[No public or meaningful name is available]

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 January 2018 -04 July 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Test material form:

semi-solid (amorphous): gel

Sampling and analysis

Analytical monitoring:

no

Remarks:

Due to the low aqueous solubility and complex nature of the test item, for the purposes of the test, the test medium was prepared as a Water Accommodated Fraction (WAF).

Details on sampling:

The results were based on nominal loading rates only.

Test solutions

Vehicle:

no

Details on test solutions:

Nominal amounts of test item (5.0, 9.0, 16, 28 and 50 mg) were each separately added to a glass slide and suspended in the water column of 5 liters of test water to give the 1.0, 1.8, 3.2, 5.6 and 10 mg/L loading rates respectively. After the addition of the test item, the test water was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 95 hours and the mixtures allowed to stand for 1-Hour. Observations made on the WAFs indicated that a significant amount of dispersed test item was present in the water column and hence it was considered justifiable to remove the WAFs by filtering through a glass wool plug (2 to 4 cm in length). A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. A glass wool plug was inserted into the opposite end of the tubing and the WAF removed by mid-depth siphoning (the first 75 to 100 mL discarded) to give the 1.0, 1.8, 3.2, 5.6 and 10 mg/L loading rate WAFs. Microscopic observations of the WAFs were performed after filtering and showed no test item present.
The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0, 24 and 48 hours

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

The test was carried out using first instar Daphnia magna derived from in-house laboratory cultures.
Adult daphnids were maintained in 150 mL glass beakers containing 100 mL Elendt M7 medium in a temperature controlled room maintaining the water temperature at 18 to 22 °C. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Each culture was fed daily with a mixture of algal suspension (Desmodesmus subspicatus) and Tetramin® flake food suspension. Culture conditions ensured that reproduction was by parthenogenesis. Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24 hours old. These young were removed from the cultures and used for testing. The diet and diluent water are considered not to contain any contaminant that would affect the integrity or outcome of the study.

Study design

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

pH:

7.6-7.7

Dissolved oxygen:

8.5-9.1

Nominal and measured concentrations:

Based on the results of the range-finding test the following loading rates were assigned to the definitive test: 1.0, 1.8, 3.2, 5.6 and 10 mg/L.

Details on test conditions:

Nominal amounts of test item (5.0, 9.0, 16, 28 and 50 mg) were each separately added to a glass slide and suspended in the water column of 5 liters of test water to give the 1.0, 1.8, 3.2, 5.6 and 10 mg/L loading rates respectively. After the addition of the test item, the test water was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 95 hours and the mixtures allowed to stand for 1-Hour. Observations made on the WAFs indicated that a significant amount of dispersed test item was present in the water column and hence it was considered justifiable to remove the WAFs by filtering through a glass wool plug (2 to 4 cm in length). A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. A glass wool plug was inserted into the opposite end of the tubing and the WAF removed by mid-depth siphoning (the first 75 to 100 mL discarded) to give the 1.0, 1.8, 3.2, 5.6 and 10 mg/L loading rate WAFs. Microscopic observations of the WAFs were performed after filtering and showed no test item present.
The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0, 24 and 48 hours

Reference substance (positive control):

yes

Remarks:

A positive control (Envigo study number LK67NP) used potassium dichromate as the reference item at concentrations of 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L. Exposure conditions for the positive control were similar to those in the definitive test.

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

ca. 1 mg/L

Conc. based on:

test mat. (dissolved fraction)

Remarks:

Water accomodated fraction

Basis for effect:

mobility

Effect concentrations 2

Key result

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Results with reference substance (positive control):

reference item at concentrations of 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L.
Exposure conditions for the positive control were similar to those in the definitive test.
Analysis of the immobilization data was carried out using the Trimmed Spearman-Karber method at 24 hours and the Binomial Distribution method at 48 hours.

48 hr EC50 = 0.75 mg/L

Reported statistics and error estimates:

95% CL 0.73 - 0.86 mg/L

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

48 hr NOEL = 1 mg/L

Executive summary:

The test was carried out using first instar Daphnia magna derived from in-house laboratory cultures.

Adult daphnids were maintained in 150 mL glass beakers containing 100 mL Elendt M7 medium (see Annex 2) in a temperature controlled room maintaining the water temperature at 18 to 22 °C. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Each culture was fed daily with a mixture of algal suspension (Desmodesmus subspicatus) and Tetramin® flake food suspension. Culture conditions ensured that reproduction was by parthenogenesis. Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24 hours old. These young were removed from the cultures and used for testing. The diet and diluent water are considered not to contain any contaminant that would affect the integrity or outcome of the study.

LOEL rates were considered to be 3.2 and 1.8 mg/L loading rate WAF.

The slopes and their standard errors of the response curves at 24 and 48 hours were 13 (standard error = 0.019) and 26 (standard error = 0.76) respectively.

No sub-lethal effects of exposure were observed throughout the test.