Titanium nitride

Endpoint summary

Description of key information

There is no study available elucidating the skin sensitization potential of titanium nitride itself. Therefore, a skin sensitization study conducted with the poorly soluble titanium carbide was used to assess this endpoint in a read-across approach.

The skin sensitising properties of titanium carbide were tested in an in vivo local lymph node assay (OECD 429), in which test item did not show skin sensitising effects.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Positive control results:

The positive control induced an appropriate response (Mean Stimulation Index: 10.7).

Parameter:

SI

Value:

1.8

Test group / Remarks:

Concentration: 12.5 %

Remarks on result:

other: respectively Positive control: 10.7

Parameter:

SI

Value:

1.7

Test group / Remarks:

Concentration: 25 %

Remarks on result:

other: respectively Positive control: 10.7

Parameter:

SI

Value:

1.9

Test group / Remarks:

Concentration: 50 %

Remarks on result:

other: respectively Positive control: 10.7

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: negative control: 552.1 ± 58.8, positive control: 9563.2 ± 756.2 test group: 1002.1 ± 328.2, 936.4± 22.5, 1048.1 ± 155.5

No effects were observed on the body weights and the lymph node weights of the animals tested with titanium carbide. No other signs of toxicity were seen in any of the animals.

Table 1: Mean weight of lymph nodes.

Group	Mean of test group
12.5% TiC in vehicle	3.2
25% TiC in vehicle	3.0
50% TiC in vehicle	3.3
Negative control	2.8

Interpretation of results:

GHS criteria not met

Conclusions:

Titanium carbide is not sensitizing to the mouse skin under the conditions of this LLNA study.

Executive summary:

In this dermal sensitization study with titanium carbide in acetone/olive oil 4:1 (v/v), young adult female CBA/CaOlaHsD mice were tested using the Local Lymph Node Assay (LLNA). 25 µl of the test substance in solvent were applied on the entire dorsal ear surface of each animal. The following concentrations were used: 12.5, 25 and 50%. Acetone/olive oil 4:1 was used as negative control. Phenylenediamine was tested as a positive control in a prior assay. The application was repeated daily for three consecutive days. The doses applied were selected based on a pre-screening assay. Five days after the 1st application 250 µL 20 µCi 3H-methyl thymidine was injected intravenously to all mice (diluted concentration: 80 µCi/mL). All animals were sacrificed five hours after the aforementioned injection. The draining ear lymph nodes were excised into PBS and single cell suspension of lymphocyte was isolated. Cells were precipitated with 5% trichloroacetic acid at 4 °C for 18 hours.The radioactivity was measured in a ß-counter.

Stimulation indices (ratio of 3H-methyl thymidine incorporation into lymph node of test animals relative to that for control animals)≥ 3 were considered a positive response. The results revealed the following SI: 1.8, 1.7 and 1.9 for the concentrations of 12.5, 25 and 50%, respectively. No signs of toxicity were detected in any of the treated animals. In this study, Titanimum carbide is not a dermal sensitizer.

This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

No data is available for titanium nitride (target substance). Thus, available data from titanium carbide (source substance) is used to assess the sensitizing potential of titanium nitride. The nitride component of titanium nitride is considered to be of minor impact and negligible for the assessment of the acute toxicity. Titanium nitride and titanium carbide showed both a very low bioaccumulation potential as tested in artificial perspiration fluid. Due to the very low potential of bioaccessibility of both compounds the read across is appropriate and the resulting toxicity potential would also be expected to be similar. Details on the read-across rationale are provided in section 13.

Titanium carbide was tested negative in a dermal sensitization study according to OECD 429. Based on the results from the read-across partner titanium carbide, titanium nitride can be considered as not sensitizing to the skin.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The results of a valid OECD 429 assay (LLNA) with titanium carbide did not show skin sensitising effects. Based on the results from this read-across approach, classification of titanium nitride according to Regulation (EC) No. 1272/2008 is not warranted.