Zircon, cadmium yellow

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Annex VII, Column 2, Section 9.1.2. of Regulation (EC) 1907/2006, the test for growth inhibition of aquatic plants does not need to be conducted “if there are mitigating factors indicating that aquatic toxicity is unlikely to occur, for instance if the substance is highly insoluble in water or the substance is unlikely to cross biological membranes”.

Zirconium zircon with encapsulated cadmium sulphide can be considered environmentally and biologically inert due to the characteristics of the synthetic process (calcination at a high temperature of approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which all atoms are tightly bound and not prone to dissolution in environmental and physiological media. This assumption is supported by transformation/dissolution data (Klawonn, 2018) that indicate a very low release of pigment components at pH 6 and 8. Transformation/dissolution tests of Zirconium zircon with encapsulated cadmium sulphide at a loading of 1 mg/L and pH 6 resulted after 7 days in dissolved cadmium concentrations of 0.0798 µg Cd/L and zirconium concentrations below the LOQ of 0.0204 µg Zr/L. After 28 days at pH 6, cadmium and zirconium concentrations were below the respective LODs of 0.0048 µg Cd/L and 0.0017 µg Zr/L. Transformation/dissolution tests at pH 8 resulted after 7 days in dissolved cadmium concentrations of 0.1134 µg Cd/L and zirconium concentrations of 0.5420 µg Zr/L. After 28 days at pH 8, cadmium and zirconium concentrations amounted to 0.1966 µg Cd/L and 0.8769 µg Zr/L, respectively. Silicon and sulphur were not considered in the T/D assessment since they do not have an ecotoxic potential as confirmed by the absence of respective ecotoxicity reference values in the Metals Classification tool (MeClas) database (Version 5.10) and as specified for silicon in the OECD SIDS for silicon dioxide (OECD, 2004). Thus, the rate and extent to which Zirconium zircon with encapsulated cadmium sulphide produces soluble (bio)available ionic and other cadmium-, silicon-, sulphur- and zirconium-bearing species in environmental media is limited. Hence, the pigment can be considered as environmentally and biologically inert during short- and long-term exposure. The poor solubility of Zirconium zircon with encapsulated cadmium sulphide is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for Zirconium zircon with encapsulated cadmium sulphide. The poorly soluble substance Zirconium zircon with encapsulated cadmium sulphide is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 and 28 days at a loading rate of 1 mg/L with the lowest acute and chronic ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The acute and chronic ERVs are based on the lowest EC50/LC50 and NOEC/EC10 values for algae, invertebrates and fish, respectively, and were obtained from the Metals classification tool (MeClas) database as follows: The acute ERV for cadmium is 18 µg Cd/L, and thus well above the dissolved cadmium concentrations of 0.0798 µg Cd/L at pH 6 and 0.1134 µg Cd/L at pH 8, determined after 7 days T/D tests at a loading of 1 mg/L. Acute ERVs for silicon and sulphur have not been derived since a potential for short-term (acute) toxicity of silicon and sulphur ions was not identified. The acute ERV for zirconium (74 mg Zr/L) is above 1 mg/L and thus a concern for short-term (acute) toxicity was not identified (no classification).
Due to the lack of an acute aquatic hazard potential for soluble silicon and sulphur ions, the fact that dissolved cadmium and zirconium concentrations after 7 days T/D tests at a loading of 1 mg/L and pH 6 and 8 were significantly lower than the lowest acute ERV for cadmium and zirconium, respectively, and the fact that the summation of the toxic units of the different metals at the loading rate (1 mg/L) is lower than one (Σ TU < 1), it can be concluded that the substance Zirconium zircon with encapsulated cadmium sulphide is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC50/LC50).
Regarding the long-term toxicity, the chronic ERV for cadmium is 0.21 μg Cd/L and thus above the dissolved cadmium concentrations of < 0.0048 µg Cd/L at pH 6 and 0.1966 µg Cd/L at pH 8, determined after 28 days T/D tests at a loading of 1 mg/L. Chronic ERVs for silicon, sulphur and zirconium have not been derived since a concern for long-term (chronic) toxicity of silicon, sulphur and zirconium ions was not identified. Due to the lack of a chronic aquatic hazard potential for soluble silicon, sulphur and zirconium ions and the fact that dissolved cadmium concentrations after 28 days T/D tests at a loading of 1 mg/L and pH 6 and 8 were below the lowest chronic ERV for cadmium, it can be concluded that the substance Zirconium zircon with encapsulated cadmium sulphide is not sufficiently soluble to cause long-term toxicity at the level of the chronic ERVs (expressed as NOEC/EC10).
In accordance with Figure IV.4 “Classification strategy for determining acute aquatic hazard for metal compounds” and Figure IV.5 „Classification strategy for determining long-term aquatic hazard for metal compounds “of ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017) and section 4.1.2.10.2. of Regulation (EC) No 1272/2008, the substance Zirconium zircon with encapsulated cadmium sulphide is poorly soluble and does not meet classification criteria for acute (short-term) and chronic (long-term) aquatic hazard.
Please find attached in IUCLID section 2.1 the documentation of the aquatic hazard classification for Zirconium zircon with encapsulated cadmium sulphide derived with the Metals Classification tool (MeClas) Version 5.10 (“EBRC_Aquatic hazard classification conclusions for Zirconium zircon with encapsulated cadmium sulphide_2022-03-14”).

In accordance with Annex XI, Section 2 of Regulation (EC) 1907/2006, “Testing for a specific endpoint may be omitted, if it is technically not possible to conduct the study as a consequence of the properties of the substance”.
Zirconium zircon with encapsulated cadmium sulphide is poorly soluble and unlikely to cross biological membranes. Hence, Zirconium zircon with encapsulated cadmium sulphide can be considered environmentally and biologically inert during aquatic exposure (please see above). For a highly insoluble substance such as Zirconium zircon with encapsulated cadmium sulphide, it may neither be possible nor relevant to try and conduct aquatic toxicity tests, as it is difficult to maintain a quantifiable and constant concentration of the substance in the environmental test medium. In accordance with the generic testing recommendations in the “Executive summary of the MISA 2 workshop (https://echa.europa.eu/misa)” for difficult to test substances, “The Water Accommodated Fraction (WAF) method (see REACH and OECD guidance on difficult to test substances), should not be used for metals. The reason is that this method often uses nominal loadings and lacks the pH and surface relationships necessary to estimate the potential hazard. Direct aquatic ecotoxicity testing of metals and SSMCs is in principle not recommended. However, if used or needed (e.g. for complex materials like UVCBs) then it should be conducted based on the dissolved fraction(s) of the T/D medium, at the appropriate pH (pH that dilutes the most).”
Since the substance Zirconium zircon with encapsulated cadmium sulphide is not sufficiently soluble to cause toxicity at the level of the acute and chronic ERVs (expressed as EC/LC50 or EC10/NOEC), it is not technically possible in accordance with Annex XI, Section 2 of Regulation (EC) 1907/2006 to conduct any further aquatic toxicity study, including testing for growth inhibition of aquatic plants with Zirconium zircon with encapsulated cadmium sulphide.

Zirconium zircon with encapsulated cadmium sulphide is poorly soluble and unlikely to cross biological membranes. In accordance with Annex VII, Column 2, Section 9.1.2. of Regulation (EC) 1907/2006, testing for growth inhibition of aquatic plants is not necessary.


References:

EC (2007) European Union risk assessment report cadmium oxide and cadmium metal part I - Environment.

Klawonn T, 2018, Determination of the transformation/dissolution of inorganic pigment IPC-2018-005 (Zircon, cadmium yellow) in aqueous media, Fraunhofer Institute for Molecular Biology and Applied Ecology (IME).

OECD (2004) SIDS Initial Assessment Profile Silicon dioxide, Silicic acid, aluminum sodium salt, Silicic acid, calcium salt. SIAM 19, 19-22 October 2004.