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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
short-term repeated dose toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1985
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with accepatble restrictions

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1985
Report Date:
1985

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)
Deviations:
yes
Remarks:
9 day treatment study with 14 day observation period
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Source: Union Carbide Corporation (South Charleston, WV)
- Name of test material (as cited in study report): Diisobutyl Ketone
- Physical state: Water white liquid with mild odor
- Analytical purity: 98.6%
- Stability under test conditions: Analyses of the DIBK test material performed prior to and following the study exposures showed no significant compositional changes. The test material contained 97.7 to 98.6 percent DIBK and DIBK isomer (bimethyl heptanone) combined.

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding laboratories, Inc., (Kingston, NY)
- Age at study initiation: 53 days
- Weight at study initiation: Males aprox. 170g, females aprox. 114g
- Housing: Two of the same sex per cage in stainless steel, wire-mesh cages (23.5cm x 20cm x 18cm high)
- Diet (e.g. ad libitum): Ad libitum, food and water were withheld during the exposures
- Water (e.g. ad libitum): Ad libitum, food and water were withheld during the exposures
- Acclimation period: The animals were acclimated to the exposure chamber (air-only exposure) for two days prior to the initiation of the DIBK exposure

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.7-23.3
- Humidity (%): 35-45
- Photoperiod (hrs dark / hrs light): 12/12

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
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Chamber was constructed from stainless steel with glass windows for animal observation, total volume of 1330L, Manufacturer: Young and Bertke, Cinncinati, Ohio
- Method of holding animals in test chamber: Cage
- Source and rate of air: 300L/min
- System of generating particulates/aerosols: Liquid DIBK was metered from a piston pump (Fluid Metering Inc., Oyster Bay, NY, Type G-6) into a heated glass evaporator similar in design as described by Carpenter, et al. (1975). The temperature in the evaporator was maintained at the lowest level sufficient to vaporize the liquid. The resultant vapour was carried into the chamber by a counter current air stream that entered the bottom of the evaporator.
- Temperature, humidity, pressure in air chamber: 23.2-26.8C° and 37-56% relative humidity
- Air flow rate: 300L/min
- Air change rate: 14/h
- Method of particle size determination: Not applicable, vapour tested
- Treatment of exhaust air: No data

TEST ATMOSPHERE
- Brief description of analytical method used: Chamber concentrations of DIBK were analyzed approximately once each hour by gas chromatography
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Chamber concentrations of DIBK were analyzed approximately once each hour by gas chromatography
Duration of treatment / exposure:
11 days: 5 days exposure following 2 days of no exposure and again 4 days of exposure
Frequency of treatment:
6h/day
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
900 ppm equivalent to 5.13 mg/L
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
300 ppm equivalent to 1.71 mg/L
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
100 ppm equivalent to 0.57 mg/L
Basis:
nominal conc.
No. of animals per sex per dose:
20 per sex per 900ppm and control group and 10 per sex per 100ppm and 300ppm groups
Control animals:
other: Yes, air-only exposure
Details on study design:
- Post-exposure recovery period in satellite groups: 14 days for 10 animals per sex of 900ppm and control group
- Dose selection rationale: A preliminary acute study indicated that the 4-hr dynamic LC50 for DIBK is greater than 866ppm (4.9 mg/L). Saturated static vapors of DIBK killed 3 of 5 males and 0 of 5 females following a single 6h exposure.
Positive control:
No

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed prior to, during, and following each exposure for signs of toxic effects.

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes: Mean bodyweight changes
- Time schedule for examinations: On the morning preceding the first, second, fifth, sixth, and seventh exposures, and immediately prior to sacrifice.

FOOD AND WATER CONSUMPTION: Mean grams/animal/day
- Time schedule for examinations: Following the eighth exposure for female rats and the ninth exposure for male rats. Food and water consumption data were also collected the evening Prior to sacrifice from recovery group female and male rats.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Prior to the first exposure and at sacrifice, the anterior chambers of the eyes of each animal were examined by a veterinarian using an indirect ophthalmoscope.
- Dose groups that were examined: All

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Day of sacrifice
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: All
- Parameters checked:leukocyte count, erythrocyte count, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration and platelet count

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Day of sacrifice
- Animals fasted: No data
- How many animals: All
- Parameters checked: aspartate aminotransferase (AST), total bilirubin, alanine aminotransferase (ALT), sodium, total protein, potassium, albumin, chloride, globulin, creatinine

URINALYSIS: Yes
- Time schedule for collection of urine: Urine was collected while the rats were in the metabolism cages (except for
the recovery females).
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters checked: urine pH, osmolality, protein, glucose, ketone, bilirubin, blood and urobilinogen

Sacrifice and pathology:
GROSS PATHOLOGY: Yes, 10 animals per sex per group were sacrificed the morning of the day following the final exposure. The recovery animals (10 per sex in the control- and 900ppm groups) were sacrificed 2 weeks later. Gross pathology was performed on kidneys, ovaries, larynx, spleen, liver, testes, lungs, trachea, nasal turbinates and all gross lesions.
HISTOPATHOLOGY: Yes, Histopathologic examination was performed on kidneys, ovaries, larynx, spleen, liver, testes, lungs, trachea, nasal turbinates and all gross lesions from the high concentration and control groups from the first (9 day) sacrifice.
Other examinations:
The liver, kidneys, lungs, and testes (males only) from all animals were weighed at sacrifice. Organ weights were recorded as absolute weights and as a percentage of body weight.
Statistics:
Results of quantitative continuous variables (such as body weight changes) were intercompared among the concentrations groups and one control group by use of analysis of variance (ANOVA), Bartlett's homogeneity of variance and Duncan's multiple range tests. The latter was used to delineate which exposure groups differed from the control, when F from the analysis of variance was significant. If Bartlett's test indicated heterogeneous variances, all groups were compared by an ANOVA for unequal variances followed if necessary by t-tests. The fiducial limit of 0.05 (two-tailed) was used as the critical level of significance for all comparisons.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
no effects observed
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
no effects observed
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:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
No mortalities occured. Lacrimation and partial closure of eyes during exposure were observed in the 900ppm animals during the two-week exposure period. Ataxia was observed in the 900ppm females after the first exposure only. There were no exposure-related clinical observations during the post exposure recovery period or in animals of the 300 and 100ppm groups.

BODY WEIGHT AND WEIGHT GAIN
There was a significant depression in male body weight gain in the high concentration group throughout the two-week exposure period and the first week of post exposure. Body weight gain in the 900ppm males returned to control values by the second week of post exposure. There was a slight depression in male body weight gain in the intermediate (300ppm) and low (100ppm) concentration groups after one exposure. However, no biological importance was attributed to this observation. Female body weight gain showed a depression in the high concentration group similar to the 900ppm males. Recovery was observed during the post exposure period. No alterations in female body weight gain were observed in the 300 and 100ppm groups.

FOOD AND WATER CONSUMPTION
A decrease in food consumption was observed in females of the high concentration group on study day 10 (8 completed exposures). Other statistically significant differences from control values were considered spurious. A dosage-related increase in water consumption was observed in males on study day 11 (9 completed exposures). This finding corresponded with an increase in urine output in the males. There were no other statistically significant differences and water consumption values in the 900ppm males returned to control values during the post exposure period.

OPHTHALMOSCOPIC EXAMINATION
There were no exposure-related ophthalmologic findings. Incidental lesions were observed in a total of five rats distributed among all exposure groups, including controls.

HAEMATOLOGY CLINICAL CHEMISTRY AND URINALYSIS
The following alterations occurred in males, but not in females: An increase in serum total protein, serum albumin, and platelet count for the 300 and 900 ppm groups, an increase in urine volume with a concomitant decrease in urine osmolality for the 100, 300 and 900ppm groups and an increase in urinary urobilinogen in the 900ppm group. Following the two-week recovery period, all alterations either returned to control values or lessened in severity

ORGAN WEIGHTS
After nine exposures of DIBK, absolute and relative liver weights were increased in both males and females of the 900 and 300ppm groups. Similarly, absolute and relative kidney weights were increased in the males of the 900 and 300ppm groups, Only relative kidney weights were increased in the females of these two groups. No significant alterations ln liver and kidney weights were observed in rats exposed to 100ppm. Lung/bronchi and testes weights were not affected by exposure to DIBK at all three test concentrations. Recovery from organ weight increases was prominent following a two-week non exposure period. In 900ppm females, liver and kidney weights were no longer significantly different from control values. In 900ppm males, relative liver weights decreased from 124% of control value to 112%, while relative kidney weights dropped from 110.8% of control value to 105.7%. The increase in relative testes weight in the recovery group 900ppm males was considered spurious.


GROSS PATHOLOGY
No treatment related gross lesions were found at necropsy.

HISTOPATHOLOGY: NON-NEOPLASTIC
There were no findings attributable to DIBK exposure except in the kidneys of male rats. Following selective staining of kidney sections, the appearance of hyaline droplet nephrosis in the proximal tubules was more severe in the DIBK-exposed rats of the 900 and 300ppm groups when compared to the male rats of the control group. The specific differences between treated and control rats were enlarged droplets, distortion of epithelial cell shape, occasional degeneration of individual epithelial cells, and occasional necrosis of individual cells and tubules in the treated males. The severity of these lesions was less in 300ppm males compared to 900ppm males and no differences were observed between control and 100ppm males. Kidneys of the 900 ppm recovery group males had lesions similar in appearance to kidneys of recovery group control males.

Effect levels

open allclose all
Dose descriptor:
NOAEC
Effect level:
5.13 mg/L air (nominal)
Sex:
male/female
Dose descriptor:
NOAEC
Effect level:
900 ppm (nominal)
Sex:
male/female
Basis for effect level:
other: no treatment-related adverse systemic effects have been observed up to the highest dose level

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The NOAEC identified based on effects that are relevant for human exposure is 900 ppm(5.13 mg/l).