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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:
short-term toxicity to aquatic invertebrates
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is highly insoluble in water, hence indicating that aquatic toxicity is unlikely to occur
the study does not need to be conducted because the substance is unlikely to cross biological membranes, hence indicating that aquatic toxicity is unlikely to occur
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
According to Annex VII, Column 2, Section 9.1.1. of Regulation (EC) 1907/2006, testing for short-term toxicity on invertebrates 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 praseodymium yellow zircon 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 available transformation/dissolution data (Grane, 2010) that indicate a very low release of pigment components. Transformation/dissolution of zirconium praseodymium yellow zircon (24-screening test according to OECD Series 29, loading of 100 mg/L) resulted in mean dissolved praseodymium concentrations of 3.05 µg/L Pr and 21.66 µg/L Pr, silicon concentrations of 0.13 µg/L Si and 0.02 µg/L Si at pH 6 and 8, respectively, whereas dissolved zirconium concentrations remained below the LOD (< 0.08 µg/L Zr). Since silicon does not have an ecotoxic potential, as confirmed by the absence of respective ecotoxicity reference values in the Metals classification tool (MeClas) database, and the dissolution of praseodymium is highest at pH 6, pH 6 is considered as pH that maximised metal release. Metal release at the 1 mg/L loading and pH 6 resulted in dissolved concentrations of 2.10 µg/L Pr and 0.17 µg/L Zr after 7 days and 0.79 µg/L Pr and < 0.08 µg/L Zr (< LOD) after 28 days whereas silicon concentrations remained below the LOD (< 0.07 µg/L Si) during the test. Thus, the rate and extent to which zirconium praseodymium yellow zircon produces soluble (bio)available ionic and other praseodymium-, silicon- or 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 praseodymium yellow zircon is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Reliable proprietary studies are not available for zirconium praseodymium yellow zircon. The poorly soluble substance zirconium praseodymium yellow zircon is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 days at a loading rate of 1 mg/L with the lowest acute ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The ERVs are based on the lowest EC50/LC50 values for algae, invertebrates and fish. Acute ERVs were obtained from the Metals classification tool (MeClas) database as follows: Hazard information for praseodymium is not included in the MeClas database. Nevertheless, soluble praseodymium salts (Praseodymium trichloride, EC 233-794-4, CAS 10361-79-2; Praseodymium trinitrate, EC 233-796-5, CAS 10361-80-5) are self-classified as Aquatic Acute 1 (M-factor 1) indicative of an L(E)C50 of > 0.1 ≤ 1 mg/L (https://echa.europa.eu/information-on-chemicals/cl-inventory-database, accessed on 12.03.2021), which is applied to evaluate the aquatic hazard potential of zirconium praseodymium yellow zircon. An acute ERV for silicon has not been derived since a concern for short-term (acute) toxicity of silicon ions was not identified (see also OECD, 2004). The acute ERV for zirconium in the MeClas database amounts to 74 mg Zr/L. According to ECHA’s Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), “Where the acute ERV for the metal ions of concern is greater than 1 mg/L the metals need not be considered further in the classification scheme for acute hazard.” Metal release in the T/D test at the 1 mg/L loading and pH 6 resulted in dissolved concentrations of 2.10 µg/L Pr and 0.17 µg/L Zr after 7 days, whereas silicon concentrations remained below the LOD (< 0.07 µg/L Si). Due to the lack of an aquatic hazard potential for silicon and zirconium ions and the fact that dissolved praseodymium concentrations were well below the respective L(E)C50 estimate of > 0.1 ≤ 1 mg/L, it can be concluded that the substance zirconium praseodymium yellow zircon is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC50/LC50).

In accordance with Figure IV.4 “Classification strategy for determining acute 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 praseodymium yellow zircon is poorly soluble and does not meet classification criteria for acute (short-term) aquatic hazard.

Zirconium praseodymium yellow zircon is poorly soluble and unlikely to cross biological membranes. In accordance with Annex VII, Column 2, Section 9.1.1. of Regulation (EC) 1907/2006, testing for short-term toxicity to invertebrates is not necessary.

References:

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

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion

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