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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 September 2018 - 20 September 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
The substance can be produced through different process routes, yielding solutions in water or organic solvent (e.g. methanol or ethylene glycol).
It was initially unclear how to register the substance (mono-constituent or multi-constituent substance) and which manufactured substance to test to fulfil the REACH data requirements. After consultation with the ECHA helpdesk, the test program was started with the manufactured substance of the Lead registrant (solvent: methanol) in which the highest amount of solvent could be removed without causing degradation of the substance. This resulted in the selection of a solution of 56-57% BTMAOH in methanol as test substance.
During the course of the test program, and in order to aid meaningful risk assessment, after consultation with ECHA and upon ECHA's recommendation, it was considered to be more appropriate to test the water-based manufactured substance. As a consequence, some testing was performed with a BTMAOH solution in methanol, and some testing was performed with a BTMAOH solution in water.

The current entry reflects a test performed with a water-based test solution.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
21 July 1997
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
31 May 2008
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Details on test material:
Appearance: Clear almost colourless liquid
Test item storage: At room temperature
Stable under storage conditions until: 30 November 2020 (expiry date)

Method

Target gene:
- S. typhimurium: Histidine gene
- E. coli: Tryptophan gene
Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
E. coli WP2 uvr A
Metabolic activation:
with and without
Metabolic activation system:
Type and composition of metabolic activation system:
- source of S9 : rat liver S9-mix induced by Aroclor 1254 (500 mg/kg bw)
- method of preparation of S9 mix: S9-mix per 10 mL: 30 mg NADP, 15.2 mg glucose-6-phosphate in 5.5 mL Milli-Q water; 2 mL 0.5 M sodium phosphate buffer pH 7.4; 1 mL 0.08 M MgCl2 solution; 1 mL 0.33 M KCl solution. The solution was filter (0.22 μm)-sterilized and 0.5 mL S9-fraction was added
- concentration of S9 in S9 mix: 5%
- quality controls of S9: Each S9 batch was characterized with the mutagens benzo-(a)-pyrene and 2-aminoanthracene, which require metabolic activation, in tester strain TA100 at concentrations of 5 μg/plate and 2.5 μg/plate, respectively
Test concentrations with justification for top dose:

Justification for top dose: 5 mg is the recommended maximum test concentration according to the guideline.

Direct plate assay
Dose-range finding test (without and with S9; tester strains TA100 and WP2uvrA): 1.7, 5.4, 17, 52, 164, 512, 1600 and 5000 µg/plate (reported as part of experiment 1)
First experiment (without and with S9; tester strains TA1535, TA1537 and TA98): 52, 164, 512, 1600, 5000 μg/plate

Pre-incubation assay
Second experiment (without and with S9, tester strains WP2uvrA, TA1535, TA1537, TA 98 and TA100): 52, 164, 512, 1600, 5000 μg/plate
Vehicle / solvent:
- Vehicle used: Milli-Q water

Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
2-nitrofluorene
sodium azide
methylmethanesulfonate
other: 2-aminoanthracene; ICR-191
Remarks:
For details on positive control substances, see Table 1 and Table 2
Details on test system and experimental conditions:
Two individual experiments were performed. The dose range-finding study with tester strains TA100 and WP2uvrA was reported as part of the first experiment. The first experiment was a direct plate assay. The second experiment was a pre-incubation assay and was performed to obtain more information about the possible mutagenicity of the test item.

METHOD OF APPLICATION: in agar (plate incorporation)

NUMBER OF REPLICATIONS:
- Doses levels were tested in triplicate in each strain.

METHODS: The following solutions were successively added to 3 mL molten top agar: 0.1 mL of a fresh bacterial culture (1E9 cells/mL) of one of the tester strains, 0.1 ml of a dilution of the test item in Milli-Q water
and either 0.5 ml S9-mix (in case of activation assays) or 0.5 mL 0.1 M phosphate buffer (in case of non-activation assays)

DURATION
- Preincubation period (second experiment): 30 ± 2 minutes at 70 rpm at 37 ± 1°C
- Exposure duration: 48 ± 4 h (in the dark at 37.0 ± 1.0 °C)

DETERMINATION OF CYTOTOXICITY
- Method: the reduction of the bacterial background lawn, the increase in the size of the microcolonies and the reduction of the revertant colonies.
- Other: precipitation of the test item was recorded

COLONY COUNTING
The revertant colonies were counted automatically with the Sorcerer Colony Counter. Plates with sufficient test item precipitate to interfere with automated colony counting were counted manually. Evidence of test item precipitate on the plates and the condition of the bacterial background lawn were evaluated when considered necessary, macroscopically and/or microscopically by using a dissecting microscope.

ACCEPTABILITY CRITERIA
A Salmonella typhimurium reverse mutation assay and/or Escherichia coli reverse mutation assay is considered acceptable if it meets the following criteria:
a) The vehicle control and positive control plates from each tester strain (with or without S9-mix) must exhibit a characteristic number of revertant colonies when compared against relevant historical control data generated at Charles River Den Bosch.
b) The selected dose-range should include a clearly toxic concentration or should exhibit limited solubility as demonstrated by the preliminary toxicity range-finding test or should extend to 5 mg/plate.
c) No more than 5% of the plates are lost through contamination or some other unforeseen event. If the results are considered invalid due to contamination, the experiment will be repeated.
Evaluation criteria:
A test item is considered negative (not mutagenic) in the test if:
a) The total number of revertants in tester strain TA100 or WP2uvrA is not greater than two times the concurrent control, and the total number of revertants in tester strains TA1535, TA1537 or TA98 is not greater than three times the concurrent control.
b) The negative response should be reproducible in at least one follow up experiment.

A test item is considered positive (mutagenic) in the test if:
a) The total number of revertants in tester strain TA100 or WP2uvrA is greater than two times the concurrent control, or the total number of revertants in tester strains TA1535, TA1537 or TA98 is greater than three times the concurrent control.
b) In case a repeat experiment is performed when a positive response is observed in one of the tester strains, the positive response should be reproducible in at least one follow up experiment.

Any increase in the total number of revertants should be evaluated for its biological relevance including a comparison of the results with the historical control data range

Results and discussion

Test resultsopen allclose all
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
First Experiment: Direct Plate Assay
Precipitation:
No precipitation of the test item was observed.

Cytotoxicity:
A moderately or slighty reduced bacterial background lawn was observed in tester strains TA1537 and TA98 in the absence and presence of S9-mix and in tester strain TA1535 in the absence of S9-mix at the top dose level of 5000 μg/plate.

Mutagenicity:
In the direct plate test, no increase in the number of revertants was observed upon treatment with Benzyltrimethylammonium hydroxide under all conditions tested.

Second Experiment: Pre-Incubation Assay
Precipitation:
Precipitation of test item on the plates was observed at the start and at the end of the incubation period at the concentration of 5000 μg/plate.

Cytotoxicity:
A moderately or slighty reduced bacterial background lawn was observed in all tester strains in the absence and presence of S9-mix at the top dose level of 5000 μg/plate.

Mutagenicity:
In the pre-incubation test, no increase in the number of revertants was observed upon treatment with the test item under all conditions tested.

Acceptability criteria:
The negative and strain-specific positive control values were within the laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly.

Applicant's summary and conclusion

Conclusions:
Based on the results of an Ames test, performed according to OECD guideline 471 and GLP principles, Benzyltrimethylammonium hydroxide is not mutagenic in the Salmonella typhimurium reverse mutation assay and in the Escherichia coli reverse mutation assay.
Executive summary:

A bacterial reverse mutation test was performed according to OECD guideline 471 and GLP principles to determine the potential of Benzyltrimethylammonium hydroxide and/or its metabolites to induce reverse mutations at the histidine locus in several strains of Salmonella typhimurium (S. typhimurium; TA98, TA100, TA1535, and TA1537) and at the tryptophan locus of Escherichia coli (E. coli) strain WP2uvrA in the presence or

absence of S9 -metabolic activation. Bacterial strains were tested in the absence and presence of S9-metabolic activation in two independent experiments, a direct plate assay and a pre-incubation assay, up to and including the highest recommended concentration (5 mg/plate). The negative and strain-specific positive control values were within the laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system (S9 -mix) functioned properly. The test item did not induce a significant dose-related increase in the number of revertant (His+) colonies in each of the four tester strains (TA1535, TA1537, TA98 and TA100) and in the number of revertant (Trp+) colonies in tester strain WP2uvrA both in the absence and presence of S9-metabolic activation. Based on the results of this study it is concluded that the test item is not mutagenic in the Salmonella typhimurium reverse mutation assay and in the Escherichia coli reverse mutation assay.