Tar, coal, high-temp.

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 July - 24 Aug. 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

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

Species / strain / cell type:

S. typhimurium TA 102

Metabolic activation:

with and without

Metabolic activation system:

Microsomal fraction prepared from induced livers of male Wistar rats, induced with phenobarbital (80 mg/kg bw) and ß-naphthoflavone (100 mg/kg bw) orally (3x)

Test concentrations with justification for top dose:

1st experiment: 10, 31.6, 100, 316, 1000, 2500, and 5000 µg/plate, plus 3.16 µg/plate with TA 98 and TA 100 //...
2nd experiment: 31.6, 61.5, 125, 250, 500, 1000, 2000, 3500, and 5000 µg/plate (without S9)
1.58, 5.0, 15.8, 50, 158, 500, 1580, and 5000 µg/plate (with S9)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: compatible with survival of bacteria and S9 activity

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: see Report p. 15

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)
DETERMINATION OF CYTOTOXICITY
- Method: relative total growth/colony formation

Evaluation criteria:

Considered as mutagenic ....
- if a clear and dose-related increase in the number of revertants occurs in at least one tester with or without metabolic activation and/or
- if a biologically relevant positive response for at least one of the dose groups occurs in at least one tester with or without metabolic activation.
An increase is considered relevant - if in TA 100 and TA 102 mutation rate is at least twice as high as the rate of the solvent control;
- if in TA 98, TA 1535, and TA 1537 the mutation rate is at least 3x higher than that of the solvent control.

Statistics:

According to the OECD guidelines, the biological relevance is the criterion for the interpretation of the results: a statistical evaluation was not considered necessary under this premise (report p. 21).

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

at >= 316 µg/pl. (-S9); at >= 1000 µg/pl. (+S9)

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium, other: TA 98, TA 1537

Metabolic activation:

with

Genotoxicity:

positive

Remarks:

clear effect, reproducible

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

not cytotoxic in the mutagenic concentration range

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium, other: TA 100, TA 102

Metabolic activation:

with

Genotoxicity:

positive

Remarks:

weak positive effect, reproducible

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

not in the relevant mutagenic concentration range

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium, other: TA 98, TA 100, TA 1537, TA 102

Metabolic activation:

without

Genotoxicity:

ambiguous

Remarks:

not reproducible

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

in the relevant concentration range

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Summary:

The results without S9 were weak and not reproducible in either experiment (see below).

In the presence of S9 clear dose-related increases in the mutation rates were found in TA 98 and 1537 and a weak positive correlation in TA 100 and TA 102, reproducible at non-cytotoxic concentrations in both experiments. The most responsive tester strain was TA 98.

[Mutation factors (+S9) = 4 - 27x above background with maximum in TA 98]

In either experiment, no biological relevant increases in the mutation rate were seen in TA 1535.

Experiment I:

Relevant increases in TA 100 and TA 1537 (>= 316 and >= 100 µg/plate, respectively, -S9);

relevant increases in TA 98, TA 100, TA 1537, and TA 102 (>= 10 µg/plate, +S9)

Experiment II:

Relevant increases in TA 98 (61.5 and 125 µg/plate, -S9);

relevant increases in TA 98, TA 100, TA 1537, and TA 102 (>= 5 - 1580 µg/plate, +S9)

Dose-response relationship of the reversion rate was observed with each tester strain.

Conclusions:

Coal tar produced mutations in dose-dependent reproducible manner in the Salmonella reverse mutation assay according to OECD 471 in the presence of a metabolising enzyme system.

Additional information

Short description of key information:
Coal tar is mutagenic in the Ames-Salmonella test in the presence of a metabolising enzyme system (S9).

Endpoint Conclusion: Adverse effect observed (positive)