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

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 June 2005 to 17 June 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OECD Series on testing and assessment, Guidance document on aquatic toxicity testing of difficult substances and mixtures, Number 23

Version / remarks:

2000

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: Samples of 5 mL were taken from the limit test solution (100 mg/L nominal) at the beginning of the test, before and after each solution change and at the end of the test. They were kept at -20 °C until analysis. An aliquot of each 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 the test water.
- Quantity of test material: 1000 mg
- Volume of test water: 10 000 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 test water to provide a geometric series of concentrations: 0, 0.01, 0.1, 1, 10 and 100 mg/L.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Length at study initiation: 40 to 59 mm long (based on a measurement of a sample of 34 fish used in the study)
- Weight at study initiation: The mean weight of the fish, based on a sample of ten animals removed at random from the acclimation tank just before the test, was 0.750 g.
- Method of breeding: Animals were cultured at the laboratory from eggs supplied by an external company

ACCLIMATION
- Acclimation period: At least 12 days
- Acclimation conditions (same as test or not): Yes. During culture the fish are maintained under a flow-through system in water of the same quality and temperature as that to be used in the test. Half of the water passes directly into a holding tank attached to the flow-through system while the remaining half passes through a deioniser producing ultra-pure water which is then fed into the holding tank. This results in a 1:1 dilution of potable dechlorinated:deionised water giving a supply of the desirable hardness.During culture temperature and water hardness are checked daily while dissolved oxygen concentration and pH are checked at least weekly. Oxygen concentration remains above 80 % of the saturation value at the selected temperature.
- Type and amount of food during acclimation: Trout chow
- Feeding frequency during acclimation: Twice daily
- Health during acclimation (any mortality observed): Not specified

FEEDING DURING TEST: No
Feeding ceased 24 h before the start of the test. Animals were not fed during the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

146 to 151 mg CaCO3/L

Test temperature:

15.9 to 16.9 °C

pH:

7.05 to 7.95

Dissolved oxygen:

5.2 to 9.3 mg/L (greater than or equal to 60 % of the air saturation value)

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 fish were filled directly from the test solution containers immediately after preparation.
- Aeration: Forced aeration was not used during the test. Dilution water was aerated prior to addition of the test material.
- Renewal rate of test solution (frequency/flow rate): Solutions were changed every 24 hours
- No. of organisms per vessel: 7 fish per vessel
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates):1
- Biomass loading rate: The animals were loaded at a density of less than 1 g of fish per litre (0.750 g/L)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Filtered and dechlorinated potable water which is then softened by a Permo® water softening system. The pH of the solution is between 6.0 and 8.5 and the total hardness is 150 ± 20 mg/L as CaCO3. The test solution was a clear and colourless solution at all test material concentrations.
- Ca/Mg ratio: Ca 41.5 mg/L, Mg 10.2 mg/L
- Culture medium different from test medium: No
- Intervals of water quality measurement: The pH, temperature and dissolved oxygen values were measured in the limit test solutions (highest concentration and control) at T0 and then every 24 hours thereafter in the stale solution. Measurements of total hardness in the control solution were made daily.

OTHER TEST CONDITIONS
- Adjustment of pH: There was no adjustment of pH before incorporation of the animals.
- Photoperiod: A light/dark cycle of 16/8 hours

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
Animals were inspected for mortality and visible abnormalities at each observation time (0, 2, 4, 24, 48, 72 and 96 hours). Fish are considered dead when they fail to respond to tactile stimulation of the caudal peduncle and show no signs of respiration.
Sub-lethal effects observations included animals staying at the surface of the solution, minor and severe loss of equilibrium, hyperactive swimming behaviour, spasmodic swimming, animals staying at the bottom of the aquarium, colour change, abnormal respiratory rate and immobilisation before death.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: None, limit test
- Range finding study: Yes
- Test concentrations: 0.01, 0.1, 1 and 10 mg/L nominal with 5 fish per concentration
- Results used to determine the conditions for the definitive study: Yes. No mortality or sub-lethal effects were noted at any of the concentrations tested.

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: mortality and sub-lethal effects

Details on results:

No mortality or sub-lethal effects were noted in the control and the limit test solution (100 mg/L nominal).
Hence, the no observed sub-lethal effect concentration at 96 hours and the highest concentration resulting in no mortality at 96 hours were ≥100 mg/L, while the 96-hour LC50 of the test material was > 100 mg/L.
As no mortality was observed at 100 mg/L and the measured concentrations of the test material were 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 mortality in the control group 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, mortality is > 0 % and < 100 %, the LC50 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, mortality is > 0 % and < 100 %, the LC50 is also calculated by Probit analysis. In this case, the highest concentration causing no mortality and the lowest concentration producing 100 % mortality are used as confidence limits.
If at all concentrations, mortality is 0 or 100 %, the LC50 corresponds to the geometric mean of the highest concentration causing no mortality and the lowest concentration producing 100 % mortality. In this case, the highest concentration causing no mortality and the lowest concentration producing 100 % mortality can also be used as confidence limits.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, the 96-hour LC50 of the test material in a semi-static test system was >100 mg/L for Oncorhynchus mykiss.

Executive summary:

A study was conducted to investigate the potential of the test material to cause acute toxicity to fish in accordance with the standardised guidelines OECD 203, EU Method C.1 and the OECD Series on testing and assessment Guidance document on aquatic toxicity testing of difficult substances and mixtures Number 23 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 rainbow trout. Seven fish were exposed to a nominal concentration of 100 mg/L for 96 hours under semi-static conditions while a second group of seven fish was exposed to test dilution water only (control solution). Test solutions were renewed every 24 hours. Mortality and sub-lethal effects at each concentration were recorded at 0, 2, 4, 24, 48, 72 and 96 hours.

No mortality or sub-lethal effects were 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 96-hour LC50 of the test material in a semi-static test system was > 100 mg/L for Oncorhynchus mykiss. The NOEC was ≥100 mg/L.

Description of key information

Under the conditions of this study, the 96-hour LC50 of the test material in a semi-static test system was > 100 mg/L for Oncorhynchus mykiss.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

100 mg/L

Additional information

A study was conducted to investigate the potential of the test material to cause acute toxicity to fish in accordance with the standardised guidelines OECD 203, EU Method C.1 and the OECD Series on testing and assessment Guidance document on aquatic toxicity testing of difficult substances and mixtures Number 23 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 rainbow trout. Seven fish were exposed to a nominal concentration of 100 mg/L for 96 hours under semi-static conditions while a second group of seven fish was exposed to test dilution water only (control solution). Test solutions were renewed every 24 hours. Mortality and sub-lethal effects at each concentration were recorded at 0, 2, 4, 24, 48, 72 and 96 hours.

No mortality or sub-lethal effects were 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 96-hour LC50 of the test material in a semi-static test system was > 100 mg/L for Oncorhynchus mykiss. The NOEC was ≥100 mg/L.