Decamethylcyclopentasiloxane

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

07.11.1988 to 10.02.1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Version / remarks:

version from May 12, 1981

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Decamethylcyclopentasiloxane

EC Number:

208-764-9

EC Name:

Decamethylcyclopentasiloxane

Cas Number:

541-02-6

Molecular formula:

C10H30O5Si5

IUPAC Name:

2,2,4,4,6,6,8,8,10,10-decamethyl-1,3,5,7,9,2,4,6,8,10-pentoxapentasilecane

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Stamm Bor:WISW (SPF-Cpb), Versuchstierzucht Winkelmann, Borchen, Germany
- Age at study initiation: 7 weeks
- Weight at study initiation: Males: 129-165 g; Females: 102-141 g
- Fasting period before study:
- Housing: Makrolon Type II cages, 5 animals per cage
- Diet (e.g. ad libitum): Ad libitum, nutrition composition and contaminants are given
- Water (e.g. ad libitum): Ad libitum,
- Acclimation period: 8 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22± 2
- Humidity (%): ca. 50
- Air changes (per hr): ca. 10
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 07.11.1988 To: 10.02.1989

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

Vehicle dispensed daily by gavage, reference animals were given water by the same route.
Dose volume: Since 100% concentration of substance was administered, dose volume changed with dose:
0.1 ml/kg
0.33 ml/kg
1 ml/kg

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

no details given on verification of dose; the volume of substance was measured

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

No. of animals per sex per dose:

Ten

Control animals:

other: control animals were given dose of water by the same route.

Details on study design:

- Dose selection rationale: Dose was selected based on published and non-published results from chemically similar substance studies. 1000 mg/kg was fixes as upper limit following OECD recommendation. A factor of 3 was used for lower doses.
- Rationale for animal assignment (if not random): Randomization was carried out with computerized method
- Rationale for selecting satellite groups: No satellite groups
- Post-exposure recovery period in satellite groups: No

Positive control:

None

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily during the week, once daily on Saturdays and Sundays

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly

BODY WEIGHT: Yes
- Time schedule for examinations: daily monitoring

FOOD CONSUMPTION:
- Food consumption was determined daily for each individual animal. Mean daily diet consumption was calculated as g food/kg body weight/day: Data are given

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: Yes
- Time schedule for examinations: water uptake was determined for weekly periods for each individual animal

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: 3 days before first dosage and at the end of the test before the blood test
- Dose groups that were examined: all rats of the control group and all rats of the maximum dose group

HAEMATOLOGY: Yes
- Time schedule for collection of blood: week 5 and week 14 of test for all animals
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: (all)
- Parameters checked see table No. 1 below. Also differential blood count data are reported.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: week 5 and week 14 of test for all animals
- Animals fasted: No data
- How many animals: (all)
- Parameters checked in table 1 below.

URINALYSIS: Yes
- Time schedule for collection of urine: week 5 and week 13 of test for all animals
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters checked in table [No.113191/90] Urine volume was measured using calibrated test tubes, and urine colour and turbidity were visually assessed. Urinalysis parameters were urine pH, protein, glucose, ketone, bilirubin, blood and urobilinogen

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, A complete necropsy was conducted on all animals.

HISTOPATHOLOGY: Yes, was carried out at Institute for Toxicology Pharma, Bayer AG, Registration Number 2953.
see table 2.

Statistics:

Data are given as arithmetic mean with standard deviation; Organ weights are given as 95 and 99 Percentile values. Control group data were compared using significance tests (U-Test). Differences exceeding the significance levels 5% and 1% are labelled in the result tables.
It is noted that the total error probability increases with number of comparisons carried out. To compensate overestimation of significance values the biological and toxicological relevance was considered in the evaluation. All statistical tests were performed using appropriate computing devices or programs.

Results and discussion

Results of examinations

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):

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

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:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

no tumour found

Details on results:

CLINICAL SIGNS AND MORTALITY: During the study two male (dose group 1000 mg/kg, due to dosing error or not considered treatment-related) and three female animals of various groups died. The substance treatment was excluded as reason for the fatalities.

BODY WEIGHT, WEIGHT GAIN AND FOOD CONSUMPTION: Female rats in both low dose groups show partly significant higher body weights than the control groups. This was not considered toxiclologically relevant. Slightly higher water consumption in all dose groups compare to control groups was observed. No clear treatment-related effects were reported on the other end points.

HAEMATOLOGY: The high dose groups (both m/f) showed significantly lower hemoglobin concentration after 13 weeks.

CLINICAL CHEMISTRY: a reduction of bilirubin values of all dose groups and calcium was higher in female dose groups and chloride was lower in all female dose groups. Chloride findings were not considered toxicologically relevant.

ORGAN WEIGHTS: Female rats in all dose groups showed significantly increased liver weights of up to 62% compare to the control group (see below).

GROSS PATHOLOGY: One female in the 100 mg/kg group had a glassy solid lump in the lung parenchyma. In the 330 mg/kg group 8 males and 6 females exhibited glassy and/or hard lumps in the lung parenchyma (2 - 15mm diameter). In the 1000mg/kg group six males and 6 females had lumps of 3 - 10 mm diameter in the lung parenchyma.
For one male in the highest dose group testes were observed to be smaller; one female of the high dose group exhibited an increased glassy right lymph node (3 mm).

HISTOPATHOLOGY: The glassy lumps which were observed in pathology were confirmed in the lung examinations.
Results on lungs, lymph nodes and liver are given in the detailed summary below.
Other organs were examined but indicated no treatment related damage.

Effect levels

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: Based on toxicological effects relevant to humans.

Target system / organ toxicity

Critical effects observed:

no

Any other information on results incl. tables

Summary report on Histopathology (Dr. Eike Hartmann, pathologist, Bayer, July 1, 2005)

Ten male and female Wistar rats received undiluted Cyclomethicone D5 at doses of 0 (tap water) — 100 — 330 — 1000 mg/kg once daily for 13 weeks by gavage. In this study H&E stained paraffin sections of the lungs, trachea, liver, kidneys, heart, spleen, stomach, intestine, mesenteric lymph node, and gross lesions were examined from rats of all dose groups. On lungs and mesenteric lymph nodes also special staining methods like the Periodic —Acid —Schiff reaction, an Elastica van Gieson, and/or an Oil red 0 stains were applied.

Lungs:

At necropsy, lung nodules (hard, glassy/gray) of varying size were reported predominantly located in the apical or cranial parts of the diaphragmatic lobes close to the bronchi. The combined incidence for either sex was 0 / 1 / 14 / 12 out of 20 rats per group. Microscopically, granulomatous pneumonia characterized by an accumulation of vacuolated macrophages, solid granulomas, giant cells, necrosis, hemorrhage, granulocytic infiltration, suppurative foci, and /or type II pneumocyte proliferation was observed in males in the incidence 0 / 0 / 9 / 8 and in females in the incidence 0 / 1 / 7/ 6. An accompanying goblet cell hypertrophy of larger bronchi occurred in males at 330 mg/kg and in females at 100 mg/kg and above. Among affected mid and high dose rats similar severity scores were given for both lung findings ranging from grade 1 to grade 5. The lesions were restricted to lung lobes involved macroscopically, other parts of the lungs demonstrated no relevant histopathologic alterations.

Localization, morphologic pattern and resorptive character of the pneumonic changes are presumed to be the result of the test compound reaching the lungs by the airways unintentionally (e.g. by the methods of administration) and subsequent aspiration. They are not considered as systemic alterations caused by the test material and reaching the lungs by the bloodstream.

Mesenteric Lymph nodes:

Histiocytosis was found in almost all males and females at 100 mg/kg and above. The sinus of affected lymph nodes contained foci of macrophages loaded with foamy material. These changes were not associated with leukocytic infiltration or necrosis. Frequency and severity score were not dose dependent in males. In females, the most

severe lesions were observed at 1000 mg/kg. Similar grades were given in females of the low and mid dose group. Histiocytosis of the mesenteric lymph node can be explained by absorption of test compound or metabolites by the intestinal mucosa and its transfer to the local lymph node where it is phagocytosed by sinusoidal macrophages / histiocytes. These processes did not provoke any inflammatory reactions.

Liver:

Several animals receiving 1000 mg/kg had hepatocytic cytoplasmic changes which were interpreted as morphologic sign of an adaption to increased metabolic activity. These liver cell changes are not considered as adverse effects.

Applicant's summary and conclusion

Conclusions:

A well reported 90-day oral study, conducted in the main according to the current guideline and in accordance with GLP is reported. In the study damage to the lungs and lymph nodes was seen at all dose levels. However, he effects on the lungs were considered by the pathologist to be due to aspiration of the test substance, and the effects on the lymph nodes are physical rather than due to systemic toxicity. For the purposes of human hazard assessment, the NOAEL is therefore considered to be greater than or equal to the highest dose tested, 1000 mg/kg bw/day.