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Toxicological information

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:
17 April 1978 - 30 March 1979
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with acceptable restrictions. Limited documentation on animal housing, only 2 concentrations tested, exposure duration 84 days, no ophthalmological examination.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1979
Report Date:
1979

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
no
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): MRD-78-26
- Physical state: Clear colourless liquid
- Analytical purity: 100% pure commercial product
- Lot/batch No.: SN 03613EC
- Other: Source: Exxon Corporation, Linden, N.J. 07036

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Wilmington, Mass. 01887
- Age at study initiation: males 6 wks, females 7 wks
- Weight at study initiation: males 185 g mean (range 165-217 g); females 162 g mean (range 138-189)
- Fasting period before study: no
- Housing: paired in chamber, individual out of chamber
- Diet (e.g. ad libitum): Standard laboratory pellet diet (Purina Laboratory Chow) ad libitum (out of chamber only)
- Water (e.g. ad libitum): ad libitum (out of chamber only)
- Acclimation period: 13 days

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Remarks on MMAD:
MMAD / GSD: not applicable, vapour
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: stainless steel and glass chambers with 1 cubic meter total volume (760 L effective volume)
- Source and rate of air:
- Method of conditioning air:
- System of generating particulates/aerosols:
- Temperature, humidity, pressure in air chamber:
- Air flow rate: 134 L/min
- Air change rate: 8 per hour
- Method of particle size determination: not applicable, vapour


TEST ATMOSPHERE
- Brief description of analytical method used: Atmospheric sampling was performed using a Wilks Scientific Corp., Miran 1A Ambient Air Analyzer (long pathlength infrared). A calibration curve relating the absorption to the airborne concentration of the test material was prepared. On each exposure day, three samples were drawn from each exposure chamber (at about 1, 3, and 5 hours) and the exposure concentration calculated by comparing the absorption of this sample to the standard curve.
In addition, the composition of the test atmosphere was analyzed for homogeneity by gas chromatographic analysis of several charcoal-trapped vapour samples collected from each chamber during the 12-wk exposure period
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The test atmosphere was analysed for concentration and homogeneity by measurement of the infrared spectrum and by gas chromatographic analysis, respectively. Based on the infrared analysis the animals were exposed to cumulative mean concentrations of 385 and 1200 ppm, respectively. Gas chromatographic analysis of the chamber atmosphere demonstrated that the test material composition was representative of the initial sample.
Duration of treatment / exposure:
12 weeks
Frequency of treatment:
6 hours/day, 5 days/week
Doses / concentrations
Remarks:
Doses / Concentrations:
400, 1200 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
35
Control animals:
yes, sham-exposed
Details on study design:
- Rationale for animal assignment (if not random): assigned to group by weight
Positive control:
none

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations included: incidence of abnormal signs


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly (full recorded physical assessment)


BODY WEIGHT: Yes
- Time schedule for examinations: weekly, from 5 days prior to exposure through termination


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes (retro-orbital sinus)
- Time schedule for collection of blood: 4, 8, 12 weeks
- Anaesthetic used for blood collection: Yes (exsanguination under ether anesthesia)
- Animals fasted: Yes (fasted overnight prior to bleeding)
- How many animals: 10/sex/group (4 and 8 weeks), 15/sex/group (12 weeks, all survivors)
- Parameters examined: hemoblobin, hematocrit, erythrocyte count, clotting time, total and differential leukocytes


CLINICAL CHEMISTRY: Yes (retro-orbital sinus)
- Time schedule for collection of blood: 4, 8, 12 weeks
- Animals fasted: Yes (exsanguination under ether anesthesia)
- How many animals: 10/sex/group (4 and 8 weeks), 15/sex/group (12 weeks, all survivors)
- Parameters examined: blood urea nitrogen, serum glutamic pyruvic transaminase (SGPT), glucose, alkaline phosphatase


OTHER:
Organ weights and organ/body weight ratios determined in animals sacrificed at 4, 8 and 12 weeks (adrenals, brain (sans pituitary), gonads, kidneys, liver, lungs)
Sacrifice and pathology:
GROSS PATHOLOGY: Yes: adrenals, brain (without pituitary), gonads, kidneys, liver, lungs
HISTOPATHOLOGY: Yes (control and 1200 ppm group): adrenals (2), bone marrow (sternal), brain (2 sections), eye, gonad, heart (with coronary vessels) intestine, colon, duodenum, ileum, kidneys (2), liver (2 sections), lung (2 sections), lymph node (mesenteric), mammary gland, pancreas, pituitary, salivary gland, skeletal muscle, skin, spinal cord (cervical), spleen, stomach, thyroid, trachea, urinary bladder, uterus/prostate, gross lesions, tissue masses
Statistics:
Body weight, hematology and clinical chemistry parameters, organ weights and organ/body weight ratios were statistically evaluated. Mean values for all treatment groups were compared to the control group at each time interval (4, 8, and 12 weeks). Hematology and clinical chemistry parameters were compared by the F-test and Student's t-test. When variances differed significantly (F-test), Student's t-test was appropriately modified using Cochran's approximation (t'). Body weight, organ weight and organ/body weight ratios were compared to control according to Dunnett.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
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:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
No treatment-related mortality occured (1 male of the 1200 ppm group was accidentally killed).
Several animals in all groups exhibited dry rales and red and mucoid nasal discharge (more numerous in the treated groups, but not clearly treatment-related), moist rales, excessive lacrimation, hair loss and chromodacryorrhea were found in a limited number of animals in all groups (not treatment-related)
1200 ppm: singular occurrences of excessive salivation, laboured, irregular breathing; yellow staining of the anogenital fur in 6 males and 35 females from wk 3 through 12
400 ppm: yellow staining of the anogenital fur in 2 females
Control: singular occurrences of excessive salivation and bleeding inside the ear; a limited number of animals with brown staining of the ano-genital region and soft stool; three observations (in one animal) of an abnormally dark red or red and yellow eye

BODY WEIGHT AND WEIGHT GAIN
1200 ppm: mean body weights in males significantly higher at wk 2 and significantly lower (p?0.05) from wk 8 through 11 than in controls
400 ppm: mean body weight and weight gains in males similar to control throughout the study, except wk 2 (significantly higher, p?0.01), in females mean body weights significantly depressed (p?0.01 and p?0.05) at wk 5 through 8.

HAEMATOLOGY
Several statistically significant (p < 0.05 and p < 0.01) decreases in mean hematocrit values of males and females of both treated groups at wk 4 and 8, statistically significant decreases (p?0.05) in mean hemoglobin values at wk 8 in the males of both treated groups and the females of the 400 ppm group at wk 4. Mean red blood cell values were significantly decreased in 1200 ppm males at wk 8 and 400 ppm females at wk 12. Since all values were within normal biological limits, these findings were not considered to be treatment-related.

CLINICAL CHEMISTRY
Mean SGPT levels were significantly (p?0.01) depressed in 1200 ppm males at wk 4, 400 and 1200 ppm males at wk 8, and in 1200 ppm females at wk 12. Mean blood urea nitrogen levels were significantly increased in the males of both treated groups at wk 8. Mean glucose levels were significantly (p?0.01 or p?0.05) increased in 400 ppm males at wk 8, decreased in 1200 ppm males at wk 12, and decreased in 1200 ppm females at wk 4 and 12. The observed effects were not considered to be treatment-related.

ORGAN WEIGHTS
Mean kidney weights and kidney/body weight ratios were significantly (p?0.05) higher in the 1200 ppm males at wk 8. In the 400 ppm males these values were also elevated, but not statistically significant. At wk 12, mean kidney weights and kidney/body weight ratios for 400 and 1200 ppm males were significantly (p?0.01) elevated, indicating a treatment-related response. The only other statistically significant (p?0.05) findings were elevated mean adrenal/body weight ratios for the 1200 ppm males at wk 4 and the 400 ppm females at wk 12.

GROSS PATHOLOGY
Microscopic evaluation of organs and tissues from the control and high level exposure groups revealed a mild tubular injury in the kidneys of some exposed male rats sacrificed after exposure for 8 and 12 wk. Other changes were unrelated to group or sex and were considered to be spontaneous.

HISTOPATHOLOGY: NON-NEOPLASTIC
See Gross Pathology

Effect levels

Key result
Dose descriptor:
NOAEC
Effect level:
1 200 ppm (nominal)
Sex:
male
Basis for effect level:
other: overall effects

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Significantly increased mean kidney weights and kidney/body weight ratios were observed in males at 400 ppm, which were considered to be treatment-related by the authors of the study.

The kidney was confirmed as potential target organ for the test material-induced toxicity by the observation of mild tubular injury found in the histopathological examination of high dose males.

The fact, that these effects were strictly limited to male rats and that the test substance belongs to a category of substances which are known for their ability to induce nephropathy in male rats due to their exclusive expression of alpha-2u-globulin, the protein known to play the crucial role in the onset of this disease, the observed effects in the kidney have to be regarded as species-specific and therefore not relevant for risk assessment in humans. Therefore, these effects were not considered for the determination of the NOAEC.

Applicant's summary and conclusion

Conclusions:
In a 12 -week inhalation study with rats the test substance hydrocarbons, C7 -C9, isoalkanes was tested. Significantly increased mean kidney weights and kidney/body weight ratios were observed in males at 400 ppm, which were considered to be treatment-related by the authors of the study.

The kidney was confirmed as potential target organ for the test material-induced toxicity by the observation of mild tubular injury found in the histopathological examination of high dose males.

The fact, that these effects were strictly limited to male rats and that the test substance belongs to a category of substances which are known for their ability to induce nephropathy in male rats due to their exclusive expression of ?2u-globulin, the protein known to play the crucial role in the onset of this disease, the observed effects in the kidney have to be regarded as species-specific and therefore not relevant for risk assessment in humans. Therefore, these effects were not considered for the determination of the NOAEC.

Renal effects were strictly limited to males, therefore the authors concluded an ?2u-globulin-related mechanism for the observed nephropathy. The observation was not considered for determination of the NOAEC.
Executive summary:

In a 12 -week inhalation study with rats the test substance hydrocarbons, C7 -C9, isoalkanes was tested. Significantly increased mean kidney weights and kidney/body weight ratios were observed in males at 400 ppm, which were considered to be treatment-related by the authors of the study. The kidney was confirmed as potential target organ for the test material-induced toxicity by the observation of mild tubular injury found in the histopathological examination of high dose males. The fact, that these effects were strictly limited to male rats and that the test substance belongs to a category of substances which are known for their ability to induce nephropathy in male rats due to their exclusive expression of ?2u-globulin, the protein known to play the crucial role in the onset of this disease, the observed effects in the kidney have to be regarded as species-specific and therefore not relevant for risk assessment in humans. Therefore, these effects were not considered for the determination of the NOAEC. Renal effects were strictly limited to males, therefore the authors concluded an ?2u-globulin-related mechanism for the observed nephropathy. The observation was not considered for determination of the NOAEC.