Dimethyl (dimethoxyphosphinyl)succinate

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

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)

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

GLP compliance:

yes

Analytical monitoring:

yes

Remarks:

GC-FID

Details on sampling:

sampling schedule: 0 h, 21 h, 48 h
samples for chemical analysis were taken of fresh and aged test solutions

Vehicle:

no

Details on test solutions:

Test concentrations
Following concentrations with a spacing factor of 2.0 were tested: 6.25, 12.5, 25.0, 50.0 and 100 mg test item/L.
The test was performed in four replicates per concentration with five daphnids per replicate under semi-static conditions.

Control
The control consisted of dilution water only. Four replicates with five daphnids per replicate were conducted.

Introduction of the test item
All test item solutions were prepared in Cu-reduced dilution water.
Before test start and at medium renewal the highest test concentration of 100 mg/L was prepared by weighing in an adequate amount of test item and transferring it to Cu-reduced dilution water. This solution was stirred for about 15 – 30 minutes at room temperature. The other test concentrations were prepared by dilution of the highest test concentration with Cu-reduced dilution water using a spacing factor of 2.0.
The test was performed under semi-static test conditions. Test solutions were renewed after 24 hours. The test solutions were freshly prepared before test start and before media renewal.

Test organisms (species):

Daphnia magna

Details on test organisms:

The test organisms were young specimens of Daphnia magna, 4 - 24 hours old at test start. Origin of the daphnids is the German Federal Environment Agency, Institut für Wasser-, Boden- und Lufthygiene. Specimens used in the test were bred in the laboratory of the Fraunhofer IME.

Pre-Treatment:
Adult Daphnia, at least 3 weeks old, were separated from the stock population by sieving. Batches of 30 to 50 animals were held at room temperature in ca. 1.8 L dilution water for one week. During this week the daphnids were fed daily with an algal suspension (Desmodesmus subspicatus) and ArtemioFluid (JBL). Algae growing in the log-phase were centrifuged and the pellet was re-suspended in a few mL of medium. 30 mL of this suspension was given to 1 L Daphnia medium. The water was changed once per week. Newborn Daphnia magna were separated by sieving, the first generation was discarded. Individuals applied in the test were transferred with a bore Pasteur pipette a few hours after sieving to ensure applying only healthy specimens.

Test type:

semi-static

Water media type:

freshwater

Remarks:

Purified drinking water was used as holding- and dilution water.

Limit test:

no

Total exposure duration:

48 h

Test temperature:

20.5 - 20.8 °C (mean temperature 20.6 °C)

pH:

8.1 – 8.5

Dissolved oxygen:

Oxygen saturation between 7.7 mg/L and 8.7 mg/L

Nominal and measured concentrations:

Control, 6.25, 12.5, 25.0, 50.0 and 100 mg test item/L
At test initiation, the measured concentrations were 5.73, 11.64, 24.24, 50.20 and 99.98 mg test item/L (91.7 – 100.4 % of nominal). At media renewal after 24 hours, aged test solutions showed concentrations of 5.40, 11.07, 23.15, 46.18 and 96.54 mg/L (86.4 – 96.5 % of nominal). The aged test concentrations remained stable with 92.0 – 96.9 % of initial concentrations. After 24 hours, freshly prepared test concentrations were 5.79, 11.65, 24.47, 49.08 and 100.54 mg/L (92.7 – 100.5 % of nominal). After 48 hours in aged test solutions, measured concentrations were 5.31, 10.58, 21.77, 45.96 and 94.46 mg/L (84.6 – 94.6 % of nominal). The aged test concentrations again remained stable with 88.9 – 94.0 % of initial concentrations.

Details on test conditions:

Food
According to the OECD guideline 202, the daphnids were not fed during the test.

Environmental conditions
With a mean temperature of 20.6 °C throughout the test the permitted range of 18 – 22 °C (with a variation of less than 1 °C) was maintained. The oxygen saturation was between 7.7 mg/L and 8.7 mg/L. The pH values throughout the test were within a range of 8.1 – 8.5 at all treatment levels, which is in accordance with the guideline. The light intensity was measured using an illuminance meter (MINOLTA) with a photometric sensor in Lux. With 816 – 843 lx (corresponding to 10.9 – 11.2 µE/(m² * s)) the light intensity was below the maximum threshold value of about 1000 - 1500 lx (15 - 20 µE/(m² * s)) as permitted by OECD guideline 211. Thus, all water quality criteria mentioned in the guideline were met.

The test was performed in four replicates per concentration with five daphnids per replicate under semi-static conditions with a medium renewal after 24 h.

The numbers of immobile animals were visually determined daily and dead specimens were removed. Immobility was determined according to the OECD guideline 202. Specimens which were not able to swim within 15 seconds after gentle agitation of the test vessel were considered to be immobilized (even if they were still moving their antennae).

Reference substance (positive control):

no

Remarks:

According to guideline no reference item is required.However, the sensitivity of the test clone is checked twice a year in non-GLP tests by using K2Cr2O7 as reference substance. The latest 24h-EC50 was 1.435 mg/L (95% confidence limits: 1.233–1.745 mg/L).

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Since the measured concentrations were between 80 and 120% of nominal test concentrations in fresh and aged samples, it was decided to perform the evaluation of the concentration-effect-relationships and the calculations of effect concentrations based on the nominal test concentrations.

Physical/Pathological symptoms and changes in behaviour
Neither significant signs of disease nor stress like discoloration or abnormal behavior were observed in any replicate up to and including the highest test item concentration of 100 mg test item/L. All surviving specimens, up to and including the highest test item concentration gave the impression of healthy condition.

Reported statistics and error estimates:

Statistical calculations
For immobilization, the NOEC and LOEC were determined. EC10, EC20, and EC50 values together with 95% confidence intervals (where possible) were calculated by Probit-analysis assuming log-normal distribution of the values. All statistical calculations were performed using the computer programme ToxRat®.

Validity criteria fulfilled:

yes

Remarks:

mortality observed in the controls over the test period is ≤ 10 %, dissolved oxygen concentration at the end of the aging period (48 h) was > 3 mg/L in control and test vessels

Conclusions:

No acute toxicity of dimethyl (dimethoxyphosphinyl)succinate towards Daphnia magna under the chosen test conditions was determined up to 100 mg/L.

Executive summary:

The study was performed to determine the influence of dimethyl (dimethoxyphosphinyl)succinate on immobilization of daphnids of the species Daphnia magna. For this, the daphnids were placed in water containing the substance in nominal concentrations of 6.25, 12.5, 25.0, 50.0 and 100 mg/L. The test was conducted under semi-static conditions for 48 h. Effects on immobilization were determined after 24 and 48 hours. Samples for chemical analysis were taken of fresh and aged test solutions.

The concentrations of the test item in the test media were determined by chemical analysis in the aqueous phase of all treatment levels. The test item was measured by GC-FID at the start and at the end of the test (LOQ = 2.172 mg/L).

At test initiation, the measured concentrations of the freshly prepared test solutions of the test item were 5.73, 11.64, 24.2, 50.2 and 100.0 mg /L (92 – 100 % of nominal). After 24 hours, in aged test solutions, test item concentrations remained constant at 5.4, 11.1, 23.1, 46.2 and 96.5 mg/L (86 - 97 % of nominal). Freshly prepared test media at 24 hours showed concentrations of 5.8, 11.7, 24.5, 49.1 and 11.5 mg/L (93 -101 % of nominal). At test end concentrations of aged test media were 5.3, 10.6, 21.8, 46.0 and 94.6 mg/L (85 – 95 % of nominal).

Due to recovery rates between 80 and 120 % of nominal throughout the test, nominal test concentrations of 6.25, 12.5, 25.0, 50.0 and 100 mg /L were applied for the effect assessment.

At the end of the test, no significantly increased immobility of daphnids was observed up to the highest test concentration of 100 mg/L when compared to the control daphnids. Dimethyl (dimethoxyphosphinyl)succinate is not acutely toxic to Daphnia magna under the chosen test conditions.

Description of key information

The study was performed to determine the influence of dimethyl (dimethoxyphosphinyl)succinate on immobilization of daphnids of the species Daphnia magna. For this, the daphnids were placed in water containing the substance in nominal concentrations of 6.25, 12.5, 25.0, 50.0 and 100 mg/L. The test was conducted under semi-static conditions for 48 h. Effects on immobilization were determined after 24 and 48 hours. Samples for chemical analysis were taken of fresh and aged test solutions. The test item was measured by GC-FID at the start and at the end of the test (LOQ = 2.172 mg/L).

Due to recovery rates between 80 and 120 % of nominal throughout the test, nominal test concentrations were applied for the effect assessment.

At the end of the test, no significantly increased immobility of daphnids was observed up to the highest test concentration of 100 mg/L when compared to the control daphnids. Thus, dimethyl (dimethoxyphosphinyl)succinate is not acutely toxic to Daphnia magna under the chosen test conditions.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L

Additional information

Should be read as: LC 50 >= 100 mg/L