Iron(3+) ion dipotassium 2-({2-[bis(carboxylatomethyl)amino]ethyl} (carboxylatomethyl)amino)acetate; hydrate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

14-06-2010 - 15-06-2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Test performed under GLP according guidelines, all quality criteria were met

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The results as observed/predicted for EDTA-FeNa are read across to EDTA-Fe(OH)K2 as in diluted form in the aquatic environment both EDTA complexes will have a similar structure and related fate.

2. ANALOGUE APPROACH JUSTIFICATION
It is therefore considered justified to use data/predictions as observed for EDTA-FeNa also for EDTA-Fe(OH)K2.

3. ANALOGUE APPROACH JUSTIFICATION
It is considered justified to use the results as observed/predicted for EDTA-FeNa for read across to EDTA-Fe(OH)K2 because in diluted form in the aquatic environment both EDTA complexes will have a similar structure and related fate.

4. DATA MATRIX
See chapter 13 for Read across document

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not required

Vehicle:

no

Details on test solutions:

The ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate stock solution was prepared by stirring 1.00 g ethylenediaminetetraacetic
acid, ferric-sodium complex, trihydrate in 500 mL of deionized water. The ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate stock solution was a clear solution.
pH stock solution = 5.3

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Unadapted secondary activated sludge was obtained (14-06-2010) from the WWTP Nieuwgraaf in Duiven. The WWTP Duiven is an activated sludge
plant treating predominantly domestic wastewater. Prior to use the activated sludge was homogenized with a syringe. The dry weight of the
homogenized activated sludge was determined and subsequently concentrated by settlement to the required dry weight concentration. The dry
weight of the activated sludge in the incubation vessels was 1.7 g/L.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

Temperature varied from 20.1 to 21.1°C.

pH:

The pH of the reaction mixtures after the incubation period ranged from 6.9 to 7.2.

Dissolved oxygen:

aerobic during test

Details on test conditions:

-The test was performed in 250 to 300 ml Erlenmeyers.
-The homogenized activated sludge was incubated in a shaking water bath (100 rpm, 20°C) for 3 hours with various concentrations of the test
compound and synthetic sewage.
-Synthetic sewage was added to the activated sludge (1.6 ml on a total volume of 50 ml).
Synthetic sewage contained per liter: 16 g peptone
11 g meat extract
3 g urea
0.7 g NaCl
0.4 g CaCl2.2H2O
0.2 g MgSO4.7H2O
2.8 g K2HPO4
-Different concentrations (spaced by a factor two) of test compound and reference compound where added using stock solutions of respectively
2.0 g/l and 0.5 g/l.
-Tap-water was used to fill up the total test volume to 50 ml.
- The dry weight concentration of the activated sludge in the test was 1.7 g/l
-The tested concentrations of the reference compound 3,5-dichlorophenol where: 1.5, 3.0 mg/l, 5.9 mg/l,11.8 mg/l, 23.6 mg/l and 47.2 mg/l
-The tested concentrations of ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate where : 40 mg/l, 80 mg/l, 160 mg/l, 320 mg/l
and 640 mg/l
-Controls without test substance (or reference compound) are measured at the beginning and at the end of the test
-The inhibitory effect of the test substance/reference compound is expressed as a percentage of the mean of the two control respiration rates.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

640 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 640 mg/l was the highest concentration tested

Details on results:

Test conditions
The pH of the reaction mixtures after the incubation period ranged from 6.9 to 7.2. Temperature varied from 20.1 to 21.1 °C. These conditions
allowed respiration of the activated sludge used.

Validity of the test
The validity of the test is demonstrated by two criteria. First, the control respiration rates were within 15% of each other and secondly, the EC50 of the reference compound was 7 mg/L which is within the prescribed range of 5 to 30 mg/L .

Activated sludge respiration inhibition test
The inhibitory effect of ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate at a particular concentration is expressed as a percentage of the two controls. No inhibition of the respiration of the activated sludge was measured at the highest concentration tested, i.e. 640 mg/L.
Ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate is therefore considered not harmful to activated sludge.

Results with reference substance (positive control):

The EC50 of the reference compound was 7 mg/L at a contact time of 3 hours, respectively. These EC50 values is within the prescribed range of 5 to 30 mg/L.

Validity criteria fulfilled:

yes

Remarks:

The validity of the test is demonstrated by two criteria. First, the control respiration rates were within 15% of each other and secondly, the EC50 of the reference compound was 7 mg/L which is within the prescribed range of 5 to 30 mg/L .

Conclusions:

Test performed under GLP according guidelines. The test is valid as shown by the EC50of the reference compound, 3,5-dichlorophenol (7 mg/L
contact time 3 hours ) and the control respiration rates which are within 15% of each other.
No inhibition of the respiration of the activated sludge was measured at the highest concentration tested, i.e. 640 mg/L. Ethylenediaminetetraacetic
acid, ferric-sodium complex, trihydrate is therefore considered not harmful to activated sludge.

Executive summary:

In order to predict effects of chemicals in the environment and in biological waste water treatment plants, an activated sludge respiration inhibition test was performed. The toxicity to activated sludge was determined in accordance with OECD Test Guideline 209, and in compliance with the OECD principles of Good Laboratory Practice.

The test is valid as shown by the EC₅₀of the reference compound, 3,5-dichlorophenol (7 mg/L) and the control respiration rates which are within 15% of each other.

The toxicity of ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate to activated sludge was determined at a contact time of 3 hours, using various concentrations of the test substance. The inhibitory effect of ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate at a particular concentration is expressed as a percentage of the two controls. No inhibition of the respiration of the activated sludge was measured at the highest concentration tested, i.e. 640 mg/L. Ethylenediaminetetraacetic acid, ferric-sodium complex, trihydrate is therefore considered not harmful to activated sludge

Description of key information

The ecotoxicity of EDTA-FeK is considered to be similar to the ecotoxicity of EDTA-Fe(OH)K2 as both substances will be tested in very diluted form in buffered matrices and under these conditions no significant effects of the additional OH are expected. The ecotoxicity test results as observed for EDTA-FeK will therefore be read across to EDTA-Fe(OH)K2. As a worst-case no molecular weight correction is applied (14% difference).

3h-NOEC 640 mg/l (EDTA-FeNa.3H2O) respiration inhibition for activated sludge.

Recalculation to FeK-EDTA would give 383.2/421.1 x 640 = 582 mg/L, (trihydrate has to be taken into account).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

582 mg/L

Additional information

An activated sludge respiration inhibition test was performed with the test substance EDTA-FeNa.3H₂O in accordance with OECD Test Guideline 209, and in compliance with the OECD principles of Good Laboratory Practice (Geerts 2010; reliability 1, KEY study). After a contact duration of 3 hours, no inhibition of the respiration of the activated sludge was measured up to the highest concentration tested, i.e. 640 mg/L. Thus the test substance is considered not harmful to activated sludge.

In a published study the acute toxicity (15min-EC50) of Fe(III)-EDTA towards Photobacterium phosphoreum was investigated using the Microtox Toxicity Analyzer according to the protocol provided by the supplier (Sillanpaa Oikari 1996). The 15min-EC50 was found to 88.4 mg test material per liter (210 µmol/l, with a 95%CL of 154 - 286 µmol/l). The reliability was classified as Rel. 2 as details of the methods and results are lacking, including some details on the substance identity. Moreover, it is questionable whether there is no interference of the salt water with the Fe-EDTA-complex that would influence the exposure concentrations or the results.

The key study was selected as this one was carried out according to the guidelines and it tests the required object (activated sludge).