Reaction mass of decamethyltetrasiloxane; dodecamethylpentasiloxane; hexamethyldisiloxane; octamethyltrisiloxane

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3465 (90-Day Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Octamethyltrisiloxane

EC Number:

203-497-4

EC Name:

Octamethyltrisiloxane

Cas Number:

107-51-7

Molecular formula:

C8H24O2Si3

IUPAC Name:

Octamethyltrisiloxane

Test animals

Species:

rat

Strain:

other: Hsd:Sprague DawleySD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: not stated
- Age at study initiation: approximately 9 weeks
- Weight at study initiation: Males 263.6 - 308.7g (+/-8%) Females 181.2 - 219.8g (+/-10%)
- Fasting period before study: No
- Housing: Makrolon type-4 cages, 5/sex/cage
- Diet: Kliba Nafag 3433 ad libitum
- Water: local supply ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-25
- Humidity (%): 30-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: To: 27 January to 26 May 2009

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: not applicable

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel sealed chambers
- Method of holding animals in test chamber: stainless steel wire cage units
- Source and rate of air: compressed air at 40L/min
- System of generating vapours: compressed air supplied into glass flasks containing Octamethyltrisiloxane through a metal nebulization tube. Flasks maintained at 60-80 degrees C.
- Temperature, humidity, pressure in air chamber: oxygen concentration maintained above 19% whenever possible. Temperature 19-25 degrees C, humidity 30-70%
- Air flow rate: 380L/min
- Method of particle size determination: n/a


TEST ATMOSPHERE
- Brief description of analytical method used: on-line GC
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Nominal - once daily weighing test item reservoir before and after each exposure
Chemical - measured 4 times per hour by on-line GC according to following conditions:
Column: DB-1 (30m x 0.53mm x 1.5um)
Injector: 225 degrees C
Oven: 100 degrees C for 0.1 min, then 50 degrees C/min, to 150 degrees C for 0 min
Detector: FID, 300 degrees C

Duration of treatment / exposure:

90 days followed by 28 day recovery period for subgroup of Control and high dose animals

Frequency of treatment:

6 hours daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

95 ppm (nominal)

Doses / concentrations 2

Dose / conc.:

400 ppm (nominal)

Doses / concentrations 3

Dose / conc.:

3 200 ppm (nominal)

No. of animals per sex per dose:

Control and high dose - 20
Low and intermediate dose - 10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: not stated

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily during treatment, weekly during recovery

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

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

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: pretreatment and day 86
- Dose groups that were examined: All

HAEMATOLOGY: Yes
- Time schedule for collection of blood: day 92 or 93, recovery period day 29
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes
- How many animals: all
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: day 92 or 93, recovery period day 29
- Animals fasted: Yes
- How many animals: all
- Parameters checked in table No. 2 were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: day 92 or 93, recovery day 29
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked in table No.3 were examined.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

ORGAN WEIGHT: Yes (see table 4)
GROSS PATHOLOGY: Yes (see table 4)
HISTOPATHOLOGY: Yes (see table 4)

Other examinations:

Immunohistochemistry of kidney sections for alpha-2u globulin staining

Statistics:

The Dunnett-test (many to one t-test) based on a pooled variance estimate was applied if the variables could be assumed to follow a normal distribution for the comparison of the treated groups and the control groups for each sex.
The Steel-test (many-one rank test) was applied instead of the Dunnett-test when the data could not be assumed to follow a normal distribution.
Fisher's exact-test was applied to the ophthalmoscopic and macroscopic findings.
Statistical evaluation of microscopic findings was performed using the one-sided exact Fisher test

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):

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

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:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY: all animals survived and no treatment-related clinical signs recorded.

BODY WEIGHT AND WEIGHT GAIN: no effect of treatment.

FOOD CONSUMPTION: no effect of treatment.

OPHTHALMOSCOPIC EXAMINATION: no treatment-related findings

HAEMATOLOGY: no effect of treatment

CLINICAL CHEMISTRY: A slight increase in cholesterol levels were observed in males (+26.5%) and females (+10.1%) at 3200 ppm and females at 400 ppm (+8.0%) compared to controls at the end of treatment. This was not apparent at the end of the recovery period.

Marginally increased sodium (between +3.2 and +3.8%) and chloride (between +1.2 and +1.8%) values were seen in females at all concentrations. Additionally, sodium was also increased in males at 3200 ppm (+ 1.6%) and marginally increased calcium values were noted in males (+3.6%) and females (+2.4%) at 3200 ppm. This was not apparent at the end of recovery.

Increased total protein and globulin values, which resulted in a decreased albumin to globulin ratio, were observed for males at 3200 ppm (+6.4% for protein and + 13.8% for globulin) and females at 400 (+4.4% for protein and +10.1% for globulin) or 3200 ppm (+5.4% for protein and +14.7% for globulin).This was not apparent at the end of recovery.

URINALYSIS: no effect of treatment.

ORGAN WEIGHTS: Increased absolute and relative liver weights were recorded at the end of the treatment period for males at 400 (+11.1% absolute/+12.1% body weight ratio) or 3200 ppm (+22.1% absolute/+24.6% body weight ratio) and for females at 3200 ppm (+26.5% absolute/+26.6% body weight ratio). The differences to Controls was less marked but still apparent at the end of the recovery period in males but not females.

Increased kidney weights were observed for males exposed to 3200 ppm (+6.7% absolute/+8.5% body weight ratio). This was not apparent at the end of the recovery period.

GROSS PATHOLOGY: no effect of treatment.

HISTOPATHOLOGY: NON-NEOPLASTIC
Centrilobular hepatocellular hypertrophy was observed in the liver of four males at 400 ppm (minimal in severity) and nine males and nine females at 3200 ppm (minimal to slight in severity).

Reddish-brown pigmented crystalline material, consistent in appearance with brown pigment at a minimal to moderate degree was noted in all ten males at 3200 ppm. The material was characterized by accumulations/concretions of red-brown pigment in small and medium bile ducts and macrophages in the portal triads. Under polarized light these concretions were birefringent appearing bright red with a dark Maltese cross-like patterns in many globules. Periportal chronic inflammation was noted in all ten males and one female at 3200 ppm, and was also noted in one control male and female each, one female at 95 ppm, and one male and female each at 400 ppm. Bile duct proliferation was noted in one female each at 95 and 400 ppm, and nine males at 3200 ppm.

Brown pigment crystals were noted in seven males previously exposed to 3200 ppm at the end of the recovery period with a lower mean severity than at the end of the treatment period. Periportal chronic inflammation was noted at the end of recovery in four control males and in nine males and two females previously exposed to 3200 ppm, and bile duct proliferation was noted in eight males and two females of the same group.

Minimal to slight proximal tubular hypertrophy was noted in the kidneys of nine males and ten females at 3200 ppm. Minimal to slight hyaline droplets were observed in one male at 95 ppm, three males at 400 ppm and all males at 3200 ppm. This was not observed at the end of the recovery period.

IMMUNOHISTOCHEMISTRY:
Immunohistochemical staining of kidney sections for alpha-2u-globulin revealed a dose-related increase in staining in male rats at all doses terminated at the end of the dosing period. This was observed primarily as an increase in mean staining score of the globular staining patterns. There was evidence of incomplete recovery in alpha-2u-globulin accumulation in the Recovery Group males at 3200 ppm. There was no evidence ofalpha-2u-globulin accumulation in the kidneys of female rats.

Effect levels

Dose descriptor:

NOAEL

Effect level:

400 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Based on accumulation of brown hepatic pigment and associated periportal chronic inflammation and bile duct proliferation noted at 3200 ppm

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 1 - Exposure conditions

Group	Temperature (^oC)	Relative Humidity (%)	Oxygen concentration (%)
1	23.1±0.2 (n=91)	49.2± 1.5 (n=91)	20.3± 0.0 (n=91)
2	22.8± 0.2 (n=91)	37.0± 1.3 (n=91)	20.6± 0.0 (n=91)
3	23.8± 0.1 (n=91)	36.3± 1.0 (n=91)	20.3± 0.0 (n=91)
4	22.9± 0.4 (n=91)	39.9± 1.8 (n=91)	19.4± 0.3 (n=91)

Table 2 - Test Atmosphere Concentrations

Group	Achieved Test Atmosphere Concentration (ppm)	Target Test Atmosphere Concentration (ppm)	Test Atmosphere Concentration Relative to Target (%)
2	95.0±0.2 (n=91, CV=0.2%)	95	100.0%± 0.2% (n=91)
3	400±1 (n=91, CV=0.1%)	400	100.1%±0.1% (n=91)
4	3201±3 (n=91, CV=0.1%)	3200	100.0%±0.1% (n=91)

Applicant's summary and conclusion

Conclusions:

Whole body exposure of SD rats to Octamethyltrisiloxane at 95, 400 or 3200 ppm for 90 days resulted in liver and kidney changes. In the liver hepatocyte hypertrophy and accumulation of brown pigment crystals in the bile ducts with associated periportal inflammation and bile duct proliferation were noted. In the kidneys tubular hypertrophy was noted and associated with minor changes in salt balance and plasma protein levels. Hyaline droplets noted represented alpha-2u-globulin accumulation. Based on the pigment accumulation noted in the liver at 3200 ppm the No-Observed-Adverse-Effect-Level was considered to be 400 ppm.