2,4-xylenol

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Based on the results of the in vitro Ames study, the test substance is considered to have no mutagenic potential.

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1981

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Suspensions of bacterial cells are exposed to the test substance in the presence and in the absence of an exogenous metabolic activation system. In the plate incorporation method, these suspensions are mixed with an overlay agar and plated immediately onto minimal medium. After two or three days of incubation, revertant colonies are counted and compared to the number of spontaneous revertant colonies on solvent control plates.

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Remarks:

TA 1538

Metabolic activation:

with and without

Metabolic activation system:

S-9 mix

Test concentrations with justification for top dose:

0,0.5,5,50,500,5000 µg/plate

Vehicle / solvent:

DMSO

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

sodium azide

Details on test system and experimental conditions:

Mutagenicity testing. The histidine auxotrophic indicator strains Salmonella typhimurium TA1535, TA1537, TA1538, TA98 and TA100 were kindly supplied by Dr. B. N. Ames, California. The test for their reversion to histidine prototrophy was performed using the plate incorporation assay. Each compound or smoke condensate fraction was dissolved in DMSO and tested in five concentrations in quadruplicate in the presence of buffer pH 7.4 or S-9 mix with cofactors (60 mg S-9 protein/10 ml S-9 mix) from Aroclor-pretreated Sprague-Dawley rats. The S-9 protein content was determined using the biuret method-kit of Boehringer, Mannheim. The sensitivity of the S-9 and of the indicator strains was monitored routinely using positive control compounds during each experiment. Significance levels for positive dose-response effects were obtained with the Joncheere test (Hollander & Wolfe, 1973). Special procedures in addition to the standard method were used to study the mutagenicity of the parent compound, phenol. These included incorporation of S-9 from untreated Sprague-Dawley rats, preincubation of the compound (added in 100 µl H20) with the bacteria and S-9 mix prior to plating, addition of S-9 mix with various protein contents, and inclusion of the co-mutagen norharman during the test.

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: The only dose-related effect was toxicity at the highest tested concentration (5000 µg). This was apparent as a thinning of the bacterial background lawn and as a reduced number of spontaneous revertants

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: The only dose-related effect was toxicity at the highest tested concentration (5000 µg). This was apparent as a thinning of the bacterial background lawn and as a reduced number of spontaneous revertants

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: The only dose-related effect was toxicity at the highest tested concentration (5000 µg). This was apparent as a thinning of the bacterial background lawn and as a reduced number of spontaneous revertants

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

other: The only dose-related effect was toxicity at the highest tested concentration (5000 µg). This was apparent as a thinning of the bacterial background lawn and as a reduced number of spontaneous revertants

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: The only dose-related effect was toxicity at the highest tested concentration (5000 µg). This was apparent as a thinning of the bacterial background lawn and as a reduced number of spontaneous revertants

Positive controls validity:

valid

Additional information on results:

The number of histidine revertants scored in the presence of the test substance, 2,4-dimethylphenol, never more than slightly exceeded that umber of spontaneously arising revertants. For the test substance the only dose-related effect was toxicity at the highest tested concentration (5000/µg). This was apparent as a thinning of the bacterial background lawn and as a reduced number of spontaneous revertants.

Result:

Special procedures in addition to the standard method were used to study the mutagenicity of the parent compound, phenol:

No mutagenic effect of phenol is observable in preincubation of the compound (added in 100/al H20) with the bacteria and S-9 mix prior to plating, addition of S-9 mix with various protein contents, and inclusion of the comutagen norharman during the test (table 3 and 4).

Conclusions:

Under the study conditions, the test substance was not mutagenic in in S. typhimurium strains TA 1535, TA 1537, TA 1538 TA 98 and TA 100 in the reverse mutation assay with and without metabolic activation.

Executive summary:

An in vitro study was conducted to investigate the potential of test substance, to induce gene mutations Salmonella typhimurium strains. Salmonella typhimurium strains TA 1535, TA 1537, TA 1538, TA 98 and TA 100 were treated with the test substance using the Ames plate incorporation. The assay was performed with and without metabolic activation (S9 mix). Each concentration, including the controls, was tested in quadruplicate. The concentrations of the test substance ranged from 0.5 to 5000 μg/plate. The sensitivity of the S-9 and of the indicator strains was monitored routinely using positive control compounds during each experiment. For the test substance the only dose-related effect was toxicity at the highest tested concentration (5000/µg). This was apparent based on thinning of the bacterial background lawn and reduced number of spontaneous revertant. No substantial increase in revertant colony numbers in any of the five tester strains was observed following treatment with the test substance either in the presence or absence of S9 mix. Under the study conditions, the test substance was not mutagenic in in S. typhimurium strains TA 1535, TA 1537, TA 1538 TA 98 and TA 100 in the reverse mutation assay with and without metabolic activation (Pool, 1982).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

An in vitro study was conducted to investigate the potential of test substance, to induce gene mutations Salmonella typhimurium strains. Salmonella typhimurium strains TA 1535, TA 1537, TA 1538, TA 98 and TA 100 were treated with the test substance using the Ames plate incorporation. The assay was performed with and without metabolic activation (S9 mix). Each concentration, including the controls, was tested in quadruplicate. The concentrations of the test substance ranged from 0.5 to 5000 μg/plate. The sensitivity of the S-9 and of the indicator strains was monitored routinely using positive control compounds during each experiment. For the test substance the only dose-related effect was toxicity at the highest tested concentration (5000/µg). This was apparent based on thinning of the bacterial background lawn and reduced number of spontaneous revertant. No substantial increase in revertant colony numbers in any of the five tester strains was observed following treatment with the test substance either in the presence or absence of S9 mix. Under the study conditions, the test substance was not mutagenic in in S. typhimurium strains TA 1535, TA 1537, TA 1538 TA 98 and TA 100 in the reverse mutation assay with and without metabolic activation (Pool, 1982).

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the results of the in vitro Ames study, the test substance does not warrant a classification for genotoxicity according to EU CLP (Regulation 1272/2008/EC) criteria.