Spinels, cobalt tin grey

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”.

Cobalt magnesium tin spinel 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 cobalt tin magnesium spinel at a loading of 1 mg/L and pH 6 resulted after 7 days in dissolved cobalt concentrations of 0.412 µg Co/L, and tin concentrations of 0.641 µg Sn/L. After 28 days at pH 6 dissolved cobalt and tin concentrations amounted to 0.498 µg Co/L and 0.344 µg Sn/L, respectively. T/D tests at pH 8 resulted after 7 days in cobalt and tin concentrations of 0.677 µg Co/L and 2.253 µg Sn/L, respectively. After 28 days at pH 8, the dissolved cobalt concentrations amounted to 0.764 µg Co/L and tin concentrations to 2.921 µg Sn/L. 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”. Further, “Where the chronic ERV for the metal ions of concern is greater than 1 mg/L, the metals need not be considered further in the classification scheme”. Accordingly, magnesium was not considered in the T/D assessment since it does not have an ecotoxic potential as confirmed by ecotoxicity reference values of > 1 mg Mg/L listed in the Metals classification tool (MeClas) database. Thus, the rate and extent to which cobalt tin magnesium spinel produces soluble (bio)available ionic and other cobalt-, and tin-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 cobalt tin magnesium spinel is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.


Proprietary studies are not available for Cobalt magnesium tin spinel. The poorly soluble substance Cobalt magnesium tin spinel 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 acute ERVs are based on the lowest EC50/LC50 values for algae, invertebrates and fish and were obtained from the Metals classification tool (MeClas) database as follows: An acute ERV for magnesium has not been derived since a concern for short-term (acute) toxicity of magnesium ions was not identified. The acute ERV for tin ions is above 1 mg/L (9.8 mg Sn/L) and thus a concern for short-term (acute) toxicity was not identified (no classification). 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.” The acute ERV for cobalt is 52.0 µg Co/L and thus well above the dissolved cobalt concentrations of 0.412 µg Co/L at pH 6 and 0.677 µg Co/L at pH 8 determined after 7 days T/D test at a loading of 1 mg/L. Due to the lack of an acute aquatic hazard potential for soluble magnesium and tin ions and the fact that the dissolved cobalt concentrations after 7 days T/D tests at pH 6 and 8 were significantly lower than the lowest acute ERV for cobalt, it can be concluded that the substance cobalt tin magnesium spinel 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 Cobalt magnesium tin spinel is poorly soluble and does not meet classification criteria for acute (short-term) aquatic hazard. Please find attached in IUCLID section 2.1 the documentation of the aquatic hazard classification for Cobalt magnesium tin spinel derived with the Metals Classification tool (MeClas) Version 5.11 (“EBRC_Aquatic hazard classification conclusions for Cobalt magnesium tin spinel _2022-11-17”).


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”.
Cobalt magnesium tin spinel is poorly soluble and unlikely to cross biological membranes. Hence, Cobalt magnesium tin spinel can be considered environmentally and biologically inert during aquatic exposure (please see above). For a highly insoluble substance such as Cobalt magnesium tin spinel, 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 Cobalt magnesium tin spinel is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC/LC50), 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 short-term toxicity to invertebrates with Cobalt magnesium tin spinel.

Cobalt magnesium tin spinel 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.