1-[(4-chlorophenyl)methyl]-1-cyclopentyl-3-phenylurea

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:

2000-08-15 to 2001-03-23

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:

4 April, 1984

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

The test material is a colourless crystal.

Analytical monitoring:

yes

Details on sampling:

Test water samples were collected from all test levels including controls at day 0 and 2 to measure actual exposure concentrations. All samples were analyzed by HPLC.

Vehicle:

yes

Remarks:

Acetone (0.1 ml/L)

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Controls: a dilution water and a solvent control (0.1 mL acetone/L)
- Chemical name of vehicle: Acetone
- Other relevant information: For the test, any test concentration was established as a uniform batch. To prepare the nominal test concentrations of 0.18 mg a.s./L, 18.2 mg of Pencycuron were suspended in 10 ml of acetone (= stock solution I). The further stock solutions II to VIII (for preparing the concentrations of 0.32, 0.56, 1.0, 1.8, 3.2, 5.6 and 10.0 mg a.s./L) were established by suspending 32.3, 56.6, 101, 182, 323, 566 or 1010 mg, respectively in 10 mL of acetone. Every stock solution was sonicated for 3 minutes. From these stock solutions 100 µL were taken each and added up to 1L of test water. Each concentration was stirred on a magnetic stirrer for 3 minutes. At the start of the study, ten < 24 hours old first instars were carefully transferred into each test beaker using a pipette. All organisms were transferred into the test chambers within fifteen minutes after preparation of the test solutions. The animals were impartially distributed to the test beakers. A random number sequence was used to assign the test animals to the test beakers.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea (Daphnia magna)
- Age at study initiation (mean and range, SD): < 24h
- Age of parental stock: 21 to 28 days old
- Feeding: The adults were fed with an aqueous suspension of 5 mL single cell green algae Scenedesmus subspicatus three times per week per container. The animals occasionally receive some commercial ornamental fish food (aqueous suspension) as a supplement to the algae diet (2 ml per container).

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES, INCLUDING CULTURING CONDITIONS
The first instars used in the test were obtained by repeated careful screening of adults using plastic screens with 0.6 and 0.2 mm mesh. The parent daphnids were of the same age (±12 hours). They were between 21 and 28 days old. The organisms used during the exposure were < 24 hours old and were from the fourth brood or later. No males, ephippia or discoloured animals were present in the cultures. The cultures showed no delay in first brood.

Test type:

static

Water media type:

other: M7-medium

Limit test:

no

Total exposure duration:

48 h

Remarks on exposure duration:

Exposed oer 48 hours with observations made daily for immobility and other adverse effects.

Hardness:

196 mg/L

Test temperature:

20.0 - 20.3°C

pH:

8.0 - 8.1

Dissolved oxygen:

Start of the test: 8.6 - 9.2 mg/L; end of the test: 7.8 - 9.0 mg/L

Salinity:

50 mg/L CaCO3

Conductivity:

596 µS/cm

Nominal and measured concentrations:

Nominal concentrations of 0.18, 0.32, 0.56, 1.0, 1.8, 3.2, 5.6 and 10.0 mg a.s./L
Measured concentrations: 0.178, 0.299, 0.518, 0.867, 1.03, 0.98, 0.933 and 2.08 mg a.s./L

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL glass beakers
- Type: closed
- Volume of solution: Each test vessel contained 50 ml of the test solution.
- Aeration: the test solutions were not aerated during the test.
- No. of organisms per vessel: ten animals per vessel.
- No. of vessels per concentration (replicates): three replicates per concentration.
- No. of vessels per control (replicates): three replicates per concentration.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The medium (M7-medium) is prepared using deionized water by adding mineral salts and vitamins (reagent grade chemicals).
- Ca/mg ratio: 7:1
- Conductivity: 580 µS/cm

OTHER TEST CONDITIONS
- Photoperiod: 8h dark/16h light.
- Light intensity: about 1000 lux.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.3 mg/L

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: based on test substance aqueous solubility.

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.3 mg/L

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: based on test substance aqueous solubility.

Details on results:

The mean measured concentrations of the test substance varied between 17% and 99% of the nominal values. The percentage of recovered test substance decreased with increasing test concentrations. At 1.8, 3.2, 5.6 and 10 mg a.s./L, 57%, 30%, 17% and 21% of nominal was measured, respectively. At the lower concentrations all measured values were above 80% of nominal. This indicates that the higher concentrations are above the water solubility of the test item (0.3 mg/L at 20°C). This was confirmed by the observation of precipitations at concentrations above 1.0 mg a.s./L.

The lowest measured dissolved oxygen concentration was 7.8 mg/L; pH values varied between 8.0 and 8.1. In the control and solvent control groups, the number of immobilised animals was =10%. At 3.2 mg a.s./L and the higher concentrations tested, adverse effects with respect to condition were observed after 24 and 48h of exposure. This report states that the 24h and 48h-EC50 are >1.0 mg a.s./L and that the 24h and 48h-NOEC are 1.0 and 0.56 mg a.s./L, respectively.

The recovery of the active substance was <80% of the nominal concentration for test concentrations above 1.0 mg a.s./L. This is related to the water solubility of the active ingredient (0.3 mg a.s./L at 20°C) and confirmed by precipitation of the test substance at concentrations exceeding 1.0 mg a.s./L. The reported values for the EC50 and NOEC were based on nominal concentrations. It must be assumed that the amount of test substance dosed above the aqueous solubility of the active substance is not bioavailable and does not contribute to the exposure of daphnids to the test substance. As within the water solubility level no adverse effects to the daphnids were observed, it can be concluded that under the circumstances of the test, the test substance is not toxic within its aqueous solubility (0.3 mg a.s./L)

It is therfore concluded that the 48h-EC50 is >0.3 mg a.s./L and the 48h-NOEC values for mobility and condition are both =0.3 mg a.s./L.

Results with reference substance (positive control):

The EC50 of the reference substance is located within the required range. Thus, the study conditions and breeding quality meet the criteria.

See "Attachments" in "Overall remarks, attachments" for the tables.

Validity criteria fulfilled:

yes

Conclusions:

The recovery of the active substance was <80% of the nominal concentration for test concentrations above 1.0 mg a.s./L. This is related to the water solubility of the active ingredient (0.3 mg a.s./L at 20°C) and confirmed by precipitation of the test substance at concentrations exceeding 1.0 mg a.s./L. The reported values for the EC50 (>1.0 mg a.s./L) and NOEC (0.56 mg a.s./L) were based on nominal concentrations. It must be assumed that the amount of test substance dosed above the aqueous solubility of the active substance is not bioavailable and does not contribute to the exposure of daphnids to the test substance. As within the water solubility level no adverse effects to the daphnids were observed, it can be concluded that under the circumstances of the test, the test substance is not toxic within its aqueous solubility (0.3 mg a.s./L). It is therfore concluded that the 48h-EC50 is >0.3 mg a.s./L and the 48h-NOEC values for mobility and condition are both =0.3 mg a.s./L.

Executive summary:

The acute toxicity of Pencycuron Technical to Daphnia magna was determined under static conditions.  Daphnids were exposed to nominal concentrations of 0.18, 0.32, 0.56, 1.0, 1.8, 3.2, 5.6 and 10.0 mg a.s./L, alongside a dilution water control and a solvent control.  The test substance is not toxic to Daphnia magna at a level of its aqueous solubility. It is concluded that the 48h-EC₅₀ is >0.3 mg a.s./L and the 48h-NOEC values for mobility is ≥0.3 mg a.s./L.

Description of key information

An acute 48-h toxicity test was conducted to determine the effect of Pencycuron on the mobility of Daphnia magna. Based on nominal concentrations of Pencycuron the 48-h EC₅₀ for was determined to be >0.3 mg/L.

 

Test species	Result	Assessment	Reference
Daphnia magna	48-h EC50 >0.3 mg a.s./L (nominal)	Key study	Hendel (2001)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

> 0.3 mg/L