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Administrative data

Key value for chemical safety assessment

Additional information

Gene mutation potential:

In vitro Bacterial mutagenicity (Ames Test)

THPC-Urea-Amine concentrate has been evaluated in a bacterial mutagenicity assay (OECD 471) using five strains of Salmonella typhimurium (TA1535, TA1537, TA98, TA100, TA 102).

 

In three separate experiments, the test substance did not induce any significant, reproducible increases in the observed numbers of revertant colonies in all strains with or without an auxiliary metabolising system (S9).

Under the conditions of this assay, THPC-Urea-Amine concentrate gave a negative, i.e. non-mutagenic, response in all S. typhimurium strains tested.

 

In vitro Clastogenic Potential:

No study on in vitro cytogenetic potential is available however this endpoint is covered by an in vivo mouse micronucleus test.

 

In vitro mammalian cell mutagenicity

THPC-Urea-Amine concentrate was tested in the L5178Y TK +/- mouse lymphoma gene mutation assay (OECD 476) in one experiment in the presence of an auxiliary metabolising system (S9) and in the absence of S9, all at a 48-hour expression time. The maximum concentration tested (62.5 μg/ml) was limited by the toxicity of the test substance.

Treatment with the test substance produced statistically significant, dose-related increases in mutant frequency both in the presence and absence of S9-mix. THPC-Urea-Amine was considered to be mutagenic to L5178Y TK+/- cells both in the presence and in the absence of S9 -mix when tested up to a concentration (62.5 μg/ml) limited by the toxicity of the test sample.

 

In vivo Mutagenicity

THPC-urea-amine was assessed in the in vivo UDS assay (OECD 486) for its potential to induce DNA repair (UDS) in the hepatocytes of rats. The test substance was formulated in deionised water, which was used as the vehicle control. The test substance was administered orally by gavage at 175 and 350 mg/kg bw (the maximum tolerated dose). After a treatment period of 2 and 16 hours respectively, the animals were anaesthetised and sacrificed by liver perfusion. Primary hepatocyte cultures were established and exposed for 4 hours to3HTdR (methyl-3H-thymidine).

The viability of the hepatocytes was not substantially affected by the in vivo treatment with the test substance at any of the treatment periods or dose groups. The inter-individual variations obtained for the numbers and the viabilities of the isolated hepatocytes were in the range of historical controls.

No dose level of the test substance revealed UDS induction in the hepatocytes of the treated animals compared to the current vehicle controls. Neither the nuclear grains nor the resulting net grains were distinctly enhanced due to the in vivo treatment of the animals with the test substance for 2 hours or 16 hours. Therefore the net grain values obtained after treatment with the test substance were consistently negative. No substantial shift to higher values was obtained in the percentage of cells in repair. Appropriate reference mutagens revealed distinct increases in the number of nuclear and net grain counts.

It was concluded that under the experimental conditions reported, the test substance did not induce DNA damage leading to increased repair synthesis in the hepatocytes of the treated rats.

Based on these results, THPC-urea-amine is considered as not mutagenic.

In vivo Clastogenic Potential:

ITC 826 concentrate was evaluated for its ability to induce micronucleated polychromatic erythrocytes in the bone marrow of CD-1 mice (OECD 474). A single oral dose was given to groups of 5 male mice at a dose level of 200 mg/kg and to groups of 5 female mice at a dose level of 320 mg/kg. In each case the dose level used represented the maximum tolerated dose (MTD). Bone marrow samples were taken 24 and 48 hours after dosing.

No statistically or biologically significant increases in the incidence of micronucleated polychromatic erythrocytes, over the control values, were seen in males at the 24 hour sampling time or in either males or females at the 48 hour sampling time. Although a small but statistically significant increase in the incidence of micronucleated polychromatic erythrocytes, compared to the vehicle control, was observed at the 24 hour sampling time in females dosed at 320 mg/kg, this was not reproduced in an extended analysis of a further 2000 polychromatic erythrocytes and is therefore considered of no biological significance.

Comparison of the percentage of polychromatic erythrocytes showed no statistically or biologically significant differences in either sex at either of the sampling times between the vehicle control animals and those treated with the test substance.

Under the conditions of the test, ITC 826 Concentrate is not clastogenic in the mouse bone marrow micronucleus test.

Based on these results, THPC-urea-amine is considered as not clastogenic.


Justification for selection of genetic toxicity endpoint
No study was selected. Based on the results of the in vivo studies, the product is considered as not genotoxic.

Short description of key information:
Two in vitro and two in vivo genotoxicity studies are considered to be key studies covering the mutagenic and clastogenic endpoints of genotoxicity.
An Ames test (Simar, 2015; OECD 471, Rel. 1) showed no mutagenic effect of the substance in the 5 strains of S. typhimurium strain. The L5178Y TK +/- mouse lymphoma gene mutation assay (OECD 476; Simar, 2015, Rel. 1) gave a positive result in both metabolic conditions. This last in vitro study suggest that THPC-urea-amine could have some genotoxic potential.
A mouse micronucleus test in vivo (Mackay, 1996; OECD 486, Rel. 1) and a UDS test in rat hepatocytes in vivo (Honarvar, 2005; OECD 474, Rel. 1) both gave negative results. These two in vivo studies clarify that THPC-urea-amine does not have genotoxic potential in vivo.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on absence of mutagenicity in the UDS study in vivo and absence of clastogenicity in a mouse micronucleus study in vivo, it is concluded that the THPC-urea-amine is not genotoxic. Therefore no classification is required according to the EU legislation (Directive 67/548/EEC and CLPregulation (1272/2008)).