Polysulfides, bis[3-(triethoxysilyl)propyl]

Endpoint summary

Description of key information

The key 28-day repeated dose oral gavage study with bis[3-(triethoxysilyl)propyl]polysulfides (CAS No. 211519-85-6, EC No. 915-673-4) was conducted according to a national standard method equivalent to OECD Test Guideline 407 and in compliance with GLP (Hita Laboratory, 2000a). In this study, the systemic NOAEL 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 also were effects in the kidneys of male rats from 200 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 reviewer.

There are no repeated dose data for the dermal and inhalation routes.

[copy OECD 443 note from S2]

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

Study period:

07.02.2000 to 26.07.2000

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

A restriction in the study was the lack of full histopathology on the 32 tissues required by OECD TG 407.

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: To:

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 pre-test 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 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's 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's test. Furthermore, FOB data were analysed with Kruskal-Wallis test, and if significant difference was obtained, data were further analysed with nonparametric Dunnett's test.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

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.

Mortality:

mortality observed, treatment-related

Description (incidence):

There were no deaths related to treatment.

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

Description (incidence and severity):

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 biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

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 findings:

no effects observed

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

No adverse effect on sensory activity and locomotor activity.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

At the end of the treatment period 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 pathological findings:

effects observed, treatment-related

Description (incidence and severity):

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.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

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 at 1000 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.

Histopathological findings: neoplastic:

not examined

Other effects:

not specified

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

organ weights and organ / body weight ratios

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

Key result

Critical effects observed:

not specified

Conclusions:

In a 28-day repeated dose oral gavage study with bis[3-(triethoxysilyl)propyl]polysulfides conducted according to a national standard method equivalent to OECD Test Guideline 407 and in compliance with GLP, the systemic NOAEL 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 also were 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 reviewer.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

200 mg/kg bw/day

Study duration:

subacute

Species:

rat

System:

hepatobiliary

Organ:

liver

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

Only subacute oral data are available for bis[3-(triethoxysilyl)propyl]polysulfides in repeated dose toxicity tests. However, a 90-day OECD Test Guideline 408 study for bis[3-(triethoxysilyl)propyl]polysulfides is planned, awaiting final authorization from ECHA on the test proposal.

 

The key study was selected as it was the most reliable study available and gave the lowest systemic NOAEL (Hita Laboratory, 2000a). Both of the available studies on the registered substance are considered reliable with restrictions due to the lack of full histopathology in the 32 tissues as required by OECD Test Guideline 407.

 

In the key 28-day repeated dose toxicity study with bis[3-(triethoxysilyl)propyl]polysulfides, four dose groups (8, 40, 200 and 1000 mg/kg bw/day), a 14-day recovery group (1000 mg/kg bw/day) and a vehicle control group were examined. In this study, no deaths occurred and there were no adverse findings in clinical observations, body weights and food intakes during the dosing period. 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. Centrilobular hepatocyte hypertrophy in males and females, and basophilic renal tubules in males were observed 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 (Hita Laboratory, 2000a).

 

Therefore, the majority of the treatment-related changes present at the termination of the dosing period were not observed after the 14 -day recovery period. The histopathological effects observed in the high dose group (1000 mg/kg bw/day) are of minor toxicological relevance and did not result in any clinical symptoms.

 

The NOAEL determined in this study was 200 mg/kg bw/day based on the enlarged liver and histopathological changes (centrilobular hypertrophy) of the hepatocytes in the 1000 mg/kg bw/day males and females (Hita Laboratory, 2000a).

 

A supporting study also was available for repeated dose toxicity via the oral route (Degussa Institute of Toxicology, 1983). This 28-day repeated dose toxicity limit study with bis[3-(triethoxysilyl)propyl]polysulfides conducted according to OECD Test Guideline 407 and in compliance with GLP, the test material was administered to Wistar rats (10/sex/dose) for 28 days by oral gavage. Twenty (20) animals were treated with 2309 mg/kg bw/day (2.15 ml/kg) of test substance, and 20 were control animals that received an equal volume of tap water. Following 28 days of treatment, 10 animals from each group were observed for an additional 14 days without any further treatment (recovery groups). There were no deaths or clinical findings. Nor were there any adverse treatment-related effects on food consumption, body weight, reflexes, haematology, clinical chemistry, gross pathology, histopathology and organ weights. The systemic NOAEL was therefore ≥ 2309 mg/kg bw/day.

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. The liver effects observed are likely to be adaptive rather than adverse; however, in the absence of a sub-chronic test results (planned OECD Test Guideline 408), the conservative systemic NOAEL is based on this effect.

Justification for classification or non-classification

Based on the currently available data, bis[3-(triethoxysilyl)propyl]polysulfides does not require classification for repeated dose toxicity according to Regulation (EC) No. 1272/2008. The classification for this endpoint will be re-visited upon completion of the planned OECD Test Guideline 408 study.