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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:
key study
Study period:
02/1988-03/1989
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-study equivalent to OECD guideline

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1989
Report Date:
1989

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): propylene glycol n-butyl ether, PnB, 1-butoxy-2-propanol
- Physical state: colorless liquid
- Analytical purity: 99.6%
- Lot/batch No.: EH 28043

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: ca. 8 weeks
- Weight at study initiation: ca. 160 g (males) and ca. 120 g (females)
- Fasting period before study: none
- Housing: Animals were placed in rooms designated to maintain adequate environmental conditions concerning temperature, relative humidity and photocycle for the specific species under test.
- Diet (e.g. ad libitum): ad libitum (except during exposure)
- Water (e.g. ad libitum): ad libitum (except during exposure)
- Acclimation period: at least 2 weeks

Administration / exposure

Route of administration:
inhalation
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Remarks on MMAD:
MMAD / GSD: n.a.
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 157 liter stainless steel and glass exposure chambers
- Source and rate of air: dynamic air flow conditions
- Method of conditioning air: Vapors were generated using a glass J-tube method. Liquid test material was metered into the J-tube. Compressed air, heated with a flameless torch to the minimum extent necessary, passed through the J-tube to volatalize the test material. An additional glass J-tube was inserted to add water vapor to the generating system in an effort to increase the relative humidity in the exposure chambers.
- Temperature, humidity: 22-24°C; 40-60%
- Air flow rate: 30 liter/minute

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The analytica concentration of PnB in the chamber was determined at least four times/exposure by gas chromatography using a flame ionization detector. The gas chromatographic conditions were: helium flow = 30 ml/min, hydrogen flow = 30 ml/min, air flow = 300 ml/min, oven = 110°C and detector = 190°C. A 6 foot x 1/8 inch nickel column packed with 10% OV-101 on 100/120 mesh Chromosorb WHP was used for seperation of the test material from air.
Duration of treatment / exposure:
2 weeks (9 exposure)
Frequency of treatment:
6 h daily, 5 days/week
Doses / concentrationsopen allclose all
Dose / conc.:
50 ppm (nominal)
Remarks:
Basis:
nominal conc.
Dose / conc.:
200 ppm (nominal)
Remarks:
Basis:
nominal conc.
Dose / conc.:
700 ppm (nominal)
Remarks:
Doses / Concentrations:
700 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
5
Control animals:
yes
Details on study design:
- Dose selection rationale: the highest exposure concentration was the maximum concentration that could be practically attained.
- Rationale for animal assignment: random
Positive control:
none

Examinations

Observations and examinations performed and frequency:
CAGE SIDE and CLINICAL OBSERVATIONS: Yes
- Time schedule: all animals were observed daily for overt signs of toxicity or changes in demeanor. These observations included an evaluation of the fur, eyes, mucous membranes and respiration. Behaviour pattern and nervous system activity was assessed by specific observations for lethargy, tremors, convulsions, salivation, lacrimation, diarrhea and other signs of altered central nervous system function. An additional dailt observation and routine monitoring on weekends was limited to animal husbandry procedures required to ensure the availability of food and water.

BODY WEIGHT: Yes
- Time schedule for examinations: all animals were weighed on test days 1, 3, 5, 8, and 11.

FOOD CONSUMPTION:
No data

FOOD EFFICIENCY:
No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: each animal received a pen-light ophthalmological examination prior to the initial exposure and after the final exposure to PnB.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: immediately prior to necropsy
- Anaesthetic used for blood collection: Yes (methoxyflurane)
- Animals fasted: No data
- How many animals: all animals
- Parameters examined: hematocrit (HCT), hemoglobin (HGB), erythrocyte count (RBC), total leukocyte counts and red blood cell morphology were prepared and evaluated by light microscopy for each animal.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the terminal sacrifice
- Animals fasted: No data
- How many animals: all animals
- Parameters examined: urea nitrogen (UN), alanine aminotransferase activity (ALT), aspartate aminotransferase activity (AST), alkaline phosphatase activity (AP), glucose (GLUC), total protein (TP), albumin (ALB), globulin (GLOB, calculated), total bilirubin (TBILI), cholesterol (CHOL), triglycerides (TRIG), phosphorus (PHOS), calcium (CALC), sodium (Na), potassium (K) and chloride (CL).

URINALYSIS: Yes
- Time schedule for collection of urine: during the second week of exposure
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters examined: bilirubin, glucose, ketones, blood, pH, protein, urobilinogen, pecific gravity and microscopic examinations were made on sediments from samples pooled by exposure group.

NEUROBEHAVIOURAL EXAMINATION: Yes
Behaviour pattern and nervous system activity was assessed by specific observations for lethargy, tremors, convulsions, salivation, lacrimation, diarrhea and other signs of altered central nervous system function.

Sacrifice and pathology:
All animals were fasted over night and were necropsied the day following the last exposure to the test material. Each animal was weighed, anesthetized with methoxyflurane, sampled for hematology and clinical chemistry and humanely euthanized. All animals were examined for gross pathological alterations by a veterinary pathologist and weights of the brain, heart, liver, kidneys, adrenals and testes were recorded from all animals. The necropsy included in situ examination of the eyes using a moistened glass slide pressed against the corneal surface. A complete set of tissues was collected from each animal and preserved in neutral, phosphate-buffered 10% formaline. Following examination, the lungs were distended with buffered formalin to their approximate normal inspiratory volume. The nasal cavity was flushed with formalin via the pharyngeal duct to insure rapid fixation. A complete histopathological examination of tissues (except for auditory sebaceous galnds) was made from all animals in the control and highest exposure group. Tissues examined histopathologically were processed by conventional techniques, sectioned at approximately 6 µ, stained with hematoxylin and eosin and evaluated by light microscopy. No tissues were examinated histologically from rats exposed to 50 or 200 ppm PnB.
Statistics:
Descriptive statistics (means and standard deviations) were used to report chamber concentrations, chamber temperature, and relative humidity, and white blood cell differential counts. All remaining parameters examined statistically were first tested for equality of variance using Bartlett's test. If the results from Bartlett's test rejected the equality of variances, the parameter was flagged for careful evaluation of results. All parameters were then subjected to approriate parametric analysis as described below. In-life body weights, hematologic (excluding differential WBC) and clinical chemistry parameters, terminal body weights, organ weights (absolute and relative except testes) and urine specific gravities were evaluated using a two-way analysis of variances (ANOVA) with the factors of sex and dose. Results for absolute and relavtive testes weights were analysed using a one-way ANOVA. If significant dose effects were determined in the one-way ANOVA, then separate doses were compared to controls using Dunnett's test. For those parameters examined by a two-way ANOVA, examination was first for a significant sex-dose interaction. If this existed, a one-way ANOVA was done separately for each sex. If no sex-dose interaction was identified, and a dose effect was identified, or if in the subsequent ANOVA's separated by sex a dose effect was identified, then separate ANOVA's were used for each exposure group with control. To control for multiple comparisons with control, a Bonferroni correction 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):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
effects observed, treatment-related
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
All rats survived until the scheduled necropsy with no clinical signs attributed to exposure to the test material.

BODY WEIGHT AND WEIGHT GAIN
The mean body weights of male and female rats were not adversely affected by exposure to PnB.

FOOD CONSUMPTION
no data

FOOD EFFICIENCY
no data

WATER CONSUMPTION
no data

OPHTHALMOSCOPIC EXAMINATION
A minor ocular change (hazy corea) was observed in the left eye of one male rat at 700 ppm just prior to necropsy. No other ophthalmologic changes were detected in any other animal.

HAEMATOLOGY
There were no adverse effects on hematologic parameters in male and female rats following exposure to PnB. In addition, the mean differntial leukocyte counts for male and female rats were similar to controls at all concentrations.

CLINICAL CHEMISTRY
A statistically significant decrease in total protein (TP) was observed in serum of both sexes (3.3% for males and 1.8% for females) at the lowest concentration. A statistically significant increase was also observed in blood glucose in both sexes (6.5% for males and 10.7% for females) at the highest concentration.

URINALYSIS
A statistically significant, but minimal increase in urine specific gravity was noted in both sexes at the highest concentration. All other urinary parameters were comparable to controls.

ORGAN WEIGHTS
Statistically significant increased relative but not absolute liver weights were noted in both sexes (6.7% for males and 6.5% for females) exposed to 700 ppm PnB. No effects were observed in any other organ weight.

PATHOLOGY
Microscopic examination of full sets of tissues from control and high exposure animals revealed no treatment-related effects. The few changes were generally of a minimal degree and occurred in similar incidences in both the controls and the exposed groups. These changes were considered typical of spontaneous lesions frequently noted in rats of this strain and age. Consequently, tissues were not examined from male and female rats exposed to 50 and 200 ppm PnB.

The hazy cornea of one eye observed in male rats exposed to 700 ppm PnB during the ophthalmic exam was confirmed at necropsy. Histologically, there was evidence of inflammation and mineralization of the cornea.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
> 700 ppm
Sex:
male/female
Basis for effect level:
other: highest attainable concentration.
Dose descriptor:
LOAEL
Effect level:
> 700 ppm
Sex:
male/female
Basis for effect level:
other: highest attainable concentration.

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The observed adverse effect level (NOAEL) after 9-days of exposure to PnB is 700 ppm which was the highest attainable concentration.
Executive summary:

Whole-body exposures of male and female Fischer 344 (5 per sex and group) rats to targeted concentrations of 0, 50, 200 or 700 ppm (0, 0.27, 1.08 or 3.78 mg/l) PnB vapors resulted in no adverse effects following 9 exposures, each of six hours duration. The highest exposure concentration was the maximum that could be practically attained. Each animal was evaluated for changes in body weight, clinical chemistry, haematology, urinalysis, clinical observations, selected organ weights, and gross and histopathological evaluations.

The only effect noted was a slightly increased realtive liver weight in both sexes exposed to 700 ppm PnB. However, this was unaccompanied by any histologic lesions or change in clinical chemistry parameters reflective of hepatic dysfunction. Therefore, this minimal effect on liver weight was considered to be of no toxicicologic significance.

In summary, there were no adverse effects ascribed to the inhalation of up to 700 ppm PnB, six hours/day for nine exposures over two weeks. Based on the low biological activity and moderate vapor pressure, PnB is expected to have a low potential for adverse effects following short-term exposure.