High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix

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”.

High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix 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 (Grané, 2010) that indicate a very low release of pigment components. Transformation/dissolution of High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix (24-screening test according to OECD Series 29, loading of 100 mg/L, pH 6 and 8) resulted in mean dissolved iron concentrations of 0.131 µg/L Fe and 0.002 µg/L Fe, silicon concentrations of 215.7 µg/L Si and 204 µg/L Si at pH 6 and 8, respectively. Dissolution of iron and silicon is highest at pH 6, therefore pH 6 is considered as pH that maximised metal release. Metal release at the 1 mg/L loading and pH 6 remained below the respective LOD for iron and silicon (<0.22 µg/L Fe and <0.07 µg/L Si). After 28 days at the 1 mg/L loading and pH 6 iron concentrations of 0.29 µg/L were measured whereas silicon concentrations remained below the LOD (< 0.07 µg/L Si). Thus, the rate and extent to which High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix produces soluble (bio)available ionic and other silicon- and iron-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 High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix. The poorly soluble substance High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix 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: For iron ions, the acute ERV is above 1 mg/L (in fact above 100 mg/L), and a concern for short-term (acute) toxicity was not identified (no classification). 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). According to ECHA 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.” Due to the lack of an aquatic hazard potential for soluble silicon and iron ions and the fact that dissolved silicon and iron concentrations were below the LOD of 0.07 µg/L and 0.22 µg/L, respectively, after 7 days at pH 6 in the T/D test, it can be concluded that the substance High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix 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 High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is poorly soluble and does not meet classification criteria for acute (short-term) aquatic hazard.

High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix 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.