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Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
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 guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.3465 (90-Day Inhalation Toxicity)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent

Test animals

Species:
rat
Strain:
other: Hsd:Sprague DawleySD
Sex:
male/female
Details on test animals 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 / concentrationsopen allclose all
Dose / conc.:
95 ppm (nominal)
Dose / conc.:
400 ppm (nominal)
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: pre-treatment 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).

Brown pigmented crystalline material at a minimal to moderate degree was noted in all ten males at 3200 ppm. The material was characterized by accumulations/concretions of 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 ppml. There was no evidence of alpha-2u-globulin accumulation in the kidneys of female rats.

Effect levels

Dose descriptor:
NOAEC
Effect level:
400 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Based on accumulation of brown 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.