chloromethane; methyl chloride

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian germ cell study: cytogenicity / chromosome aberration

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication/study report which meets basic scientific principles

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Reproductive effects of inhaled methyl chloride in the male Fischer 344 rat. I. Mating performance and dominant lethal assay

Author:

Working, P.K. et al.

Year:

1985

Bibliographic source:

Toxicology and Applied Pharmacology; 77(1):133-143

Reference 2

Reference Type:

secondary source

Title:

Chloromethane CAS: 74-87-3

Author:

OECD SIDS

Year:

2004

Bibliographic source:

SIDS Initial Assessment Report for SIAM 15 ; www.iccahpv.com

Reference 3

Reference Type:

secondary source

Title:

Methyl Chloride

Author:

Löf, A. et al.

Year:

2000

Bibliographic source:

Concise International Chemical Assessment Document 28

Reference 4

Reference Type:

secondary source

Title:

Toxicological review of methyl chloride (CAS No. 74-87-3)

Author:

Greenberg, M. and Riddle, J.

Year:

2001

Bibliographic source:

U.S. Environmental Protection Agency, EPA/635/R01/003

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 478 (Genetic Toxicology: Rodent Dominant Lethal Test)

GLP compliance:

not specified

Type of assay:

rodent dominant lethal assay

Test material

Test material information

Constituent 1

Reference substance name:

Chloromethane

EC Number:

200-817-4

EC Name:

Chloromethane

Cas Number:

74-87-3

Molecular formula:

CH3Cl

IUPAC Name:

chloromethane

Details on test material:

- Name of test material (as cited in study report): methyl chloride
- Analytical purity: 99.9%

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, N.Y., USA
- Weight at study initiation: 180-200 g
- Fasting period before study: no
- Housing: 5 per cage before onset of study, during exposure two to three per cage, after exposure individually
- Diet: ad libitum NIH-07 open formula diet (Ziegler Bros., Gardner, Pa.)
- Water: ad libitum filter-purified tap water
- Acclimation period: yes

Administration / exposure

Route of administration:

inhalation

Vehicle:

- Vehicle(s)/solvent(s) used: none

Details on exposure:

TYPE OF INHALATION EXPOSURE: whole body

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: stainless steel and glas Rochester-type 1 m³ chamber
- Method of holding animals in test chamber: hanging mesh cages
- Source and rate of air: room air
- Method of conditioning air: chloromethane was diluted with room air and passed through a HEPA filter
- Temperature and humidity in air chamber: 24-26 °C, 46-55% humidity
- Air flow rate: 225 L/min

TEST ATMOSPHERE
- Brief description of analytical method used: GC-FID
- Samples taken from breathing zone: yes, hourly

Duration of treatment / exposure:

6 hours/day

Frequency of treatment:

5 consecutive days

Post exposure period:

After exposure male mice had a 3-day recovery period before sequentially mating. One female was placed with each male. Females were removed when bred or after 5 days. This sequence was repeated weekly fo 8 weeks of breeding, after which the 1000 ppm chloromethane and triethylenemelamine exposed males were killed. The control and the 3000 ppm chloromethane exposed males were kept for an additional 8 weeks and bred once more to assess recovery.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
1000 and 3000 ppm (2065 and 6195 mg/m³)
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
987 +/- 39 ppm and 3005 +/- 120 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

40 male rats / dose

Control animals:

yes, sham-exposed

Positive control(s):

triethylenemelamine (TEM)
- Route of administration: single i.p. injection
- Doses / concentrations: 0.2 mg/kg

Examinations

Tissues and cell types examined:

Females were killed 12-17 days after mating and were examined for pregnancy, number of viable fetuses, number of resorptions, number of late fetal deaths and number of corpora lutea. The uteri of animals which were not pregnant, or in which the difference between the number of implants and the number of corpora lutea was more than two, were stained with 10% ammonium sulfide to reveal otherwise undetectable implantation sites.

Statistics:

Percentage of females mated per treatment group, the percentage of females pregnant per group and the percentage of mated females pregnant per group were analyzed by a one-tailed Fisher Exact test with the Bonferroni correction. The number of corpora lutea, the total number implants and the number of live fetuses were analyzed for significance by one-tailed Mann-Whitney U-test with Bonferroni correction. Numbers of females with or without dead implants or PI loss were analyzed for significance by one-tailed Fisher Exact test with Bonferroni correction. The body weight data were analyzed by analysis of variance, followed by Dunnett's test where appropriate. The 0.05 level of probability was used as the criterion of statistical significance.

Results and discussion

Test results

Sex:

male

Genotoxicity:

negative

Toxicity:

yes

Remarks:

weight loss in high dose group

Vehicle controls validity:

not specified

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Male rats exposed to 1000 ppm were able to fertilize female rats at a rate comparable to control males. Male rats exposed to 3000 ppm 6 hours per day for 5 consecutive days were infertile two weeks after exposure and remained below control animals for at least 8 weeks. 
The numbers of live and total implants were decreased, there was an increase in the percentage of preimplantation loss at weeks 2, 4, 6, and 8 postexposure, and there was an increase in the percentage of postimplantation loss at week 1 postexposure, only. The changes observed were not concentration related. A true dominant lethal effect of genetic origin could be questioned, as the time-courses of the pre- and postimplantation losses after chloromethane exposure were not the same as those obtained after administration of the positive control, triethylenemelamine (TEM). The development of sperm granulomas in the epididymis, the effects seen in the dominant lethal assay, seems to be cytotoxic rather than genotoxic in origin.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative