1,2-dichloroethane

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:

1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1993

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

yes

Remarks:

, no positive control, an uncommon mouse strain though answering the Guideline criteria, and different sampling time.

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

1,2-dichloroethane

EC Number:

203-458-1

EC Name:

1,2-dichloroethane

Cas Number:

107-06-2

Molecular formula:

C2H4Cl2

IUPAC Name:

1,2-dichloroethane

Details on test material:

- Name of test material: 1,2-dichloroethane
- Source: Sigma Chemical Company (St. Louis, Mo, U.S.A)

Test animals

Species:

mouse

Strain:

other: Eµ-PIM-1 transgenic mice, lymphona prone

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female (5 - 10 week old, 20 - 30 g) Eµ - PIM 1 transgenic mice were obtained from GenPharm International (Mountain View CA, U.S.A). Mice were randomized then housed in a clean air room with a 12 h light/dark cycle and given food ad libitum. Study animals had an acclimization period of 2-4 weeks.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

Corn oil (5 mL/kg bw)

Details on exposure:

- Treated and vehicle control animals were dosed daily (7 days per week) by oral gavage
- Corn oil suspensions of 1,2-dichloroethane were prepared weekly and were administered at 5 mL/kg bw
- Male and female mice were treated with 1,2-dichloroethane initially at 100 and 200 mg/kg bw (males) or 150 and 300 mg/kg bw (females) but the top doses were sequentially reduced by week 6, to 100 mg/kg bw for males and 150 mg/kg bw for females due to mortality and failure to gain weight.

Duration of treatment / exposure:

41 weeks (42 weeks were planned)

Frequency of treatment:

Once daily

Post exposure period:

No post exposure period

Doses / concentrations

Remarks:

Doses / Concentrations:
100 and 200 mg/kg bw for males, 150 and 300 mg/kg bw for females. After the 6th week of treatment, 100 mg/kg bw for males and 150 mg/kg bw for females were administered.
Basis:
nominal conc.

No. of animals per sex per dose:

5 animals per sex, 10 animals (5 males and 5 females) per dose

Control animals:

yes, concurrent vehicle

Positive control(s):

No positive control was used

Examinations

Tissues and cell types examined:

Peripheral blood; polychromatic (PCE) and normochromatic (NCE) erythrocytes

Details of tissue and slide preparation:

Peripheral blood (10-20 µL) was collected from a ventral tail vessel at 14 weeks and from the vena cava at terminal sacrifice. Blood smears were air dried then fixed for 10 min in absolute methanol. To reduce fading slides were scored within 1 week of staining with acridine orange. Coded slides were examined using a epifluorescence microscopy.
Slides from 10 animals per treatment group were analysed by one scorer for the number of micronucleated cells per 1000 NCE and the number of PCE per 1000 erythrocytes.

Evaluation criteria:

Statistically significant compared to the control

Statistics:

Data from male and female mice were analysed separately using the Micronucleous Assay Data Management and Analysis System Software (Integrated Laboratory Systems, research triangle park, NC) as follows: The significance level was set at p ≤ 0.05. There was no evidence of significant interanimal variability in control groups so the number of MN-erythrocytes (MN-PCE or MN-NCE) were pooled across animals within each treatment group and assessed for dose effect using a one - tailed trend rest. a pairwise comparison between each treatment group and teh concurrent control was also done to determine the lowest effective dose. an ANOVA ratio was used to assess whether the percentages of PCE were significantly increased of reduced by treatment, indicating perturbation of erythropoiesis.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

, after 6 weeks of repeated dose of 200 mg/kg bw in males and 300 mg/kg bw in females per day, mortality and failure to gain weight were observed (therefore the dosage after week 6 was changed).

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

not examined

Additional information on results:

Peripheral blood PCE frequencies were not affected by exposure to 1,2-dichloroethane at 14 weeks or at 41 weeks.
No treatment related increases in MN (micronucleus) - erythrocytes were seen in either sex at 14 weeks or at 41 weeks, when only NCE were analysed (because treatment had been stopped a week before sample collection).

Any other information on results incl. tables

No remarks

Applicant's summary and conclusion

Conclusions:

There was no micronucleus induction or PCE suppression detected in the either sex after treatment with 100 to 300 mg/kg bw 1,2-dichloroethane in the presented study. Thus, under the conditions of the study, 1,2-dichloroethane was not considered to induce cytogenetic damage (chromosome damage). 1,2-dichloroethane therefore was not considered as a clastogenic substance.

Executive summary:

1,2 dichloroethane was examined for its possible cytogenetic effects (induction of chromosomal damage) using the micronucleus test, similarily conducted according to OECD Test Guideline 474 (Mammalian Erythrocytes Micronucleus Test) . Micronucleus (MN) induction in peripheral blood was examined in 10 male and female mice (lymphoma prone Eµ - PIM 1 transgenic mice) per dose after a repeated dose of 1,2 -dichloroethane in corn oil administered by gavage (5 mL/kg bw) once a day in concentrations of 100 and 200 mg/kg bw (in males) and 150 and 300 mg/kg bw (in females) up to week 6. After week 6 until the end of the exposure period (week 41) the top doses were reduced, therefore male animals were only administered with 100 mg/kg bw and females were only administered with 150 mg/kg bw (due to mortality and treatment related weight gain). Two negative controls were performed, a vehicle control and a “true” negative control with methyl cellulose. Peripheral blood was collected at week 14 and at terminal sacrifice (41 week) and analysed a week later (week 42). Stained slides (acridine orange staining) from 10 animals per treatment group were analysed for the number of micronucleated cells per 1000 NCE (normochromatic erythrocytes) and the number of PCE (polychromatic erythrocytes) per 1000 erythrocytes (Since exposure was discontinued one week before the terminal harvest of mice, only NCE were scored for micronuclei because of the short residence time of polychromatic erythrocytes.

Results showed no micronucleus induction (in normochromatic erythrocytes) after 14 weeks or 41 weeks of 1,2 -dichloroethane exposure and no polychromatic erythrocyte suppression was detected in the blood after 14 weeks or 41 weeks of exposure to the test substance. It can therefore be concluded that under the study conditions, 1,2 -dichloroethane induced no cytogenetic damage/chromosome damage.