Octaphenylcyclotetrasiloxane

Endpoint summary

Description of key information

In the key Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test, conducted according to OECD Test Guideline 422 and in compliance with GLP, the reported NOAEL value for octaphenylcyclotetrasiloxane for repeated dose toxicity was ≥1000 mg/kg bw/day. No adverse effects were observed in any of the test animals (Charles River, 2017).

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 November 2016 to 09 February 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1996

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3650, Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test

Version / remarks:

2000

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OECD 421, Reproduction/Developmental Toxicity Screening Test

Version / remarks:

1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3550, Reproduction/Developmental Toxicity Screening Test

Version / remarks:

2000

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3050, Repeated dose 28-day oral toxicity study in rodents

Version / remarks:

2000

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: at room temperature
- Stability under test conditions: stable until 31 March 2018
- Solubility and stability of the test substance in the solvent/vehicle: Stability in propylene glycol for at least 24 hours at room temperature and for at least 8 days in a refrigerator is confirmed over the concentration range 1 to 200 mg/mL

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Formulations (w/w) were prepared daily within 6 hours prior to dosing and were homogenized to a visually acceptable level. Adjustment was made for specific gravity of the vehicle. No correction was made for the purity/composition of the test item.
- Preliminary purification step (if any): No correction factor required.
- Final dilution of a dissolved solid, stock liquid or gel: not applicable
- Final preparation of a solid: not applicable

FORM AS APPLIED IN THE TEST (if different from that of starting material): diluted in propylene glycol

Species:

rat

Strain:

other: Crl:WI(Han)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Germany
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation: males: approximately 10 weeks; females: approximately 11 weeks
- Weight at study initiation: not specified
- Fasting period before study: no
- Housing: Animals were housed in groups of 5 animals/sex/cage in Macrolon plastic cages during pre-mating period. This is also applicable for Recovery animals throughout the complete study. During mating period Main females were caged together with Main males on a one-to-one-basis in Macrolon plastic cages. At post-mating period Main males were housed in their home cage (Macrolon plastic cages, MIV type, height 18 cm) with a maximum of 5 animals/cage. Main females were individually housed in Macrolon plastic cages. During lactation Main females were housed in Macrolon plastic cages (MIII type, height 18 cm). Pups were housed with the dam, except during locomotor activity monitoring of the dams, when the pups were kept warm in their home cage using bottles filled with warm water.
- Diet (e.g. ad libitum): pelleted rodent diet, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: 5 days

DETAILS OF FOOD AND WATER QUALITY: Diet, water, bedding and cage-enrichment/nesting material evaluation for contaminants and/or nutrients was performed according to facility standard procedures. There were no findings that could interfere with the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 to 24°C,
- Humidity (%): 40 to 70%
- Air changes (per hr): 10 room air changes/hour
- Photoperiod (hrs dark / hrs light): 12-hour light/12-hour dark

Route of administration:

oral: gavage

Vehicle:

propylene glycol

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: Formulations (w/w) were prepared daily within 6 hours prior to dosing and were homogenized to a visually acceptable level. Adjustment was made for specific gravity of the vehicle. No correction was made for the purity/composition of the test item.

VEHICLE
- Justification for use and choice of vehicle (if other than water): Based on trial formulations performed at Charles River Den Bosch.
- Concentration in vehicle: not specified
- Amount of vehicle (if gavage): not specified
- Lot/batch no. (if required): not specified
- Purity: not specified

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of formulations were analyzed for homogeneity (highest and lowest concentration) and accuracy of preparation (all concentrations). The accuracy of preparation was considered acceptable if the mean measured concentrations were 85-115% of the target concentration. Homogeneity was demonstrated if the coefficient of variation was ≤ 10%. Formulations were considered stable if the relative difference before and after storage was maximally 10%.

Duration of treatment / exposure:

Main and Recovery males: 29 to 30 days
Main females with offspring: 41-45 days
Main females that failed to deliver: 41 to 45 days
Recovery females: 44 days

Frequency of treatment:

Once daily for 7 days per week

Dose / conc.:

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

Dose / conc.:

300 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:

Main males: 10
Main females: 10
Recovery animals: 5

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on the results of a 14-day dose range finding study in which no signs of toxicity were observed up to 1000 mg/kg, the dose levels for this combined 28-day oral gavage study with reproduction/developmental toxicity screening test were selected to be 100, 300 and 1000 mg/kg.
- Rationale for animal assignment (if not random): random
- Rationale for selecting satellite groups: Recovery animals were selected for the negative control and high dose group.
- Post-exposure recovery period in satellite groups: 14 days
- Section schedule rationale (if not random): random

Positive control:

Not used.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Cage side observations checked included: The animals were checked for mortality and viability at least twice daily,

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: At least once daily from start of treatment onwards up to the day prior to necropsy, detailed clinical observations were made for all animals. The following functional observations tests were performed on each individual animal of the selected 5 Main animals/sex/group and all Recovery animals: hearing ability, pupillary reflex, fore- and hind-limb grip strength, locomotor activity. The selected Main males and all Recovery males were tested during Week 4 of treatment and the selected Main females were tested once during the last week of lactation (from lactation Day 4 onwards), and all Recovery females were tested on the first day a Main female was tested. Motor activity measurements were also conducted for all Recovery males at the end of the Recovery period since a potential increase in motor activity was recorded for males at 300 and 100 mg/kg at the end of the treatment period.

BODY WEIGHT: Yes
- Time schedule for examinations: Males and females were weighed on the first day of exposure (prior to first dosing) and weekly thereafter. Mated Main females were weighed on Days 0, 4, 7, 11, 14, 17 and 20 postcoitum and during lactation on PND 1 and 4.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): not applicable

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Not applicable

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: From the selected 5 animals/sex/group, blood samples were collected on the day of scheduled necropsy at the end of the treatment period. From all Recovery animals, blood samples were collected at the end of the treatment period and on the day of scheduled necropsy at the end of the recovery period.
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes
- How many animals: selected 5 animals/sex/group and all Recovery animals
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: From the selected 5 animals/sex/group, blood samples were collected on the day of scheduled necropsy at the end of the treatment period. From all Recovery animals, blood samples were collected at the end of the treatment period and on the day of scheduled necropsy at the end of the recovery period.
- Animals fasted: Yes
- How many animals: selected 5 animals/sex/group and all Recovery animals
- Parameters checked in table [No.1] were examined.

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

IMMUNOLOGY: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table No 2)

HISTOPATHOLOGY: Yes (see table No 2)

Statistics:

- If the variables could be assumed to follow a normal distribution, the Dunnett-test based on a pooled variance estimate was applied for the comparison
of the treated groups and the control groups for each sex.
- The Steel-test was applied if the data could not be assumed to follow a normal distribution.
- The Fisher Exact-test was applied to frequency data.
- The Kruskal-Wallis nonparametric ANOVA test (Ref. 5) was applied to motor activity data to determine intergroup differences. In case intergroup differences were seen, the Wilcoxon test was applied to compare the treated groups to the control group.

Clinical signs:

no effects observed

Description (incidence and severity):

No treatment-related clinical signs were noted during daily clinical observations or during weekly arena observations.
Clinical signs noted incidentally occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study and showed no dose-related trend. At the incidence observed, these were considered to be unrelated to treatment.

Mortality:

no mortality observed

Description (incidence):

No mortality occurred during the study period that was considered to be related to treatment with the test item.
One female at 300 mg/kg (no.85) was euthanized in extremis on Day 3 of the pre-mating period when she showed laboured respiration and gasping. This was not test item-related but due to the gavage procedure as was evident from the presence of a (part of the) dosing tube in the larynx at macroscopic examination.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Body weight and body weight gain were not considered affected by treatment.

Food efficiency:

no effects observed

Description (incidence and severity):

No treatment-related changes in food consumption before or after allowance for body weight were noted.

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

Haematological parameters were not considered affected by treatment.
Statistically significant variations between treated rats and controls were limited to a lower percentage of eosinophils in 1000 mg/kg females at the end of the recovery period. Based on the minor magnitude of the difference and the absence of a treatment-related change in eosinophils at the end of the treatment period, this finding was considered to be unrelated to treatment.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

At 1000 mg/kg, higher total protein and glucose was recorded for Recovery females at the end of treatment. Means remained within the range considered normal for rats of this age and strain. Similar but not statistically significant differences were also recorded at the end of the recovery period. These differences were not apparent for Main females at the end of treatment.

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

At the end of the treatment period, mean total movements were statistically significantly higher in males at 300 and 1000 mg/kg than in controls. Mean ambulations were higher (not statistically significantly) in males at 1000 mg/kg. Mean values in treated males remained within the normal range for male rats of this strain and age, and showed a normal motor activity habituation profile with a decreasing trend over the duration of the test period. At the end of the recovery period, motor activity was similar in treated males and controls.
Motor activity of females was not considered affected by treatment and showed a normal motor activity habituation profile.
Hearing ability, pupillary reflex and static righting reflex were normal in all examined animals. Grip strength was not affected by treatment.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

There were no test item-related alterations in organ weights.

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no treatment-related gross observations.

Neuropathological findings:

not examined

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

There were no test item-related microscopic observations.

Details on results:

The concentrations analyzed in the formulations of Groups 2, 3 and 4 were in agreement with target concentrations (i.e. mean accuracies between 85% and 115%).

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed.

Critical effects observed:

no

Conclusions:

In the Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test, the reported NOAEL value for octaphenylcyclotetrasiloxane for repeated dose toxicity was ≥1000 mg/kg bw/day. No adverse effects were observed in any of the test animals.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 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

The test item, octaphenylcyclotetrasiloxane formulated in propylene glycol, was administered daily by oral gavage to SPF-bred Wistar Han rats. One control group and three treated groups were tested, each consisting of 10 males and 10 females. An extra 5 animals per sex in the control and high dose group were allowed 14 days of recovery.

The animals were examined for mortality / viability, clinical signs (daily), functional observations (end of treatment), locomotor activity (end of treatment in both sexes, end of recovery in males), body weight and food consumption (at least at weekly intervals), clinical pathology (end of treatment and recovery), macroscopy at termination, organ weights and histopathology on a selection of tissues. In addition, the following reproduction/developmental parameters were determined: mating and fertility indices, precoital time, number of corpora lutea and implantation sites, gestation index and duration, parturition, maternal care, sex ratio and early postnatal pup development (mortality, clinical signs, body weight, anogenital distance and macroscopy). Formulations were analyzed twice during the study to assess accuracy and homogeneity.

No adverse effects were observed in any of the test animals and the reported NOAEL value for octaphenylcyclotetrasiloxane for repeated dose toxicity was ≥1000 mg/kg bw/day (the highest dose tested) (Charles River, 2017).

Justification for classification or non-classification

Based on the available data for octaphenylcyclotetrasiloxane, no classification for specific target organ toxicity following repeated exposure is required according to Regulation (EC) No 1272/2008.