Butane-1,2-diol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

TBC

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The study was conducted to international guideline with some deviations i.e. only 45 days exposure instead of 63 days, no clarity on measurement of estrous cycle or sperm analysis and no T4/T3 measurements were taken.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: OECD 422

Version / remarks:

TBC

Deviations:

yes

Remarks:

The study was conducted to international guideline with some deviations i.e. only 45 days exposure instead of 63 days, no clarity on measurement of estrous cycle or sperm analysis and no T4/T3 measurements were taken.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Butane-1,2-diol

EC Number:

209-527-2

EC Name:

Butane-1,2-diol

Cas Number:

584-03-2

Molecular formula:

C4H10O2

IUPAC Name:

butane-1,2-diol

Test animals

Species:

rat

Strain:

Crj: CD(SD)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories Japan, Inc.,
- Age at study initiation: Approximately 8 weeks
- Fasting period before study: no
- Housing: Animals were housed in polycarbonate cages (265 W × 426 D × 200 H mm, Tokiwa Kagaku Kikai Co., Ltd.) in which bedding for experimental animals (Betachip, Charles River Laboratories Japan, Inc.) was laid: 2 animals/sex/cage during quarantine and acclimatization period, 1 animal/cage during the premating treatment period, 1 male and 1 female/cage during the mating period, 1 litter/cage during the lactation period. The animals were reared on steel racks (four-tiered).
- Diet (e.g. ad libitum): Autoclaved solid feed for experimental animals (CRF-1, Oriental Yeast Co., Ltd.) was fed ad libitum. Feed was changed at a frequency of once per week. Feed for which the analytical values of residual agricultural chemicals and contaminants were confirmed to be the internal SOP-defined concentrations or less was used.
- Water (e.g. ad libitum): All animals had free access to tap water. Tap water for drinking was filtrated through a 5 μm filter and irradiated by UV light. Water for drinking was changed at a frequency of once per week. Water quality tests in compliance with the Water Supply Law were conducted regularly and the analysis results were confirmed to be within the acceptance criteria as stipulated by the annex of the Ordinance of the Ministry of Health and Welfare No. 56.
- Acclimation period: At least 6 days prior to start of treatment.
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20°C to 25°C.
- Humidity (%): 40 - 70%
- Air changes (per hr): 12 times/hour
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: Animal arrival August 28, 1991 but date of necropsy was not documented.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test article was dissolved in purified water and dosing solutions at the nominal concentrations were prepared. The preparation was conducted once weekly and the dosing solutions were kept refrigerated and protected from light until immediately before dosing.

For stability of the test article in the dosing solution, the dosing solutions for the low dose group and high dose group were analyzed before the commencement of dosing in a laboratory of Mitsubishi Kasei Institute of Toxicological and Environmental Sciences, Co., Ltd., and the test article was confirmed to be stable for 14 days under the storage condition.

DIET PREPARATION: N/A 
 - Rate of preparation of diet (frequency):
 - Mixing appropriate amounts with (Type of food): 
 - Storage temperature of food:
 
 VEHICLE
 - Justification for use and choice of vehicle (if other than water): N/A
- Concentration in vehicle: The concentrations measured for all dose levels were within ±2% of the nominal concentrations.
- Amount of vehicle (if gavage): The concentrations measured for all dose levels were within ±2% of the nominal concentrations.
- Lot/batch no. (if required): Not stated 

- Purity: Not stated.

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: up to 1 week
- Proof of pregnancy: vaginal smears were collected from females in the morning every day, which were then stained with Giemsa’s stain solution and examined microscopically. When a sperm positive vaginal smear and/or plug was observed, mating was considered successful, and the day of successful mating was regarded as gestation day 0.
- Further matings after unsuccessful attempts: The unmated females were necropsied at 14 days after the end of the mating period (35 days after the commencement of treatment) and their ovaries were stored.
- After successful mating each pregnant female was caged (how): The animals were reared on steel racks (four-tiered). Stainless steel feeders for solid feed (Tokiwa Kagaku Kikai Co., Ltd.).
- Any other deviations from standard protocol: Not stated

Duration of treatment / exposure:

40 - 45 days

Frequency of treatment:

Once daily

Duration of test:

40 - 45 days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

40 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

200 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

10

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: A one-week preliminary repeat dose study in 8-week-old SD rats was conducted at doses of 0, 100, 300, and 1000 mg/kg. As a result, a slight tendency for swelling of the liver was noted in the females of the 1000 mg/kg. Based on the results, 1000 mg/kg was selected as the high dose in this study and 200 mg/kg and 40 mg/kg were selected as the intermediate and low dose groups, respectively, in a geometric ratio of 5.
- Rationale for animal assignment (if not random): n/a
- Rationale for selecting satellite groups: n/a
- Post-exposure recovery period in satellite groups: n/a
- Section schedule rationale (if not random): n/a

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Not specified

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
or males, body weights were measured on the day of the commencement of dosing and thereafter once per week. For females, bodyweights were measured on the day of the commencement of dosing and thereafter once per week before mating and after the completion of mating on gestation days 0, 7, 14, and 20, and lactation days 1 and 4.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
For males, food consumption was measured once per week from the commencement of dosing, except for the mating period. For females, gross weights of food were measured once per week before mating, and after the completion of mating, on gestation days 0, 7, 14, and 20, and Lactation Days 1 and 4.

FOOD EFFICIENCY: No

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

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: 21 hours after completion of treatment
- Anaesthetic used for blood collection: Not specified
- How many animals: All surviving males.
- Parameters checked in table: Yes

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: 21 hours after completion of treatment
- Animals fasted: Yes, but details not disclosed.
- How many animals: All surviving males.
- Parameters checked in table: Yes

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

IMMUNOLOGY: No

OTHER: Yes (see below);

ESTROUS CYCLE: Yes
- Dry smears - not specified.
- Wet smears - not specified.

THYROID HORMONE ANALYSIS: No

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: No
- Number of late resorptions: No
- Other: Gestation length & index and delivery index

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Not stated
- Skeletal examinations: Not stated
- Head examinations: Not stated

Statistics:

Bartlett's test for homogeneity of variance, when the variances were heterogeneous, the Kruskal-Wallis test was performed. Dunnett’s method in case of an equal number of animals between the groups or using Scheffe’s method in case of a different number of animals between the groups. For count data, the data were tested by Fisher's exact probability test.

Indices:

Offspring viability indices including; viability index, lactation index and sex ratio.

Historical control data:

Not stated

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

In females of the 1000 mg/kg group, post-treatment decreases in locomotor activity were observed in more than half of the animals and hypopnea in a few animals. Both signs were transient in nature. The number of affected animals decreased over time, and on day 6 or later, the sign occurred only in one animal until gestation day 5 (at 21 days after the commencement of treatment). No abnormalities occurred in males. In addition, hair loss was observed in one female of the 1000 mg/kg group but the finding is considered a spontaneous finding.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

For glucose in the 40 mg/kg group and total bilirubin in the 200 mg/kg group, statistical differences were noted. However, no related changes suggestive of the effects of the test article were noted.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

In both the control group and 1000 mg/kg group, focal myocardial degeneration in the heart, microgranuloma in the liver, fatty change of hepatocytes, and brown pigmentation in tubular epithelial cells, cyst, focal basophilic change in renal tubules and fatty change of tubular epithelia in the kidneys were sporadically found. No between-group differences in the incidences of these changes were noted; therefore, these changes were not indicative of the treatment effects. In addition, slight increases of hematopoietic cells in the spleen and diffuse chronic hypertrophy in the fascicular zone of the adrenals were found in almost all animals in the control and 1000 mg/kg groups without any between-group differences.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not specified

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

not specified

Details on maternal toxic effects:

Mortality: No deaths ascribable to the treatment occurred.

Clinical signs: In females of the 1000 mg/kg group, post-treatment decreases in locomotor activity were observed in more than half of the animals and hypopnea in a few animals. Both signs were transient in nature. The number of affected animals decreased over time, and on day 6 or later, the sign occurred only in one animal until gestation day 5 (at 21 days after the commencement of treatment). No abnormalities occurred in males. In addition, hair loss was observed in one female of the 1000 mg/kg group but the finding is considered a spontaneous finding.

Clinical chemistry: For glucose in the 40 mg/kg group and total bilirubin in the 200 mg/kg group, statistical differences were noted. However, no related changes suggestive of the effects of the test article were noted.

No effects were observed on bodyweight, food consumption, organ weight and heamatology.

Macroscopy: Bilateral atrophy of the testes was found in one male of the 1000 mg/kg group (animal number: DM09). In the other animals, no abnormalities were found in either males or females of any groups.

Microscopy: In both the control group and 1000 mg/kg group, focal myocardial degeneration in the heart, microgranuloma in the liver, fatty change of hepatocytes, and brown pigmentation in tubular epithelial cells, cyst, focal basophilic change in renal tubules and fatty change of tubular epithelia in the kidneys were sporadically found. No between-group differences in the incidences of these changes were noted; therefore, these changes were not indicative of the treatment effects. In addition, in females, slight increases of hematopoietic cells in the spleen and diffuse chronic hypertrophy in the fascicular zone of the adrenals were found in almost all animals in the control and 1000 mg/kg groups without any between-group differences.

The atrophy of the testes of the male in the 1000 mg/kg found in necropsy was reflected by extensive atrophy of seminiferous tubules found in histopathology. The change was associated with slight bilateral atrophy of the epididymides. In the testes, degeneration, vacuolation, and multinucleated cell formation were observed in the sperm cells, but no abnormalities were observed in Sertoli cells or interstitial cells. In the other animals, including those of the 40 and 200 mg/kg groups, no abnormalities were found in the testes or epididymides. The other changes included germinal center deficiency in the spleen and unilateral extensive hemorrhagic necrosis in the adrenal cortex in one female of the 1000 mg/kg group (D07).

Reproductive performance: Mating was not confirmed only in two pairs of the 40 mg/kg group. For the other animals, mating was conducted during the first estrous cycle. All mated females became pregnant, and no treatment effects were noted in the copulation index or fertility index.

Delivery and lactation function: In each group, the pregnant females delivered normally. No statistical difference was noted in gestation length, gestation index, corpora lutea count, implantation site count, implantation index, or delivery index. No abnormalities in lactation behaviors after delivery were noted in any litters of any groups.

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

>= 1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Remarks on result:

not determinable due to absence of adverse toxic effects

Maternal abnormalities

Key result

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Visceral malformations:

no effects observed

Other effects:

not specified

Details on embryotoxic / teratogenic effects:

Effects on offspring

In the observations on lactation day 1, no external anomalies were found in any groups, and no statistical differences between the control group and treatment groups were noted in the total number of offspring, number of live offspring, or sex ratio.

Between lactation days 1 and 4, deaths occurred sporadically in each group. However, no statistical differences between the control group and treatment groups were noted in viability of offspring at birth or viability of neonates.

One offspring of the 40 mg/kg group presented a sign of anemia on lactation day 2 and died on lactation day 3. In the other offspring, no abnormalities were observed.

For both males and females, from lactation days 1 through 4, no significant differences between the control group and treatment groups were noted in bodyweight or body weight gain.

Thymic remnant in the neck was found in 3, 2, 5, and 2 animals in the order from the control to high dose groups, and the left umbilical artery was found in one animal of the control group. In addition, hepatic (a) white spot(s) was (were) found in one female of the 1000 mg/kg group. A microscopic examination of the liver of the animal revealed extensive necrosis in the perilobular area and diffuse fatty change of hepatocytes. In the necropsy of dead animals, dilatation of the renal pelvis was found in one animal of the 200 mg/kg group. All these changes had no dose-dependency in their incidences or occurred in a very few animals; therefore, they were not ascribable to treatment.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

> 1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Applicant's summary and conclusion

Conclusions:

Daily repeat oral gavage doses of 1,2-butanediol at 40, 200, and 1000 mg/kg were administered to rats (males) from 14 days prior to mating and during the mating period and thereafter for a total of 42 days and to females from 14 days prior to mating and during the period covering mating, gestation, and delivery until lactation day 3 did not result in adverse effect. Therefore, the no observed adverse effect levels (NOAEL) of 1000 mg/kg for general toxicity and > 1000 mg/kg developmental toxicity.

Executive summary:

OECD 422 - Daily repeat oral gavage doses of 1,2-butanediol at 40, 200, and 1000 mg/kg were administered to SD rats. The test article was orally administered once daily to males from 14 days prior to mating and during the mating period and thereafter for a total of 42 days and to females from 14 days prior to mating and during the period covering mating, gestation, and delivery until lactation day 3. Toxicological effects on parent animals and effects on reproductive performance, such as gonadal function, mating behaviour, fertility, delivery, and lactation were investigated.

No mortality was observed, body weight, food consumption, haematology and organ weight were unaffected throughout the study.  For glucose in the 40 mg/kg group and total bilirubin in the 200 mg/kg group, statistical differences were noted. However, no related changes suggestive of the effects of the test article were noted.

In females of the 1000 mg/kg group, post-treatment decreases in locomotor activity were observed in more than half of the animals and hypopnea in a few animals. Both signs were transient in nature. The number of affected animals decreased over time, and on day 6 or later, the sign occurred only in one animal until gestation day 5 (at 21 days after the commencement of treatment). No abnormalities occurred in males. In addition, hair loss was observed in one female of the 1000 mg/kg group, but the finding is considered a spontaneous finding.

Bilateral atrophy of the testes was found in one male of the 1000 mg/kg group (animal number: DM09), this was reflected by extensive atrophy of seminiferous tubules found in histopathology and associated with slight bilateral atrophy of the epididymides. In the testes, degeneration, vacuolation, and multinucleate cell formation were observed in the sperm cells, but no abnormalities were observed in Sertoli cells or interstitial cells. In the other animals, including those of the 40 and 200 mg/kg groups, no abnormalities were found in the testes or epididymides. The other changes included germinal centre deficiency in the spleen and unilateral extensive hemorrhagic necrosis in the adrenal cortex in one female of the 1000 mg/kg group (D07).

In both the control group and 1000 mg/kg group, focal myocardial degeneration in the heart, microgranuloma in the liver, fatty change of hepatocytes, and brown pigmentation in tubular epithelial cells, cyst, focal basophilic change in renal tubules and fatty change of tubular epithelia in the kidneys were sporadically found. No between-group differences in the incidences of these changes were noted; therefore, these changes were not indicative of the treatment effects. In addition, in females, slight increases of hematopoietic cells in the spleen and diffuse chronic hypertrophy in the fascicular zone of the adrenals were found in almost all animals in the control and 1000 mg/kg groups without any between-group differences.

Reproductive performance for both males and females, no abnormality was noted in copulation index or fertility index, and no effect of the test article was noted in gestation length, delivery, or nursing behaviour. Furthermore, the examination on corpora lutea count, implantation site count, implantation index, gestation index, delivery index, offspring count, and viable offspring count revealed no changes suggestive of effects of the test article on ovulation, implantation, or subsequent embryonic development. In addition, no abnormality was noted in the external surface of the offspring, viability index, bodyweight at birth, or bodyweight gain after birth. In necropsy of neonates, thymic remnant in the neck and left umbilical artery were sporadically found. However, these findings were those often spontaneously observed at the end of the fetal stage, and the incidences were not correlated with dose levels. In one female of the 1000 mg/kg group, (a) white spot(s) was(were) found, which was (were) hepatic necrosis and fatty change. These changes are known to be induced by various factors, and it is widely recognised that these changes are also induced by circulatory impairment and metabolic disorder including nutritional disorder. In this study, however, the changes occurred in only one animal and were not found in the other neonates; therefore, they were not considered treatment related.

Therefore, the no observed effect levels (NOEL) under the experimental conditions used were considered 200 mg/kg for repeat dose toxicity and 1000 mg/kg for reproductive and developmental toxicity while the no observed adverse effect levels of 1000 mg/kg for repeat dose toxicity and > 1000 mg/kg for developmental toxicity.