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Toxicity to microorganisms

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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: Guideline study with acceptable restrictions
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.
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
>= 10 000 mg/L

No relevant effect on activated sludge

Validity criteria fulfilled:
yes
Remarks:
The validity of the test was checked on the basis of a graphic analysis of the reference item.
Conclusions:
Following the OECD Guideline 209 for triiron tetraoxide a 3-hour EC50 of >/= 10000 mg/L was obtained on activated sludge of a predominantly domestic sewage.
Executive summary:

Following the OECD Guideline 209 for triiron tetraoxide a 3-hour EC50 of >/= 10000 mg/L was obtained on activated sludge of a predominantly domestic sewage.

A defined quantity of activated sludge is fed with a synthetic nutrition medium and the respiration rate is measured. This respiration rate is compared with those, measured in various test preparations containing different concentrations of the test item. The sensitivity of the used activated sludge is checked with 3,5-Dichlorophenol as reference item.

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: Guideline study with acceptable restrictions
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.
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Principles of method if other than guideline:
read across
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
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
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
>= 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
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 3-hour EC50 was >/= 10000 mg/L on activated sludge with the test item manganese ferrite, related to respiration rate. The method used was the OECD Guideline 209.
Executive summary:

A defined quantity of activated sludge is fed with a synthetic nutrition medium and the respiration rate is measured. This respiration rate is compared with those, measured in various test preparations containing different concentrations of the test item. The sensitivity of the used activated sludge is checked with 3,5-Dichlorophenol as reference item.

The 3-hour EC50 of manganese ferrite was >/= 10000 mg/L on activated sludge, related to respiration rate. The method used was the OECD Guideline 209.

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: Guideline study with acceptable restrictions
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.
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

no effect on test microorganisms

Validity criteria fulfilled:
yes
Remarks:
The validity of the test was checked on the basis of a graphic analysis of the reference item.
Conclusions:
Following the guideline ISO 8192 a 3-hour EC50 of > 10000 mg/L for Iron(III)oxide was obtained on activated sludge of a predominantly domestic sewage.
Executive summary:

Following the guideline ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) a 3-hour EC50 of > 10000 mg/L for Iron(III)oxide 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).

Description of key information

Applying read-across to micro- and nano-sized iron (hydr)oxides (see attachment "Read-across justification-environ assessment-iron oxides" in section 13), micro-sized iron (hydr)oxides are not considered toxic to aquatic microorganisms. Based on studies with activated sewage sludge exposed to micro- and nano-sized 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.

Key value for chemical safety assessment

EC50 for microorganisms:
10 000 mg/L

Additional information

For micro- and nano-sized iron (hydr)oxides, three reliable studies on toxicity to aquatic microorganisms are available. Toxicity was not observed in activated sludge exposed to micro- and nano-sized iron (hydr)oxide forms, and unbounded 3-h EC50 values of > 10 g/L were derived.


 


In a guideline study with activated sludge exposed to micro-sized triiron tetraoxide according to OECD 209 (Bruns, 1989), adverse effects on respiration rate were not observed after 3 h and an unbounded 3 h EC50 value of > 10 g/L was derived. Further, an unbounded 3-h EC50 value of > 10 g/L was derived for micro-sized manganese ferrite black spinel in a guideline study with activated sludge according to OECD 209.


 


Toxicity of nano-sized 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.


 


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 indicate a low potential for toxicity of iron (hydr)oxides to activated sludge microorganisms (see table below). Toxicity of micro- and nano-sized iron (hydr)oxides to aquatic microorganisms was not observed up to 10 g/L (Bruns, 1989; Bruns, 2004), a concentration that is 10-fold above the corresponding OECD test limit for toxicity to microorganisms.


 


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



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