of 250 and 100 mg/kg bw/day.
In the OECD 422 study, male and female Wistar rats were treated at doses of 40, 120 and 360 mg/kg bw/day (treated for 28 days in males and 63 days in females). In this study, test item-related lesions were observed in the kidneys, ureters and the urinary bladder at 120 and 360 mg/kg bw/day. The NOAEL for general toxicity in this study was considered to be 40 mg/kg bw/day and for reproductive toxicity screening is considered to be 360 mg/kg bw/day.
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 assess any dose-related response and establish a NOAEL.

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations: morbidity, mortality

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

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

FOOD CONSUMPTION: Yes
- Food consumption measured on GD 5, 8, 11, 14, 17 and 20

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
The dam (presumed pregnant female) 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.

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

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: The position and number of foetuses in each uterine horn was also recorded.

Fetal examinations:

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

Statistics:

A statistical assessment of the results of the body weight 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).

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical signs observed on a few days during the treatment period included skin and fur, hairless area (hind limb/abdomen/inguinal) in one female on GD 14-20 and increased salivation on GD 19 and hairless area (fore limb/hind limb/neck) in another female on GD 9, 10, 13-20 of the high dose group. A third female showed deviations in skin and fur, namely hairless area at right hind limb on GD 17-19. These findings are considered to be of incidental in nature.
Animals nos. 75, 77, 79 and 80 showed moderate increased salivation on GD 18-19, 16 17, 15-16, 12/17-19 respectively in the high dose group. This was observed transiently after dose administration and considered as a clinical sign elicited by local effects of the test item formulation and/or attributed to discomfort of the animals due to oral administration.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Description (incidence):

No mortality was observed during the treatment period and all females 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 by the test item and increased with the progress of the study in the control, low dose and mid dose groups. However lower mean body weights was observed in high dose females with statistical significance seen on GD 14 - 20 (5-6 % below control).
Moderate, but statistically significantly lower mean body weight gain was observed on GD 5-8 and GD 11-14 in the high dose group. The group mean body weight gain of low dose and mid dose groups were comparable to control. However, slightly lower mean body weight gain was observed on GD 0-5 in low dose females and GD 11-14 in mid dose females (19 % and 16 % respectively) without achieving statistical significance.
Overall, statistically significant lower mean body weight gain was observed on GD 5-20 in high dose females when compared to the control (20 % below control), this is considered be a test item-related effect.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

In correlation to lower mean body weight and bodyweight gain, statistically significant lower food consumption was observed in the high dose group on GDs 5-8, 8-11, 11-142 (15-19 % below control). The overall mean food consumption on GDs 5-20 was found to be statistically reduced in the HD group (13 % below control) when compared to control.
The group mean food consumption of LD and MD groups were comparable to control animals

Food efficiency:

not examined

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

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:

no effects observed

Description (incidence and severity):

Statistical analysis of post fixed thyroid/parathyroid weights from all dams revealed no statistically significant or toxicologically relevant effect on the absolute and relative (to body weight) thyroid/parathyroid weights of the dose groups when compared to the control.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Animals no. 30 and 76 showed lungs with abnormal red spotted colour in the low dose group and abnormal red/mottled in the high dose group, respectively. Uteri with abnormal red colour in animal no. 59 and both sides dilated in animals no. 49 and, 61 were observed in the mid dose group and a 2.5 cm mass was observed in ovaries of animal no. 30 of the low dose group. These are considered to be incidental findings and not toxicologically relevant.
Predominant findings of dilated ureter on both sides were observed in animals no. 83, 72, 73, 79, 85, 86, 87, 89, 92; on the right side only in animals no. 84, 88; abnormally shaped, thick ureter in animal no. 75 and thickened wall, urinary bladder in animal no. 79, 92 was observed in the high dose group. All these findings are considered to be test item-related effects.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

There were no test item-related findings at histopathological evaluation of the thyroid gland in any of the treated groups.

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Description (incidence and severity):

In all terminally sacrificed females, no toxicologically relevant effect was observed on group mean T3, T4 and TSH hormone levels and values were comparable with the controls.

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

Changes in pregnancy duration:

not examined

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

Successful mating resulted in 22/23 pregnancies in the lo dose group, 20/23 in the mid dose group and 22/23 in the high dose group compared to 21/23 pregnancies in the control group.

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Net weight change (g) from GD 0 showed a slight trend towards lower mean weight in the HD group compared to the control group (32.8 % below control). As there is no dose-dependency, it is not considered toxicologically relevant. Carcass and uterine weight were found to be comparable to control except for a slight but statistically significant reduction in mean carcass weight in the high dose group (7 % below control).

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

body weight and weight gain

food consumption and compound intake

gross pathology

Abnormalities:

effects observed, treatment-related

Localisation:

other: ureter

Fetal body weight changes:

no effects observed

Description (incidence and severity):

There were no test item-related effects of toxicological relevance observed for the mean foetus weight, male and female foetus weight on litter basis (group mean of individual litter mean) in any of the treatment groups when compared to control.

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

not examined

Changes in litter size and weights:

no effects observed

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 foetuses of treated groups.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Skeletal examination of the Alizarin red stained foetuses revealed a range of findings, which occurred at an incidence generally comparable to or slightly lower or higher in the dose groups, when compared to the control.
Statistically significantly higher foetal incidences were observed at 4th sternebra in the low dose group (8 %) when compared to 2 % in control and at 3rd sternebra in the low dose group (5 %) when compared to control (0 %). Statistically significantly higher foetal incidences were observed in skull supraoccipital with small hole in high dose group (60 % compared to 34 % in control). All these findings were observed without dose dependency or consistency; hence they are not considered to be test item-related.

Higher or lower litter incidences, but without achieving statistical significance, were observed as mentioned below.
Higher or lower litter incidences of unossified forelimb phalanx (low dose, mid dose and high groups, 100% each) were observed compared to 95 % in control. Higher or lower litter incidences of pelvic girdle, caudal shift were observed (30 %, 25 % and 20 % in low dose, mid dose and high dose groups, respectively) when compared to 20% in control. Higher or lower litter incidences of incomplete ossifications of 2nd sternebra were observed (40 %, 15 % and 50 % in low dose, mid dose and high dose groups, respectively) when compared to 45 % in control. Higher litter incidence of incomplete ossification of forelimb humerus and frontal skull (left) was observed in the high group (15 % compared to 5 % in control). Higher or lower litter incidence incomplete ossification of skull parietal (bone) was observed in treated groups (35 %, 40 % and 55 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (35 %).
Higher litter incidence of incomplete ossification of skull frontal (bone) was observed in high groups (15 % compared to 10 % control). Litter incidence of vertebra thoracic centrum, irregular ossification was observed in treated groups (65 %, 70 % and 65 % in the LD, MD and HD groups, respectively) when compared to control group (70 %). Higher or lower litter incidence of forelimb metatarsal, unossified was observed in treated groups (40 %, 25 % and 65 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (45 %). Higher litter incidence of forelimb radius, incomplete ossification-upper extremity (bone) was observed in treated groups (25 % in high dose compared to control (5 %). Higher litter incidences incomplete ossification of skull supraoccipital was observed in treated groups (95 %, 95 % and 100 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (90 %).
Higher litter incidence of 14th Rib, rudimentary was observed in treated groups (45 %, 60 % and 50 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (40%). Higher or lower litter incidence of sternebra (5th) incomplete ossification was observed in treated groups (75%, 65% and 80% in the low dose, mid dose and high dose groups, respectively) when compared to control group (75%). Higher litter incidence of hind limb femur incomplete ossification was observed in treated groups (60 %, 55 % and 75 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (40 %). Higher or lower litter incidence of vertebra cervical centrum, unossified was observed in treated groups (100 %, 90 % and 100 % in the low dose, mid dose and high dose groups, respectively) when compared control group (95 %).
Higher or lower litter incidence of skull orbital socket region, increased ossification was observed in treated groups (65 %, 70 % and 45 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (75 %). Higher or lower litter incidence of skull parietal (right), increased ossification was observed in treated groups (35 %, 20 % and 35 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (30 %). Higher or lower litter incidence of skull parietal (left), increased ossification was observed in treated groups (0 %, 30 % and 20 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (10 %). Higher litter incidence of skull basisphenoid, increased ossification was observed in treated groups (25 % in the mid dose group) when compared to control group (5 %). Higher or lower litter incidence of 14th rib (right), rudimentary was observed in treated groups (50 %, 45 % and 45 % in the low dose, mid dose and high dose groups respectively) and control group (50 %).
Litter incidence of incomplete ossification of 6th sternebra was observed in treated groups (100 % in the low dose and high dose groups and 95 % in mid dose group) when compared to control group (95 %). Higher or lower litter incidence of ribs, wavy was observed in treated groups (30 %, 70% and 65 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (70 %). Higher or lower litter incidence of vertebra cervical arches, irregular ossification was observed in treated groups (35 %, 40 % and 15 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (35 %).
Litter incidence of vertebra sacral centrum and arches fused was observed in treated groups (20 %, 20 % and 5 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (20 %).
Higher or lower litter incidence of vertebra caudal centrum and arches fused was observed in treated groups (25 %, 10 % and 10 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (15 %). Higher or lower litter incidence of pelvic girdle caudal shift (right) was observed in treated groups (20 %, 10 % and 30 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (20 %). Higher or lower litter incidence of vertebra lumbar arches increased ossification was observed in treated groups (5 %, 20 % and 15 % in the low dose, mid dose and high dose groups, respectively) when compared to control group (10 %).
The observed incomplete ossification without achieving statistical significance of a few bones and a few other skeletal findings in the treated groups were either marginally lower or higher or within the historical control data range. Generally delayed ossification is not regarded to persist postnatally and is not associated with long-term consequences on survival, general growth and development and therefore is not considered to be adverse.
There was no statistical significance and no indication of a test item-related trend in the type and/or incidences of other skeletal findings and they were therefore considered to be spontaneous in nature.

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 all groups including 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 concurrent 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.
Higher litter incidences of testes, malpositioned in the high dose group were observed (45 %) when compared to control (30%). There were lower litter incidences of umbilical artery malpositioned (30 %, 25 % and 30 % in the low dose, mid dose and high dose groups, respectively, compared to 45 % in control) observed. There were lower litter incidences of liver, lobe supernumerary (20 %, 30 % and 25 % in low dose, mid dose and high dose groups, respectively, compared to 40% in control) observed. There were lower litter incidences of azygos vein (bilateral) (55 %, 70 % and 40 % in the low dose, mid dose and high dose groups, respectively, compared to 80 % in control observed. There were higher litter incidences of abdomen, internal haemorrhage (55 %, 80 % and 80 % in low dose, mid dose and high dose groups, respectively, compared to 55 % in control) observed. Lower litter incidence of discoloured kidney, thoracic internal haemorrhage and long thymus was observed in the low dose group (5 % each). All these findings are considered to be incidental in nature.

Other effects:

no effects observed

Description (incidence and severity):

In male and female foetuses weight and cube root of foetus weight were comparable to control group and no test item-related findings were observed.
In males and females, the relative anogenital distance (AGD) in low dose and high dose groups, respectively, was statistically significantly lower when compared to the control. There was no dose dependency, as this was observed in low dose and high dose but not in mid dos group. However, all these values are within the historical control values of this strain. Hence, this is not considered to be a test item-related effect.
All male foetuses were checked for indication of incomplete testicular descent/ cryptorchidism and evaluation revealed completion of testicular descent (abdominal) in all male foetuses from all groups.

Craniofacial examination by razor blade serial sectioning technique revealed incidences of head, subcutaneous hematoma in all treated (45 %, 50 % and 45 % in low dose, mid dose and high dose groups) when compared to control (25%). Lower litter incidences of mid brain subdural oedema were observed in all treated (50% in each low dose, mid dose and high dose groups, respectively) when compared to control (65 %). Higher litter incidences of increased subcutaneous space in head was observed in low dose and mid dose groups (10 % and 5 %, respectively) when compared to control (0 %). Higher or lower litter incidences of increased perimeningal space were observed in all treated groups (10 %, 20 % and 10 % in low dose, mid dose and high dose groups, respectively) when compared to control (15 %). All 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.

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no adverse effects observed up to the highest dose tested

Key result

Abnormalities:

no effects observed

Key result

Developmental effects observed:

no

Conclusions:

On the basis of this prenatal developmental toxicity study in Wistar pregnant female rats with triethoxyphenylsilane (CAS 780-69-8) at dose levels of 40, 120, and 400 mg/kg bw/day administered on GD 5 to GD 19, the following conclusions can be made:
No test item-related mortality and clinical signs were observed during the treatment period of this study. Test item-related and statistically significant reductions in mean body weight gain and mean food consumption were observed at the high dose group. No test item-related effects on prenatal and litter data parameters or, thyroid hormone and thyroid/parathyroid organ weights of dam were observed. Test item-related effects on gross pathology of terminally sacrificed high dose females was observed which included dilated ureter on both sides, abnormally shaped and thick ureter and thickened wall of urinary bladder. There were no test item-related findings at histopathological evaluation of the thyroid gland in any of the treated groups. Furthermore, no test item-related and toxicologically relevant external, visceral or craniofacial findings were observed in the treatment groups. However, there were a few skeletal findings including incomplete ossification of some bones and other incidental skeletal findings observed which were not of statistical significance in the high dose group. These findings were either marginally lower or higher or within the historical control data range and not considered to be adverse.
The NOAELs for maternal and foetal toxicity of triethoxyphenylsilane in this study are considered to be 120 mg/kg bw/day and 400 mg/kg bw/day, respectively.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

400 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The study was conducted with the test substance according to the OECD test guideline 414 and in compliance with GLP.

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

A reliable prenatal developmental toxicity study according to OECD 414 is available for triethoxy(phenyl)silane (Eurofins, 2020). The test substance was administered in corn oil (vehicle) at dosages of 40, 120, and 400 mg/kg body weight/day, and controls received the vehicle only during gestation day (GD) 5 to 19.

No test item-related mortality was observed during the treatment period and all animals survived until the end of the study. There was no test item-related or adverse clinical signs of toxicological relevance observed in the females of any treatment group. None of the females showed signs of abortion or premature delivery prior to the scheduled necropsy. The mean body weight remained unaffected by the test item and increased with the progress of the study in the control, LD (40 mg/kg bw/day) and MD (120 mg/kg bw/day) groups. However, lower mean body weights were observed in HD (400 mg/kg bw/day) females with statistical significance seen on GDs 5-8 and GDs14-20. Bodyweight gain was also reduced in the HD group when compared to the control (20% below control) and statistically significant from GD 5 to 20. This was considered be a test item-related effect. In correlation to lower mean body weight and bodyweight gain, statistically significantly lower food consumption was observed in the HD group on GDs 5-8, 8-11, 11-14 (15-19% below control). The overall mean food consumption on GDs 5-20 was found to be statistically reduced in the HD group (13% below control) when compared to control. The group mean food consumptions of the LD and MD groups were comparable to control animals.
No test item-related effects of toxicological relevance were noted for any prenatal parameters including; terminal body weight, adjusted maternal weight (carcass weight), uterine weight, net weight change from GD 0, number of corpora lutea, implantation sites, early and late resorptions, number of live foetuses, anogenital distance, number of male and female foetuses, sex ratios and percent pre- and post-implantation loss in treatment groups when compared to the controls. No dead foetuses were noted in any of the groups.
However, statistically significant reduction in mean carcass weight (7% below control) and Net weight change (g) from Gestation day 0 (33% below control) were observed in HD groups.

Successful mating resulted in 22/23 pregnancies in the LD group, 20/23 in the MD group and 22/23 in the HD group compared to 21/23 pregnancies in the control group. In all terminally sacrificed females, no toxicologically relevant effect was observed on group mean T3, T4 and TSH hormone levels and values were comparable to the controls. 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 dose groups when compared to the control group.
No test item-related gross pathological changes were observed during the macroscopic examination in the LD and MD groups. However, in the HD group there were test item related gross pathological findings observed in the ureter, abnormal shape (thick) in 1/23 females and dilation in both sides in 11/23 females, and urinary bladder thickened wall in
2/23 females. There were no test item-related findings at histopathological evaluation of the thyroid gland in any of the treated groups.

In male and female foetuses, weight and cube root of foetal weight were comparable to control and no test item-related findings were observed. In males and females, the relative anogenital distance (AGD) in the LD and HD groups, respectively, was statistically significantly lower when compared to the control. There was no dose dependency, as this was observed in the LD and HD groups but not in the MD group. However, all these values were within the historical control values of this strain; hence this was not considered to be a test item-related effect. All male foetuses were checked for indication of incomplete testicular descent/cryptorchidism and evaluation revealed completion of testicular descent (abdominal) in all male foetuses from all groups. There were no test item-related effects of toxicological relevance observed for the mean foetal weight, as male and female foetal weights on a per litter basis (group mean of individual litter mean) were not different in any of the treatment groups when compared with the controls. There were no test item-related external abnormalities observed in any of the dose groups. Internal observation of the foetal viscera by free hand microdissection technique revealed a range of visceral findings in all groups including 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 controls. As the observed findings were minor variations and/or lacked 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 with the control. Craniofacial examination by razor blade serial sectioning technique revealed incidences of head, subcutaneous hematoma in all treated groups (45%, 50% and 45% in the LD, MD and HD groups, respectively) when compared to control (25%). Lower litter incidences of mid brain subdural oedema were observed in all treated groups (50% in each LD, MD and HD groups, respectively) when compared to control (65%). Higher litter incidences of increased subcutaneous space in head were observed in the LD and MD groups (10% and 5%, respectively) when compared to control (0%). Higher or lower litter incidences of increased perimeningal space were observed in all treated groups (10%, 20% and 10% in the LD, MD and HD groups, respectively) when compared to control (15%). All these findings were considered to be spontaneous in nature and not related to the treatment with the test item and within the historical control range. Statistical analysis of the data revealed no statistical significance for any of these findings. Skeletal examination of the Alizarin red stained foetuses revealed a range of findings which occurred at an incidence generally comparable to or slightly lower or higher in the dose groups when compared to the control group. Statistically significantly higher foetal incidences were observed at 4th sternebra in the LD group (8%) when compared to 2% in control and at 3rd sternebra in the LD group (5%) when compared to control (0%). Statistically significantly higher foetal incidences were observed in skull supraoccipital with small hole in the HD group (60% compared to 34% in the control). All these findings were observed without dose dependency or consistency and therefore they were not considered to be test item-related. Without achieving statistical significance, the observed incomplete ossification of some
bones and other incidental skeletal findings in the HD group were either marginally lower or higher than concurrent controls or within the historical control data range. Generally,
delayed ossification is not regarded to persist post-natally and is not associated with longterm consequences on survival, general growth and development and, therefore, is not
considered to be adverse. There was no statistical significance and no indication of a test item-related trend in the type and/or incidences of other skeletal findings and they were, therefore, considered to be spontaneous in nature
In conclusion, the NOAELs for maternal and foetal toxicity of triethoxyphenylsilane in this study were considered to be 120 mg/kg bw/day and 400 mg/kg bw/day, respectively.

Furthermore, a reliable combined repeated dose/reproductive and developmental screening study according to OECD 422 is available for triethoxy(phenyl)silane (Eurofins, 2019). The test substance was administered in corn oil as vehicle at dosages of 40, 120, and 360 mg/kg body weight/day, and controls received the vehicle only. Two recovery groups were included which were treated with vehicle only or 360 mg test substance/kg bw/day. 

Treatment-related effects were observed in body weight and food consumption in the high dose group. One male rat from the high dose group with 360 mg/kg bw/day was sacrificed moribund on day 15. The death was considered treatment-related as a consequence of backflow nephrosis. At necropsy adverse effects in kidneys and urinary bladder were observed at 120 and 360 mg/kg bw/day. The systemic toxicity is described in detail under the chapter “repeated dose toxicity”.

There were no effects on litter data, litter weight data, pre and post-natal data, pup survival data, anogenital distance and nipple retention, pup thyroid weight and thyroid hormone analysis in parental males and pups sacrificed on PND 13 and male sacrificed at the end of recovery period and pup external findings in all groups up to 360 mg/kg bw/day.

A very slight and dose-dependent tendency towards lower a serum thyroxine hormone (T4) level was observed in PND 13 pups of the dose groups when compared to controls. A relation to treatment with the test item cannot be excluded.

Based on the findings in the urinary tract, the NOAEL for triethoxy(phenyl)silane in this study for general toxicity is considered to be 40 mg/kg bw/day. As no effects were observed in any developmental toxicity aspects, the NOAEL for developmental toxicity is considered to be 360 mg/kg bw/day.

Justification for classification or non-classification

The available data on toxicity to reproduction of the test substance do not meet the criteria for classification according to Regulation (EC) 1272/2008, and are therefore conclusive but not sufficient for classification.

No information is available on effects via lactation.