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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1990
Report Date:
1990
Reference Type:
publication
Title:
Studies on the Prenatal Toxicity of 3-Methyl-1-butanol and 2-Methyl-1-propanol in Rats and Rabbits following inhalation exposure
Author:
Klimisch H-J, Hellwig J
Year:
1995
Bibliographic source:
Fundamental and applied Toxicology 27: 77-89

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Methylpropan-1-ol
- Physical state: liquid
- Analytical purity: 99.8 %
- Storage condition of test material: room temperature
- Storage condition of test material: The stability was ensured for the period of the study under the specified storage conditions

Test animals

Species:
rat
Strain:
Wistar
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Dr. K. Thomae GmbH
- Age at study initiation: ca. 10-11 weeks
- Weight at study initiation: mean: 216 g
- Housing: individually
- Diet: ad libitum (no food during exposure)
- Water: ad libitum (no water during exposure)
- Acclimation period: at least 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24 °C
- Humidity (%): 30-70 %
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
Concentrations of 0.5, 2 .5 and 10 mg/liter were achieved by supplying the test substances via continuously operating pumps to evaporators maintained at 50-70 °C by a water circulation thermostat. The vapors were diluted with clean air. This vapor-air mixture was distributed to a horizontal-flow whole-body exposure chamber at a flow rate corresponding to about 15 air exchanges per hour (inhalation chamber glass/steel construction with volumes of approximately 1100 l; manufactured by BASF AG, Ludwigshafen, Germany).
Supply and exhaust air flows were adjusted by flow meters, in order to achieve a minimal negative pressure in the inhalation chambers. Pressure and temperature (21-24 °C) were measured continuously. The relative humidity (49-64 %) was checked with a hygrometer (Humicap, Vaisala, Finland).


TEST ATMOSPHERE
- Brief description of analytical method used: Samples of the inhalation atmospheres were analyzed hourly by gas chromatography (Hewlett-Packard gas chromatograph Model 5840 A with an automatic sampler Model 767 1A, FID ; column, 2 m x 2 mm with 15% Ucon LB 550 x on Chromosorb W/HP; 80/100 mesh; oven temperature, 90 °C).
- Samples taken from breathing zone: yes
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Samples of the inhalation atmospheres were analyzed hourly by gas chromatography (Hewlett-Packard gas chromatograph Model 5840 A with an automatic sampler Model 767 1A, FID; column, 2 m x 2 mm with 15% Ucon LB 550 x on Chromosorb W/HP; 80/100 mesh; oven temperature, 90 °C).
Details on mating procedure:
- Impregnation procedure: [cohoused]
- If cohoused:
- M/F ratio per cage: 1/4
- Length of cohabitation: 4 pm to 7.30 am of the following day (15.5 hours)
- Verification of same strain and source of both sexes: [yes]
- Proof of pregnancy: [vaginal plug / sperm in vaginal smear] referred to as [day 0 of pregnancy
Duration of treatment / exposure:
day 6-15 of gestation
Frequency of treatment:
6 hours/day, daily
Duration of test:
until day 20 of gestation
Doses / concentrationsopen allclose all
Dose / conc.:
0.5 mg/L air (nominal)
Dose / conc.:
2.5 mg/L air (nominal)
Dose / conc.:
10 mg/L air (nominal)
No. of animals per sex per dose:
25
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: In the range-finding study 10 pregnant rats per group were exposed to 0.5, 2.5, or 5.0 mg/liter for 6 hr each day, from Day 6 to Day 15 of gestation. No maternally toxic effects (clinical signs, body weight, various hematological, and clinicochemical parameters, gross pathological findings at necropsy) could be observed up to 5 mg/liter. This is the highest concentration (limit concentration) recommended by guidelines (EPA/TSCA, 1985). For the following full-scale studies 10 mg/liter was used as the highest concentration.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at least once daily
- Cage side observations: The behaviour and state of health of the test animals were checked at least 3 times on exposure days and, as a rule, once during the preflow period and the post-exposure observation period.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at least once daily


BODY WEIGHT: Yes
- Time schedule for examinations: The body weight of the animals was checked on day 0 (= day of detection of sperm) and on days 3, 6, 9, 12, 15, 18 and 20 p.c. As a rule, the animals were weighed at the same time of the day.


FOOD CONSUMPTION: No data

WATER CONSUMPTION: No data

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: On day 20 p.c. the dams were sacrificed in randomized order by cervical dislocation and the fetuses removed by cesarean section. After the dams had been sacrificed, they were necropsied and assessed by gross pathology.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Number of live and dead fetuses; calculation of conception rate and pre- and postimplantation losses
Fetal examinations:
- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]
- Head examinations: No data
Statistics:
The Dunnett test (Dunnett, 1955, 1964) was used to statistically compare body weight, body weight changes, corrected body weight gain, intact uterine weight, fetal and placental weights, the number of corpora lutea, implants, resorptions, live fetuses, and pre- or postimplantation losses. The Fisher's exact test (Dixon, 198 1) was used for evaluating the conception rate, maternal mortality, and all fetal findings.
Indices:
no data
Historical control data:
historical control data was available

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Details on maternal toxic effects:
The body weights of all test groups compared to the control were not statistically significantly influenced. The body weight change of all test groups compared to the control was not statistically significantly influenced. The results of the corrected body weight gain (body weight on day 20 p.c. minus body weight on day 6 p.c. minus weight of the uterus before it was opened) do not show any differences of statistical significance or biological relevance between the groups. There were no substance-induced clinical signs or findings in all test groups at any time of the study period (preflow, exposure, post-exposure observation). No deaths were recorded throughout the study period.
There were no remarkable observations at necropsy in any of the dams, which could be attributed to the test substance exposure. Only hydrometra was recorded for two animals of the control, one animal of test group 2 (2.5 mg/l) and for one animal of test group 3 (10 mg/l); all these animals did not become pregnant. Edema of lungs, which has to be related to the sacrifice of the animals, was noted for one control and one animal of the 2.5 mg/l group. There were no substantial differences concerning the uterus weights between the controls and the substance treated groups. All values lie within the range of biological relevance.
The conception rate varied between 76 and 92%.
Concerning all groups, there were no substance-related and/or statistically significant differences in conception rate, in the mean number of corpora lutea and implantation sites as well as in the value calculated for the preimplantation loss, the number of resorptions and viable fetuses.
The statistically significant dereases in postimplantation loss, total and late resorptions in the high dose females are without any biological relevance with regard to adverse effects, but considered incidental findings. All differences evident are considered to be incidental and within the normal range of deviations for animals of this strain and age.

Effect levels (maternal animals)

Key result
Dose descriptor:
NOAEL
Effect level:
10 mg/L air (analytical)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity

Maternal abnormalities

Key result
Abnormalities:
no effects observed

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Details on embryotoxic / teratogenic effects:
The sex distribution of the fetuses in test groups 1 - 3 (0 .5 - 10 mg/l) was comparable with the control fetuses. The differences observed in comparison to the control are without any biological relevance. The mean placental weights in test groups 1 - 3 (0.5, 2.5 and 10 mg/l) were not influenced by the test substance exposure to the dams. The differences observed in comparison to the control are without any biological relevance. The mean fetal weights were not influenced by the test substance exposure. All values are within the range of biological variation.
The external examination of the fetuses revealed two kinds of malformations. Anasarca was recorded for two high dose fetuses, one of them showing in addition cleft palate. Both malformations are also present at a low incidence in the historical control data.
There were no external varations.
Several so-called unclassified observations (placentae fused or necrobiotic) were recorded in 4 control and in 2 fetuses of test group 3 (10 mg/l).
The examination of the organs of the fetuses revealed only one kind of malformation (dilatation of both heart ventricles) in one fetus of the high dose group. Variations were detected in each group including the control. The very common finding (dilated renal pelvis) in the rat strain used in this study and the other kind of variation (hydroureter) occurred without a clear dose-response relationship. The differences observed in comparison to the control group including the statistically significantly decreased number of soft tissue variations in the low and in the intermediate dose are without any biological relevance.
No so-called unclassified observations (like blood coagulum around the bladder) were recorded.
Various malformations of the sternebrae and/or the vertebral column were seen in 5 fetuses of the control group, in 9 fetuses of the 0.5, in 2 fetuses of the 2.5 and in 1 fetus of the 10 mg/l group. The variations exhibited were related to the ribs (shortened 13th or accessory 14th ribs or rudimentary cervical ribs) and the sternum (sternebra(e) of irregular shape, bipartite or accessory sternebra) and were found in all groups. They occurred without any dose-response relationship. In all groups, signs of retardations (incomplete or missing ossification of hyoid, skull bones, vertebral bodies, sternebra(e), and/or metacarpal and metatarsal bones) were found. The number of fetuses with incompletely or not ossified sternebrae is statistically significantly decreased in test groups 1 (0 .5 mg/l) and 3 (10 mg/l). Furthermore, the number of fetuses with only one ossification center in the sternebra(e) is statistically significantly increased in the intermediate dose group (2.5 mg/l) and the overall number of high dose skeletal retardations is lowest in comparison to the other groups.
All differences between the groups, however, are within the range of biological variation and/or occur without a clear dose-response relationship.

Effect levels (fetuses)

open allclose all
Key result
Dose descriptor:
NOAEL
Effect level:
10 mg/L air (analytical)
Based on:
test mat.
Basis for effect level:
other: fetotoxicity
Key result
Dose descriptor:
NOAEL
Effect level:
10 mg/L air (analytical)
Based on:
test mat.
Basis for effect level:
other: teratogenicity

Fetal abnormalities

Key result
Abnormalities:
no effects observed

Overall developmental toxicity

Key result
Developmental effects observed:
no

Any other information on results incl. tables

The only statistically significant differences between the groups are the lower number of low and intermediate dose fetuses with soft tissue variations and the lower number of high dose fetuses with skeletal retardations which are, of course, without any biological relevance. The external malformations (i.e. cleft palate and/or anasarca) noted for two high dose fetuses (out of 250) and the rare soft tissue finding (i.e. globular shaped heart) observed in one high dose fetus (out of 122) are finally assessed as being of incidental nature and not related to the test substance exposure, because they occurred with very low incidences only and there were no indications of an increased malformation rate in the high dose fetuses if all classified findings are summarized. Moreover, the spontaneous occurrence of both external malformations is documented in the historical control data. All other observations, which are summarized in the relevant tables occurred in all test groups including the control to about the same amount, without any clear, dose-related differences between the groups and/or are present in the same magnitude in the historical control data.

Applicant's summary and conclusion