Zirconium

Endpoint summary

Description of key information

One study is available for acute toxicity via the oral route of exposure (according to OECD 423): the LD50 is > 2000 mg/kg (rat) and the LD50cut off is > 5000 mg/kg.
No reliable data is available for acute toxicity via the inhalation route of exposure. As Zr powder is pyrophoric, it is not technically possible to generate an inhalable test atmosphere.  Based on the same behaviour and toxicological effects, a read across with ZrO2 is performed. No toxic effect is observed in the available study, the LC50 is therefore > 4.3 mgZrO2/L or >3.18 mg eq Zr/L

Additional information

• Oral toxicity

One reliable test is available to assess the oral acute toxicity of Zr (Klimisch 1). This study has been performed according to the OECD guideline 423 where the rats exposed received an unique dose of 2000 mg/kg Zr. No mortality was observed during the test and during the 14 days of observation. Zr is not toxic, its LD50 is higher than 2000 mg/kg and the LD50cut off is higher than 5000 mg/kg.

 

• Inhalation toxicity

For inhalation acute toxicity, as this test is technically impossible, a read across with ZrO2 is realised. Indeed, according to the REACh recommendations, a read across could be used for substances with similar behaviour and toxic effects in the organism. An OECD guideline 436 was available: 3 male and 3 female were exposed nose-only to 4.3 mg/L of ZrO2 for 4 hours. The mean mass median aerodynamic diameter was 2 µm (+/- 1.75 µm). With this particle size, ZrO2 could reach lower parts of respiratory tract, like the bronchioles. No mortality was observed during the test, all animals were considered clinically normal and no macroscopic findings were noted at the scheduled necropsy. All animals lost weight from study day 0 to 1; one male showed a slight loss of weight between day 1 and 3.The CL50 equivalent for Zr was 3.18 mg/L.

Justification for classification or non-classification

Regarding inhalation, taking into account the LC50 strictly higher than 3.18 mg Zr/L (the maximum obtainable mean concentration), the inert form of the substance and its capacity to reach lower parts of the respiratory tract (ZrO2 granulometry < 4 µm), Zr was not classified under the CLP regulation 1272/2008 and the directive Classification and Labelling 67/548.

Based on the available oral and dermal data, the substance was not classified under the CLP Regulation 1272/2008 and the directive Classification and Labelling 67/548.