2,2-dimethylbutane

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

198903-27 to 1989-04-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable without restrictions because it is well documented and follows OECD Guideline 414.

Justification for type of information:

A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

developmental toxicity

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

198903-27 to 1989-04-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable without restrictions because it is well documented and follows OECD Guideline 414.

Justification for type of information:

A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes (incl. QA statement)

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, NY
- Age at study initiation: 42 days at arrival
- Weight at study initiation: 30 g male, 24 g females
- Housing: individually in stainless steel wire mesh cages, identified with toe clips and ear notches
- Diet (e.g. ad libitum): Prolab Certified Rodent Food, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: 2 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 66-72 degree F
- Humidity (%): 50-71
- Photoperiod (hrs dark / hrs light): 12 hrs light/12 hrs dark


IN-LIFE DATES: From: April 5, 1989 To: April 18, 1989

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 4320 l glass and stainless steel chambers.
- Method of holding animals in test chamber: cages
- Source and rate of air: 1000 l/min
- Method of conditioning air: Test substance was metered from a piston pump into one or two heated glass evaporator with a temperature of 27-70 degree C. Conditioned air was passed through the evaporator, where it carried the vapor into the exposure chamber.
- Temperature, humidity: monitored every 30 minutes
- Air flow rate: 1000 l/min
- Air change rate: 20 min, 14 air changes per hour
- Treatment of exhaust air: filtration


TEST ATMOSPHERE
- Brief description of analytical method used: GC with flame ionization detection
- Samples taken from breathing zone: yes, 7 times per exposure

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples were taken seven times per exposure period and analyzed with GC-FID. Distribution of test substance was evaluated by sampling five different areas of the exposure chamber.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
- Length of cohabitation: March 27, 1989-April 2, 1989
- Proof of pregnancy: vaginal plug referred to as day 0

Duration of treatment / exposure:

gestation day (GD) 6-15

Frequency of treatment:

6 hrs/day

Duration of test:

GD 18

Remarks:

Doses / Concentrations:
0, 900, 3000, 9000 ppm
Basis: nominal conc.

Remarks:

Doses / Concentrations:
914, 3026, 9107 ppm
Basis: analytical conc.

No. of animals per sex per dose:

30 pregnant females per exposure group

Control animals:

yes

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations: mortality, clinical signs



BODY WEIGHT: Yes
- Time schedule for examinations: GD 0, 6, 9, 12, 15


FOOD CONSUMPTION: Yes

WATER CONSUMPTION: Yes


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 18
- Organs examined: gravid uterus, ovaries, cervix, vagina, abdominal cavities, thoracic cavities, liver, kidneys

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Number of corpora lutea: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: live and dead fetuses

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter were examined for thoracic and abdominal visceral abnormalities
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: [all per litter / half per litter / #? per litter ] / No / No data

Statistics:

Quantitative continuous variables were compared by use of Levene's test for equal variance, analysis of variance, and t-tests with Bonferroni probabilities. Nonparametric data was evaluated using the Kruskal-Wallis test, followed by the Mann-Whitney U test. Indices were compared using Fisher's exact test. 0.05 was used as the criteria for statistical significance.

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
There were no significant treatment related effects to body weight, clinical signs, food consumption, weight changes, or organ weights. There was increased water consumption on GD 6-9, 9-12, 6-15, and 15-18 in the 3000 ppm group. There was also increased water consumption in the 900 ppm group on GD 3-6 and 6-9. There was a statistically significant increase in lung color changes in the 9000 ppm group. Four dams also had brown foci. Two dams in the 3000 ppm group had lung color changes as well, and three had dark brown foci.

Key result

Dose descriptor:

NOAEC

Effect level:

900 ppm

Basis for effect level:

other: maternal toxicity

Key result

Dose descriptor:

LOAEC

Effect level:

3 000 other: ppm (10560 mg/m3)

Basis for effect level:

other: maternal toxicity

Key result

Abnormalities:

effects observed, treatment-related

Localisation:

other: Colour changes in lungs

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Gestational parameters were similar between exposure and control groups. There was a statistically significant increase in two skeletal malformations in the 9000 ppm group, bilateral bone island at the first lumbar arch, all intermediate phalanges of the hindlimb unossified. No other dose related abnormalities were noted.

Key result

Dose descriptor:

NOAEC

Effect level:

3 000 other: ppm (10560 mg/m3)

Sex:

male/female

Basis for effect level:

skeletal malformations

Key result

Dose descriptor:

LOAEC

Effect level:

9 000 other: ppm (31680 mg/m3)

Sex:

male/female

Basis for effect level:

skeletal malformations

Key result

Abnormalities:

effects observed, treatment-related

Localisation:

skeletal: vertebra

skeletal: hindlimb

Key result

Developmental effects observed:

yes

Lowest effective dose / conc.:

9 000 ppm

Treatment related:

yes

Relation to maternal toxicity:

not specified

Dose response relationship:

yes

Relevant for humans:

not specified

Results of Developmental Toxicity Study on Mice

	0.0 ppm	900.0 ppm	3000.0 ppm	9000.0 ppm
No. of dams with lung color change	0	0	2	12
All inter. Phalanges (hindlimb) unossified (litters, %)	76.9	72.0	84.0	100.0
Bone island - first lumbar arch - bilateral  (litters, %)	0.0	0.0	8.0	23.1

Conclusions:

In mice, the maternal NOAEC was 900 ppm, and the maternal LOAEC was 3000 ppm (10560 mg/m3) based on color changes in the lungs. The developmental NOAEC was 3000 ppm and the LOAEC was 9000 ppm (31680 mg/m3) in mice.

Executive summary:

The purpose of this study was to examine the developmental toxicity of commercial hexane in mice. Groups of 30 pregnant female mice were exposed to concentrations of 0, 900, 3000, or 9000 ppm for 6 hrs/day during gestational days 6 -15. The animals were then sacrificed on GD 18. During the study, the animals were examined for clinical signs, mortality, food and water consumption, and body weights taken. After sacrifice, the internal organs were examined, and the uterus was examined for viable fetuses, number of resorptions, and number of corpora lutea. Fetuses were examined for malformations.

Necropsy revealed color changes in the lungs of females in the 3000 and 9000 ppm groups. Fetuses in from dams in the 9000 ppm group had a statistically significant increase in some skeletal abnormalities. The maternal NOAEC in mice was 900 ppm (3168 mg/m³), and the LOAEC 3000 ppm based on lung color changes. The developmental NOAEC in mice was 3000 ppm (10560 mg/m³) and the LOAEC 9000 ppm (31680 mg/m³) based on skeletal abnormalities.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1989

Report date:

1989

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

commercial hexane

IUPAC Name:

commercial hexane

Details on test material:

- Name of test material (as cited in study report): commercial hexane
- Composition of test material, percentage of components: 52.19% n-hexane

Test animals

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, NY
- Age at study initiation: 42 days at arrival
- Weight at study initiation: 30 g male, 24 g females
- Housing: individually in stainless steel wire mesh cages, identified with toe clips and ear notches
- Diet (e.g. ad libitum): Prolab Certified Rodent Food, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: 2 weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 66-72 degree F
- Humidity (%): 50-71
- Photoperiod (hrs dark / hrs light): 12 hrs light/12 hrs dark


IN-LIFE DATES: From: April 5, 1989 To: April 18, 1989

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 4320 l glass and stainless steel chambers.
- Method of holding animals in test chamber: cages
- Source and rate of air: 1000 l/min
- Method of conditioning air: Test substance was metered from a piston pump into one or two heated glass evaporator with a temperature of 27-70 degree C. Conditioned air was passed through the evaporator, where it carried the vapor into the exposure chamber.
- Temperature, humidity: monitored every 30 minutes
- Air flow rate: 1000 l/min
- Air change rate: 20 min, 14 air changes per hour
- Treatment of exhaust air: filtration


TEST ATMOSPHERE
- Brief description of analytical method used: GC with flame ionization detection
- Samples taken from breathing zone: yes, 7 times per exposure

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples were taken seven times per exposure period and analyzed with GC-FID. Distribution of test substance was evaluated by sampling five different areas of the exposure chamber.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
- Length of cohabitation: March 27, 1989-April 2, 1989
- Proof of pregnancy: vaginal plug referred to as day 0

Duration of treatment / exposure:

gestation day (GD) 6-15

Frequency of treatment:

6 hrs/day

Duration of test:

GD 18

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 900, 3000, 9000 ppm
Basis: nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
914, 3026, 9107 ppm
Basis: analytical conc.

No. of animals per sex per dose:

30 pregnant females per exposure group

Control animals:

yes

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations: mortality, clinical signs



BODY WEIGHT: Yes
- Time schedule for examinations: GD 0, 6, 9, 12, 15


FOOD CONSUMPTION: Yes

WATER CONSUMPTION: Yes


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 18
- Organs examined: gravid uterus, ovaries, cervix, vagina, abdominal cavities, thoracic cavities, liver, kidneys

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Number of corpora lutea: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: live and dead fetuses

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter were examined for thoracic and abdominal visceral abnormalities
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: [all per litter / half per litter / #? per litter ] / No / No data

Statistics:

Quantitative continuous variables were compared by use of Levene's test for equal variance, analysis of variance, and t-tests with Bonferroni probabilities. Nonparametric data was evaluated using the Kruskal-Wallis test, followed by the Mann-Whitney U test. Indices were compared using Fisher's exact test. 0.05 was used as the criteria for statistical significance.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
There were no significant treatment related effects to body weight, clinical signs, food consumption, weight changes, or organ weights. There was increased water consumption on GD 6-9, 9-12, 6-15, and 15-18 in the 3000 ppm group. There was also increased water consumption in the 900 ppm group on GD 3-6 and 6-9. There was a statistically significant increase in lung color changes in the 9000 ppm group. Four dams also had brown foci. Two dams in the 3000 ppm group had lung color changes as well, and three had dark brown foci.

Effect levels (maternal animals)

1

Key result

Dose descriptor:

NOAEC

Effect level:

900 ppm

Basis for effect level:

other: maternal toxicity

2

Key result

Dose descriptor:

LOAEC

Effect level:

3 000 other: ppm (10560 mg/m3)

Basis for effect level:

other: maternal toxicity

Maternal abnormalities

Key result

Abnormalities:

effects observed, treatment-related

Localisation:

other: Colour changes in lungs

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Gestational parameters were similar between exposure and control groups. There was a statistically significant increase in two skeletal malformations in the 9000 ppm group, bilateral bone island at the first lumbar arch, all intermediate phalanges of the hindlimb unossified. No other dose related abnormalities were noted.

Effect levels (fetuses)

1

Key result

Dose descriptor:

NOAEC

Effect level:

3 000 other: ppm (10560 mg/m3)

Sex:

male/female

Basis for effect level:

skeletal malformations

2

Key result

Dose descriptor:

LOAEC

Effect level:

9 000 other: ppm (31680 mg/m3)

Sex:

male/female

Basis for effect level:

skeletal malformations

Fetal abnormalities

Key result

Abnormalities:

effects observed, treatment-related

Localisation:

skeletal: vertebra

skeletal: hindlimb

Overall developmental toxicity

Key result

Developmental effects observed:

yes

Lowest effective dose / conc.:

9 000 ppm

Treatment related:

yes

Relation to maternal toxicity:

not specified

Dose response relationship:

yes

Relevant for humans:

not specified

Any other information on results incl. tables

Results of Developmental Toxicity Study on Mice

	0.0 ppm	900.0 ppm	3000.0 ppm	9000.0 ppm
No. of dams with lung color change	0	0	2	12
All inter. Phalanges (hindlimb) unossified (litters, %)	76.9	72.0	84.0	100.0
Bone island - first lumbar arch - bilateral  (litters, %)	0.0	0.0	8.0	23.1

Applicant's summary and conclusion

Conclusions:

In mice, the maternal NOAEC was 900 ppm, and the maternal LOAEC was 3000 ppm (10560 mg/m3) based on color changes in the lungs. The developmental NOAEC was 3000 ppm and the LOAEC was 9000 ppm (31680 mg/m3) in mice.

Executive summary:

The purpose of this study was to examine the developmental toxicity of commercial hexane in mice. Groups of 30 pregnant female mice were exposed to concentrations of 0, 900, 3000, or 9000 ppm for 6 hrs/day during gestational days 6 -15. The animals were then sacrificed on GD 18. During the study, the animals were examined for clinical signs, mortality, food and water consumption, and body weights taken. After sacrifice, the internal organs were examined, and the uterus was examined for viable fetuses, number of resorptions, and number of corpora lutea. Fetuses were examined for malformations.

Necropsy revealed color changes in the lungs of females in the 3000 and 9000 ppm groups. Fetuses in from dams in the 9000 ppm group had a statistically significant increase in some skeletal abnormalities. The maternal NOAEC in mice was 900 ppm (3168 mg/m³), and the LOAEC 3000 ppm based on lung color changes. The developmental NOAEC in mice was 3000 ppm (10560 mg/m³) and the LOAEC 9000 ppm (31680 mg/m³) based on skeletal abnormalities.