Titanium oxide sulphate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

other: expert statement

Adequacy of study:

key study

Study period:

2011-05-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Comparable to guideline study. The expert statement covers the toxicokinetic behaviour of parent compound titanium oxide sulphate and final hydrolysis product titanium dioxide. Target compound titanium oxide sulphate hydrolyses easily when in contact with wet material to form titanium dioxide (TiO2). Therefore the toxicokinetic consideration can focus on the behaviour of titanium dioxide (TiO2).

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other:

Deviations:

not applicable

Principles of method if other than guideline:

The attached Toxicokinetic Assessment is meant to fulfill the requirement as defined in the REGULATION (EC) No 1907/2006 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 18 December 2006 requests in Annex VIII, point 8.8.1:
"Assessment of the toxicokinetic behaviour of the substance to the extent that can be derived from the relevant available information."

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Titanium oxide sulphate

EC Number:

237-523-0

EC Name:

Titanium oxide sulphate

Cas Number:

13825-74-6

Molecular formula:

O5STi

IUPAC Name:

Titanium(IV) Oxysulfate

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): no bioaccumulation potential based on study results
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.

Executive summary:

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.