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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:
key study
Study period:
No data reported
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study is classified as reliable without restriction because it was carried out in a method similar to OECD TG 471 with modifications.
Justification for type of information:
The standard OECD 471 test is not suitable to test petroleum UVCBs, because it has a tendency to produce false negatives for these substances. Therefore, the petroleum industry has developed a Modified Ames assay, optimized to accurately identify positive results for this endpoint. This deviation from the prescribed testing procedure requires some further explanation which is given in the attached document. The document gives a brief history of the development of the Modified Ames test and outlines Concawe’s proposed work (as part of a wider testing strategy, see Annex 13) to further support the use of this test for PS.

Data source

Reference
Reference Type:
publication
Title:
Estimation of the dermal carcinogenic activity of petroleum fractions using a modified Ames assay
Author:
Blackburn GR, Deitch RA, Schreiner CA, Mehlman MA, and Mackerer CR
Year:
1984
Bibliographic source:
Cell Biol Toxicol, Vol 1(1), pp 67-80

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
with modifications
Principles of method if other than guideline:
Method: other: procedure described in paper by Blackburn et al. The light paraffinic distillate was extracted with dimethylsulphoxide by performing five successive one-to-one extractions and pooling extracts. The pooled extract sample was stored at 4 degrees celsius in an amber bottle until assayed.
GLP compliance:
not specified
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Test material form:
other: Oily liquid
Details on test material:
Test substance:
Sample number 3 CAS 64741-50-0

Method

Target gene:
Not applicable
Species / strain
Species / strain / cell type:
other: Modified Ames Test using Salmonella typhimurium strain TA 98 and Aroclor 1254-induced rat or hamster liver S-9
Details on mammalian cell type (if applicable):
Not applicable
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with
Metabolic activation system:
Aroclor 1254-induced rat or hamster liver S9
Test concentrations with justification for top dose:
range of doses that provided an initial linear dose response; specific doses not stated.
Vehicle / solvent:
No data reported.
Controls
Untreated negative controls:
not specified
Negative solvent / vehicle controls:
not specified
True negative controls:
not specified
Positive controls:
yes
Remarks:
benzo(a)pyrene at 5 ug/plate and 2-aminoanthracene at 2 ug/plate
Positive control substance:
not specified
Details on test system and experimental conditions:
The light paraffinic distillate was extracted with dimethylsulphoxide by performing five successive one-to-one extractions and pooling extracts. The pooled extract sample was stored at 4 degrees celsius in an amber bottle until assayed.
Evaluation criteria:
A tangent to the dose-response curve at zero dose was constructed to provide the Mutagenicity Index.
Statistics:
A tangent to the dose-response curve at zero dose was constructed to provide the Mutagenicity Index.

Results and discussion

Test results
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with
Genotoxicity:
positive
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
not specified
Untreated negative controls validity:
not specified
Positive controls validity:
valid
Remarks on result:
other:
Remarks:
Migrated from field 'Test system'.

Any other information on results incl. tables

The test substance was not mutagenic in standard assay, but extraction with DMSO produced a mutagenic response.  The mutagenicity index was 17.  This compares with values of 0 for a solvent refined oil and 40 for a cracked distillate.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
positive with metabolic activation

DMSO-extracted light paraffinic distillate was classified as mutagenic and produced a mutagenicity index of 17. Assay sensitivity (the number of TA98 revertants per plate) improved with 8-fold increase of S9.
Executive summary:

In a modified in vitro mutagenicity assay, S. typhimurium strain TA98 was exposed to a DMSO-extracted light paraffinic distillate at a concentration of 50 microlitres per plate with metabolic activation (Aroclor 1254 -induced rat or hamster liver S9) using the standard pre-incubation method. The test substance was considered mutagenic and produced a mutagenicity index of 17. This study received a Klimisch score of 1 and is classified as reliable without restriction because it was carried out in a method similar to OECD TG 471 with modifications.