Registration Dossier

Ecotoxicological information

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
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 iron and chromium (< 0.5 µg/L). Dissolved metal 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 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 ERVs are based on the lowest NOEC/EC10 values for algae, invertebrates and fish. Chronic ERVs were obtained from the Metals classification tool (MeClas) database as follows: For trivalent chromium and iron ions, the chronic ERVs are above 1 mg/L, respectively, 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 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 28 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 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 chromium iron oxide 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”.

Chromium iron oxide is poorly soluble and unlikely to cross biological membranes. Hence, chromium iron oxide can be considered environmentally and biologically inert during aquatic exposure (please see above). For a highly insoluble substance such as chromium iron oxide, 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 chromium iron oxide 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 chromium iron oxide.

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion