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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
no data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Meets generally accepted scientific standards, well documented and acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1988

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
An Ames test with three hundred chemicals was performed applying the pre-incubation method.
GLP compliance:
no
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
- Name of test material (as cited in study report): Titanium dioxide
- Substance type: inorganic
- Physical state: solid
- Analytical purity: 98.5 %

Method

Target gene:
One of the genes comprising the his-operon involved in histidine synthesis
Species / strain
Species / strain / cell type:
other: TA97, TA98, TA100, TA1535, TA1537
Details on mammalian cell type (if applicable):
- Type and identity of media: Oxoid No. 2 broth; Vogel-Bonner medium (Vogel and Bonner, 1956) was used for the preincubation assay.
- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: n.a.
- Periodically checked for karyotype stability: n.a.
- Periodically "cleansed" against high spontaneous background: n.a.
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
S9 fractions of Aroclor 1254-induced
Test concentrations with justification for top dose:
The concentrations tested were reported as follows:
Each chemical was tested initially at half-log dose intervals up to a dose that elicited toxicity, or to a dose immediately below one which was toxic in the preliminary toxicity test. Subsequent trials occasionally used narrower dose increments and may not have included doses in the toxic range. Chemicals that were not toxic were tested, with few exceptions, to a maximum dose of 10 mg/plate.
Vehicle / solvent:
Water
Controls
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; 2-aminoanthracene
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium; in agar (plate incorporation); preincubation; in suspension; as impregnation on paper disk

DURATION
- Preincubation period: The test chemical (0.05 ml), Salmonella culture (0.10 ml), and S-9 mix or buffer (0.50 ml) were incubated at 37°C, without shaking, for 20 min.
- Exposure duration: incubation time 2 days
- Expression time (cells in growth medium): same as exposure time
- Selection time (if incubation with a selection agent): same as exposure time;
- Fixation time (start of exposure up to fixation or harvest of cells): n.a.

SELECTION AGENT (mutation assays): absence of histidine;
SPINDLE INHIBITOR (cytogenetic assays): n.a.
STAIN (for cytogenetic assays): n.a.

NUMBER OF REPLICATIONS: no data

NUMBER OF CELLS EVALUATED: n.a.; the colonies able to grow on meidum lacking histidine were counted

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; cloning efficiency; relative total growth; other: cloning efficiency

OTHER EXAMINATIONS:
- Determination of polyploidy: n.a.
- Determination of endoreplication: n.a.
Evaluation criteria:
The data were evaluated as described previously (Zeiger et al., 1987). Evaluations were made at both the individual trial and overall chemical levels. Individual trials were judged mutagenic ( +), weakly mutagenic ( +W), questionable (?), or nonmutagenic ( -), depending on the magnitude of the increase of his + revertants, and the shape of the dose-response.
Statistics:
no data

Results and discussion

Test results
Species / strain:
other: TA97, TA98, TA100, TA1535, TA1537
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
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative

Based on the results of an Ames test Titanium Dioxide is considered to be not a mutagenic substance.
Executive summary:

In a reverse gene mutation assay in bacteria, strains TA97, TA98, TA100, TA1535, and TA1537 ofS. typhimuriumwere exposed to altogether 300 chemical, among them Titanium Dioxide in concentrations not clearly specified. Each chemical was tested initially at half-log dose intervals up to a dose that elicited toxicity, or to a dose immediately below one which was toxic in the preliminary toxicity test. Subsequent trials occasionally used narrower dose increments and may not have included doses in the toxic range. Chemicals that were not toxic were tested to a maximum dose of 10 mg/plate. Each chemical was tested in the absence and in the presence of the metabolic activator S9 applying the pre-incubation method.

Appropriate positive and negative controls showed the expected responses in the corresponding strains.The results of a study from Dunkel et al. (1985) which are also cited by the NTP (National Toxicology Program) could be confirmed. Titanium Dioxide is not considered to be mutagenic in the Ames test.There wasno evidenceof induced mutant colonies over background reported.