Trimethoxyvinylsilane

Endpoint summary

Description of key information

In the key oral repeated dose study (combined repeated dose toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP (Hashima Laboratory, 2005)), administration of trimethoxy(vinyl)silane to rats at dose levels of 62.5, 250 or 1000 mg/kg bw/day lead to significant histopathological changes in the urinary bladder of males and females, which were not reversible at the end of the recovery period, in the higher dose groups of 250 and 1000 mg/kg bw/day. Administration of 62.5 mg/kg bw/day did not lead to organ damage including irreversible morphological effects permanently impairing the function of the organ/tissue (reversibility after recovery period). Also, no other effects such as necrosis or other cell death were reported, which could contribute to the degeneration of the metabolically functional tissue. The No Observed Adverse Effect Level (NOAEL) was therefore determined to be 62.5 mg/kg bw/day. The Lowest Observed Adverse Effect Level (LOAEL) was 250 mg/kg bw/day, based on the histopathological changes in the urinary bladder observed in all animals (males and females) at this dose level.

For purposes of identifying the oral CSA value, the systemic NOAEL of 40 mg/kg bw/day from the extended one-generation reproductive toxicity study (EOGRTS, OECD Test Guideline 443) is selected. As discussed further in Section 5.9.3 Summary and discussion of reproductive toxicity, the NOAEL for systemic toxicity for the parental (P0 and P1 [F1 Cohort 1B]) animals in this study was concluded to be 40 mg/kg bw/day based on test substance-related effects in the urinary system (kidney, bladder) at 100 and 300 mg/kg bw/day (BSL Bioservice, 2021).

In the key 14-week whole-body inhalation study (Bushy Run Research Center, 1990), conducted using a protocol similar to OECD Test Guideline 413 and in compliance with GLP, in which rats were exposed to nominal concentration of trimethoxy(vinyl)silane at 10, 100 or 400 ppm, minimal to mild alterations in body weight, water consumption, urinalysis, organ weights, and bladder and kidney histopathology were observed at the highest concentration of 400 ppm. The clinical chemistry findings in males at 400 mg/kg bw/day (lower osmolarity and electrolyte concentrations, and decreased creatinine clearance) are consistent with the renal histopathology at this dose. At a concentration of 100 ppm there were some body weight gain reductions in females, but they were less than 10% and not always statistically significant, and there were no such finding in males; males had mild effects on urine osmolality and urine volume in week one only and there were no associated organ weight changes, macroscopic or microscopic findings. There were no findings at the end of the recovery period. Therefore, the findings at 100 ppm were concluded not to be adverse and the NOAEC in Fischer 344 rats was therefore 100 ppm (equivalent to 605 mg/m³).

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

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)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories Japan, Inc., Yokohama, Japan
- Age at study initiation: 9 weeks
- Weight at study initiation: males: 317 - 423 g, females: 250 - 277 g
- Fasting period before study: no fasting period
- Housing: individual in stainless steel cages
- Diet (e.g. ad libitum): CRF-1, pelleted, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: at least 17 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 - 24 °C
- Humidity (%): 41 - 71%
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Dosing solutions were prepared more than once a week. Concentration of stock solution was 200 mg/ml and stored at 4 °C in a refrigerator. The stock solution was diluted with corn oil to achieve the concentration of the dosing solutions.

VEHICLE
- Lot/batch no.: V3T0416 and V4K3008

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration of dosing solution was verified by GC at the study initiation and at the end of the study. The range of concentration was acceptable because it was between 93.6 - 101.2%.

Duration of treatment / exposure:

Male: 14 days before mating, 28 days thereafter (42 days)
Females for repeated dose study: 42 days
Females in mating groups: 14 days before mating, during mating, during resulting pregnancies, 6 days during lactation (44 - 58 days)

Frequency of treatment:

daily

Dose / conc.:

62.5 mg/kg bw/day (nominal)

Dose / conc.:

250 mg/kg bw/day (nominal)

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

(Males)
6 males/dose
for satellite group: 6 males/dose

(Females for satellite group)
Control, 250 mg/kg b.w., 1000 mg/kg b.w.: 6 females/dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose levels were based on the results of a foregoing range finding study, in which animals were orally exposed to 0, 250, 500 and 1000 mg/kg bw/day (Hashima, year not available, 401223P). No mortality was observed in all groups. Reddish urine, decrease in food consumption and occult blood was observed in administered groups. Therefore, 62.5, 250 and 1000 were selected as the dose levels for the main study.

Post-exposure period: Yes, for a sub group of males and females for 14 days

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice a day during administration period, daily during recovery period, and once before necropsy

DETAILED CLINICAL OBSERVATIONS: Yes (including FOB)
- Time schedule: once before administration, Day 7, 14, 21, 28, 35 and 41 (males)
- Time schedule: once before administration, Day 8 and 15 of administration; Day 1, 8 and 15 of gestation; Day 3 of lactation
- Time schedule: once before administration, Day 8, 15, 22, 29, 36 and 42 (females for satellite group)

BODY WEIGHT: Yes
- Time schedule for examinations: twice a week
Males and satellite females: Day 1, 4, 8, 11, 15, 18, 22, 25, 29, 32, 36, 39 and 42 during administration period, Day 1, 4, 8, 11, 14 and 15 during recovery period
Pregnant females: Day 1, 4, 8, 11, 15 and 18, Day 0, 7, 11 and 21 during gestation, Day 0, 4, 6 and 7 during lactation

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

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on day after last administration or after recovery period
- Anaesthetic used for blood collection: Yes (Pentobarbital-Na)
- Animals fasted: Yes
- How many animals: all administered animals
- Parameters checked: RBC, Haemoglobin, Haematocrit, MCV, MCH, MCHC, Platelets, Reticulocytes, PT, APTT, Fibrinogen, WBC, Differential leukocytes: Lymphocyte, Neutrophils, Eosinophils, Basophil, Monocyte

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on day after last administration or after recovery period
- Animals fasted: Yes
- How many animals: all administered animals
- Parameters checked: AST, ALT, ALP, gamma-GTP, T-protein, Albumin, A/G, T-bilirubin, Urea nitrogen, Creatinine, Glucose, T-cholesterol, Triglycerides, Na, K, Cl, Ca, Inorganic-P

URINALYSIS: Yes
- Time schedule for collection of urine: on Day 2 and 37 in fasted males, Day 3 and 38 in non-fasted males, Day 2 during administration period and Day 5 of lactation in fasted females, Day 3 during administration period and Day 6 of lactation in non-fasted females, after recovery period in females
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes/No
- Parameters checked: Colour, pH, Protein, Glucose, Ketone body, Bilirubin, Occult blood, Urobilinogen, Urinary sediments, Epithelial cells, Erythrocytes, Leukocytes, Casts, Crystals

Sacrifice and pathology:

ORGAN WEIGHT: Yes: Brain, pituitary, thyroids, thymus, heart, liver, spleen, kidney, adrenals, testes, epididymides, ovaries, uterus, lung
GROSS PATHOLOGY: Yes: heart, lung, trachea, liver, pancreas, sublingual gland, submandibular gland, oesophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, thymus, spleen, submandibuar lymph node, mesentric lympha node, kidney, urinary bladder, testis, epididymis, seminal vesicle, prostate, ovary, uterus, pituitary, adrenal, thyroid, parathyroid, cerebrum, cerebellum, medulla oblongata, spinal code, sciatic nerve, eyeball, Harderian gland, bone (sternum or femur), and mammary gland
HISTOPATHOLOGY: Yes: heart, lung, trachea, liver, pancreas, sublingual gland, submandibular gland, oesophagus, stomach, duodenum, jejunum, ileum. cecum. colon, rectum, thymus, spleen, submandibuar lymph node, mesentric lympha node, kidney, urinary bladder, urethra, ovary, uterus, pituitary, adrenal, thyroid, parathyroid, cerebrum, cerebellum, medulla oblongata, spinal code, sciatic nerve, eyeball, Harderian gland, bone (sternum or femur), bone marrow (sternum or femur), and mammary gland

Statistics:

Bartlett test, Dunnett test, chi-square test, Cochran-Armitage test

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg bw/day: mortality occurred
Transient salivation, soiled hair, a decrease in locomotor activity, reddish urine, hypothermia, perioral smudges, perianal soiling, diarrhoea, bradypnea, and piloerection were noted in the dying animals. Transient salivation, soiled hair and reddish urine were noted in the surviving males and females of the 1000 and 250 mg/kg groups.

Mortality:

mortality observed, treatment-related

Description (incidence):

1000 mg/kg bw/day: mortality occurred
Two males and 1 female from the 1000 mg/kg bw/day group died on Day 16 and 17 of males and Day 8 of female.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg bw/day: reduced body weight
Low body weights were noted in males on Day 4 to 42 during administration period and Day 1 and 4 during recovery period. No changes were detected in females during administration period and recovery period.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption was decreased on Day 2 in males of 62.5 and 250 mg/kg bw/day group and on Day 2, 5 and 9 of males in 1000 mg/kg bw/day. Males in 62.5 mg/kg bw/day group and 250 mg/kg bw/day group showed more food consumption on Day 9 and 5, respectively. Increased food consumption was also observed in males of 1000 mg/kg bw/day on Day 5, 9 and 12 in recovery period. These increase was not observed as a toxicity effect of the test item, since no change was observed in body weight.

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg bw/day: reduced Hb concentration
Decreased red blood cell counts, haemoglobin concentrations, hematocrit, MCV, and MCH and increased fibrinogen concentrations were noted in males of the 1000 mg/kg bw/day group after administration period. Prolonged APTT was observed in males of 62.5 mg/kg after recovery period. This change was no regarded as a tox effect of the test item due to lack of dose-responsibility. Red blood cell counts, haemoblobin, hematocrit were decreased and reticulocytes were increased in males administered with 1000 mg/kg bw/day. Besides, decreased fibrinogen were observed in 250 and 1000 mg/kg administered males. However, this change disappeared after recovery period. This change was not caused by the test item.

Lower hematocrit in females of the 1000 and 250 mg/kg bw/day groups, and decreased haemoglobin concentrations and prolonged APTT in females of the 1000 mg/kg bw/day group were also noted after administration period. Decreased MCV and MCH was detected in females of 250 mg/kg bw/day after recovery period. Decreased MCV, MCH, MCHC and RBC were also observed in females of 1000 mg/kg bw/day group.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg bw/day: TP reduced in males/females
Increased CL was observed in males of 62.5 mg/kg bw/day after administration period. However, dose- responsibility was not noted. Low total protein, albumin, A/G ratios, and potassium, and high g-GTP, urea nitrogen, and creatinine were noted in males of the 1000 mg/kg bw/day group after administration period. The change of g-GTP was not caused by the test item because no changes of liver was detected by the histopathological findings. Lower AST was detected in males of 250 and 1000 mg/kg bw/day after administration period but this was not regarded as a tox effect of the test item.

Decreased total protein and increased A/G ratio was detected in males of 1000 mg/kg bw/day after recovery period. Increased chloride was noted in males of 1000 mg/kg bw/day after recovery period but this was not caused by the test item due to the range of background data (106.4 ± 1.9 mEq/l). Inorganic phosphate was increased in same group. This change was not considered as a tox effect of the test item, since this was not observed after administration period.

Low total protein and triglycerides in females of the 1000 mg/kg bw/day group were noted after administration period, and a tendency for high g-GTP in females of the 1000 and 250 mg/kg bw/day groups was observed. The decrease in t-bilirubin was not considered as a tox effect of the test item in females of 1000 mg/kg after administration period. Decreased in total protein was observed in females of 1000 mg/kg bw/day after recovery period. Increased ALP and Cl observed in females of 1000 mg/kg bw/day was not caused by the test item, since this data was similar to the background data of this test facility (ALP: 242.7 ± 1012.4 IU/l, Cl: 107.7 ± 2.1 mEq/l).

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg bw/day: occurrence of blood and epithelial cells
Males on Day 2 before administration: increased volume and decreased specific gravity, occult blood positive, epithelial cells and erythrocytes were noted in 1000 mg/kg bw/day. 250 mg/kg bw/day groups showed occult blood and erythrocytes.
Females on Day 2 before administration: increased volume and decreased specific gravity, occult blood positive, erythrocytes and leukocytes were noted in 1000 mg/kg bw/day. 250 mg/kg bw/day groups showed occult blood and erythrocytes.
Males on Day 3 after administration: 250 mg/kg bw/day groups showed white turbidity, occult blood and erythrocytes. White turbidity, occult blood, erythrocytes and leukocytes were observed in 1000 mg/kg bw/day.
Females on Day 3 after administration: 250 mg/kg bw/day groups showed white turbidity, occult blood and erythrocytes. White turbidity, occult blood, erythrocytes and epithelial cells were observed in 1000 mg/kg bw/day.
Males on Day 37 before administration: Decreased specific gravity, occult blood, epithelial cells, erythrocytes and leucocytes were observed in 1000 mg/kg bw/day.
Females on last day before administration: Epithelial cells were observed in 250 mg/kg bw/day and erythrocytes and leucocytes were observed in 1000 mg/kg bw/day.
Males on Day 37 after administration: 250 mg/kg bw/day groups showed white turbidity, erythrocytes and leucocytes. White turbidity, occult blood, erythrocytes and leucocytes were observed in 1000 mg/kg bw/day.
Females on last day after administration: Leucocytes were found in 1000 mg/kg bw/day.
Males and females after recovery period: No changes were observed.

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

Salivation was observed in males and females of 1000 mg/kg bw/day after administration. Ease of removal from cage was decreased in 250 mg/kg bw/day but this was observed before administration. Salivation was observed in 1000 mg/kg bw/day. No changes were noted in both sexes regarding sensory response and grip strength. Increased spontaneous motor activity was noted in males 250 mg/kg bw/day but this was not regarded as a specific toxic effect due to lack of dose response. No change of spontaneous motor activity was reported in females.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

reduced thymus weight (females, all dose groups)
Body weight of males in 1000 mg/kg bw/day after administration period was increased. Decrease in absolute weight of thymus, increase in absolute weight of kidney, increase in relative weight of spleen, kidney and adrenals were observed in males of 1000 mg/kg bw/day after administration period. In same group, decrease in absolute weight of pituitary was also observed but this was not caused by the test item, since no change was detected in its relative weight. Absolute weight of brain was also increased. However, this change was not regarded as compound-related effect but caused by the difference of body weight.
No changes in body weight were detected in females after administration groups. Relative weight of thymus was decreased in females of 62.5 and 250 mg/kg. Decreased absolute weight of thymus, decreased relative weight of thymus and increased relative weight of liver were observed in females after administration period.
No changes of body weight was detected in males after recovery period. Decreased absolute weight of pituitary and increased relative weight of heart was observed in males in 62.5 mg/kg bw/day. However, these changes were not considered as a toxic effect of the test item, since there was no dose-response. Absolute weight of kidney was increased in males of 250 mg/kg bw/day but this was not caused by the test item due to lack of dose dependency. Relative weight of kidney was increased in males. Absolute weight of pituitary was also decreased. This was not caused by the test item because no change was detected in relative weight.
No changes of body weight were found in females after recovery period. Increased absolute and relative weight of uterus were observed in 250 and 1000 mg/kg bw/day after recovery period. However, these changes were not caused by the test item since no changes were observed after administration period. Furthermore, these data was similar to the background data of the test facility (absolute weight: 672 mg, relative weight: 229 mg (%)).

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg bw/day: kidney enlargement
Two dead male animals in 1000 mg/kg bw/day showed atrophy of thymus and spleen. One dead male animal in 1000 mg/kg bw/day showed enlargement of kidneys and dark read glandular mucosa were noted in males of the 1000 mg/kg bw/day group. Enlargement of kidney was observed in four males in 1000 mg/kg bw/day after administration period. Atrophy of spleen was observed in one male of control group after recovery period.
One dead female showed atrophy of thymus and spleen in 1000 mg/kg bw/day. One female in 1000 mg/kg bw/day showed the enlargement of kidney. This was related to hydronephrotic kidney which was observed by histopathological examination and accidentally occurred. No abnormalities were found in females after recovery period.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

250 mg/kg bw/day: hyperplasia (urinary bladder)
In dead males in 1000 mg/kg bw/day, two animals showed postmortal change in whole organs and tissues. One dead male showed vacuolization of lamina propria in jejunum, one male showed hyperplasia of transitional epithelium in kidney, two males showed slight hyperplasia of transitional epithelium in urinary bladder, two males showed hyperplasia of transitional epithelium in urethra, one animal showed atrophy of seminiferous tubule in testis and one animal showed cell debris in lumen in epididymis.

One death occurred in females in 1000 mg/kg bw/day. The dead animal showed moderate postmortal change in whole organs and tissues, slight cellular infiltration of heart, slight hyperplasia of transitional epithelium in kidney and slight hyperplasia of transitional epithelium in urinary bladder. However, these observed changes in dead males and female were not marked. Death was caused by deteriorating general conditions by the test substance.

Histopathological findings after administration and recovery phase are listed in Tables.

On histopathological examination, hyperplasia of transitional epithelium in the urinary bladder was noted in males at all doses. The effect seemed to be substance-related and followed a dose-response relationship. The incidence of hyperplasia in the 250 and 1000 mg/kg bw/day groups was statistically significantly increased up to the end of the recovery period, although a slight decrease (mild to slight) in severity was observed from end of administration period to the end of the recovery period. Hyperplasia that was observed in 2/6 male rats of the 62.5 mg/kg bw/day group after the administration period seemed to be treatment-related, as there were no incidences in the control group; hyperplasia was not observed in the urinary bladder of females in the 62.5 mg/kg bw/day group. In general, hyperplasia in the urinary tract/bladder is not a typical spontaneous lesion, but simple hyperplasia may also occur in untreated animals. Often it is a secondary effect provoked by inflammation or physical damage. The effects observed in males at 62.5 mg/kg bw/day were not evaluated as adverse, as the incidence was not increased statistically significantly and the severity of the effect was stated as "slight". In addition the effects were fully reversible within the recovery period.

Histopathological findings: neoplastic:

no effects observed

Dose descriptor:

NOAEL

Effect level:

62.5 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Critical effects observed:

yes

Lowest effective dose / conc.:

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

System:

urinary

Organ:

bladder

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Table 1: Body weights of male and female rats of the administration and recovery period.

Group	Control	Test substance
mg/kg	0	62.5	250	1000
Number of males	12	12	12	12
Days of administration
1	399±13	399±15	400±15	400±15
11	430±16	417±14	420±23	392±27**
22	456±18	446±20	447±27	417±21**
32	491±21	481±21	479±26	440±22**
42	516±26	498±27	496±28	447±13**
Number of males	6	6	6	6
Days of recovery
1	518±29	511±34	508±25	449±16**
4	524±30	516±36	518±23	472±24*
8	531±30	527±38	528±22	489±26
14	542±32	536±38	541±26	511±35
Number of females	6		6	6
Days of administration
1	266±10		264±8	266±10
42	331±25		313±9	317±27
Number of females	6		6	6
Days of recovery
1	328±26		314±13	316±26
14	340±25		329±16	334±19

Significantly different from control group (*: p<0.05; **: p<0.01)

Table 2: Haematology results of male and female rats after the administration period.

Group	Control	Test substance
mg/kg	0	62.5	250	1000
Number of males	6	6	6	5
At termination of administration period
RBC (10^4/µl)	836±43	829±34	813±32	755±59*
HGB (g/dl)	15.4±0.9	15.3±0.6	14.9±0.5	13.3±1.1**
HCT (%)	45.5±2.4	45.4±1.8	44.2±2.0	39.5±3.6**
MCV (fl)	54.5±1.5	54.7±1.1	54.4±0.8	52.3±1.6*
MCH (pg)	18.4±0.6	18.5±0.4	18.4±0.2	17.7±0.4*
MCHC (g/dl)	33.9±0.4	33.7±0.4	33.8±0.5	33.7±0.4
PLT (10^4/µl)	94.1±9.3	92.6±2.3	96.1±14.1	95.1±9.2
RET (‰)	26±5	23±4	27±4	23±5
PT (sec.)	16.1±1.9	18.0±2.3	16.6±2.4	16.1±1.9
APTT (sec.)	22±1.4	23.5±2.0	21.1±2.1	21.8±2.0
Fbg (mg/dl)	210.6±10.5	223.2±13.3	210.8±17.8	263.4±8.4**
WBC (10²/µl)	72±18	55±5	68±18	102±35
Number of females	6	6	6	6
At termination of administration period
RBC (10^4/µl)	714±25	725±11	687±36	697±33
HGB (g/dl)	14.3±0.5	14.3±0.5	13.8±0.4	13.5±0.6*
HCT (%)	42.1±1.1	41.6±1.4	39.9±1.6*	39.5±1.5*
MCV (fl)	59±2.4	57.4±2.1	58.1±1.4	56.7±1.0
MCH (pg)	20.1±0.8	19.7±0.8	20±0.7	19.3±0.4
MCHC (g/dl)	34.1±0.4	34.3±0.2	34.5±0.5	34±0.6
PLT (10^4/µl)	103.3±6.0	101±7.5	105.8±8.5	95.2±15
RET (‰)	56±12	53±12	60±12	62±24
PT (sec.)	13.8±0.4	13.8±0.3	14.1±0.4	13.6±0.6
APTT (sec.)	17.3±0.8	18±0.6	18.4±1.1	18.8±0.7**
Fbg (mg/dl)	210.4±18.6	214.6±16.2	237.5±57.6	189.2±7.3
WBC (10²/µl)	52±15	52±6	53±18	48±9

Significantly different from control group (*: p<0.05; **: p<0.01)

Table 3: Organ weights of male and female rats after the administration period.

Group	Control	Test substance
mg/kg	0	62.5	250	1000
Number of males	6	6	6	5
At termination of administration period
Body weight (g)	496±24	474±13	469±33	422±18**
Brain (g)	2.08±0.08	2.11±0.09	2.08±0.07	2.07±0.05
(g%)	0.42±0.03	0.44±0.03	0.45±0.03	0.49±0.02**
Pituitary (mg)	13.9±0.7	14.3±1.4	13±0.7	11.8±1.2**
(mg%)	2.8±0.2	3±0.3	2.8±0.2	2.8±0.3
Thymus (mg)	287±43	241±43	323±41	189±38**
(mg%)	58±8	51±10	69±9	45±10
Spleen (mg)	777±99	752±115	723±136	832±136
(mg%)	156±16	159±25	154±23	196±25*
Kidney (g)	3.14±0.25	3.14±0.36	3.1±0.18	4.27±0.99*
(g%)	0.63±0.03	0.66±0.06	0.66±0.05	1.01±0.25**
Adrenals (mg)	55.4±7.7	60.3±7.4	60.6±4.4	61.1±4.9
(mg%)	11.2±1.6	12.7±1.5	13±1.3	14.5±1.7**
Number of females	12	11	11	10
Body weight (g)	302±17	312±18	311±19	286±19
Thymus (mg)	307±56	256±66	247±60	170±52**
(mg%)	103±22	82±19*	80±21*	59±16**
Liver (g)	9.48±0.78	10.01±0.65	10.11±0.99	9.86±0.87
(g%)	3.14±0.17	3.21±0.16	3.25±0.19	3.44±0.19**

Significantly different from control group (*: p<0.05; **: p<0.01)

 

Table 4: Organ weights of male and female rats after the recovery period.

Group	Control	Test substance
mg/kg	0	62.5	250	1000
Number of males	6	6	6	5
At termination of recovery period
Body weight (g)	519±29	513±36	514±23	483±33
Pituitary (mg)	17.3±1.1	15±1.3*	16.1±2.3	14.9±1*
(mg%)	3.3±0.2	2.9±0.4	3.1±0.5	3.1±0.2
Heart (g)	1.46±0.14	1.61±0.14	1.49±0.08	1.48±0.07
(g%)	0.28±0.02	0.31±0.02*	0.29±0.02	0.31±0.02
Kidney (g)	3.08±0.13	3.33±0.18	3.36±0.25*	3.28±0.13
(g%)	0.6±0.04	0.65±0.05	0.65±0.03	0.68±0.04**
Number of females	6	0	6	6
Body weight (g)	319±22		309±13	311±18
Uterus (mg)	543±32		753±186*	734±97*
(mg%)	171±17		243±54**	236±30*

Significantly different from control group (*: p<0.05; **: p<0.01)

 

Table 5: Histopathological findings of male and female rats after the administration and recovery period.

Group	Control	Test substance
mg/kg	0	62.5	250	1000
Number of males	6	6	6	5
After administration period/recovery period
Duodenum, vacuolization, lamina propria	0/0	0/0	1 (slight)/ 1 (slight)	3 (slight)*/2 (slight-mild)
Ileum, vacuolization, lamina propria	0/0	0/0	1 (slight)/0	5 (mild)**/ 5 (mild)**
Mesenteric lymph node, vacuolization simus	0/0	0/0	0/0	2 (slight)/4 (slight)**
Kidney, hyperplasia, transitional epithelium	0/0	0/0	0	5 (mild)**
Pyelonephritis	0/0	0/0	0	5 (mild-moderate)**
Regeneration, urinary tubule	0/0	1 (slight)/0	0/0	0/5 (slight-mild)**
Urinary bladder, hyperplasia, transitional epithelium	0/0	2 (slight)/0	6 (slight-mild)**/ 5 (slight)**	5 (mild)**/ 5 (slight)**
Urethra, hyperplasia, transitional epithelium	0/0	0/0	0/0	4 (slight-mild)**/0
Number of females	6	6	6	6
Duodenum, vacuolization, lamina propria	0/0	0/-	1 (slight)/0	2 (slight-mild)/5 (slight)**
Jejunum, vacuolization, lamina propria	0/0	0/-	0/0	6 (mild)**/ 6 (mild)**
Mesenteric lymph node, vacuolization simus	0/0	0/-	0/0	3 (slight-mild)*/ 3 (slight)*
Kidney, hyperplasia, transitional epithelium	0/0	0/-	0/0	3 (slight-mild)*/ 3 (slight)*
Regeneration, urinary tubule	0/0	0/-	0/0	3 (slight)*/ 4 (slight)*
Urinary bladder, hyperplasia, transitional epithelium	0/0	0/-	6 (slight-mild)**/ 6 (slight-mild)**	6 (mild)**/6 (slight-mild)**
Urethra, hyperplasia, transitional epithelium

Significantly different from control group (*: p<0.05; **: p<0.01)

 

Conclusions:

In the combined repeated dose toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP, administration of trimethoxy(vinyl)silane at a dose of 62.5 mg/kg bw/day did not lead to organ damage including irreversible morphological effects permanently impairing the function of the organ/tissue (reversibility after recovery period). Also, no other effects such as necrosis or other cell death were reported, which could contribute to the degeneration of the metabolically-functional tissue. The No Observed Adverse Effect Level (NOAEL) was therefore determined to be 62.5 mg/kg bw/day. The Lowest Observed Adverse Effect Level (LOAEL) was set to 250 mg/kg bw/day, based on the histopathological changes in the urinary bladder observed in all animals (males and females) at this dose level.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

40 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

Conducted according to OECD Test Guideline 443 and in compliance with GLP. This EOGRTS is used as the basis for the oral repeated dose CSA value

System:

urinary

Organ:

bladder

kidney

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987-1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: not known

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

Animal Species. Source. and Ouality Control:
One-hundred twenty-two (122) male and ninety-nine (99) female rats (F344/NHSD BR), 36 days of age, were received on November 17, 1986, from Harlan Sprague-Dawley, Inc. (Indianapolis, IN). Faecal samples from three male and three female rats were examined for intestinal parasites by the zinc sulfate method. In addition, these rats were sacrificed and submandibular lymph glands, lungs, trachea, larynx, kidneys, heart, liver, spleen, salivary glands, and nasal, cavities were fixed and examined microscopically. Parasitology examination for pinworms was performed on three male and three female rats using the Scotch® tape test of the perineal skin and hair. Prior to the parasitology examination, blood samples were obtained for possible serologic evaluations. Approximately two weeks later, additional blood samples were collected on five male and five female rats for serologic evaluation. Results of the physical examination, ophthalmic examination, parasitological tests, serologic tests, and tissue histopathology indicated that the rats were free of infectious disease and suitable for use on this study.

Animal Husbandry:
The animals were housed two or three per cage in stainless steel wire-mesh cages measuring 23.5 cm x 20 cm x 18 cm high in Room 164 (Bioclean Unit A) from November 18, 1986, to December 1, 1986. From December 1, 1986, until the end of the study, animals were housed two per cage, separated by sex and test group. Animals were moved to Room 139 on December 8, 1986. The animals assigned to the recovery (nonexposure) period were housed one per cage in Room 164 (Bioclean Unit A). A layer of Deotized Animal Cage Board® (Shepherd Specialty Papers, Inc., Kalamazoo, MI) was placed under each row of cages.
Room temperature and relative humidity were monitored continuously by a Hygrothermograph® Seven-Day Continuous Recorder, Model #8368-00 (Cole-Parmer Instrument Company, Chicago, IL). The animals were kept on a l2-hour photoperiod throughout the study. During nonexposure periods, water (Municipal Authority of Westmoreland County, Greensburg, PA), supplied by an automatic watering system, and powdered feed (Purina Certified Rodent Chow #5002, Ralston Purina Company) were available to the animals ad libitum. Analyses of the food and water showed no contaminants at concentrations high enough to interfere with the outcome of the study. During the A-17l exposures, the animals were housed two per cage, separated by sex and test group, in stainless steel, wire-mesh cages (35 cm x 17 cm x 18 cm high). Food and water were withheld during the exposures.
The animal husbandry procedures for the recovery animals were similar to those used during nonexposure periods.

Animal Identification and Group Assignment:
Each animal was uniquely numbered by toe-clipping and some of the male rats had the right ear notched. The body weight and physical condition of the animals were monitored for approximately two weeks prior to placement into exposure groups. Animals were assigned to three test groups and an air control group (20 rats per sex per exposure group, with an additional 10 male rats per control and high concentration groups), using a computer-based randomization program. For each exposure group, 10 rats per sex were scheduled for sacrifice after 14 weeks of A-17l exposure. The remaining 10 rats per sex per group were scheduled for sacrifice after a 4-week recovery period. The additional 10 male rats assigned to both the control and high concentration groups were designated only for perfusion fixation of the kidneys (for examination by electron microscopy). Five of the 10 males per group were scheduled for sacrifice after 14 weeks of exposure; the remaining 5 after the 4-week recovery period. At the time of group assignment, only animals with body weights within two standard deviations of the group mean for each sex were used in the study. Any animal in poor health was rejected from group assignment.

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

Inhalation Chamber Description and Operation:
The inhalation chambers were constructed of stainless steel with glass windows for animal observation. Chamber volume was approximately 4320 litres and the airflow was 1000 L/min (13.9 air changes per hour) for the 0, 100, and 400 ppm chambers and 1500 L/min (20.8 air changes per hour) for the 10 ppm chamber. Chamber temperature and relative humidity were recorded using an industrial thermometer (Control Specialties, Inc., Houston, TX) and Airguide Humidity Indicator (Airguide Instrument Company, Chicago, IL), respectively. Temperature and relative humidity measurements were recorded at least 10 times per exposure.

Target Concentrations and Exposure Regimen:
The animals were acclimated to the inhalation chambers (air-only exposure) for two days prior to initiation of the the substance exposure regimen. Target concentrations of a (control), 10, 100, and 400 ppm test substance were selected for this study. The rats (8 weeks of age) were exposed for six hours per day. five days a week for 13 weeks, except during the third week (no exposure on December 26, 1986). Male rats received two exposures, and female and recovery group rats received three exposures during the 14th week of the study. Control (air-only exposed) animals were handled in an identical manner as test substance treated animals. The 6-hour chamber exposure interval was defined as the time when the vapour generation system was turned on and subsequently turned off. The position of the cages was rotated weekly in a predetermined pattern within each chamber to compensate for any possible, but undetected, variations in chamber environment or test substance concentration.

Test substance vapour generation:
Liquid test substance was metered from a piston pump (Fluid Metering, Inc., Oyster Bay, NY) into a heated glass evaporator similar in design to that described by Carpenter et al. (1975). The temperature in the evaporator was maintained at the lowest level sufficient to vaporize the liquid. Evaporator temperatures ranged from 35 to 43°C. The resultant vapor was carried into the chamber by a countercurrent airstream that entered the bottom of the evaporator.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Chamber Concentration Analyses of test substance and Methanol:
Chamber concentrations of the test substance were analyzed 6 to 8 times during each 6-hour exposure by gas chromatography. In addition, methanol concentrations were determined in the high concentration chamber once a week by gas chromatography.

Measured test substance concentrations, as mean ± SD, were 402 ± 19, 100 ±6, and 10 ± 0.7 ppm.  The concentration of methanol vapour (a product of the reaction between the test substance and water vapour) in the 400 ppm test substance chamber was approximately 20 ppm.

Duration of treatment / exposure:

5 days/week for 14 weeks

Frequency of treatment:

6 hours/day

Dose / conc.:

400 ppm (nominal)

Dose / conc.:

100 ppm (nominal)

Dose / conc.:

10 ppm (nominal)

Dose / conc.:

402 ppm (analytical)

Dose / conc.:

100 ppm (analytical)

Dose / conc.:

10 ppm (analytical)

Dose / conc.:

58 mg/m³ air

Remarks:

conversion from analytical ppm to mg/m3

Dose / conc.:

605 mg/m³ air

Remarks:

conversion from analytical ppm to mg/m3

Dose / conc.:

2 421 mg/m³ air

Remarks:

conversion from analytical ppm to mg/m3

No. of animals per sex per dose:

20/sex/dose level were exposed six hours per day, five days per week, for 14 weeks to A-171 vapor at 400, 100, 10 or 0 (control) ppm.
10/sex/dose level were sacrificed following the 14-week exposure regimen; the remaining rats were sacrificed after a 4-week recovery period.
An additional 10 male rats assigned to both the control and high concentration groups for examination of the kidneys

Control animals:

yes

Details on study design:

Four groups, each consisting of twenty male and twenty female Fischer-344 rats were exposed six hours per day, five days per week, for 14 weeks to vapour of vinyltrimethoxysilane at target concentrations of 400, 100, 10 or 0 (control) ppm. Ten rats per sex per group were sacrificed following the 14-week exposure regimen; the remaining rats were sacrificed after a 4-week recovery period. An additional ten male rats assigned to both the control and high concentration groups were designated for perfusion fixation of the kidneys for examination by electron microscopy.

Observations and examinations performed and frequency:

Monitors for toxicity were as follows: clinical observations; body weight; food and water consumption; hematologic analyses; serum chemistries;
urinalysis at study weeks 1, 3, 5, 8, 11, 14 and 18; organ weights (brain, liver, kidneys, lungs, spleen, thymus, and testes); and ophthalmic examinations

Sacrifice and pathology:

Gross pathologic and microscopic evaluations were conducted.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical signs in the 400 ppm group included urogenital area wetness and alopecia.

Mortality:

no mortality observed

Description (incidence):

There were no mortalities throughout the study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Male and female rats of the 400 ppm group had decreases (11 to 16% below control values) in body weights. Occasional decreases in body weights of the female rats of the 100 ppm group were also observed.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption was not altered. 

Food efficiency:

not examined

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

effects observed, treatment-related

Description (incidence and severity):

Water consumption was increased in the male rats of the 400 ppm group at study weeks 1, 5, 8, and 14 and for females during the first week.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

There were no treatment-related eye lesions. 

Haematological findings:

no effects observed

Description (incidence and severity):

There were no biologically significant changes in haematology or serum chemistries in rats exposed to the test substance.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

There were no biologically significant changes in haematology or serum chemistries in rats exposed to the test substance.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

Urinalysis results indicated that male rats of the 400 ppm group had lower osmolality, lower electrolyte concentrations, and a decrease in estimated creatinine clearance.  Female rats of the 400 ppm group had similar changes, but at week 14 only. A decrease in urine osmolality with a concomitant increase in urine volume was observed in male rats of the 100 ppm group at week 1.

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

At necropsy, there were no changes in organ weights in rats of the 400 ppm group that were considered to result from body weight depression. 

Gross pathological findings:

no effects observed

Description (incidence and severity):

At necropsy, there were no exposure-related lesions.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Noteworthy microscopic lesions in rats of the 400 ppm group were observed in two tissues, the urinary bladder and the kidney.  Minimal cystitis in the bladder submucosa was observed at 14 weeks, and submucosal mastocytosis was observed at 18 weeks.  Renal lesions in a few of the 400 ppm-exposed rats included papillary necrosis, interstitial edema, and/or papillary hyperplasia of the transitional epithelium.  Electron microscopic examination of the kidneys supported the light microscopic findings.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not examined

Details on results:

There were no findings in the 10 ppm exposed group. 

In the rats of the 400 and 100 ppm groups some effects were noted. These findings were minimal to mild in severity and usually infrequent in occurrence.  For most of the abnormalities, a return to normality was observed following the 4-week post-exposure period, indicating recovery.  

Based on the fact that at 100 ppm (605 mg/m3) there were some body weight gain reductions in females, but they were less than 10% and not always statistically significant, and there were no such finding in males, males had mild effects on urine osmolality and urine volume in week 1 only, and there were no adverse findings from serum chemistry, haematology, organ weight, macro- or microscopy and no findings at all at the end of the recovery period for this group, it is concluded that the effects at 100 ppm are non-adverse and the NOAEC is 100ppm. [study author opinion - NOAEC and an opinion on adversity of the findings were not stated in the test report]

Key result

Dose descriptor:

NOAEC

Effect level:

100 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

urinalysis

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

400 ppm

System:

urinary

Organ:

bladder

kidney

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Conclusions:

Rats repeatedly exposed to 400 ppm trimethoxy(vinyl)silane for 14 weeks had minimal to mild alterations in body weight, water consumption, urinalysis, organ weights, and bladder and kidney histopathology. The clinical chemistry findings in males at 400 mg/kg bw/day (lower electrolyte concentrations and decreased creatinine clearance) also suggests renal effect at this dose. At a concentration of 100 ppm there were some body weight gain reductions in females, but they were less than 10% and not always statistically significant, and there were no such finding in males; males had mild effects on urine osmolality and urine volume in week 1 only and there were no associated organ weight changes, macroscopic or microscopic findings. There were no findings at the end of the recovery period. Therefore, the findings at 100 ppm were concluded not to be adverse and the NOAEC in Fischer 344 rats was therefore 100 ppm (605 mg/m3).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

605 mg/m³

Study duration:

subchronic

Species:

rat

Quality of whole database:

Conducted according to a protocol similar to OECD Test Guideline 413 and in compliance with GLP

System:

urinary

Organ:

bladder

kidney

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987-1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: not known

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

Animal Species. Source. and Ouality Control:
One-hundred twenty-two (122) male and ninety-nine (99) female rats (F344/NHSD BR), 36 days of age, were received on November 17, 1986, from Harlan Sprague-Dawley, Inc. (Indianapolis, IN). Faecal samples from three male and three female rats were examined for intestinal parasites by the zinc sulfate method. In addition, these rats were sacrificed and submandibular lymph glands, lungs, trachea, larynx, kidneys, heart, liver, spleen, salivary glands, and nasal, cavities were fixed and examined microscopically. Parasitology examination for pinworms was performed on three male and three female rats using the Scotch® tape test of the perineal skin and hair. Prior to the parasitology examination, blood samples were obtained for possible serologic evaluations. Approximately two weeks later, additional blood samples were collected on five male and five female rats for serologic evaluation. Results of the physical examination, ophthalmic examination, parasitological tests, serologic tests, and tissue histopathology indicated that the rats were free of infectious disease and suitable for use on this study.

Animal Husbandry:
The animals were housed two or three per cage in stainless steel wire-mesh cages measuring 23.5 cm x 20 cm x 18 cm high in Room 164 (Bioclean Unit A) from November 18, 1986, to December 1, 1986. From December 1, 1986, until the end of the study, animals were housed two per cage, separated by sex and test group. Animals were moved to Room 139 on December 8, 1986. The animals assigned to the recovery (nonexposure) period were housed one per cage in Room 164 (Bioclean Unit A). A layer of Deotized Animal Cage Board® (Shepherd Specialty Papers, Inc., Kalamazoo, MI) was placed under each row of cages.
Room temperature and relative humidity were monitored continuously by a Hygrothermograph® Seven-Day Continuous Recorder, Model #8368-00 (Cole-Parmer Instrument Company, Chicago, IL). The animals were kept on a l2-hour photoperiod throughout the study. During nonexposure periods, water (Municipal Authority of Westmoreland County, Greensburg, PA), supplied by an automatic watering system, and powdered feed (Purina Certified Rodent Chow #5002, Ralston Purina Company) were available to the animals ad libitum. Analyses of the food and water showed no contaminants at concentrations high enough to interfere with the outcome of the study. During the A-17l exposures, the animals were housed two per cage, separated by sex and test group, in stainless steel, wire-mesh cages (35 cm x 17 cm x 18 cm high). Food and water were withheld during the exposures.
The animal husbandry procedures for the recovery animals were similar to those used during nonexposure periods.

Animal Identification and Group Assignment:
Each animal was uniquely numbered by toe-clipping and some of the male rats had the right ear notched. The body weight and physical condition of the animals were monitored for approximately two weeks prior to placement into exposure groups. Animals were assigned to three test groups and an air control group (20 rats per sex per exposure group, with an additional 10 male rats per control and high concentration groups), using a computer-based randomization program. For each exposure group, 10 rats per sex were scheduled for sacrifice after 14 weeks of A-17l exposure. The remaining 10 rats per sex per group were scheduled for sacrifice after a 4-week recovery period. The additional 10 male rats assigned to both the control and high concentration groups were designated only for perfusion fixation of the kidneys (for examination by electron microscopy). Five of the 10 males per group were scheduled for sacrifice after 14 weeks of exposure; the remaining 5 after the 4-week recovery period. At the time of group assignment, only animals with body weights within two standard deviations of the group mean for each sex were used in the study. Any animal in poor health was rejected from group assignment.

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

Inhalation Chamber Description and Operation:
The inhalation chambers were constructed of stainless steel with glass windows for animal observation. Chamber volume was approximately 4320 litres and the airflow was 1000 L/min (13.9 air changes per hour) for the 0, 100, and 400 ppm chambers and 1500 L/min (20.8 air changes per hour) for the 10 ppm chamber. Chamber temperature and relative humidity were recorded using an industrial thermometer (Control Specialties, Inc., Houston, TX) and Airguide Humidity Indicator (Airguide Instrument Company, Chicago, IL), respectively. Temperature and relative humidity measurements were recorded at least 10 times per exposure.

Target Concentrations and Exposure Regimen:
The animals were acclimated to the inhalation chambers (air-only exposure) for two days prior to initiation of the the substance exposure regimen. Target concentrations of a (control), 10, 100, and 400 ppm test substance were selected for this study. The rats (8 weeks of age) were exposed for six hours per day. five days a week for 13 weeks, except during the third week (no exposure on December 26, 1986). Male rats received two exposures, and female and recovery group rats received three exposures during the 14th week of the study. Control (air-only exposed) animals were handled in an identical manner as test substance treated animals. The 6-hour chamber exposure interval was defined as the time when the vapour generation system was turned on and subsequently turned off. The position of the cages was rotated weekly in a predetermined pattern within each chamber to compensate for any possible, but undetected, variations in chamber environment or test substance concentration.

Test substance vapour generation:
Liquid test substance was metered from a piston pump (Fluid Metering, Inc., Oyster Bay, NY) into a heated glass evaporator similar in design to that described by Carpenter et al. (1975). The temperature in the evaporator was maintained at the lowest level sufficient to vaporize the liquid. Evaporator temperatures ranged from 35 to 43°C. The resultant vapor was carried into the chamber by a countercurrent airstream that entered the bottom of the evaporator.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Chamber Concentration Analyses of test substance and Methanol:
Chamber concentrations of the test substance were analyzed 6 to 8 times during each 6-hour exposure by gas chromatography. In addition, methanol concentrations were determined in the high concentration chamber once a week by gas chromatography.

Measured test substance concentrations, as mean ± SD, were 402 ± 19, 100 ±6, and 10 ± 0.7 ppm.  The concentration of methanol vapour (a product of the reaction between the test substance and water vapour) in the 400 ppm test substance chamber was approximately 20 ppm.

Duration of treatment / exposure:

5 days/week for 14 weeks

Frequency of treatment:

6 hours/day

Dose / conc.:

400 ppm (nominal)

Dose / conc.:

100 ppm (nominal)

Dose / conc.:

10 ppm (nominal)

Dose / conc.:

402 ppm (analytical)

Dose / conc.:

100 ppm (analytical)

Dose / conc.:

10 ppm (analytical)

Dose / conc.:

58 mg/m³ air

Remarks:

conversion from analytical ppm to mg/m3

Dose / conc.:

605 mg/m³ air

Remarks:

conversion from analytical ppm to mg/m3

Dose / conc.:

2 421 mg/m³ air

Remarks:

conversion from analytical ppm to mg/m3

No. of animals per sex per dose:

20/sex/dose level were exposed six hours per day, five days per week, for 14 weeks to A-171 vapor at 400, 100, 10 or 0 (control) ppm.
10/sex/dose level were sacrificed following the 14-week exposure regimen; the remaining rats were sacrificed after a 4-week recovery period.
An additional 10 male rats assigned to both the control and high concentration groups for examination of the kidneys

Control animals:

yes

Details on study design:

Four groups, each consisting of twenty male and twenty female Fischer-344 rats were exposed six hours per day, five days per week, for 14 weeks to vapour of vinyltrimethoxysilane at target concentrations of 400, 100, 10 or 0 (control) ppm. Ten rats per sex per group were sacrificed following the 14-week exposure regimen; the remaining rats were sacrificed after a 4-week recovery period. An additional ten male rats assigned to both the control and high concentration groups were designated for perfusion fixation of the kidneys for examination by electron microscopy.

Observations and examinations performed and frequency:

Monitors for toxicity were as follows: clinical observations; body weight; food and water consumption; hematologic analyses; serum chemistries;
urinalysis at study weeks 1, 3, 5, 8, 11, 14 and 18; organ weights (brain, liver, kidneys, lungs, spleen, thymus, and testes); and ophthalmic examinations

Sacrifice and pathology:

Gross pathologic and microscopic evaluations were conducted.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical signs in the 400 ppm group included urogenital area wetness and alopecia.

Mortality:

no mortality observed

Description (incidence):

There were no mortalities throughout the study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Male and female rats of the 400 ppm group had decreases (11 to 16% below control values) in body weights. Occasional decreases in body weights of the female rats of the 100 ppm group were also observed.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption was not altered. 

Food efficiency:

not examined

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

effects observed, treatment-related

Description (incidence and severity):

Water consumption was increased in the male rats of the 400 ppm group at study weeks 1, 5, 8, and 14 and for females during the first week.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

There were no treatment-related eye lesions. 

Haematological findings:

no effects observed

Description (incidence and severity):

There were no biologically significant changes in haematology or serum chemistries in rats exposed to the test substance.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

There were no biologically significant changes in haematology or serum chemistries in rats exposed to the test substance.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

Urinalysis results indicated that male rats of the 400 ppm group had lower osmolality, lower electrolyte concentrations, and a decrease in estimated creatinine clearance.  Female rats of the 400 ppm group had similar changes, but at week 14 only. A decrease in urine osmolality with a concomitant increase in urine volume was observed in male rats of the 100 ppm group at week 1.

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

At necropsy, there were no changes in organ weights in rats of the 400 ppm group that were considered to result from body weight depression. 

Gross pathological findings:

no effects observed

Description (incidence and severity):

At necropsy, there were no exposure-related lesions.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Noteworthy microscopic lesions in rats of the 400 ppm group were observed in two tissues, the urinary bladder and the kidney.  Minimal cystitis in the bladder submucosa was observed at 14 weeks, and submucosal mastocytosis was observed at 18 weeks.  Renal lesions in a few of the 400 ppm-exposed rats included papillary necrosis, interstitial edema, and/or papillary hyperplasia of the transitional epithelium.  Electron microscopic examination of the kidneys supported the light microscopic findings.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not examined

Details on results:

There were no findings in the 10 ppm exposed group. 

In the rats of the 400 and 100 ppm groups some effects were noted. These findings were minimal to mild in severity and usually infrequent in occurrence.  For most of the abnormalities, a return to normality was observed following the 4-week post-exposure period, indicating recovery.  

Based on the fact that at 100 ppm (605 mg/m3) there were some body weight gain reductions in females, but they were less than 10% and not always statistically significant, and there were no such finding in males, males had mild effects on urine osmolality and urine volume in week 1 only, and there were no adverse findings from serum chemistry, haematology, organ weight, macro- or microscopy and no findings at all at the end of the recovery period for this group, it is concluded that the effects at 100 ppm are non-adverse and the NOAEC is 100ppm. [study author opinion - NOAEC and an opinion on adversity of the findings were not stated in the test report]

Key result

Dose descriptor:

NOAEC

Effect level:

100 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

urinalysis

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

400 ppm

System:

urinary

Organ:

bladder

kidney

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Conclusions:

Rats repeatedly exposed to 400 ppm trimethoxy(vinyl)silane for 14 weeks had minimal to mild alterations in body weight, water consumption, urinalysis, organ weights, and bladder and kidney histopathology. The clinical chemistry findings in males at 400 mg/kg bw/day (lower electrolyte concentrations and decreased creatinine clearance) also suggests renal effect at this dose. At a concentration of 100 ppm there were some body weight gain reductions in females, but they were less than 10% and not always statistically significant, and there were no such finding in males; males had mild effects on urine osmolality and urine volume in week 1 only and there were no associated organ weight changes, macroscopic or microscopic findings. There were no findings at the end of the recovery period. Therefore, the findings at 100 ppm were concluded not to be adverse and the NOAEC in Fischer 344 rats was therefore 100 ppm (605 mg/m3).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

2 421 mg/m³

Study duration:

subchronic

Species:

rat

Quality of whole database:

Conducted according to a protocol similar to OECD Test Guideline 413 and in compliance 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

In the key oral repeated dose study (combined repeated dose oral toxicity study, with a reproduction/developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP (Hashima Laboratory, 2005)), trimethoxy(vinyl)silane was administered by gavage at doses of 62.5, 250 or 1000 mg/kg bw/day (in corn oil) for 42 days to Sprague-Dawley rats. Two males and one female from the 1000 mg/kg bw/day group died and the clinical signs noted in the dying animals were: decrease in locomotor activity; reddish urine; hypothermia; perioral smudges; perianal soiling; diarrhoea; bradypnea and/or piloerection. Soiled hair and reddish urine were noted in the surviving males and females of the 1000 and 250 mg/kg bw/day groups.

A decrease in relative thymus weights in females was observed at all doses. Decreased absolute thymus weights and increased relative liver weights in females of the 1000 mg/kg bw/day group were noted. In males a decrease in the absolute thymus weight was observed in the 1000 mg/kg bw/day group only. No reduction in thymus weight was observed at the end of the recovery period in males and females at any dose level. Histopathology revealed no changes in the thymus in the 62.5 and 250 mg/kg bw/day group. In the 1000 mg/kg bw/day group a slight atrophy (cortex and medulla) was observed in 2/6 females after the administration period, but no effects were observed after the recovery period.

In the 1000 mg/kg bw/day dose group the incidence of hyperplasia of the transitional epithelium in the kidney was statistically significantly increased in male and female animals. This finding was still present in male and female animals after the recovery period, although the severity was slightly decreased. No effects on the kidney were observed in the 62.5 and 250 mg/kg bw/day groups.

On histopathological examination, hyperplasia of the transitional epithelium in the urinary bladder was noted in males at all doses. The effect seemed to be substance-related and followed a dose-response relationship. The incidence of hyperplasia in the 250 and 1000 mg/kg bw/day groups was statistically significantly increased up to the end of the recovery period, although a slight decrease (mild to slight) in severity was observed from end of administration period to the end of the recovery period. Hyperplasia that was observed in 2/6 male rats of the 62.5 mg/kg bw/day group after the administration period seemed to be treatment-related, as there were no incidences in the control group; hyperplasia was not observed in the urinary bladder of females in the 62.5 mg/kg bw/day group. In general, hyperplasia in the urinary tract/bladder is not a typical spontaneous lesion, but simple hyperplasia may also occur in untreated animals. Often it is a secondary effect provoked by inflammation or physical damage. The effects observed in males at 62.5 mg/kg bw/day were not evaluated as adverse, as the incidence was not increased statistically significantly, and the severity of the effect was stated as "slight". In addition, the effects were fully reversible within the recovery period. Administration of trimethoxy(vinyl)silane at a dose of 62.5 mg/kg bw/day did not lead to organ damage including irreversible morphological effects permanently impairing the function of the organ/tissue (reversibility after recovery period). Also, no other effects such as necrosis or other cell death were reported, which could contribute to the degeneration of the metabolically-functional tissue. The No Observed Adverse Effect Level (NOAEL) was therefore determined to be 62.5 mg/kg bw/day. The Lowest Observed Adverse Effect Level (LOAEL) was 250 mg/kg bw/day, based on the histopathological changes in the urinary bladder observed in all animals (males and females) at this dose level.

In the 28-day oral repeated dose toxicity study used as dose range finder for the subsequent extended one-generation reproductive toxicity study, conducted according to OECD Test Guideline 407 and in compliance with GLP, 5 groups each consisting of 5 male and 5 female Wistar rats were given daily oral gavage administration of 0 (group 1), 50 (group 2), 150 (group 3), 600 (group 4) or 1000 (group 5) mg/kg bw/day trimethoxy(vinyl)silane in corn oil for 28 days (BSL Bioservice, 2020a). During the period of administration, the animals were observed each day for signs of toxicity. Animals that died were examined macroscopically and at the conclusion of the test, surviving animals were sacrificed and observed macroscopically. Body weight and food consumption were measured weekly. At the conclusion of the treatment period, all animals were sacrificed and subjected to necropsy. A full histopathological evaluation of the tissues was performed on animals of dose group 5 and control (group 1) animals which was extended to intermediate dose groups (2-4).

No mortality occurred during the treatment period in any of the groups and no adverse effects of test item were found on clinical observations, functional observations, body weight development, food consumption, clinical biochemistry or urinary parameters.

Males treated with 1000 mg/kg bw/day were observed with slightly lower body weights/lower body weight gain and a correlating tendency towards lower food consumption throughout the treatment period.

Increases in haematological parameters compared to control were observed in reticulocytes in males at =600 mg/kg bw/day and females at =150 mg/kg bw/day and monocytes in males and females at =150 mg/kg bw/day. Slightly higher serum TBA values were observed in male animals at =50 mg/kg bw/day. The effects were assumed by the study author to be test-item related. The effects were assumed by the study author to be test-item related.

Test item-related lesions were observed in the kidneys (enlargement, renal pelvis dilatation), ureters (dilatation) and urinary bladder (thickened wall). Histopathological treatment-related changes were observed in organs of the urinary system (i.e. urothelial hyperplasia, inflammatory reactions, liminal precipitate(s), granular casts, tubular dilatation, and tubular basophilia) in animals at =150 mg/kg bw/day, and in the small intestine with regional lymphoid tissues (lipid accumulation) in animals at =600 mg/kg bw/day.

The NOAEL for systemic effects was concluded to be 50 mg/kg bw/day based on urothelial hyperplasia (with inflammatory changes in males) in the urinary bladder of animals at >150 mg/kg bw/day. Dose levels of 40, 100, and 300 mg/kg bw/day were selected for the subsequent extended one-generation reproductive toxicity study (OECD Test Guideline 443) with the test substance.

In the EOGRTS conducted according to OECD Test Guideline 443 and in compliance with GLP (BSL Bioservice, 2021) and as used for the oral CSA (study discussed in further detail in Section 5.9.3 Summary and discussion of reproductive toxicity), 25 male and 25 female parental (P0 and Cohort 1B [P1]) Wistar rats per group, were exposed to 0, 40, 100, 300 mg/kg bw/day trimethoxy(vinyl)silane in corn oil by oral gavage for 2 weeks during pre-mating (males and females), for up to 2 weeks during mating (males and females), for 6 weeks during post-mating and up to termination after offspring weaning (10 weeks total exposure for males, 8-10 weeks for females). In P1 males and females (20 animals per sex and group), the direct exposure to test item was started at their weaning through scheduled termination, i.e., until study termination (weeks 20-25). The dose levels were selected based on the findings of the 28-day oral repeated dose toxicity study (BSL Bioservice, 2020a).

 

The following observations and examinations were performed, except as noted, for the P0 and P1 (F1 Cohort 1B) animals: daily post-dosing observations, detailed clinical observations, body weight, food consumption, confirmation of mating, haematology / clinical chemistry analysis (P0 only), necropsy and gross pathology including for animals that died or were moribund sacrificed, histopathology (full list for P0 high dose (HD) and control, P0 or P1 identified gross lesions, P0 or P1 animals that died or were moribund sacrificed). In addition, based on the P0 HD histopathology findings, the following low dose (LD) and mid dose (MD) tissues were evaluated via microscopic exam: kidneys, ureters, urinary bladder, duodenum, jejunum and ileum.

 

For this repeated dose section, only those parental (P0 and P1) findings identified as test-item-related and identified as the basis of the parental systemic NOAEL (urinary system) are discussed. All other parental systemic findings were identified as: not test item-related, not toxicologically relevant, lacking a dose correlation, lacking a histopathological correlation, and/or otherwise considered non-adverse. The detailed results for all endpoints / cohorts are presented in Section 5.9 Toxicity for reproduction.

 

In animals that survived their scheduled treatment period, gross lesions that were considered to be treatment-related were recorded in the urinary bladder of females from the P0 generation and in the urinary bladder and/or ureters of both sexes of animals from the P1 generation. Test item-related changes also were found in the kidney of P0 animals.

In the P0 histopathological examination, microscopic changes that could be attributed to treatment with the test item were observed in the kidneys and urinary bladder of both sexes of animals treated with 100 mg/kg bw/day and higher, and in the ureters of both sexes of animals treated with 300 mg/kg bw/day.

 

In the kidneys of the P0 generation, the following histopathological changes were observed: diffuse urothelial hyperplasia and mixed inflammatory cell infiltration in the suburothelium in both sexes; fibrosis at/around the fornix, focal to multifocal interstitial fibrosis, pelvic luminal precipitates, and foreign body giant cells at/around the fornix in males; and increased incidence and/or severity of pelvic dilation, focal to multifocal mononuclear cell infiltration, tubular basophilia and tubular dilatation in males. In the urinary bladder of the P0 generation, the following changes were observed: diffuse urothelial hyperplasia, mixed inflammatory cell infiltration in the mucosa, increased incidence and/or severity of mononuclear cell focus/foci in lamina propria, submucosal oedema, congestion, and haemorrhage in both sexes. In the ureters of the P0 generation, the following changes were observed: diffuse urothelial hyperplasia in both sexes; increased incidence and severity of luminal dilatation in males; and mixed inflammatory cell infiltration and submucosal oedema, as well as diffuse urothelial hyperplasia and luminal dilatation, in the ureters present by chance on the prostate sections.

 

Consistent with the renal histopathology, lower creatinine was observed in P0 animals for HD group males and in MD and HD group females, although within historical control and without a dose-response.

 

The NOAEL for systemic toxicity for the parental animals (P0 and F1 Cohort 1B [P1]) animals was concluded to be 40 mg/kg bw/day based on test substance-related effects in the urinary system (kidney, bladder) at 100 and 300 mg/kg bw/day (P0 and P1 gross pathology and P0 histopathology).

In the key 14-week vapour inhalation study in rats which was conducted using a protocol similar to OECD Test Guideline 413 and in compliance with GLP (Bushy Run Research Center, 1990), rats were repeatedly exposed to nominal concentrations of  10, 100 or 400 ppm of the registered substance for 6 hours per day over 14 weeks. Minimal to mild alterations in body weight, water consumption, urinalysis, organ weights, and bladder and kidney histopathology were observed. Clinical signs in the 400 ppm group included urogenital area wetness and alopecia. There were no treatment-related eye lesions. Male and female rats of the 400 ppm group had decreased body weights (11 to 16% below control values). Occasional decreases in body weights of the female rats of the 100 ppm group were also observed. Food consumption was not altered. Water consumption was increased in the male rats of the 400 ppm group at study weeks 1, 5, 8, and 14 and for females during the first week. Urinalysis results indicated that male rats of the 400 ppm group had lower osmolality, lower electrolyte concentrations, and a decrease in estimated creatinine clearance, with these findings consistent with renal the histopathology. Female rats of the 400 ppm group had similar changes, but at week 14 only. A decrease in urine osmolality with a concomitant increase in urine volume was observed in male rats of the 100 ppm group at week 1. There were no biologically significant changes in haematology or serum chemistries in rats exposed to the test material. At necropsy, there were no exposure-related lesions, and changes in organ weights in rats of the 400 ppm group were considered to result from body weight depression. Noteworthy microscopic lesions in rats of the 400 ppm group were observed in two tissues, the urinary bladder and the kidney. Minimal cystitis in the bladder submucosa was observed at 14 weeks, and submucosal mastocytosis was observed at 18 weeks. Renal lesions in a few of the 400 ppm-exposed rats included papillary necrosis, interstitial oedema, and/or papillary hyperplasia of the transitional epithelium. Electron microscopic examination of the kidneys supported the light microscopic findings. Based on the fact that at 100 ppm (605 mg/m³) there were some body weight gain reductions in females, but they were less than 10% and not always statistically significant, there were no such finding in males, males had mild effects on urine osmolality and urine volume in week 1 only, and there were no adverse findings from serum chemistry, haematology, organ weight, macro- or microscopy and no findings at all at the end of the recovery period for this group, it is concluded that the effects at 100 ppm are non-adverse and the NOAEC is 100ppm. [study author opinion - NOAEC and an opinion on adversity of the findings were not stated in the study report]

Justification for classification or non-classification

The results of the EOGRTS (OECD Test Guideline 443) and the combined repeated dose oral toxicity study, with a reproduction/developmental toxicity screening test (OECD Test Guideline 422) and the 28-day oral repeated dose toxicity study (OECD Test Guideline 407) have been reviewed with regards to STOT RE classification.

Consideration of STOT RE 2 Classification for trimethoxy(vinyl)silane:

The review of the repeated oral exposure data, including the EOGRT study, and the STOT RE 2 classification guidelines, revealed that repeated exposure to trimethoxy(vinyl)silane causes a treatment-related effect on the urinary bladder, kidneys, ureters, and the small intestine.  

First, the observed effects have been reviewed in order to determine whether there are any test item-related effects that rise to the level of a toxic effect within the guidance value range of >10 mg/kg bw/day and =100 mg/kg bw/day:

• In the combined repeated dose oral toxicity study, with a reproduction/developmental toxicity screening test (OECD Test Guideline 422) (Hashima Laboratory, 2005), the LOAEL was 250 mg/kg bw/day based on the histopathological changes in the urinary bladder observed in all animals (males and females) at this dose level.  Given that the exposure duration for both males and toxicity group females was 44 days, the guidance value should be increased by an appropriate factor of two, making the upper value of the guidance range =200 mg/kg bw/day.  Since the LOAEL for the study (250 mg/kg bw/day) exceeds the upper guidance value, this study would not support classification for STOT RE, no matter what adverse test item-related effects had been observed.

• In the 28-day oral repeated dose toxicity study (dose range-finding study) (OECD Test Guideline 407) (BSL Bioservice, 2020a), test item-related lesions were observed in the kidneys, ureters and urinary bladder at =150 mg/kg bw/day, in the small intestine at =600 mg/kg bw/day and the histopathological no-observed-effect-level (NOEL) was established at 50 mg/kg bw/day. Based on the exposure duration of 28-days, the guidance value would be increased by a factor of three, making the guidance range >30 to =300 mg/kg bw/day. Therefore, only those test item-related effects observed at 150 mg/kg bw/day should be considered as supporting a classification of STOT RE. In examining the results for specific changes at 150 mg/kg bw/day, only the following results were identified:

- Urinary bladder: diffuse urothelial hyperplasia in 5/5 males and 4/5 females. This lesion was accompanied by inflammatory reactions, such as mixed inflammatory cell infiltration (3/5 males), with occasional mucosal haemorrhage, mononuclear cell foci (3/5 males and 1/5 females) and submucosal oedema (2/5 males) in the urinary bladder.

- Kidney: tubular basophilia in 1/5 males and 1/5 females.

• In the EOGRTS (OECD Test Guideline 443) (BSL Bioservice, 2021), the only test item-related findings observed at =100 mg/kg bw/day (i.e., limited to LD and MD findings at 40 and 100 mg/kg bw/day, respectively) were:

- Urinary bladder - thickened wall: in 1/24 LD and 3/25 MD P-generation females; and in 1/20 F1-generation MD Cohort 1B females;

- Urinary bladder: diffuse urothelial hyperplasia in 20/25 MD males and 12/25 MD females of the P-generation; and in 12/20 MD males and 4/19 MD females of the F1-generation Cohort 1A group;

- Kidney: diffuse urothelial hyperplasia in 1/25 MD males and 2/25 MD females of the P-generation; and in 2/20 MD males and 1/19 MD females of the F1-generation Cohort 1A group.

Second, the identified test item-related effects that are within the guidance value range of >10 mg/kg bw/day and =100 mg/kg bw/day have been reviewed to determine whether they can be considered as significant toxic effects:  

• Table 3.9.1 of Regulation (EC) No 1272/2008 and Figure 3.9.1 in GHS Regulation specifically refers to “significant toxic effects” in animals as being the basis for STOT RE 2.  

• Section 3.9.2.7.1 of Regulation (EC) No 1272/2008 and GHS Regulation states that “reliable evidence … of a consistent and identifiable toxic effect demonstrates support for classification”. In the reviewed data the effects were only limited to findings of hyperplasia in the urinary bladder and diffuse urothelial hyperplasia or tubular basophilia in the kidney.

• Section 3.9.2.7.3 of Regulation (EC) No 1272/2008 and GHS Regulation uses modifying terms such as "significant", "mutli-focal" or "diffuse", "marked", or appreciable in describing the types of effects that might trigger classification. The effects observed in the urinary bladder and kidney in limited animals are not considered to be indicative of significant organ damage or dysfunction.

• Section 3.9.2.7.3(d) of Regulation (EC) No 1272/2008 and GHS Regulation specifies “significant organ damage.”  The data do not support these criteria.

• Section 3.9.2.7.3(e) of Regulation (EC) No 1272/2008 and GHS Regulation refers to “multi-focal or diffuse necrosis, fibrosis or granuloma formation in vital organs with regenerative capacity.”  The data do not support these criteria.

• Section 3.9.2.7.3(f) of Regulation (EC) No 1272/2008 and GHS Regulation indicates “morphological changes that are potentially reversible but provide clear evidence of marked organ dysfunction.” Although histomorphological changes were observed, overall the data do not support marked organ dysfunction.

     

In addition, the dose-response relationship for the observed effects and influence of the exposure duration have been given consideration:

• Dose-response relationship for the observed effects on urinary bladder and kidney – the incidence and severity of the observed effects increased with the doses. In the extended one-generation reproductive toxicity study (BSL Bioservice, 2021), diffuse urothelial hyperplasia in the urinary bladder was evident for all male and female P and F1 Cohort 1A animals in the high dose group, while fewer animals were affected in the mid dose group from P and F1 Cohort 1A animals. In addition, higher number of high dose animals from P and F1 Cohort 1A had diffuse urothelial hyperplasia in the kidney when compared to the mid dose animals. Pathology and microscopic findings at low doses do not appear to be early stages of more severe or irreversible tissue damages or tumour formation. The only effect seen at low doses in the extended one-generation reproductive toxicity study is thickened urinary bladder wall in one P female, which was also evident in 3 control P females and no corresponding microscopic changes were detected for these animals. Therefore, these changes can be concluded as non-treatment related. In the combined repeated dose oral toxicity study, with a reproduction/developmental toxicity screening test (Hashima Laboratory, 2005) treatment-related hyperplasia of transitional epithelium in the urinary bladder was noted in males at all doses. The effect seemed to be substance-related and followed a dose-response relationship. The incidence of hyperplasia in the mid and high dose groups was statistically significantly increased up to the end of the recovery period. Treatment-related hyperplasion was observed in 2/6 male rats of the low dose group and there were no such incidences in the control group. The effects observed in low dose males were not evaluated as adverse, as the incidence was not increased statistically significantly and the severity of the effect was stated as "slight". In addition, the effects were fully reversible within the recovery period. In female rats, hyperplasia of transitional epithelium in the urinary bladder was noted in all mid and high dose animals, while hyperplasia was not observed in the urinary bladder of low dose group females. In the 28-day oral repeated dose toxicity study (BSL Bioservice, 2020a), diffuse urothelial hyperplasia was observed in the urinary bladder of both sexes in groups that received 150 mg/kg bw/day (lower mid dose) and higher, as well as in the kidneys and ureters of both sexes in groups 600 mg/kg bw/day (higher mid dose) and higher. There were no effects reported in low dose group animals in the 28-day oral repeated dose toxicity study (dose range-finding study) (OECD Test Guideline 407).

• Influence of exposure duration on severity of effects – Similar effects in severity and incidence are seen in the available data for trimethoxy(vinyl)silane and there is no evidence to suggest that longer exposure duration leads to irreversible, or more severe effects.

Overall, it was concluded that the adverse test item-related effects observed in the urinary bladder and kidney do not rise to the level of a “significant toxic effect" as required by Regulation (EC) No 1272/2008 and GHS Regulation. According to Regulation (EC) No 1272/2008 and GHS Regulation, the significant toxic effect must specifically show “significant organ damage”, “multi-focal or diffuse … granuloma formation in vital organs with regenerative capacity”, or “morphologic changes that provide clear evidence of marked organ dysfunction”. The data do not support these criteria.

Furthermore, the treatment-related changes in the urinary bladder and kidney of rats administered trimethoxy(vinyl)silane were evaluated in an Expert Panel Review Report (EPL, 2020) which aimed to determine the pathogenesis of these changes. The Expert Panel concluded that the treatment-related urothelial changes were identical in the urinary bladder, kidney, and ureter (when present) and consisted of a diffuse urothelial hyperplasia without atypia, which was considered to be an adaptive response to a physical or chemical irritant present within the urine. This type of diffuse hyperplasia was not considered to represent a preneoplastic change. For more details on the EPL Report (2020) see attachment to IUCLID Section 13.

Based on the available data, trimethoxy(vinyl)silane does not require classification for target organ toxicity following repeated exposure according to Regulation (EC) No 1272/2008.