2,3-dimethylbutane

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration

Type of information:

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

Adequacy of study:

key study

Study period:

1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable without restriction because it closely followed OECD Guideline 475.

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

Cross-reference 1

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration

Type of information:

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

Adequacy of study:

key study

Study period:

1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable without restriction because it closely followed OECD Guideline 475.

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

Reason / purpose for cross-reference:

reference to same study

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

There was a decrease in body weight observed after the last exposure. This reduction is typical for nose-only exposure, and is considered to be due to restraint. There was no statistically significant increase in aberrations in the exposure groups.

Chromosomal Damage in Rat Bone Marrow - Male         

Dose (ppm)	Time Evaluated (hrs)	Cells with Aberrations (%)	Mean Aberrations per Cell per Animal
0	6	0.0	0.000 ± 0.000
0	24	0.0	0.000 ± 0.000
876	6	0.4	0.004 ± 0.009
876	24	0.0	0.000 ± 0.000
3249	6	0.0	0.000 ± 0.000
3249	24	0.4	0.004 ± 0.009
8715	6	0.8	0.008 ± 0.018
8715	24	0.4	0.004 ± 0.009
Positive Control	6	14.4	0.696 ± 0.121

Chromosomal Damage in Rat Bone Marrow - Female

Dose (ppm)	Time Evaluated (hrs)	Cells with Aberrations (%)	Mean Aberrations per Cell per Animal
0	6	0.8	0.008 ± 0.011
0	24	0.0	0.000 ± 0.000
876	6	0.4	0.004 ± 0.009
876	24	0.4	0.004 ± 0.009
3249	6	0.4	0.004 ± 0.009
3249	24	0.0	0.000 ± 0.000
8715	6	0.4	0.004 ± 0.009
8715	24	0.4	0.004 ± 0.009
Positive Control	6	20.8	0.900 ± 0.477

Conclusions:

Interpretation of results: negative

The test substance is not mutagenic.

Executive summary:

This data is being read across from the source study that tested commercial hexane based on analogue read across.

This study determined the effect of inhalation exposure of commercial hexane on rat bone marrow. Groups of 5 male and 5 female rats were exposed to 0, 900, 3000, and 9000 ppm of test substance vapor for 6 hrs/day for 5 days. 0.5 mg/Kg triethylenemelamine was used as a positive control substance. Animals were sacrificed 3 or 21 hrs after exposure, and the bone marrow from their femurs examined for cell aberrations.

There was no statistically significant increase in cell aberrations in any treatment group. The test substance is not mutagenic.

Cross-reference 2

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1994

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)

Deviations:

yes

Remarks:

In order to test substance as a vapor, animals were exposed via nose-only inhalation.

GLP compliance:

yes (incl. QA statement)

Type of assay:

other: cytogenetics assay

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
- Physical state: clear, water white liquid
- Composition of test material, percentage of components: 52.19% n-hexane
- Storage condition of test material: room temperature in the dark

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Sprague Dawley, Inc., Frederick, MD
- Age at study initiation: 6-8 weeks
- Weight at study initiation: 228-266 g males, 153-188 g females
- Assigned to test groups randomly: assigned using body weight randomization program
- Housing: singly in plastic cages, identified by ear tags
- Diet (e.g. ad libitum): certified laboratory rodent chow, ad libitum
- Water (e.g. ad libitum): tap water ad libitum
- Acclimation period: 10 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 72 degree F
- Humidity (%): 40-70
- Photoperiod (hrs dark / hrs light): 12 hrs light/12 hrs dark

Administration / exposure

Route of administration:

inhalation: vapour

Details on exposure:

TYPE OF INHALATION EXPOSURE: nose only


GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 360 ml polycarbonate chamber
- Method of holding animals in test chamber: Polycarbonate tubes were used to restrain the animals. Only the nose of the animals protruded into the chambers. A soft sponge was used as a plunger to hold the animals in place.
- Source and rate of air: filtered outside air
- Method of conditioning air: A Gilson peristaltic pump was used to meter test liquid in sealed resevoirs to vaporization flasks immersed in 57 degree C water. Air was passed through the flasks, then through teflon tubing to the exposure chamber. A calibrated rotameter was used to dilute the air to the appropriate concentration.
- Temperature, humidity, pressure in air chamber: monitored every 30 min.
- Air flow rate: monitored every 30 min.


TEST ATMOSPHERE
- Brief description of analytical method used: GC
- Samples taken from breathing zone: yes

Duration of treatment / exposure:

6 hrs per day

Frequency of treatment:

5 days

Post exposure period:

1 or 19 hrs after end of exposure

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 900, 3000, 9000 ppm (0, 3168, 10560, 31680 mg/m3)
Basis:
nominal conc.

No. of animals per sex per dose:

5 male and 5 female per dose

Control animals:

yes, sham-exposed

Positive control(s):

triethylenemelamine
- Route of administration: intraperitoneal injection
- Doses / concentrations: 0.5 mg/kg

Examinations

Tissues and cell types examined:

bone marrow

Details of tissue and slide preparation:

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):
Colchicine was administered two hours prior to sacrifice to arrest cell division at metaphase. Animals were sacrificed by carbon dioxide asphyxiation. Bone marrow cells were removed from the femur by aspiration into HBSS. Cells were mixed well and kept in an ice bath until all samples were collected. After centrifuging for 10 min, the supernatent was discarded, and the cells resuspended in 5 ml 0.075 M KCl at 37 degree C. After incubating for 10 min, cells were again centrifuged and resuspended in fixative. This was repeated with fresh fixative.

DETAILS OF SLIDE PREPARATION:
Cells were again centrifuged for 10 min, the supernantant decanted, and the cells resuspended in 1 ml of fixative. Two drops were placed on a cold wet glass slide, and allowed to air dry. Three slides were prepared per animal. Slides were stained with 4% Giemsa.

METHOD OF ANALYSIS:
50 metaphase cells containing approx. 40 centromeres were scored if possible.

OTHER:

Evaluation criteria:

In order for the test to be valid, there must be no more than 4% cells demonstrating aberrations in the negative control group. Positive control must be statistically increased over untreated controls (p<=0.05, Fisher's exact test). A positive result is a percentage of cells with aberrations which was statistically increased over untreated controls (p<=0.05, Fisher's exact test).

Statistics:

Fisher's exact test was used to determine statistical significance. Cochran-Armitage test was used to test dose-responsiveness.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

There was a decrease in body weight observed after the last exposure. This reduction is typical for nose-only exposure, and is considered to be due to restraint. There was no statistically significant increase in aberrations in the exposure groups.

Any other information on results incl. tables

Chromosomal Damage in Rat Bone Marrow - Male         

Dose (ppm)	Time Evaluated (hrs)	Cells with Aberrations (%)	Mean Aberrations per Cell per Animal
0	6	0.0	0.000 ± 0.000
0	24	0.0	0.000 ± 0.000
876	6	0.4	0.004 ± 0.009
876	24	0.0	0.000 ± 0.000
3249	6	0.0	0.000 ± 0.000
3249	24	0.4	0.004 ± 0.009
8715	6	0.8	0.008 ± 0.018
8715	24	0.4	0.004 ± 0.009
Positive Control	6	14.4	0.696 ± 0.121

Chromosomal Damage in Rat Bone Marrow - Female

Dose (ppm)	Time Evaluated (hrs)	Cells with Aberrations (%)	Mean Aberrations per Cell per Animal
0	6	0.8	0.008 ± 0.011
0	24	0.0	0.000 ± 0.000
876	6	0.4	0.004 ± 0.009
876	24	0.4	0.004 ± 0.009
3249	6	0.4	0.004 ± 0.009
3249	24	0.0	0.000 ± 0.000
8715	6	0.4	0.004 ± 0.009
8715	24	0.4	0.004 ± 0.009
Positive Control	6	20.8	0.900 ± 0.477

Applicant's summary and conclusion

Conclusions:

Interpretation of results: negative

The test substance is not mutagenic.

Executive summary:

This study determined the effect of inhalation exposure of commercial hexane on rat bone marrow. Groups of 5 male and 5 female rats were exposed to 0, 900, 3000, and 9000 ppm of test substance vapor for 6 hrs/day for 5 days. 0.5 mg/Kg triethylenemelamine was used as a positive control substance. Animals were sacrificed 3 or 21 hrs after exposure, and the bone marrow from their femurs examined for cell aberrations.

There was no statistically significant increase in cell aberrations in any treatment group. The test substance is not mutagenic.