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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: comparable to guideline study
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Unnamed
Year:
1995
Report date:
1995
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report date:
1990

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
not specified
Limit test:
no

Test material

Constituent 1
Reference substance name:
2-methylpropan-1-ol
EC Number:
201-148-0
EC Name:
2-methylpropan-1-ol
Cas Number:
78-83-1
IUPAC Name:
2-methylpropan-1-ol
Details on test material:
- Name of test material (as cited in study report): 2-methyl-1-propanol, MEP
- Analytical purity: 99.8%
- Impurities (identity and concentrations): no data
- Purity test date: no data
- Lot/batch No.: no data
- Stability under test conditions: yes
- Storage condition of test material: no data

Test animals

Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Thomae GmbH, Biberach/Riss, Germany
- Age at study initiation: 10 - 11 weeks
- Weight at study initiation: mean body weight approx. 216 g
- Fasting period before study: no data
- Housing: individually in wire-mesh cages, type DK III (EBECO, Becker and Co., Castrop Rauxel, Germany), air conditioned rooms
- Diet (e.g. ad libitum): KLIBA rat/mouse laboratory diet 24-343-4, 10 mm pellets (Klingentalmühle AG, Kaiseraugst, Switzerland)
- Water (e.g. ad libitum): tap water
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 /12

Administration / exposure

Route of administration:
inhalation
Type of inhalation exposure (if applicable):
whole body
Vehicle:
unchanged (no vehicle)
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: horizontal-flow whole-body exposure chamber (glas/steel construction, volume 1.1.m³ (BASF AG, Ludwigshafen, Germany)
- Method of holding animals in test chamber: individually in wire cages
- Source and rate of air: clean air
- Method of conditioning air: no data
- System of generating particulates/aerosols: evaporator maintained at 50-70°C, TS was delivered by a continuously operating pump
- Temperature, humidity, pressure in air chamber: 21-24°C, 49-64%, minimal negative pressure
- Air flow rate: 275 L/Minute
- Air change rate: 15 air changes per hour
- Method of particle size determination: no particle size determination
- Treatment of exhaust air: no data

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatography (Hewlett-Packard GC, Model 5840 A with FID detector)
- Samples taken from breathing zone: no data
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Samples of the inhalation atmosphere were analyzed hourly during exposure.
Mean concentrations ± SD measured in inhalation chamber: 0.49 ± 0.012 mg/L, 2.50 ± 0.084 mg/L, 10.10 ± 0.330 mg/L
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/4, no further data on mating
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy or postcoitum (pc) respectively
Duration of treatment / exposure:
day 6- 15 day of pregnancy
Frequency of treatment:
6 hours / day
Duration of test:
20 days
Doses / concentrations
Remarks:
Doses / Concentrations:
0.5; 2.5; 10 mg/L
Basis:
nominal conc.
No. of animals per sex per dose:
25 females per group
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: preliminary range-finding study
- Rationale for animal assignment (if not random): random

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: No data
- Time schedule:

BODY WEIGHT: Yes
- Time schedule for examinations: day 0, 3, 6, an from then on at 3-day intervals until day 20

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: uterus and ovaries

OTHER: Yes
- gross pathology for all animals
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
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter; fixation in Bouin's solution according to the method of Barrow and Taylor (1969)
- Skeletal examinations: Yes: half per litter; fixation in ethyl acohol and staining according to a modified method of Dawson (1926)
- Head examinations: No data
Statistics:
The Dunnett test (Dunnett, 1955, 1964) was used to statistically compare body weight, body weight changes, the number of corpora lutea, implants, resorptions, live fetuses, and pre- or postimplantation losses. The Fisher's exact test (Dixon, 1981) was used for evaluating the conception rate, maternal mortality, and all fetal findings.
Historical control data:
Historical control data were used to further evaluate findings of low significance.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:no effects

Details on maternal toxic effects:
No differences in body weight/body weight gain were observed between controls and treated groups.
In addition no clinical signs of toxicity were seen.
Gross-pathologiy examination revealed no effects that could be attributed to the exposure with isobutanol.

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
10 mg/L air
Basis for effect level:
other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The fetuses did not showed any substance-related effects (no indications of any embryo-/fetotoxicity or any teratogenic effect).

The uterine weights of the treated animals were not significantly different from the controls. Compound related effects occured neither for conception rate, mean number of corpora lutea, and implantation sites nor in the values calculated for the pre- and postimplantation loss and the number of resorptions as well as viable fetuses.

Effect levels (fetuses)

open allclose all
Dose descriptor:
NOAEL
Effect level:
10 mg/L air
Basis for effect level:
other: embryotoxicity
Dose descriptor:
NOAEL
Effect level:
10 mg/L air
Basis for effect level:
other: fetotoxicity
Dose descriptor:
NOAEL
Effect level:
10 mg/L air
Basis for effect level:
other: teratogenicity

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

In no test group (0.5 mg/l - 10 mg/l) substance-related effects neither on the dams nor on the fetuses were obtained. There were no indications of substance-related maternal toxicity and embryo-/fetotoxicity or any teratogenic effect.
    
Table 1     Data on Reproduction, Maternal Body Weight Change and Uterine Weight

Dose [mg/L]

0 (sham)

0.5

2.5

10.0

Number of animals

25

25

25

25

Number of dams (pregnant animals)

21

23

23

19

Corpora lutea/dam

15.2

15.5

15.3

14.5

Implants/dam

13.6

14.6

13.1

13.8

Live fetuses/dam

12.3 (2.89)

13.7 (1.99)

12.3 (3.35)

13.2 (1.86)

Dead implants/dam

1.2

1.0

0.8

0.6

Sex ratio (male / female

53.3 / 46.7

48.7 / 51.3

53.0 / 47.0

50.8 / 49.2

Mean fetal weight [g]

3.9 (0.29)

3.9 (0.28)

3.9 (0.21)

3.9 (0.15)

Mean placental weight [g]

0.46 (0.07)

0.43 (0.06)

0.45 (0.06)

0.46 (0.05)

Mean corrected maternal body weight change [g] *

47.7 (9.21)

50.3 (6.86)

50.4 (8.25)

50.9 (6.96)

Intact uterine weight [g]

71 (15.28)

78.1 (10.12)

70.0 (17.36)

75.6 (11.59)

Numbers in parentheses indicate standard deviations

* corrected maternal body weight change = (body weight on day 20 of pregnancy) - (body weight on day 6 of pregnancy) - (uterine weight)

Tabelle 2 Fetal Anomalies


Dose [mg/L]

0 (sham)

0.5

2.5

10

Number of litters evaluated

21

23

23

19

Number of fetuses evaluated

124

164

149

128

Total fetal external malformations

Fetal incidence

0

0

0

2 (0.8)

Litter incidence

0

0

0

2 (10.5)

Total fetal soft tissue malformation

Fetal incidence

0

0

0

1 (0.8)

Litter incidence

0

0

0

1 (5.3)

Total fetal soft tissue variations

Fetal incidence

60 (48.0)

47** (31.2)

47* (35.1)

49 (40.2)

Litter incidence

19 (90.5)

18 (78.3)

20 (87.0)

17 (89.5)

Total fetal skeletal malformations

Fetal incidence

5 (3.7)

9 (5.5)

2 (1.3)

1 (0.8)

Litter incidence

5 (23.8)

7 (30.4)

2 (8.7)

1 (5.3)

Total fetal skeletal variations

Fetal incidence

59 (44.0)

75 (45.7)

72 (48.3)

51 (39.8)

Litter incidence

19 (90.5)

22 (95.7)

22 (95.7)

18 (94.7)

Numbers in parentheses indicate percentage of fetuses/litters affected

* significantly different from control; p < 0.05

** significantly different from control; p < 0.01

The external changes showed two types of malformations. Anasarca was observed in two fetuses. In addition, one showed a cleft palate.

The only soft tissue malformation was dilatation of both ventricles (globular shaped heart).

Variations were seen in all groups including controls. They occurred independent of exposure or concentration.

The skeletal examination revealed various malformations of the sternebrae and/or the vertrebral column. Variations seen in the ribs and the sternum were found in all groups.

Any observed differences between groups were within the range of biological variation and/or occurred without a clear concentration dependency.

Applicant's summary and conclusion

Conclusions:
No signs of maternal and developmental toxicity or teratogenicity were noted in this inhalation study, where the maximum exposure concentration was 10 mg/L.
Executive summary:

The developmental toxicity of isobutanol (purity 99.8%) was tested in an inhalation study in pregnant wistar rats. 25 female animals were exposed to vapors of isobutanol at concentrations of 0, 0.5, 2.5 and 10 mg/L for 6 hours/day from day 6 through 15 of gestation. All animals were killed on day 20 of gestation. The fetuses were removed and examined for compound-related effects.

There were no treatment-related effects on maternal toxicity (no mortality, no significant differences between controls and treated groups in clinical signs, body weight development, and gross pathology) even at the highest dose. The maternal NOAEL is 10 mg/L . 

The fetuses did not exhibit any signs of treatment-related embryo-/fetotoxicity or teratogenic effects. The developmental NOAEL is 10 mg/L.

(Klimisch 1990).

This inhalation developmental toxicity study in the rat is classified acceptable and satisfies the guideline requirements for a developmental toxicity study (OECD 414).

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