1,2-diethoxybenzene

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation potential: 1, 2-diethoxybenzene showed no mutagenic action in Bacteria (OECD 471, Klimisch rating: 1).

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:

from 2011-11-10 to 2012-05-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study (OECD 471) well performed. No deviation from the protocol of the study.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: ICH Guidance S2A: Guidance on Specific Aspects of Regulatory Genotoxicity Tests For Pharmaceuticals, 1995. ICH Guidance S2B: Genotoxicity: A Standard Battery for Genotoxicity Testing of Pharmaceuticals, 1997

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: EPA Health Effects Test Guidelines, OPPTS 870.5100 "Escherichia coli WP2 and WP2 uvrA Reverse Mutation Assays", EPA 712-C-96-247, June 1996 (Public Draft)

Deviations:

not specified

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Target gene:

Histidine gene (Salmonella typhimurium) and tryptophan gene (Escherichia coli WP2 uvrA)

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Details on mammalian cell type (if applicable):

Not applicable

Additional strain / cell type characteristics:

other: See Table 7.6.1/1

Metabolic activation:

with and without

Metabolic activation system:

S9 from induced phenobarbital and beta-naphthoflavone rat liver

Test concentrations with justification for top dose:

- 5000, 2500, 1000, 316, 100, 31.6 and 10 μg/plate (Informatory Toxicity Test, (+/- S9))
- 5000; 1581; 500; 158.1; 50 and 15.81 μg/plate (Initial Mutation Test, (+/-S9))
- 5000; 1581; 500; 158.1; 50 and 15.81; 5 and 1.581 μg/plate (Confirmatory Mutation Test, (+/- S9))

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO and WATER
- Justification for choice of solvent/vehicle: in this study, two vehicle control groups were used depending on the solubility of the test item and the solubility of strain specific positive chemicals. The test item is not soluble in Distilled water. Therefore, the solubility of the test item was examined in Dimethyl sulfoxide (DMSO), Acetone and N,N-Dimethylformamide (DMF). The test item was soluble in all of the three examined solvent. Due to the better biocompatibility to the test system, DMSO was selected for solvent of the study

Untreated negative controls:

yes

Remarks:

(untreated)

Negative solvent / vehicle controls:

yes

Remarks:

two vehicle control groups: DMSO and water

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: See Table 7.6.1/2

Remarks:

no remarks

Details on test system and experimental conditions:

METHOD OF APPLICATION:
- In agar (plate incorporation): In the Range Finding Test as well as in the Initial Mutation Test
- preincubation: in the Confirmatory Mutation Test

DURATION
- Incubation period: at 37°C for 48 hours.
- Preincubation period: 20 min at 37ºC

NUMBER OF REPLICATIONS: 3 plates/dose/strain. Two independent experiments were performed

DETERMINATION OF CYTOTOXICITY
- Method: the cytotoxicity of the test material was determined using TA100 and TA98 in the presence and absence of metabolic activation system (+/-S9 Mix) with appropriate untreated, negative (solvent) and positive controls. In the test each samples (including the controls) were tested in triplicate. The concentrations examined were 5000, 2500, 1000, 316, 100, 31.6 and 10 µg/plate. After 48 hours incubation at 37°C, the plates were scored for revertant colonies and examined for a thinning of the background lawn.

Evaluation criteria:

The study was considered valid if:
- the number of revertant colonies of the negative (solvent) and positive controls were in the historical control range in all strains of the main tests;
- at least five analyzable concentrations were presented in all strains of the main tests.

- Criteria for a Positive Response:
A test item was considered mutagenic if:
- a dose–related increase in the number of revertants occurred and/or;
- a reproducible biologically relevant positive response for at least one of the dose groups occurred in at least one strain with or without metabolic activation.

Criteria for a Negative Response:
A test article was considered non-mutagenic if it produces neither a dose-related increase in the number of revertants nor a reproducible biologically relevant positive response at any of the dose groups, with or without metabolic activation.

Statistics:

No data

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

inhibitory, slightly cytotoxic effect of the test item was observed in all examined bacterial strain +/- S9 during the study.

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: no data

RANGE-FINDING/SCREENING STUDIES: in the range finding test the concentrations examined were 5000, 2500, 1000, 316, 100, 31.6 and 10 µg/plate. The observed numbers of revertant colonies were mostly in the normal range, no insolubility or signs of cytotoxicity were observed. Based on these results, the test item concentrations in the initial mutation test were 5000, 1581, 500, 158.1, 50 and 15.81 µg/plate. Examined concentrations in the confirmatory test were 5000, 1581, 500, 158.1, 50, 15.81, 5 and 1.581 µg/plate.

COMPARISON WITH HISTORICAL CONTROL DATA: the number of revertants colonies was within the historical control range (the initial mutation test, confirmatory mutation test, vehicle and positive controls)

ADDITIONAL INFORMATION ON CYTOTOXICITY: inhibitory, cytotoxic effect of the test item (slightly reduced background lawn development) was observed in the initial mutation test in salmonella typhimurium TA100, TA1535 and TA1537 strains at 5000 µg/plate concentrations with metabolic activation; and in salmonella typhimurium TA100 bacterial strains at 5000 µg/plate concentration without metabolic activation. Similarly, inhibitory, cytotoxic effect of the test item (reduced/slightly reduced background lawn development) was observed in the confirmatory mutation test in all strains at 5000 and 1581 µg/plate concentrations with and without metabolic activation.

Remarks on result:

other: all strains/cell types tested

Table 7.6.1/3: Summary Table of the Initial Mutation Test

Concentrations (µg/plate)	Mean values of revertants / Mutation factor (MF)	Salmonella typhimuriumtester strains								Escherichia coli
		TA98		TA100		TA1535		TA1537		WP2uvrA
		-S9	+S9	-S9	+S9	-S9	+S9	-S9	+S9	-S9	+S9
Untreated control	Mean	22.3	25.3	96.0	103.7	6.7	8.7	9.7	8.0	19.3	37.0
	MF	1.08	0.86	1.26	0.92	0.91	0.68	1.07	0.73	0.84	1.05
Distilled water control	Mean	-	-	87.3	-	8.0	-	-	-	25.0	-
	MF	-	-	1.14	-	1.09	-	-	-	1.09	-
DMSO control	Mean	20.7	29.3	76.3	112.3	7.3	12.7	9.0	11.0	23.0	35.3
	MF	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
5000	Mean	17.0	23.7	62.7	77.7	6.7	7.7	6.7	6.7	21.7	27.3
	MF	0.82	0.81	0.82	0.69	0.91	0.61	0.74	0.61	0.94	0.77
1581	Mean	20.3	23.0	83.3	97.7	7.7	13.7	9.7	10.3	23.7	30.0
	MF	0.98	0.78	1.09	0.87	1.05	1.08	1.07	0.94	1.03	0.85
500	Mean	21.7	27.0	103.3	111.7	8.0	15.3	11.0	11.0	25.0	34.7
	MF	1.05	0.92	1.35	0.99	1.09	1.21	1.22	1.00	1.09	0.98
158.1	Mean	17.7	26.7	118.3	92.7	7.0	10.0	11.0	11.0	24.3	32.0
	MF	0.85	0.91	1.55	0.82	0.95	0.79	1.22	1.00	1.06	0.91
50	Mean	19.3	29.7	98.7	106.3	9.3	10.7	9.7	11.0	26.3	27.3
	MF	0.94	1.01	1.29	0.95	1.27	0.84	1.07	1.00	1.14	0.77
15.81	Mean	17.3	24.7	95.7	112.0	6.0	10.0	10.0	13.0	24.0	26.3
	MF	0.84	0.84	1.25	1.00	0.82	0.79	1.11	1.18	1.04	0.75
NPD (4µg)	Mean	369.7	-	-	-	-	-	-	-	-	-
	MF	17.89	-	-	-	-	-	-	-	-	-
2AA (2µg)	Mean	-	3698.7	-	4240.0	-	258.7	-	233.7	-	-
	MF	-	126.09	-	37.74	-	20.42	-	21.24	-	-
2AA (50µg)	Mean	-	-	-	-	-	-	-	-	-	299.7
	MF	-	-	-	-	-	-	-	-	-	8.48
SAZ (2µg)	Mean	-	-	1153.3	-	1020.0	-	-	-	-	-
	MF	-	-	13.21	-	127.50	-	-	-	-	-
9AA (50µg)	Mean	-	-	-	-	-	-	817.3	-	-	-
	MF	-	-	-	-	-	-	90.81	-	-	-
MMS (2µL)	Mean	-	-	-	-	-	-	-	-	1073.3	-
	MF	-	-	-	-	-	-	-	-	42.93	-

1.   Abbreviations: NPD: 4-nitro-1,2-phenylene-diamine; 2AA:2-aminoanthracene; SAZ: sodium azide;
9AA: 9-aminoacridine; MMS: Methyl-methanesulfonate

2.    Distilled water control was used because of SAZ and MMS

 

Conclusions:

Interpretation of results: negative with and without metabolic activation

Under the test conditions of this study, the test item 1,2-diethoxybenzene had no mutagenic activity in the bacterium tester strains.

Executive summary:

In a reverse gene mutation assay in bacteria (Hargitai, 2012) performed according to the OECD N° 471 guideline and in compliance with GLP,Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA were exposed to the test item 1, 2-diethoxybenzene diluted in DMSO at concentrations ranging from 0 to 5000 µg/plate in the presence and absence of metabolic activation system from liver fraction of phenobarbital/beta-naphthoflavone-induced rats (S9-mix).

The study included a Preliminary Solubility Test, a Preliminary Range Finding Test (Informatory Toxicity Test), an Initial Mutation Test (Plate Incorporation Method) and a Confirmatory Mutation Test (Pre-Incubation Method).

The positive controls induced the appropriate responses in the corresponding strains.

Under the test conditions, 1, 2-diethoxybenzene did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used with and without metabolic activation during the study as there was no evidence of induced mutant colonies over background. Inhibitory, slightly cytotoxic effect of the test item was observed in all examined bacterial strains with and without metabolic activation during the study.

In conclusion, 1,2-diethoxybenzene had no mutagenic activity in the applied bacterium tester strains under the test conditions used in this study.

This study is considered as acceptable as it satisfied the criteria of the OECD guideline N° 471.

Endpoint conclusion

Endpoint conclusion:

no study available (further information necessary)

Additional information

Additional information from genetic toxicity in vitro:

Gene mutation potential:

Two studies were available with reliability 1 and 2 according to Klimisch rating (Kr).

- A study report (Hargitai, 2012) has been chosen as key study for this endpoint (Kr: 1). This study was conducted according to OECD N° 471 and in compliance with GLP. In this study, Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA were exposed to the test item 1, 2-diethoxybenzene diluted in DMSO at concentrations ranging from 0 to 5000 µg/plate in the presence and absence of metabolic activation system from liver fraction of phenobarbital/beta-naphthoflavone-induced rats (S9-mix). The study included a Preliminary Solubility Test, a Preliminary Range Finding Test (Informatory Toxicity Test), an Initial Mutation Test (Plate Incorporation Method) and a Confirmatory Mutation Test (Pre-Incubation Method).

The positive controls induced the appropriate responses in the corresponding strains.

Under the test conditions, 1, 2-diethoxybenzene did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used with and without metabolic activation during the study as there was no evidence of induced mutant colonies over background. Inhibitory, slightly cytotoxic effect of the test item was observed in all examined bacterial strains with and without metabolic activation during the study.

- A study report (Miyaji, 2004) has been chosen as supporting study (Kr: 2). This study was performed similarly to the OECD guideline No. 471 (screening test) but not in compliance with GLP. Only TA100 and TA98 of Salmonella typhimurium strains were exposed to o-Diethoxybenzene diluted in dimethylsulfoxide (DMSO) at concentrations of 0.00(untreated),0.07, 0.21, 0.64, 1.86 and 5.72 mg/plate, in triplicate, both in the presence and absence of mammalian metabolic activation (fraction of S9 from the liver of Sprague-Dawley male rats treated by intraperitoneal injection with Aroclor 1254) .The method of direct incorporation was tested. The dose range determined in a preliminary toxicity assay was 0 to 2.5 mg/plate.

The positive controls produced the expected increases in the number of revertants. The negative control kept up the number of spontaneous revertants within the reversion rate for each strain. The test substance o-Diethoxybenzene did not produce an increase in the number of revertants in the systems with and without metabolic activation system, at any of the studied strains and concentrations when compared with the number of spontaneous revertants of control cultures treated with solvent. These results indicate that, under the test conditions, o-Diethoxybenzene did not exhibit mutagenic activity in the strains of Salmonella typhimurium (TA100 and TA98).

Based on these results, o-Diethoxybenzene was not mutagenic in the bacterial mutation (Ames) test. No other in vitro/in vivo studies were performed with o-Diethoxybenzene.

Justification for classification or non-classification

Based on available results, 1,2- diethoxybenzene is considered as not mutagenic in the bacterial mutation (Ames) test. No other in vitro/in vivo studies were performed, therefore; no classification is possible due to insufficient data.