Zinc EDDHA

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

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

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

>= 120 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 120 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

> 120 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Since the analytically determined concentrations of the test substance in the test solutions were within +/- 20 % of the nominal concentrations, the effect concentration can be expressed relative to the nominal concentration.

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50/LC50: The EC50(24h) of the reference substance potassium dichromate was 1.19 mg/L.
- Other: This result is within the range of 0.6 – 2.1 mg/L (ISO 6341) and indicates that the culture of Daphnia magna used in this study is responding normally to toxic stress.

Reported statistics and error estimates:

Since the study is designed as a limit test, no statistical analysis was performed.

Number of mobile daphnids

Nominal concentration [mg/L]	Replicate 1 [h]			Replicate 2 [h]			Replicate 3 [h]			Replicate 4 [h]			∑	∑
	0	24	48	0	24	48	0	24	48	0	24	48	24	48
0 (control)	5	5	5	5	5	5	5	5	5	5	5	5	20	20
120	5	5	5	5	5	5	5	5	5	5	5	5	20	20

Effect concentrations after 24 hours and 48 hours of exposure. The EC values based on nominal concentrations were:

Time [h]	EC0 [mg/L]	EC50 [mg/L]	Confidence limits 95% [mg/L]	EC100 [mg/L]
24	>120	> 120	* – *	> 120
48	>120	> 120	* – *	> 120

*The data were insufficient to determine confidence limits.

Validity criteria fulfilled:

yes

Remarks:

Validity criteria of the test guideline were fulfilled.

Conclusions:

In conclusion the 48 hour EC50 values for FeNaEDDHA in this acute toxicity study with Daphnia magna were > 120 mg/L based on the nominal concentration of the test substance and > 122 mg/L based on the mean measured concentrations. The same result is expected for the organic constituents of target substance since it has the same composition as the source substance.

Executive summary:

This acute toxicity study investigated the effect of Fe(Na)EDDHA on the immobilisation of Daphnia magna according to the principles of OECD Guideline 202 and EU Method C.2. Juvenile daphnids (younger than 24 hour old) were exposed to one concentration of the test substance and compared to a control. Immobilisation of daphnia is determined after 24 and 48 hours of exposure. The test substance was was tested at 120 mg/L. The 48 hour EC50 value for the test substance was greater than 120 mg/L based on the nominal concentration of the test substance and greater than 122 mg/L based on the mean measured concentrations. Since the analytically determined concentrations of the test substance in the test solutions were within +/- 20% of the nominal concentrations, the effect concentration is expressed relative to the nominal concentration for the evaluation of the test substance.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

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:

48 h

Dose descriptor:

EC50

Remarks:

soft water, clone C

Effect conc.:

3.45 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Remarks:

soft water, clone A

Effect conc.:

1.75 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Remarks:

moderate-hard water, clone C

Effect conc.:

14.13 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Remarks:

moderate-hard water, clone A

Effect conc.:

6.09 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Remarks:

hard water, clone C

Effect conc.:

12.83 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Remarks:

hard water, clone A

Effect conc.:

8.01 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

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 % as worst-case value.

EC50 (Zn ion) = 0.259 mg/L

EC50 (target substance) = 0.259/0.075 = 3.45 mg/L

EC50 (Zn ion) = 0.131 mg/L

EC50 (target substance) = 0.131/0.075 = 1.75 mg/L

EC50 (Zn ion) = 1.06 mg/L

EC 50 (target substance) = 1.06/0.075 = 14.13 mg/L

EC50 (Zn ion) = 0.457 mg/L

EC 50 (target substance) = 0.457/0.075 = 6.09 mg/L

EC50 (Zn ion) = 0.962 mg/L

EC 50 (target substance) = 0.962/0.075 = 12.83 mg/L

EC50 (Zn ion) = 0.601 mg/L

EC50 (target substance) = 0.601/0.075 = 8.01 mg/L

Conclusions:

In general, D. magna clones were more sensitive to zinc in soft water relative to hard water. In addition, a significant genetic variability concerning zinc toxicity was shown. The least sensitive clone had the following EC50 (48 h) values: 259 µg/L (soft water), 1060 µg/L (moderate-hard water), 962 µg/L (hard water). The most sensitive clone had the following EC50 (48 h) values: 131 µg/L (soft water), 457 µg/L (moderate-hard water), 601 µg/L (hard water). This result is also relevant for the target substance, which contains 7.5 % zinc ions.

Executive summary:

D. magna clones were exposed to single-metal solutions of varying concentration at two or three levels of water hardness (soft, moderate–hard and hard) for periods ranging from 12–96 h (12 h increments). EC50 values for each metal-, genotype-, water hardness-, exposure period-combination were determined for (i) total metal concentration and (ii) the free hydrated metal ion concentration (predicted using geochemical speciation modeling) and compared using analysis of covariance with environment (water hardness) and genotype (clone) as fixed factors and exposure time as a covariate. Substantial genetic variability occurred in both essential (Zn, Cu) and non essential (Cd, U) metals.

Concerning Zinc, the least sensitive clone had the following EC50 (48 h) values: 259 µg/L (soft water), 1060 µg/L (moderate-hard water), 962 µg/L (hard water). The most sensitive clone had the following EC50 (48 h) values: 131 µg/L (soft water), 457 µg/L (moderate-hard water), 601 µg/L (hard water). This result is also relevant for the target substance, which contains 7.5 % zinc ions. To account for the Zn content of 7.5 %, these values were converted to the target substance.

As a result, the least sensitive clone had the following EC50 (48 h) values: 3.45 mg/L (soft water), 14.13 mg/L (moderate-hard water), 12.83 mg/L (hard water). The most sensitive clone had the following EC50 (48 h) values: 1.75 mg/L (soft water), 6.09 mg/L (moderate-hard water), 8.01 mg/L (hard water).

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

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:

48 h

Dose descriptor:

EC50

Remarks:

pH 8, DOC 7.49 mg/L, Ca 52.7 mg/L

Effect conc.:

43.87 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Remarks:

pH 7.3, DOC 2.53 mg/L, Ca 5 mg/L

Effect conc.:

4.72 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Remarks:

converted to target substance

Basis for effect:

mobility

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 % as worst-case value.

EC50 (Zn ion) = 3.29 mg/L

EC 50 (target substance) = 3.29/0.075 = 43.87 mg/L

EC50 (Zn ion) = 0.354 mg/L

EC 50 (target substance) = 0.354/0.075 = 4.72 mg/L

Conclusions:

Both inorganic and organic Zn complexation reduce Zn2+ activity and thus also reduce toxicity. Inorganic complexation (i. e. ZnCO3) is relatively straightforward, while dissolved organic matter (DOM) vary much in their zinc-binding characteristics. Therefore, for unknown samples, it is suggested to assume that the DOM consists of a fixed fraction of chemically active fulvic acid, i.e., 61 %, which is the mean of optimal %AFA of the five abovementioned samples with which Zn titration studies were performed. This result is also relevant for the target substance, which contains 7.5 % zinc ions.

Executive summary:

Zinc toxicity to Daphnia magna was evaluated in a series of experiments with spiked natural surface waters. The eight selected freshwater samples had varying levels of bioavailability modifying parameters: pH (5.7–8.4), dissolved organic carbon (DOC, 2.48–22.9 mg/L), Ca (1.5–80 mg/L), Mg (0.79–18 mg/L), and Na (3.8–120 mg/L). In those waters, acute zinc toxicity (expressed as 50% effective concentrations [EC50]) varied up to 9-fold for the D. magna (48-h EC50 from 354 to 3290 µg Zn/L). Both inorganic and organic Zn complexation reduces Zn2+ activity and thus also reduce toxicity. Inorganic complexation (i. e. ZnCO3) is relatively straightforward, while dissolved organic matter (DOM) vary much in their zinc-binding characteristics. Therefore, for unknown samples, it is suggested to assume that the DOM consists of a fixed fraction of chemically active fulvic acid, i.e., 61%, which is the mean of optimal %AFA of the five abovementioned samples with which Zn titration studies were performed. 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 EC 50 values between 4.72 and 43.87 mg/L for the target substance.

Description of key information

An EC50 (48h) value of > 120 mg/L is reported for Fe(Na)EDDHA in a study conducted with D. magna (OECD TG 202, GLP; Salinas (2010)). Thus, the EDDHA chelate is clearly not acutely toxic to aquatic invertebrates.

To address the toxicity of the zinc ion in the target substance the key value for chemical safety assessment for toxicity to invertebrates was set to the lowest EC50 obtained in a test similar to a recommended test method (OECD TG 202). The selected EC50 (48 h) value is 131 µg Zn/L. It was determined in a study with D. magna (Barata 1998). Converted to the zinc moiety in the target substance taking into account the maximum amount of zinc in the target substance, this corresponds to an EC50 (48 h) of 1.75 mg/L for the target substance. For the whole evaluation of the available data on zinc compounds please refer to 'Additional information'.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

1.75 mg/L

Additional information

Read-across - Zn ion

Barata 1998

D. magna clones were exposed to single-metal solutions of varying concentration at two or three levels of water hardness (soft, moderate–hard and hard) for periods ranging from 12–96 h (12 h increments). EC50 values for each metal-, genotype-, water hardness-, exposure period-combination were determined for (i) total metal concentration and (ii) the free hydrated metal ion concentration (predicted using geochemical speciation modeling) and compared using analysis of covariance with environment (water hardness) and genotype (clone) as fixed factors and exposure time as a covariate. Substantial genetic variability occurred in both essential (Zn, Cu) and non essential (Cd, U) metals.

Concerning Zinc, the least sensitive clone had the following EC50 (48 h) values: 259 µg/L (soft water), 1060 µg/L (moderate-hard water), 962 µg/L (hard water). The most sensitive clone had the following EC50 (48 h) values: 131 µg/L (soft water), 457 µg/L (moderate-hard water), 601 µg/L (hard water).

This result is also relevant for the target substance, which contains 7.5 % zinc ions. To account for the Zn content of 7.5 %, these values were converted to the target substance.

As a result, the least sensitive clone had the following EC50 (48 h) values: 3.45 mg/L (soft water), 14.13 mg/L (moderate-hard water), 12.83 mg/L (hard water). The most sensitive clone had the following EC50 (48 h) values: 1.75 mg/L (soft water), 6.09 mg/L (moderate-hard water), 8.01 mg/L (hard water).

De Schamphelaere 2005

Zinc toxicity to Daphnia magna was evaluated in a series of experiments with spiked natural surface waters. The eight selected freshwater samples had varying levels of bioavailability modifying parameters: pH (5.7–8.4), dissolved organic carbon (DOC, 2.48–22.9 mg/L), Ca (1.5–80 mg/L), Mg (0.79–18 mg/L), and Na (3.8–120 mg/L). In those waters, acute zinc toxicity (expressed as 50% effective concentrations [EC50]) varied up to 9-fold for the D. magna (48-h EC50 from 354 to 3290 mg Zn/L). Both inorganic and organic Zn complexation reduces Zn²⁺ activity and thus also reduce toxicity. Inorganic complexation (i. e. ZnCO₃) is relatively straightforward, while dissolved organic matter (DOM) vary much in their zinc-binding characteristics. Therefore, for unknown samples, it is suggested to assume that the DOM consists of a fixed fraction of chemically active fulvic acid, i.e., 61%, which is the mean of optimal %AFA of the five abovementioned samples with which Zn titration studies were performed. 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 EC50 values between 4.72 and 43.87 mg/L for the target substance.