Iron hydroxide oxide yellow

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

Study period:

1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Justification for type of information:

see "Endpoint-specific read-across justification for nanoforms of iron oxide_2021” attached in IUCLID section 13
see "Read-across justification-environ assessment-iron oxides_2021” attached in IUCLID section 13

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

GLP compliance:

no

Analytical monitoring:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Remarks on exposure duration:

Permanent aeration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

>= 10 000 mg/L

Validity criteria fulfilled:

yes

Remarks:

The validity of the test was checked on the basis of a graphic analysis of the reference item.

Conclusions:

The obtained 3-hour EC50 for diiron trioxide was >/= 10000 mg/L. The method ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) was used applying activated sludge of a predominantly domestic sewage. Due to the similarity in structure the same value was assumed for iron hydroxide oxide.

Executive summary:

The obtained 3-hour EC50 for diiron trioxide was >/= 10000 mg/L. The method ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) was used applying activated sludge of a predominantly domestic sewage. Due to the similarity in structure the same value was assumed for iron hydroxide oxide.

Description of key information

A 3-hour EC50 of > 10,000 mg/L for the respiration inhibition of activated sewage sludge was determined for iron hydroxide oxide/diiron trioxide (75:25) alpha nanoparticles (Bruns, 2004).

Additional information

Following the guideline ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) a 3-hour EC50 of > 10000 mg/L for iron hydroxide oxide/diiron trioxide (75:25) alpha nanoparticles was obtained on activated sludge of a predominantly domestic sewage. Nominal concentrations of 100 mg/L, 1000 mg/L and 10000 mg/L were used. No chemical analysis was performed. The validity of the test was checked on the basis of a graphic analysis of the reference item (3,5 -Dichlorophenol).

Based on read-across to triiron tetraoxide (see attachment "Iron oxides category justification” in IUCLID section 13), available data for microorganisms further indicate a low potential of toxicity of

iron hydr(oxides) to activated sludge microorganisms (see table below).

Table: Toxicity of 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
	Activated sludge	EC50 (3 h): > 10 g/L nominal	triiron tetraoxide	RL2: Bruns, 1989

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.