O-isopropyl ethylthiocarbamate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Ames: OECD 471; S, typhimurium TA 1535, TA1537, TA98, TA100 and TA102; no mutagenic
Chromosome aberration: OECD 473; human peripheral blood; no mutagenic
HPRT: OECD 476; Chinese hamster lung fibroblasts (V70); no mutagenic

Link to relevant study records

Reference

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian chromosome aberration test

Species / strain / cell type:

mammalian cell line, other: human peripheral lymphocytes

Details on mammalian cell type (if applicable):

Human peripheral blood was obtained by venipuncture from healthy donors known to be without any medication and collected in heparinised vessels. Small innocula of whole blood (0.5 mL) were added to tubes containing 5 mL of complete culture medium. The tubes were sealed and incubated at 37°C with occasional shaking to prevent clumping.

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Post-mitochondrial fraction (S9 fraction) from rats treated with Aroclor 1254 was prepared according to MARON and AMES (1983). S9 was collected from 20 - 30 rats. The pooled fraction was tested for:

Test concentrations with justification for top dose:

10, 26, 103, 257, 1029 and 2571 µg IPETC per mL medium

Vehicle / solvent:

dimethyl sulfoxide (DMSO)

Untreated negative controls:

yes

Remarks:

DMSO

Negative solvent / vehicle controls:

yes

True negative controls:

yes

Positive controls:

yes

Positive control substance:

mitomycin C

Remarks:

was used as the positive control for the study in the absence of metabolic activation.

Untreated negative controls:

yes

Remarks:

DMSO

Negative solvent / vehicle controls:

yes

True negative controls:

yes

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

was used as the positive control for the study in the presence of metabolic activation.

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION

- Exposure duration: 4 hours in experiment 1 and 24 hours in experiment 2

SPINDLE INHIBITOR (cytogenetic assays): colcemid® to accumulate cells in a metaphase-like stage of mitosis (c-metaphase).

Evaluation criteria:

The test item is judged to have mutagenic properties with respect to chromosomal or chromatid change, if the following criteria are fulfilled:
o the number of chromosomal aberrations is significantly increased compared with the solvent control
o the increase observed is concentration-dependent
o both duplicate cultures lead to similar results
o the increase should not occur in the severely cytotoxic range (mitotic index <0.25), as it is known that high cytotoxicity causes artefacts in the form of aberrations in in vitro chromosomal aberration tests
o a reproducible increase in the number of cells with chromosomal aberrations.

Statistics:

The assessment was carried out by a comparison of the number of chromosome aberrations of the samples with those of the solvent control, using the exact test of R. A. FISHER as recommended by the UKEMS guidelines (The United Kingdom Branch of the European Environmental Mutagen Society: Report of the UKEMS subcommittee on guidelines for mutagenicity testing, part III, Statistical evaluation of mutagenicity test data, 1989).

Key result

Species / strain:

mammalian cell line, other: human peripheral lymphocytes

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

cytotoxicity was noted in the experiment without and with metabolic activation (24-h or 4-h exposure, respectively) starting at 1029 µg IPETC /mL. Haemolysis was noted at concentrations of 2571 and 5143 µg/mL in both experiments.

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: strain/cell type: human peripheral lymphocytes

Remarks:

Migrated from field 'Test system'.

Conclusions:

Under the present test conditions, IPETC, tested up to cytotoxic concentrations, in the absence and in the presence of metabolic activation employing two exposure times (without S9) and one exposure time (with S9) revealed no indications of mutagenic properties with respect to chromosomal or chromatid damage.
In the same test, Mitomycin C and cyclophosphamide induced significant damages, which confirmed the validity of this assay.

Executive summary:

The registered substance was tested for its potential to induce chromosome aberrations in an Chromosome Aberration study in mammalian cells (human peripheral lymphocytes) according to OECD Guideline 473 with and without metabolic activation.
Under the present test conditions, IPETC, up to cytotoxic concentrations, in the absence and in the presence of metabolic activation employing two exposure times, revealed no indications of mutagenic properties with respect to chromosomal or chromatid damage. In the test, Mitomycin C and cyclophosphamide induced significant damages, which confirmed the validity of this assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Ames test

The registered substance was tested for its mutagenicity in an Ames plate incorporation Assay and preincubation assay according to OECD Guideline 471, under GLP in Salmonella typhimurium strains TA 98, TA 100, TA 102, TA 1535 and TA 1537 with and without metabolic activation.
Under the present test conditions IPETC tested up to a cytotoxic concentration of 3250 µg IPETC /plate, caused no mutagenic effect in the Salmonella typhimurium strains TA 98, TA 100, TA 102, TA 1535 and TA 1537 neither in the plate incorporation test nor in the preincubation test each carried out without and with metabolic activation.

Chromosome aberration

The registered substance was tested for its potential to induce chromosome aberrations in an Chromosome Aberration study in mammalian cells (human peripheral lymphocytes) according to OECD Guideline 473 with and without metabolic activation.
Under the present test conditions, IPETC, up to cytotoxic concentrations, in the absence and in the presence of metabolic activation employing two exposure times, revealed no indications of mutagenic properties with respect to chromosomal or chromatid damage. In the test, Mitomycin C and cyclophosphamide induced significant damages, which confirmed the validity of this assay.

HPRT

The substance was tested in an HPRT-V79 mammalian cell mutagenicity test according to OECD Guideline 476 and under GLP, with and without metabolic activation in Chinese hamster lung fibroblasts. Under the present test conditions, IPETC tested up to the cytotoxic concentrations caused no mutagenic effects in  Chinese hamster lung fibroblasts (V79) without and with metabolic activation. Positive controls exerted potent mutagenic effects.

 

Justification for classification or non-classification

Based on the negative results of three valid in vitro tests with the test substance, the substance does not need to be classified according to the criteria of Classification, Labelling and Packaging of Substances and Mixtures Regulation (EC) No 1272/2008 (CLP Regulation).