Bis[O,O-bis(2-ethylhexyl) dithiophosphorato-S,S']dioxodi-μ-thioxodimolybdenum

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)

Version / remarks:

April 2004

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Single Samples for analysis were taken from all test concentrations and the control.
Frequency: at t=0 h and t=48 h
Volume: 5.0 mL from the approximate centre of the test vessels. At the end of the exposure period, the replicates were pooled at each concentration before sampling.
Storage: Not applicable, samples were analysed on the day of sampling

Vehicle:

no

Details on test solutions:

The test item was not completely soluble at the loading rate initially prepared. Thus, preparation of test solutions started with a loading rate of 100 mg/L applying a three-day period of magnetic stirring to reach the maximum dissolution of the test item in medium. The resulting aqueous mixture was allowed to settle for 1 hour and thereafter the Saturated Solution (SS) was collected by means of siphoning. The SS was used as the highest test concentration. Lower test concentrations were prepared by subsequent dilutions of the SS in test medium. All test solutions were clear and colorless at the end of the preparation procedure. No correction was made for the purity/composition of the test item.
The method of preparation of the test medium was based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2000.
- Controls: Test medium without test item or other additives

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flee
- Strain/clone: Straus, 1820
- Age at study initiation (mean and range, SD): less than 24 hours
- Method of breeding: Approximately 250 newborn daphnids, i.e. less than 3 days old, were placed into 5 litres of Elendt M7 medium in an all-glass culture vessel. The maximum age of the cultures was 4 weeks. After 7 days of cultivation, half of the medium was renewed twice a week. The temperature of medium was 18-22°C.
- Source: In-house laboratory culture with a known history
- Age of parental stock (mean and range, SD): 2nd to 5th brood
- Feeding during test: none

ACCLIMATION
- Acclimation period: none; breeding and test conditions were comparable.
- Health during acclimation/breeding (any mortality observed): no signs of stress such as mortality >20%, presence of males, ephippia or discoloured animals; no delay in the production of the first brood.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

1.8 mM (180 mg CaCO3/L)

Test temperature:

20 °C

pH:

7.9 - 8.2

Dissolved oxygen:

8.6 - 9.0 mg O2/L

Nominal and measured concentrations:

nominal test concentrations: 100, 56, 32, 18, and 10% of a supersaturated solution (SS) prepared at 100 mg/L.
measured test concentrations:
at test start: 0.065, 0.047, 0.029, 0.015, and 0.0088 mg/L.
at test end: 0.022, 0.013, 0.0062, 0.0022, and <0.001 mg/L.
average exposure concentrations (the geometric mean): 0.038, 0.024, 0.013, 0.0058, and 0.0021 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: 60 mL, all-glass vessels, containing 50 mL of test medium
- Aeration: none
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 10 mL/animal

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Adjusted ISO medium, formulated using RO-water (tap-water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands); Composition: CaCl2.2H2O: 211.5 mg/L, MgSO4.7H2O: 88.8 mg/L, NaHCO3: 46.7 mg/L, KCl: 4.2 mg/L
- Ca/Mg ratio: 4:1
- Culture medium different from test medium: yes (daphnids were cultured in Elendt M7 medium)
- Intervals of water quality measurement: pH and dissolved oxygen were measured at the beginning and at the end of the test, for all concentrations and the control. Temperature was measured continuously in a temperature control vessel, beginning at the start of the test.

OTHER TEST CONDITIONS
- Adjustment of pH: not necessary
- Photoperiod: daily photoperiod of 16 hours

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
Immobility (including mortality) and signs of disease or stress (e.g. discolouration, unusual behaviour such as surface trapping, etc.) after 24 and 48 hours of exposure.

RANGE-FINDING STUDY
- Test concentrations: 100, 10 and 1% of a supersaturated solution (SS) prepared at 100 mg/L
- Results used to determine the conditions for the definitive study: no significant immobility in 1.0 and 10% of the SS after 48 hours, 95% mortality was observed in the undiluted SS.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mobility

Remarks on result:

other:

Remarks:

supersaturated solution prepared at 100 mg/L

Key result

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

56 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mobility

Remarks on result:

other:

Remarks:

56% of a supersaturated solution (SS) prepared at 100 mg/L

Details on results:

DETAILS ON RESULTS
Behavioural abnormalities:
- Other biological observations: see attached document "S-930 - Number of Introduced Daphnids and Incidence of Immobility in the Final Test.pdf"
- Mortality of control: none
- Other adverse effects control: none
- Abnormal responses: none
All test solutions were clear and colorless at the end of the preparation procedure.

For details, see attached document "S-930 - Number of Introduced Daphnids and Incidence of Immobility in the Final Test.pdf"

Results with reference substance (positive control):

- Results with reference substance valid? yes
- 48-hour EC50: 0.59 mg/L with a 95% confidence interval between 0.53 and 0.72 mg/L (historical data of 48h EC50 are between 0.3 and 1.0 mg/L)

Reported statistics and error estimates:

The 24 and 48h-EC50-values could not be determined because the observed effects were below 50%. The NOELR and LOELR were determined directly from the raw data.

Validity criteria fulfilled:

yes

Remarks:

In the control, no daphnids have been immobilised or showed other sub-lethal effects; the dissolved oxygen concentration at the end of the test was > 3 mg/L in control and test vessels.

Description of key information

effect value for Daphnia magna, based on loading rates (OECD 202):

48-h EL50: > 100 mg/L mg/L (solubility in test water < 1 mg/L)

Additional information

The results indicate that the test material is not toxic to daphnia up to the limits of its solubility (< 1 mg/L in test water) and a NOEC and thus a PNEC cannot be determined.