Zirconium zircon with encapsulated cadmium selenium sulphide

Endpoint summary

Description of key information

Zirconium zircon with encapsulated cadmium selenium sulphide is moderately soluble in environmental media. Based on results of a standard transformation/dissolution test according to OECD Series 29, the dissolution at a loading of 1 mg/L Zirconium zircon with encapsulated cadmium selenium sulphide at pH 6, the pH that maximizes dissolution, results in dissolved cadmium levels of 0.41 µg Cd/L and 0.86 µg Cd/L and in dissolved selenium levels 0.05 µg Se/L and < LOQ (0.14 µg/L) after 7 and 28 days, respectively. Dissolved zirconium concentrations at a loading of 1 mg/L resulted in concentrations below the LOD (0.003 µg/L, pH 6 and 8) after 7 days, and below the LOQ (0.002 µg/L, pH 8) after 28 days. Thus, the rate and magnitude to which Zirconium zircon with encapsulated cadmium selenium sulphide releases soluble, (bio)available ionic and other cadmium-, selenium- and zirconium-bearing species in environmental media is limited.  Zirconium zircon with encapsulated cadmium selenium sulphide also contains silicon and sulfur, however, both elements do not have an ecotoxicological potential (see OECD SIDS silicon dioxide, 2004), as also confirmed by the absence of respective ecotoxicity reference values in the Metals Classification tool (MeClas) database (http://www.meclas.eu accessed on 10.05.2021).

Further, the limited solubility of Zirconium zircon with encapsulated cadmium selenium sulphide is expected to determine its behaviour and fate in the environment, and subsequently its bioavailability and potential for bioaccumulation and ecotoxicity.

Since Zirconium zircon with encapsulated cadmium selenium sulphide is not sufficiently soluble to cause short-term or long-term toxicity at the level of the acute and chronic ERVs for selenium and zirconium ions, the aquatic hazard potential of Zirconium zircon with encapsulated cadmium selenium sulphide is assessed based on the release of cadmium ions. A conservative read-across approach is applied based on all available information for various inorganic cadmium substances, and the fate of released cadmium ions can eventually be considered comparable to the general fate of cadmium ions in the environment. For further information on the applied read-across approach, please refer to the RAAF document “Read-across approach for the assessment of the environmental fate and toxicity of the pigment Zirconium zircon with encapsulated cadmium selenium sulphide” attached in IUCLID Section 13.