Registration Dossier

Diss Factsheets

Toxicological information

Repeated dose toxicity: inhalation

Currently viewing:

Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented study report equivalent or similar to OECD guideline 413.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Cross-reference
Reason / purpose for cross-reference:
read-across: supporting information
Reference
Endpoint:
sub-chronic toxicity: inhalation
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented study report equivalent or similar to OECD guideline 413.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
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:
no effects observed
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
Health and behaviour of the rats of the test groups were not visibly affected by exposure to the test material. No mortality observed in this study

BODY WEIGHT AND WEIGHT GAIN
The animals, both males and females, of all test groups gained weight at a rate similar to that of the controls.

HAEMATOLOGY
Mean haematologic values include values obtained from rats in week 6 and 13. A few statistically significant differences occurred between test animals and controls. All values were increased with respect to the corresponding items of the control group. The differences occurred haphazardly among the exposure groups. Moreover, all values were within the range of “biological variability’, or expected values for rats of this strain and age, and there never was a clear dose-response relationship for any of the criteria concerned. Therefore, these findings are considered to be of no toxicological significance.

CLINICAL CHEMISTRY
Statistically significant differences between test animals and controls were found in parameters determined in week 7 and 13, most of them in week 13. However, some were increased and other decreased; they occurred randomly among the test groups; all were within the normal range found in rats of this strain and age, and moreover, in all cases there was no indication of a dose-response relationship for any of the criteria concerned. Therefore, no toxicological significance is attached to these findings.

URINALYSIS
No exposure-related alterations were observed for any of the parameters in any of the groups exposed to 12.5, 50, 100 or 200 ppm isododecane. The few statistically significant differences in specific gravity and in volume between males exposed to 50 or 200 ppm and control males in week 13, could not be correlated with the exposure levels and were within the range of normal values for rats of this strain and age.


ORGAN WEIGHTS
Absolute brain weight and lung-to-body weight ratios of males of the 100 ppm groups were statistically significantly different from those of the controls. Because these effects were observed in one of the intermediate dose groups only and because the differences were only marginal, no toxicological significance is attached to these findings.

GROSS PATHOLOGY
Macroscopical examination at autopsy did not reveal any gross lesions that could be attributed to the treatment. All lesions observed were either about equally distributed among the various groups or they occurred in one animal or in a few animals only.


HISTOPATHOLOGY: NON-NEOPLASTIC
Microscopical examination of the kidneys revealed a dose-related increase in incidence of tubular nephrosis. These lesions were characterized by a loss of cytoplasmatic eosinophilia and striation, a loss of the brush border, and an increased cellular and nuclear size of epithelium of mainly the proximal tubules. These changes were occasionally accompanied by very small to small aggregates of mononuclear inflammatory cells.

In males, statistical analysis of the data, comparing the various treatment groups with controls revealed a significant increase of the number of animals showing tubular nephrosis at the 50, 100 and 200 ppm exposure levels. In line with these findings a slight increase was found in the incidence of inflammatory cell infiltrates. Other changes observed in the kidneys, such as hydronephrosis and calcareous deposits occurred in one or two animals only, without any apparent relation to the treatment.
Dose descriptor:
NOAEL
Effect level:
>= 200 ppm (nominal)
Basis for effect level:
other: NOAEL >= 1160 mg/m^3, No treatment-related mortality or significant adverse clinical effects occurred.
Critical effects observed:
not specified
Conclusions:
The NOAEL for isododecane is greater than or equal to 200 ppm (≥1160 mg/m3, nominal, vapor) under the test conditions of this study.
Executive summary:

This data is being read across from the source study that tested Isododecane based on analogue read across.

Five groups of rats, consisting of 20 males and 20 females each, were exposed to atmospheres containing 0, 12.5, 50, 100 and 200 ppm isododecane vapor for 6 hours a day, 5 days a week, for a period of 13 weeks. No treatment-related effects on mortality were observed and there were no significant alterations in hematological, blood chemical or urinary values, or in organ weights, which could be unequivocally attributed to treatment.  An increased incidence of minimal to slight tubular nephrosis was found in the kidneys of males at levels of 50 ppm and above.  These lesions were characterized by a loss of cytoplasmic eosinophilia and striation, a loss of brush border, and an increase in cellular and nuclear size of epithelium of mainly the proximal tubules.  The kidney effects observed in male rats are indicative of alpha-2u-globulin nephropathy.  Alpha-2u-globulin nephropathy, also known as hyaline droplet nephropathy, results from the formation of complexes with a naturally occurring protein (alpha-2u-globulin) in the kidneys of male rats.  These complexes can accumulate in the proximal renal tubule and may produce species-specific histopathological changes.  These kidney effects are specific to male rats and are not considered to be of biological relevance to humans.  Based on these results, the No Observed Adverse Effect Level (NOAEL) was greater than or equal to 200ppm (1160 mg/m3).

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1982

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
2,2,4,6,6-pentamethylheptane
EC Number:
236-757-0
EC Name:
2,2,4,6,6-pentamethylheptane
Cas Number:
13475-82-6
Molecular formula:
C12H26
IUPAC Name:
2,2,4,6,6-pentamethylheptane
Details on test material:
- Name of test material (as cited in study report): isododecane

The test material was a colourless liquid, having a boiling point range from 160 °C to
170 °C, with the following composition as reported by the principal:
— total C4 hydrocarbons < 2 ppm
— total C8 hydrocarbons 0.3 % (w/w)
— total C12 hydrocarbons 97.7 % (w/w)
consisting of: 82 % 2.2.4.6.6. pentamethylheptane and
17.7 % other C12 hydrocarbons
— total C16 hydrocarbons < 0.1 % (w/w)
— aromatics content < 10 ppm
— water content 10 ppm

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Central Institute for the breeding of laboratory animals TNO, Zeist Netherlands
- Weight at study initiation: 35-50g
- Housing: individually
- Diet (e.g. ad libitum): ad libitum, removed during exposure
- Water (e.g. ad libitum): ad libitum, removed during exposure
- Acclimation period:1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19.0-20
- Humidity (%): 40-60

IN-LIFE DATES: From: 13 January 1982 To: 16 April 1982

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
The test atmospheres are obtained as follows: filtered and dried air from the compressed—air line was passed through a glass evaporator, filled with isododecane. To obtain the desired isododecane concentration in the test atmosphere the airflow laden with isododecane was mixed in the proper ratio with the main airflow passed through the exposure chambers.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The analysis of test atmospheres to monitor the isododecane concentration was carried out by gas chromatography. Samples were taken automatically at regular intervals by means of a timer controlled 7-port gas-sampling valve. The sample loop was calibrated by comparing the area of the isododecane peak obtained from a loop sample with the area of the isododecane peak obtained from a sample taken simultaneously with a gas— tight syringe. The detector response to isododecane was calibrated by injecting known amounts of a standard solution of isododecane in diethylether.

The actual overall mean concentrations of isododecane in the various test atmospheres were 12.5, 50.2, 99.9 and 201.1 ppm.
Duration of treatment / exposure:
6h/day
Frequency of treatment:
5 days/week for 13 weeks
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 12.5, 50, 100 and 200ppm
Basis:
nominal conc.
No. of animals per sex per dose:
20 males and 20 females/dose group
Control animals:
yes

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations:just before the start of the first exposure and once every week thereafter

OPHTHALMOSCOPIC EXAMINATION:No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: weeks 6 and 12
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10 animals/sex/dose

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: weeks 6 and 12.
- Animals fasted: Yes
- How many animals:10 rats/sex/group


URINALYSIS: Yes
- Time schedule for collection of urine: weeks 6 and 12
- Animals fasted: Yes
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (see table) / No / No data

The following organs were weighed:
adrenals lungs with trachea and larynx
brain pituitary
heart spleen
kidneys testes/ovaries
liver thymus
thyroid (with parathyroid)

Samples of the organs weighed and of the following tissues and organs were preserved in a neutral aqueous phosphate—buffered 4% formaldehyde solution.

Aorta, pancreas, axillary lymph nodes, parotid salivary glands, caecum, prostate coagulating glands, sciatic nerve, colon, seminal vesicles, duodenum, skeletal muscle (thigh), epididymides, skin (flank), spinal cord, eyes, sternum (with bone marrow), ileum, stomach, jejunum, submaxillary salivary glands, mesenteric lymph nodes, sublingual salivary glands, nose (sections at 4 levels), urinary bladder, oesophagus, uterus (with cervix), all gross lesions

The lungs were fixed (after weighing) by intratracheal infusion of the fixative under 10 cm water pressure.
The kidneys of all rats were embedded in paraffin wax, sectioned at 5 um, stained with haematoxylin and eosin, and examined by light microscopy.
Statistics:
Statistical analyses of body weights and organ to-body weight ratios were carried out using analysis of co-variance followed by the Dunnetts Test, whereas the haematological and biochemical data were evaluated by means of the Mann/Whitney U-test. For statistical analysis of the histopathological data, chi-square analysis was used.

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:
no effects observed
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
Health and behaviour of the rats of the test groups were not visibly affected by exposure to the test material. No mortality observed in this study

BODY WEIGHT AND WEIGHT GAIN
The animals, both males and females, of all test groups gained weight at a rate similar to that of the controls.

HAEMATOLOGY
Mean haematologic values include values obtained from rats in week 6 and 13. A few statistically significant differences occurred between test animals and controls. All values were increased with respect to the corresponding items of the control group. The differences occurred haphazardly among the exposure groups. Moreover, all values were within the range of “biological variability’, or expected values for rats of this strain and age, and there never was a clear dose-response relationship for any of the criteria concerned. Therefore, these findings are considered to be of no toxicological significance.

CLINICAL CHEMISTRY
Statistically significant differences between test animals and controls were found in parameters determined in week 7 and 13, most of them in week 13. However, some were increased and other decreased; they occurred randomly among the test groups; all were within the normal range found in rats of this strain and age, and moreover, in all cases there was no indication of a dose-response relationship for any of the criteria concerned. Therefore, no toxicological significance is attached to these findings.

URINALYSIS
No exposure-related alterations were observed for any of the parameters in any of the groups exposed to 12.5, 50, 100 or 200 ppm isododecane. The few statistically significant differences in specific gravity and in volume between males exposed to 50 or 200 ppm and control males in week 13, could not be correlated with the exposure levels and were within the range of normal values for rats of this strain and age.


ORGAN WEIGHTS
Absolute brain weight and lung-to-body weight ratios of males of the 100 ppm groups were statistically significantly different from those of the controls. Because these effects were observed in one of the intermediate dose groups only and because the differences were only marginal, no toxicological significance is attached to these findings.

GROSS PATHOLOGY
Macroscopical examination at autopsy did not reveal any gross lesions that could be attributed to the treatment. All lesions observed were either about equally distributed among the various groups or they occurred in one animal or in a few animals only.


HISTOPATHOLOGY: NON-NEOPLASTIC
Microscopical examination of the kidneys revealed a dose-related increase in incidence of tubular nephrosis. These lesions were characterized by a loss of cytoplasmatic eosinophilia and striation, a loss of the brush border, and an increased cellular and nuclear size of epithelium of mainly the proximal tubules. These changes were occasionally accompanied by very small to small aggregates of mononuclear inflammatory cells.

In males, statistical analysis of the data, comparing the various treatment groups with controls revealed a significant increase of the number of animals showing tubular nephrosis at the 50, 100 and 200 ppm exposure levels. In line with these findings a slight increase was found in the incidence of inflammatory cell infiltrates. Other changes observed in the kidneys, such as hydronephrosis and calcareous deposits occurred in one or two animals only, without any apparent relation to the treatment.

Effect levels

Dose descriptor:
NOAEL
Effect level:
>= 200 ppm (nominal)
Basis for effect level:
other: NOAEL >= 1160 mg/m^3, No treatment-related mortality or significant adverse clinical effects occurred.

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The NOAEL for isododecane is greater than or equal to 200 ppm (≥1160 mg/m3, nominal, vapor) under the test conditions of this study.
Executive summary:

Five groups of rats, consisting of 20 males and 20 females each, were exposed to atmospheres containing 0, 12.5, 50, 100 and 200 ppm isododecane vapor for 6 hours a day, 5 days a week, for a period of 13 weeks. No treatment-related effects on mortality were observed and there were no significant alterations in hematological, blood chemical or urinary values, or in organ weights, which could be unequivocally attributed to treatment.  An increased incidence of minimal to slight tubular nephrosis was found in the kidneys of males at levels of 50 ppm and above.  These lesions were characterized by a loss of cytoplasmic eosinophilia and striation, a loss of brush border, and an increase in cellular and nuclear size of epithelium of mainly the proximal tubules.  The kidney effects observed in male rats are indicative of alpha-2u-globulin nephropathy.  Alpha-2u-globulin nephropathy, also known as hyaline droplet nephropathy, results from the formation of complexes with a naturally occurring protein (alpha-2u-globulin) in the kidneys of male rats.  These complexes can accumulate in the proximal renal tubule and may produce species-specific histopathological changes.  These kidney effects are specific to male rats and are not considered to be of biological relevance to humans.  Based on these results, the No Observed Adverse Effect Level (NOAEL) was greater than or equal to 200ppm (1160 mg/m3).