Hydrocarbons, C4, steam-cracker distillate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP compliant, guideline study, available as unpublished report, no restrictions, fully adequate for assessment

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5395 (In Vivo Mammalian Cytogenetics Tests: Erythrocyte Micronucleus Assay)

Deviations:

no

Principles of method if other than guideline:

none

GLP compliance:

yes (incl. QA statement)

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Hydrocarbons, C4, ethylene-manuf.-by-product

EC Number:

270-691-3

EC Name:

Hydrocarbons, C4, ethylene-manuf.-by-product

Cas Number:

68476-52-8

IUPAC Name:

Hydrocarbons, C4, ethylene-manuf.-by-product

Constituent 2

Reference substance name:

C4 crude butadiene (low 1,3-butadiene content)

IUPAC Name:

C4 crude butadiene (low 1,3-butadiene content)

Constituent 3

Reference substance name:

25167-67-3, 64742-83-2, 68187-60-0, 68476- 44-8, 68955-28-2 and 68956-54-7

IUPAC Name:

25167-67-3, 64742-83-2, 68187-60-0, 68476- 44-8, 68955-28-2 and 68956-54-7

Details on test material:

- Name of test material (as cited in study report): C4 crude butadiene (low 1,3-butadiene content)
- Physical state: liquid
- Supplier: Texas Petrochemicals, LP
- Composition of test material, percentage of components: 10% 1,3-butadiene, 4% isobutane, 4% n-butane, 29% trans-2-butene, 11% isobutylene, 12% cis-2-butene
- Lot/batch No.: 268193
- Storage condition of test material: supplied in cylinders, stored at approximately 40°F prior to use and at approximately 60°F during use.

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Portage, Michigan, USA
- Origin: The B6C3F1 strain originated from a cross between female C57BL/6NCrlBR and male C3H/HeNCrlBR mice (Charles River Catalog, 2000).
- Age at study initiation: 9 weeks
- Weight at study initiation: 23.3-28.2 g (males), 19.7-23.0 g (females)
- Assigned to test groups randomly: yes, by a stratified randomization procedure using body weights.
- Housing: singly in stainless steel cages
- Diet: LabDiet® Certified Rodent Diet #5002 (PMI Nutrition International, St. Louis, Missouri) in pelleted form ad libitum (except during exposure)
- Water: municipal water ad libitum (except during exposure)
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature: 18-26°C
- Humidity: 40-70%
- Air changes: 12-15 per hr
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 27 November 2000 To: 29 November 2000

Administration / exposure

Route of administration:

inhalation: vapour

Vehicle:

- Vehicle(s)/solvent(s) used: air

Details on exposure:

TYPE OF INHALATION EXPOSURE: whole body

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and glass Rochester-style 2m3 exposure chambers (1.3 m x 1.2 m x 1.2 m with a pyramidal top and bottom).
- Method of holding animals in test chamber: Individually in the chamber
- System of generation: The test material flowed through a micrometer and a 25 psi check valve where partial vaporization began. The test material stream in a liquid and gas phase mixture flowed through a Brazed Plate Heat Exchanger where the test material completed vaporization. Test material vapour was then passed through a regulator and metered to the exposure chambers. The vapour was diluted and mixed with supply air and compressed air to achieve the target chamber airflow and desired concentration.
- Temperature, humidity in air chamber: 18.0-23.4°C, 44.2 to 77.0%
- Air flow rate: approx 450 L/min

TEST ATMOSPHERE
- Brief description of analytical method used: Chamber concentrations were determined using area counts, then using the standard curve and response factor to determine the concentration in mg/L. Chamber mean total olefins* (*referring to all components in the crude stream that were analyzed by gas chromatography) concentrations were less than the Level of Quantitation, 0.520, 9.86, and 17.8 mg/L for target concentrations of 0, 0.5, 10.0, and 20.0 mg/L, respectively. Ratios of the isobutane, trans-2-butene, and 1,3-butadiene at all concentration levels were proportionate to the expected content based on the analytical characterization of the test material.
- Samples taken from breathing zone: yes

Duration of treatment / exposure:

2 consecutive days

Frequency of treatment:

4 hours/day

Post exposure period:

24 hours after second exposure (test animals), 24 hours after oral dose (positive controls)

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 0.5, 10.0, and 20.0 mg/L
Basis:
other: target concentration

No. of animals per sex per dose:

6

Control animals:

yes, sham-exposed

Positive control(s):

cyclophosphamide
- Route of administration: oral gavage
- Doses / concentrations: single dose of 120 mg/kg

Examinations

Tissues and cell types examined:

erythrocytes from femoral bone marrow

Details of tissue and slide preparation:

Wedge smears were prepared on microscope slides using small portions of the cell suspension. The slides were allowed to air dry and stained with Wright- Giemsa using an automatic slide stainer.

Evaluation criteria:

see below

Statistics:

The raw data on the counts of MN-PCE for each animal were first transformed by adding 1 to each count and then taking the natural log of the adjusted number. The transformed MN-PCE data and the data on % PCE were analyzed separately by a two-way analysis of variance. The sex-by-dose interaction in the two-way analysis was reviewed and if significant, a one-way analysis was performed for each sex. Pairwise comparisons of treated vs. control groups were done, if the dose effect was significant, by Dunnett’s t-test, one-sided (upper) for MNPCE and two-sided for % PCE. Linear dose-related
trend tests were performed only if any of the pairwise comparisons yielded significant differences. The alpha level at which all tests were conducted was 0.05.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

positive

Toxicity:

no effects

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

see below

Any other information on results incl. tables

There was no effect on the body weight of the animals and no indications of toxicity were observed during the daily observations of the in-life portion of the study. Statistically significant increases in the frequencies of MN-PCE in both sexes of all groups treated with the test material were observed as compared to the negative controls. Although statistical analyses indicated a significant dose response, the difference in MN-PCE incidence at the high- (20 mg/L) and low- (0.5 mg/L) dose was minimal. The positive control treatment induced a significant increase in the frequency of MN-PCE. The mean proportion of PCE among the erythrocytes (200/animal) in the bone marrow was not affected following exposure to the test material while the positive control treatment significantly reduced this value.

Applicant's summary and conclusion

Conclusions:

Interpretation of results: positive
C4 Crude Butadiene (Low 1,3-Butadiene Content) was positive in the mouse bone marrow micronucleus test.

Executive summary:

C4 Crude Butadiene (Low 1,3-Butadiene Content) was tested in a mouse bone-marrow micronucleus assay. C3H/HeNCrlBR mice were exposed to 20mg/L (20,000 mg/m3)for 4h/day for 2 days. A positive result was obtained.