Zinc EDDHA

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

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:

72 h

Dose descriptor:

EC50

Effect conc.:

> 294 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

8.2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

29.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

27.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

8.2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

After 72 h exposure, in test groups up to 32 mg/L no remarkable observations were reported. Concerning the test groups with 100 and 320 mg/L, a low cell density was recorded.

Results with reference substance (positive control):

According to the test ISO guideline 8692 the EC50 values of the reference substance potassium dichromate should be in the range: ErC50 = 0.71 – 0.97 mg/L after 72 hours for Desmodesmus subspicatus. The ErC50(72 h) of the control substance potassium dichromate was 0.82 mg/L. These results indicate that the algae are responding normally to toxicant stress.

Reported statistics and error estimates:

No statistics and error estimates reported.

Validity criteria fulfilled:

yes

Remarks:

The test conformed to all validity criteria of the OECD Guideline used and is valid.

Conclusions:

In conclusion the 72 hour EC50 value for FeNaEDDHA with Desmodesmus subspicatus CHODAT (SAG 86.81) was > 294 mg/L and the NOEC was 8.2 mg/L based on algal growth rate. The 72 hour EC50 based on yield was 27.3 mg/L and the NOEC 2.4 mg/L. 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 toxic effects of Fe(Na)EDDHA on the growth of single-cell green algae as representatives of primary producers in freshwater plankton over a 72 hour static exposure period were determined according to the principles of OECD Guideline 201 and EU Method C.3.

The following nominal concentrations based on test substance mass without a correction for purity were used: 3.2, 10, 32, 100, 320 mg/L. The analytically determined concentrations of the test substance in the test water were in a range of 89 - 102 % of the nominal concentration at start of exposure and decreased to 63 - 86 % of the nominal concentration at the end of exposure. Therefore mean measured concentrations were considered to be an accurate representation of exposure levels throughout the exposure period.

The 72-hour EC50 value for Desmodesmus subspicatus CHODAT (SAG 86.81) was greater than 294 mg/L and the NOEC was 8.2 mg/L based on mean measured concentrations and growth rate. The 72 hour EC50 based on yield and mean measured concentrations was 27.3 mg/L and the NOEC was 2.4 mg/L.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

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

Key result

Duration:

72 h

Dose descriptor:

IC50

Effect conc.:

1.47 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

IC10

Effect conc.:

0.37 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.59 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.27 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

IC50

Remarks:

cells were acclimated to 2 µg Cu/L for 82 d

Effect conc.:

1.31 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth 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) = 0.11 mg/L

IC 50 (target substance) = 0.11/0.075 = 1.47 mg/L

IC10 (Zn ion) = 0.028 mg/L

IC 10 (target substance) = 0.028/0.075 = 0.37 mg/L

LOEC (Zn ion) = 0.044 mg/L

LOEC (target substance) = 0.044/0.075 = 0.59 mg/L

NOEC (Zn ion) = 0.02 mg/L

NOEC (target substance) = 0.02/0.075 = 0.27 mg/L

IC50, acclimated to 2 µg Cu/L (Zn ion) = 0.098 mg/L

IC50, acclimated to 2 µg Cu/L (target substance) = 0.098/0.075 = 1.31 mg/L

Conclusions:

The Chlorella sp. culture acclimated to copper had no increased zinc tolerance compared with that of the nonacclimated algae, nor were there any changes in control growth rates. The IC50 of the non-acclimated culture was 110 µg Zn/L, whereas the culture acclimated to 2 µg Cu/L for 82 days showed an IC50 value of 98 µg Zn/L. The LOEC and NOEC for the non acclimated algae was 44 and 20 µg Zn/L, respectively. This result is also relevant for the target substance, which contains 7.5 % zinc ions.

Executive summary:

Chlorella sp. was acclimated in medium containing 2 µg Cu/L for 100 days. Changes in algal growth rates and copper and zinc tolerance were monitored using standard growth inhibition toxicity tests in minimal medium over 72 h. The acclimated Chlorella sp. culture had no increased zinc tolerance compared with that of the non-acclimated algae, nor were there any changes in control growth rates. The IC50 of the non-acclimated culture was 110 µg Zn/L, whereas the culture acclimated to 2 µg Cu/L for 82 days showed an IC50 value of 98 µg Zn/L. The LOEC and NOEC for the non acclimated algae was 44 and 20 µg Zn/L, respectively. This result is also relevant for the target substance, which contains 7.5 % zinc ions. Converted to the target substance under consideration of the zinc content of 7.5 %, the IC50 value is 1.47 mg/L, IC10 value is 0.37 mg/L, LOEC is 0.59 mg/L and the NOEC is 0.27 mg/L.

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

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:

72 h

Dose descriptor:

EC50

Remarks:

pH 5.7, DOC 6.28 mg/L, Ca 3.45 mg/L

Effect conc.:

27.33 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Remarks:

pH 8.01, DOC 5.89 mg/L, Ca 65.4 mg/L

Effect conc.:

1.41 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Remarks:

pH 7.42, DOC 22.3 mg/L, Ca 43.4 mg/L

Effect conc.:

11.48 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

converted to target substance

Basis for effect:

growth 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 %.

EC50 (Zn ion) = 0.106 mg/L

EC 50 (target substance) = 0.106/0.075 = 1.41 mg/L

EC50 (Zn ion) = 0.861 mg/L

EC 50 (target substance) = 0.861/0.075 = 11.48 mg/L

EC50 (Zn ion) = 2.05 mg/L

EC 50 (target substance) = 2.05/0.075 = 27.33 mg/L

Conclusions:

An increase in Ca, Mg, and Na concentraion and pH value had protective effects on the zinc toxicity. Among these factors, the pH had the most significant effect. 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. This result is also relevant for the target substance, which contains 7.5 % zinc ions. The EC50 values converted to the target substance range between 1.41 and 27.33 mg/L depending on the pH and DOC content.

Executive summary:

Zinc toxicity to a green alga (Pseudokirchneriella subcapitata) 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, chronic zinc toxicity (expressed as 10% effective concentrations [EC10]) varied up to 20-fold for the alga (72-h EC10 from 27.3 to 563 µg Zn/L). An increase in Ca, Mg, and Na concentraion and pH value had protective effects on the zinc toxicity, whereas the pH had the most significant effect. 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. This result is also relevant for the target substance, which contains 7.5 % zinc ions. The EC50 values converted to the target substance range between 1.41 and 27.33 mg/L depending on the pH and DOC content.

Description of key information

Fe(Na)EDDHA was tested in Desmodesmus subspicatus (OECD TG 201, GLP). An E_rC50(72h) of > 294 mg/L and a NOEC_r of 8.2 mg/L were reported (Salinas 2010).

With regard to zinc the key value for chemical safety assessment for freshwater algae is set to the lowest reported EC50 (72 h) value of 0.11 mg Zn/L obtained for Chlorella sp. (Johnson 2007). 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 EC50 (72 h) of 1.47 mg/L. For the whole evaluation of the available data on zinc compounds please refer to 'Additional information'.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.47 mg/L

EC10 or NOEC for freshwater algae:

0.37 mg/L

Additional information

Read-across Zn-ion

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 %.

De Schamphelaere, 2005

Zinc toxicity to a green alga (Pseudokirchneriella subcapitata) 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, chronic zinc toxicity (expressed as 10% effective concentrations [EC10]) varied up to 20-fold for the alga (72-h EC10 from 27.3 to 563 µg Zn/L). An increase in Ca, Mg, and Na concentraion and pH value had protective effects on the zinc toxicity, whereas the pH had the most significant effect. 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. This result is also relevant for the target substance, which contains 7.5 % zinc ions. The EC50 values converted to the target substance range between 1.41 and 27.33 mg/L depending on the pH and DOC content.

Johnson 2007

Chlorella sp. was acclimated in medium containing 2 µg Cu/L for 100 days. Changes in algal growth rates and copper and zinc tolerance were monitored using standard growth inhibition toxicity tests in minimal medium over 72 h. The acclimated Chlorella sp. culture had no increased zinc tolerance compared with that of the nonacclimated algae, nor were there any changes in control growth rates. The IC50 of the non-acclimated culture was 110 µg Zn/L, whereas the culture acclimated to 2 µg Cu/L for 82 days showed an IC50 value of 98 µg Zn/L. The LOEC and NOEC for the non acclimated algae was 44 and 20 µg Zn/L, respectively.

This result is also relevant for the target substance, which contains 7.5 % zinc ions. Converted to the target substance under consideration of the zinc content of 7.5 %, the IC50 value is 1.47 mg/L, IC10 value is 0.37 mg/L, LOEC is 0.59 mg/L and the NOEC is 0.27 mg/L.