Dioxybenzone

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study under GLP conditions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

GLP compliance:

yes (incl. QA statement)

Remarks:

2007-10-15

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Dioxybenzone

EC Number:

205-026-8

EC Name:

Dioxybenzone

Cas Number:

131-53-3

Molecular formula:

C14H12O4

IUPAC Name:

2-(2-hydroxybenzoyl)-5-methoxyphenol

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

Name: 2,2'-Dihydroxy-4-methoxybenzophenone (CAS 131-53-3)
Description: Yellow solid
Batch number: 8010111
Storage conditions: Room temperature in the dark

Method

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:

S9-mix

Test concentrations with justification for top dose:

Based on a preliminary toxicity test using TA100 and E.coli, the following dose levels were used:
Salmonella strains, with and without S9: 5, 15, 50, 150, 500 and 1500 µg/plate
E. coli WP2vurA-, with and without S9: 15, 50, 150, 500, 1500 and 5000 µg/plate

Vehicle / solvent:

- Vehicle/solvent used: DMSO
- Justification for choice of solvent/vehicle: The test material was insoluble in sterile water at 50 mg/ml but soluble in dimethyl sulphoxide at the same concentration in solubility checks performed in-house.

Controls

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

9-aminoacridine

N-ethyl-N-nitro-N-nitrosoguanidine

benzo(a)pyrene

other: 2-Aminoanthracene

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar; Direct plate incorporation method for the range-finding test and the main test

DURATION
- Exposure duration: 48h

NUMBER OF REPLICATIONS:
3 replicates per bacterial strain and concentration

The frequency of revertant coloniges was assessed using a Domino colony counter.

Rationale for test conditions:

Range-finding study

Evaluation criteria:

There are several criteria for determining a positive result, such as a dose-related increase in revertant frequency over the dose range tested and/or a reproducible increase at one or more concentrations in at least one bacterial strain with or without metabolic activation. Biological relevance of the results is considered first, statistical methods, as recommended by the UKEMS can also be used as an aid to evluation, however, statistical significance will not be the only determining factor for a positive response.
A test material will be considered non-mutagenic (negative) in the test system if the above criteria are not met.

Results and discussion

Test results

Species / strain:

other: All strains

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Results for the negative controls were considered as acceptable. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies thus confirming the activity of the S9-mix and the sensitivity of the bacterial strains.

The test material was initially toxic from 500 and 1500 µg/plate to the strains of bacteria used, TA100 and WP2uvrA-, respectively.

The test material caused a visible reduction in the growth of the bacterial background lawns of all the tester strains both with and without metabolic activation, initially from 500 µg/plate. The test material was, therefore, tested up to either the maximum recommended dose level of 5000 µg/plate or the toxic limit, depending on the bacterial strain type.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, at any dose level either with or without metabolic activation.

Applicant's summary and conclusion

Conclusions:

The test is negative, the test item is not mutagenic to bacteria.

Executive summary:

2,2'-Dihydroxy-4 -methoxybenzophenone has been tested according to OECD 471 and under GLP. No increase in the number of revertants was observed for the test substance tested up to cytotoxic or limit concentrations in any of the test strains either with or without metabolic activation. It is concluded that the test substance is not mutagenic to bacteria under the conditions of the test.