O,O-diethyl hydrogen phosphorodithioate

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline compliant study, fulfilling the validity criteria determined by the guideline.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

3454-66-8

Cas Number:

3454-66-8

IUPAC Name:

3454-66-8

Constituent 2

Reference substance name:

Phosphorodithionic acid, O,O-diethyl ester, potassium salt

IUPAC Name:

Phosphorodithionic acid, O,O-diethyl ester, potassium salt

Details on test material:

- Name of test material (as cited in study report): EP-1 potassium salt
- Molecular formula (if other than submission substance): C4H10KO2PS2
- Molecular weight (if other than submission substance): 224.32 g/mol
- Physical state: white powder
- Analytical purity: 99.7% w/w
- Lot/batch No.: 343-BSe-66E
- Storage condition of test material: at -20°C

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
-Water solubility: 80 g/L
- log Pow: -0.46

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
The stock solution was prepared by dissolving 487 mg and 453 mg of EP-1 potassium salt in the test medium (natural seawater) by flushing the amount into a 500 mL volumetric flask and making up to volume with filtered clean seawater, followed by mixing this solution by magnetic stirring. After 2 hours, this solution was used for preparing a dilution series with the following final concentrations as used in the test: 100, 200, 500, 1000 and 1800 mg/L.

Test organisms

Test organisms (species):

Skeletonema costatum

Details on test organisms:

TEST ORGANISM
- Strain: Clone NIVA BAC 1

Study design

Test type:

not specified

Water media type:

saltwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

Not applicable

Test conditions

Hardness:

Not applicable

Test temperature:

18.8 +/- 0.2°C

pH:

8.1

Dissolved oxygen:

Not applicable

Salinity:

28%

Nominal and measured concentrations:

nominal: 0, 100, 200, 500, 1000 and 1800 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass flasks with total capacity of 250 mL
- Fill volume: 70 mL test solution consisting of algal growth medium, algae and test substance
- Initial cells density: 1200 cells/mL
- No. of vessels per concentration (replicates): 3

GROWTH MEDIUM
- prepared from natural seawater; heated to 73°C and filtered through Millipore filters (10, 5, 0.5 and 0.22 µm); nutrients and salts were added according to OECD 201.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: seawater

Reference substance (positive control):

yes

Remarks:

3,5-DCP

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

1 026 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

cell number

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 800 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

cell number

Effect concentrations 3

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

1 800 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

cell number

Effect concentrations 4

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

cell number

Results with reference substance (positive control):

The results of the reference substane 3,5-DCP with an EC50 value of 1.7 mg/L showed that the sensitivity of the algae was not significantly different from the results obtained in an international ring test (EC50r = 1.0 - 2.2 mg/L).

Reported statistics and error estimates:

Not applicable

Any other information on results incl. tables

The validation criteria of the test according to ISO 10253 are considered fulfilled:

- The cell density in the negative control (without test substance) increased by a factor of more than 16 during the test period.

- pH in the control flasks did not vary more than +/- 1 unit during the test.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The NOEC and LOEC for the growth rate of Skeletonema costatum after application of EP-1 potassium salt were 1000 mg/L and 1800 mg/L, respectively. The EC10 and EC50 values derived in the experiment were 1026 mg/L and > 1800 mg/L, respectively.

Executive summary:

The test substance EP-1 potassium salt was tested for inhibitory effects on the growth of the marine microalgae Skeletonema costatum according to OECD guideline 201 and ISO 10253.

The test was carried out in 250 mL flasks with approximately 70 mL of test solution per flask. The growth of the algae was measured as fluorescence every 24 hours during the test. The total exposure time was 72 hours.

Chemical analysis revealed that the actual concentration of the stock solution was 1850 mg/L, which is close to the nominal concentration of 1880 mg/L.

The results of the study expressed in nominal concentrations can be summarized as follows:

The NOEC and LOEC for the growth rate were 1000 mg/L and 1800 mg/L, respectively and the EC10 and EC50 values for the growth rate were 1026 mg/L and >1800 mg/L, respectively.