2,3,3-trimethyl-3H-indole-5-carboxylic acid

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:

other information

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 (incl. QA statement)

Analytical monitoring:

yes

Remarks:

HPLC

Details on sampling:

Chemical analysis of test concentrations: At start and at end of exposure

Control and test solutions were sampled in duplicate. The duplicate samples were kept separately as a reserve. The nominal volume per sample was 10 mL. The samples were stabilised by adding acetonitrile directly after sampling (acetonitrile volume: 50% of the total sample volume; 10 mL of sample was mixed with 10 mL of acetonitrile). The volume of each sample was recorded.

Vehicle:

no

Remarks:

stirring and ultrasonication

Details on test solutions:

Preparation of Stock and Test Solutions:
- stock solution was prepared by adding 100.0 mg of the test item to 1000 mL of the test medium
- stock solution was stirred (900 rpm) for 30 minutes and treated additional with ultrasonication three times for 5 min at ambient temperature
- stock solution was left to settle for 10 minutes
- stock solution was visually examined for undissolved/particulate matter in the free water column, visual inspection of the flask showed a clear solution
The volume of the stock solution was large enough to prepare the test concentrations and all analytical samples.

Test organisms (species):

Daphnia magna

Details on test organisms:

Test Organism:
- Species: Daphnia magna STRAUS (clone M10), cultured at ECT Oekotoxikologie GmbH since December 22, 2011
- Origin: Organisms were originally supplied by KU Leuven, Belgium
- Age of parental daphnids: less than 35 d
- Age of the daphnids at the beginning of the test: less than 24 h

Holding conditions:
- Material of stock vessel: Glass
- Volume of medium per stock vessel: 1.8 L
- Depth of medium in the stock vessel: Approximately 14.5 cm
- Number of daphnids kept as stock per culture vessel (batch size): Approximately 20
- Separation of adult and young daphnids: 2-5 times per week
- Medium: Elendt medium M4
- Renewal of medium: Twice per week
- Temperature: Within required ranges (20 +- 2°C)
- Photoperiod (light/dark): 16/8 h
- Light intensity: Within required ranges (50 to 1000 lx)
- Aeration: None
- Food: algae (Desmodesmus subspicatus), instant baker’s yeast suspension, TetraMin® suspension
- Feeding frequency: 4 times per week

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

14.2 °dH (= 254 mg/L CaCO3)

Test temperature:

19.4 - 20.9 °C

pH:

6.2 - 7.7

Dissolved oxygen:

7.8 - 8.4 mg/L O2, 88 - 93 %

Salinity:

n.a.

Conductivity:

No data

Nominal and measured concentrations:

Nominal [mg/L]: 6.25, 12.5, 25.0, 50.0, 100.0

The test item concentration was stable during the test period, with >90% of the nominal concentration found in the fresh and aged solution.

Details on test conditions:

EXPOSURE CONDITIONS:
- Volume of test solution per test vessel: 50-60 mL
- Test medium: medium M4 (OECD 2004)
- Adjustment of pH in the medium: none
- Application of test item: test item dissolved in Medium M4 applied once at the beginning of the test
- Aeration of test vessels: none
- Test units: 100-mL glass beakers, closed by watch glass
- Volume of test solution per test vessel: 50-60 mL
- Number of daphnids per test vessel: 5
- Test concentrations (nominal): Control, 6.25, 12.5, 25.0, 50.0 and 100 mg test item/L
- Number of replicates per concentration: 4
- Number of replicates in the controls: 4
- Renewal of the test solution during the test period: static, no renewal
- Feeding during exposure: none
- Temperature (target): 18 to 22°C, constant within a range of 2°C
- Light intensity (target): 50 to 1000 lx
- Light regime: 16 h light; 8 h dark
- Biological parameter: immobility

WATER QUALITY MEASUREMENTS:
At start of the test, after temperature adaptation of the test solutions, and at the end of the test the following parameters were measured and recorded in one replicate test vessel of the control and the highest test concentration:
- Temperature
- pH
- Dissolved oxygen content in % of air saturation value (ASV) and in mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate (K2Cr2O7)

Key result

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:

No immobility was observed in the control or in all test concentrations up to and including 100 mg test item/L. It is therefore concluded that the EC50 of the test item is higher than the highest concentration tested (nominal: 100 mg test item/L) which equals 95.0 mg/L test item based on measured concentration.

Results with reference substance (positive control):

The most recent reference test with potassium dichromate performed in a separate study (Study No. IDA1711) resulted in an EC50(24 h) of 0.74 mg/L.

Reported statistics and error estimates:

In this dose response test, no immobilities were observed in the control or in all concentration up to 100 mg test item/L. A statistical evaluation for differences between treatment and control was therefore not required and was not performed.

Validity criteria fulfilled:

yes

Remarks:

immobilisation and other abnormalities in the controls did not exceed 10% by the end of the test; dissolved oxygen concentration remained above 3 mg/L throughout the exposure period

Conclusions:

No toxic effects against daphnia were observed in all test concentrations up to and including 100 mg/L under exposure conditions. It is therefore concluded that the EC50 of the test item 2,3,3-trimethyl-3H-indole-5-carboxylic acid is higher than the highest test concentration tested (nominal: 100 mg test item/L).

Executive summary:

The study was performed according to Method C.2 ‘Acute toxicity for Daphnia’ (1992), described in the Council Regulation (EC) No 92/69, which is equivalent to OECD Guideline for Testing of Chemicals No. 202 'Daphnia sp., Acute Immobilization Test'. Daphnids were exposed to a series of concentrations of 2,3,3-trimethyl-3H-indole-5-carboxylic acid (6.25, 12.5, 25.0, 50.0 and 100 mg test item/L) in aqueous solution as well as to controls without the test item for a period of 48 hours under static conditions. 20 daphnids were tested per concentration and control (5 daphnids/vessel, 4 replicates). During the test period the test solutions were not aerated. The daphnids were not fed. Those animals not able to swim within 15 seconds after gentle agitation of the test vessel were considered to be immobile. To verify the nominally applied concentrations, samples were taken from the test solutions and analytically measured. The samples designated for chemical analysis were shipped to the analytical test site and analysed under the responsibility of the principal investigator for analysis. No toxic effects against daphnia were observed in all test concentrations up to and including 100 mg/L under exposure conditions. Therefore a 48h-EC50 of > 100 mg/L was determined for 2,3,3-trimethyl-3H-indole-5-carboxylic acid.

Description of key information

The study was performed according to Method C.2 ‘Acute toxicity for Daphnia’ (1992), described in the Council Regulation (EC) No 92/69, which is equivalent to OECD Guideline for Testing of Chemicals No. 202 'Daphnia sp., Acute Immobilization Test'. Daphnids were exposed to a series of concentrations of 2,3,3-trimethyl-3H-indole-5-carboxylic acid (6.25, 12.5, 25.0, 50.0 and 100 mg test item/L) in aqueous solution as well as to controls without the test item for a period of 48 hours under static conditions. 20 daphnids were tested per concentration and control (5 daphnids/vessel, 4 replicates). During the test period the test solutions were not aerated. The daphnids were not fed. Those animals not able to swim within 15 seconds after gentle agitation of the test vessel were considered to be immobile. To verify the nominally applied concentrations, samples were taken from the test solutions and analytically measured. No toxic effects against daphnia were observed in all test concentrations up to and including 100 mg/L under exposure conditions. Therefore a 48h-EC50 of > 100 mg/L was determined for 2,3,3-trimethyl-3H-indole-5-carboxylic acid.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L

Additional information

"Should read: EC50 > 100.0 mg/L"