Iron manganese trioxide

Endpoint summary

Description of key information

Based on read-across to nanosized iron (hydr)oxides (see attachment "Read-across justification-environ assessment-iron oxides" and “Endpoint-specific read-across justification for nano forms of iron oxide, 2021” attached IUCLID section 13), available data for fish, invertebrates, algae and microorganisms indicate a low potential for acute and chronic aquatic toxicity of nanosized iron manganese trioxide.

Additional information

Data available on the short-term toxicity of different nanosized iron (hydr)oxides, including nanosized iron hydroxide oxide yellow and diiron trioxide 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 > 100 g/L, a concentration as high as the corresponding OECD test limit for acute toxicity and > 20 mg/L for algae.

Nanosized iron (hydr)oxides are also not toxic to aquatic micro-organisms as 3-h EC50 value for the respiration inhibition of nanosized iron hydroxide oxide/diiron trioxide (75:25) is > 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

In all acute and chronic toxicity studies with nanosized iron (hydr)oxides, effect concentrations were unbounded and/or above the OECD test limit (see Table below).

 

Table: Aquatic toxicity ofnanosized iron(hydr)oxides.

Endpoint	Test species	Test results	Test material/form	Reliability: Reference
Short-term toxicity to fish	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	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	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.

Iron manganese trioxide can be considered environmentally and biologically inert due to the 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 iron manganese trioxide is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 days 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 iron manganese trioxide with a maximum manganese content of 10% 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 100 µg Mn/L that could dissolve during T/D of iron manganese trioxide (with a maximum manganese content of 10%) 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 iron manganese trioxide cannot cause a concern for chronic aquatic toxicity, it can be concluded that the substance iron manganese trioxide does also not have a chronic aquatic hazard potential.

The conclusion on a lack of an aquatic hazard potential of nanosized iron manganese trioxide 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, nanosized iron manganese trioxide (poorly soluble iron oxide category substances incl. nanosized iron manganese trioxide) does 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 nanosized iron (hydr)oxides, there are not any reliable ecotoxicity data showing effects in aquatic organisms, soluble iron salts and nanosized iron manganese trioxide are not classified as dangerous for the aquatic environment, an aquatic PNEC cannot be derived thus not indicating a hazard to the aquatic environment.

Nanosized iron manganese trioxide is not classified as harmful, toxic or very toxic to aquatic life or may cause long lasting harmful effects to aquatic life. Nanosized iron manganese trioxide is 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"), nanosized iron manganese trioxide is also not considered an unclassified hazard to the aquatic compartment.