Trisilicon tetranitride

Endpoint summary

Description of key information

For skin irritation, no symptoms of systemic toxicity were observed and the mean scores for erythema/eschar and oedema were 0 for all rabbits. Therefore, Silicon Nitride is not classified as a skin irritant according to either the CLP Regulation or the Dangerous Substances Directive.

For eye irritation, no symptoms of systemic toxicity were observed. The mean scores calculated for each rabbit were 0 apart from one animal in which conjuntival redness resulted in a score of 0.3.  Silicon Nitride does not meet the criteria for classification as an eye irritant under the CLP Regulation or the DSD.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin Irritation/Corrosion

The key skin irritation/corrosion study was performed with Silicon Nitride according to OECD guideline 404 and in accordance with GLP (ARC Seibersdorf research GmbH, 2005). 0.5 g of Silicon Nitride moistened with deionised water was applied via a patch to a site of 2.5 x 2.5 cm of the intact skin of 3 New Zealand white rabbits and covered by a semi-occlusive dressing. The first animal was exposed to the test substance stepwise at three sites of the skin: Site 1 for 3 minutes, site 2 for 1 hour and site 3 for 3 hours. No serious skin reactions were noted, therefore the remaining two animals were exposed to the test substance one week later for 4 hours. Skin was examined 1, 24, 48 and 72 hours after patch removal at each site. No adverse skin reactions were noted immediately after patch removal. Scores at each site for each animal for erythema/eschar and oedema were 0.0 therefore Silicon Nitride is not classified as a skin irritant.

Eye Irritation

The key eye irritation study was performed with Silicon Nitride according to OECD Guideline 405 and EC method B.5 and in accordance with GLP (ARC Seibersdorf research GmbH, 2005). The approximate equivalent of 0.1 mL of Silicon Nitride was instilled into the conjunctival sac of one eye of each of 3 New Zealand White rabbits. Firstly the substance was administered to one animal. As there was no corrosive or severe irritant effect observed, the test substance was administered to two additional animals one week later. No symptoms of systemic toxicity were observed in the animals during the test period and no mortality occurred. After examination of the eyes after exposure, cornea and irises were not affected. Conjunctivae redness: Some injected blood vessels (score 1) were observed from 1 h post administration (p.a.) onwards until a maximum of 24 h p.a. Conjunctivae chemosis: Very slight (1) or obvious (score 2) swelling was seen in all animals only at 1 h p.a. Ocular discharge was noted in 2/3 animals only 1 h p.a.

The mean scores calculated for each animal from the examinations were 0 in all cases except for one animal which scored 0.3 for conjunctival redness. Therefore Silicon Nitride is not classified for eye irritation.

Justification for selection of skin irritation / corrosion endpoint:

The study was carried out to internationally accepted guidelines and to GLP.

Justification for selection of eye irritation endpoint:

The key study was carried out to internationally accepted guidelines and to GLP.

Justification for classification or non-classification

For skin irritation, no symptoms of systemic toxicity were observed and the mean scores for erythema/eschar and oedema were 0 for all rabbits. Therefore, Silicon Nitride is not classified as a skin irritant according to either the CLP Regulation or the Dangerous Substances Directive.

For eye irritation, no symptoms of systemic toxicity were observed. The mean scores calculated for each rabbit were 0 apart from one animal in which conjuntival redness resulted in a score of 0.3. Silicon Nitride does not meet the criteria for classification as an eye irritant under the CLP Regulation or the DSD.