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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study is GLP and in accordance with OECD guidelines.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1988

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Principles of method if other than guideline:
The standard test plate method and the pre-incubation test were both performed with and without the S-9 metabolic activator.
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Constituent 1
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
Details on test material:
- Analytical purity: 97.5%

Method

Target gene:
Histidine
Species / strain
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Metabolic activation system:
S-9 fraction extracted from rat livers
Test concentrations with justification for top dose:
1st experiment - std plate test with and without metabolic activator
0, 20, 100, 500, 2500 and 5000 micrograms /plate

2nd experiment - std plate test with and without metabolic activator
0, 4, 20, 100, 500 and 1500 micrograms/plate

3rd experiment - pre-incubation test with and without metabolic activator
0, 4, 20, 100, 500 and 1000 micrograms /plate

4th experiment - pre-incubation test with and without metabolic activator
0, 15, 30, 60, 125 and 250 micrograms/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
Controls
Untreated negative controls:
yes
Remarks:
solvent control and steriity control
Positive controls:
yes
Positive control substance:
other: see below for details.
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)
NUMBER OF REPLICATIONS: 3 plates per dose or control

The following positive controls were used to check the mutability of the bacteria and the activity of the S-9 mix.

With S-9 mix - 2-aminoanthracene for all strains
Without S-9 mix - N-methyl-N-nitro-N-nitroso-guanidine (MNNG) for strains TA100 and TA 1535
4-nitro-o-phenylendiamine for the strain TA 98
9-aminoacridine chloride monohydrate for the strain TA 1537




Evaluation criteria:
In order for the substance to be characterised as having a postive Ames test it must fulfil the following requirements:
- doubling of the spontaneous mutation rate relative to the control
- dose response relationship
- reproducibility of the results

Results and discussion

Test results
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
Bacteriotoxicity was observed from 1500 micrograms/plate in the standard plate test and 125 micrograms /plate in the pre-incubation test.
Untreated negative controls validity:
valid

Applicant's summary and conclusion

Conclusions:
Interpretation of results:
negative with metabolic activation Pre-incubation test
negative without metabolic activation Pre-incubation test
negative with metabolic activation Standard Plate Test
negative without metabolic activation Standard Plate Test

According to the results of this BASF study, 4-chloro-o-cresol is not mutagenic in the Ames test under the test conditions reported here.
Executive summary:

In a guideline study 4 -chloro-o-cresol was tested for mutagenicity in the Ames test.

Strains TA1535, TA 100, TA 1537 and TA98 of Salmonella Typhimurium were tested in the dose range 4 - 5000 micrograms /plate in the standard plate test and 4 - 1000micrograms/plate in the pre-incubation test.

Both were performed with and without metabolic activation (S-9 mix).

Clear bacteriotoxicity was observed from 1500 micrograms/plate in the standard plate test and 125 micrograms /plate in the pre-incubation test.

An increase in the number of histadine+ revertants was not observed in either the standard plate test or the pre-incubation test with or without metabolic activation. 4-chloro-o-cresol is not mutagenic in the Ames test under the test conditions reported here.