Bromoform

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Data source

Reference

Reference Type:

publication

Title:

Mutagenicity of 42 Chemicals in Salmonella

Author:

Errol Zieger

Year:

1990

Bibliographic source:

Environmental and Molecular (Mutagenesis Volume 16, Supplement 18:32-54 (1990).

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

GLP compliance:

no

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Bromoform

EC Number:

200-854-6

EC Name:

Bromoform

Cas Number:

75-25-2

Molecular formula:

CHBr3

IUPAC Name:

tribromomethane

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Aldrich Chemical Company.
- Purity: 97.7%

Method

Target gene:

- S. typhimurium: His-locus

Species / strain

Species / strain 1

Species / strain / cell type:

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

Species / strain 2

Species / strain / cell type:

S. typhimurium TA 97

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254-induced Sprague-Dawley rats or Syrian hamsters liver S9 (due to the nature of the study as an inter-laboratory trial, tests were run using both types).

Test concentrations with justification for top dose:

For the standard plate method: 0, 100, 3.333, 1000, 6,666, 10,000 µg/mL

For the desiccator method designed to take account of the volatility of the test substance: 0.000, 0.001, 0.005, 0.007, 0.010, 0.020, 0.025, 0.035, 0.050, 0.100, 0.500, 1.000 mL/chamber.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: dimethyl sulfoxide (DMSO)

Controls

Controls 1

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Controls 2

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

sodium azide

other: 4-nitro-o-phenylenediamine

Evaluation criteria:

Evaluations of the results were made at both the individual trial and overall chemical levels. Individual trials were judged mutagenic (+), weakly mutagenic (+ W), questionable (?), or non-mutagenic (-), depending on the magnitude of the increase in his+ revertants, and the shape of the dose-response. A trial was questionable (?) if the dose response was judged insufficiently high to support a call of "+ W", if only a single dose was elevated over the control, or if a weak increase was not dose-related.

The distinctions between a questionable mutagenic response and a non-mutagenic or weak mutagenic response and between a weak mutagenic response and mutagenic response are highly subjective. It was not necessary for a response to reach twofold over background for a trial to be judged "+" or "+ W". A chemical was judged mutagenic (+) or weakly mutagenic (+ W) if it gave a reproducible dose-related response over the solvent control in replicate trials, and judged questionable (?) if the results of individual trials were not reproducible or if only single doses produced increases in his' revertants in repeat trials. Chemicals were judged non-mutagenic (-) if they did not meet the criteria for a mutagenic or questionable response.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not applicable

Remarks:

No vehicle used

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not applicable

Remarks:

No vehicle used

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

other: TA1535, TA1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not applicable

Remarks:

No vehicle used

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Species / strain:

other: TA97, TA1535, TA1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 5

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 6

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: desiccator method

Applicant's summary and conclusion

Conclusions:

The test substance was considered positive for mutagenicity in salmonella typhimurium in the Ames test.

Executive summary:

Introduction

The study was conducted to determine the mutagenic potential of the test substance to Salmonella typhimurium using a test method comparable to the OECD 471 Bacterial Reverse Mutation Test

Method

S. typhimurium strains TA97, TA98, TA100, TA1535, and TA1537 were used.  Because the testing was done as part of an inter-laboratory trial testing was conducted in more than one laboratory on coded samples.   The test used a preincubation procedure with and without exogenous metabolic activation.  The metabolising system was liver S-9 derived from Aroclor 1254-induced Sprague-Dawley rats and Syrian hamsters. Experiments were conducted with both types of S9.

The test substance is a volatile chemical and following testing in the preincubation procedure it produced either negative or equivocal responses in some laboratories.  It was therefore retested at one laboratory using exposure in a desiccator. Test strains were TA98, TA100, TA1535 and TA1537. In this procedure, S-9 or buffer was incorporated into the top agar and poured onto the plate. The lids of the plates were removed and the plates were stacked on a perforated porcelain plate in a 9 litre glass desiccator jug containing a magnetic stirring bar. A measured volume of test chemical in liquid form was introduced into a watch glass suspended below the porcelain plate, and the desiccator was sealed and placed on a magnetic stirrer in a 37°C incubator.  After 24 hr, the plates were removed from the desiccator and incubated at 37°C in air for an additional 24 hr.

 

Results

In the desiccator protocol which is considered the most reliable method the test substance was positive for mutagenicity in strain TA 98 in the absence of S9 and positive in strain TA100 in the presence of S9.

Conclusion

The test substance was considered positive for mutagenicity in salmonella typhimurium the Ames test.