Iron manganese trioxide

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: as reported in source record

Justification for type of information:

see attachment "Read-across justification-environ assessment-iron oxides" and “Endpoint-specific read-across justification for nano forms of iron oxide, 2021” attached in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 10 000 mg/L

Description of key information

Applying read-across to nanosizediron(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 in IUCLID section 13), nanosized iron manganese trioxide is not considered toxic to aquatic microorganisms. An unbounded 3-h EC50 value of >10,000 mg/L for respiration inhibition of activated sewage sludge was derived for nano-alpha iron hydroxide oxide/diiron trioxide (75:25) particles (Bruns, 2004), a concentration that is 10-fold above the corresponding OECD test limit.

Additional information

Toxicity of nanosized iron (hydr)oxides to aquatic microorganisms was investigated in a study using activated sludge of a predominantly domestic sewage exposed to iron hydroxide oxide/diiron trioxide (75:25) alpha nanoparticles, following ISO guideline 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge). An unbounded 3-h EC50 value of >10 g/L was derived, as adverse effects were not observed at the highest concentration tested,a concentration that is 10-fold above the corresponding OECD test limit.

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 in IUCLID section 13), available data indicate a low potential for toxicity ofnanosized iron manganese trioxideto aquatic microorganisms (see table below).

 

Table: Toxicity of nanosized iron (hydr)oxides to aquatic microorganisms.

Endpoint	Test species	Test results	Test material/form	Reliability: Reference
Toxicity to microorganisms	Activated sludge	EC50 (3 h): > 10 g/L nominal	iron hydroxide oxide/diiron trioxide (75:25) / nano, alpha	RL2: Bruns, 2004

Supportive information microsized iron (hydr)oxides

Based on two studies with activated sewage sludge exposed to microsized iron (hydr)oxides, unbounded 3-h EC50 values of >10,000 mg/L were derived, a concentration that is 10-fold above the corresponding OECD test limit.