Registration Dossier

Diss Factsheets

Administrative data

Link to relevant study record(s)

Description of key information

In consideration of its variable elemental compositions, animal testing on the UVCB as such is unlikely to reflect the full scheme of variations in case only a limited number of samples can be tested. For the sake of animal welfare, the toxicokinetics, metabolism and distribution are considered driven by the characteristics of the individual UVCB constituents. 

Key value for chemical safety assessment

Additional information

The toxicokinetics, metabolism and distribution are driven by the characteristics of the individual UVCB constituents.

The physico-chemical characterization of the UVCB (see relevant section in IUCLID) demonstrates that metal constituents are built into complex mineralogical structures consisting mainly of intermetallic and metal sulphides. This can result in potential partial solubilisation of the metals present in the UVCB (eg Cu, Ag, As).

Generally, the physical form and the physical-chemical properties of the UVCB substance are expected to limit the solubility of the UVCB constituents in biological fluids and subsequently to limit cellular absorption of the released metals. The toxicokinetics of the UVCB is therefore primarily related to the degree to which the metal mineral phases in the UVCB react with biological fluids and release soluble, potentially bio available species. In consideration of the species present in the UVCB, the metals in the UVCB can be considered sparingly to sligthly soluble and therefore the bio-accessibility of the metal ion in biological fluid is considered as equivalent to the bio-accessibility in the bio-elution tests.

In addition, the following requires to be taken into consideration:

Oral: the UVCB is a solid and needs to dissolve before it can be adsorbed. Low absorption in gastro intestinal tract can therefore be expected due to limited release of constituting species during bio availability tests. The results of gastric bio-elution tests indeed demonstrated limited bio-accessibility (details in section 3.0.4.2)

Inhalation: If remaining in molten form, the UVCB may emit/release toxic species in the form of fumes that can be inhalted. For solidified matte, only made of sufficient amount of inhalable particles (particle size less than 100 µm), are capable of entering the respiratory tract under realistic breathing conditions. The latter is only the case for fines.

 

Considering the importance of molten matte at the workplace, exposure through inhalation is also considered for the risk assessment.

Dermal: the UVCB has to dissolve into the surface moisture of the skin before dermal uptake can begin. As the UVCB is low soluble in water, it is expected to partition only sparingly to the epidermis, and thus likely resulting in only limited dermal uptake of some constituting (metal) species. The metals adsorbed after dermal exposure may also contribute to systemic metal doses and therefore have been considered for the (combined) toxicity assessement, as appropriate.

The results from bio-elution tests in “sweat”, relevant to dermal exposure demonstrates limited bio-accessability (see section 3.0.4.3)

The "bio accessible" metal ions (or species) may enter the blood stream and exert its toxic action directly to the blood or in any target tissue or organ to which the circulatory system transports or distributes it. Information on toxicokinetics (absorption, distribution, metabolism and excretion) is available for key constituents of the UVCB.