Titanium oxide sulphate

Endpoint summary

Description of key information

Short description of key information on bioaccumulation potential result: 
Titanium oxide sulphate (TiOSO4) In contact with water is hydrolysed very fast to sulphuric acid and TiO2.There is no potential of bioaccumulation of sulfate. TiO2 particles might accumulate in the lungs and the lymphatic tissues if exposure via the in halation overpowers the clearance mechanism. As this is only to be expected at very high exposure levels, bioaccumulation is not expected under normal exposure conditions.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Summary of the toxicokinetic assessment of Frère 2011:

Titanium oxide sulphate (TiOSO4) is a colourless white solid that is usually produced as a powder. In contact with water titan oxide sulfate is hydrolysed very fast to sulphuric acid and TiO2. Therefore the toxicokinetic assessment focuses on these two species. The assessment does not cover the discussion on the toxicokinetic of TiO2 nanoparticles.

Sulphate stemming from buffering of the sulphuric acid to neutral pH can be absorbed via specialised transport systems in the lungs and the intestine. Skin penetration of ionic substances like sulphate is usually very low, but might be increased through the caustic action of the substance in contact with wet material.

TiO2 particles are poorly soluble so no significant absorption of titanium ions is expected via any of the possible exposure routes. 28 d treatment of rats with a very high dose of 24g/kg bw/d of TiO2 via gavage did not lead to any signs of toxicity indicating that the uptake via the oral route is negligible. Skin penetration of TiO2 particles of the micrometre scale is very unlikely due to the barrier function of the skin. In the lung most TiO2 particles will be transported to the intestine via the mucociliar clearance mechanism. Residual particles are phagocytosed by macrophages and shuttled via the lymphatic system to the liver where they are excreted via the bile. So while they are incorporated they are not truly systemically available. Accordingly they are not metabolised. As an essential ion, absorbed sulphate stemming from sulphuric acid will be included in the physiological processes distributed throughout the organism accordingly, possibly subjected to redox metabolism and finally excreted via the urine.

Therefore there is no potential of bioaccumulation of sulfate. TiO2 particles might accumulate in the lungs and the lymphatic tissues if exposure via the in halation overpowers the clearance mechanism. As this is only to be expected at very high exposure levels, bioaccumulation is not expected under normal exposure conditions.

Supporting information:

This assessment is in line with the statement on the toxicokinetic of TiO2 in the respective REACH dossier of 2011, and is further being supported by the studies of Landford-Pollard 2003 and Midlander 2007.