Zinc EDDHA

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Please refer to Read Across Statement attached in Section 13

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

450 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

No further details are available.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: up to 80 % inhibition occurred

Reported statistics and error estimates:

In order to calculate the inhibition effects of the test item at a particular concentration, the respiration rate was expressed as percentage of the mean of the 2 control respiration rates.
The degree of inhibition (EC10 and EC20) of the test item was evaluated by Probit analysis according to Finney. The values were given with an accuracy of 2 significant digits.
The degree of inhibition (EC20; EC50 and EC80) of the reference item was also evaluated by Probit analysis according to Finney.

Measured data of oxygen content of the test assays at the begin and end of the evaluation time:

Assay identification	BC1	BC2	RS1	RS2	RS3	TS1	TS2	TS3	TS4	TS5
O2-concencentration Start [mg/L]	8.0	8.0	8.4	8.7	9.1	8.2	8.3	8.5	7.8	7.6
O2 -concentration after 6 minutes [mg/L]	7.0	7.0	7.5	8.2	8.9	7.5	7.5	7.5	6.5	6.0
O2consumption rate [mg/L in 6 min]	1.0	1.0	0.9	0.5	0.2	0.7	0.8	1.0	1.3	1.6
O2-consumption rate [mg/Lxh]	10	10	9	5	2	7	8	10	13	16
Specific O2-consumption rate [mg O2/gxh]	7	7	6	3	1	5	5	7	9	11
RS/TSconcentrations[mg/L]	-		1	10	100	1000	500	250	125	62.4
Calculation of inhibition respiration[%]	-	-	10	50	80	30	20	0	-30	-60

Legend: TS = test item, RS = reference item, BC = blank control

Validity criteria fulfilled:

yes

Remarks:

Validity criteria of the applied guideline were fulfilled.

Conclusions:

The study is regarded as a valid guideline study conducted under certificated GLP compliance. According to the reported EC50 value (> 1000 mg/L, nominal) the test substance is not acutely toxic towards aquatic microorganisms. The same result is expected for the organic constituents of target substance since it has the same composition as the source substance.

Executive summary:

The toxicity of Acetic acid, oxo-, sodium salt, reaction products with ethylenediamine and phenol, iron sodium salts (CAS 84539-55-9) towards freshwater microorganisms was investigated in accordance to OECD Guideline 209 / EU Method C11. Activated sludge was collected from the aeration tank at a municipal wastewater treatment. Aliquots of the stock solutions with test- or reference substance were pipetted into test vessels and made up with demineralized water to a volume of 150 mL. After that 8 mL synthetic medium were given to the test vessel. To prepare the blank control assays 150 mL of demineralized water and 8 mL synthetic medium were given to the blank control test vessels. The pH-values were measured in all test vessels. An adjustment was not necessary. 42 mL demineralized water were added to each test vessel. After addition of 50 mL of the inoculum suspension (dry weight 7.5 g/L) the incubation was started by aeration of the test vessels with pressure air. The vessels for the blank control assays were prepared according to the same procedure without addition of test- or reference item. After 180 minutes incubation the mixtures in the test vessels were placed subsequently into a closed oxygen measuring cell. As a result, an EC50(3h) and EC80(3h) > 1000 mg/L and an EC10(3h): 450 mg/L is reported.

Reference 2

Endpoint:

activated sludge nitrification inhibition testing

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

Please refer to Read Across Statement attached in Section 13

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1.33 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

inhibition of nitrification rate

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

4.67 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

inhibition of nitrification rate

Duration:

3 h

Dose descriptor:

other: IC20

Effect conc.:

2.13 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

inhibition of nitrification rate

The target substance contains 7.5 % Zn ions. Therefore, the hazard value for Zn ion is converted to the target substance considering a Zn content of 7.5 %.

IC50 (Zn ion) = 0.35 mg/L

IC50 (target substance) = 0.35/0.075 = 4.67 mg/L

IC20 (Zn ion) = 0.16 mg/L

IC20 (target substance) = 0.16/0.075 = 2.13 mg/L

NOEC (Zn ion) = 0.1 mg/L

NOEC (target substance) = 0.1/0.075 = 1.33 mg/L

Conclusions:

The nitrite and nitrate production in nitrification decreases as the concentration of heavy metals increases. Consequently, the % inhibition increases as the concentration of heavy metals increases. The no observed effect concentration is 0.1 mg Zn/L, the IC20 is reached at 0.16 mg/L Zn2+ and the IC50 is reached at 0.35 mg/L Zn2+.
As the target substance contains 7.5 % Zinc ion the no observed effect concentration for the target substance is 1.33 mg/L, the IC20 is reached at 2.13 mg/L and the IC50 is reached at 4.67 mg/L.

Executive summary:

In this study the ISO 9509 test was used to assess the inhibitory effect of Zn²⁺ ion nitrification of municipal wastewater samples using activated sludge collected from a municipal wastewater treatment plant. The nitrite and nitrate production in nitrification decreases as the concentration of heavy metals increases. The no observed effect concentration is 0.1 mg Zn/L, the IC₂₀ is reached at 0.16 mg/L Zn²⁺ and the IC₅₀ is reached at 0.35 mg/L Zn²⁺.

This result is also relevant for the target substance, which contains 7.5 % zinc ions. Accounting to the Zn content of 7.5 %, this corresponds to a no observed effect concentration of 1.33 mg/L, an IC20 of 2.13 mg/L and an IC50 of 4.67 mg/L.

Description of key information

In an activated sludge respiration inhibition test (OECD TG 209, GLP) Fe(Na)EDDHA was used as test substances. An EC50(3 h) value of > 1000 mg/L was obtained (BASF 2010). Hence, the substance can be regarded as non-toxic to microorganisms present in sewage treatment plants.

With regard to zinc the key value for chemical safety assessment for toxicity to microorganisms is obtained in an activated sludge inhibition test (ISO 9509). An IC50 (3 h) of 0.35 mg Zn/L was determined (Juliastuti 2003). Converted to the zinc moiety in the target substance taking into account the maximum amount of zinc in the target substance, this key value corresponds to an IC50 (3 h) of 4.67 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

4.67 mg/L

EC10 or NOEC for microorganisms:

1.33 mg/L

Additional information

Read-across - Zinc Ion

Juliastuti et al., 2003

In this study the ISO 9509 test was used to assess the inhibitory effect of Zn²⁺ ion nitrification of municipal wastewater samples using activated sludge collected from a municipal wastewater treatment plant. The nitrite and nitrate production in nitrification decreases as the concentration of heavy metals increases. The no observed effect concentration is 0.1 mg Zn/L, the IC₂₀ is reached at 0.16 mg/L Zn²⁺ and the IC₅₀ is reached at 0.35 mg/L Zn²⁺. This result is also relevant for the target substance, which contains 7.5 % zinc ions. Accounting to the Zn content of 7.5 %, this corresponds to a no observed effect concentration of 1.33 mg/L, an IC20 of 2.13 mg/L and an IC50 of 4.67 mg/L.