Chromium iron oxide

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”.

Chromium iron oxide 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, 2010) that indicate a very low release of pigment components. Transformation/dissolution of chromium iron oxide (24-screening test according to Oecd Series 29, loading of 100 mg/L, pH 6 and 8) resulted in metal concentrations that are below the respective LODs for chromium and iron (< 0.5 µg/L). Dissolved chromium and iron concentrations remained also below the respective LOD after 7 days with 1 mg/L (and also 100 mg/L) and after 28 days with 1 mg/L at pH 6. Thus, the rate and extent to which chromium iron oxide produces soluble (bio)available ionic and other chromium- 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 chromium iron oxide is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for chromium iron oxide. The poorly soluble substance chromium iron oxide 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 trivalent chromium and iron ions, the acute ERVs are above 1 mg/L (in fact above 100 mg/L), respectively, and 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.” Due to the lack of an aquatic hazard potential for soluble trivalent chromium and iron ions and the fact that dissolved chromium and iron concentrations were below the LOD of 0.5 µg/L after 7 days at pH 6 in the T/D test, it can be concluded that the substance chromium iron oxide 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 chromium iron oxide is poorly soluble and does not meet classification criteria for acute (short-term) aquatic hazard.

Chromium iron oxide 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.