Zinc Chelate Complex

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

September 2020 - February 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Principles of method if other than guideline:

The test item is a sparingly soluble substance, which hydrolyses in aqueous solutions resulting in an organic compound and copper. Therefore, Water Accommodated Fractions (WAFs) with the loading rates of 0.10, 0.32, 1.0, 3.2 and 10 mg/L were tested to assess the toxicity of the test item to daphnids.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Storage Conditions: Room temperature. Keep in a cool, dry place. Store below 40 °C; keep away from excessive humidity. Storing under dry conditions or with desiccant is preferred. Keep away from sunlight

Analytical monitoring:

yes

Details on sampling:

The test item is a sparingly soluble substance which hydrolyses immediately after application to aqueous solutions leading to the release of an organic compound and formation of copper. As analytical determination of the organic compound was not feasible (due to the low applied concentrations of test item resulting in concentrations of the organic compound below the limit of detection of the analytical method), the biological results are expressed based on loading rates.

Vehicle:

no

Details on test solutions:

The preparation of the test media was based on the OECD Guidance Document No. 23 on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2000. For preparation of the WAFs, individual dispersions of the test item with the loading rates of 3.2 and 10 mg/L were prepared. The dispersions were intensively stirred for 3 hours to dissolve a maximum amount of the test item in the dispersions. After stirring, each of the dispersions was filtered through a membrane filter (0.45 µm). These resulting undiluted filtrates were tested as WAFs. Due to technical reasons (operational constraints on the precision of direct weighing of test item), the WAFs with the lower loading rates of 0.32 and 1.0 mg/L were prepared as dilutions of the filtrate of the WAF with the loading rate of 3.2 mg/L. Additionally, a control group (test water without test item) was tested in parallel.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna Straus
- Strain/clone: a clone of this species (originally from the Daphnia Collection of the University of Basel/Switzerland in 2015) bred in tzest lab
- Age at study initiation (mean and range, SD): 6-24 hours old
- Method of breeding: 3 times a week; feeding with green algae suspension
- Feeding: no feeding of daphnids during study
- Source: test lab
- Lightning: a 16-hour light to 8-hour dark cycle with a 30-minute transition period was used. Light intensity during the light period was 16.4 – 16.6 µmol m-2 s-1

Test type:

semi-static

Water media type:

other: reconstituted test water (ISO Test water) according to OECD Guideline No. 202 was used

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

none

Hardness:

2.5 mmol/L (250 mg/L as CaCO3)

Test temperature:

The water temperature during the test was between 20 and 21 °C.

pH:

The pH values were between 7.6 and 8.0.

Dissolved oxygen:

At the beginning and end of the medium renewal periods, the dissolved oxygen concentration in the test media and the control was at least 7.8 mg/L

Salinity:

Reconstituted water used

Nominal and measured concentrations:

The test item is a sparingly soluble substance, which hydrolyses in aqueous solutions resulting in an organic compound and copper. Therefore, Water Accommodated Fractions (WAFs) with the loading rates of 0.10, 0.32, 1.0, 3.2 and 10 mg/L were tested to assess the toxicity of the test item to daphnids.

Details on test conditions:

The test was performed using glass tubes completely filled (without headspace) with test medium that were tightly sealed with glass stoppers to avoid possible losses of volatile components of the test item by evaporation (closed system).

Reference substance (positive control):

yes

Key result

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

8.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: concentration based on loading rate

Key result

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

5.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: concentration based on loading rate

Details on results:

After 48 hours exposure, no immobilized test organisms were observed in the control and in the loading rates up to and including 3.2 mg/L. However, at the loading rate of 1.0 mg/L, 1 daphnid was found to show reduced swimming activity. Nevertheless, since it represents only 10 % and there was no dose response effect (at the next higher test item concentration there was no immobility or symptoms), it was not considered as a toxic effect of the test item. At the loading rate of 10 mg/L, 19 daphnids (i.e., 95 % of the daphnids) were found to be immobile and 1 daphnid was found to have reduced swimming activity. At the loading rate of 32 mg/L (mean measured 2.8 mg/L zinc), 100 % of the daphnids were previously found to be immobile after 24 hours. The 48-hour EL50 of the test item was calculated to be 5.9 mg/L with 95% confidence limits of 4.8 and 7.2 mg/L.

Results with reference substance (positive control):

Checked twice a year; the result of the latest positive control test in November 2020 (24-hour EC50: 1.6 mg/L) showed that the sensitivity of the test organisms was within the range given by the guideline (OECD 202: 24-hour EC50: 0.60-2.1 mg/L).

Reported statistics and error estimates:

The 24 and 48-hour EL/EC50 and the 95 % confidence limits were calculated by Weibull analysis or Probit analysis using linear maximum likelihood regression, where appropriate.

Validity criteria fulfilled:

yes

Conclusions:

The biological results are expressed based on loading rates, since the test item is a sparingly soluble compound, which hydrolyses immediately after being applied to aqueous solutions. The EL50 (48h) on Daphnia Magna was found to be 5.9 mg/L based on loading rate.

Executive summary:

The acute toxicity of the test item to Daphnia magna was determined in a 48‑hour test according to the OECD Guideline for Testing of Chemicals, No. 202 (2004) and the Commission Regulation (EC) No. 440/2008, Part C.2. The test item is a sparingly soluble substance, which hydrolyses in aqueous solutions resulting in an organic degradation product and copper. Therefore, Water Accommodated Fractions (WAFs) with the loading rates of 0.32, 1.0, 3.2, 10 and 32 mg/L were tested to assess the toxicity of the test item to daphnids. The test was performed using glass tubes completely filled (without headspace) with test medium that were tightly sealed with glass stoppers to avoid possible losses of volatile components of the test item by evaporation (closed system).

A semi-static test design with a test medium renewal after 24 hours was used. For preparation of the WAFs, individual dispersions of the test item with the loading rates of 3.2, 10 and 32 mg/L were prepared. The dispersions were intensively stirred for 3 hours to dissolve a maximum amount of the test item in the dispersions. After stirring, each of the dispersions was filtered through a membrane filter (0.45 µm).These resulting undiluted filtrates were tested as WAFs. The preparation of the test media was based on the OECD Guidance Document No. 23 (Second Edition) on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2019.

The biological results are expressed based on loading rates, since the test item isa sparingly soluble compound, which hydrolyses immediately after being applied to aqueous solutions, forming an organic degradation product and copper. The EL50 (48h) on Daphnia Magna was found to be 5.9 mg/L based on loading rate.

Description of key information

The acute toxicity of the test item to Daphnia magna was determined in a 48‑hour test according to the OECD Guideline for Testing of Chemicals, No. 202 (2004) and the Commission Regulation (EC) No. 440/2008, Part C.2. The test item is a sparingly soluble substance, which hydrolyses in aqueous solutions resulting in an organic degradation product and copper. Therefore, Water Accommodated Fractions (WAFs) with the loading rates of 0.32, 1.0, 3.2, 10 and 32 mg/L were tested to assess the toxicity of the test item to daphnids. The test was performed using glass tubes completely filled (without headspace) with test medium that were tightly sealed with glass stoppers to avoid possible losses of volatile components of the test item by evaporation (closed system).

A semi-static test design with a test medium renewal after 24 hours was used. For preparation of the WAFs, individual dispersions of the test item with the loading rates of 3.2, 10 and 32 mg/L were prepared. The dispersions were intensively stirred for 3 hours to dissolve a maximum amount of the test item in the dispersions. After stirring, each of the dispersions was filtered through a membrane filter (0.45 µm).These resulting undiluted filtrates were tested as WAFs.The preparation of the test media was based on the OECD Guidance Document No. 23 (Second Edition) on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2019.

The biological results are expressed based on loading rates, since the test item isa sparingly soluble compound, which hydrolyses immediately after being applied to aqueous solutions, forming an organic degradation product and copper.The EL50 (48h) on Daphnia Magna was found to be 5.9 mg/L based on loading rate.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

5.9 mg/L