Zirconium iron pink zircon

Long-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

long-term toxicity to aquatic invertebrates

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
Zirconium zircon with encapsulated hematite 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 (Pardo Martinez, 2013) that indicate a very low release of pigment components. Transformation/dissolution tests at a loading of 100 mg/L for 7 days resulted in dissolved iron and zirconium concentrations below the LOD of < 0.5 µg/L at pH 6 and 2.4 µg Fe/L and 2.17 µg Zr/L at pH 8. Thus, metal release is maximised at pH 8. Transformation/dissolution at a loading of 1 mg/L and pH 8 resulted in dissolved iron and zirconium concentrations below the LOD (< 0.5 µg/L) after 7 and 28 days. Silicon was not considered in the T/D assessment since it does not have an ecotoxic potential as confirmed by the absence of respective ecotoxicity reference values in the Metals classification tool (MeClas) database (see also OECD 2004). Thus, the rate and extent to which Zirconium zircon with encapsulated hematite produces soluble (bio)available ionic and other iron- 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 hematite 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 hematite. The poorly soluble substance Zirconium zircon with encapsulated hematite is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 28 days at a loading rate of 1 mg/L with the lowest chronic ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The chronic ERVs are based on the lowest NOEC/EC10 values for algae, invertebrates and fish and were obtained from the Metals classification tool (MeClas) database as follows: A chronic ERV for silicon has not been derived since a concern for long-term (chronic) toxicity of silicon ions was not identified (see also OECD, 2004). A chronic ERV has also not been derived for zirconium. For iron ions, the chronic ERV is above 1 mg/L and a concern for long-term (chronic) toxicity was not identified (no classification). According to ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), ”Where the chronic ERV for the metal ions of concern corrected for the molecular weight of the compound (further called as chronic ERV compound) is greater than 1 mg/L, the metal compounds need not to be considered further in the classification scheme for long-term hazard.” Due to the lack of a chronic aquatic hazard potential for iron, silicon and zirconium ions and the fact that dissolved iron and zirconium concentrations were below the LOD of 0.5 µg/L after 28 days at pH 8 in the T/D test, it can be concluded that the substance Zirconium zircon with encapsulated hematite 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.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 hematite is poorly soluble and does not meet classification criteria for chronic (long-term) aquatic hazard.

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 hematite is poorly soluble and unlikely to cross biological membranes. Hence, Zirconium zircon with encapsulated hematite can be considered environmentally and biologically inert during aquatic exposure (please see above). For a highly insoluble substance such as Zirconium zircon with encapsulated hematite, 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 hematite is not sufficiently soluble to cause long-term toxicity at the level of the chronic ERVs (expressed as NOEC/EC10), it is neither technically possible in accordance with Annex XI, Section 2 of Regulation (EC) 1907/2006 nor scientifically justified to conduct any further aquatic toxicity study, including long-term toxicity to invertebrates with Zirconium zircon with encapsulated hematite.

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