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Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
repeated dose toxicity: inhalation
Remarks:
combined repeated dose and carcinogenicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1994
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented, according to accepted guidelines

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1994
Report Date:
1994

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: OECD 451
Deviations:
yes
Remarks:
Not monitoring food consumption
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): isopropanol
- Physical state: liquid
- Analytical purity: 99.9%
- Lot/batch No.: Not reported
- Expiration date of the lot/batch: Not reported
- Stability under test conditions: 2 years
- Storage condition of test material: Not reported

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan Sprague Dawley Inc. Indianapolis, IN
- Age at study initiation: 28-30 days old
- Weight at study initiation: 121.2-165 g (males) and 93.6 - 124.3 g (females) on the first day of exposure
- Fasting period before study: None
- Housing: 2 per cage in stainless steel, wire mesh cages
- Diet (e.g. ad libitum): Pelleted, certified AGWAY PROLAB animal diet rat 3000 ad libitum
- Water (e.g. ad libitum): tap water ad libitum
- Acclimation period: 3 weeks


ENVIRONMENTAL CONDITIONS
- Temperature : 17 - 26 °C
- Humidity (%): 40-70
- Air changes (per hr): Not reported
- 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 reported
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Inhalation chamber (Wahmann Manufacting company, Timonium, MD)
- System of generating particulates/aerosols: liquid isopropanol was metered from a container by piston pump
- Temperature in air chamber: 22 +/- 4 degrees
- Air flow rate: 1000 l/min for first month and 900 l/min thereafter
- Air change rate: 14 air changes/hr for first month and 12.5 air changes/hr thereafter
- Method of particle size determination: not reported
- Treatment of exhaust air: not reported


TEST ATMOSPHERE
- Brief description of analytical method used: liquid isopropanol was metered from a container by piston pump into a heated glass evaporator and the temperature of the evaporators was maintained at the lowest level to sufficiently vaporize the test substance.
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Each exposure chamber was analyzed for isopropanol twice each hour by flame ionization gas chromatography.
Duration of treatment / exposure:
at least 104 weeks
Frequency of treatment:
6 hours/day, 5 days/week
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 500, 2500, 5000 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
65 sex/dose for the core group and 10 sex/dose for the interm sacrifice
Control animals:
yes, sham-exposed
Details on study design:

- Rationale for animal assignment (if not random): animals were assigned to 3 exposure groups and a control group using a sacrificed randomization procedure based on body weight
- Rationale for selecting satellite groups: 10 sex/group were sacrified in the middle of the study
Positive control:
None

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice a day

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly

BODY WEIGHT: Yes
- Time schedule for examinations: weekly for the first 14 weeks and then every other week after

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to experiment, and during weeks 71, 80, 104, and 107
- Dose groups that were examined: all rats


HAEMATOLOGY: Yes
- Time schedule for collection of blood: 13 months, 19 months, and 25 months
- Anaesthetic used for blood collection: Yes (identity) methoxyflurane
- Animals fasted: No
- How many animals: 10 sex/dose level

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: week 57
- Animals fasted: No
- How many animals: 10 sex/dose group

URINALYSIS: Yes
- Time schedule for collection of urine: week 57, 59, 74, and 104
- Metabolism cages used for collection of urine: No
- Animals fasted: No

NEUROBEHAVIOURAL EXAMINATION: No



Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Other examinations:
None
Statistics:
The data for the 3 treatment groups and the control group were compared with Levene's test for equality of variances, analysis of variance (ANOVA), and t-tests. The nonparmetric data were statistically evaluated with the Kruskal-Wallis test followed by the Mann-Whitney U-test. Mortality was analysed by life-table analyses. Incidence data were compared using Fishers exact test.

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):
not examined
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:
no effects observed
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:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
- Mortality rates for males in the 0, 500, 2500, and 5000 ppm groups were 82, 83, 91, and 100%, respectively. For females, 54, 48, 55, and 69%. No significant differences were noted for male rats from 500 or 2500 groups or any female rats.
-In males and females exposed to 5000 ppm; hypoactivity, lack of a startle reflex, and narcosis were identified. In males and females exposed to 2500 ppm; hypoactivity, and a lack of a startle reflex were observed. No effects in 500 ppm group. During non-exposure periods in males 5000 ppm group emaciation and dehydration was observed. In males and females in 5000 ppm there was greater numbers of rats with urine stains and swollen periocular tissue (females only). Females in the 2500 ppm group also had increased incidence of urine stains.

BODY WEIGHT AND WEIGHT GAIN
-Decreased body weights were observed for male rats from the 5000 ppm group in the first and second weeks of exposure, and then increased and at the end of week 6 body weights were increased significantly over the control group. Increased body weights were also noted for male rats from the 2500 ppm group.
-Decreased body weights were observed for female rats from the 5000 ppm group in the first and second weeks of exposure, and then increased and at the end of week 5 body weights were increased significantly over the control group. Increased body weights were also noted for female rats from the 500 ppm group. At week 72, all female body weights were significantly increased when compared to the control group.

URINALYSIS
-In males in the 5000 ppm group, in weeks 57, 59, 74, and 104 decrease in osmolality and increase in total protein and total volume were reported.
-In females rats in the 5000 ppm group, a decrease in osmolality and an increase in total volume was reported. At week 74, total glucose excreted in the urine was increased for females in the 5000 ppm group.


ORGAN WEIGHTS
- At the interim sacrifice, absolute and relative kidney weights were increased for male rats in the 5000 ppm group. Relative liver weights were increased for male rats in the 2500 ppm group. Concentration-related increases in absolute and relative testes weight was reported for male rats in 5000 ppm group. In females, increases in absolute and relative lung weight for rats in the 5000 ppm was reported.
-At the terminal sacrifice, increase in relative liver weight was noted for male rats in 2500 ppm group. In females, an increase in absolute and relative liver and kidney weights were noted for the 5000 ppm group.


GROSS PATHOLOGY
- At the interim sacrifice, an increase in granular kidneys in male rats from the 2500 and 5000 ppm groups were noted
- At the terminal sacrifice, an increase in granular kidneys in male rats from the 2500 ppm group was noted. Increased frequencies of gross lesions for male rats that died included increase incidence of thickened stomachs, granular kidneys, and color change of the kidneys for animals in 2500 and 5000 ppm groups.
- For females that died before the end of the study, an increased incidence of thickened stomachs was noted for animals from the 5000 ppm group and granular kidneys were noted for animals from the 2500 and 5000 ppm groups.


HISTOPATHOLOGY: NON-NEOPLASTIC
- At the interim sacrifice, male rats from the 5000 ppm group had an increased frequency of testicular seminiferous tubule atrophy.
-Increased frequencies of kidney lesions were observed in male rats in the 2500 and 5000 dose groups that died during the study. Increased in the frequency of mineralization in the heart, aorta, vasculature, stomach, larynx, trachea, lungs, kidney, cornea, and testes was noted for male rats in the 2500 and 5000 ppm dose groups that died during the study. Additionally, basophilic cell foci in the liver, splenic hemosiderosis, rhinitis, and squamous metaplasisa of the respiratory epithelium in the nasal cavity were reported for male rats in the 5000 ppm group that died during the study.
-Increased severity of glomerulosclerosis was observered in female rats in the 5000 ppm group. Renal disease was also increased in female rats in the 5000 ppm group.
- For female rats that died during the study, increased frequencies of mineralization in the heart, aorta, vasculature, stomach, larynx, trachea, lungs and kidney. Increase in myocardial degeneration, atrial thrombosis, splenic hemosiderosis, ocular keratitis, inflammatory and metaplastic changes in the nasal cavity, squamous metaplasia of the respiratory epithelium and glandular ectasia in the gastric mucosa was also evident in females in the 5000 ppm group that died during the study.


HISTOPATHOLOGY: NEOPLASTIC (if applicable)
-Dose-related increase in interstitial cell adenomas of the testis in male rats at interim sacrifice, at the terminal sacrifice, and in male rats that died during the study.

Effect levels

open allclose all
Dose descriptor:
NOEC
Effect level:
500 ppm
Sex:
male/female
Basis for effect level:
other: for species specific toxic effects
Dose descriptor:
NOAEC
Effect level:
5 000 ppm
Basis for effect level:
other: The report allows the conclusion that there are no substance specific adverse exposure related effects. A NOAEL of 5000 ppm can be derived.
Dose descriptor:
NOEC
Effect level:
5 000 ppm
Sex:
male/female
Basis for effect level:
other: for oncogenicity effects

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Executive summary:

The inhalation toxicity of IPA has been assessed in a 104-week oncogenicity study in rats (Burleigh-Flayer and Benson, 1994). This GLP study was conducted according to OECD test guideline 451.  IPA was administered by whole-body inhalation to groups of male and female Fischer 344 rats (75 rats/sex) for6 hours/day 5 days/weekfor at least 104 weeks at nominal concentrations of 0 (control), 500, 2500, or 5000 ppm (measure concentrations of0, 504, 2509, or 5031 ppm, respectively).  Ten rats/sex/group were assigned to interim sacrifice at Week 73. Animals were monitored for clinical observations, body and organ weights, ophthalmology examinations, hematology, urinalysis and urine chemistry examinations, gross pathology and microscopic examinations.

Exposure of rats to IPA vapour for 104 weeks produced clinical signs of toxicity (including hypoactivity, lack of startle reflex, and/or narcosis), changes in body weight, and urinalysis and urine chemistry indicative of kidney changes (decrease in osmolality and increase in total volume and/or protein) in the 2500 and 5000 ppm groups. At terminal sacrifice, increased absolute and relative kidney weights were noted in males at 2500 ppm and females at 5000 ppm. Macroscopic changes such as granular kidney were noted in males and females of 2500 and 5000 ppm groups. A number of non-neoplastic histopathological changes were observed, with the most significant being in the kidney. The only neoplastic change observed was in male rats and was an increase in interstitial cell adenomas of the testis considered to represent marked hyperplasia and not autonomous growth. The increased incidence was considered related to the unusually low frequency of testicular tumors in the control group. No increases in the incidence of neoplastic lesions were noted for female rats. In summary, the report allows the conclusion that there no adverse exposure related effects. Therefore, from the present report, a NOAEL of 5000 ppm IPA can be derived.