Ethoprophos

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 1999-05-19 to 1999-07-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

Part I, 1984

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

E.E.C. DIRECTIVE 92/69 (1992)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPP 72-2 (Aquatic Invertebrate Acute Toxicity Test)

Version / remarks:

1985

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Ethoprophos

EC Number:

236-152-1

EC Name:

Ethoprophos

Cas Number:

13194-48-4

Molecular formula:

C8H19O2PS2

IUPAC Name:

ethyl bis(propylsulfanyl)phosphinate

Test material form:

liquid

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Treatment replicate vessels were filled from bulk preparations. Samples of test solutions were taken for analysis from each bulk preparation at the initiation of the test and from pooled replicates of each concentration level at the termination of the test.
- All samples were collected in triplicate: one sample was analysed within 24 hours after preparation, the two others were appropriately stored in case required for purposes of verification.
- Each sample was collected from the approximate midpoint of the vessel with a pipette.

Test solutions

Vehicle:

yes

Details on test solutions:

- A stock solution of the highest test substance concentration was prepared by dissolution of 10 mg of test substance in 2 mL of the solvent dimethylformamide (DMF).
- Stock solutions of the four lower test substance concentrations were prepared by serial dilutions of the first stock solution submitted to magnetic agitation until used.
- Test solutions were prepared by dilution of the stock solutions with known volumes of dilution water. Volumes of 500 mL (bulk preparation) for each fixed concentration were prepared. Then each bulk preparation was distributed between the test vessels to provide final test volumes of 200 mL.
- The final concentration of solvent in the highest test substance concentration was 0.1 mL/L. An appropriate volume of solvent was added to the stock solutions of each of the four lower test substance concentrations so that the final concentration of solvent in each test solution was 0.1 mL/L.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Strain/clone: Straus
- Age at study initiation: less than 24 hours old
- Source: laboratory cultures maintained in the Aquatic Ecotoxicology facilities, Rhone-Poulenc Agro, Sophia Antipolis, France, initiated with daphnids of clone 5 originating from IRCHA as identified by INERIS Laboratory - BP1 - 91710 Vert-le-petit, France.
- Feeding during test: no

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

Hardness:

171 mg/L as CaCO3

Test temperature:

20 ± 2 °C

pH:

7.74 - 7.82

Dissolved oxygen:

8.0 - 8.6 mg/L

Conductivity:

519 µS/cm

Nominal and measured concentrations:

Nominal concentrations: 0.05, 0.09, 0.15, 0.28 and 0.50 mg/L (spacing factor of 1.8)
Mean measured concentrations: 0.06, 0.09, 0.15, 0.27 and 0.49 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: beaker
- Type: covered
- Material, size, headspace, fill volume: glass, 250 mL
- Volume of solution: 200 mL
- Aeration: no
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- No. of vessels per vehicle control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted water 80% DSW + 20% LC-oligo
- Total organic carbon: 0.7 mg/L
- Particulate matter: 1.0 mg/L
- Metals: <0.05 mg/L
- Pesticides: <0.02 µg/L
- Chlorine: 57.4 mg/L
- Ca/mg ratio: 2.967
- Conductivity: 540 ± 40 micro Siemens per centimetre (µS/cm)
- pH: 7.8 ± 0.2
- Culture medium different from test medium: no
- Intervals of water quality measurement: 6 months

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 hours light : 8 hours darkness
- Light intensity: 528 to 539 lux

EFFECT PARAMETERS MEASURED: Immobilisation and the appearance of any behavioural alterations, 24 and 48 hours

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: 0.02, 0.05, 0.10, 0.23 and 0.50 mg/L
- Results used to determine the conditions for the definitive study: After 48 hours of exposure, 5, 5, 5, 55 and 100 % immobilisation were recorded at the test concentrations of 0.02, 0.05, 0.10, 0.23 and 0.50 mg/L, respectively. 5 % immobilisation was also observed among the daphnids in the solvent control group.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.2 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Effect concentrations 2

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.15 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

During the test period, no immobilisation was observed in the control groups (dilution water and solvent control groups) and no daphnid was found entrapped at the surface of the control solution.
Following 24 and 48 hours of exposure, no significant immobilisation was observed among the daphnids exposed to the mean measured concentrations of 0.06,0.09 and 0.15 mg/L.
100 % immobilization were recorded at the two highest concentrations of 0.27 and 0.49 mg/L at test termination.
No sub-lethal effects were observed among the exposed daphnids.

Any other information on results incl. tables

Analytical results

The test solutions were sampled and analyzed at the beginning and the end of the test. The test substance was soluble in the dilution water at all concentrations tested.
Analytical verification at test initiation showed the measured concentrations were close to the nominal values (96 - 140 % recovery).
At test termination, the measured concentrations were close to the initial measured values (71 - 100 %) indicating stability of ethoprophos in the test solutions.
Analytical verification of the lowest test substance concentrations of 0.05 mg/L presented some variability (140 % recovery at test initiation and 71 % recovery at test termination) which can be explained by the fact that this concentration was very close to the quantification limit of the analytical method.
Analytical measurements in the control groups (dilution water and solvent control group) were below the quantification limit of the method (LOQ = 0.02 mg/L).

 

TABLE 1 - MEASURED CONCENTRATIONS OF ETHOPROPHOS IN TEST SOLUTIONS DURING 48-HOUR EXPOSURE OF DAPHNIA MAGNA UNDER STATIC CONDITIONS

Nominal concentrations (mg/L)	Measured Concentrations (mg/L)			Recoveries
	0-hour B	48-hour P	Mean (a)	T0 %	T48/T0 %
0 (Control)	< LOQ	< LOQ	-	-	-
0 (Solvent)	< LOQ	< LOQ	-	-	-
0.05	0.07	0.05	0.06	140	71
0.09	0.09	0.09	0.09	100	100
0.15	0.15	0.15	0.15	100	100
0.28	0.27	0.27	0.27	96	100
0.50	0.49	0.48	0.49	98	98

LOQ = Quantification limit ( 0.02 mg/L)

B = Bulk preparation

P = Pooled test solution

(a) = Mean measured values for reporting.

T0%: Initial measured concentration versus nominal concentration

T48/T0%: Final measured concentration versus initial measured concentrations

 

Biological results

No immobilization or sublethal toxicity was observed neither in the control groups (dilution water and solvent control groups) nor in the groups exposed to the mean measured concentrations of 0.06, 0.09 and 0.15 mg/L during the test period. 100 % mortality were recorded at the two highest mean measured concentrations of 0.27 and 0.49 mg/L.

The 24-hour EC50 was calculated to be 0.38 mg/L (95 % confidence interval: 0.27 - 0.49)
The 48-hour EC50 of the test item to Daphnia magna under static conditions was calculated to be 0.20 mg/L (95 % confidence interval: 0.15 - 0.27).
The No Observed Effect Concentration (NOEC) of the test item through 48 hours is reported to be 0.15 mg/L.

 

TABLE 2 - CUMULATIVE NUMBER OF IMMOBILIZED DAPHNIDS (DAPHNIA MAGNA) DURING THE 48-HOUR STATIC EXPOSURE

Mean measured concentrations (mg/L)	Cumulative number
	24-hour			48-hour
	In each container		Mean %	In each container		Mean %
	R1	R2		R1	R2
Control (<LOQ)	0	0	0	0	0	0
Solvent (<LOQ)	0	0	0	0	0	0
0.06	0	0	0	0	0	0
0.09	0	0	0	0	0	0
0.15	0	0	0	0	0	0
0.27	0	0	0	10	10	100
0.49	10	9	95	10	10	100

Total number of exposed daphnids per concentration level: 20.

R1 = Replicate 1

R2 = Replicate 2

LOQ = Quantification Limit (0.02 mg/L)

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

Under static conditions and based on the mean measured concentrations, the acute toxicity of the test item to daphnids (Daphnia magna) is defined as follows: 48-h EC50 = 0.20 mg/L (95 % confidence interval: 0.15 - 0.27 mg/L) and 48-h NOEC = 0.15 mg/L.

Executive summary:

The purpose of this study was to estimate the acute toxicity of the test item to Daphnia magna under static conditions according to OECD 202 (1984). The test substance was in the form of pale yellow liquid and is intended for use as an insecticide. A total of 140 organisms (10 per replicate, 2 replicates per concentration) were exposed to 5 concentrations of the test item, a solvent control (dimethylformamide, DMF) and a dilution water control over a 48-hour period. The test was conducted using the following nominal concentrations: 0.05, 0.09, 0.15, 0.28 and 0.50 mg/L. The test solutions were sampled and analysed at the beginning and the end of the test. The test substance was soluble in the dilution water at all concentrations tested. Analytical verification at test initiation showed the measured concentrations were close to the nominal values (96 - 140 % recovery). At test termination, the measured concentrations were close to the initial measured values (71 - 100 %).
The results of this test are reported on the basis of the following mean measured concentrations of the test item expressed as milligrams per liter (mg/L): 0.06, 0.09, 0.15, 0.27 and 0.49 mg/L.
No immobilization or sub-lethal toxicity was observed neither in the control groups (dilution water and solvent control groups) nor in the groups exposed to the mean measured concentrations of 0.06, 0.09 and 0.15 mg/L during the test period. 100 % mortality were recorded at the two highest mean measured concentrations of 0.27 and 0.49 mg/L.
The 48-hour EC50 of the test item to Daphnia magna under static conditions was calculated to be 0.20 mg/L.
The No Observed Effect Concentration (NOEC) of the test item through 48 hours is reported to be 0.15 mg/L.
In conclusion, under the static conditions of the test and based on the mean measured concentrations, the acute toxicity of the test item to daphnids (Daphnia magna) is defined as follows: 48-h EC50 = 0.20 mg/L (95 % confidence interval: 0.15 - 0.27 mg/L) and 48-h NOEC = 0.15 mg/L.