5-fluoro-2-methoxypyrimidin-4(3H)-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:

14 June 2005 to 16 June 2005

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)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: As the test material was not found to be toxic at 100 mg/L nominal, chemical analysis was undertaken to measure the concentration of the test material in this solution.
- Sampling method: A sample of 5 mL was taken from the limit test solution (100 mg/L nominal) at the beginning of the test and kept at -20 °C until analysis. An aliquot of the sample was extracted and analysed by High Performance Liquid Chromatography (HPLC) with UV detection at 220 nm.
- Sample preparation before analysis: The samples were thawed and mixed. Then each sample was diluted (20-fold) in mobile phase to achieve concentrations in the range 0.1 to 10 mg/L of test material.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
The stock solutions for the limit and range-finding tests were prepared by dissolving the test material directly in M4 reconstituted water.
- Quantity of test material: 100 mg
- Volume of test water: 1000 mL
- Concentration of test material: 100 mg/L
- Duration of agitation: 5 minutes
Test solutions were prepared by further dilution of the stock solution with M4 recnosituted water to provide a geometric series of concentrations: 0, 0.01, 0.1, 1, 10 and 100 mg/L.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain/clone: STRAUS-clone 5
- Source: Daphnia magna were bred by the testing facility
- Age (mean and range, SD): At the beginning of the test, first instar daphnids between 6 and 24 hours old and produced from parthenogenically reproducing brood female population were allocated for the test.
- Feeding during test: Animals were not fed during the test.

ACCLIMATION
- Acclimation period and conditions: Animals are held in water of the same quality as the test water from birth until use in the test. The medium is replaced generally each Monday, Wednesday and Friday. On each of these occasions, neonates are separated from the adults and either removed or, once monthly, used to start a new culture. During culture, pH, water hardness and dissolved oxygen concentrations are checked in the "new" and "old" media when solutions are replaced generally twice a week.
- Type and amount of food: Culture animals are fed with a diet of between 0.1 and 0.2 mg of carbon per Daphnia per day, in the form of the algal strain Scenedesmus subspicatus which is cultured at the testing facility.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

340 mg CaCO3/L

Test temperature:

20.0 to 20.8 °C

pH:

7.27 to 8.49

Dissolved oxygen:

8.6 to 8.7 mg/L (≥ 60 % of the air saturation value)

Conductivity:

< 10 μS/cm

Nominal and measured concentrations:

- Limit test: 100 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Material, size, headspace, fill volume: Not specified. Test vessels containing daphnids were filled directly from the test solution containers immediately after preparation.
- Aeration: None. Dilution water was aerated prior to the addition of the test material. Oxygen concentrations were ≥60 % of the saturation value at the selected temperature.
- No. of organisms per vessel: Five daphnids per vessel
- No. of vessels per concentration (replicates): Four replicates of five.
- No. of vessels per control (replicates): Four replicates of five.
- Biomass loading rate: The animals are loaded at one animal/20 mL of culture water.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted (M4). The pH of this solution is 8.0 ± 0.5; total hardness is generally between 272 and 340 mg/L as CaCO3.
- Ca/Mg ratio: The sum of Ca and Mg ions in the solution is 2.5 mmol/L; molar ratio Ca:Mg is approximately 4:1 (Na:K approximately 10:1)
- Conductivity: <10 µS/cm
- Culture medium different from test medium: No
- Intervals of water quality measurement: The pH and dissolved oxygen values of the control and the highest concentration were measured at the beginning and the end of the test. Temperature was measured at the beginning of the test and the maximum and minimum temperatures during the test recorded. Water hardness was checked at the beginning and the end of the test in the control solution.

OTHER TEST CONDITIONS
- Adjustment of pH: No. The pH of all test solutions remained within the range 6.0 ± 0.2 to 9.0 ± 0.2 after preparation and there was therefore no adjustment of pH before incorporation of the animals.
- Photoperiod: 16/8 h light/dark cycle

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
Observations were carried out at 0, 24 and 48 hours in order to determine the number of immobilised daphnids in each test solution. Immobilisation is defined as the inability of a daphnid to swim within 15 seconds after gentle agitation of the test vessel.

VEHICLE CONTROL PERFORMED: Not applicable

RANGE-FINDING STUDY
- Test concentrations: 0.01, 0.1, 1 and 10 mg/L nominal with 20 daphnids per concentration (4 replicates)
- Results used to determine the conditions for the definitive study: Yes. No immobilisation was noted at any of the concentrations tested.

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

Key result

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:

IMMOBILISATION
No difficulty was experienced in discerning the daphnids during the observation periods. No immobilisation was observed throughout the test.
Hence, the highest concentration resulting in no immobilisation at 48 hours was ≥ 100 mg/L and the 48-hour EC50 of the test material was > 100 mg/L.
As no immobilisation was observed at 100 mg/L and the measured concentrations of the test material was within ± 20 % of this nominal value throughout the test, the study was considered complete.

VALIDITY CRITERIA
All validity criteria of the study were respected. The immobilisation in the control was ≤10 % at the end of the test. The dissolved oxygen concentration remained ≥ 60 % of the air saturation value throughout the test. The pH of the control did not vary by more than 1 unit during the test.

Reported statistics and error estimates:

- Determination of the LC50
When for at least two concentrations, immobilisation is > 0 % and < 100 %, the EC50 is calculated according to Probit analysis (i.e. Finney's method, published by E. Weber, combined with Bliss's method). The confidence interval limits are calculated statistically according to Fieller's method.
When at only one concentration, immobilisation is > 0 % and < 100 %, the EC50 is also calculated by Probit analysis. In this case, the highest concentration causing no immobilisation and the lowest concentration producing 100 % immobilisation are used as confidence limits.
If at all concentrations, immobilisation is 0 or 100 %, the EC50 corresponds to the geometric mean of the highest concentration causing no mortality and the lowest concentration producing 100 % immobilisation. In this case, the highest concentration causing no immobilisation and the lowest concentration producing 100 % immobilisation can also be used as confidence limits.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, the 48-hour EC50 of the test material in a static test system was >100 mg/L for Daphnia magna.

Executive summary:

A study was conducted to investigate the potential of the test material to cause acute toxicity to daphnids in accordance with the standardised guidelines OECD 202 and EU Method C.2 under GLP conditions.

Following a range-finding test, a limit test was conducted at 100 mg/L to assess the toxicity of the test material in daphnia magna. Twenty daphnids (in four replicates of five) were exposed to a nominal concentration of 100 mg/L for 48 hours under static conditions while a second group of 20 daphnids (in four replicates of five) was exposed to test dilution water (M4) only ( control solution). Observations were carried out at 0, 24 and 48 hours in order to determine the number of immobilised daphnids in each test solution.

No immobilisation was noted in the control and the limit test solution (100 mg/L nominal). All validity criteria of the study were fulfilled therefore the test was considered valid. As the test material was not found to be toxic at 100 mg/L nominal, chemical analysis was undertaken to measure the concentration of the test material in test solutions and measured concentrations were within ± 20 % of the nominal value (100 mg/L) throughout the test.

Under the conditions of this study, the 48-hour EC50 of the test material in a static test system was >100 mg/L for Daphnia magna. The NOEC was ≥100 mg/L.

Description of key information

Under the conditions of this study, the 48-hour EC50 of the test material in a static test system was >100 mg/L for Daphnia magna.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L

Additional information

A study was conducted to investigate the potential of the test material to cause acute toxicity to daphnids in accordance with the standardised guidelines OECD 202 and EU Method C.2 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Following a range-finding test, a limit test was conducted at 100 mg/L to assess the toxicity of the test material in daphnia magna. Twenty daphnids (in four replicates of five) were exposed to a nominal concentration of 100 mg/L for 48 hours under static conditions while a second group of 20 daphnids (in four replicates of five) was exposed to test dilution water (M4) only ( control solution). Observations were carried out at 0, 24 and 48 hours in order to determine the number of immobilised daphnids in each test solution.

No immobilisation was noted in the control and the limit test solution (100 mg/L nominal). All validity criteria of the study were fulfilled therefore the test was considered valid. As the test material was not found to be toxic at 100 mg/L nominal, chemical analysis was undertaken to measure the concentration of the test material in test solutions and measured concentrations were within ± 20 % of the nominal value (100 mg/L) throughout the test.

Under the conditions of this study, the 48-hour EC50 of the test material in a static test system was >100 mg/L for Daphnia magna. The NOEC was ≥100 mg/L.