boron nitride (cubic)

Endpoint summary

Description of key information

Cubic boron nitride is not bioavailable (and not systemically available) and therefore not acute toxic. Limit tests on oral and dermal toxicity resulted in LD50 values > 2000 mg/kg bw. cBN was further not toxic in an inhalation study (5.20 mg/L).

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Dose descriptor:

LC50

Value:

5.2 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Additional information

Due to its physico-chemical characteristics (inert substance, insoluble in water, does not cross biological membranes) it can be inferred that the substance is unlikely to be taken up into the blood stream because of its low bioavailability. Therefore, cBN is not systemically available, which is further supported by oral, inhalation and dermal studies conducted with cBN (see chapters 7.2.1, 7.2.2 and 7.2.3 of the IUCLID dossier). In standard OECD tests 423 and 402 cBN exhibited no acute orally toxic characteristics and no acute dermal toxic characteristics when applied to rats at a concentration of 2,000 mg/kg body weight. The negative results of an in vitro Cytotoxicity Assay (see section 7.12 of the IUCLID dossier) and the absence of cytotoxic effects in a pre-incubation test (Ames Test) with several Salmonella typhimurium strains (see section 7.6.1 of the IUCLID dossier) performed with an extract of cBN powder (200 g/L) underline the conclusion that cBN is not bioavailable (and not systemically available) due to its insolubility in water.