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Based on read-across to micro- and nano-sized iron (hydr)oxides (see attachment "Read-across justification-environ assessment-iron oxides" in section 13), available data for fish, invertebrates, algae and microorganisms indicate a low potential for acute and chronic aquatic toxicity of micro-sized iron (hydr)oxides.

Additional information

Data available on the short-term toxicity of different iron (hydr)oxides, including micro- and nano-sized iron hydroxide oxide yellow, diiron trioxide, triiron tetraoxide, zinc ferrite brown spinel and manganese ferrite black spinel, to fish (Danio rerio), invertebrates (Daphnia magna) and algae (Pseudokirchneriella subcapitata) indicate a low potential for acute toxicity. Respective unbounded EC/LC50 values amount for fish up to > 100 g/L, a concentration that is 1000-fold above the corresponding OECD test limit for acute toxicity, for invertebrates up to > 10 g/L, a concentration that is 100-fold above the corresponding OECD test limit for acute toxicity and > 20 mg/L for algae.


 


Iron (hydr)oxides are also not toxic to aquatic micro-organisms as 3-h EC50 values for the respiration inhibition of different iron (hydr)oxides, including micro- and nano-sized iron hydroxide oxide/diiron trioxide (75:25), manganese ferrite black spinel and triiron tetraoxide are > 10 g/L, a concentration that is 10-fold above the corresponding OECD test limit.


 


Furthermore, chronic toxicity data of diiron trioxide in nanoform indicate a low potential for aquatic toxicity since NOECs available for three trophic levels (algae, invertebrates, fish) are ≥ 10 mg/L, and thus above the corresponding OECD test limit of 10 mg/L for chronic toxicity.


 


Regarding differences in the particle size, the available data for the acute toxicity of diiron trioxide in powder and nano-form to fish further indicate that the particle size does not affect the toxicity potential to any detectable extent since effect concentrations of the powder and nano-form are up to 500-fold above the OECD test limit.In all acute and chronic toxicity studies with iron (hydr)oxides, effect concentrations were unbounded and/or above the OECD test limit (see Table below).


 


Table: Aquatic toxicity ofiron(hydr)oxides.











































































































































Endpoint



Test species



Test results



Test material/form



Reliability: Reference



Short-term toxicity to fish



Danio rerio



LC50 (96h): > 50 g/L nominal


LC0 (96h): >= 50 g/L nominal



diiron trioxide / powder



RL2: Bruns, 1989



.



Danio rerio



LC50 (96h): > 10 g/L nominal


LC0 (96h): >= 10 g/L nominal



triiron tetraoxide / powder



RL2: Caspers, 2000



.



Danio rerio



LC50 (96h): > 10 g/L nominal


LC0 (96h): >= 10 g/L nominal



triiron tetraoxide /powder



RL2: Bayer AG, 1989



.



Danio rerio



LC50 (96h): > 100 g/L nominal


LC0 (96h): >= 100 g/L nominal



zinc ferrite brown spinel / powder



RL2: Weyers, 1989



.



Danio rerio



LC50 (96h): > 100 g/L nominal


LC0 (96h): >= 100 g/L nominal



manganese ferrite black spinel / powder



RL2: Weyers, 1989



.



Danio rerio



LC50 (96h): > 10 g/L nominal


LC0 (96h): >= 10 g/L nominal



diiron trioxide / nano, alpha



RL2: Weyers, 1985



.



Danio rerio



LC50 (96h): > 100 g/L nominal


LC0 (96h): >= 100 g/L nominal



iron hydroxide oxide yellow / nano, alpha



RL2: Weyers & Caspers, 1989



Long-term toxicity to fish



Danio rerio



NOEC (168 h): 10 mg/L nominal



diiron trioxide / nano, alpha



RL3: Zhu et al., 2012



Short-term toxicity to aquatic invertebrates



Daphnia magna



EC50 (48h): > 100 mg/L nominal



diiron trioxide / powder



RL2: Neuhahn, 2008



.



Daphnia magna



EC0 (48 h): >= 10 g/L nominal



triiron tetraoxide /powder



RL2: Caspers, 2000



.



Daphnia magna



EC0 (48 h): >= 10 g/L nominal



zinc ferrite brown spinel / powder



RL2: Caspers, 1999



.



Daphnia magna



EC0 (48 h): >= 10 g/L nominal



manganese ferrite black spinel / powder



RL2: Caspers, 2000



.



Daphnia magna



EC50 (48h): > 100 mg/L nominal



iron hydroxide oxide yellow / nano, alpha



RL2: Neuhahn, 2008



Long-term toxicity to aquatic invertebrates



Daphnia magna



NOEC (21d): >= 20 mg/L nominal



diiron trioxide / nano



RL2: Nogueira et al., 2015



Toxicity to aquatic algae and cyanobacteria



Pseudokirchneriella subcapitata



NOEC (72 h): >= 20 mg/L nominal


EC50 (72 h): > 20 mg/L nominal



diiron trioxide / nano



RL2: Nogueira et al., 2015



Toxicity to microorganisms



Activated sludge



EC50 (3 h): > 10 g/L nominal



triiron tetraoxide / powder



RL2: Bruns, 1989



.



Activated sludge



EC50 (3 h): >= 10 g/L nominal



manganese ferrite black spinel / powder



RL2: Bruns, 1989



.



Activated sludge



EC50 (3 h): > 10 g/L nominal



iron hydroxide oxide/diiron trioxide (75:25) / nano, alpha



RL2: Bruns, 2004



 


Soluble iron salts are also not considered toxic to the aquatic life, i.e. do not meet CLP classification criteria for acute (short-term) aquatic hazard and chronic (long-term) aquatic hazard.


 


Manganese ferrite can be considered environmentally and biologically inert due to the spinel structure in which atoms are tightly bound and not prone to dissolution in environmental and physiological media. This assumption is supported by available water solubility data that indicate a very low release.


 


The acute and chronic aquatic hazard potential of poorly soluble substances such as manganese ferrite is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 and 28 days at a loading rate of 1 mg/L with the lowest acute and chronic ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions, respectively. Acute and chronic ERVs are based on the lowest EC50/LC50 or NOEC/EC10 values for algae, invertebrates and fish, respectively and were obtained from the Metals classification tool (MeClas) database (Version 5.9 accessed on 22.11.2021) as follows:


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”. Iron (hydr)oxides are not expected to have an acute and chronic ecotoxic potential as confirmed by the absence of ecotoxicity reference values for iron (ions) in the Metals classification tool (MeClas) database. Thus, a concern for short-term (acute) and long-term (chronic) toxicity of iron (ions) was not identified (no classification).


The acute ERV of manganese ions is with 3.2 mg Mn/L also above 1 mg/L and thus, a concern for short-term (acute) toxicity of manganese ions was also not identified (no classification). Due to the lack of an acute aquatic hazard potential for soluble iron and manganese ions, it can be concluded that the substance manganese ferrite with a maximum manganese content of 20% does also not have an acute aquatic hazard potential.


The chronic ERV for manganese is with 0.55 mg Mn/L well above the maximum (theoretically possible) manganese concentration of 200 µg Mn/L that could dissolve during T/D of manganese ferrite (with a maximum manganese content of 20%) after 28 days at a loading of 1 mg/L. Due to the lack of a chronic aquatic hazard potential for soluble iron ions and the fact that the maximum manganese content of manganese ferrite cannot cause a concern for chronic aquatic toxicity, it can be concluded that the substance manganese ferrite does also not have a chronic aquatic hazard potential.


 


The conclusion on a lack of an aquatic hazard potential of iron (hydr)oxides is in accordance with a Tier-1 assessment performed with MECLAS version 5.2 (http://www.meclas.eu/ accessed on 22.11.2021). The Metals Classification Tool (MECLAS) is a web enabled classification tool always updated to the latest classification guidance, legal ruling, information on toxicity references and available self-classifications.


 


In sum, iron (hydr)oxides (poorly soluble iron oxide category substances, incl. manganese ferrite) do not meet classification criteria of an acute or long-term aquatic hazard of Regulation (EC) No 1272/2008.


 


“If there are ecotoxicity data showing effects in aquatic organisms, but the substance is not classified as dangerous for the aquatic environment, an aquatic PNEC can nevertheless be derived thus indicating a hazard to the aquatic environment (ECHA guidance on IR & CSA, Part B: Hazard Assessment (V. 2.1, December 2011).” For soluble iron salts and poorly soluble iron (hydr)oxides, there are not any reliable ecotoxicity data showing effects in aquatic organisms, soluble iron salts and iron (hydr)oxides are not classified as dangerous for the aquatic environment, an aquatic PNEC cannot be derived thus not indicating a hazard to the aquatic environment.


 


Micro-sized iron (hydr)oxides are not classified as harmful, toxic or very toxic to aquatic life or may cause long lasting harmful effects to aquatic life. Micro-sized iron (hydr)oxides are also not an unclassified hazard to the aquatic environment. Based on the poor solubility, bioavailability, lack of a potential for bioaccumulation and toxicity to aquatic organisms and considering ubiquitousness of iron (hydr)oxides in the aquatic compartment and essentiality of iron (as described in section "Nano-Environmental fate and pathways"), micro-sized iron (hydr)oxides are also not considered an unclassified hazard to the aquatic compartment.