1-ethylazepan-2-one

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:

23 Apr - 03 May 2018

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

GLP compliance:

yes

Analytical monitoring:

yes

Remarks:

UPLC

Details on sampling:

- Concentrations: Control and all test concentrations at test start (0 h) and test end (48 h)
- Sampling method: 2.0 mL from the approximate centre of the test vessels. At the end of the exposure period, the replicates were pooled at each concentration before sampling. Additionally, reserve samples of 2.0 mL were also taken.
- Sample storage conditions before analysis: Freezer (≤ - 15 °C) for a maximum of three monthes after delivery of the draft report

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Test item: The test item was a colourless to pale yellow liquid with a purity of 99.57% and completely soluble in the test medium at the concentrations tested. No correction was made for the purity/composition of the test item.
- Method of preparation: First, the 100 mg/L test solution was prepared by application of approximately 15 min magnetic stirring for acceleration of the dissolution process of the test item in the test medium. Lower concentration were prepared by subsequent dilutions of the limit concentration in test medium.
- Differential loading: No
- Controls: Test medium without test item
- Evidence of undissolved material: All test solutions were clear and colorless at the end of the preparation procedure.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Waterflea
- Source: In-house laboratory culture with known history
- Age of parental stock: 2nd to 5th brood
- Age of daphnia at test start: < 24 h from parental daphnids of more than 2 weeks old
- Breeding: Approximately 250 newborn daphnids (< 3 d old) were placed in 5 L culture medium in an all-glass culture vessel. After 7 d of cultivation, half of the medium was renewed twice a week; Maximum age of cultures: 4 weeks; Temperature of medium: 18 - 22 °C; Culture medium: M7, according to Elendt-Schneider (Elendt, B.P. 1990, Protoplasma 154, 25-33)
- Feeding during Breeding: A suspension of freshwater algae, administered daily.
- Feeding during test: No feeding during test

ACCLIMATION
- Acclimation period: None. Daphnids were introduced 15 min after preparation of the test solutions.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

180 mg/L CaCO3 (test medium)

Test temperature:

19 - 21 °C

pH:

Control: 8.0 (0 h), 8.4 (48 h)
Limit concentration: 8.0 (0 h), 8.3 (48 h)

Dissolved oxygen:

Control: 8.9 mg/L (0 h), 9.4 mg/L (48 h)
Limit concentration: 8.9 mg/L (0 h), 9.4 mg/L (48 h)

Nominal and measured concentrations:

Control and 100 mg/L (nominal)
Control and 88 - 91 mg/L (measured)

Details on test conditions:

TEST SYSTEM
- Test vessel: 60 mL all-glass vessels filled with 50 mL test solution
- Aeration: No aeration of the test solutions
- No. of organisms per vessel: 5 per vessel
- No. of vessels per concentration (replicates): 4 (limit concentration) and 2 (range-finder concentrations)
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The test medium was prepared in tap water purified by Reverse Osmosis (RO-water, GEON Waterbehandeling, The Netherlands)
- Culture medium different from test medium: Culture medium (M7, Elendt 1990) different from test medium (ISO medium, according to guideline).
- Intervals of water quality measurement: pH and dissolved oxygen were measured at the begining (0 h) and at the end of the test (48 h) in the control and limit concentration. The temperature of the medium was continuously measured in a temperature contol vessel.

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 16 h light, 8 h dark

EFFECT PARAMETERS MEASURED:
- Immobility (including mortality): 24 h and 48 h

RANGE-FINDING STUDY
- Test concentrations: 0.10, 1.0 and 10 mg/L (from combined limit/range-finding test)
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (K2Cr2O7)

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Behavioural abnormalities: No
- Mortality of control: 0%
- Any observations that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: No

Results with reference substance (positive control):

- Results with reference substance valid? Yes, the results were within the expected range and in agreement with historical in-house data.
- EC50 (48 h) = 0.33 mg/L (95% CI: 0.29 - 0.38 mg/L).
- Other: The reference test dates from 19 - 21 Mar 2018 and was performed according to OECD testing guideline 202 using potassium dichromate (K2Cr2O7) as reference substance.

Reported statistics and error estimates:

The EC50 could not be calculated because no effects were observed.

VALIDITY CRITERIA

The study fulfilled the validity criteria defined by the testing guideline (Table 1) and is thus considered reliable and valid.

Table 1: Validity criteria for OECD 202.

Criterion from the guideline	Outcome	Validity criterion fulfilled
In the control, including the control containing the solubilising agent, not more than 10% of the daphnids should have been immobilized.	No mortality or any other signs of (sub-lethal) toxicity were observed in the control.	Yes
The dissolved oxygen concentration at the end of the test should be ≥ 3 mg/L in control and test vessels.	The dissolved oxygen concentration was ≥ 3 mg/L at the end of the test in control and test vessels.	Yes

 

ANALYTICAL RESULTS

The measured test item concentration in the limit concentration was 88 – 91% of nominal throughout the exposure period. Thus, effect parameters were expressed in terms of the analytically confirmed nominal concentration.

BIOLOGICAL RESULTS

No immobility was observed in the control and at any of the test concentrations throughout the exposure period, resulting in an EC50 (48 h) of > 100 mg/L.

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Description of key information

Not acutely toxic to aquatic invertebrates. EC50 (48 h) >100 mg/L (nominal).

Additional information

One study investigating the acute toxicity of N-ethylcaprolactam to aquatic invertebrates is available. The study was conducted according to OECD 202 at static test conditions with Daphnia magna. The test animals were exposed to a limit concentration of 100 mg/L for 48 hours. The test substance concentration was analytically verified via Ultra Performance Liquid Chromatography (UPLC). The measured test concentration was 88 – 91% of the nominal test concentration.  Thus, the effect concentration was based on the nominal test concentration. No immobilisation or behavioural abnormalities were observed in the course of the test. The determined EC50 (48 h) was >100 mg/L (nominal).
Based on the results of the acute toxicity testing N-ethylcaprolactam is considered not acutely toxic to aquatic invertebrates.