Zirconium

Endpoint summary

Description of key information

Short description of key information on bioaccumulation potential result: 
Zr metal and salts are poorly absorbed following oral, respiratory or dermal route.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

• Key value for chemical safety assessment

No bioaccumulation potentiel.

 

• Discussion

A qualitative judgement on the toxicokinetic behaviour was performed based on physico-chemical characteristics. Zirconium is an inorganic substance and thus some physico-chemical characteristics (like the octanol/water partition coefficient) are not defined.

Zr metal (and salts) are poorly absorbed following oral, respiratory or dermal route. Gastrointestinal absorption of Zr salts is negligible; parenterally, administrated salts were slowly absorbed.  Absorption factors of 10% should be proposed for oral, inhalation and dermal absorption, representing default values of what is considered still defendable based on the limited physical/chemical data that can be applied for inorganic substances and following the lowest proposed default dermal absorption factor of 10% based on physical/chemical properties (ECHA, 2008). It is recognised that the actual absorption factors for Zirconium will be much lower. Data on Zirconium dichloride oxide in mouse and rat show oral absorption to be at levels of 0.01 to 0.05% of the administered dose (Delongeas JL et al., 1983).

Following inhalation, the main deposition site of Zr particles is the lung. Then, it could be transported in blood to other tissues like the bones. Following intravenous injection, the few amount of Zr absorbed was mainly distributed in soft organs, including liver, ovaries, lung, pancreas, kidney and thymus gland. The higher concentration was found in the ovaries (maximum 8.5 µg Zr/g tissue) and in the liver (maximum 7.1 µg Zr/g tissue).

The few amount of Zr absorbed seems to be excreted mainly through the faeces and in a lesser extent, via the urinary way (< 1 %). Unabsorbed particles are excreted via the urine. Zr was also found in the milk. It seems able to cross the haemato-encephalic barrier and the placenta, and hence could reach the foetus.

ECHA Endpoint specific guidance, Chapter R.7c; section R.7.12.2.1, Dermal absorption. May 2008

Discussion on bioaccumulation potential result:

Zr metal and salts are poorly absorbed following oral, respiratory or dermal route. Gastrointestinal absorption of Zr salts is negligible; parenterally, administrated salts were slowly absorbed.

Following inhalation, the main deposition site of Zr particles is the lung. Then, it could be transported in blood to other tissues like the bones. Following intravenous injection, Zr was mainly distributed in soft organs, including liver, lung, pancreas, kidney and thymus gland, and adipose tissues. The higher concentration was found in the liver and the muscles.

It seems to be excreted mainly through the faeces and, in a lesser extent, via the urinary way (< 1 %). Zr was also found in the milk. It seems able to cross the haemato-encephalic barrier and the placenta, and hence could reach the foetus.