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Toxicological information

Genetic toxicity: in vivo

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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other: Guideline study, available as unpublished report, no restrictions, fully adequate for assessment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:
EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.5395 (In Vivo Mammalian Cytogenetics Tests: Erythrocyte Micronucleus Assay)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): pyrolysis C5s
- Substance type: complex mixture of hydrocarbons
- Physical state: clear, colourless liquid
- Lot/batch No.: QA1001A100
- Expiration date of the lot/batch: Not provided by Sponsor
- Stability under test conditions: The 3 major components analysed were shown to be stable for the duration of the study
- Storage condition of test material: approximately 10°C in the dark under nitrogen
- The sample tested consisted of isoprene (18%), cis- and trans-pentadiene-1, 3 (16%), cyclopentadiene + dicyclopentadiene (14%), n-pentane (10%), cyclopentene (7%), 2-methy1-2-butene (3%) and cyclopentane (1%)
- The balance consists of other hydrocarbons with similar boiling point (primarily C5s)

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River UK Limited, Margate, Kent, UK
- Age at study initiation: Not reported
- Weight at study initiation: 29.4-35.2 g
- Assigned to test groups randomly: yes
- Housing: Group housed
- Diet: pelleted expanded rat and mouse No.1 maintenance diet (SQC grade obtained from Special Diets Services Ltd, Witham, Essex, UK) ad libitum (except during exposures)
- Water: tap water ad libitum (except during exposures)
- Acclimation period: Minimum of 6 days

ENVIRONMENTAL CONDITIONS
- Temperature: 21?2°C
- Humidity: 55?10%
- Air changes (per hr): Not reported
- Photoperiod: 12hrs dark / 12hrs light

IN-LIFE DATES: From: 12 June 2002 To: 13 June 2002

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: Glass vapour generators
- Compressed air was used to generate atmospheres for both negative control and test chemical exposed groups. Gas chromatography was used to measure the concentrations of Pyrolysis C5s in the test atmospheres. Negative control animals were exposed using compressed air.
Duration of treatment / exposure:
2 days
Frequency of treatment:
Daily (two 6-hour exposures on consecutive days)
Post exposure period:
24 hours after 2nd exposure period
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
40, 125 and 500 ppm
Basis:
other: target concentration
Remarks:
Doses / Concentrations:
44, 130 and 490 ppm
Basis:
analytical conc.
No. of animals per sex per dose:
7 control and treated
5 positive control
Control animals:
yes, sham-exposed
Positive control(s):
mitomycin C
- Route of administration: oral gavage
- Doses / concentrations: 12 mg/kg

Examinations

Tissues and cell types examined:
micronuclei (MN) in polychromatic erythrocytes (PCE)
Evaluation criteria:
One smear from each animal was examined for the presence of micronuclei in 2000 immature erythrocytes. The proportion of immature erythrocytes was assessed by examination of at least 1000 erythrocytes from each animal and the incidence of micronucleated mature erythrocytes was recorded. A positive response is normally indicated by a statistically significant dose-related increase in the incidence of micronucleated immature erythrocytes for the treatment group compared with the concurrent control group (P<0.01); individual and/or group mean values should exceed the laboratory historical control range (Morrison and Ashby 1995). A negative result is indicated where individual and group mean incidences of micronucleated immature erythrocytes for the group treated with the test substance are not significantly greater than incidences for the concurrent control group (P>0.01) and where these values fair within the historical control range. An equivocal response is obtained when the results do not meet the criteria specified for a positive or negative response. Bone marrow cell toxicity (or depression) is normally indicated by a substantial and statistically significant dose-related decrease in the proportion of immature erythrocytes (P<0.01).
Statistics:
Incidences of micronucleated immature erythrocytes: Linear-by-Linear association test and exact one tailed pairwise Permutation test.
Proportion of immature erythrocytes: exact versions of Wilcoxon's sum of ranks test and Jonckheere's test for trend.

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Toxicity:
no effects
Negative controls valid:
yes
Positive controls valid:
yes

Any other information on results incl. tables

No clinical signs or mortalities were observed for any animal treated with Pyrolysis C5s and killed 24 hours after two 6-hour periods of whole body inhalation exposure, compared to negative control values (P>0.01 in each case). No statistically significant increases in the frequency of micronucleated immature erythrocytes and no substantial decreases in the proportion of immature erythrocytes were recorded.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
Pyrolysis C5s did not show any evidence of causing chromosome damage or bone marrow cell toxicity when administered by whole body inhalation exposure in an in vivo mouse micronucleus test.
Executive summary:

Groups of 7 male CD-1 mice were exposed to Pyrolysis C5s (CAS 68476 -55 -1) for two 6-hour whole body exposure periods, on consecutive days, at target concentrations of 40, 150 and 500 ppm. Negative control animals were exposed using compressed air. A positive control group (5 animals) were dosed once only by oral gavage with mitomycin C at 12 mg/kg. All animals were sacrificed approximately 24 hours after the second exposure period (24 hours after the oral dose for the positive control group) and bone marrow smears prepared. Smears were examined to evaluate the incidence of micronuclei in 2000 polychromatic erythrocytes (PCE) per animal. The proportion of PCE was assessed by examination of at least 1000 erythrocytes.

No statistically significant increase in the incidence of micronucleated PCE were observed in the Pyrolysis C5s exposed animals compared with the negative control values. The positive control treatment induced a significant increase.

The results demonstrate that Pyrolysis C5s is not clastogenic toward mammalian cells in vivo.