2-amino-6-methyl-1,2,4-triazolo[1,5-a]pyrimidin-5(1H)-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:

20 January 2016 to 20 February 2016

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

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: The concentrations of test substance were analyzed in one of the duplicate test medium samples of all test concentrations from the sampling times of 0 and 48 hours.
- Sampling method: Samples were taken from each treatment before the start of the test and after 48 hours. Duplicate samples were taken for further analysis if necessary.
- Sample storage conditions before analysis: All samples were stored frozen immediately after sampling.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A nominal amount of test item (100 mg) was dissolved in test water and the volume adjusted to 1 liter to give the required test concentration of 100 mg/L.
- Controls: Test water (ISO reconstituted test water)
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): No remarkable observations, clear colorless test medium

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Strain: Straus
- Source: originally supplied by the University of Sheffield, UK in 2002 and cloned and bred since that time in the test laboratory.
- Age of parental stock (mean and range, SD): At the start of the test, the organisms used were less than 24 hours old and were not first brood progeny.
- Feeding during test: the daphnia were not fed during the test.


For evaluation of the quality of the daphnia clone in the laboratory and the experimental conditions, potassium dichromate is tested as a positive control twice a year.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Test temperature:

22 °C

pH:

7.8 to 7.9 in control vessels, 6.8 - 7.6 in the treated vessels.

Dissolved oxygen:

8.3 to 8.8

Nominal and measured concentrations:

Chemical analysis of the 100 mg/L test preparation at 0 and 48 hours showed a measured concentration of 98% of nominal was obtained indicating that the test system had been correctly dosed and that the test item was stable over the 48-Hour test period. It was therefore considered appropriate to estimate the EC50 and NOEC values based on the nominal test concentration only.

Details on test conditions:

TEST SYSTEM
- Test vessel: 150 mL glass beakers covered to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4


OTHER TEST CONDITIONS
- Adjustment of pH: None
- Photoperiod: A 16-hour light to 8-Hour dark cycle with a 20 minute transition period was used.
- Light intensity: 521 to 704 Lux.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The immobility of the daphnids was determined by visual inspection after 24 and 48 hours of exposure. Those daphnids that were not able to swim within 15 seconds after gentle agitation of the test vessel were considered to be immobilised.

RANGE-FINDING STUDY
- Test concentrations: 0.1, 1, 10 and 100 mg/L.
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

no

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

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Behavioural abnormalities: No signs of stress (e.g. unusual behavior such as trapping at the water surface) were observed
- Other biological observations: None reported
- Mortality of control: No
- Other adverse effects control: None
- Abnormal responses: No
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: The control and 100 mg/L test concentration were observed to be clear colorless solutions.
- Effect concentrations exceeding solubility of substance in test medium: Not reported

The limit of quantification in this study was 11.6 mg/L. Nominal concentrations were used for the calculation and reporting of results.

Table 1: Analytical results

Nominal concentrations (mg/L)	% of nominal measured at 0 hours	% of nominal measured at 48 hours
100	103	97

 

The 24 and 48-Hhour EC₅₀and the NOEC were estimated by inspection of the data. There was no immobility observed in the dilution water control.Immobility data and estimated EC₅₀valuesare shown in the table below:

Table 2: Effects of the test material on Daphnia magna following exposure for 48-hours in a static test

Nominal concentration	Immobilised daphnids after 24 hours		Immobilised daphnids after 48 hours
(mg/L)	Number	%	Number	%
Dilution water control	0	0	0	0
100	0	0	1	5
EC50mg/L	>100		>100
95% Confidence limits	n.d.		n.d.
NOEC	100		100

n.d. – not determined

Validity criteria fulfilled:

yes

Conclusions:

The 48-hour EC50 of the test substance to Daphnia magna was > 100 mg/L. The NOEC was 100 mg/L.

Executive summary:

The acute toxicity of the test material to Daphnia magna was determined under static conditions according to OECD Guideline 202 and EU Method C.2. Daphnids were exposed to a single nominal concentration of 100 mg/L alongside a dilution water control. Based on nominal concentrations, the 48-hour EC₅₀was >100 mg/L.

Description of key information

The acute toxicity of the test material to Daphnia magna was determined under static conditions according to OECD Guideline 202 and EU Method C.2.

The 48-hour EC50 of the test substance to Daphnia magna was >100 mg/L.  The NOEC was 100 mg/L.