Chloroethane

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

1994

Reference 2

Reference Type:

secondary source

Title:

Chloroethane CAS: 75-00-3

Author:

OECD SIDS

Year:

2006

Bibliographic source:

SIDS Initial Assessment Report for SIAM 22

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

GLP compliance:

yes

Type of assay:

mammalian erythrocyte micronucleus test

Test material

Test material information

Constituent 1

Reference substance name:

Chloroethane

EC Number:

200-830-5

EC Name:

Chloroethane

Cas Number:

75-00-3

Molecular formula:

C2H5Cl

IUPAC Name:

chloroethane

Details on test material:

- Name of test material (as cited in study report): chloroethane
- Physical state: gaseous
- Analytical purity: > 99% (Elf Atochem SA, Paris La Défense, France)

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Wiga, Germany
- Weight at study initiation: 20-24 g for males and 17-20 g for females
- Assigned to test groups randomly: yes, under following basis: group weights differed from the mean by no more than 5%
- Housing: in groups of no more than three animals of the same sex in stainless steel cages
- Diet: ad libitum Special Services Ltd, RM1.(E).SQC. pellets
- Water: ad libitum tap water



ENVIRONMENTAL CONDITIONS
- Temperature (°C): 15-25
- Humidity (%): 40-50
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation: gas

Details on exposure:

TYPE OF INHALATION EXPOSURE: nose only in a continuous flow system

TEST ATMOSPHERE
- Brief description of analytical method used: samples taken continuously and recorded half-hourly using an infrared spectrophotometer

Duration of treatment / exposure:

6 h/day

Frequency of treatment:

3 consecutive days

Post exposure period:

no

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

25 000 ppm (nominal)

Remarks:

corresponding to 65961 mg/m³

Doses / concentrations 2

Dose / conc.:

25 071 ppm (analytical)

Remarks:

corresponding to 66148 mg/m³

No. of animals per sex per dose:

5

Control animals:

yes, sham-exposed

Positive control(s):

cyclophosphamide (in distilled water)
- Route of administration: oral
- Doses / concentrations: 80 mg/kg (24 h prior to sacrifice)

Examinations

Tissues and cell types examined:

bone marrow cells (erythrocytes) from both femurs

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION:
An initial range finding study with 19000 ppm chloroethane was conducted using groups of male and female mice to determine mortality. All animals survived. In the main study, the dose was therefore increased to 25000 ppm which represents approximately 66% of the flammability limit and the highest dose which could be safely administered.

DETAILS OF SLIDE PREPARATION:
Cells were pelletted by centrifugation (1250xg for 2-3 min) and smears prepared on microscope slides. Preparations were stained using a modification of the method of Gollapudi and Kamra (1979). Following fixation for 5 min in methanol, slides were rinsed in water and stained for 10 min in filtered Giemsa stain diluted 1:6 in water. When dry, slides were cleared in xylene and mounted.

METHOD OF ANALYSIS:
For each animal scored, at least 1000 polychromatic (PCE) and normochromatic (NCE) erythrocytes were analyzed to obtain a PCE/NCE ratio. At least 2000 PCE per animal were scored for micronuclei. The PCE/NCE ratio for each sex and the mean per treatment group were calculated as a potential indicator of bone marrow toxicity. The sex and group mean micronucleated PCE/1000 PCE were also calculated. The PCE/NCE ratios and frequencies of micronucleated PCE in vehicle control animals were compared with historical control ranges.

Statistics:

For each animal scored, at least 1000 polychromatic (PCE) and normochromatic (NCE) erythrocytes were analyzed to obtain a PCE/NCE ratio. At least 2000 PCE per animal were scored for micronuclei. The PCE/NCE ratio for each sex and the mean per treatment group were calculated as a potential indicator of bone marrow toxicity. The sex and group mean micronucleated PCE/1000 PCE were also calculated. The PCE/NCE ratios and frequencies of micronucleated PCE in vehicle control animals were compared with historical control ranges. For each group, inter individual variation in the numbers of micronucleated PCE was estimated by means of a heterogeneity chi square test. The numbers of micronucleated PCE in each treated group were then compared with the numbers in vehicle control groups using a 2 x 2 contingency table to determine X2. Probability values of p <= 0.05 were accepted as significant. The statistical methods were according to Lovell et al. (1989).

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range: 19124 ppm (mean of 3 days exposure)
- Clinical signs of toxicity in test animals: no deaths were observed
- Evidence of cytotoxicity in tissue analyzed: no decrease in group mean PCE/NCE ratio (this was 0.99 and 1.31 for control and 1.10 and 1.14 for chloroethane treated male and female B6C3F1 mice, respectively).

Applicant's summary and conclusion

Conclusions:

Interpretation of results: negative