Reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane

Endpoint summary

Description of key information

No repeated dose toxicity data are available for the registered substance, therefore this endpoint is addressed using weight of evidence for a number of related substances. Based on the available data, the overall 28-day NOAEL for male and female rats is judged to be 200 mg/kg bw/day, based on observations in the liver and kidneys at higher dose levels.

There are no data for the dermal and inhalation routes.

There is a testing proposal for a 90 -day repeated dose toxicity test with polysulfides, bis[3-(triethyoxysilyl)propyl (CAS No 211519-85-6).

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

07.02.2000 to 26.07.2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Qualifier:

according to guideline

Guideline:

other: partial revision of 'Test method of new chemical substances' in Kanpogyo No. 700, Yakuhatsu No. 1039 and 61 kikyoku No. 1014 dated 5th Dec 1986

Qualifier:

according to guideline

Guideline:

EU Method B.7 (Repeated Dose (28 Days) Toxicity (Oral))

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

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.
- Age at study initiation: Five weeks
- Weight at study initiation: Males: 126.7-142.5 g; Females: 113.4-125.5 g
- Fasting period before study: No data
- Housing: Individually in stainless steel cages with wire floors
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: Yes, but period not specified


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ±2
- Humidity (%): 55 ±10
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 07.02.2000 to 26.07.2000

Route of administration:

oral: gavage

Vehicle:

olive oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: Test substance was accurately weighed and dissolved in olive oil. The mixture of 0.08, 0.4 and 2 % w/v were made from 10% w/v mixture by dilution. The 10% mixture was prepared once per week and dilutions were conducted later.

VEHICLE
- Justification for use and choice of vehicle (if other than water): Olive oil used as TS not stable in water
- Concentration in vehicle: 10, 2, 0.4 and 0.08% w/v
- Amount of vehicle (if gavage): Total volume doses: 10 ml/kg
- Lot/batch no. (if required): 011OOA
- Purity: No data

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

28 days

Frequency of treatment:

Daily (7 days/week)

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

Six

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: A repeated dose 14-day pretest was conducted using doses of 50, 250 and 1000 mg/kg bw/day. Adverse effects were observed at all doses. Therefore the doses were adjusted for the current 28-day study to try and determine a NOAEL.
- Rationale for selecting satellite groups: To investigate reversibility of effects
- Post-exposure recovery period in satellite groups: 14 day post-exposure group for control and 1000 mg/kg bw/day groups

Positive control:

No positive control

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least one per day for general clinical observations. At least twice per day for mortality.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once before start of exposure and then once per week (all groups, except recovery groups)

BODY WEIGHT: Yes
- Time schedule for examinations: Day prior to start of exposure, then on day 1 (at 1st administration), 3, 8, 12, 17, 21, 26, 28 during the administration period, and on day 1, 5, 10 and 14 during the recovery period.

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: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of treatment and recovery periods
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes
- How many animals: All
- Parameters checked in table No.1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of treatment and recovery periods
- Animals fasted: Yes
- How many animals: All
- Parameters checked in table No.1 were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: On the last day of of administration and recovery periods (16 hour collection prior to scheduled sacrifice)
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked in table No.1 were examined.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Fourth week of exposure period and second week of recovery period
- Dose groups that were examined: All
- Battery of functions tested: Sensory activity to different types of stimulation, grip strength and locomotor activity

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 2)
HISTOPATHOLOGY: Yes (see table 2)

Other examinations:

None reported.

Statistics:

All data were evaluated with Bartlett's test for an equal variance and if the equality of variance was valid at 5% confidence limit, ONE-way ANOVA was used. If significant differences were obtained with ANOVA, data from control and treatment groups were compared by Dunnett test. If the equality of variance was no established, Kruskal-Wallis test was used. If significant differences were obtained, data from control and treatment groups were compared by nonparametric Dunnett test. Furthermore, FOB data were analysed with Kruskal-Wallis test, and if significant difference was obtained, data were further analysed with nonparametric Dunnett test.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: There were no deaths related to treatment. Clinical signs were salivation and staining around the nose and mouth. Salivation was observed in all dose groups, and is generally associated with gavage dosing.

BODY WEIGHT AND WEIGHT GAIN: No adverse effects.

FOOD CONSUMPTION: No adverse effects.

HAEMATOLOGY: Haematological examinations revealed an increase in prothrombin time and activated partial thromboplastin time in the males of the 1000 mg/kg bw/day group at the end of the treatment period. Changes were thought to be secondary to effects on the liver.

CLINICAL CHEMISTRY: Blood chemistry tests revealed an increase in total proteins and albumin in males and females, an increase in calcium in males, an increase in gamma-GPT, GPT, total cholesterol and a decrease in alkaline phosphatase in females, in groups dosed with 1000 mg/kg bw/day. Changes were thought to be secondary to effects on the liver.

URINALYSIS: No adverse effects.

NEUROBEHAVIOUR: No adverse effect on sensory activity and locomotor activity.

ORGAN WEIGHTS: At the end of the treatment period there was an increase in liver weights in males and females, and an increase in kidney weights in males in groups dosed with 1000 mg/kg bw/day.

GROSS PATHOLOGY: An increase in liver weights was also observed in females of the 1000 mg/kg bw/day group. During necropsy, enlarged liver was also observed at the end of the recovery period in males and females dosed with 1000 mg/kg bw/day.

HISTOPATHOLOGY: Centrilobular hepatocyte hypertrophy in males and females, and basophilic renal tubules in males at the end of the administration period in the 1000 mg/kg bw/day group. There was also an increase in acidophilic bodies and hyaline droplets observed in males in the 200 mg/kg bw/day group. The basophilic renal tubules in males, and increased relative liver weight in females in the highest dose group were still present at the end of the recovery period. However, the effects in the liver appeared to be reversible, as weights were reducing and histopathological changes were not apparent by the end of the recovery period.

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Based on liver hypertrophy at 1000 mg/kg bw/day. Kidney effects assumed not relevant to humans.

Critical effects observed:

not specified

Conclusions:

In a 28-day repeated dose oral gavage study, conducted to a national standard method and GLP (reliability score 1), the NOAEL for TESPPS was 200 mg/kg bw/day, based on adverse effects in the liver (enlarged liver accompanied by finding of centrilobular hypertrophy) at the higher dose of 1000 mg/kg bw/day. There were also adverse effects in the kidneys of male rats at 200 and 1000 mg/kg bw/day; however, these appeared to be alpha 2u-globulin-type effects, and have been discounted as not relevant to humans by the author of this EPSR.

Reference 2

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

11.01.1983 to 13.06.1983

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes (incl. QA statement)

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Winkelmann.
- Age at study initiation: Males: 42-49 days. Females: 49-56 days.
- Weight at study initiation: Males: 133-146g. Females: 119-137g.
- Fasting period before study:
- Housing: Macrolon cages type II (one animal/cage)
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: One week.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ±2
- Humidity (%): 50-60
- Air changes (per hr): No data
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 11.01.1983 To: 22.02.1983

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: None required, dosed undiluted (2.15 ml/kg).

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

28 days

Frequency of treatment:

Daily

Dose / conc.:

2 309 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

Five

Control animals:

other: Tap water only at same dose volume as treated animals.

Details on study design:

- Dose selection rationale: Based on the results of 14 day dose range finding study in rats.
- Rationale for animal assignment (if not random): Random
- Rationale for selecting satellite groups: To assess reversibility of any adverse effects.
- Post-exposure recovery period in satellite groups: 14 days.

Positive control:

None

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily.
- No further details


DETAILED CLINICAL OBSERVATIONS: Yes, including eye, hearing and teeth check.


BODY WEIGHT: Yes
- Time schedule for examinations: Weekly


FOOD CONSUMPTION:
- Food consumption as weekly mean values of five animals per group and sex.


FOOD EFFICIENCY: No


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: Corneal reflex only, at beginning and end of exposure period.


HAEMATOLOGY: Yes
- Time schedule for collection of blood: Prior to first administration and at the end of the study.
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: All
- Parameters checked in table No.1 were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Prior to first administration and at the end of the study.
- Animals fasted: No data
- How many animals: All
- Parameters checked in table No.1 were examined.


URINALYSIS: No


NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Weekly
- Dose groups that were examined: All
- Battery of functions tested: reflex (pupillar, pain and corneal) testing.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 2)
HISTOPATHOLOGY: Yes (see table 2)

Other examinations:

None

Statistics:

An analysis of variance was performed on all measured values of the test results of all groups. In addition, the Student t-test was performed in the case of significance.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: No deaths and clinical signs of toxicity.


BODY WEIGHT AND WEIGHT GAIN: No effects detected.


FOOD CONSUMPTION: No treatment-related effects detected. One animal was affected by adhesive pleuritis, so food intake was reduced during weeks 4 and 5.


OPHTHALMOSCOPIC EXAMINATION: No effect in corneal reflexes (no other parameter examined).


HAEMATOLOGY: No treatment-related effects.


CLINICAL CHEMISTRY: No treatment-related effects.


NEUROBEHAVIOUR: No effect on reflexes.


ORGAN WEIGHTS: The liver showed an increase in the relative organ weight in both sexes of treated animals. The absolute weight of the left kidneys was significantly different within the female recovery group as a consequence of a low, abnormal kidney weight of two control animals. The weight of both adrenal glands was relatively and absolutely reduced in the male substance treated animals compared with the controls. The differences in liver and adrenal gland weights were reversed by the end of the recovery period.


GROSS PATHOLOGY: No treatment-related effects. In the animal with adhesive pleuritis the subpleural lung parenchyma was partially involved in the disease.


HISTOPATHOLOGY: A number of histopathological changes occurred in treated and control animals that were regarded as unspecific reactions to infections or spontaneous pathology. None of the recovery animals showed these findings. In one animal a regressive change in one testis, expressing a disturbance in spermatogenesis was recorded. There were no such findings in controls, so a treatment-related effect cannot be excluded. However, it is possible that this was a spontaneous change.

Key result

Dose descriptor:

NOAEL

Effect level:

>= 2 309 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No significant irreversible effects observed at the only dose tested.

Critical effects observed:

not specified

Conclusions:

In a well conducted and reported 28-day repeated dose toxicity limit study (reliability score 1) conducted according to OECD 407 and GLP, the NOAEL for Reinforcing Agent Si 69 was at least 2309 mg/kg bw/day in rats.

Reference 3

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

21.08.2001 to 27.02.2002

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Japanese Ministry of Health and Welfare (MHW) Guidelines 1986 for a twenty-eight day repeated dose oral toxicity.

GLP compliance:

yes (incl. QA statement)

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 (UK) Limited
- Age at study initiation: Five to six weeks.
- Weight at study initiation: Males: 120-154g, Females: 112-143g
- Fasting period before study: None
- Housing: Polypropylene grid-floor cages suspended over trays lined with absorbent paper.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: Seven days.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21±2
- Humidity (%): 55±15
- Air changes (per hr): At least 15
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

arachis oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: Test material was prepared at the appropriate concentrations as a solution in dried arachis oil BP.


VEHICLE
- Justification for use and choice of vehicle (if other than water): No data
- Concentration in vehicle: 0, 31.6, 158 and 631 mg/ml
- Amount of vehicle (if gavage): No data
- Lot/batch no. (if required): No data
- Purity: No data

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples were taken of each test material formulation and were analysed for concentration of Silquest A-1589 silane. The method was not included in the part of the report provided. The results indicated that the prepared formulations were within ±9% of the nominal concentrations.

Duration of treatment / exposure:

28 Days (plus 14 day recovery)

Frequency of treatment:

Daily

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

1 221 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

Five

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Range-finding study.
- Rationale for animal assignment: Random
- Post-exposure recovery period in satellite groups: Recovery groups for control and high dose groups to investigate reversibility of any observed adverse effects.

Positive control:

None

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were examined for overt signs of toxicity, ill-health or behavioural change immediately before dosing and one to five hours after dosing during the working week. Animals were observed immediately before dosing and one hour after dosing at weekends and public holidays. During the treatment-free period, animals were observed twice daily, morning and afternoon (once daily at weekends).


BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were recorded on Day 0 (the first day of treatment) and on Days 7, 14, 21 and 28, and in recovery group animals on Days 35 and 42. Body weights were also recorded at terminal kill.


FOOD CONSUMPTION AND FOOD EFFICIENCY: Yes
- Food consumption for each cage group was recorded at intervals throughout the study.


WATER CONSUMPTION: Yes
- Time schedule for examinations: Daily for each cage group, by visual inspection of the water bottles for overt changes.

OPHTHALMOSCOPIC EXAMINATION: No data


HAEMATOLOGY: Yes
- Time schedule for collection of blood: Non-recovery test and control groups at the end of the treatment period on Day 28, and on all recovery group animals at the end of the treatment-free period (Day 42).
- Anaesthetic used for blood collection: No data
- Animals fasted: No
- Parameters checked in table [No.1] were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Non-recovery test and control groups at the end of the treatment period on Day 28, and on all recovery group animals at the end of the treatment-free period (Day 42).
- Animals fasted: No
- Parameters checked in table [No.1] were examined.


URINALYSIS: Yes
- Time schedule for collection of urine: All non-recovery test and control animals during week 4 and on all recovery group animals during week 6.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked in table [No.1] were examined.


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 2)
HISTOPATHOLOGY: Yes (see table 2)

Statistics:

Data were processed to give group mean values and standard deviation where appropriate.
Haematological, blood chemical, organ weight (absolute and relative to terminal bodyweight), weekly body weight gain and quantitative urinalytical data were assessed for non-recovery groups, and dose-response relationships by linear regression analysis followed by one way analysis of variance (ANOVA) incorporating Levene's test for homogeneity of variance. Where variances were shown to be homogenous, pairwise comparisons were conducted using Dunnett's test. In the case of recovery group data a two-tailed t-test incorporating Levene's test for homogeneity of variance was performed. Where Levene's test showed unequal variances among either non-recovery or recovery group data, the affected parameters were analysed using non-parametric methods: Kruskal-Wallis ANOVA and Mann-Whitney 'U' test.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

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

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: There were no deaths during the study. Animals of either sex treated with 1221 mg/kg bw/day showed increased salivation either before or for up to ten minutes after dosing from Day 9 onwards together with associated isolated incidents of red/brown staining of the external body surface and generalised fur loss. These findings had regressed in recovery group animals following cessation of treatment. Observations of this nature are often reported when the test material formulation is unpalatable or mildly irritant and, as such, are considered not to represent systemic toxicity. No treatment-related findings were detected in animals treated with 305 or 61 mg/kg bw/day.


BODY WEIGHT AND WEIGHT GAIN: No adverse effects on body weight and body weight gain were observed.


FOOD CONSUMPTION AND FOOD EFFICIENCY: There were no adverse effects on food consumption or food efficiency.


WATER CONSUMPTION: Daily visual inspection of water bottles revealed no intergroup differences.


HAEMATOLOGY: No toxicologically significant effects were detected in the haematological parameters measured.


CLINICAL CHEMISTRY: No toxicologically significant effects were detected in the blood chemistry parameters measured.


URINALYSIS: No toxicologically significant effects were detected in the urinalysis parameters measured.


ORGAN WEIGHTS: (see Table 3) Males treated with 1221 or 305 mg/kg bw/day showed a slight but statistically significant increase in absolute liver weight with a statistically significant increase in relative (to terminal body weight) liver weight noted in both sexes treated with 1221 and 305 mg/kg bw/day. In most cases individual values were within the normal range for rats of the strain and age used, and there were no histopathological correlates. However, the weight increases were apparently dose-related and an association with treatment could not be ruled out. Other isolated findings were considered to be incidental and unrelated to treatment.


GROSS PATHOLOGY: No treatment-related macroscopic abnormalities were found.


HISTOPATHOLOGY: Treatment-related kidney changes were detected. A higher incidence and marginally greater general severity of groups of basophilic tubules were observed for male rats dosed at 1221 mg/kg bw/day. Although this effect was equivocal it was to some extent confirmed by a similar residual finding among recovery group 1221 mg/kg bw/day male rats.

Dose descriptor:

NOAEL

Effect level:

ca. 1 221 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Dose descriptor:

NOEL

Effect level:

ca. 61 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Elevated liver weights with no histopathological changes, and most individual values within the normally expected range, and basophilic tubules in male kidneys without any renal dysfunction or degenerative changes at the two higher doses.

Critical effects observed:

not specified

Table 3: Incidence of selected pathologies

Parameter	n=5/sex	Dose level (mg/kg bw/day)
		Control	61	305	1221	Recovery control	Recovery 1221
Heart: focal myocarditis (minimal)	M	(2/5)	N/E	N/E	(2/5)	N/E	N/E
	F	(1/5)	N/E	N/E	(1/5)	N/E	N/E
Kidney: groups of basophilic tubules (minimal or slight)	M	-	(4/5)	(2/5)	(3/5) 2/5	(2/5)	(2/5) 3/5
	F	(1/5)	-	(1/5)	(2/5)	-	(4/5)
Kidney: hydronephrosis (minimal or slight)	M	-	-	-	(1/5)	1/5	-
	F	-	-	-	(1/5)	-	-
Kidney: cortical scarring	M	-	-	(1/5)	-	-	-
	F	-	-	-	-	-	-
Kidney: corticomedullary mineralization (minimal)	M	-	-	-	-	-	-
	F	-	-	-	(1/5)	-	(1/5)
Liver: mononuclear cell foci (minimal)	M	(5/5)	N/E	N/E	(5/5)	N/E	N/E
	F	(5/5)	N/E	N/E	(5/5)	N/E	N/E
Spleen:extramedullary haemopoiesis (minimal or slight)	M	(3/5) 2/5	N/E	N/E	(5/5)	N/E	N/E
	F	5/5	N/E	N/E	(5/5)	N/E	N/E

N/E not examined

- no change

( ) statistically significant change not considered to be toxicologically significant.

Conclusions:

In a GLP study (reliability score 2) conducted according to MHW test guidelines administration of Silquest A-1589 Silane by oral gavage for 28 days gave a NOAEL of 1221 mg/kg bw/day and a NOEL of 61 mg/kg bw/day in rats. The test substance was similar to the registered substance but contained a higher proportion of an S3 isomer.

Reference 4

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

20.04.1999 to 10.02.2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes (incl. QA statement)

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 Japan
- Age at study initiation: Five weeks.
- Weight at study initiation: Males: 139.5-162.9 g. Females: 119.6-144.0 g.
- Fasting period before study:
- Housing: Individually in hanging stainless steel cage with wire mesh floor.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: yes, but period not stated.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ± 2
- Humidity (%): 55 ± 10
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 17.06.1999 To: 29.07.1999

Route of administration:

oral: gavage

Vehicle:

olive oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The test substance was weighed accurately and dissolved with olive oil to make a 10 %w/v solution from which the 2.0, 0.4 and 0.08 % w/v solutions were prepared. 10 and 2.0 %w/v solutions were prepared weekly, and the 0.4 and 0.08 % w/v were prepared prior to use.


VEHICLE
- Justification for use and choice of vehicle (if other than water): No data.
- Concentration in vehicle: 10, 2.0, 0.4 and 0.08 %w/v.
- Amount of vehicle (if gavage): No data
- Lot/batch no. (if required): 004RRA
- Purity: No data

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

28 days (plus a 14 day recovery period with no treatment for the high dose group)

Frequency of treatment:

Daily

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

Six

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on the results of a 14 day preliminary study.
- Rationale for animal assignment (if not random): Random
- Rationale for selecting satellite groups: No data
- Post-exposure recovery period in satellite groups: yes, vehicle only and high dose group recovery groups.
- Section schedule rationale (if not random): No data

Positive control:

None

Observations and examinations performed and frequency:

The day of the initiation of dosing was defined as Day 1, and the day before as Day -1. The week of the initiation of the dosing period was defined as Week 1. Also, the next day of the final dosing was defined as Recovery day 1, and the week of the initiation of the recovery period as Recovery week 1.
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least daily.


DETAILED CLINICAL OBSERVATIONS: No data


BODY WEIGHT: Yes
- Time schedule for examinations: Before dosing on Day -2, then on Days 1, 3, 8, 12, 17, 21, 26 and 28, and during the recovery period on Days 1, 5, 10 and 14. Plus immediately before necropsy for calculation of relative organ weights.


FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/rat/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: No


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the termination of dosing and at the end of the recovery period.
- Anaesthetic used for blood collection: Yes (ether).
- Animals fasted: Yes, overnight (16-20 hours).
- How many animals: All survivors.
- Parameters checked in table 1 were examined. In addition a myelogram was performed as haematological abnormalities were noted in the preliminary toxicity study. Thin bone marrow smears were prepared from the left femurs in the first three animals of each group at the terminal necropsy of the dosing and recovery periods, and examined in the 1000 mg/kg and vehicle control groups on the terminal necropsy of the dosing period. Parameters examined were: myerobrasts, promyelocytes, myelocytes, metamyelocytes, stab neutrophils, segmented neutrophils, eosinophils, basophils, lymphocytes, plasmacytes, megakaryocytes, retoperitheliums, mastocytes, monocytes, proerythroblasts, basoerythroblasts, polychromatic erythroblasts, neuerythroblasts, and myeloblast series/erythroblasts series (M/E ratio).


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the termination of dosing and at the end of the recovery period.
- Animals fasted: Yes, overnight (16-20 hours).
- How many animals: All survivors.
- Parameters checked in table 1 were examined.


URINALYSIS: Yes
- Time schedule for collection of urine: At termination of the dosing and recovery periods.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked in table 1 were examined.


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 2)
HISTOPATHOLOGY: Yes (see table 2)

Statistics:

Data regarding body weights, food intakes, haematology, clinical chemistry, urinalysis and organ weights were analysed using the Bartlett's test for homogeneity of variance. If the variances were homogeneous at a significance level of 5%, one way analysis of variance was performed. If there was a significant difference in this analysis, the difference between the vehicle group and each of the treatment groups was analysed by the Dunnett's test (equal number of data). If the variances were not homogeneous the Kruskal-Wallis's test was used. If there was a significant difference in this analysis, the difference between the vehicle control group and each of the treatment groups was analysed by the nonparametric Dunnett's test (equal number of data).

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: During the dosing period salivation was observed in males of the vehicle control group (8/12), 8 mg/kg bw/day group (3/6), 40 mg/kg bw/day group (5/6), 200 mg/kg bw/day group (6/6) and 1000 mg/kg bw/day group (12/12). In females the salivation was observed in the vehicle control group (4/12), 8 mg/kg bw/day group (3/6), 40 mg/kg bw/day group (3/6), 200 mg/kg bw/day group (5/6) and 1000 mg/kg bw/day group (12/12). Staining around the nose and mouth was observed in 3/12 males and 1/12 females in the high dose group. Hair loss was also observed in the high dose males (2/12). These clinical signs were not observed in the recovery period. Salivation is commonly observed in gavage studies.


BODY WEIGHT AND WEIGHT GAIN: There were no abnormalities in either the dosing or recovery periods.


FOOD CONSUMPTION: There were no abnormalities in either the dosing or recovery periods.


HAEMATOLOGY: There were no abnormalities in males. At termination of dosing there was a decrease in red blood cell count, and an increase in activated thromboplastin time in high dose females. At the end of the recovery period an increase in red blood cell count and a decrease in mean corpuscular haemoglobin was noted in the high dose group.


CLINICAL CHEMISTRY: At the end of the dosing period there was an increase in calcium level in the high dose group males. In high dose females there were increases in GPT and gamma-GTP activities, total cholesterol, total protein, albumin levels, and a decrease in alkaline phosphatase activity. There was also a tendency towards increased GPT activity due to an increase in one animal of the 200 mg/kg bw/day. There were no such findings at the end of the recovery period.


URINALYSIS: There was a tendency towards increased ketone bodies in the high dose groups for males and females, and the 200 mg/kg bw/day group for females at the end of the dosing period. There were no such findings at the end of the recovery period.


ORGAN WEIGHTS: Small testes were observed in one male of the vehicle control group at the end of the recovery period, but these were not analysed statistically as they were considered to be a malformation. In males at termination of dosing, increases in relative liver weights were noted in the 200 and 1000 mg/kg bw/day groups. Decreased absolute testis weights were noted in the 8 and 40 mg/kg bw/day groups, and decreased relative kidney weights were noted in the 200 mg/kg bw/day group. In females there was an increase in absolute liver weight in the 200 mg/kg bw/day group, and an increase in absolute and relative liver weights in the 1000 mg/kg bw/day group. There were no such findings at the end of the recovery period.


GROSS PATHOLOGY: At the end of the dosing period males had enlargement (2/6) of the liver and loss of hair (1/6) in the highest dose group. Females of the highest dose group (4/6) had liver enlargement. At the termination of the recovery period. No abnormalities were observed in females, but there was one male of the vehicle control group that had small testes.


HISTOPATHOLOGY: NON-NEOPLASTIC: Table 3 summaries the histopathology findings.

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

Table 3: Incidence of selected pathologies

Parameter	n=6/sex		Dose level (mg/kg bw/day)
		Control		8	40	200	1000	Recovery control	Recovery 1000
Liver enlargement	M	0		0	0	0	2	0	0
	F	0		0	0	0	4	0	0
Testes - small	M	0		0	0	0	0	1	0
	F	-		-	-	-	-	-	-
Skin - Loss of hair	M	0		0	0	0	1	0	0
	F	0		0	0	0	0	0	0
Liver – Centrilobular hypertrophy of hepatocytes	M	0		-	-	-	4/6 (+)	0	0
	F	0		-	-	-	3/6 (+)	0	0
Centrilobular lipid droplets of hepatocytes	M	0		-	-	0	0	0	0
	F	0		-	-	3/6 (+)	0	0	0
Disseminated microgranuloma	M	1/6 (+)		-	-	1/6 (+)	0	1/6 (+)	0
	F	0		-	-	0	2/6 (+)	1/6 (+)	0
Periportal lipid droplets of hepatocytes	M	1/6 (+)		-	-	0	0	0	0
	F	1/6 (+), 1/6(++)		-	-	1/6 (±), 2/6 (+)	3/6 (+), 2/6 (++)	0	0
Periportal microgranuloma	M	0		-	-	0	0	0	0
	F	1/6 (++)		-	-	1/6 (+)	2/6 (+)	0	0
Single cell necrosis of hepatocytes	M	0		-	-	0	0	0	1/6 (+)
	F	0		-	-	0	0	0	2/6 (+)
Kidney – Basophilic tubules	M	0		-	-	0	4/6 (+)	0	1/6 (±), 2/6 (+)
	F	0		-	-	0	1/6 (±)	0	1/6 (±), 2/6 (+)
Increased eosinophilic bodies	M	0		-	-	0	0	0	2/6 (±)
	F	0		-	-	0	0	0	0
Increased hyaline droplets	M	0		-	-	0	1/6 (± ), 1/6 (+)	0	3/6 (±)
	F	0		-	-	0	0	0	0
Subcapsular solitary cyst	M	1/6 (+)		-	-	0	0	0	0
	F	0		-	-	0	0	0	0
Testes – diffuse atrophy of seminiferous tubules	M	-		-	-	-	-	1/1 (+++)	-
	F	-		-	-	-	-	-	-
Leydig cell hyperplasia	M	-		-	-	-	-	1/1 (++)	-
	F	-		-	-	-	-	-	-
Skin – scab formation	M	-		-	-	-	1/1 (+)	-	-
	F	-		-	-	-	1/1	-	-

± very slight, + slight, ++ moderate, +++ severe

Conclusions:

In a well conducted and documented 28-day repeated dose oral gavage study (reliability score 1) conducted according to OECD 407 and GLP, the NOAEL for Si-75 was 200 mg/kg bw/day in rats. This was based on histopathological changes in the liver and kidney.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

200 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

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

No repeated dose toxicity data are available for the registered substance, therefore this endpoint is addressed using weight of evidence from reliable data for a number of related substances. The composition of these related substances includes different concentrations of both isomers present in the registration substance, and the available data indicate that there are no differences in systemic toxicity for constituents with different numbers of sulfur atoms in a (poly)sulfide chain. Since the three test substances cover the composition range of the registered substance, and no significant adverse effects were seen in any study up to a high dose level of 1000 mg/kg/day, additional testing with the registration substance itself is not warranted.

Four relevant 28-day oral toxicity studies are available on which to base a weight of evidence approach for the registered substance.

There is a testing proposal for a 90 -day repeated dose toxicity test with polysulfides, bis[3-(triethyoxysilyl)propyl (CAS No 211519-85-6).

Justification for read-across from Polysulfides, bis[3-(triethoxysilyl) propyl] (Polysulfides; CAS 211519-85-6) and 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2; CAS 56706-10-6)

(a) Structural similarity

Both the registration substances and the read-across substances are structurally similar; all contain bis[3-(triethoxysilyl)propyl]- structures with the two (triethoxysilyl)propyl groups linked by di- or polysulfide groups. Details on the composition of the three materials is given in Section 1.4 of the CSR but in summary the registration substance is a multiconstituent substance comprising 50-65% by weight of disulfide, 30-40% by weight of trisulfide and 5-15% tetrasulfide. S2 is a monoconstituent substance comprising >80% by weight of disulfide, with approximately 10-20% of the trisulfide as an impurity whereas Polysulfides is multiconstituent comprising a mixture of di- (S2, 15-25% w/w), tri- (S3, 30-35% w/w) and tetrasulfides (S4, 20-30% w/w). Additional information including structural diagrams is included in the attached report.

S2, S3 and S4 can be considered as toxicologically equivalent; this is discussed further in (c) and (d).

(b) Similar physicochemical characteristics

The key physicochemical parameters of the substances are summarised in the attached document. The substances all hydrolyse, and the products of hydrolysis are bis(3-(trihydroxysilyl)propylsulfides (with a varying number of sulfur atoms) and ethanol. The key physicochemical properties of the silanol hydrolysis products are also included in the attached document. Information on the physicochemical properties of the individual constituents can be found in Section 1.4.

Summary of key physicochemical parameters

Abbreviation	Low purity S2^1	S2	S2/S3	Polysulfides
CAS Number	n/a	56706-10-6	n/a	211519-85-6
EC number	n/a	260-350-7	915-748-1	915-673-4
Status	Not for registration	Registered	Registered	Registered
Chemical Name	n/a^1	4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane	Reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane	Reaction mass of 4,4,15,15-tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disilaoctadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane and 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane
Composition	5-10% S1; 65-70% S2; 15-20% S3	80-90% S2	50-65% S2; 30-40% S3	15-25% S2; 30-35% S3; 20-30% S4; 15-30% Sn n>4[1]
Molecular weight	443-507 g mol^-1	475 g mol^-1	475-507 g mol^-1	475-539
log Kow(parent)	4.2-5.2 (prediction)	5.2 (prediction)	5.2 (prediction)	5.2 (prediction)
log Kow(silanol hydrolysis product)	-3.0 (prediction)	-3.0 (prediction)	-3.0 (prediction)	-3.0 (prediction)
Water sol (parent)	<1 mg/l (prediction)	≤1 mg/l (measured)	1 mg/l (prediction)	<1 mg/l (measured)
Water sol (silanol hydrolysis product)	1E+06 mg/l (prediction) The concentration dissolved in water is limited to about 1000 mg/l by condensation reactions.	1E+06 mg/l (prediction) The concentration dissolved in water is limited to about 1000 mg/l by condensation reactions.	1E+06 mg/l (prediction) The concentration dissolved in water is limited to about 1000 mg/l by condensation reactions.	1E+06 mg/l (prediction) The concentration dissolved in water is limited to about 1000 mg/l by condensation reactions.
Vapour pressure (parent)	9 Pa (read-across, supported by predictions)	9 Pa (measured)	9 Pa (read-across, supported by predictions)	9 Pa (read-across, supported by predictions)
Vapour pressure (silanol hydrolysis product)	2.9E-05 Pa at 25°C (calculated)	2.9E-05 Pa at 25°C (calculated)	2.9E-05 Pa at 25°C (calculated)	2.9E-05 Pa at 25°C (calculated)
Hydrolysis t1/2at pH 7 and 20-25°C	40-90 hours (prediction)	40-90 hours (prediction)	40-110 hours (prediction)	40 – 130 hours (prediction)
Hydrolysis t1/2at pH 2 and 37.5°C	11-14 seconds (prediction)	11 - 14 seconds (prediction)	11-18 seconds (prediction)	11-20 seconds (prediction)

[1]The substance tested in the OECD 414 study with Polysulfides contained 18% S2; 30% S3; 24% S4; 27% Sn where n > 4

 

Due the very similar chemical structures, the registration and read-across substances are predicted to have near identical physicochemical properties.

 

The substances hydrolyse very rapidly to silanols and ethanol at pH 2 and 37.5°C (the conditions relevant for oral exposure). The silanol hydrolysis products are predicted to have near identical physicochemical properties.

(c) Similar toxicokinetics

Based on the predicted physicochemical properties it can be inferred that the substances in the sulfidosilane group behave similarly with respect to adsorption, distribution and excretion. The toxicokinetic properties of S2, reaction mass S2/S3 and polysulfides have been predicted based on the physicochemical properties and estimated using pharmacokinetic or toxicokinetic (PBTK) prediction models. See Section 5.1.3 for more information.

(d) Similar acute and repeated dose systemic toxicity

Acute oral and dermal toxicity studies are available for both read-across substances and for low purity S2. No mortalities or systemic effects were observed with either substance in any of the studies, at doses greater than or equal to 2000 mg/kg. Furthermore, there were no effects in an acute inhalation study with the read-across substance. Together these results indicate that the sulfidosilanes have a low acute toxicological profile.

Four relevant 28-day oral toxicity studies are available, two on each of the read-across substances. These are summarised below.

In the first study with CAS 56706-10-6 (Hita Labs., 2000a) four dose groups, a recovery group and a vehicle control group were examined. The high dose was 1000 mg/kg bw/day, and the three lower doses 200, 40 and 8 mg/kg bw/day and a high dose (1000 mg/kg bw/day) recovery group. The test material contained >80% of the S2 constituent, and small amounts of the monosulfide (S1) and polysiloxane impurities. A 14-day recovery period was included. In this study no deaths occurred, there were no abnormalities in clinical signs, body weights and food intakes during the dosing period. The NOAEL determined in this study was 200 mg/kg bw/day based on the histopathological changes centrilobular hypertrophy of the hepatocytes and basophilic tubules in the kidney in the 1000 mg/kg bw/day males and females, and hyaline droplets in the kidney in the 1000 mg/kg bw/day males, and periportal lipid droplets of the hepatocytes in the 1000 mg/kg bw/day females.

In the recovery test, basophilic tubules in the kidney of male and females, and increased hyaline droplets in the kidney of males remained in the 1000 mg/kg bw/day groups. The other treatment -related changes at the termination of the dosing period were not observed after recovery period. The histopathological effects in the high dose group (1000 mg/kg bw/day) are of minor toxicological relevance and did not result in any clinical symptoms. The experience of the lead registrant is that 4 weeks or longer are better to demonstrate reversibility of effects. If a minor toxicological effect is reversible it is not an adverse effect.  In summary this study gives no indication of a severe toxicological concern even in the high dose group. Although the study was conducted according to current OECD test guideline and GLP, it is assigned reliability 2 because a thorough histopathological investigation of required tissues was not carried out.

In a second study (SafePharm, 2002), which was conducted in accordance with Japanese national guidelines for 28-day oral toxicity testing, the test material contained mainly the S2 and S3 constituents, with a small amount of S1 impurity. Dose levels were 0, 61, 305, 1221 mg/kg bw/day. There were no deaths, significant clinical signs or effects on body weight, urinalysis, clinical chemistry and haematological parameters measured. Males treated with 1221 or 305 mg/kg bw/day showed a slight but statistically significant increase in absolute liver weight with a statistically significant increase in relative (to terminal body weight) liver weight noted in both sexes treated with 1221 and 305 mg/kg bw/day. In most cases individual values were within the normal range for rats of the strain and age used, and there were no histopathological correlates. However, the weight increases were apparently dose-related and an association with treatment could not be ruled out. Other isolated findings were considered to be incidental and unrelated to treatment.

Treatment-related kidney changes were detected. A higher incidence and marginally greater general severity of groups of basophilic tubules were observed for male rats dosed at 1221 mg/kg bw/day. Although this effect was equivocal it was to some extent confirmed by a similar residual finding among recovery group 1221 mg/kg bw/day male rats. The NOAEL was judged to be 1221 mg/kg bw/day and the NOEL was 61 mg/kg bw/day.

Two 28-day studies are also available for the related substance polysulfides, bis[3-(triethoxysilyl)propyl] (CAS 211519 -85 -6) which is a reaction mass containing principally the S2 (15-60%), S3 (25-40%) and S4 (5-30%) constituents.

In the first (Hita Labs., 2000b) four dose groups, a recovery group and a vehicle control group were examined. The high dose was 1000 mg/kg bw/day, and the three lower doses 200, 40 and 8 mg/kg bw/day and a high dose (1000 mg/kg bw/day) recovery group. The recovery period was 14 days. In this study no death occurred, there were no abnormalities in clinical signs, body weights and food intakes during the dosing period. The NOAEL determined in this study was 200 mg/kg/day based on the histopathological changes centrilobular hypertrophy of the hepatocytes and basophilic tubules in the kidney in the 1000 mg/kg bw/day males and females, and hyaline droplets in the kidney in the 1000 mg/kg bw/day males, and periportal lipid droplets of the hepatocytes in the 1000 mg/kg bw/day females.

In the recovery test, basophilic tubules in the kidney of male and females, and increased hyaline droplets in the kidney of males remained in the 1000 mg/kg bw/day groups. The other treatment-related changes at the termination of the dosing period were not observed after recovery period.

In the other study with the polysulfides (Degussa AG, 1983), a limit test at 2309 mg/kg bw/day was carried out. The only treatment related effects were related to organ weights. There was an increase in relative liver weight in both sexes of treated animals. The absolute weight of the left kidneys was significantly different within the female recovery group as a consequence of a low, abnormal kidney weight of two control animals. The weight of both adrenal glands was relatively and absolutely reduced in the male substance treated animals compared with the controls. The differences in liver and adrenal gland weights were reversed by the end of the recovery period. The NOAEL was reported as 2309 mg/kg bw/day.

There were no adverse effects on any of the reproductive organs examined in any of the studies described above.

The studies clearly show that the substances tested have a similar toxicological profile.

Summary of repeated dose toxicity data

Test substance	Dose levels	Recovery group included?	Results	Reference
S2	8, 40, 200 and 1000 mg/kg bw/day	Yes	NOAEL: 200 mg/kg bw/day   Basis:centrilobular hypertrophy of the hepatocytes and basophilic tubules in the kidney in the 1000 mg/kg bw/day males and females, and hyaline droplets in the kidney in the 1000 mg/kg bw/day males (effect not relevant for humans), and periportal lipid droplets of the hepatocytes in the 1000 mg/kg bw/day females.   Recovery: basophilic tubules in the kidney of male and females, and increased hyaline droplets in the kidney of males remained in the 1000 mg/kg bw/day groups. The other treatment -related changes at the termination of the dosing period were not observed after recovery period.	Hita Laboratory (2000a)
S2	0, 61, 305, 1221 mg/kg bw/day	No	NOAEL: ca. 1221 mg/kg bw/day   Basis: Elevated liver weights with no histopathological changes, and most individual values within the normally expected range, and basophilic tubules in male kidneys without any renal dysfunction or degenerative changes were not considered adverse effects.	McRae, L., Mullee, D. and Brooks, P.N. (2002)
Polysulfides	8, 40, 200 and 1000 mg/kg bw/day	Yes	NOAEL: 200 mg/kg bw/day   Basis: liver hypertrophy at 1000 mg/kg bw/day. Kidney effects assumed not relevant to humans.   Recovery:basophilic tubules in the kidney of male and females, and increased hyaline droplets in the kidney of males remained in the 1000 mg/kg bw/day groups. The other treatment-related changes at the termination of the dosing period were not observed after recovery period.	Hita Laboratory (2000b)
Polysulfides	2309 mg/kg bw/day (limit test)	Yes	NOAEL: ≥2309 mg/kg bw/day   Basis: No irreversible adverse effects.   Recovery: differences in liver and adrenal gland weights were reversed by the end of the recovery period	Degussa AG (1983)

Consideration of possible mixture effects

When considering the toxicity of mixtures, it is necessary to consider the possibility that the toxicity of the mixture is greater than would be expected based on the sum of the constituents (synergistic effects). The sulfidosilane substances Polysulfides, S2/S3 reaction mix and low purity S2 are multiconstituent substances. However, mixture effects are considered unlikely based on the high degree of similarity between the different constituents. The structural similarity of the constituents makes it probable that toxicity is exerted by each constituent of the multiconstituent substances with the same mode of action. This would make the effects additive, rather than synergistic. Evidence of this can be seen in the 28-day repeated dose toxicity studies where both the type of effects (adaptive changes in liver and kidney) and the effect levels seen in studies on S2, low purity S2 and Polysulfides are very similar.

If mixture effects did occur for the Polysulfides, this would probably make the Polysulfides more toxic than the submission substance. It is very unlikely that mixture effects would lead to a reduction in toxicity. Therefore, the proposed read-across is considered to be conservative.

(e) Justification of read across conclusions

The structural similarities between the source and the target substances and the similarities in their breakdown products presented above support the read-across hypothesis. Adequate, reliable and available scientific information indicates that the source and target substances and their abiotic degradation products follow similar metabolic pathways resulting in identical products of metabolism, and therefore have similar toxicity profiles.

The constituents of the target substance are constituents of the source substance polysulfides, and are also present in the source substances S2 and low purity S2. Information on hydrolysis indicates that, under the conditions in the stomach in oral toxicity studies, source and target substances are subject to rapid hydrolysis to ethanol, and to silanol hydrolysis products that differ only in the number of sulfur atoms in the sulfide bridge. Thus, systemic exposure following oral administration will be predominantly to these breakdown products.

Information on sulfur metabolism indicates that the substances and the silanol hydrolysis products of source and target substances will follow similar biotransformation pathways producing identical metabolites. 

No classification and labelling criteria are fulfilled by the source or target substances.

Justification for classification or non-classification

No serious adverse effects were observed in repeated dose oral toxicity studies in the rat with closely related test substances. Based on this weight of evidence, the registered substance does not require classification for Specific Target Organ Toxicity according to Regulation (EC) No 1272/2008.