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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration
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:
read-across source

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report date:
2005

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)
GLP compliance:
yes (incl. QA statement)
Type of assay:
mammalian bone marrow chromosome aberration test

Test material

Constituent 1
Chemical structure
Reference substance name:
(4-chloro-2-methylphenoxy)acetic acid
EC Number:
202-360-6
EC Name:
(4-chloro-2-methylphenoxy)acetic acid
Cas Number:
94-74-6
Molecular formula:
C9H9ClO3
IUPAC Name:
(4-chloro-2-methylphenoxy)acetic acid
impurity 1
Chemical structure
Reference substance name:
Water
EC Number:
231-791-2
EC Name:
Water
Cas Number:
7732-18-5
Molecular formula:
H2O
IUPAC Name:
water
impurity 2
Chemical structure
Reference substance name:
4-chloro-o-cresol
EC Number:
216-381-3
EC Name:
4-chloro-o-cresol
Cas Number:
1570-64-5
Molecular formula:
C7H7ClO
IUPAC Name:
4-chloro-2-methylphenol
Test material form:
solid
Specific details on test material used for the study:
Tested compound and dose range
Test substance MCPA was prepared for administration as suspension of MCPA in 0,5% carboxymethylcellulose. The substance volumes (12.5 -100 mg/kg) for individual animals were chosen due to the individual body weights. The substance volumes (calculation) are recorded in the primary documentation.
Solvent: 0.5% carboxymethylcelullose
Auxiliary compound: Aqua pro injectione

Positive control
Cyclophosphamidum monohydricum (ENDOXAN) was used as positive control compound in this study. The compound was dissolved in sterile distilled water and immediately injected intraperitoneally (i.p.) into mice in a dosage 20 mg/kg, volume 10 ml/kg.

Test animals

Species:
mouse
Strain:
ICR
Sex:
male
Details on test animals or test system and environmental conditions:
Experimental animals
ICR-SPF mice: 49 males, 8 weeks old and weighing 28-34 g (Protocol 8/2004).Supplier of animals: Accredited Breeding Velaz Prague. Identification of animals: signing of cages with indicating sex, dose and date of compound application. Animal acclimatization: 7 days.

Animal care and use statement
The animals were housed in experimental animal room in standard cages. Hygiene of housing and animal nursing was carried out according to (SOP 1, 7). The animals were maintained under 12h light and dark cycles in a room in which the relative humidity was at 55-60 % and the temperature was maintained at 22 ± 2°C, controlled according to (SOP 8, 9). The mice were fed with a balanced diet ST (according to TOP DOVO Dobra Voda) and tap water ad libitum. The animals were placed into the animal room 412/C on the Department of microbiology in the day of the test performance.

All procedures were in compliance with the Animal Welfare Act, the Guide for the Care and Use of Laboratory Animals, and the Office of Laboratory Animal Welfare. In the opinion of responsible investigator, the partial study does not unnecessarily duplicate any previous work.

Administration / exposure

Details on exposure:
Dose
Acute oral LD50 values for MCPA of 550 and 700 mg /kg of body weight have been reported in mice and rats. Based on this parameter three doses of MCPA were selected for the genotoxic assay (12.5, 25 and 100 mg/kg). The used doses were 44, 22 and 5.5 times lower than the published LD50 values.

Results and discussion

Test results
Key result
Sex:
male
Genotoxicity:
negative
Toxicity:
no effects
Remarks:
The used doses were 44, 22 and 5.5 times lower than the published LD50 acute tox values for MCPA.
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid

Applicant's summary and conclusion

Executive summary:

Bone marrow cells of male mice were used for in vivo cytogenetic analysis. The evaluation in a single sex was performed because there are expected no substantial differences in toxicity between sexes.

Five mice were examined in each experimental group and also in intact and (vehicle) group. Doses of up to 300 mg/kg were used in this experiment. The animals tolerated the highest dose with minimal symptoms of toxicity. In the group of animals treated with dose of 300 mg/kg was not possible to perform cytogenetic analysis because the numbers of mitoses were greatly diminished.

Oral administration of MCPA (25 and 100 mg/kg) induced a slight increase in the frequency of damaged cells and in the number of chromosome aberrations/cell over the level of control.

The results of statistical analysis did not show any significant differences in the percent aberrant metaphases exclusive of gaps between vehicle control (0.8 % of aberrant cells) and treated groups with MCPA at doses 25 and 100 mg/kg (1.8 %, 2.4 %). The percent aberrant metaphase exclusive of gaps in group mice treated with MCPA of 12,5 mg/kg was 0,6 %. 

The metaphase analysis of the bone marrow cells revealed mostly the presence of chromatid gaps and chromatid breaks in MCPA treated animals.

The positive control compound cyclophosphamide gave a significantly higher percentage of aberrant metaphase cells, as compared with the vehicle control. Cyclophosphamide induced a number of chromosomal abnormalities, including chromosome breaks, chromatide breaks and chromatide exchanges.

Mitotic index (MI) was calculated from 1000 cells/ animal and expressed in percentage. The percentages of dividing cells exhibited by the groups of mice that received MCPA at doses 12.5, 25 and 100 mg/kg did not differ much from that of the vehicle group of mice. Statistically significant reduction of percentage of dividing cells in the positive control group was not observed.

Obtained results showed MCPA did not cause significant increase in the frequency of cells with chromosome aberrations and also chromosomal aberrations/cell in vivo. Under our testing conditions, MCPA doses of 12.5,25 and 100 mg/kg body weight did not show any mutagenic effect after cytogenetic analysis of bone marrow. The results suggest that MCPA has no genotoxic potential in vivo.