Sodium chlorodifluoroacetate

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Sodium chlorodifluoroacetate

EC Number:

217-586-0

EC Name:

Sodium chlorodifluoroacetate

Cas Number:

1895-39-2

Molecular formula:

C2HClF2O2.Na

IUPAC Name:

sodium chloro(difluoro)acetate

Test material form:

solid: particulate/powder

Method

Target gene:

his D (S. typhimurium TA 98); his C (S. typhimurium TA 1537); his G (S. typhimurium TA 100 and TA1535); tryp E (E. coli WP2 uvrA pKM101)

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:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

Preparation os the metabolic activation system:
- Obtention of S9: S9 fraction prepared from Sprague Dawley rat liver homogenate, provided by MOLTOXTM (POB Box 1189 - 157 Industrial Park Dr - Boone, NC 28607 - USA).
- Preparation of S9 mix 10%: 10% S9 fraction, 8 mM MgCL2-6H2O, 33 mM KCl, 5 mM Glucose-6-Phosphate Na2, 4 mM NADP Na2 and 0.1 M Phosphate buffer pH 7.4.
- preliminary cytotoxicity testing: Sterility test: 50 μL of S9-mix were added to 2 mL of top agar at 45ºC, homogenized and poured on the agar (20 ml) onto a Petri plate in three plates. Plates were incubated for 48 - 72 hours at 37°C.

Test concentrations with justification for top dose:

0.00625, 0.0125, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 and 5 mg/plate. The test item resulted in cytotoxicity no cytotoxicity from 0.00625 to 5 mg/plate when compared to vehicle control with lawn intensity 4+ (thick lawn) both in the presence and absence of metabolic activation system. Based on cytotoxicity results, 5 mg/plate is considered as the highest test concentration for mutation assay.

Vehicle / solvent:

- Vehicle/solvent: Distilled water

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

Distilled water at concentration 50 mg/mL

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

9-aminoacridine

2-nitrofluorene

sodium azide

other: 2-aminoanthracene (1, 2 μg/plate; S. typhimurium strains, + S9)

Details on test system and experimental conditions:

PRELIMINARY CYTOTOXICITY TEST:
In a test tube 0.1 mL of the bacterial suspension (1-9 X 10^3 bacteria /mL) and 0.1 mL of the stock solution and dilutions were successively added to 2 mL of top agar at 45ºC, containing 10 % (v/v) of a solution of L-Histidine-D-Biotine (2.5 mM). After homogenization, the content of the tube was poured onto a Petri plate (90 mm in diameter) containing minimal agar (20 mL). 3 plates per concentration were incubated for 48-72 h at 37ºC, and the colonies counted. A negative control containing the blank alone was run in parallel.
In case of bacteriostatic activity is detected, the highest concentration to be retained is that exhibiting a bacteriostatic activity of 75% or less. The precipitate, if present, should not interfere with the scoring.

METHOD:
1. Without metabolic activation: Salmonella Typhimurium strains: Solution of the test item was prepared at 100 mg/mL. In a test tube, 0.1 mL of the bacterial suspension containing 1-9 x10^9 bacteria/mL and 0.1 mL of each dilution of the original solution and 0.5 mL of sterile phosphate buffer are successively added to 2 mL of overlay agar maintained super cooled at 45ºC containing 10% (v/v) of a L-Histidine-D-Biotine solution (0.5 mM).
For Escherichia coli strain containing 5% (v/v) of nutrient broth nº2 to which are added 5 μL of a L-Tryptophane solution at 2 mg/mL.
With metabolic activation, is similar to the described above, except that, 500 μL of S9-mix fraction is quickly added, before pouring the mixture onto the plates. After a 48-72 hour incubation period at 37ºC, revertant colonies are counted in each plate.

2. Pre-incubation: The test item solution with the test strain, and 500 μL of S9-mix fraction are preincubated with shaking for 30 min., at 37ºC prior to mixing with the overlay agar and pouring onto the minimal agar plate. After a 48-72 hour incubation period at 37ºC, revertant colonies are counted in each plate.

DATA PRESENTATION
After a 48-72-hour incubation period at 37ºC, revertant colonies were manually counted in each plate. The following ratio was calculated per plate: R = Number of revertant colonies in the presence of the test item / Number of revertant colonies in the absence of the test item.

Evaluation criteria:

The result of the test is considered as negative if the revertant number is below three fold the number of spontaneous reversions, for TA 1535 and TA 1537 strains, and below two fold the number of spontaneous reversions for TA 98, TA 100 and Escherichia coli WP2(uvrA-) (pKM 101) strains without and with metabolic activation.

The result of the test is considered positive if a dependent relationship concentration is obtained in one, or several of the 5 strains, without and/or with metabolic activation, a mutagenic effect being taken into account for a given dilution of test item if the number of revertant colonies is at least two fold that of spontaneous revertant colonies for TA 98, TA 100 and Escherichia coli WP2(uvrA-) (pKM 101), and three fold for TA 1535 and TA 1537.

All results must be confirmed in an independent experiment.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Applicant's summary and conclusion

Conclusions:

The test item did not induce any mutagenic change in the bacterial reverse mutation test in any of the strains tested with and without metabolic activation up to 5 mg/plate.

Executive summary:

A bacterial reverse mutation test was conducted on the test substance according to OECD guideline 471 under GLP conditions. Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537 and Escherichia coli WP2 uvrA were exposed to concentrations of the test substance ranging from 50 to 5000 μg/plate in DMSO, with and without metabolic activation, based on preliminary solubility and cytotoxicity tests. The metabolic activation system (S9 fraction) was prepared from Sprague Dawley rat liver homogenate. Two independent assays were performed in all strains: an initial mutation test (plate incorporation method) and a confirmatory mutation test (plate incorporation method without S9 and pre-incubation method with S9). Untreated, solvent controls and strain specific positive controls were included in the assays and the values obtained were within ranges of the historical control values of the laboratory in all strains. All validity criteria were fulfilled. The test item did not induce any significant increase in the number of revertants in any of the strains tested, with and without metabolic activation, up to 5 mg/plate. Based on these results, the test item can be considered as not mutagenic according to the OECD TG 471.