Octamethyltrisiloxane

Endpoint summary

Description of key information

Whole body exposure of SD rats to octamethyltrisiloxane at 95, 400 or 3200 ppm for 90 days resulted in liver and kidney changes (Harlan, 2011). In the liver hepatocyte hypertrophy and accumulation of brown pigment 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 secondary effects of pigment accumulation noted in the liver at 3200 ppm the NOAEC was considered to be 400 ppm. There were no local effects. In an OECD Guideline 422 study (Dow Corning Corporation, 2008), performed to GLP, the potential inhalation toxicity of octamethyltrisiloxane was evaluated in Sprague-Dawley rats.

Animals were exposed to target concentrations of 0, 800, 1600 or 3200 ppm for 6 hours/day for 29 days in the toxicity test and up to 42 days in the reproductive/developmental screening test. After 29 days, there were no overt toxic effects. Increased liver weights were observed in female rats exposed to 806 ppm and above and in male rats exposed to 3146 ppm. Histopathological examination revealed effects that were attributed to octamethyltrisiloxane exposure in the liver, kidney and thyroid gland. Effects (centrilobular hypertrophy) in the liver were evident in females at all dose levels and in males in the highest exposure group. In males, hepatic brown pigment accumulation was observed in the mid- and high exposure groups and protein droplet nephropathy at 806 ppm and above. Thyroid gland follicular hypertrophy was evident in both sexes at 3146 ppm and this was considered to be secondary to the hepatic centrilobular hypertrophy. Actual exposure concentrations were 806, 1623 and 3146 ppm. The NOAEC for general systemic toxicity was <806 ppm octamethyltrisiloxane based on protein droplet nephropathy and hepatic brown pigment accumulation.

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:

17 December 2009 - 20 July 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories, B.V., Netherlands
- Age at study initiation: approximately 7 weeks
- Weight at study initiation: Males 196-220g, females 152-183g
- Fasting period before study: no
- Housing: In groups of 5, in Makrolon type-4 cages.
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3
- Humidity (%): 30-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: corn oil (dried and deacidified)

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The dose formulations were prepared daily. The test material was weighed into a glass beaker, and the vehicle was added to give the appropriate final concentration of the test item in the dose formulation. Each dose level was prepared individually. The mixtures were stirred using a magnetic stirrer and used at room temperature. The homogeneity of the rest item in the vehicle was maintained during daily administration period using a magnetic stirrer.

VEHICLE
- Lot/batch no. (if required): 049103168

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analysis was performed using a GC method. After experimental start and during week 3, duplicate samples of the control group and three samples (top, middle and bottom) of about 2 g of each concentration were taken prior to dosing for analysis of homogeneity and concentration. Duplicate samples of about 2 g of each concentration were taken to confirm stability (4 hour; due to organizational reasons the samples were transferred to the analytical department ca. 4.5 hours after preparation). The samples were delivered to the analytical department and stored at -20C +/-5 until analysis.

Duration of treatment / exposure:

Treatment: 28 days
Recovery: 14 days

Frequency of treatment:

Daily.

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

250 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:

The groups comprised of 5 animals per sex which were terminated after 28 days of treatment. Additional 5 rats per sex and group were used at 0 and 1000 mg/kg. These animals were treated for 28 days and then allowed a 14 day treatment-free recovery period after which they were terminated.

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were selected based on a previous range finding toxicity study (C53644)

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily on days 1-3, once daily on days 4-28 and once daily during days 1-14 of the recovery period

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly during acclimatization, treatment and recovery periods and before necropsy.


HAEMATOLOGY: Yes
Complete blood cell count including: erythrocyte count, haemoglobin, haematocrit, mean corpuscular volume, red cell volume distribution width, mean corpuscular haemoglobin and haemoglobin concentration, haemoglobin concentration distribution width, reticulocyte count, reticulocyte maturity index, total leukocyte count, differential leukocyte count, neutrophils, eosinophils, basophils, lymphocytes, monocytes, large unstained cells, platelet count, methaemoglobin, Heinz bodies, prothrombin/thromboplastin time and activated partial thromboplastin time.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: After 4 weeks, and 6 weeks (recovery)
- Animals fasted: Yes
- How many animals: all animals
- Parameters examined. Glucose, urea, creatinine, total bilirubin, total cholesterol, triglycerides, phospholipids, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, bile acids, gamma-glutamyl-transferase, creatinine kinase, sodium, potassium, chloride, calcium, phosphorus (inorganic), total protein, albumin, globulin and albumin/globulin ratio

URINALYSIS: Yes
- Time schedule for collection of urine: After 4 weeks, and 6 weeks (recovery)
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters examined. Urine volume, specific gravity, colour, appearance, pH, nitrite, protein, glucose, ketones, urobilinogen, erythrocytes, leukocytes

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Week 4
- Dose groups that were examined: all
- Battery of functions tested: sensory activity / grip strength / motor activity

OTHER: Weekly behavioural observations were carried out for the animals in their home cages, outside their home cages in a standard arena and in the hand. These observations were performed once before initial dosing and once weekly (weeks 1 to 3) during treatment period. Vaginal smears were taken over four days from all females in Week 4, and the stage of estrus was evaluated.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 1)
HISTOPATHOLOGY: Yes (see table 1)

Other examinations:

Organ weights were recorded for adrenal glands, brain (including section of medulla/pons, cerebral and cerebella cortex), epididymides, heart including auricles, kidneys, liver, ovaries, pituitary gland, seminal vesicles and prostate gland (including coagulating glands), spleen, testes, thymus, thyroid, uterus. Relative organ weights were calculated on the basis of body weight and brain weight. Terminal body weight was recorded immediately prior to necropsy and the organ to terminal body weight ratios and organ to brain weight ratios were determined.

Statistics:

The following statistical methods were used to analyse body weight, grip strength, locomotor activity, clinical laboratory data, organ weights and ratios and macroscopic findings.
• 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.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

no effects observed

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

Details on results:

CLINICAL SIGNS AND MORTALITY
All animals survived until scheduled necropsy.
No test-item related findings were noted and no abnormalities were recorded at any dose level.
In three male animals at 1000 mg/kg/day clinical signs were noted during the treatment phase: animal No. 28 had hunched posture and slight visible body weight loss from day 20 onwards as well as slightly ruffled fur at day 14 and again from day 22 to the end of observation time were observed. Slight dyspnea was recorded at days 13 and 14 and again from day 19 to 25. Slight salivation was observed from day 19 to 22. In animal 35, slight to moderate hair loss was observed in the right axillary region from day 10 to the end of observation. These findings are considered to be typical background findings.

BODY WEIGHT AND WEIGHT GAIN
A test item-related reduction in the body weight was recorded in males at 1000 mg/kg/day when compared to the control animals.
The mean body weight in these males was significantly lower on day 8 (-9%), day 15 (-11%), day 22 (-14%) and day 28 (-11%) of the treatment phase (all p<0.01) as well as day 1 (-15%), day 8 (-11%; both p<0.01) and day 14 (-9%; p<0.05) of the recovery period compared to the control group. In addition, the mean body weight gain was significantly reduced in the same animals on days 8, 15, 22 and 28 of treatment (p<0.01), but was increased compared to the control animals during recovery (day 8; p<0.05). This was considered to be a compensatory reaction.
Increased mean body weight gain compared to control was noted during recovery in females at 1000 mg/kg/day (day 14; p<0.01).

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
No test item-related difference in the mean daily food consumption was noted at any dose level. Changes in mean food consumption were noted in male and female animals at 1000 mg/kg/day. The food consumption was increased in these animals during treatment days 22 - 28 and during
the recovery period when compared to the control groups.


HAEMATOLOGY
After the four-week treatment phase, test item related and statistically significant changes were noted in males at 1000 mg/kg/day. These included increased number of red blood cells as well as decreased mean corpuscular volume and mean cell hemoglobin (with normal mean cell
hemoglobin concentration). The decrease in MCV and MCH persisted at the end of the recovery period. Although the red blood cell count was not significantly different from control at the end of the recovery, it was still much higher at this time point compared to the control animals and even to
the data at the end of the treatment phase. Therefore, it is considered to be relevant although not statistically significant. However, the lack of statistical significance was due to a single outlier and the smaller sample size. Mean corpuscular hemoglobin level was below the control levels in the female animals at 1000 mg/kg/day. The reticulocyte maturity index showed a higher fraction of mature (low fluorescence reticulocytes) and reduced fraction of immature (middle fluorescence and high fluorescence reticulocytes) cells only in males. In the differential white blood cell count, the relative and
absolute number of eosinophils was below the control level. Significant changes of these parameters were no longer evident after the 2-week recovery period. Other significant changes (see below) noted in the hematology parameters in male and female animals are within the historical control data for animals of this strain, sex and age, based on outliers or due to statistical method and, therefore, considered not to be test item-related.
Within the normal range of variability were reduced relative lymphocyte count (p<0.05), increased number of neutrophils (p<0.05) and platelets (p<0.01), increased hemoglobin distribution width (p<0.01) in male animals at 1000 mg/kg/day as well as decreased hemoglobin and hematocrit (both p<0.05) in males at 250 mg/kg/day. In females, red blood cells (p<0.05) and hematocrit (p<0.01) were reduced at 5 mg/kg/day and reduced red cell distribution width 1000 mg/kg/day, but also within the range of historical data. The mean relative methemoglobin level was the same in males at 250 mg/kg/day and 1000 mg/kg/day, but is mentioned significantly different the latter group due to the rounding difference during calculation. This parameter was also within the historical data range. The mean thromboplastin time was significantly lower in males at 250 mg/kg/day and at 1000 mg/kg/day and in females at 25 mg/kg/day and 1000 mg/kg/day (but not at 250 mg/kg/day) when compared with the control animals. As the control values exceed the range of historical data, the statistical differences were considered to be artefacts.

CLINICAL CHEMISTRY
After four weeks of treatment, several test item-related effects were noted in the clinical biochemistry parameters.
Test item-related changes in liver-associated enzymes noted in males at 1000 mg/kg/day included significantly increased mean activities of aspartate aminotransferase (p<0.05), alanine aminotransferase (p<0.05) and gamma glutamyl transferase (p<0.01). Females of the same dose
level were unaffected. Total cholesterol and phospholipid levels were significantly elevated (p<0.01) in males at 250 mg/kg/day and in both sexes at 1000 mg/kg/day. Triglyceride level was increased (p<0.01) only in females at 1000 mg/kg/day and this difference persisted until the end of the recovery period (p<0.05).
Mean total bilirubin level was increased (p<0.01) in males at 250 mg/kg/day and 1000 mg/kg/day. In females, a significant increase was noted only at 250 mg/kg/day (p<0.01). As no effect was noted in females at 1000 mg/kg/day, this was considered to be not test item related.
An increase in glucose level was noted in males and females at 5 mg/kg/day, males at 25 mg/kg/day and females at 250 and 1000 mg/kg/day when compared to the controls but was within the range of historical data for animals of this strain, sex and age and considered to be not
related to treatment. Significant changes in protein parameters noted in males and females at 250 mg/kg/day and/or 1000 mg/kg/day included increased total protein and globulin, and decreased albumin and albumin/globulin ratio. However, with exception of higher globulin and lower albumin/globulin ratio in males at 1000 mg/kg/day, all changes were within the historical data range and considered not to be test item-related.
Significantly elevated sodium and chloride serum levels were evident in males at 1000 mg/kg/day (p<0.01) after four weeks of treatment. An increase in serum potassium was noted in males at 25 mg/kg/day (p<0.05), 250 mg/kg/day (p<0.05) and 1000 mg/kg/day (p<0.01). In females at 1000 mg/kg/day, mean serum potassium level was also significantly increased after four weeks of treatment but did not persist after the recovery period. Phosphorous level was lower than control level in males at 250 mg/kg/day (p<0.05) as well as males and females at 1000 mg/kg/day (p<0.05 and p<0.01, resp.). However, the values in females were still within the historical data.
Further significant changes in females included increased sodium and chloride at 25 mg/kg/day and decreased calcium at 5 mg/kg/day, all within the range of the historical data and considered not to be test item-related. After two weeks of recovery, several significant differences were noted: significantly higher potassium persisted in males (p<0.05) when compared with the control values. Although the triglyceride level remained significantly higher in females (p<0.05) when compared with the control value, it was markedly lower than at the end of the treatment period and most likely
caused by a low control value. Decreased bile acid (p<0.01), decreased mean activity of alanine aminotransferase (p<0.01) and decreased mean activity of alkaline phosphatase (p<0.05) in males as well as decreased albumin levels in females (p<0.05) were noted. These differences were either within the range of the historical control data, or considered to be of no toxicological relevance.


URINALYSIS
Mean urine volume was significantly increased in males at 1000 mg/kg/day (p<0.01) and the relative density was decreased in the same animals after four weeks of treatment when compared to the control group. However, these values are within the range of historical data and do not
appear in females of the same dose group. Nevertheless, this effect was considered to be toxicologically relevant (but not adverse) due to the combination with changes in serum electrolyte levels (see Clinical Biochemistry) and microscopic changes. The significant decrease in protein noted in males at 1000 mg/kg/day (p<0.05) was in the range of historical data. The ketones were also significantly decreased at 1000 mg/kg/day (p<0.01) with control levels above the historical data range. The urine pH in females at 1000 mg/kg/day was significantly different from control. Although the pH values appear identical in females at 25 and 1000 mg/kg/day, the statistical significance resulted from a rounding difference and different numbers of animals (n = 5 in group 2 versus n = 10 in group 4). In all cases, the exact raw data values were used for statistical analysis, but are rounded for printing. Therefore, the statistical significance of this parameter was considered to be an artefact.

NEUROBEHAVIOUR
No test-item related differences compared to the control groups were recorded in the mean forelimb or hindlimb grip strength values of male and female animals at any dose levels. The mean grip strength was significantly reduced (p<0.05) in females at 5 mg/kg/day. As there
were no significant differences in the higher dose groups compared to the control, this finding is considered to be incidental.

No test item-related effects on the locomotor activity were observed.
When compared to the control group, significantly reduced locomotor activity was recorded in males at 1000 mg/kg/day at 20 - 30 minutes (p<0.05), 30 - 40 minutes (p<0.01) and 40 - 50 minutes (p<0.05). In females of this dose level, significantly increased locomotor activity was
noted at 0-10 minutes (p<0.05) and 40-50 minutes (p<0.05). These differences are considered to be within the normal range of variability.

ORGAN WEIGHTS
Test item-related increases in mean absolute and relative liver weights were recorded in male animals at 25 mg/kg/day, 250 mg/kg/day and/or 1000 mg/kg/day and in females at 250 mg/kg/day and 1000 mg/kg/day after four weeks of treatment. Mean absolute liver weights were significantly elevated in males at 250 and 1000 mg/kg/day (+56% for both groups) and in females at 1000 mg/kg/day (+37%; all p<0.01). The mean liver/body weight ratio was significantly increased in males at 25 mg/kg/day (+12%; p<0.05), 250 mg/kg/day (+52%; p<0.01) and 1000 mg/kg/day (+78%; p<0.01) and in females at 250 mg/kg/day (+12%; p<0.05) and 1000 mg/kg/day (+45%; p<0.01). Furthermore, the mean liver/brain weight ratio was significantly higher in males at 250 mg/kg/day (+57%; p<0.01) and 1000 mg/kg/day (+62%; p<0.01), and in females at 1000 mg/kg/day (44%; p<0.01).
Reduced mean absolute weights of the heart (-16%) and pituitary gland (-18%) were noted in males at 1000 mg/kg/day (p<0.05). Elevated mean kidney/body weight ratio (p<0.01) was recorded in male animals at 1000 mg/kg/day. Significantly reduced mean heart/brain weight ratio (p<0.05) was noted in males at 1000 mg/kg/day. Significantly decreased mean absolute brain weights were recorded in female animals at
250 mg/kg/day (-4%; p<0.05) and at 1000 mg/kg/day (-4%; p<0.01). After two weeks of recovery, significantly lower mean absolute brain weights (-5%; p<0.01), lower combined absolute mean weights of the seminal vesicles/prostate glands (-15%; p<0.01) and lower weight of epididymides (-8%; p<0.05) were noted in males at 1000 mg/kg/day. Elevated mean testes/body weight ratios (p<0.05) and mean testes/brain weight ratios were
recorded (p<0.05) in these animals compared to controls and mean seminal vesicles and prostate/brain weight ratio were decreased (p<0.05). Elevated mean liver/body weight and liver/brain weight ratios (+23%; p<0.01 and +15%; p<0.05, respectively) were recorded in males at 1000 mg/kg/day. In the corresponding females, a significantly higher mean liver/body weight ratio (+12%; p<0.01) was also noted.

GROSS PATHOLOGY
Test item-related enlargement and dark or black brown discoloration of the liver were noted in males at 250 mg/kg/day (100% of treated animals, both p<0.01) and at 1000 mg/kg/day (80 - 100%, p<0.01 or p<0.05, respectively) and in females at 1000 mg/kg/day (40%) at necropsy
after four weeks of treatment. Additional findings noted in individual males or females were considered to be not related to treatment: dark red foci in the mucosa of the stomach (one control male), unilateral renal pelvis dilation (one male at 5 mg/kg), red foci or reddish discoloration of the thymus (one control male and one control female, one male at 250 mg/kg/day, one male at 1000 mg/kg/day, one female at 5 mg/kg/day), dark red nodules in epididymal adipose tissue (one male at 250 mg/kg/day), dilation of the uterus (one female at 25 mg/kg/day and one female at 250 mg/kg/day).
After two weeks of recovery, black brown discoloration of the liver was still present in all males at 1000 mg/kg/day (p<0.01), and enlarged / discoloured lymph nodes were recorded in one of these males. No findings were noted in the females at necropsy after the 2-week recovery period.

HISTOPATHOLOGY: NON-NEOPLASTIC
LIVER:
Hepatic brown l pigment accumulation in the intra-hepatic bile ducts was recorded at minimal to moderate severity in animals of both sexes at 1000 mg/kg/day and in males at 250 mg/kg/day after the treatment period. Brown pigment accumulation was recorded in Kupffer cell as well as in
hepatocytes in males at 250 mg/kg/day and 1000 mg/kg/day at the end of the four week treatment period. Under polarised light some pigment accumulations show birefringence, but this finding was not consistent in size or between animals. Periportal chronic inflammation and bile duct proliferation at minimal to slight severity was recorded in both sexes at 1000 mg/kg/day and in males at 250 mg/kg/day at the end of the treatment period. Hepatocellular hypertrophy (centrilobular) was recorded at minimal severity in both sexes at 1000 mg/kg/day and in males at 250 mg/kg/day after four weeks of treatment. With the exception of hepatocellular hypertrophy in both sexes and bile duct proliferation in females, these findings persisted in animals at 1000 mg/kg/day after the 14 day recovery period.

KIDNEY:
Hyaline droplets at minimal to slight severity were recorded in males at 25 mg/kg/day, 250 mg/kg/day and 1000 mg/kg/day at the end of the treatment period. The hyaline droplets were not evident in animals after 14 day recovery period. Immunohistochemistry for a-2u globulin (globular staining) showed a similar dose effect as seen with hyaline droplets indicating that the hyaline droplets are not relevant for humans.

THYROID GLANDS:
Follicular cell hypertrophy at minimal severity was recorded in two males and one female at 1000 mg/kg/day at the end of 28-day treatment period.
The follicular cell hypertrophy was not evident in animals after the 14-day recovery period.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)

HISTORICAL CONTROL DATA (if applicable)

OTHER FINDINGS

Dose descriptor:

NOAEL

Effect level:

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

Sex:

male

Basis for effect level:

other: Based on the findings in the liver (brown pigment accumulation accompanied by periportal chronic inflammation and bile duct proliferation), and the absence of clear reversibility.

Dose descriptor:

NOAEL

Effect level:

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

Sex:

female

Basis for effect level:

other: lack of reversibility of macroscopic liver findings.

Critical effects observed:

not specified

Conclusions:

The NOAEL of 25 mg/kg/day in the males and 250 mg/kg/day in the females was determined in a 28 day oral gavage study in rat, conducted according to current OECD guideline and in compliance with GLP.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

25 mg/kg bw/day

Study duration:

subacute

Species:

rat

System:

hepatobiliary

Organ:

bile duct

liver

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

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

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3465 (90-Day Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

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

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

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

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

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 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 polarised light some pigment accumulations show birefringence, but this finding was not consistent in size or between animals. 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.

Hepatic brown pigment was 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 of alpha-2u-globulin accumulation in the kidneys of female rats.

Dose descriptor:

NOAEL

Effect level:

400 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

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

Critical effects observed:

not specified

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)

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 pigments 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 NOAEC was considered to be 400 ppm.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

3 870 mg/m³

Study duration:

subchronic

Species:

rat

System:

other: Hepatobiliary and urinary

Organ:

bile duct

kidney

liver

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

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

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3465 (90-Day Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

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

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

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

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

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 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 polarised light some pigment accumulations show birefringence, but this finding was not consistent in size or between animals. 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.

Hepatic brown pigment was 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 of alpha-2u-globulin accumulation in the kidneys of female rats.

Dose descriptor:

NOAEL

Effect level:

400 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

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

Critical effects observed:

not specified

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)

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 pigments 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 NOAEC was considered to be 400 ppm.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

30 690 mg/m³

Study duration:

subchronic

Species:

rat

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

In an OECD Guideline 407 study (Harlan 2010), performed to GLP, the potential oral toxicity of octamethyltrisiloxane was evaluated in Sprague Dawley rats. Animals were exposed to target concentrations of 0, 5, 25, 250 and 1000 mg/kg bw/day by oral gavage for 28 days. Based on the findings in the liver (brown pigment accumulation accompanied by periportal chronic inflammation and bile duct proliferation), it was concluded that males were more affected than the females by treatment with octamethyltrisiloxane (L3). Under polarised light some pigment accumulations show birefringence, but this finding was not consistent in size or between animals. Pigment accumulation was considered to be an adverse finding due to observed secondary periportal chronic inflammation and bile duct proliferation. In the absence of clear reversibility of microscopic liver findings, the NOAEL of the test item was considered to be 25 mg/kg/day in the males and 250 mg/kg/day in the females.

Other effects on the liver (liver enlargement, altered clinical chemistry and liver cell hypertrophy) are not necessarily directly related to the hepatic brown pigment findings. The current interpretation, which is consistent with findings with other siloxanes, is that the liver enlargement is an adaptive effect that should not be considered as adverse. There is currently no evidence, from studies with L3 or other substances, that an increase in liver weight has the potential to impact on other organs.

There are two reliable inhalation studies available for octamethyltrisiloxane. The key study is a 90-day whole body inhalation study which gave a NOAEC of 400 ppm (3870 mg/m³) based on pigment accumulation in the liver. The supporting study is an inhalation OECD 422 study which gave a NOAEC of <806 ppm based on protein droplet nephropathy and hepatic brown pigment accumulation, which supports the findings in the key study. There were no local effects on the respiratory tract therefore the local NOAEC was at least 30,960 mg/m³ (the highest dose tested).

Justification for classification or non-classification

Based on the results of the available repeated dose toxicity studies octamethyltrisiloxane is not classified for adverse effects following repeated exposures according to Regulation (EC) No 1272/2008.