Registration Dossier

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting 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other: GLP compliant, Guideline study, available as unpublished report, no restrictions, fully adequate for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report Date:
2004

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.5395 (In Vivo Mammalian Cytogenetics Tests: Erythrocyte Micronucleus Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)
Deviations:
no
GLP compliance:
yes
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Dicyclopentadiene/Codimer Concentrate
- Synonyms: DCPD/Codimer Concentrate, DCP97, H-25430
- CA Index name: Naphtha (petroleum), light steam-cracked, debenzenized, C8-16-cycloalkadiene concentrate
- Lot number: 121302
- Substance type: a distillate from a C8+ fraction of thermally processed pyrolysis gasoline obtained from ethylene production
- Physical state: colourless liquid
- Purity: Not applicable (the test substance was within specifications and the occurrence and distribution of isomers was as expected)
- Stability under test conditions: stable at room temperature below 70°F, protected from light and air
- Composition of test material, percentage of components:
29.175 wt % endo- and exo-DCPD
18.726 wt % C4-MCPD and C5-MCPD codimers
13.210 wt % MCPD dimer
12.903 wt % CPD-MCPD codimer
8.129 wt % C8 aliphatic and aromatic hydrocarbons
7.144 wt % C4-CPD and C5-CPD codimers
3.625 wt % MCPD-C7 dimer
2.771 wt % Tetrahydroindene
1.917 wt % Trimers
0.927 wt % C7 cyclic hydrocarbon
0.697 wt % C5 acyclic hydrocarbon dimer
0.634 wt % MCPD monomer
0.078 wt % CPD monomer
0.063 wt % C6 acyclic hydrocarbons

Test animals

Species:
mouse
Strain:
other: Crl:CD-1®(ICR)BR
Sex:
male/female
Details on test animals and environmental conditions:
- Source: Charles River Breeding Laboratories, Raleigh, North Carolina, USA (males); Charles River Canada, St. Constant, Canada (females)
- Age at study initiation: approximately 8 weeks
- Weight at study initiation: approximately 28.7-35.6 g (males), 21.6-26.8 g (females)
- Assigned to test groups randomly: yes (by computerised stratified randomisation)
- Fasting period before study: No
- Housing: 3 same sex per cage in stainless steel, wire-mesh suspended cages.
- Diet: Certified Rodent LabDiet® 5002 (PMI Nutrition International, Inc.,) ad libitum
- Water: tap water ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature: 22±3ºC
- Humidity: 30-70%
- Air changes (per hr): Not reported
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: Not reported

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Vehicle(s)/solvent(s) used: corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
- The dosing solutions were prepared daily in corn oil
- A correction factor was not used for preparation of the dosing solutions
- Prior to dosing, aliquots were taken from each DCPD/Codimer Concentrate dosing preparation, and the homogeneity/concentration and stability of the vehicle control, high, intermediate, and low test substance dosing preparations were confirmed
Duration of treatment / exposure:
Two doses at an approximate 24-hour interval
Frequency of treatment:
Twice at an approximate 24-hour interval
Post exposure period:
24 hours after second dose
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 437.5, 875, or 1750 mg/kg body weight
Basis:
other: nominal in corn oil
No. of animals per sex per dose:
5/sex/group (0, 437.5, or 875 mg/kg body weight and positive controls), 7/sex/group (1750 mg/kg body weight).
Control animals:
yes, concurrent vehicle
Positive control(s):
5/sex (cyclophosphamide, 30 mg/kg once by oral intubation)

Examinations

Tissues and cell types examined:
Bone marrow erythrocytes
Details of tissue and slide preparation:
The mice were killed approximately 24 hours after administration of the second dose and smears of bone marrow erythrocytes were prepared and stained.
Evaluation criteria:
2000 PCEs per animal were scored for the presence of micronuclei. The proportion of PCEs among 1000 total erythrocytes was determined for each animal and expressed as the PCE/NCE ratio.
Statistics:
Total polychromatic erythrocytes (PCEs), micronucleated polychromatic erythrocytes, normochromatic erythrocytes (NCEs) were compared to the
control using Dunnett’s and Dunn’s test (p < 0.05).

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
valid
Positive controls validity:
valid

Any other information on results incl. tables

Clinical signs observed in male and female animals at 1750 mg/kg included ataxia, lethargy, and hyperactivity. In addition, male animals exhibited spasms, and female animals exhibited ruffled fur, prostration, and hyperreactivity. No clinical signs of toxicity were observed in male or female animals at 875 or 427.5 mg/kg.

An 18% and 14% decrease in terminal body weight was observed for the high dose males and females, respectively, as compared with their initial body weights The terminal body weight loss for the high dose groups, as compared with the controls, was 18% for males and 13% for females. Both observed body weight reductions are considered test substance-related signs of systemic toxicity. The body weight loss in males is also considered biologically significant.

No statistically significant or biologically relevant effects on micronuclei frequencies were observed in the bone marrow cells in any dose group treated with DCPD/Codimer Concentrate. Although not statistically significant, a depression of approximately 30% in the PCE/NCE ratio was seen at 1750 mg/kg in females

The vehicle and positive control groups exhibited a response consistent with the laboratory’s historical control data. The positive control, cyclophosphamide, induced a significant increase in the frequency of micronucleated PCEs (p < 0.05).

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
DCPD/Codimer Concentrate was considered negative in this in vivo assay.
Executive summary:

DCPD/Codimer Concentrate did not induce a statistically significant increase in micronucleated polychromatic erythrocytes in male or female mouse bone marrow when evaluated after two administrations, approximately 24 hours apart. The highest dose administered on the study (1750 mg/kg body weight) gave clear evidence of clinical signs (both sexes) and bone marrow toxicity (decreased PCE/NCE ratio) in females. Based on these findings, the test substance was considered negative in this in vivo assay.