Diiron titanium pentaoxide

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

other: solubility in gastric and intestinal juices

Qualifier:

no guideline available

GLP compliance:

no

Radiolabelling:

no

Conclusions:

From this in vitro assay on the solubility of iron from pearlescent pigments in artificial gastric and intestinal juices, the bioavailability is expected to be very low after oral ingestion.

Executive summary:

The test item was incubated with artificial gastric or intestinal juice at 37°C for 2 and 10 hours, respectively. Subsequently the filtrates of these incubations were analyzed for iron using flame atom absorption spectroscopy (F-AAS). The content of soluble iron after incubation with artificial intestinal juice was below the limit of quantification of < 1.5 ppm. After incubation with artificial gastric juice a maximum content of soluble iron of 0.013 % was determined. Based on this study, the bioavailability of iron and, thus, of the test item from the pigments after oral ingestion is considered to be extremely low.

Description of key information

Diiron titanium pentaoxide is an inorganic solid with a molecular weight of 240 g/mol. The water solubility of TiFe2O5 is with very low. The concentrations of Fe and Ti after 28 d long term dissolution/transformation test are assumed as worst case values. They are 2.715 ± 1.506 µg Fe/L and 1.156 ± 0.497 µg Ti/L. No melting or boiling point was observed up to 500°C. The maximum of the mono-modal particle size distribution was observed at approximately between 10 µm and 20 µm. The D10, D50 and D90 percentile were determined as L10 = 7.07 µm, L50 = 13.1 µm and L90 = 22.9 µm, respectively. Considering these physico-chemical properties, dermal and oral/GI absorption can be excluded. This assumption is supported by an in vitro assay on the solubility of iron from pearlescent pigments in artificial gastric and intestinal juices. Based on the low water solubility, but mainly based on the absence of target organs or signs of toxicity in repeated dose toxicity studies, distribution was considered minimal. No substantial accumulation was observed in tissues following oral administration of the pigment containing diiron titanium pentaoxide up to a 13.5%. Based on the particle size of 10 - 20 µm, particles could reach the alveolar region of the respiratory tract after inhalation. However, for poorly water-soluble dusts, the rate at which the particles dissolve into the mucus will limit the amount that can be absorbed directly. The tendency of particles to agglomerate and deposit do not favor the respiratory uptake. Furthermore, in an acute inhalation toxicity study according to OECD TG 403, adverse effects have been observed only at massive overload (at 14600 mg/m3). No effects are expected at the limit dose recommended by the current OECD guideline (i.e. 2000 mg/m3). The test material is considered not toxic after acute inhalation. It is expected that excretion of the substance after oral exposure occurs mainly via faeces, since silver-coloured faeces have been reported in repeated-dose studies with the pigment.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential