1,3-dibutyl-2-thiourea

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:

2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

None.

Analytical monitoring:

yes

Details on sampling:

All treatments were analytically monitored at the beginning and the end of the test.

Vehicle:

no

Details on test solutions:

Tests solutions were prepared from dilutions of a stock solution. A known volume of test item (500.2 mg) was poured into a volumetric flask, the volume was then made up to 500 mL with test medium. The solution was kept under high speed stirring at ambient temperature during approximately 2 hours with a magnetic stir bar. The pH of the test solutions were not adjusted. Test solutions were not renewed throughout the 96h test period (static test).

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

The test organisms were Danio rerio (Teleostei, Cyprinidae), obtained from a recognizsed supplier: La Grande Rivière France (69490 Saint-Forgeux). All fish were in good health and free from any apparent malformation. Mortality of the batch was less than 5% in the week preceding the start of the study. No disease treatments were administered throughout holding and testing.
Holding was maintained within the laboratory at a temperature of 21-25°C in glass tanks. A light cycle of 12 h light and 12 h dark was applied, illumination being provided by fluorescent tubes (intensity between 400 and 800 lux at the surface of the tanks). Tanks were aerated to ensure that the dissolved oxygen concentration is at least 60% of air saturation value in holding tanks and in test tanks. During holding, fish were fed twice per day with ground flake food TetraMin®.

The fish were not fed for a period of 24h prior to test commencement and throughout the duration of the test

Fish were added to the test tanks within 30 min after completion of preparation of the test solutions. All test fish were weighed prior to the test and a representative number of test fish batch (10 at random) was measured after the test to assess compliance with guideline criteria (mean = 3 cm; min = 2.5 cm ; max = 3.5 cm).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Remarks on exposure duration:

Standard exposure duration

Post exposure observation period:

None.

Hardness:

240 mg CaCO3/L.

Test temperature:

22.4°C - 23.8°C (min-max)

pH:

7.2 - 8.1 (min-max)

Dissolved oxygen:

60.3 - 99.1 % of saturation (min - max)

Salinity:

None.

Conductivity:

Not measured.

Nominal and measured concentrations:

Nominal: 0 ; 6.25 ; 12.5 ; 25 ; 50 ; 100 mg/L
Measured at 0 h: 6 ; 12 ; 27.7 ; 48.3 ; 93.6 mg/L
Measured at 96 h: 6 ; 12 ; 27.3 ; 48 ; Not analysed due to 100% fish mortality within 48 hours in this treatment.

Chemical analysis of test samples indicated that concentrations of the test item were maintained over the 96h test period (i.e. deviation <20%). As a consequence, the stability of the substance was confirmed over the test period; nominal concentrations were thus used to determine LC50.

Details on test conditions:

Test tanks (filled with 2.5 L of test solution) containing fish were incubated with a photoperiod of 12 hours of darkness per 24 h, at a temperature ranging from 21°C to 25°C but remaining constant within ± 2°C during the test. All test tanks were made of clear glass and covered by plates with ventilation holes to minimise evaporation and avoid the entry of dust into the solutions. One tank was prepared at each test concentration and the control group; each tank contained 7 fish. Test solutions were prepared using the synthetic medium; chemical reagents used for the preparation of the dilution water was of “analytical grade”. The control treatment was maintained under the same conditions, with no test item.
Fish were observed at least after 24h, 48h, 72h and 96h (end of the exposure period). Fish were considered dead if touching the caudal peduncle produceds no reaction and no breathing movements are were visible; their number per concentration at each time interval was recorded. Dead fish were removed as soon as observed. Any visible abnormalities abnormality (eg loss of equilibrium, changes in swimming behaviour, respiratory function, pigmentation etc) was also recorded. All surviving fish were sacrificed at the end of the test.
pH and dissolved oxygen concentration were measured for in all tanks at the beginning of the definitive test and thereafter at 24h intervals. The total hardness of a sample of the medium used to prepare the test solutions was measured and expressed as mg CaCO3/L. The temperature was continuously recorded in one tank.

Reference substance (positive control):

yes

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

17.8 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality (fish)

Details on results:

- Behavioural abnormalities: None
- Observations on body length and weight: from 300 to 357 mg mean individual weight per replicate.
- Mortality of control: 0 fish
- Other adverse effects control: None
- Abnormal responses: None
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: None
- Effect concentrations exceeding solubility of substance in test medium: None

Results with reference substance (positive control):

Potassium dichromate : 24h-LC50 fish = 186 mg/L

Reported statistics and error estimates:

Raw data were treated according to the recommendations of the guideline using the software Minitab® 16.1.1 (Probit analysis). For the definitive test, as there was evidence that the concentration of the substance being tested were satisfactorily maintained within ± 20% of the nominal concentration throughout the test, analysis of the results was based on nominal concentrations.

Sublethal observations / clinical signs:

Test solution (mg/L)	Cumulative dead fish					Mortality at the end of the period
	T0	T24h	T48h	T72h	T96h
Control	0	0	0	0	0	0.0%
6.25	0	0	0	0	0	0.0%
12.50	0	0	0	0	0	0.0%
25.00	0	0	0	7	7	100.0%
50.00	0	1	1	7	7	100.0%
100.00	7	7	7	7	7	100.0%

Validity criteria fulfilled:

yes

Conclusions:

This study was designed to determine the effects of 1,3 -dibutylthiourea to Danio rerio over a 96h period with static conditions, according to the OECD 203 Guideline. LC50 was 17.8 mg/L.

Executive summary:

This study was designed to determine the effects of 1,3 -dibutylthiourea to Danio rerio over a 96h period with static conditions, according to the OECD 203 Guideline. Fish were exposed to a series of dilutions of a stock solution in dilution water (0 ; 6.25 ; 12.5 ; 25 ; 50 and 100 mg/L). The stability of the substance was confirmed over the 96h test period (i.e. deviation <20% between T0 and 96h measurements). Nominal concentrations were thus used to determine 96h-LC50 (all results are mg/L). LC50 was 17.8 mg/L.

The definitive test succeeded to meet the validity criterion detailed as follows:

 - The mortality in the control did not exceed 10% at the end of the test.

- The dissolved oxygen in the test tanks remained above 60% of the air saturation value at the end of the test.

- The pH did not vary by more than 1 unit.

Description of key information

One OECD 203 study is available for acute toxicity of 1,3 -dibutylthiourea to fish. LC50 was 17.8 mg/L

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

17.8 mg/L