Ethylbenzene

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

Study period:

2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study was performned according to international guidelines, i.e., OECD No. 474 and EC Directive 2000/32, B. 12, and was conducted in compliance with the OECD Prineiples of Good Laboratory Practice and the GLP Principles of the German "Chemikaliengesetz".

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:

publication

Title:

In vivo micronucleus test in mice with 1-phenylethanol

Author:

Engelhardt G.

Year:

2006

Bibliographic source:

Arch. Toxicol. 80:868-872

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Principles of method if other than guideline:

No information available

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

1445-91-6

Cas Number:

1445-91-6

IUPAC Name:

1445-91-6

Constituent 2

Reference substance name:

1-phenylethanol

EC Number:

202-707-1

EC Name:

1-phenylethanol

Cas Number:

98-85-1

IUPAC Name:

1-phenylethanol

Details on test material:

other TS: 1-phenyl ethanol 98.2% pure (metabolite of ethylbenzene)

Test animals

Species:

mouse

Strain:

NMRI

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Deutschland GmbH
- Age at study initiation: 5-8 weeks
- Weight at study initiation: Mean weight 29 grams
- Assigned to test groups randomly: not specified
- Fasting period before study: not specified
- Housing: not specified
- Diet (e.g. ad libitum): not specified
- Water (e.g. ad libitum): not specified
- Acclimation period: not specified

ENVIRONMENTAL CONDITIONS
- Temperature (°C): not specified
- Humidity (%): not specified
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): not specified

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: [olive oil]
- Justification for choice of solvent/vehicle: recommended
- Concentration of test material in vehicle: not specified
- Amount of vehicle (gavage): 10 ml/kg
- Lot/batch no. (if required): not specified
- Purity: not specified

Details on exposure:

not specified

Duration of treatment / exposure:

24 and 48 hours

Frequency of treatment:

single

Post exposure period:

not applicable

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0 mg/kg
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
187.5 mg/kg
Basis:
nominal conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
375 mg/kg
Basis:
nominal conc.

Doses / concentrations 4

Remarks:

Doses / Concentrations:
750 mg/kg
Basis:
nominal conc.

No. of animals per sex per dose:

5 males/test and control groups

Control animals:

yes, concurrent vehicle

Positive control(s):

cyclophosphamide; vincristine
- Justification for choice of positive control(s): recommended
- Route of administration: as per guidelines
- Doses / concentrations: 20 mg cyclophosphamide in 10 ml solution; 0.15 mg vincristine in 10 ml solution

Examinations

Tissues and cell types examined:

Bone marrow was taken from the femora and slides prepared using standard procedures. 2000 polychromatic erythrocytes (PCE's) from each animal were evaluated.

Details of tissue and slide preparation:

not specified

Evaluation criteria:

A finding is considered positive if the following criteria are met. Significant and dose related increase in the number of PCE's containing micronuclei. The number of PCE's has to exceed both the concurrent negative control and the highest value of the historical control range

Statistics:

To determine if there are significant differences between treated and control groups in the micronucleus rate in PCE's the asymptotic U-test according to Mann-Whitney (modified rank test according to Wilcoxon). The relative frequencies of cells containing micronuclei of each animal was used as a criterion for rank determinations in the U-test

Results and discussion

Test results

Sex:

male

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

MORTALITY: There were no treatment related deaths.

CLINICAL SIGNS:
- 750 mg/kg: Overt signs of toxicity including narcosis, staggering and abdominal position were observed at the top dose level in the first 2 hours after dosing. All the clinical signs were disappeared by the following day.
- 375 mg/kg: All mice were staggering during the first 2 hours following dosing, by 4 hours all the clinical signs were disappeared .
- 187.5 mg/kg: No signs of intoxication.

PCE/NCE RATIO: The number of normochromatic erythrocytes did not differ significantly between the control group or any of the treatment groups at either sacrifice interval.

GENOTOXIC EFFECTS: There was no treatment related increase in PCE's with micronuclei compared to the controls at either 24 or 48 hours sacrifice times. The incidence at 24 hours was 1.7%, 1.8% and 0.8% for low, mid and high dose respectively compared to 1.4% in the vehicle control group. At 48 hours in vehicle controls 1% of PCE's contained micronuclei compared to 1.8% in the top dose group.

The positive controls showed an appropriate increase in in PCE's. Cyclophosphamide (clastogenicity control) had an incidence of 15.5%, mostly micronuclei. Vincristine (aneugenicity control) had an incidence of 60.4% of shich 14.4% was attributable to large micronuclei.

The values obtained in the treated groups were all within concurrent vehicle control and historical control ranges.

A slight inhibition of erythropoiesis was detected at 750 mg/kg after a sacrifice intervalof 48 hours

Any other information on results incl. tables

None

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
1-phenyl ethanol, a metabolite of ethylbenzene, administered to mice at dose levels up to 750 mg/kg/day did not increase the rate of development of micronuclei in polychromatic erythrocytes. At this dose level there were overt clinical signs of toxicity.

Executive summary:

In this micronucleus assay, groups of NMRI mice (5 males/group) were orally administered (by gavage) 1-phenyl ethanol (98.2% pure, metabolite of ethylbenzene) (single administration) at doses of 0, 187.5, 375 and 750 mg/kg and sacrificed 24 and 48 hours post administration (high dose and control only). The vehicle control group received olive oil, only. The study was conducted according to OECD TG 475. Another group of mice received the positive controls cyclophosphamide and vincristine

 

Animals were observed for clinical signs of toxicity and bone marrow was taken from the femora and slides prepared using standard procedures. 2000 polychromatic erythrocytes (PCE's) from each animal were evaluated.

 

There were no treatment related deaths. In the 750 mg/kg group, overt signs of toxicity including narcosis, staggering and abdominal position were observed in the first 2 hours after dosing. All mice were symptomless by the following day. The number of normochromatic erythrocytes did not differ significantly between the control group or any of the treatment groups at either sacrifice interval. A slight inhibition of erythropoiesis was detected at 750 mg/kg after a sacrifice interval of 48 hours.

 

The positive controls showed an appropriate increase in in PCE's. Cyclophosphamide (clastogenicity control) had an incidence of 15.5%, mostly micronuclei. Vincristine (aneugenicity control) had an incidence of 60.4% of which 14.4% was attributable to large micronuclei.

The values obtained in the treated groups were all within concurrent vehicle control and historical control ranges.

 

In conclusion, 1-phenyl ethanol, a metabolite of ethylbenzene, administered to mice at dose levels up to 750 mg/kg/day did not increase the rate of development of micronuclei in polychromatic erythrocytes and at this dose level there were overt clinical signs of toxicity.