Distillates (petroleum), sweetened middle

Genetic toxicity: in vivo

Administrative data

Endpoint:

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

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

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

Adequacy of study:

key study

Study period:

1984-05-16 to 1985-05-16

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable with restriction because it is an acceptable and a well-documented study report.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)

GLP compliance:

yes

Type of assay:

chromosome aberration assay

Test material

Test material information

Constituent 1

Reference substance name:

Straight run middle distillate (CAS# 64741-44-2)

IUPAC Name:

Straight run middle distillate (CAS# 64741-44-2)

Details on test material:

- Name of test material (as cited in study report): API 83-11 (Microbiological Associates, Inc. code # T2419)
- Substance type: Gas oil
- Physical state: Liquid
- Analytical purity: Not reported
- Purity test date: Not reported
- Stability under test conditions: Not determined
- Storage condition of test material: In dark at room temperature
- Other: Clear, colourless, non viscous liquid

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratory (Kingston, NY)
- Age at study initiation: 6-8 weeks
- Weight at study initiation: Male - 235 to 289 grams; Female - 160 to 199 grams
- Assigned to test groups randomly: Yes
- Fasting period before study: No
- Housing: Three to four per cage during quarantine and individually thereafter in plastic autoclavable cages with wire lids
- Diet (e.g. ad libitum): Certified laboratory rodent chow ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 10-14 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 74 ± 6° F
- Humidity (%): 50 ± 20%
- Air changes (per hr): Not reported
- Photoperiod (hrs dark / hrs light): 12 hrs dark/12 hrs light


IN-LIFE DATES: Not reported

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

- Vehicle(s)/solvent(s) used: corn oil
- Justification for choice of solvent/vehicle: Not reported
- Concentration of test material in vehicle: Not reported
- Lot/batch no. (if required): B1121
- Purity: Not reported

Duration of treatment / exposure:

6, 24, or 48 hours

Frequency of treatment:

single intraperitoneal injection

Post exposure period:

2 to 4 hours post colchicine injection to arrest cells in metaphase

Doses / concentrations

Remarks:

Doses / Concentrations:
0.3, 1.0, 3.0 g/Kg
Basis:
nominal conc.

No. of animals per sex per dose:

5 per sex per dose

Control animals:

yes

Positive control(s):

triethylenemelamine
- Justification for choice of positive control(s): Not reported
- Route of administration: Intraperitoneal injection
- Doses / concentrations: 0.5 mg/Kg

Examinations

Tissues and cell types examined:

Bone marrow cells extracted from the femur

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION: A confirmatory test was conducted by exposing 4 male and female rats to 3.0 g/Kg API 83-11 for 24 hours. Based on mortality observed in 1 of the 4 male rats, 0.3, 1.0, and 3.0 g/Kg were selected for the study.


TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):
Test material and corn oil vehicle control - 6, 24, or 48 hours post intraperitoneal injection
Positive control - 24 hours post intraperitoneal injection
Colchicine injections (1 mg/Kg) were administered 2 to 4 hours prior to sacrifice to arrest dividing cells in metaphase


DETAILS OF SLIDE PREPARATION:
Immediately following sacrifice, the femur was exposed, and the bone marrow aspirated into a syringe containing HBSS. Bone marrow cells were thereafter tranferred into a capped centrifuge tube containing 5 mL cold HBSS, mixed well, and maintained in an ice bath. Post-centrifugation at 100g for 10 minutes, cells were resuspended in 5 mL of 37°C 0.075 M KCl and incubated at 37°C for another 10 minutes. Cells were subsequently suspended in 5 mL Carnoy's fixative for 30 minutes, centrifuged followed by discarding the supernatant, and resuspended in fresh fixative for overnight storage at 4°C. Post overnight storage, cells were centrifuged at 100g for 10 minutes and then suspended to opalescence in 1 mL fresh fixative after the supernatant was discarded. Two to three drops of this cell suspension were then dropped onto the surface of a cold wet glass slide and allowed to air dry. At least three slides were prepared for each animal and the dry slides were stained with 4% Giesma stain and permanently mounted.


METHOD OF ANALYSIS:
Stained slides were coded and scored without regard to the treatment group. A minimum of 50 metaphase cells from each animal were examined and scored for chromatid and chromosome gaps and breaks, fragments, structural arrangements, and ploidy. The XY co-ordinates of each cell with chromosome aberrations was recorded using a calibrated microscope stage.

Evaluation criteria:

The test material would be considered to induce a positive response if the percentage of cells with aberrations in any treatment group was significantly increased (p ≤ 0.05) relative to the vehicle control (corn oil) using Chi-Square analysis and if the number of aberrations per cell was also significantly increased (p ≤ 0.05) relative to the vehicle control using the t-test statistics. Additionally, the percentage of cells in the vehicle control group exhibiting aberrations of any type (except gaps) should not exceed 4% and the percentage of cells in the positive control group exhibiting aberrations must be significantly higher (p ≤ 0.05) than the vehicle control group.

Statistics:

Chi-Square analysis using a 2 x 2 contingency table was used to ascertain significant differences between the number of cells with aberrations in the treatment and control groups. The t-test was used to compare pair-wise the number of aberrations per cell of each treatment group with that of the vehicle control.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range: 3.0 g/Kg single intraperitoneal injection
- Clinical signs of toxicity in test animals: mortality observed in 1 of 4 male rats
- Evidence of cytotoxicity in tissue analyzed: Not reported
- Rationale for exposure: Not reported
- Harvest times: 24 hours


RESULTS OF DEFINITIVE STUDY
- Types of structural aberrations for significant dose levels (for Cytogenetic or SCE assay): a small number of gaps and breaks were observed at all dose levels tested
- Statistical evaluation: At 24 hours, the percentage of chromosome aberrations was 0 (vehicle control); 0.2 (API 83-11 - 3.0 g/Kg); 0.2 (API 83-11 - 1.0 g/Kg); 0 (API 83-11 - 0.3 g/Kg); and 35.4 (positive control). The number of aberrations per cell at 24 hours was 0 (vehicle control); 0.004 (API 83-11 - 3.0 g/Kg); 0.002 (API 83-11 - 1.0 g/Kg); 0 (API 83-11 - 0.3 g/Kg); and 2.358 (positive control)

Any other information on results incl. tables

A 4% body weight loss was observed in male rats 24 hours post exposure to 3.0 g/Kg and a 2% weight loss in females 48 hours post exposure to 3.0 g/Kg API 83 -11. No mortality or signs of clinical toxicity were observed at any dose level in either sex through the study period.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Under the conditions of the study, Straight run middle distillate did not induce chromosome aberrations in bone marrow cells of male or female rats.

Executive summary:

Justification for Read Across

Compositional and physico-chemical data show that Other Gas Oils are very similar to Straight-Run Gas Oils. It is considered appropriate, therefore, to read across from the SRGO data to Other Gas Oils.

In a bone marrow chromosome aberration assay, 5 Sprague-Dawley rats/sex/dose were treated intraperitoneally with Straight run middle distillate at doses of 0, 0.3, 1.0, or 3.0 g/kg bw. Bone marrow cells were harvested at 6, 24, and 48 hours post-treatment. The vehicle was corn oil.

 

There were no signs of toxicity during the study. The positive control (Triethylenemelamine) induced the appropriate response. There was no significant increase in the frequency of chromosome aberrations in bone marrow after any treatment time.

This study received a Klimisch score of 2 and is classified as reliable with restriction because it is an acceptable and a well-documented study report.