Triethoxy(phenyl)silane

Endpoint summary

Description of key information

Oral (subacute):
Repeated dose toxicity: OECD TG 422 in rats: NOAEL = 40 mg/kg bw/day.

Inhalation (subacute):
Repeated dose toxicity: OECD TG 412 in rats: NOAEC > 620 mg/m³.
No systemic toxicity was observed after repeated exposure to concentrations up to 620 mg/m³.

Dermal toxicity: no measured data are available

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental toxicity screening

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: no
- 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 oral 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 (if other than water): 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

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 in males and up to 63 days in 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

Observations and examinations performed and frequency:

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

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

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

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes; parameters checked in table 1 were examined
- Time schedule for collection of blood: as part of sacrifice
- Anaesthetic used for blood collection: ketamine/xylazine
- Animals fasted: not reported
- How many animals: 5

CLINICAL CHEMISTRY: Yes; parameters checked in table 2 were examined
- Time schedule for collection of blood: as part of sacrifice
- Animals fasted: not reported
- How many animals: 5

URINALYSIS: Yes; parameters checked in table 3 were examined
- Time schedule for collection of urine: Prior to sacrifice
- Metabolism cages used for collection of urine: Not specified
- Animals fasted: Not specified
- Urine colour/ appearance was recorded.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: 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)
- Dose groups that were examined: all dose groups
- Battery of functions tested included: 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).

IMMUNOLOGY: No

Sacrifice and pathology:

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 the tables below were prepared for microscopic examination and weighed, respectively.

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.

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 low-dose 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.

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 cont rol 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 treatm ent period and % reticulocytes in high-dose males at the end of the recovery period, were not consi dered 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

Description (incidence and severity):

At the end of the treatment period statistically significantly higher relative kidney weights in high-dose females were observed when compared to the control group (22% above controls). The relative kidney weight of high-dose males was also higher (22% above controls) when compared to control, although not statistically significant. In the presence of histopathological findings in these organs the effect on organ weights at the end of treatment period was considered to be adverse. No considerable difference in kidney weight was observed at the end of the recovery period.

Males and females sacrificed at the end of treatment period, showed statistically significantly lower absolute and relative thymus weights in high dose (77% and 76% in males and 47% and 42% in females below controls, respectively). This was associated with thymic atrophy found histopathologically in this dose group.

A statistically significantly lower absolute weight of prostate gland with seminal vesicles and coagulating gland in the high-dose male group (19% below controls) is not assumed to be toxicologically relevant as it was not associated with histopathological findings or reduced fertility in this study.

A slightly but not statistically significantly higher relative weight of adrenal glands was observed in high-dose males (32% above controls).

A tendency towards increased liver weight (approx. 10% above controls) was observed in high- and mid-dose females.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Test item-related gross lesions were noted mainly in the kidneys, ureters and urinary bladders. Males were more affected than females. The findings consisted mainly of renal pelvis dilatation (in one decedent recovery male it was described as enlarged kidney and abnormal consistency), ureter dilatation, and thickening of the urinary bladder wall.

Treatment-related macroscopic finding were as follows:
In males, main macroscopic changes were: kidneys - abnormal consistency, abnormal content, enlarged kidneys and pelvis dilatation in high-dose males (8/10) and low/mid-dose males (2/10). Ureter dilatation was observed in high-dose (10/10), mid-dose (3/10) and high-dose recovery (1/6) males. Thickened wall of urinary bladder was observed in high-dose males (5/10).Thickened wall of urinary bladder was observed in high-dose females (6/10).

The thymus was found to be abnormally colored, enlarged, small with a focus in high-dose (1/10), mid-dose (4/10), and low-dose (3/10) males; however, this effect also was observed in the control group (5/10). In females, thymus was found to be abnormally colored in the low-dose group (1/10), enlarged in the control group (1/10) and the low-dose group (1/10) and with a focus in the recovery control group (1/6) and in the high-dose recovery group (1/6). The presence of these thymus findings in control animals suggests no relation to the test item.

Abnormally colored (red) mandibular lymph node was observed in control (1/10), low-dose (3/10) and mid-dose (1/10) group, a single red, hard mass of approx. 1 cm diameter in epididymis of control rats (1/10), yellow fluid filled thoracic cavity in the low-dose (1/10) group, fluid filled heart - pericardium, in the low-dose (1/10), abnormal color in lung in the low-dose group (1/10) and high-dose group (1/10). These changes in males and females were within the range of normal background alterations which may be recorded in animals of this strain and age and histopathological evaluation revealed that these gross lesions could not be attributed to treatment with the test item.

At the end of the recovery period few foci on the thymus of single animals of the control and high-dose groups were found. They were not associated with histopathological findings and are not assumed to be test item-related. Besides, there were no macroscopic findings at the end of the recovery period.

Neuropathological findings:

not examined

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

Details on results:

See background material.

Key result

Dose descriptor:

NOAEL

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

gross pathology

histopathology: non-neoplastic

organ weights and organ / body weight ratios

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

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 systemic effects at the low dose of 40 mg/kg bw/day based on effects at the urinary system.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

40 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

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

System:

urinary

Organ:

bladder

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Dose descriptor:

NOAEC

Effect level:

>= 80 ppm (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested

Dose descriptor:

NOAEC

Effect level:

>= 620 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested

Critical effects observed:

no

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

620 mg/m³

Study duration:

subacute

Experimental exposure time per week (hours/week):

32.5

Species:

rat

Quality of whole database:

The study was conducted with a structural analogue substance according to a protocol that is comparable to the OEDCD TG 412. It was not compliant with GLP.

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Dose descriptor:

NOAEC

Effect level:

>= 80 ppm (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested

Dose descriptor:

NOAEC

Effect level:

>= 620 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested

Critical effects observed:

no

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

620 mg/m³

Study duration:

subacute

Species:

rat

Quality of whole database:

The study was conducted with a structural analogue substance according to a protocol that is comparable to the OEDCD TG 412. It was not compliant with GLP.

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

For the oral route, 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. 

One rat from the high dose group with 360 mg/kg bw/day was sacrificed moribund on day 15. As to histopathological evaluation, it is assumed that the moribund condition of the animal was a consequence of backflow nephrosis and considered to be treatment-related. There were no treatment-related clinical signs throughout the treatment period up to 360 mg/kg bw/day. There were no treatment-related functional observation changes at the end of the treatment and recovery periods. Treatment-related adverse effects of the test item were found on male and female body weight and food consumption mainly at 360 mg/kg bw/day. Haematology and coagulation, clinical biochemistry, and urinalysis parameters were not affected by the treatment in both genders. At scheduled necropsy, treatment-related gross macroscopic findings were noted in kidneys and urinary bladder. Changes in respective organ weights are considered to be treatment related at 120 and 360 mg/kg bw/day. Test item-related gross lesions consisted in the kidneys of renal pelvis dilatation (in one decedent recovery male it was described as enlarged kidney and abnormal consistency). Histologically, the incidence of pelvic dilatation increased in males at 40 up to 360 mg/kg bw/day, and tubular dilatation was noted in almost all males at 360 mg/kg bw/day. The findings at 120 and 360 mg/kg bw/day, degenerative and inflammatory lesions consisted of increased incidences and/or severities of tubular basophilia, pyelitis, and, at 360 mg/kg bw/day, of interstitial inflammation, interstitial fibrosis and papillary necrosis. Furthermore, there was urothelial hyperplasia in two males at 120 mg/kg bw/day, and in all males and four females at 360 mg/kg bw/day. Males were more affected than females. The findings were still present after the recovery period.

Pelvic dilatation is common in rats, as are the single incidences of tubular basophilia at minor severity degrees. Therefore, findings at 40 mg/kg bw/day are not considered to be test item-related. There were also ureter dilatation and thickening of the urinary bladder wall noted at necropsy. Histologically, these alterations correlated with the ureters of one male at 120 mg/kg bw/day, and with all males and three females at 360 mg/kg bw/day to dilatation, associated in some cases at 360 mg/kg bw/day with mucosal and/or muscularis hyperplasia, and/or inflammation. The highest degree of mucosal hyperplasia was noted at the most distal portions of the ureters.

In the urinary bladder, there was 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 moderate hyperplasia accompanied by a minimal subacute inflammation. At some locations, in mucosal folds, precipitation of an unknown material was seen. The precipitation was noted by chance only due to the unusual circumstances of observing the urethra within the prostate gland. This finding explains the higher grading of urothelial hyperplasia at more distal parts of the urinary system. Precipitation is deemed to cause irritative effects to the urothelium that causes backflow nephrosis with dilatation of the renal pelvis (hydronephrosis) and tubular dilatation (nephrohydrosis).

Stress-related lesions were noted in the adrenals by cortical hypertrophy and in the thymus by increased thymic atrophy.

Based on the findings in the urinary tract, the NOAEL for triethoxy(phenyl)silane in this study for general toxicity is be considered to be 40 mg/kg bw/day.

Furthermore, for the oral route, a reliable OECD 422 combined repeated dose/reproductive and developmental screening study is available for trimethoxyphenylsilane (CAS 2996-92-1). This study is a valid investigation of the toxicological effects resulting from repeated oral-gavage administration of the test item to male and female rats for at least 28 days. The test item was administered in dried and deacidified corn oil as vehicle at dosages of 100, 250, and 500 mg/kg body weight/day, and controls received the vehicle only. At 250 mg/kg bw/day, treatment with the test item caused an increase in the concentration of urea and bile acids. Multifocular tubular degeneration/regeneration and transitional hyperplasia of kidney were noted in males and females. During the macroscopic examination, the urinary bladder was observed to be thickened in males and females at all dose levels. This correlated with the findings noted at the microscopic level. At all dose levels (100, 250 and 500 mg/kg bw/day) during the histopathology examination, perivascular lymphoid cell infiltration and transitional cell hyperplasia of the urinary bladder were observed in males and females. Therefore, based on the findings in urinary bladder noted in all test item-treated groups, a general NOAEL could not be established. The LOAEL was 100 mg/kg bw/day (SEHSC, 2009).

Comparing the findings in the screening study with both substances it can be seen that their target organ is the same and their toxicity is in the same range. Thus, read across between both substances can be justified.

Inhalation

In a key study, an acceptable repeated inhalation toxicity study similar or equivalent to the OECD TG 412, but not in compliance with GLP, the test item – trimethoxypehnylsilane (CAS 2996-92-1) was administered to Sprague-Dawley rats (10 per sex and dose) by whole body exposure at analytical concentrations of 9.5, 52.4, and 76.5 ppm, corresponding to 0.077, 0.425, and 0.620 mg/l for 6.5 hours per day, 5 days/week for a total of 28 days. Due to an accident in the mid dose group, an additional experiment was performed with 0.401 mg/l (analytical concentration).

There were no compound related effects in mortality, clinical signs, body weight, food consumption, haematology, clinical chemistry, organ weights, or gross and histologic pathology.

Based on no systemic toxicity after repeated exposure to concentrations up to 0.62 mg/l, the NOAEC was set at >620 mg/m³, which was the highest dose tested (Bio-Research Laboratories, 1980).

Justification for classification or non-classification

Following oral exposure with the test substance triethoxy(phenyl)silane there were signs of adverse effects in the urinary tract of rats starting at 120 mg/kg bw/day and therefore the test substance has to be classified for STOT-RE Cat 2, with the hazard statement 'H373: May cause damage to organs' according to Regulation (EC) 1272/2008.