Yttrium oxide (Y2O3), europium-doped

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

other: theoretical assessment

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Toxicokinetic assessment based on available information from the open literature as well as on the physico-chemical properties of the substance.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Objective of study:

absorption

Principles of method if other than guideline:

Based on REACH guidance IR CSA R.7, the toxicokinetic assessment is based on available information from the open literature as well as on the physico-chemical properties of the substance.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Yttrium oxide (Y2O3), europium-doped

EC Number:

271-591-2

EC Name:

Yttrium oxide (Y2O3), europium-doped

Cas Number:

68585-82-0

Molecular formula:

Y2O3:Eu

IUPAC Name:

Yttrium trioxide, Europium doped

Test material form:

solid

Results and discussion

Main ADME results

Type:

absorption

Results:

For risk assessment purposes, the oral and dermal absorption is derived to be 10% and the inhalation absorption is derived to be 100%.

Any other information on results incl. tables

A substance can enter the body via the lungs, the gastrointestinal tract, and the skin. To determine the absorption rate, the different routes need to be assessed individually. In general, a compound needs to be dissolved before it can be taken up from the gastro-intestinal tract after oral administration. Yttrium Oxide, Europium-Doped is considered to be insoluble in water. Thus, the water insolubility can be considered a potentially rate-limiting factor for the absorption of the compound. Although the molecular weight of this substance is favorable for absorption, it is unlikely that Yttrium Oxide, Europium-Doped will show a high systemic exposure after oral administration. In the presence of food and bile salts some systemic exposure might be possible. In a study with radioactive Yttriumchloride, tissue distribution was studied after oral administration. The uptake of Yttrium was very low in tissues outside the gastrointestinal tract, indicating some but poor absorption of this isotope from the intestine. Although similar behavior of YCl₃and Y₂O₃can be expected, these data should only be used as an indication for the behavior.

Based on the available data, for risk assessment purposes the oral absorption of Yttrium Oxide, Europium-Doped is set at 10% as a worst case assumption.

Once absorbed, distribution of Yttrium Oxide, Europium-Doped throughout the body will be limited due to its water insolubility. The Y³⁺-ion is a strong Lewis base, and it can therefore form colloids with proteins. Indeed, Yttriumchloride has been shown to bind to glycoprotein from bovine cortical bone in vitro and to deposit in the bones of growing rats. However, the amounts were either not quantified or yttrium did not accumulate in large amounts. It is of note that these data were not obtained from studies with Yttriumoxide and since the precise mode of action is not known it is not clear whether Yttriumoxide behaves in a similar way as Yttriumchloride. Taking all available data into account, it can be concluded that the bioaccumulation potential of Yttrium Oxide, Europium-Doped is expected to be low.

Since Yttrium Oxide, Europium-Doped has a boiling point above 150°C, a low vapour pressure can be assumed and therefore this substance is not available for inhalation as a vapour. Based on the particle size distribution study performed with Yttrium Oxide, Europium-Doped, particles < 100 μm which have a potential to be inhaled, are present. Particles with an aerodynamic diameter below 50 μm may reach the thoracic regions, whereas particles with an aerodynamic diameter below 15 μm may reach the alveolar region of the respiratory tract. The water insolubility of Yttrium Oxide, Europium-Doped indicates that the substance will not dissolve into the mucus lining of the respiratory tract, which will limit the amount that can be absorbed directly. Poorly water-soluble particles depositing in the alveolar region will mainly be engulfed by alveolar macrophages. The macrophages will then either translocate particles to the ciliated airways or carry particles into the pulmonary interstitium and lymphoid tissues. As most of the particles have a size < 10 μm (99.93%), the fraction that will reach the alveolar region of the respiratory tract will be available for absorption. For risk assessment purposes the inhalation absorption of Yttrium Oxide, Europium-Doped is set at 100%.

Yttrium Oxide, Europium-Doped is a solid which is considered to be insoluble in water and has therefore no real potential for dermal absorption. Its moderate molecular weight above 100 g/mol favors dermal absorption. Based on these physical/chemical properties of Yttrium Oxide, Europium-Doped, dermal absorption is considered to be low. Since the criteria for 10% dermal absorption as given in the REACH guidance (MW > 500 and log Pow < -1 or > 4 are not met, 100% dermal absorption should be considered for dermal absorption.

However, as it is general accepted that dermal absorption does not exceed oral absorption, for risk assessment purposes 10% dermal absorption of Yttrium Oxide, Europium-Doped as default value is considered to be more appropriate.

Based on its physical/chemical properties, absorption factors for Yttrium Oxide, Europium-Doped are derived to be 10% (oral), 100% (inhalation) and 10% (dermal) for risk assessment purposes. The bioaccumulation potential of Yttrium Oxide, Europium-Doped is expected to be low.